W8WWV - ICOM 756 and 756PRO (and PRO II)

Greg Ordy


Last Update: Wednesday, February 26, 2003 05:59 PM

756 and 756Pro

I decided to replace my ICOM 756 with a 756PRO. This gave me an opportunity to compare both radios side-by-side. This page contains my observations. Additional 756PRO information can be found on the pages maintained by Adam, VA7OJ/AB4OJGary, VE3SOU, WA0SXV,  the ICOM reflector (mailing list) at QSL.net, the eHam equipment reviews and of course, the ICOM site. If you have any of your own observations, please email me, and I will add them to the list if appropriate.

ICOM introduced the PRO II radio in the second half of 2001. As of this writing, the radio is still quite new, and comments and observations are just starting to emerge. A few of my observations are contained at the end of this page.

Because I am comparing two radios here, it may appear as if one is good and one is bad. I really do not want to give the impression that either radio is bad. In fact, given the cost difference between the two radios, I think that both are well worth their respective prices. For me, I decided that the upgrade cost made sense because of the equivalent cost of the filters necessary to turn a 756 into a PRO. Of course this is not even possible because the 756 has a single filter slot at each IF frequency. But if there were more slots, it seems as if I would need to add 6 or so filters to be able to get the SSB and CW selectivity choices I would like. At $100 to $200 (USD) per filter, the cost difference between the radios evaporates. On top of that, there is the color display and a number of other enhancements. So, for me, spending the extra money made sense.

Topics:

I think we have all learned that S meters are, at best, relative signal strength indicators. S Units are not a standard. S meters are not calibrated against an absolute signal strength reference. Still, they are all we have to measure signals, and they are often quoted.

With two radios it's very easy to compare how each reports signal strength.

On both radios, the difference between S8 and S9 appears to be 6 dB, a typical value. Above S9, the meter readings are fairly accurate, which is to say that meter markings track real relative decibel changes. Below S8, both meters becomes increasingly more sensitive. The difference between S1 and S2 may be as little as one decibel or two.

I also found what I call a tracking difference between the two radios. The mismatch was the greatest on 20 meters, where the 756 read the same signal as 8 dB stronger on its meter. The difference was about 5 dB on 40 and 15 meters, again the 756 reported a higher value. On the other bands, the two radios basically tracked. Their S meters indicated the same strength for the same test signal.

The S meter on the PRO is also what I would call sluggish. The S meter on the 756 seems to follow syllables in words, and the dits and dahs of CW. The meter on the PRO moves more slowly, regardless of AGC speed.

Finally, there appears to be no adjustment on either radio for S meter calibration. The meter itself, which reports several different qualities, is driven from a microprocessor. The meter readings are not the result of analog signals changing, they are the result of a numeric computation.  What you see is what you get.

Since I made my first comparisons, I have made a closer look at the S Meter. That information is on another page, and if you have a 756PRO, you might want to check out my S Meter Lite software.

I have written about ICOM radios and microphones on another page. With the 756, I found it difficult to drive the transmitter to full output with a dynamic microphone element. I had to use an electret condenser element (or a dynamic element with a pre-amp). The PRO appears to have more available microphone input gain, and I can drive it fully with both dynamic and electret condenser elements.

Page 12 of the PRO Instruction Manual depicts the back panel of the radio. The PRO, and not the 756, has an additional jack, the Transverter Jack. This jack has been added directly next to the Receive Antenna Connector. Both are phono (RCA) jacks. The documentation for the PRO incorrectly reverses the two jacks, Transverter and Receive Antenna. This mistake is repeated every time that either jack is shown in the manual. The labeling on the back panel of the radio is correct.

The PRO has a transverter I/O jack, the 756 does not. The transverter function is activated by placing a 2 to 13.8 VDC signal to pin 6 of the ACC2 jack. When this is done, the radio receives through the transverter jack, and transmits a -20 dBm signal on the same jack.

This observation applies to both radios. The front panel has a NB (noise blanker) button, which activates the noise blanker function. There are no additional adjustments. Many people report that the noise blanker does nothing and is a useless control. My observation is that the control is effective if you consider it to be an ignition noise blanker. From time to time, I have ignition (spark plug) noise near the house. This is usually due to a chain saw or air compressor. The noise blanker is very effective in removing this type of noise. For general atmospheric noise, however, the control does do very little. I suspect that ICOM believes that the NR (noise reduction) control should be used to deal with that class of noise.

The spectrum analyzer on the PRO is much more sensitive than the one on the 756. Signals really jump out on the PRO, whereas the scope can be nearly a flat line on the 756, especially on the upper bands when the band is quiet. At first, the difference was so great that I thought that there must be a change in the fundamental computation of the scope data, in addition to an increase in scope gain. But after trying to carefully watch both scopes at once while changing the scope attenuator on the PRO, I am of the opinion that both scopes are the same, except that the PRO scope has about 15 dB more gain. The PRO scope does have several scope attenuation settings which can be used if desired.

Both scopes are influenced by the pre-amp setting. The scope is after the pre-amp, so increasing the pre-amp gain will increase the scope gain. I found myself often increasing the pre-amp gain on the 756 just to make the scope more responsive. With the added gain in the PRO, I only use the pre-amp to improve the audio, not the scope.

The PRO also has a two-color mode that uses a muted second color to indicate the maximum signal at each frequency (while the first color follows the signal). When you turn the VFO, the display starts to recompute the maximum signals. While this is the factory default setting, I find it to be annoying, and I turned it off as soon as I figured out how to do it. I suspect that this was done to give some sex-appeal to the color display. I don't find it useful, however.

Much has been written and spoken about the so-called audio distortion on the PRO. Here's my opinion.

Using the small built-in speaker is not a good way to listen to the radio. An external speaker, or better yet, an external amplifier and speaker connected to the audio out (not the speaker out) is much better. I have all three. The internal speaker, an external speaker, and I feed the audio out into my computer sound blaster card where I can route it to some good quality multimedia speakers. As the speaker gets better, the PRO audio quality also gets better. That's hardly shocking. The same can be said for the 756.

Still, there is what I would call a brittle quality to the PRO sound. At the extreme, it's harsh. As best as I can guess, it's due to the digital IF. In some sense, it's a signature of such a large amount of digital processing. In fact, I think that the 756 has a more pleasing sound than the PRO. I would much rather listen to a fat and rich AM broadcast station on the 756 than on the PRO. The PRO filters are claimed to be very sharp (shape factor), and this will color the audio as well, especially when there are a number signals surrounding the desired signal. I would not be surprised if this phenomena was similar to what happened when CDs were introduced in the early 1980's. At first they sounded crisp, brittle, and sterile compared to analog medium, which was warm, lush and full.

I find the CW sound to be the most interesting, especially with using a narrow filter setting. On the 756 (350 Hz filter, 9MHz IF), it sounds like you are listening to a narrow wedge of spectrum. Narrow but natural. When a signal appears, you can hear the character of the transmitter quite clearly. On the PRO, with the same filter width, it's as if you are listening to a computer reenactment of the spectrum. Of course that's what it is. Narrow but artificial. When a signal appears, it's more of a synthesized replica sound as opposed to the underlying transmitter sound.

On several occasions I have looked for weak CW signals and tuned both radios to the same frequency. It seems as if both radios have similar sensitivity. If you can hear it on one radio, you can hear it on the other. The difference I found was that I could hear the dits and dahs more clearly on the PRO than on the 756. Especially with higher speed CW, very weak signals blur together on the 756. Even if you can hear the signal, you can't copy the text. With the PRO, it is often possible to hear and understand the CW. The edges of the dits and dahs are sharper and cleaner.

In summary, and when comparing just these two radios, I find the 756 to be warmer and smoother, whereas the PRO is colder and more brittle. It does seem, however, that the signals from the PRO are somewhat more intelligible and understandable. It's communication, not HI-FI.

Both radios feature an auto notch which is in the audio chain, after the AGC. While they effectively remove carrier tones from the audio signal, the impact of the (usually loud) carrier on the receiver front-end is unchanged, meaning that the receiver gain is reduced. This often makes the desired signal undetectable. This is no more than the common AF DSP notch.

The PRO, however, has an additional manual notch which is implemented at the IF DSP level, and is before or at least within the AGC loop. Of all of the features on this radio, this is the one feature that I would call amazing. The notch is quite narrow, and one must adjust the knob carefully. But, when you hit the frequency, the tone goes away, and the S meter drops as gain is restored to the front-end. The desired signal again appears.

It is possible on the PRO to read the S meter value from the computer (serial) interface. This is not possible on the 756. My S Meter Lite software works with the PRO.

Both radios feature what ICOM calls triple band stacking registers. What that means is that the radio memorizes three different frequency/mode combinations for each band. You cycle through the choices by pressing the same band button multiple times. This lets you store, for example, a favorite CW frequency, digital frequency, and SSB frequency. Just keep pressing the same button until you get to the one you want.

One of the bands is the so-called General Coverage band. I would like to program my favorite local AM broadcast station, 10 MHz WWV, and 15 MHz WWV. For some reason, neither radio will allow me to get those three frequencies on the general band registers. I think this all comes down to the definition of the word band. We know what that means in the amateur case, but in the general case, it is conceptually the entire receiver range. But as you turn the dial across the receiver range, in the general band, you do hear, from time to time, beeps, which normally signify band edges. They may correspond to the common shortwave broadcast bands, but I have not verified that. In any case, these beeps do appear to trap a register in a band. So, some frequency combinations do not appear possible. This is a very small point, and I doubt if this is a bug, as opposed to just the way that it works. But, it is not documented, and doesn't make obvious sense (to me!).

The 756 has audio speech compression, whereas the PRO as RF compression. Only the PRO has a meter position that indicates the compression amount. The manual suggests between 10 and 20 dB of compression. I have found that much lower settings are effective without sounding like a typical compressor (jet engine in the shack). It should be remembered that I use a headset microphone that is very close to my mouth.

The PRO has a built-in voice recorder. The 756 does not. Note, however, the PRO voice recorder is not very useful. On both receive and transmit you can record up to 4 different segments, each up to 15 seconds long. The received segments can only be played on the speaker, and the transmit segments can only be transmitted and reviewed on the speaker. Two additional capabilities would have made the recorder a much more useful feature. First, the ability to play back received audio on the transmitter (let your friends hear how they sound at your place), and the ability to trigger the transmit messages from the computer interface (to be done so by logging software). Without these features, the voice recorder is basically a gimmick. The Yaesu FT-920 has about the same problems.

Another great variation would be to allow the voice recorder to record continuously, and be able to replay the last 15 seconds on command. I would really like this for capturing DX exchanges, where I would like to make sure that my call was copied correctly. Of course you never know that the DX is coming back to you until it's too late to hit the record button, so you really can't start recording on cue. It's much better to be continuously record, then stop recording after the important part of the exchange.

This is one control that does not impress me very much on either radio. The function certainly seems nearly identical on both radios. It appears as if the intent of this control is to remove atmospheric (and other random) noise from a desired signal. As you increase the reduction value, the noise is indeed scrubbed away, but so is the readability of the signal, especially on SSB. The control changes the signal/noise sound, but to me, it never really improves it. I find the control most useful on low settings, around 9:00 o'clock. This is helpful for taking the edge of noise bursts while ragchewing. I certainly don't see how this control could be useful in weak-signal work.

I looked for a number of what I would call weak signals. These included CW signals on an otherwise dead upper band (no background noise at all), and weak SSB signals in the 75 meter DX window (little background noise). In all cases, the radios had very similar sensitivities. If I had to pick the more sensitive radio, however, it would be the 756. Please note that I conducted my tests with both pre-amps off. Since the pre-amps appear to add the same amount of gain, I do not believe that the pre-amps would change my comparison.

Given the brittle sound of the PRO DSP, and coupled with the slight edge in sensitivity going to the 756, and assuming the same filter bandwidth in both radios, I would prefer the 756 (receiver) over the PRO. It's close, but the warm and lush analog 756 is very appealing. The IF DSP needs to offer just a little more to truly pull ahead of the established analog technology.

The conflict is that the 756 has a single filter position available at each IF (9 MHz and 455 KHz). This means that it is impossible to get as many filter choices as I would like. As a compromise, I would put the 350 Hz filter at the 9 MHz IF, and a 250 Hz filter at the 455 KHz slot. The default SSB filters would be used. In my opinion, this would give the 756 SSB, wide CW, narrow CW, and RTTY filtering. It would be a very appealing configuration.

The primary appeal of the PRO is the large number of filter width choices. I believe the number is over 40. Given the number of free filter slots in the 756 (see the Sensitivity comments), the PRO has substantially more filter choices. The way that the radio is set up, it is convenient to think of three filter settings per mode. Each of these settings can be changed, but I found myself picking my three favorite settings and then not changing them that much.

On SSB, my most common filter settings are 2.8, 2.4, and 1.8 KHz. These values are close to the factory defaults. I find myself lowering the center frequency, however, in order to better match the typical male voice, and to reduce the high end hiss. The filter selection does make quite a bit of difference. Normally, I'll use a 2.4 KHz filter for DXing, and 2.8 KHz for ragchewing. When the local signals are good, it's nice to be able to crank up the bandwidth and get a fatter sound, approaching AM or FM. The real value of the filters comes in when an interfering signal enters the passband. On many occasions I have had hash and garbage really eat into the desired signal. By going to 1.8 KHz, the interference is clipped off. Coupled with the manual notch to remove carrier tones, it's a powerful combination. One can go below 1.8 KHz when necessary. I do find myself reaching for the filter adjustments and it's great to be able to adjust center frequency and width. Very flexible and powerful. I no longer accept adjacent channel interference, I try to get rid of it. It can usually be done.

On CW, my most common filter settings are 1.2 KHz, 350 Hz, and 100 Hz. I think I use the 350 Hz setting since that's the filter width I have in the 756, and I have wanted to duplicate that in the PRO (for comparison tests). I thought at first that I would always use a very narrow filter. But in practice, I like to start off wide, and go narrower as needed. In some sense, the wider CW filters are used for spotting, that is finding activity. Here's where the more sensitive spectrum scope on the PRO is very nice. When using a narrow filter (100 Hz, for example), it is easy to simply miss signals. The scope will show me that a signal is there, and I rock the VFO back and forth in order to find it. When you get very narrow, tuning can be critical. That may be the time to turn on the RIT, in order to make sure that the transmit frequency does not change.

On SSB transmit, there are three selectable widths. It's hard to understand why one would leave the wide setting. I should explain that I have never been a fan of the classic narrow bandwidth contest audio - it's no fun to listen to for any length of time. I do admit that it does have its moments. I have had the following scenario happen more than once. I will be one of many stations calling some rare DX. After perhaps a dozen calls, I will finally realize that  under the existing conditions, my signal strength is nothing special, I am one of many. I'll then (hopefully) remember to narrow my transmit audio bandwidth. In many cases, I've made the contact on the next call or two. I can only believe that the additional punch made the difference.

I wish that these radios had a carrier offset adjustment for SSB transmit, like on some Yaesu radios.

After over 30 years on HF, I finally tried 6 meters in the summer of 2000, with the sunspot cycle near its peak. It was quite a bit of fun. Both radios support 6 meter operation. What I wanted to share on this page was the high value of the spectrum scope on this band. When an opening occurs, the scope makes it very easy to find the activity. This is especially true on SSB, where stations tend to gather at 5 KHz spacing on and above 50.125 MHz. It's easy to keep track of all of the activity on the band.

Apparently the phrase Twin Passband Tuning has been an ICOM signature on a number of radios. It is the ability to exploit IF shift at two different IF frequencies from one set of concentric tuning knobs. The effect it creates is the ability to both modify (in width) and shift the effective passband. The 756 even presented a little picture of the virtual passband, which changed as you adjusted the knobs. ICOM has retained the Twin Passband Tuning terminology on the PRO, and I don't think it makes much sense.

First of all, the phrase is technically incorrect since one is no longer shifting twin passbands. All of the adjustments are within one IF within the DSP. Of course this is actually a simplification of the way to think about filters, since now we have what we always wanted, which is to talk about the filter in terms of filter bandwidth and filter center frequency. In my opinion, the PRO knobs should have been labeled Bandwidth and Center, as opposed to Twin PBT.  I think they didn't want to scare people away who might think that their big feature was removed. It isn't removed - it's better, but they used the old language. This is just a small user-interface issue. If you go into the filter adjustment mode on the PRO, you have a complete picture showing the filter width, starting frequency, center frequency, and top frequency.

The 756 has a feature called APF, Audio Peak Filter. It really is nothing more than an audio filter used with CW. It has 3 selectable bandwidths, 80, 160, and 320 Hz. The center frequency is also adjustable to match your favorite CW pitch. This feature is not on the PRO, and it does not need it, since one can create an IF filter which is as narrow as 50 Hz. An IF filter should always be better than an audio filter.

The 756 lets you select one of three (slow, mid, fast) AGC time constants on non-FM modes. The PRO gives you the same three selections, but the underlying time constants can be user specified in a configuration table.  It seems like there is more to adjust here than one would ever need.

Much has been written and said about the so-called intermod problem on the PRO. Part of the problem is identifying exactly what it sounds like. Here is a message from the ICOM reflector by Sean, K3XT, that is a good description of how to hear the problem for yourself (or at least one version of it) (reprinted with permission).

I was on 40m this morning and ran across K8JW saying how he returned his Pro because of unacceptable DSP intermod problems in crowed bands.  He said he contacted Icom and they refused to acknowledge the problem.  He told me how to hear these intermod products.  I tried the below procedure and sure enough you can hear them.  Note, this is intermod products not an audio distortion issue.

-SSB-
Select SSB filter of choice. Tune VFO to a quiet area of a band that has S8 or stronger signals on either side (+- 10 KHz) of your VFO frequency. Set your band scope to +- 12.5Khz to see these signals transmitting. Put on your headphones (in my case Heil pro set that have a good bass response).  Turn the audio (AF) knob full counter clockwise (off) then turn it clockwise till you hear a faint pop (7:30 position)(DSP audio has just kicked in). You can hear a faint low tone rumble of the various mixing products of the adjacent signals.  You can see the signals on your scope corresponding to the intermod you hear.  These intermod products are very faint and is a non issue because as you turn the volume to a normal audio level (9 o'clock) the noise and/or signal quickly masks these intermod products.  The intermod products do not get louder as you up the volume control.  It is a different story on CW.

-CW-
Select CW filter #2 (500Hz). Tune VFO to a quiet area of a band that has S8 or stronger signals on either side (+- 10 KHz)(actually, one signal will do) of your VFO frequency. Set your band scope to +- 12.5Khz to see these signals transmitting.  Put on your headphones.  Turn the audio (AF) knob and set your volume to a comfortable level, in my case it is 9 o'clock.  At this point you will hear what sounds like key clicks that are very low in frequency.  You will hear these intermod products even at normal volume levels.  Even if you tune the VFO to a CW signal, you can hear these low level intermod products between the pauses of the CW characters of the station you are listening to.

I can not hear any of these intermod products with my SP-21 external speaker, only with my headphones. Serial number for my Pro is 1698.

Sean - K3XT

I can hear these artifacts on my PRO as well. I don't think that the word intermod technically applies because intermod or cross modulation requires two signals. These artifacts can be heard with a single signal. That's really not important, since the sounds are real. They are weak, but they are there.

In my opinion, these sounds are part of the overall brittle sound that I hear from the PRO. Normal SSB and CW signals are surrounded by little clicks and pops and thumps. I believe that they are artifacts of the IF DSP stage. Again, a signature of the technology at this point in its evolution. These sounds are not found on analog radios, at least the ones that I have used, including the 756. I also find that these sounds do not interfere with copying the desired signal. They are a distraction at best.

Since this page is about comparing the 756 to the PRO, I thought I would conduct a CW keying test. I set up my 756 to transmit into a dummy load on 28.100 MHz. I tuned the PRO to the same frequency. By adjusting the transmit power level, and the receiver attenuator, I was able to create signals at three levels, S9, S9+20 dB, and S9+50 dB. I transmitted a string of dits and tuned the PRO above and below the center frequency noting when the CW signal was no longer detectable in a pair of headphones. I then reversed the setup, and transmitted on the PRO, and received on the 756. Here's what I found. The detectable bandwidth is listed in the table. Both radios had a 350 Hz CW filter setting.

S9

S9+20 dB

S9+50 dB

756

2.25 KHz

8 KHz 25 KHz

756PRO

8.5 KHz

10 KHz 13 KHz

For very strong signals, the 756 is twice as wide as the PRO. An average S9 signal, however, can be heard 8.5 KHz on the PRO (only 2.25 KHz on the 756). The artifact that is heard is very weak. It does not affect the receiver gain, and it does not obscure real signals.

The IF DSP on the PRO makes it a new radio and new experience. For me, I can live with the artifacts in order to get so many filter positions. The artifact sounds are unexpected, but I do not find that they interfere with copying the desired signal, even when it is a weak CW  DX signal with many callers only a few KHz away.

Both radios feature adjustable bass and treble settings on the transmit audio. The 756 allows adjustment from -12 dB to +12 dB in steps of 2 dB. The PRO settings go from -5 dB to +5 dB in steps of 1 dB. On the air testing suggests that PRO range is indeed limited, and does not provide significant changes.

The PRO features three different transmit audio bandwidths (on SSB). The bandwidths are fixed, and are called narrow (2.0 KHz), middle (2.6 KHz), and wide (2.9 KHz). The width does indeed change, and is clearly detectable both by another station, and in the audio monitor. Note that the transmit audio bandwidth is independent of the receive audio bandwidth.

NOTE: In January of 2002, I learned that some amateurs had discovered that models of the 756 past a certain serial number were built with a normal/wide transmit audio bandwidth switch. The serial number of the change appears to be around 3,000. The switch is totally undocumented, and is located within the radio. The switch, S801, is on the bottom of the radio. I do not know where it is located. The swiched is marked N (normal) and W (wide). By default, it should be in the N position. If you move the switch to the other position, your transmit audio bandwidth will become wider.

When the first rumors of the PRO broke, I was hoping that ICOM would add IF DSP to the 756, while keeping the existing 756 IFs and filter arrangement - perhaps with a few more filter slots.  The PRO implements a different set of IFs, with the DSP at the last stage before conversion to audio. The DSP is responsible for almost all of the receiver selectivity. In the end, DSP still does not seem completely up to the task, although it is getting very close.

It's hard not to compare the 756 and the PRO against the Yaesu FT-1000MP, and the new Mark V. The Yaesu radios are known for their immunity against interference from strong signals near the desired frequency. Still, the DSP implementation in the Yaesu radios, in my opinion, is very primitive. What I would really like to see is a quad conversion receiver with a Yaesu front end, complete with extensive filter options at 2 IF stages. The final IF stage would be the PRO implementation. For me, this would be an irresistible combination. The early IF stages would establish the approximate desired bandwidth, and the final IF DSP would realize the exact desired bandwidth. [update, June 2002: The TenTec Orion appears to take this approach, and is a blend of the strengths of the Yaesu and ICOM radios, while attempting to fix all of the problems. If it can perform up to expectations, it should be a very fine radio.]

ICOM PRO II

The ICOM PRO II is an update of the PRO. It completely replaces the PRO, and ICOM has discontinued manufacturing of the PRO, building only  the PRO II instead. In my opinion, it a evolutionary update, not a revolutionary jump forward. At this point in time, the radio is starting to be used by amateurs. Detailed use information is just becoming available.

In visiting the excellent web site of Adam, VA7OJ/AB4OJ, I discovered a link to an FCC web site. [The manual may also be downloaded from the ICOM Information and FAQ Page] This web site contained an on-line copy of the PRO II user's manual, which apparently was submitted to the FCC as part of the approval process. I downloaded the manual, and compared it, page by page, to my PRO manual. While I make no claims that I discovered every difference, those that I did find are listed in the following paragraphs. [By early 2003, ICOM made available many of its manuals on its web site. Click on Download.]

1. In general, the time that you have to hold in a button to activate an alternate function has been reduced from 2 seconds to 1 second. This appears to apply across the board.

2. Page 4. The front panel Bk-In Delay and Key Speed knobs have been swapped.

3. Page 4. The Speech button has been turned into the Rec/Play button for Audio Recorder Channel R4.

4. Page 6. The Lock button has been turned into the Lock/Speech button. To activate the 'old' Speech function, press the button for 1 second.

5. Page 11. The Screen Menu Arrangement is changed. When completely backed out of all levels of menus, the 'soft' buttons are now labeled: Scope, Voice, Keyer, Memory, and Scan, as opposed to Scope, Voice, Memory, Scan, and Set.

6. Page 27. New Noise Blanker level set mode. Adjust the value from 0 to 100 percent.

7. Page 27. New DSP Filter Shape set mode. Select Soft or Sharp for CW and SSB.

8. Page 37. New Preamp explanation section.

9. Page 38. DVR Explanation improved. 90 total seconds of XMIT audio capture possible.

10. Page 39. One-touch voice record and playback described.

11. Page 50. Reference to IC-PW1, IC-4KL, IC-2KL/IC-AT500 in the original PRO manual replaced with just a reference to the IC-PW in the PRO2.

12. Page 67. Display Type. There are now 8 display types, as opposed to 4 in the PRO.

13. page 68. DSP Filter Set Mode described. Soft/Sharp selections.

14. Page 74. Quick Rit/ DTX Clear set mode described.

15. Page 74. SSB/CW Synchronous Tuning set mode described. Claims to keep the signal tuned in, even when going from SSB to CW. The frequency may be automatically shifted.

16. Page 74. CW Normal Side Mode added. Selects the carrier point of CW mode from LSB and USB.

17. Page 74. External DVR (digital voice recorder) triggering interface schematic presented. Uses pin 3 from the front panel microphone connector. By using up to 4 switches, and some resistors, you can trigger any of the recorder channels, or the CW memories (if in CW).

18. Page 75. CI-V radio address (default) is 64h on the PRO2 and 5Ch on the PRO.

19. Page 83. General frequency coverage now specified by country. 5 countries specified.


Comments

[I composed the following comments for the ICOM reflector]

No new controls or connectors were added to the case. I am talking about physical holes.

It has already been discovered and reported on this reflector that you can use two different DSP receiver filter shapes - on CW, with the existing PRO. As best as I can tell by experimentation, you cannot get at the CW or 'shaper' filter in SSB. I do not know if the 'soft' and 'sharp' filter shapes in the PRO2 are something new and different. If they are not, then there is no net improvement for CW, and the only change is that you can now listen to SSB with the 'sharp' CW filter shape. I wonder if that's useful?

I felt that the PRO digital voice recorder was nearly useless due to the user interface. The PRO2 is much better, what with the dedicated front panel button, and the ability to connect a simple external switch to trigger playback. That same switch works with the CW memory keyer too, which is a definite enhancement. Still, you cannot trigger the recorder from the computer interface, which would make it possible to run the radio completely from the computer keyboard, which is often very nice in contest situations.

For me, the possible added value of the PRO2 comes down to the receiver changes. Until somebody can do a side-by-side comparison, it's all guessing. My only fear is that ICOM made changes that impact measurement numbers, but did not really improve the receiver. Many folks really follow the numbers in the various popular reviews, and take them as an absolute ranking of the current crop of radios (usually to justify their purchase decision). A few dB will change certain rankings, but might not be audible. I hope that the changes do make a (useful) difference.

Anybody directly comparing the PRO2 to a PRO should also see if the new 'soft/sharp' CW filter shapes are what already exists on the PRO. My guess is that they are the same, meaning that all that has been added is the ability to listen to SSB with the 'sharp' filter shape. It remains to be seen if that is a good thing.

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