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  N9EWO Review :
 ICOM IC-R75 Communications Receiver

ICOM's "Triple Conversion" IC-R75 HF Communications Receiver. (N9EWO Photo)
Used samples commonly appear on the market as it was in production for over 15 years.

Icom's last "HF only" Communications Receiver. Many versions include the "Sync" circuit that is really worthless. Also to our ears the audio quality in AM mode is fair at best even with a external speaker in use (can be improved with "Kiwa Electronics" modifications, see text below). Later samples (US versions marked as the IC-R75-12 and IC-R75-22 on it's outer box sticker) no longer offered the "Sync" function. Once the audio issues are fixed (BOTH Kiwa audio mods), then is a decent tabletop HF receiver. Came onto the market in 1999, production ended in late 2015. (N9EWO photo)

Discontinued Receiver

Icom's IC-R75 tabletop HF communications receiver came onto the market back in 1999 and was taken out of production in late 2015. Frequency coverage is from 30 hz right to 60 MHz. This allows one to catch the 6 Meter amateur band as well. USA versions included a "Floor Brick" AC power supply. For many samples this will be a unregulated linear transformer, but in mid 2009 this was changed to a switching type supply (see below for more information on this subject).

Continued ICOM's trait of not so great audio continued, but it's not as bad as the old IC-R71 "Distortion Beast". It's a muffled sound with the IC-R75. This "cloudy audio" ill is detected more so in the AM mode "super-wide" 15 Khz bandwidth. One can improve on this with 2 separate internal audio modifications that can be done by
Kiwa Electronics in MN USA. However, from my own "before and after testing" this does NOT totally cure the problem either (when compared to the Kenwood R-1000's super good audio, which does much better in the 12+ KHz bandwidth even after the mods). Important : One should have BOTH Kiwa audio mods done to help the audio, but at LEAST the "High Fidelity Audio Filter Upgrade" one. I have tested this in 2 steps, including before and after digital recordings so I have experience with both of the Kiwa audio mods (see reviews below and to hear a MP3 file). The Sync detector is the other real stinker but Kiwa has a mild modification for that as well that "sort of helps" on this.

The set features "Twin PBT" (Pass Band Band Tuning) as used in many of Icom's Amateur Transceivers. The optional DSP is the same board that was used in other ICOM Amateur sets, it's using the old school AF type of DSP. Even in this price point Icom used a 1 hz synthesizer. So you can tune AND DISPLAY razor sharp.

Alas, the linear "transformer" version of the AD-55A floor brick power supply (USA versions) is unregulated and provides way too much voltage even fully loaded (which we measured at 17.65 volts which is way over specs.). So the set runs very warm to near HOT after awhile as the internal voltage regulator has to burn this excessive voltage off.

See our full review below which includes separate sections on the Kiwa Electronics (USA) audio modifications.

Dave N9EWO
© N9EWO, all rights reserved
Ver. 10.3

Sync detection removed with later production, "Icom IC-R75-02" (US version). "AD-55S-12 Switching" AC Power Supply For Later USA Samples.

1. Back on October 16, 2006 we seen the IC-R75 listed with a revised FCC OET, and wondering what was going on here ? It turns out that the stinky "Sync" was no more with new samples sold starting in early 2007 ? The stock of the Motorola MC13022 Sync IC (this is a AM stereo chip) finally ran out. This IC has not been made in years, and for Icom to keep the receiver in production at that time changes had to be made to this part of the circuit. The revised model is known as the IC-R75-12 (USA version, marked on the outer box sticker near the serial number). As we have made note here to this effect already, this is no real loss as the Sync was really worthless.

2. Switching" AC Adapter was included with later production of the Icom IC-R75 receiver (for USA samples). Icom obtained another update to the FCC OET (type acceptance) on July 28, 2009 for the IC-R75 receiver. As I compare the 2009 updated owners manual (as seen on this FCC link) to the older manuals, on the "supplied accessories" page it shows a different AC Adapter and added switching regulator information on the bottom of that page.
Samples that included the new switching AD-55S-12 AC power supply were marked as the "IC-R75-22" on it's serial-model number sticker (located on it's box).

With at least the "High Fidelity Audio Filter Upgrade" done by Kiwa Electronics (see review and audio file below)
, it can sound decent too with the right external speaker. It's not perfect either even after both of the audio mods, but AM mode audio is much improved (in wider bandwidths).

Dave N9EWO
© N9EWO, all rights reserved
Ver. 4.5


N9EWO Review : Icom IC-R75 Communications Receiver (as Stock).

Model : ICOM IC-R75
Country Of Manufacture : Japan (Osaka)
Serial Number (approx.) of Test Sample : 02 0360x

Test Antenna's :

RF Systems MLBA-MK2 long wire (55 ft length - 24 ft height at peak)
Comet H-722 HF Dipole (24 ft height peak - Straight Configuration)

PRO:
-  Triple Conversion design with dual filtering system plus are independent of mode.
-  Very good weak signal sensitivity (with pre-amp 2 on).
-  Excellent Dynamic Range, Image and spurious signal rejection.
-  Excellent Front End selectivity with 7 separate band filters (for HF).
-  Tunes and displays down to precise 1 hz steps.
-  Very good ergonomics.
- Twin PBT control works very well with SSB signals (see con).
- Good audio quality (SSB modes) with no strange noises or excessive hiss/distortion (see con).
- Clean “line output” that also has no excessive hiss.
- Fast-Slow AGC selector with off and RF gain control (see con).
- Optical tuning knob encoder with weighted knob that has a fairly good spin dimple to boot.
- Easy to read LCD readout with long lasting, evenly lit 24 LED's for back lighting.
- Nice tilt bail (see con).
- 101 memory channels.
- Extended tuning range to 60 MHz.

CON:
-  AM Wide bandwidths exhibit muffled audio (fixed with Kiwa Electronics modifications, see separate reviews on this page)
-  Keypad requires MHz entry.
-  Only "One" VFO available.
-  Sync mode has absolutely no merit (unacceptable).
-  On very weak AM signals with heavy fading tend to get washed out in AGC more than it should, so for the mediocre audio recovery in AM mode under these conditions (switching to manual ECSS and turning off the AGC helps improve this issue…see text).
- Twin PBT control does not work on AM signals.
- Strange RF/AGC control (for those that are not used to the Icom way of doing this).
- No schematic or block diagram included.
- Tilt bail has no protective “feet” for table surface.
- No tone control.
- Poor noise blanker.
- Only marginally useful UT-106 DSP option.
- Included Power Supply Issues (see text)
- Keyboard beep appears at line out jack.

BOTTOM LINE : The HF Receiver tabletop bargain for decent performance. It’s a no-brainer, a set that has good ergonomics (aside from the requiring MHz keypad entry), IF bandwidth filters that I feel that are very well chosen, tunes and displays 1 hz steps and SSB performance that are unmatched at this price point. A pity that the Sync detection is a TOTAL washout (not available in later production). Triple conversion with 3 filter selections for the AM mode (455 kHz filter). The Kiwa Electronics audio modifications are highly recommended (review on these separate below). Otherwise AM audio (more so in wide bandwidths) is on the muffled side.

More Than LW / MW / SW ..101 Memories

The ICOM IC-R75 covers a bit more than the normal SW fair. It starts out at the usual coverage “bottom end” for any Icom receiver, that is 30 kHz. But the top end is at 60 MHz. Most people who purchase this set will probably never use this added coverage. But it gives more “Bands For The Buck” which allows for listening up past the 6 meter amateur band. When this band does open up (which is not very often) it can make for exciting listening provided one has the proper antennas at hand.

We have 101 memory channels (99 regular and 2 scan edge memories which can double for regular ones), with one VFO. Knob tuning steps of 0.1, 1, 5, 6.25, 9, 10 12.5, 20, 25 and 100 kHz are available. The 5 kHz step works great for zipping up and down the SW broadcast bands.

4 different scan types and even a auto memory write scan. This will write a frequency to memory channels as it finds active signals.

A clock with on–off timer and even a 24-hour sleep timer are also found. However the clock cannot be viewed at the same time as frequency. It’s another button pushing affair to use the on board clock. Better to use an external clock and forget the internal unless one is to use the timers.

Operation modes and filter selection are independent of each other for proper operation in use within the HF bands (excellent).

Included owners manual does not include a block diagram or schematic of the set (you need the optional Service Manual to do that).
 
Front Panel Controls / Nice Tuning Knob / Frequency Entry / Construction

The R75 has a very easy to use layout with logical one touch buttons for keypad, mode and other functions. This might make you cheer for joy after using a AOR AR7030 for awhile. The keys are made up of a rubber like plastic, it’s unknown how these might breakdown in use? They are of a hard variety and have good tactile feedback.

When one is using the keyboard to enter frequencies, it must be done as MHz. That is the decimal point must be entered or you will get “nada” instead of tada. Same scheme that has been used with Icom over the years (even the wideband IC-R8600 receiver still does it this way, old habits never die). But really its the only operation bug-a-boo that I have with this set. But is still pretty silly for a 21st century receiver as KHz entry is the most logical way to accomplish this.

Receiver is housed in a very solid all metal cabinet, with the usual plastic bezel. A tilt bail is also provided that gives for excellent viewing angle, but lacks any protection to the table top (this was corrected with the IC-R8600). One that is handy enough might consider slipping some thicker “slit” rubber tubing over the bottom of the bail shaft to help prevent the digging of the it into the table and also to help the set from sliding around. It does have real “rear” rubber feet, which helps the slide factor.

Large main tuning knob has an above average good “smooth” feel. A resistance level slider can be found just below this knob to increase the drag for less touchy tuning. Icom chose to use a optical encoder behind this knob. It’s not quite as smooth as the JRC NRD-545 super set, but in this price range it is very welcomed. Properly weighted with the rubber track and finger spinner hole that actually turns with rotation is another real treat. However in practice this finger spinner does not turn that freely (at least when new). The knob encoder has no play or sloppy feeling, another real bonus.

Other knobs for Vol/RF Sql and for Twin PBT are a bit small for my liking (but OK). But at least these are not of the painted variety, so should not show wear with use.

Pleasant LCD Display / LED Back-lighting / Contrast / Digital Bar Meter

A very large easy to read back lit LCD display is provided. Adjustments for the display back-lighting is provided as well and is most needed. The back lighting is not using low tech light bulbs. It actually is made up of 24 Light Emitting Diodes (LED’s). Properly fed LED’s have a much longer service life than any light bulb arrangement. Especially if one keeps the display on the dimmer side using the provided dimmer adjustment, these LED’s will surely outlive the rest of the set. This was very good to see this and Icom did it right here. It is also very evenly lighted.

Contrast of the LCD is quite good, except if one reads at an angle from below and upward it will become less readable with lighter contrast. It shows just about every function and was well laid out to the authors eyes. It can also display alpha tags to name the memories. But again like the clock cannot be displayed with the frequency at the same time.

The S-Meter continues the trend that JRC started in the consumer table top market back in 1986 with the NRD-525. We have the Digital bar graph meter in the IC-R75. You can select if you wish the to have “peak hold” to work or not (will hold the peak reading for a second). It has many segments, but I would still prefer a good analog meter. But it gets the job done in any case.

Floor Wart Power Supply (2 different types included over it's life on the USA market) / Hum when using “Back Of the Set" Antenna’s (AD-55A/E) 

The ICOM IC-R75 has no internal power supply. Instead it uses an included dreaded (external) “Floor Brick” power supply. The original AD-55A (AD-55E in Europe) transformer linear supply is almost the size of a brick too, but seems to provide the needed current to operate the set.

A snafu if a local “back of the set wire” was used, hum was heard mixed on most signals. This is due to the fact that the power supply lacks the proper bypass capacitors across it’s power supply rectifier diodes. Connecting an external antenna using shielded coax or grounding the set cleared this “diode noise” problem up totally.

L
inear "transformer" version of the AD-55A floor brick power supply included with most USA versions is unregulated and provides way too much voltage even when fully loaded (tested at 17.65 volts which is WAY over specs.). So the set runs warm to near HOT as the internal voltage regulator has to burn this excessive voltage off. Have been reports over the years (IC-R75 "Yahoo Groups" for one) that have pointed to where this has contributed to failures where the receiver fails to power on in time.

Switching AD-55S AC Adapter was included with later production of the Icom IC-R75 receiver (at least with USA samples). Even being regulated and produces closer to the 15 volt rating, it's still allows the set to run warmer than it should (almost near HOT) as 15 volts is still a bit excessive operational voltage (in our view). Of course using ANY switching power supply with a HF receiver is NOT a good idea anyway, more so with any close / indoor antennas (good old self-inflicted noise).

I will NOT be held responsible for any info that is listed here
ALL DONE AT YOUR OWN RISK !

The best solution is to run operate the set with better external LINEAR TRANSFORMER power supply such as the ASTRON RS-7A, and turn it's output voltage down to 12.0~12.2 volts (measured as when loaded, the RS-7A has an internal trimmer in which to do that). Icom does use a bit un-standard size coaxial "donut" plug for DC input with the IC-R75 (3.0 mm ID x 6.3 mm OD size, positive tip) and are not easy to find. As usual, BE SURE and add a 2 ampere "Fast Blow" fuse in the positive side of the power line as well as using the proper gauge connecting cable (say 18 AWG).


See the top of this review page for more information on the included power supplies.


The Icom IC-R75 "Rear Panel" (N9EWO Photo)

Dual Filtering / Triple Conversion / Filters

Even at this price point we have a triple conversion scheme. Many sets at even double the price are using only dual conversion (not that triple conversion is not necessarily better than a dual conversion one for increased performance).

Filter scheme is another Icom tradition that you usually see only in their amateur radio HF transceivers. It uses a first IF of about 69.01 MHz (varies a bit with mode), the 2nd  is at about 9 Mhz and the 3rd is at 450~455 kHz.

User can select what filters are actually activated on which icon (sic) on the LCD. Stores these filter choices as well for each mode “set”. For example on SSB one can have a choice on the 9 MHz IF of either 2.4 kHz or 15 kHz (or pass). On the 450~455 kHz IF, It can also be set at 2.4 or 15 kHz (or pass).

With AM modes on the 9 MHz IF selections are : 2.4. or 15 kHz (or pass). The 450-455 KHz IF the options are Narrow: 2.4 or 15 khz  (or pass), Med : 2.4 or 15 kHz, Wide : 2.4 , 6.0 or 15 kHz. You have other selections for the CW/RTTY and FM modes. The chart that shows this in the manual I felt might buffalo most non-technical people (or who are just starting to use SW receivers). The manual overall is good, but the filter adjustment page was not very clear to me.

Icom offered many additional optional filters for SSB and CW modes that again all toggle from the filter menu.

All the filters performed well to my ears and to see 3 bandwidths offered that can be used in the AM mode was a huge plus. I was also very pleased to find that the IC-R75 is able to select a very wide filter (12~15 kHz ?) in the AM mode when conditions warrant. So many manufactures choose to restrict the widest filter to 6 kHz. This of course will really squash audio quality. Thank you Icom for adding this really wide selection. 

Front End Selectivity / Image Rejection / Other weird Noises / Dynamic Range

What weird signals! I was unable to find any strange out of place signals on the test sample. The IC-R75 uses 7 different Front End Pre-selector filters for the SW coverage (a few more exist for frequencies above 30 MHz). This was done right.

I would say top notch image rejection, among other similar traits here.

Was unable to hear any overloading at any time with all antennas used during the test period. It again was excellent.

Stability / Frequency Display

Stability was simply very good. One could improve on this with the optional CR-282 TXCO (not tested).

I found the test sample’s frequency only to be off at only 20 hz high with the test sample out of the box (after a good warm up). This is not a problem for me with a HF receiver in this price range.

Twin PBT… A Useful Tool

Another control that has appeared on Icom’s amateur transceivers over the years is now found on the IC-R75. Very useful on SSB modes. However It does not work on AM modes, a bit of a shame but not a drawback either.

Being the IC-R75 lacks any kind of a tone control (another downfall), the PBT controls can of course be used as a quasi tone control, especially in manual ECSS mode. Works well indeed.

“Sync Detection” (S-AM) a Total Disaster

Not sure what happened here but, the IC-R75’s sync mode, or as Icom has it marked on the display as S-AM, has no purpose. It’s simply is a total washout. Only does it not help clear up any interference as it’s not selectable sideband, and it seems to add more distortion on fades. Best to forget this even exists on this set. It’s one of the worse (if not the worse) “Sync” circuits that I have ever encountered. This was not offered in later production, see the top on this review page for additional on this.

Kiwa Electronics offers a modification to help make this feature useful, but alas is not much. Please see the separate Kiwa reviews below as we did test the sync modification (added module) plus 2 additional audio mods.

Sensitivity Equal To Other Good Sets / Audio Recovery So-So in AM mode

I hear the sensitivity about equal when compared to the JRC NRD-545 (when “PREAMP 2 is activated). Very good but not any better either. The JRC hears signals better as it’s Sync actually works and makes for pulling out audio out the weak signals less of a chore. If one does take the Icom into manual ECSS mode…it works much better, actually a much closer match as compared to the NRD-545 in auto ECSS mode.

During testing I found myself just leaving the set with PREAMP 2 on all the time. I did not hear any bad effects here at my listening post. This it totally the opposite when compared to the later Icom IC-7300 HF transceiver and it's 2 pre-amps (here I rarely needed them).

Normal Icom AGC characteristics, very weak signals using AM mode a bit washed out.

For the most part the set’s AGC seems to function more than adequately. But to my ears when listening to very weak signals in AM mode, I feel signals are being washed into the AGC floor more than they should. That is I have a hard time understanding voices. Turning off the AGC does not seem to help this condition. If the signals contains heavy fading which most weak ones will give, its even worse.

This is the exact same trait that plagued the IC-756 PRO II transceiver tests receiving in the AM mode. It might not be quite as bad as the 756 PRO II, but it’s a noticeable problem.

Perhaps if the IC-R75’s “Sync” worked properly, this might have been the golden combination, but it’s does not.

Now, If I switch over the “Manual ECSS” (USB or LSB) this AGC floor problem is not as much of an issue. And as it should, turning OFF the AGC off helps even more with manual ECSS where on AM mode, turning off the AGC really does nothing to help the recovery of weak audio.

When I owned a Icom IC-756 PRO II transceiver, even with it’s AGC off and in ECSS mode…it did not help at all with weak signals. So much a downer like it never sounded like I switched off the AGC, so it’s a major improvement over this experience.

SSB Audio Quality Good with external speaker, with a touch of above average bass / AM Mode Audio Muffled (fixable).

The IC-R75 has pleasant SSB mode audio. I do detect a touch of out of the ordinary distortion in the AM mode but is not excessive. The internal speaker while being of a very desirable front facing variety, has limited use as it’s very small speaker will only give. As with most table top sets a better external one is a requirement.

One might wish to choose one what will not add to the sets tendency to produce a touch of above average bass. This “bit of bass” appears at the line output as well, so is not the sets audio amplifier that is creating this. AM mode audio is on the muffled side. This is more noticeable in the wider bandwidths. If one does at least the Kiwa Electronics "Hi-Fi Audio Modification" (see review below), this improves the AM Wide 12~15 Khz bandwidth audio by leaps and bounds.

Record “Line Out” at a good level / “Beep” emits from the output

Record “Line Out” on the rear panel (1/8 inch phone jack) is at a good level, also is clean without any excessive hiss. The elder Icom IC-R9000 had low audio from it’s “line-record outputs” (as tested) and needed to be boosted it was that anemic. Unlike the JRC NRD-545 but just like the IC-R9000, the keyboard beep also appears at this output, so it will be heard on the device connected to it. This can be turned off in the set mode.

Noise Reduction Tools / Noise Blanker / DSP Option Comments

The noise blanker function on the tested sample here at my location was pretty much a disappointment. It really did nothing to control my type of noises around my house. It also lacks any level adjustment. So it was a unusable button for me.

Optional UT-106 DSP option adds a ANF “Automatic Notch Filter” and a NR “Noise Reduction” function. These are working in the AF stage of the radio.

ANF mode was of use on some (but not all) heterodynes. This is best used with the narrower filters (6 kHz on AM , 2.4 kHz on SSB). One of those things that you try it and if it works it works. So a 50-50 type of thing.

NR operating mode has an level adjustment. I found the setting of 4 worked best without killing the audio too much. It does degrade the audio of the signal, but if the signal is full of static say from a motorized appliance, this is certainly more useful than the Noise Blanker.

Most samples of the IC-R75 included the UT-106 as a free perk. You will find more used samples with this than not.

Decent Digital HF TableTop / Icom's Last "HF Only" Communications Receiver

The IC-R75 is a respectable digital tabletop communications receiver. Decent overall performance / ergonomics and very good SSB audio out of the box. Caveats are it's greatly muffled "AM Mode" audio quality, which can be fixed for the most part with the Kiwa audio modifications (as we cover below). Also be sure and operate it with a better power supply then what is included with it (at least if you praise it). 

Icom's IC-R75 had a good run on the market (1999 to late 2015), They decided not to replace the receiver with a more up to date "HF only" model. The MUCH more modern and advanced IC-R8600 "Wide Band" tabletop receiver (click here for our review)covers the spectrum (wideband coverage) with SDR technology, digital voice decode and excellent Spectrum Scope. But is of course much more expensive. We feel it's the BEST HF receiver Icom has made to date, wideband or not (and we have tested them all). But if you just can't afford the latest and greatest, a nice "properly working" used IC-R75 is a worthy set. However for any serious broadcast listening the Kiwa Audio modifications are again near required in our view.


Dave N9EWO
© N9EWO, all rights reserved
ver 2.1

Discontinued Receiver

ICOM IC-R75 Communications Receiver
 with Kiwa Synchronous Detector and Audio Upgrades


Please see the Kiwa Electronics web site located here for current status and prices.

PRO :
- Slight improvement of audio response (a bit more crisp).
- Very slight improvement of “Sync” lock (see con).
- Excellent quality of work / service and turn around time.

CON :
- Only slight improvements noted after these 2 modifications.
- The Synchronous Detector (S-AM) now “screeches or warbles” (dropping out of lock) on really deep fades ,slow AGC sometimes helps greatly.
- Slightly added “Audio Amp hiss” on narrow bandwidths.
- Strange ECSS (selectable sideband) operation.
- Distortion level unaffected (no improvement).
- No (easy) way to easily undo these modifications.

BOTTOM LINE : In a nut shell….forget these, unless one really needs the “very slight” increase in performance. After listening to the digital recordings that I made before the set was sent to Kiwa and after, it comes to my ears that either of these modifications are very minor improvements
(unless one is also planning on doing the "Hi-Fi" mod as well then maybe do these as well, see below).

Fast Turnaround Time

First let me say that I was very impressed with Kiwa’s fast service. The set was sent in on a Friday and I had it back in my hands on the next Thursday. Less than a week, now that’s impressive. (Kasson MN USA).

The quality of the work appears to be very good, but the silicone goo used (as explained below) is a bit of a questionable mark?

Audio Upgrade

“Audio Upgrade”
“Key components to the audio power amplifier are replaced to enhance clarity and definition.”

This audio modification seems to be value changes of 3 capacitors near the audio amplifier IC section (that I can tell, see attached picture). One being a surface mounted type that is changed to another standard type (red in color) and the 2 others are of a electrolytic type.

A bit of silicone goo is dabbed around these after installation to help support these “caps” as they are mounted a bit away from their normal spot.

Being in widest bandwidth in the AM mode, I can tell a “slight” increase in high frequency response. That is it’s a bit crisper. However this only a very minor change and for many with less than perfect hearing might be to wonder if there is any difference at all ?

I heard this slight improvement while listening to a “Good” AM broadcast station being in the widest bandwidth setting. The downside is I noticed a slight increase in the noise floor (e.g.: Manual ECSS in narrow bandwidth) with no improvement at all with the audio in narrowest bandwidth.

Synchronous Detector Upgrade

“Kiwa provides two major upgrades to the Synchronous Detector. Together they provide enhanced performance where the PLL stays "locked" under the most difficult signal conditions.The first upgrade is best described as a "dual speed control voltage". The control voltage for the PLL filter is tuned within an optimum window that is determined by signal conditions.The response is slow to maintain a "centered" condition. A second circuit provides the control accuracy to react to fast flutter fading and noisy conditions. These two circuits provide a dual speed control for the PLL.”

“The second major upgrade is to the Synchronous AM AGC. The dual speed technique is used again to first center the AGC but still allow for quick short changes in AGC characteristics as required by signal conditions. All components are encapsulated in a plastic module and mounted to a side chassis wall.”

The added “Synchronous Detector Upgrade” circuit appears to be all housed in a small “potted” cube that is affixed to the back microprocessor shield (see picture below), 3 wires protrude from the module. It is held in place with adhesive “scotch-lock ®” strips, so one could remove the “cube” without peeling away a strip of nasty adhesive.

However actually removing this modification would still not be an easy task as two of the pins on the “sync” chip of the set are lifted up and wired to this added module. Simply no easy way to undo it. So one is pretty much stuck with it after it’s done. Another dab of silicone goo can be seen on top of the original sync chip in the set to support the wires that need to be attached.

Does this module really help in “sync-AM” performance? It does, but not to any eye shattering improvement.

It does help the lock of the circuit over a stock unit “slightly” but again this is still not the great either. It continues to drop out of lock and now when it does “unlock” on these certain stations with really deep fades, a nasty warble or screeching sound is now heard in its speaker. We did not notice this before the modification. Before it was just dropping out of lock, now it drops out of lock and you get a nasty sound with it.

Using slow AGC is actually necessary on some signals as it really goes into “hyper-warble” if it’s not. It depends on the station being received. But its not a cure all either as many times one is forced to turn it off or use manual ECSS.

S-AM is only useful with the Narrow bandwidth (other 2 forget it). To make that even more interesting, in LSB (both PBT knobs CCW) It works ok (aside from the unlocking problem). However when both PBT are clockwise (USB), audio is a bit more muffled the level goes slightly lower, weird indeed.

The distortion factor to my ears has not changed, the sync still disappoints here.

I feel that both of these modifications are of limited use and one should not be expecting sterling performance from its sync even after the trip back from Minnesota. It’s simply not to be. Again however, if one is going to try the MUCH more useful "Hi-Fi Audio Upgrade" modification as covered below, then a good idea to get the "Audio Upgrade" done as well at the same time.

Dave N9EWO
© N9EWO, all rights reserved
ver 1.4
I will NOT be held responsible for any info that is listed here
ALL DONE AT YOUR OWN RISK !

Kiwa Electronics ICOM IC-R75 Audio Modifications (N9EWO Photo)

Kiwa Electronics ICOM IC-R75 "Hi-Fi" Audio Upgrade (5.3 kHz)

(IMPORTANT NOTE : This modification is based having the first Kiwa audio modification (capacitors) done as well above, and the text below reflects this.)

Please see the Kiwa Electronics web site located here for current status and prices.

PRO :
- This useful modification clearly adds much increased AM mode audio fidelity using the “Normal” and “Wide” bandwidth positions.
- Excellent quality of work / service and turn around time.
- The “surface mounted resistors” were not just “jumped” as with the original “Yahoo Groups” modification (with the test sample as sent to Kiwa). 4 SMD devices are physically removed and replaced with the required new values (see con).

CON :
- With certain external speakers and devices connected to the “line output” added distortion was heard with some signals in SSB or manual ECSS modes (see text).
- Even with the 4 SMD resistors removed, the replacement values are using the standard 1/4-watt variety soldered in the SMD spots. No way to easily undo this or any of the Kiwa’s modifications.

BOTTOM LINE : A most worthy (both?) audio modification. If the situation stands where an owner is not happy with the muffled sound of his or her Icom IC-R75, this is the cure as it brings in more high audio frequencies along with better capture of spoken works. The minor downside is that with some signals in SSB or manual ECSS modes, mild distortion can appear with certain speakers or the line output, but not always (see text).

Be sure and listen to the "Before and After" MP3 audio file located at the bottom of this review.

Still Excellent Fast Turnaround Time

As we have experienced before, Kiwa’s fast service was a pleasant experence. Took 16 days from the day it was sent until it returned (Kasson MN), this includes the transit time.

The quality of the work also continues to be good, but the silicone stuff used in a loose fashion with the other 2 modifications (as explained below) is still a part of it that seems not to be of the same professional level in our view (see photo above).

Audio Upgrade: Take 2

Kiwa Electronics has taken on the duty of a second audio modification first learned via the Yahoo Groups for the IC-R75 via the Internet (developed by Dr. Phil).

This change involves adding 4 filter resistors across existing surface mounted ones near IC-1201. It involves changing the values to some very micro small surface mounted circuitry. Very few people (if any) will take on project like this. For even seasoned electronic “tech types” this could be an almost impossible feat as these parts are extremely tiny.

These added resistors improve the IC-R75’s high frequency response on a filter just prior to the line out audio jack. So the output of the “line out” is also affected.

Taken from Kiwa Electronics web site :

“High Fidelity Audio Filter Upgrade”
"The R75 has an inline audio filter that precedes the audio power amplifier. The audio filter comes stock with a bandwidth of 3 kHz. The High Fidelity Audio Filter Upgrade extends the audio bandwidth to 4.3 kHz. This upgrade is similar to dr. phil's upgrade as presented on the R75 Yahoo Group. (Kiwa would like to give credit and thanks to dr. phil and Ken for coming up with this excellent upgrade) The difference between dr. phil's upgrade and Kiwa's is that we set the audio bandwidth to 4.3 kHz while dr. phil extends the audio bandwidth to 5.5 kHz. We adopted the 4.3 kHz because we felt it was more in line with the filters offered and to provide some attenuation to 5 kHz hetrodynes which can be a problem on the SW bands (due to the 5 kHz channel spacing between stations)"

Kiwa Electronics will install these resistors in your IC-R75 for improvement with very little effort on the owner’s part.

Also the 4 new value resistors are not just paralleled across the existing ones as with the documented “Yahoo Groups” modification indicates. Kiwa actually removes the old SMD resistors and replaces with the new lower (corrected) values. This is a much better way to go about this and they should be complimented on this very important point with this modification.

Kiwa feels that just about any heat can easily damage the existing SMD resistors on the board while trying to piggyback on the new “larger” non-SMD ones. This makes perfect sense indeed when working with any SMD devices. General components in the IC-R75 are about as tiny as you can get too.

However, Kiwa did not install SMD devices when replacing these resistor values in the test sample. They used 4 standard 1/4-watt versions that were vertically mounted and then smeared with a dab of silicone goo after soldered in place (see photo above). It would have been even a better job if the replacement values were also of the same SMD type.

A Choice of Audio Bandwidths?

As indicated above Kiwa will install the required resistors to give this improved 4.3 kHz bandwidth.

When our sample was sent to be fitted with this “Hi-Fi Audio Upgrade” we asked if the 5.3 kHz could be installed anyway. The answer was yes (for the same cost), so we sprung with the wider 5.3 kHz version and is what was used in testing here within this report and is what the audio file contains (see file link at bottom of this section).

It should be noted that if one desires this wider 5.3 kHz filter setting, one would need to make a special request enclosed with the receiver. This is not an openly advertised offer, and the owner will end up with the untested narrower 4.3 kHz version (at least at time of writing). PLEASE NOTE : This wider filter may no longer be available ?

(Note: On the invoice included with the returned sample, the upgrade was marked with a 5.3 kHz rating and not 5.5. So perhaps as close as they could get ?)  
  
Does it really help the Audio? / Higher distortion noted in SSB-manual ECSS modes.

This is a modification that is most worthy for general short-wave and MW listening in the AM mode (or AM-S). It really helps reduce the IC-R75’s audio to contain excessive bass or muffled sounding.

One will leap for joy when listening to any broadcast in the AM or AM-S modes, and using either the “Wide” or “Standard” bandwidth settings. It will be more noticeable when the “wide” bandwidth position is used.

It does not change the “narrow” audio bandwidth response in any mode, and by rights it should not.

The only (so be it minor) downside to this modification is that with some external speakers or certain “line output” connected devices, an amount of “high end frequency” distortion can be heard in SSB modes (or AM signals tuned using the manual ECSS method). This was not always apparent and may not be heard depending on the signal being received and what the “Line Output” is connected to (say another amplifier and speakers). It already had the first capacitor “Audio Upgrade” installed prior.

This distortion was almost not detectable using the sets internal very small speaker or headphones. With external speakers that have a bit higher frequency response and with the line output (again dependent on the device connected to this output), this can be a detectable issue.

What ones uses the line output for (say the external amplifier and the speakers used on that system) will be a factor here. 

Fiddling with the AGC setting proved to be unsuccessful in taming this distortion. There was no noticeable hiss added either from the speaker/headphone or line outputs in any mode. The DSP option operated normally with no apparent drawbacks after the modification.

[The standard untested 4.3 kHz version of this modification may be more desirable as it should decrease the distortion trait? By how much is unknown?]

If one goes for the first “Audio Upgrade” as well as the “Hi-Fi Audio Upgrade” and the “Synchronous Detection” modification all at the same time, this of course would save on shipping charges vs sending it back a number of times.

A Warning before You Take the Plunge !

It must be noted that any of these changes / modifications are irreversible (well at least not easy).

Dave N9EWO
© N9EWO, all rights reserved
ver 1.3

I will NOT be held responsible for any info that is listed here
ALL DONE AT YOUR OWN RISK !
N9EWO MP3 "Off Air" Audio File :
Icom IC-R75 BEFORE and AFTER Kiwa Electronics "Audio Upgrade -"Hi-Fi Audio Upgrade" Modifications.
 Using same "Radio Canada International" transmitter/frequency/time. Wide AM bandwidth (12~15 kHz) / identical settings.


ICOM IC-R75 comments from others
(Please Note : These are dated from around 2000 or so)


Mike Moore from Canada has made a purchase of a ICOM IC-R75 than had it modified with the latest Kiwa Modifications. He notices distinct improvements and here are his initial impressions (in our testing was a bit different). Thanks Mike for the comments.

"The AGC fix and perhaps to some extent, the audio mod, really removes the distortion that, previously, was particularly noticeable in the AM mode.  Now the audio is *extremely* clear and isn't easily affected by fading signals as it was before themod.  This modification is so good that the sync mod then becomes allot less important.  (I'm unsure as to how much is attributable to the AGC mod and how much is attributable to the audio mod.)  I tried feeding the audio into an Optimus PRO-X44AV speaker.  The audio was absolutely fabulous (although only average dynamic range). The sound was full and had a good bass.  Before the mods, with the external speaker connected, the AM distortion was so noticeable as to make listening with an external speaker unpleasant.  Now, it is very pleasant."

"The sync detector now works, ie. it maintains lock.  It whistles when gaining lock and whistles when it loses lock.  While testing it on a *very weak* station, it kept whistling/howling (before the mod, it seemed to make no attempt to gain lock).  With the dramatic improvement to the straight AM, it's now somewhat more difficult to find signals (with rapid fades) that would easily demonstrate the difference between the sync AM and straight AM.  Nonetheless, in the sync AM mode, audio and especially music appeared to suffer less from fading."

"The addition of the 3.8 kHz filter is just what the doctor ordered.  This is a perfect width for narrow AM/S-AM.  I tried it on Radio Havana, which had one sideband being interfered with. With sync AM, the 3.8 kHz filter and the inner PBT control turned to one side, the signal came in clear and sounded beautiful.  I had been considering buying another 3.3 kHz filter (many months ago, I had taken the one I had out of the R75 and put into the AR7030+) but with the 3.8 kHz filter installed by Kiwa, I have since changed my mind." 

"Also, the NR now seems to work better.  On this point, I'm not really sure if this is just subjective on my part or not.  Before the mods, the NR seemed to reduce signal and noise in equal proportions, rendering it rather useless.  Now it doesn't seem to attenuate the signal as much (or it seems to reduce the noise more) as it did before - actually making it useful. "

"Cheers! Michael Moore"


A few comments from Dan Blackburn on the IC-R75. I feel that IF a "Internal Power" supply is built correctly, no excessive heat or a cheap poor "buzzy" transformers...etc...it's better inside a radio. I hate Wall-Floor Warts !!!! The internal power supply in the JRC NRD-545 is a very nice one (not with later samples it appears), matched to the set perfectly (current vs heat) and is quiet as a mouse.

"I agree with many of the comments in the postings that have appeared so far, but I have a few things to add that I have found, from having owned two of these excellent receivers so far. First of all, I do not regard the receiver's external "brick" power supply to be undesirable. I have read several reviews and some of the comments in the postings on this site, which make mention of this." To me, an external power supply is VERY desirable for two major reasons: 1) It takes one of the main heat-generating components in any piece of electronic equipment, and moves it well-away from the sensitive circuitry inside the cabinet. This also helps remove potential hum and magnetic fields from the immediate vicinity of the receiver circuitry. 2) In the event of a power supply failure, it is only necessary to service the "brick" itself, rather than forfeiting use of the entire receiver during repairs."

"It should be noted that the external supply would likely be less failure-prone to begin with, as long as it is in a properly-ventilated location."

"Another observation I have made with regard to the R75's sync-AM function, is that it works MUCH better with signals which are lowered by the RF gain control. I have found that the sync circuit seems to be effective only on signals that "peak" below S10 on my bar-graph meter scale. In other words, by using the RF gain to suppress the signal level so that it only drives the meter to around S-7 or so, THEN engaging the Sync feature, the results are noticeably improved. Of course, the volume control must be appropriately increased due to the reduced RF signal, in order to maintain adequate audio levels, but this is a minor inconvenience. I have noticed that when the "S" character on the display is blinking, the sync detector is working and effective under the above conditions. When it is not blinking, the sync is not active and I further reduce the RF gain until it blinks on all but the received signal's peaks."

"I have also found that using Icom FL-257 and FL-223 filters, which produce 3.3 KHz and 1.9 KHz I-F passbands respectively, yield very good results and give the most available flexibility when selecting combinations for the many operating modes. For example, I have selected AM-mode filtering choices of 15/6 (wide), 15/3.3 (normal) and 2.4/2.4 (narrow) for most SWL activities."

"Finally, I have also found the R75's internal speaker to be somewhat less than adequate, so I use mine with the excellent Drake MS-8 external speaker unit. I have found the MS-8 just right for my listening preferences, and the speaker looks GREAT alongside the R75 with the receiver's tilt bail extended. I would recommend to anyone wanting to improve their R75's audio to give the Drake MS-8 a try."

"All in all, even with the cost of the added filters and MS-8 speaker, I believe the R75 to be a superior receiver, preferable in many ways to the more expensive Drake R8B, and with better coverage and cosmetics. Having owned two Drake receivers previously, as well as two Kenwoods and a Yaesu, I must say that the Icom R75 remains my hands-down favorite of them all."


A short comment from Bjorn Danielsson, Sweden on the IC-R75 .

"I have one since 1 week. And I am very satisfied with it so far.Yes it has 99 mem + 2 memories for scan edge. Is not 99 enough? I think it will be nice for me. Yes it can scan between 2 freqs and memory scan and on selected memories too like the R72 did. I can't compare it to other radios execpt for my old Icom R72. And the R75 is much better than the R72. Better sound quality, almost noting background noise on the audio. The R72 had a lot of noise. The squelch is selectable between squelch and RF-gain or both at the same time. But I have RF-gain at max and only squelch on the squelch !! :-) If you buy one don't forget to buy the DSP at the same time. It has Noise reduction and auto notch. I don't know why they have it as option, it should have been in it at first."

Bjorn Danielsson, Sweden


Johan L. in Sweden with his promised comments on his new IC-R75 . Well it looks like the audio and Sync circuit both.."Stink"..oh well so much for wishful thinking. You can have BOTH of the Kiwa audio mods done to at least improve the IC-R75's audio. A Big "Thank You" Johan for the input.......Dave N9EWO

The following are my first impressions and comments on the R75 after about 10 hours of usage, including some comparisons with my other units, the AOR AR7030 (standard w NB/notch) and the Icom R71(w/o PLAM). The review is based on PURE LISTENING (BC-stations, mostly AM) and not any scientific A/B testing. The R75 is equipped with the optional DSP and a optional 1.9kc filter in 2nd IF. The antenna is an 8 m(27ft) random wire with coax-feed and balun. For specifications and technical details, please refer to the Icom US website (link below..) or other sources.

First look:
The R75 is small and light. The look and styling of the exterior is very nice although it doesn't have the robustness of the 7030. The buttons are the "rubber-type", but feels distinct and has a good "feedback". The main dial is ok, but the R71's big "free-wheel" is still superior. Also the solid metal knob of the 7030 has a better feeling. The other two knobs are quite small and I did have some minor difficulties to operate them (big fingers?).

{Good to hear that. I wish that AOR would have used optical encoders with the 2 smaller knobs. The AR7030's larger tuning knob is sort of like grabbing a greasy door knob....Dave N9EWO}

On the rear you will find the ordinary connectors for antennas, PC, recorder, speaker etc. "Why didn't Icom label them?" I asked myself, until I took a close look on the serial number label! The layout is shown there! The R75 has a traditional front panel with the "one control=one function" concept, compared to the 7030 which uses very few controls and a complex menu-system with lots of up and down toggling. The similarity to the "older brother" R71 is obvious in some cases and if you're a R71 user, the step to the R75 is a short step.

The manual for the R75 is ok (but far from the excellent 7030 manual).Schematic is not included (not even a block diagram).{that stinks ...Dave N9EWO}

Usage:
The first thing that 'hits' you at power up, is the display. Large, clear and with a nice background illumination. All the settings of the receiver are shown on the display. Icom calls it a "function display" and that's what it is! I especially enjoyed the S-meter with its 'peak hold'. R75 really wins here. The method of selecting bandwidth seems to be taken directly from the R71. Each mode has three bandwidhts; wide, normal and narrow. Contrary to the R71, R75 gives you the possibility to combine the filters (15kc, 2.4kc, Spare in 2nd IF and 15kc, 6kc, 2.4kc, Spare in 3rd IF) for each bandwidth and mode. Eg for AM you could set 15kc+6kc, 15kc+2.4kc and 2.4kc+2.4kc for wide, normal and narrow respectively. The filter setup is very versatile and installing optional filters are easy. But, even this, I might still prefer the 7030 with its (up to) six filters and the excellent calibration feature. I lack a wider filter in either IF (2.8-3.3). The difference is very small, but points goes to AOR.

What about the twin-pbt? Again an heritage from the R71. The difference is that R75 uses two controls (a concentric knob) for moving lower and upper portion of the passband. Turning both controls together moves the entire passband. Works fine and it's much better than the R71 PBT. The 7030 uses one control and most importantly, shows the passband offset on the display. You see what you're doing (aka WYSIWYG!).

Entering frequency with the keypad works fine, but Icom should have included a kHz button as well. To enter for example 15565 kHz, you have to punch 1 5 5 6 5 0 0 ENT or 1 5 . 5 6 5 ENT. Another ex: 1100 kHz would be 1 1 0 0 0 0 ENT or 1 . 1 ENT. Other settings (and there are a lot), such as tuning steps, beep level, cw pitch, dimmer etc, are done in a setup menu. Very user-friendly and easy to use!

The performance:
Audio: The R75 has a SMALL front mounted speaker (Icom US webpage calls it large!). The audio output and fidelity are ok and with headphones it's even better. I've not tested any external speaker. In general the audio is clearly better than the R71 (could it be worse?) but still not better than the 7030 (could it be better?). Distortion shows up when using very narrow filters in AM, but that's logical and and could be remedied with the pbt. One way of getting nice audio is to use synchronous AM. Turning this on, the R75 will disappoint you! Honestly, I CANNOT hear ANY difference or improvement AT ALL! In fact, under certain circumstances, the s-AM will instead momentarily distort the audio! Very strange! Do I use it the wrong way or?...I suspect that Icom employs "carrier reconstruction" rather that "carrier replacement" for the R75 s-AM solution. The s-AM on the 7030 is superior and more versatile by all measures (even taking the disturbing low level heterodyne in account) The attack- and decay time for AGC fast and slow seems to be right and I'm satisfied with them. 

The optional DSP has two functions; noise reduction and automatic notch. The notch isn't operational in AM according to the manual, but that's not 100% true! Certain het's are reduced completely, others not. It seems to be some limitations within the passband (perhaps due to the notch being optimizedfor SSB bandwidths, not AM at 6kc). Well, it works to some degree. Compared to my MFJ-784B DSP, the MFJ is of course better and more aggressive in hunting and eliminating het's. The noise reduction works very well, also compared with the MFJ. The levelis variable between 1 to 15 (dB?) and at 5 the reduction is sufficient. As in any DSP, you will get 'echoing' or 'hollowness', when you increase the reduction level to maximum.

I would rate the R75 sensitivity as good and high enough for serious DX-ing. There are two preamps, +10db and +16dB, that works more and less over the entire spectrum (+16dB mainly used for 20+ MHz). Judging from S-meter readings and assuming that both S-meters are correctly calibrated (YES I know, this is not the right way) the R75 with preamp 1 equals 7030 w/o preamp on shortwave. With preamp 2, the R75 exceeds the 7030 with preamp. On mediumwave, the 7030 is better overall.

At a glance review, 1-5 (bad-excellent):
Price/performance: 5
Design: 5
Controls: 4
User friendliness: 5
Sensitivity: 4
Features: 4
Specific functions/features:
Filters: 3-4
Sync-AM: 2
DSP: 4
Setup menus: 5

Johan L, Sweden


Comments from James in Taiwan, edited from the "Newsgroups" .

I just got an IC-R75 after reading some reports both pro and con about the receiver. After using the receiver I found out that most of the cons were over rated. When using this radio keep in mind the price it cost. An IC-R75 IS NOT an IC-R9000 or any other US$5,000+ radio. My IC-R75 is replacing my IC-R71A. The R75 is FAR BETTER that my R71A in all functions.

The size of the R75 is just right as it can be used as a portable receiver in a car without making any big changes. ICOM has choose to use hard rubber for the buttons and tuning dials. Some people on the net feel the hard rubber will get eaten away over time. I think there is some truth to this but under extreme temperature conditions. The R75 is very light (My R71A was a ton!).

I must tell you that I put the DSP option in the radio and it works very well. The key to listen on the R75 is not to set the NR (noise reduction) level too high. If the NR is set too high you will get distortion at voice freqs. It a few cases I was able to masking / cover a voice completely by setting the NR very high. It's just a good ideal to set the NR to the maximum noise reduction level and not above.

The NB (Noise Blanker) is of great help. In some cases it kills more noise than my IC-R8500 with a DSP 599zx! I live almost under power lines and I night I get very bad bus noise fro the relay stations. With the DSP option the NB works very well (The NB doesn't work in FM mode).

I found the two level preamp VERY usefull in low signal conditions. Here in Asia we have to fight with noise a lot more that US or Europe based monitoring sites. In one case I was able to pull out a very low powered Mongolian station out between a radio station in Shanghai and Helongjiang in Northern China! I use the NR and ANF (Automatic Notch Filter) to peek the voice level of the announcer along with the TWIN PBT (Passband Tuning Controls) to adjust the level of IF to give me the maximum audio level ( this TWIN PBT wasn't a great help in AM mode but it did help!).

The memory bank space on the R75 is just too small. I don't know what came across the folks at ICOM by putting in ONLY 100 slots for programming. This is a major drawback. Because of the low memory banks I've started to use a PC control software to do large band scans. ICOM messed up here big time!

I found the scanning rate as fast as my R8500 and R7100 and the hit rate just as good.

The CW audio pitch adjustment also works well and saves me time when decoding via my external noise filter (Timewave DSP-599zx) The RTTY reverse mode helps me a bit when I screw up the MARK and SPACE signals. Also being able to select the RTTY shift helps when tunning a known RTTY signal.


Comments below from Gert Nilsson from Sweden on his IC-R75 . Thanks Gert for the input.

Some weeks ago I bought an IC-R75 with the 2.8 and 3.3 kHz filters and the DSP. Price around 9000 SKr = 1000$. We are some guys in �rnsk�ldsvik using 6 very long beverage antennas at a very quiet QTH. My friends have NRD 515, AOR7030+ and NRD525 receivers and I have made some tests. COMPARISON between R71E and R75 R71 with PLAM, 1024 memory board and some extra filters, attenuator below 1.6 MHz removed.R75 with DSP, 2.8 kHz filter in 9 MHz IF, 3.3 kHz filter in 455 kHz IF, AM band attenuator shorted out.These two receivers are rather similar, if you are used to the R75 you will enjoy tuning the R75. If you do not like the menus/remote control of the AOR AR7030+ the R75 is a receiver for you.

Sensitivity:My R71 is as sensitive as the AR7030, NRD515 and NRD 525. The R75 is even more sensitive. I have tried stations down in the noise and you definitely here them first on the R75. It has 2 different preamplifiers: Preamplifier 1 uses 2 JFET in parallel in a grounded gate configuration and I still have to se it crossmodulate. Preamplifier 2 can be used on all bands but it is intended for low noise operation above 20 MHz. It is an broadband IC amplifier with almost 20 dB amplification and very low noise, but it can not be used on crowded bands like the AM band during evening and night hours. It is perfect in a low signal environment. The specs for the R75 says 5.6 uV for AM below 1.6 MHz. With the attenuator removed it is very hot down to the lower frequency limit. ICOM has made a CP = Connection Point on the main board. If you short this connection point the attenuator is removed.The R75 has very quiet AF amplifiers, no broadband hiss like the NRDs which make readability of weak signals better.

Selectivity:The R75 has 15 kHz filter in the 9 MHz IF ahead of the Noise gate, then follows the other 9 MHz filters, 2.4 kHz and one optional. Third IF has 15 kHz and 6 kHz filters with 450 kHz center frequency (very cheap Murata filters) and a 455 kHz Murata CFJ455K5 2.4 kHz in other receivers but just 2.1 kHz in the R75. Any mode can use 3 different settings: narrow, normal and wide and you can choose yourself. The only limitations are that you can not use the 455 kHz filters in the S-AM (more about that later). Selectivity is very good. My 3.3 kHz filter has very steep shirts.

Passband tuning:The PBT of the R71 adjusts the width of the filters, if you do not have a wide extra filter in the 9MHz IF or bypass these filters. The R75 has twin PBT with 2 concentric knobs. If you turn both the same amount in the same direction you just move the passband, like the Drake receivers or the 7030. You can move it +/- 1.29 kHz in 15 Hz steps. If you turn one of the knobs or turn the knobs in different directions you can tailor the bandwidth and move the position of the passband simultaneously. With the 2.8 + 3.3 kHz any bandwidth between 1.5 and 2.8 kHz is possible. This is similar to the NRD535. I think the PBT works great. It works best with the optional 455 kHz filters.

Frequency control:The R71 has 10 Hz, 50 Hz (when tuning fast), 1 kHz and 1 MHz steps. The R75 has fine tuning of 1 or 10 Hz, coarse tuning selectable 0.1, 1 , 5, 6.25, 9, 10 12.5, 20, 25 and 100 kHz and band tuning in 1 MHz steps. You can have different steps in all modes. Tuning accuracy:The R71 tunes in 10 Hz steps and a has 10 Hz accuracy if you have PLAM and learn to count the marks on the tuning control. The R75 tunes and shows 1 Hz. The only indication of correct tuning is by ear so I would say 10 Hz is a realistic accuracy. My R75 shows the correct frequency at 500 kHz but is 15 Hz high at 30 MHz. I have not tried to correct this.

Stability:The R71 drifts about 60-70 Hz from turn on. The R75 drift is within 10 Hz.AM/S-AM:Of course much better audio in the R75, but I can't see any major difference between AM and S-AM. Icom uses a Stereo IC to restore the carrier. Not close to PLAM. In fact the R75 sounds so good in USB/LSB I always receive AM stations in the SSB mode with 2.8 or 3.3 kHz filters. The DDS is very clean and the audio is very clear and open in SSB. If you have 2 or more stations on an AM channel it is much easier to separate them with the R75. I think ICOM should try another solution to synchronous AM, preferably with a small lock in range. If I have 2 stations 50 Hz apart I can lock on either of them with the R71 PLAM which functions very good.

Noise blanker:The NB works fine on impulse noise on both receivers. The R71 NB is adjustable the R75 is not. The R75 NB also distorts strong signals (when it is not needed).

DSP:The NR can be adjusted between 0 and 15. A setting of 3 to 5 works fine, but I personally think it is a disappointment. When you press the NR button it sounds very good when the noise drops a lot but in fact all audio get weaker so the difference is just a few dBs. Still it can make the difference when signals are very weak. Like all kind of DSP the sound is a little strange to listen to. The ANF, the automatic notch filters, is quite good and eliminates most heterodynes, very easy to use.

Crossmodulation: No problems unless you use the Preamplifier 2 on crowded bands .

Not so good:The concentric knobs for the Twin PBT are not very easy to use with big fingers like mine. The pressure needed to push a button is a little to much. I like the R71 much better.

Recommendations:If you like to tune to hard to get stations on crowded bands I think an extra filter in the 455 kHz IF is a must. If you have to compromise I think a 2.8 kHz filter is a good compromise. At 50$ the DSP is clearly worth the money. If you are a BC DX-er you should try to remove the attenuator. If you have troubles with local stations it is very easily restored to the original.


Links for Additional IC-R75 Information (All Subject To Change Without Notice)

IC-R75 "eham" Reviews

IC-R75 Review by Michael Stevenson



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