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Testing the DYC-817 Dynamic speech compressor

Hi Ed
I have just finished importing my logs from yesterday and as you can see I spent most of my time on GW/NW-043 on HF and I was very impressed with the result. This is the first time for about a year to reach the USA.
My setup is a standard 817 no amp and using a Sotabeams 20/30/40M dipole which I added 60M myself for the extra band.
I have opened the Speach Compressor photo below

both pots are at 12 o’clock and I adjusted to see where they were set, both are 1/4 turn clockwise from the starting position. (I hope that makes sense).

As you can see the dipole is not that hi either. My pole at the moment is only 6m and the balun centre is about 5m in the wind.
After carrying out the tests with my first QSO Gerald I used the Speach Compressor for all of the other SSB contacts, so was it just a good day or could more people hear me? I think the the Compressor helped.
I will defernatly be using it from now on. I hope to be out again next weekend.


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Yes, that makes perfect sense - thanks for doing this Paul and congratulations on all of the good contacts! The antenna you have is very similar to the one that is always in my bag, The SOTAbeams 80/40/30/20m Bandhopper (also with an extra self-made 60m section that replaces the 80m one) with a LambdaHalbe 6m pole as I’ve found it to be the most reliable antenna solution. I keep trying more complex ones, hoping for an improvement and the VP2E does indeed seem to be better but it’s more difficult to put up, so unless I’m specifically targetting a direction for a pre-arranged sked, the linked dipole normally gets used.

73 Ed.

As the weather should stay good here at least until Wednesday and I’m hoping the current CME strike will have finished by then, I intend going down to DL/AM-001 Peissenberg on Wednesday from 0930 UTC to do a 20m SSB activation, to both try for a VK contact and to try out the speech compressor. I’ll wecome any reports.
I now have my unit set the same as Paul’s as a starting point.

73 Ed.

UPDATE: I carried out my activation as planned today (8/1) but with the band (20m) all over the place this morning, I did not have a contact at a constant signal level, where I could try out the speech compressor. It may or may not be relevant but when I had the speech compressor in circuit, I got no replies to my CQ’s. When I had the standard microphone and no speech compressor in, most of the time I also got no replies but the only replies I did get, I got when I was just using the standard microphone and no speech processor. So the speech processor could have been making the audio un-readable but I can’t say that for sure.

I had a total of nine contacts in one hour with the longest being to John @ZL1BYZ in New Zealand. Thanks John !

During my activation of EA2/NV-092 yesterday afternoon, I managed to ask for modulation reports and got comparative reports from 3 stations in EA of my transmission with and without the Speech Processor (SP).
The reports were given while I was transmitting on 40m band LSB with 5 W into an inverted vee endfed wire about 21.5 m long with its appex about 7m high. Since the antenna was endfed and there was a very short length of coax (less than 1m) from the 9:1 unun to the FT-817ND, I was speaking really close to the antenna wire,so the distance from the Speech Processor unit and the hand mike to the antenna wire was about 1m or possibly less.
Nobody reported RFI problems either with or without the SP connected. However, 3 different chasers told me they were copying me better with the SP OFF :astonished:
One of these 3 chasers said that not only the quality of my audio was better without the SP, but also the signal on the S-meter was stronger without SP
A second chaser, right after this first, subscribed what the first one had said and finally a third chaser said he could copy me nothing with the SP ON and perfectly OK with the SP OFF.
The pile up was huge and the temperature too low to spend more time asking for reports and doing other tests, so I just left the SP OFF and kept working the pileup.
I have checked the SSB MIC gain in my FT-817ND (menu #46) and it’s 90. Is this too much? I don’t know. I think that’s something I’ve never changed since I bought 2nd hand the rig back in 2009 or so…
The 2 tunable trimmers inside the SP box are like this. Again, I’ve never changed them:
These reports were really a surprise because it’s just the contrary of what Jorge EA2LU told me when we made our first test in a local QSO on 10m SSB a few days ago.
We’ll have to investigate this further and run some more tests.
Problem is that being in a summit in winter is not the most attractive test lab I can think of…


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I have 55 so.
For 90 I would need to keep the mike half a meter away I guess.

73 Joe

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I’ll echo what Joe says, when I had my FT-817 the SSB Mic gain setting was between 50 and 55 - 90 is too much. I presume you are using the standard MH31 microphone.

On my side, In my activation yesterday I proved that the RFI problem is nothing to do with the DYC-817 as I was getting the problem without the compressor connected and the problem (raspy audio) went away when I turned the 50-70w amplifier off. I have now added clip on ferrites and about to do some “cable surgery” to hopefully fix the pick-up. Once I have done that, I can go back to testing the compressor!

I am surprised that you have worse reports with the compressor turned on than off Guru. Try turning down the internal Mic gain inside the FT-817 and make sure, first, that all is still OK without the compressor in circuit. What I am wondering is if the internal gain is so high, perhaps the microphone insert in the MH-31 isn’t working as well as it should be and might need replacing?

Is the switch on the back of the MH31 on “1” or “2”? One setting is supposed to give a more “rounded” - aka ragchewing audio - I think that’s “2” if I remember correctly. For our use it should be on the communications quality setting.

73 Ed.

I will just add to this conversation that in my limited experience not all MH-31 microphones are the same. I have had an FT-817 and FT-817ND where the microphone sounded great, and an FT-857 where the MH-31 microphone sounded awful. I did some experimenting with that one by replacing the element with a dynamic type, but it never worked satisfactorily and I ended up buying the DTMF microphone instead.

Has anyone else experienced this?

With reference to the switch on the back of the MH-31, the ‘2’ position I have read is recommended those speaking English as it has slightly more punch, a reduced bandwidth. The ‘1’ setting is for languages where a larger dynamic range is required to fully understand vowel sounds.


Radio mic gain 50 is about right. Pretty much all reports of bad audio are associated with high common mode currents due to poorly balanced antenna systems. Also audio tests are best done when the distant station is receiving you relatively weakly.

Hi all,
As I said, the reports I got during my last activation surprised me so much for being totally in opposition to what I previously had received from Jorge EA2LU in a local QSO on 10m, that I really want to repeat the tests ASAP.
I agree that testing with a local station is not the best and a distant station not receiving me S9+++ would surely be better.
Since testing from a SOTA summit is not very comfortable in these winter days and running my FT-817 at 5W from home with the endfed wire in the balcony, I may not reach to many of you with a good enough signal, I’ve thought that it might possibly be a good idea to arrange a testing session through the Hack Green SDR, as all we need is reaching that station and many of us can be listening and giving real time reports through this thread on the Reflector. All we should do is finding a good frequency and time in the day when the ham willing to test his Speech Processor can get to the Hack Green SDR with a decent signal.
Also, -correct me if I’m wrong- I believe the Hack Green SDR offers the possibility to make recordings, so we may be able to run the tests ourselves without even needing another ham listening to give us a report and we could do it ourselves by recording our transmission and then playing it back.
What do you think about this?


Morning Guru

Yes, I’ve used the recording facility many times on Hack Green for the purposes of checking audio levels, compression etc. as well as recording QSOs. It works on Android mobile phones as well, although the issues with muted sound on Chrome may require you to use Firefox (that applies to the desktop version too).

Regards, Mark. M0NOM

This is a highly individual setting. In my case the mic level is much lower, about 20 nowadays.

When I got my DYC-817 I tried it out in the shack first, and set the 817 to show the ALC. When I spoke into the mic the ALC indication was enormous! I switched out the compressor and tried it again and the indication was still far too high. ALC is one of those things you set and forget, it seems that something had changed since I got the rig - which I have had for over ten years. Either the mic, the speech amp or my voice had changed. I had to turn the mic gain down from 40 to 20 to get the proper ALC indication. There is no doubt that in recent years I had been overmodulating the rig, up to a certain point that is not too bad as running with the ALC a little high can simulate using a speech compressor, too high and your signal becomes antisocial, even at QRP! Anyway, to cut to the chase, I found no feedback problems.

One other point: on the Sotabeams site it mentions that the DYC-817 can be used with the FT-857. In fact the FT-857 already has an effective speech processor built into it, it is another of those “set and forget” facilities. I shudder to think what would happen if somebody tried the DYC-817 in their 857 without disabling the internal compressor, but in any case there would be no point as I tried comparing the two and there was no benefit in using the DYC-817 instead of the internal compressor. Mine will stay permanently on the 817.

Yes it does. Your comments apply to the FT-857D but not the earlier FT-857 I think? Happy to be proved wrong.

You may be right, Richard, I’ve never used the plain 857. I know they added the TXCO and DSP (plus the American 60m frequencies I believe) to the 857D but can find nothing about the compressor.

Hi Ed,
It sounded like your audio was still slightly raspy when I worked you on DL/AM-176 yesterday morning.
You were certainly intelligible and the processing probably added some punch but it didn’t quite sound perfect to me.
Sorry I hadn’t seen this thread or I’d have made a recording.
73 Gareth G0MFR

I have the SSB Mic set to 80 on both my 817s. As I wrote before, I played with the settings to get the most punchy audio before I bought my DYC-817. Using the DYC-817 unmodified resulted in reports of unintelligible audio so I knew something needed tweeking but it didn’t get done for some time. Listening on one radio with headphones and txing to a dummy load on a different radio, I adjusted the DYC-817 mic gain pot for best sounding audio. The effect is obvious on the 817’s meters and when listening. Then I backed the gain off a smidgeon. Reports after setting up from distant users say it’s better with than without. Could it be set better, well maybe. But in use it shows an improvement.

Looking through my logs I have about 5000 SSB QSOs with the 817 mic wound up to 80 and I’ve never received bad audio reports and about 400 SSB QSOs with adjusted DYC in use and no bad audio reports.

I have left the 817 SSB MIC at 80 as my DYC doesn’t like 80m RF. So with the DYC out of circuit I’m back to what worked fine 5000 times before. I should fix the RF pickup but don’t have the time.

Could it be better? Possibly.
Is it an improvement and worthwhile at these settings? Definitely.
Do you need to do a check on TX audio before using one? Absolutely.

Hi Gareth,
I was not using the speech compressor on DL/AM-176 yesterday. I was running around 70 watts PEP on 40m though and the RF from that was getting into the rigs audio (I think I now know how and am working on a fix). The PTT switching line for the amplifier comes from the accessory socket on my X108G which also has an auxilary audio input pin (used for data modes). As I re-used an old PS/2 keyboard cable, I was effectively putting a 1 metre antenna on that audio input and laying it right next to the amplifier !! I’ll be doing some “surgery” on that cable this afternoon!
Once I have the RF ingres problem cured, I’ll be testing the compressor again. The X108G already has an internal audio compressor (which is turned off) but anything over 2 on its 1-10 scale, it sounds horrible, hence the idea to use an external dynamic compressor instead.
73 Ed.

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I found a short term solution to the RF getting into the rig’s audio. I swapped the short link cable and the mic curly cord and the problem went away. This does mean the speech compressor is dangling just below the mic, but at least I have been able to use the compressor. As to a permanent solution to the RF issue, I suspect a lightweight metal box and a screened mic cable might be required. Something else to look at!

73, Gerald

Good thinking, Gerald. I just tried it and the dangling compressor doesn’t seem to be an annoyance, so if I ever get the problem I shall try that.

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Hi all,
I have just finished testing and tuning my DYC-817+FT-817ND.
I transmitted with 500mW into the endfed wire at the balcony and received with my IC-706MKIIG with no antenna at the shack. I was listening to my own modulation being received by the IC-706 on my AKG K240DF Studio-Monitor headphones.
There was a problem of too much mic gain on the FT-817, which was fine for use with the standard microphone alone, but it entered, at some point, in conflict with the Speech Compressor.
I reduced MIC SSB value on the FT-817ND from 90 down to 20 and then increased it up to 30, 40 and finally 50. I also had to slightly reduce the level of compression by tuning one of the Speech Compressor trimmers to avoid some audio interruptions I was experiencing while counting numbers, more precisely after pronouncing certain sounds, like the S at the end of DOS = number 2 in Spanish and TRES = number 3 in Spanish.
The modulation is definitely more punchy with the Speech Compressor ON.
After this tunning made while transmitting with 500mW, I switched to 5W and noticed that the output power peaks got higher with the Speech Compressor ON.
I think it’s got much better now and I’ll try to run a new comparison test with and without compressor during my next activation. Not today because it’s raining here…
That’s all folks!

P.D. after many times switching between positions 1 and 2 in the switch at the back of the standard FT-817 microphone, I must admit that I almost don’t see any difference. Perhaps, my voice gets less bass and more treble sound on position 1, but it’s been really difficult (rather impossible) for me to appreciate a substantial difference.

Hi Guru,
I’m glad to hear of your success with the dynamic compressor.
As for 1 & 2 switch positions on the MH-31 microphone, when I had mine originally (before building an RF-Clipper compressor into the microphone shell where the switch is then used to turn the compressor on or off) - I also could notice very little difference. If I remember correctly, all it is doing is switching in a capacitor on the audio line, so no real “rocket-science” behind that switch although some people have said it made a difference for their voices.

I have another suggestion, if you have time. If you can find a WebSDR that can hear your 5W from the FT-817 it would be good to listen to your audio with the compressor on and off through that as it will be a second test after using your local receiver.

73 Ed.