The following are my evaluations of the 3 following transceivers:
YAESU FT-920 AGAINST YAESU FT-650 & KENWOOD TS-940S
A few weeks ago, I evaluated an FT-920 that was purchased in May, 1997, by a local ham. He bought the FT-920 as a back-up unit and so he never used it to transmit at all and compared it only for a few weeks against his IC-756 and IC-775DSP and FT-1000; and then re-boxed it until last month. When I took the unit to my radio shack, I performed all of the below-mentioned comparisons. The unit is now at the Yaesu California Service Center to get the NB/MONITOR audio level problem fixed; and the unit only provided 70-75watts output on 6M, but 100 watts on all the other bands--weird-----so, off it went, with the local ham's "explanation" letter inside the box, to get the FT-920 "looked at".
The comparisons were made from 80 to 6 meters and under conditions both ideal (no power line noise, no QRN) and adverse (power line bursts, high static levels, and fluttery, "in the noise", weak signals). Also, band activity levels (QRM) and signal strength dynamics were utilized to compare the ability of each of the 3 units to handle both "weak signals"and crunching S9 +40db signals spread across various bands on both SSB and CW.
Initially, I used the 6 Meter beacon, W1VHF/B (50.061) in Rhode Island, as a standard of "sensitivity" for both my FT-650 & his FT-920. I first turned my antenna north away from that RI beacon so that the signal was barely audible-----in-and-out of the noise floor in a "non-noise" & "non-powerline" environment; and then later turned the beam to my Southwest where I could hear the beacon with an S4-5 signal level but the signal was heavily "masked" because of high power line noise.
At the "no power line noise" direction to the North of my QTH, the FT-650 seemed at first to be more "sensitive" and had better "audio presence" than the FT-920. I later came to believe that this initial conclusion was due to the fact that I had been so accustomed to the receiver characteristics ofthe FT-650 over the past 4 years. So, when I switched to the FT-920, I "heard" a different sound from its internal speaker.
I then decided to use headphones for each unit to make the comparison "fair." When I turned the "Noise Reduction" knob clockwise on the FT-920, I got a lowering of the 6 meter signal audio strength but I noticed that the signal's audio "returned" after 2-3 seconds! I initially thought this strange until I remembered that Joe, K1RQG, had told me that the "NR" envelops the desired signal once the contours are mapped-out by thecomputer processor (so I guess an old dog can learn new tricks!).
I also found that engaging the DSP did not seem to "bring-in" the beacon signal better until I literally spent hours (during the course of the day) tweaking the 2 concentric DSP knobs. Then, I finally realized that small, incremental knob movements made big differences in the beacon's audio quality from the FT-920 (I would thus say that it does "take time" to getto feel a "new" radio's audio presence!).
Next, as I mentioned in the above paragraphs, I swung the beam directly to RI and heard loud S5 power line noise with the Noise Blankers "off" in the2 units. When I punched-in the NB on the FT-650, the S meter dropped fromS5 to S1-1.5; however, the NB generated a "distorted" effect on the beacon's audio. When I then pushed-in the FT-920's NB (even with the round knob fully clockwise), the S meter dropped to S1 and there was NO audio distortion! GREAT!!
Later that day, I tuned to 10 meters and compared all 3 units. I found that I initially again preferred the audio quality of the FT-650 on SSB signals and found that the TS-940s, with the SSB slope tuning knobs, gave more audio "punch/presence" than the FT-920. But again, after hours of listening to dozens of stations at various signal strengths on all 3 units, I found that I began to "get use to" the FT-920's DSP audio characteristics. I also found that the NR knob was only marginally, if at all, more effective in hearing weak signals on 10 meters.
I then narrowed the FT-650's SSB bandwidth from the default value of 2.4 to 2.0 and then to 1.8 and compared those SSB narrow filter bandwidths to the 920's DSP and the 940s's SSB slope tuning. I found that the 920 & 940s werea little "sharper" in rejecting adjacent splatter: but, of course, the 920& 940s had "variable" bandwidth controls and so could produce a better "tightness" around an SSB signal. I also thought that both the FT-650 & TS- 940s had better "audio presence" for my ears....but as I played with the 920's DSP and rocked the VFO back-and-forth, I got to the point where there was hardly any audio difference between the 3 units---and of course I could hear NO "sensitivity" differences.
I then went to 20 meters on SSB & CW. Both the 920 & 940s handled the crunch of QRM on SSB and both had the same capability of hearing the S1 weak ones amidst a pile of S9++ signals. The only thing I noticed was that with the 920's DSP engaged, an S9 signal on CW, but not on SSB though, "de-sensitized" or "pumped" the AGC (as mentioned to me by various other hams who own an FT-920). The 940s did not produce any AGC "pumping" o raudio distortion at all on CW. But, the 940s, with the NB fully clockwise,produced terrible audio distortion; while the 920's Noise Blanker was excellent and produced NO audio distortion!
On 80 meters, I noticed that the 920's NR knob helped immensely in reducing the static crashes and make very weak signals perfectly intelligible. I then decided to try the Transmit side of the unit. Right away, I noticed that I was only getting 70-75 watts on 6M but 100 watts on the other bands! I used my D-104 mic and went through the "Default" and Menu "Mic Eq"settings.
The 3 locals listening said that the "Default" was the best sounding with #1 and #2 as "much too tinny". When I added the Processor to the "Default" setting, the audio punch was noticeable and did not distort, even at the 4 o'clock position. When the unit returns, I'll try my Heil HC-4 element headset and 2 other mics that I have around.
So,..... where were the FT-920 Problems?
I found NO differences in either sensitivity or selectivity between the FT-920 & TS-940s (even with ALL the mods. & staggered IF crystal filtersincluded in the unit). But I did notice audible, relative "wideness" of selectivity on the FT-650 even with its narrowest SSB filter engaged.
- On CW, with S9+ signals on 40 meters, I noticed that (as per QST's October 1997 "Product Review" article) the opposite side of zero-beat produced an audible signal! However, when I punched-in the optional Yaesu500 hz CW filter, the signal disappeared about 99%; and, when I engaged theDSP cuts, the "reverse" audible CW signal was gone COMPLETELY! (even for anS9 +20db CW signal).
- AGC "pumping" on CW only when an S9++ signal is in the passband of theDSP.
- The only serious defect is the "crosstalk" and weird buzzes and high pitch whines generated when the NB is activated while simultaneously the MONITOR LEVEL round knob is turned past 10 or 11 o'clock. And this is what the factory says it will fix for my local ham buddy.
The only "noticeable/real" differences were in the 920's CW-mode AGC "pumping" and CW (wide) "blow-by" on S9++ signals but the CW "blow-by"problem was corrected by the use of Yaesu's 500 hz CW filter in conjunction with DSP--however, a marginal residue of AGC "thumping" was still evident on CW.
Secondly, one must get "use to" the changing audio characteristics of both the DSP knobs and the NR knob on the FT-920. These 2 knobs must be constantly "tweaked" to affect the desired audio characteristics...but,when I figured out what an "average" signal should sound like, it was then easy to further refine the DSP audio as band/QRM conditions changed.
ADDENDA (2/27/98--Thursday; and 3/1/98--Sunday):
I played around for a few hours on 10M with both my FT-650 & Dad's TS-940s (and Dad has all the IRCI filters and related mods).
I concluded that the 940s does indeed have a small amount of CW "blow-by"when the rig's CW VBT knob is turned slightly counterclockwise from its"default" position of 5 o'clock. Consequently, if the CW VBT knob is turned to 4 or 3 o'clock, the "blow-by" pitch becomes almost as noticeable as in the FT-920 unit. But, as in the FT-920 unit, when the "narrow" filter on CW mode is engaged in the TS-940s, the "blow-by" is eliminated (the same thing happens when I engage the FT-920's 500hz CW filter).
The FT-650 also has CW "blow-by" and is faintly noticeable but the signals are way down and you have to really "concentrate" to hear it or else you would "skip by" it inadvertently! Also, I noticed, after careful"re-listening" to the WA1OJB/bcn (50.066) that came back on-the-air Sunday(March 1st), that even when I had that beacon at S9 +50db, I did hear some"blow-by" on CW and some AGC "pumping away"---however, I could still hearany weak signal or carrier on the reverse side of WA1OJB/bcn's zero-beatfrequency. It was thus NOT as annoying as hearing a perceptible series ofCW notes on the "blow-by" on the FT-920 in the wide CW mode setting.
Secondly, when comparing my FT-650 with Dad's TS-940s, I concluded that the SSB Slope Tuning knob on the 940s was much more "selective" in reducing the bandwidth and thus reducing adjacent channel splatter/QRM than was the FT-650 even with its 1.8 bandwidth filter engaged. But because there were not too many S9+ stations copyable at the time of my observations, I wasunable to determine which unit had better "Dynamic Range" or "3rd OrderIMD". This test component has to be conducted under "bone-crushing" S9++++sigs all over the 10M band. I'll have to wait until the band is open solidly for an hour or so.
A NOTE ON THE FT-650: I also observed that the FT-650's SSB "skirt selectivity" was much better as I pushed-in the various 4 "narrow" SSB filters. I could hear the adjacent splatter decline in volume and become more "narrow" in frequency as I switched from the 2.4 to 2.2 to 2.0 to 1.8filters!
But, as I stated above, the FT-650's selectivity was never as good as the TS-940s's (and I still had plenty of SSB Slope Tuning knob turning to do to "narrow" the selectivity even more sharply). This is the ONLY "disadvantage" I found in comparing the FT-650 with Dad'sTS-940s!!! And I'm telling you that I was even listening to signals thatwere "below" the noise threshold where I could only copy 1/2 of the words!As "they" say, if you can't hear the "tea-weak" ones, the receiver is...well...buy another one!
"Lefty" Clement, K1TOL
Lefty's comments about the INRAD filters
May 25, 1998
FT-920 UPDATE: NEW INRAD COMPANY SSB & CW FILTERS INSTALLED
Since last week, I have been experimenting, on all bands both SSB & CW, with INRAD's new 2.1hz SSB filter and its 400hz CW filter.
I originally had mounted Yaesu's optional 500hz CW filter but wanted to try out a narrower one. From "audio tests" they both have the same "hearing" quality but I think that the 400hz CW filter is somewhat quieter in terms of background noise. The new CW filter is definitely sharper and on an s-9 signal, there is hardly any noticeable "blowby" with DSP engaged.
Additionally, the new 400hz CW filter eliminates the DSP's AGC "pumping" near an extremely strong s-9+ CW signal. I can now "drop-off" to zero a signal at say 14.005 that is s-9+ at zero-beat frequency of 14.006 (now that's sharp!).
On the SSB side, the new 2.1hz SSB filter really narrows the bandwidth especially with DSP engaged. An s-9+ signal say on 14.200 can be "dropped-off" to inaudibility on both 14.202.5 and 14.197.5.
The only drawback to the new 2.1 SSB filter is that the RX audio loses some of its bassiness and so a movement of either the SHIFT knob or Menu adjustment is a strong suggestion (so as to suit one's hearing). I opted to use the Menu to adjust the RX carrier offset and found that I could even "tighten" my DSP Low Cut knob even further to eliminate adjacent splatter, etc.
An adjustment may also be made on the TX audio side as the new SSB filter enhances the "highs" on some microphones. Nothing in the TX's audio presence or "punch" is lost though even with some carrier adjustment.
More comments from "Lefty"
DATE: March 30, 1999 (2nd evaluation date)
FROM: Lefty, K1TOL
TO: Mark Downing, WM7D
RE: 2ND EVALUATION OF YAESU FT-920 WITH INRAD 1.8 KHZ SSB FILTER...and after a year of on-air activity
Hello Mark (again!):
Now that I have had a few months to evaluate the INRAD 1.8 Khz SSB filter in my FT-920 and have had the unit for almost one year, I wanted to send a 2nd evaluation contribution.
I initially thought that the 1.8 SSB filter might be too "tight" but these fears were unfounded. You can use the FT-920's MENU TX & RX settings to adjust the Receive sound to your ears; and the Transmit audio settings can be likewise adjusted for "best" TX audio quality. For example, on RX audio, I now set the "RUSBCAR" MENU #U-61 to -0.225; and on TX audio, I set my D-104 microphone via the "TUSBCAR" MENU #U-62 to -0.150 with the MIC-EQ MENU #U-51 setting to "off"; and set my Heil headset via "TUSBCAR" MENU #U-62 to -0.075 with the MIC-EQ MENU #U-51 setting to "1" or "3" or "4" (depending on your audio preference). Of course, these are only "preferences" and there is quite a latitude in setting the range of settings; but, the point is that when a narrower SSB filter is installed, you have to adjust the RX and TX parameters to obtain the best audio sound in both the RX and TX mode.
Also, if you feel that you are "going-over" a signal too quickly with the 1.8 SSB filter, you can adjust the dial speed from MENU #U-01 (it can be set to a "4" or "2" depending on how fast/slow you want to dial across a signal). Or, you can also use the STEP button on the front panel to get "FINE" tuning steps (but this FINE step tuning is too slow for my tastes).
To conclude, the INRAD 1.8 SSB filter is very sharp: I can drop-off a 59+40 db signal on 20 meters to NOTHING about 2.5 khz each side! It certainly is a welcome addition on any crowded band.
My FT-920 is constantly on and I put it through its paces in last June's ARRL VHF Contest. So far, I have not had any problems. I have had excellent TX audio reports with different microphones at different MENU settings. The PROCESSOR has punch and does not sound raspy or "overly processed" (I set it for 2-3 o'clock). The NB performs better than the one in my FT-650 and Kenwood TS-940s. And, the NB does not distort the audio quality even when loud powerline noise is present with an extremely strong signal on the band!
The only three complaints so far are:
- Yaesu should have placed an "ICON" on the screen when VOX is activated. This is a source of frustration especially when switching from CW to SSB...and I forget to disengage the VOX button.
- There are also minor errors in the booklet regarding setting-up the DVR (Digital Voice Recorder). I experimented with various microphones and found that the MIC GAIN setting, in the DVR mode, does have an impact on how the TX sounds in playback. I learned to set the MIC GAIN down to 9 o'clock, reduce the RF PWR to low power (counterclockwise to 7 o'clock), and turn-off the PROC when recording a message with the DVR. Then, in playback, I turn all my TX audio settings back to their original positions...and the TX audio sounds fine over-the-air.
- One aspect on RX that I noticed was that an extremely strong SSB signal would create a high pitch audio whine (a spur or image?) as I tuned back-and-forth across its signal. But, when the DSP function was engaged, the audio whine (or spur or image?) disappeared. I guess the DSP works well!
"Lefty" Clement, K1TOL