Testing the DYC-817 Dynamic speech compressor

I am starting this new thread as it appears there is some interest in this plug-in Dynamic speech processor which is available either from Funkamateur (Box73.de) or SOTABeams (sotabeams.co.uk).
several of us have received (or bought ourselves) this add-in unit for Christmas 2019 and want to do two things - set it up correctly without bad distortion and take actions to resolve problems caused by RF Ingres. It is documented several places on the web that this unit is RFI susceptible especially when the operator is using an amplifier and hence emitting more than 5 watts. the expectation is that when working correctly, the average output level of the rig will be increased resulting in an (at least audible) increase of signal at the receiving end of 1 S-point or more.

The unit is primarily designed for use with the Yaesu FT-817 and 818 QRP transceivers but as the same microphone and connector is used on the 100 Watt FT-857 and FT-897 it can also be used with these.

In my case, I have cross-wired the supplied RJ-45 lead so that I can use the DYC-817 with my Xiegu X108G portable transceiver, and hence my level of success may not be the same as those using Yaesu rigs. The Xiegu has it’s own internal (audio only) compressor which I have turned off as at anything above 2 (in its 1-10 range) the audio is badly distorted. With the Xiegu, there is also no way to turn down the microphone gain in the rig, so I am using an amplified microphone with a level control built-into it (the output from the DYC could however overload the rig if it is not able to be set low enough).

As testing from the home shack is less than adequate as the problems of RF ingres and level of background noise only occur when out portable, it is proposed to test from a summit (or at least a portable location) so that all equipment as planned for a SOTA activation can be used “in-place”.

This conversation started in this other thread SANTA & SOTA - #20 by M1BUU

So far it appears the following SOTA activators/chasers have or intend to, use this unit:


Although for an earlier version of the unit - this article also mentions RF Ingres problems and suggests lining the case with metal: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=2ahUKEwjV2O_68eDmAhVN2aQKHfA9Az8QFjAEegQIARAC&url=http%3A%2F%2Fwww.mods-ham.darc.de%2F02_Mods%2FOther-Mods%2FDYC-817%2FDG2IAQ%20Modification%20Sheet%20DYC-817.pdf&usg=AOvVaw2svvKmgbcX2uPOdEqmVvkV

Of those listed above can any of you not make a work-day activation? If so it’ll have to be a week-end (which has the problem of contests). any suggestions for a date / time for the tests?

If we can draw any conclusions from our tests, I am happy to write them up and supply them to Box73, so that they can at least include them in their documentation, if they aren’t able to implement a change in design to address the problem(s).

73 Ed.


Hello Ed,

Thanks for the initiative. It would be interesting to see which versions are out there. Potentially some mods or recommendations are already implemented as the mod article is from 2004. It shows a version were no SMD parts are used.
My box states version 3.0.
PCB has DYC-817 V1803F

Here pictures:

As far a I know the 857 has a build in DSP mic compressor and adding an external might be too much.

Work-day activations are difficult for me.

My plan is to build a 1:1 balun according to Wolfgang Wippermann https://www.dg0sa.de as a middle piece to be added just after the 817 so that I can test with or without scenarios.
And I have already applied some conductive RF shielding paint for plastic cases. (Kontakt Chemie EMI 35).

73 Joe

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I’ll fetch mine and find the version number.

Before I had mine, I spent time “hot-rodding” the mic gain and other such settings on the 817 to get the most punchy audio. I’m not sure if these edits made it more necessary to alter the DYC settings or not. Anyway it was set by listening to the sent signal in the shack on headphones for best punch and least distortion. Then backed off a tadge.

On air reports show it makes a noticeable improvement.

I’ve observed no RF feedback/pickup issues using a 40/30/20 trapped EFHW (inverted L or inverted V), 60/40/30 dipole, 30/20/17 dipole all with a 5m pole. I haven’t tried it with the 30/20/17 vertical or the 12m GP.

The only time I have seen a problem was yesterday with the full sized 80m dipole where I noticed the power out on the 817 showing 3/4 output with the last segment flickering on/off when I was not speaking. At first I thought it was the circuit reacting to wind noise but a test of covering the mic didn’t stop the power indication. It only did this after talking, i.e. engage PTT and saying nothing, no output but engage PTT call CQ then stop speaking with PTT and 3/4 output shown.

Flicking the switch OFF resumed normal service.

Thanks for the link Ed… interesting mods listed. I was unaware of the off switch not being a real off.

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Hi Joe,
well mine is the current v3.0. Yes the article was based on an earlier version.

This article (which appears to be almost a direct copy of the supplied manual) http://radioaficion.com/cms/ft-818-microphone-dynamic-compressor/ states:
So the inference is that it is expected that the DYC-817 will be used with the 857 - as it points out however running both the internal sppech compressor in a rig and this external unit is not advisable.

OK on no work-day, test day - so how does the 11th. or 12th. January look to you?

73 Ed.

So mine is:

Thank you, Ed, for creating this specific thread.
As I explained in the other thread where this subject started, I already tested it at home with my FT-817 at 5W and the endfed wire antenna in the balcony. No RFI was reported during a local QSO on 10m band. Further testing will have to be done using other bands.
One other thing I’d like to try is operating from a closer to the antenna position. At the moment, my initial test was done with the radio in my current shack, which is in a room about 12-13m away from the antenna. I may prepare a short length of RG58 coax just enough to connect my FT-817 and operate it from the very balcony where my endfed antenna is currently installed or, perhaps, in my son’s bedroom, which is the closest to the antenna feedpoint place in the appartment and that would spare me from being out in the cold and I could make the fine tunning more comfortably in the warmth. This should be fully representative of a SOTA activation setup.I’ll report my findings on this thread.
Personally, I think it will be easier that we individually run our own testing and share our findings here, rather than trying to find a convenient day/time for all of us getting to a SOTA or out in the outdoors and do the testing in group, because, matching all our individual agendas, plus having a good enough WX at all of our different locations strikes me as a really difficult thing to achieve.
What do you think?


I am using my v2 (DYC-8x7 Dynamikkompressor Funkamateur FT-817) on my 817 since Jan 2016 on more than 100 summits and never had a problem. I used it a few times with the MX-P50M and also had no issues. ZL1BYZ recoreded my audio which you find here, besides a quick video of my QSO into ZL.
SOTA: DM/RP-400 Großer Adelberg - 15.10.2016 - DX mit ZL1BYZ und ZL1TZW
I worked ZL1BYZ 3 other times, only with the 817 and no amp, but always with the compressor.

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Hi John,
Nice video. I note you were operating on 20 metres, when I had the complaint of possuble RF getting into the audio, that was when I was on 40m - whether that is relevant, remains to be seen.

John ZL1BYC is usually one of, if not the first ZL SSB station to get through into Europe. I’ve also worked him several times from summits, but unfortunately not in the last year.

Listening to the recording of your audio that John sent you - what level of compression did you have the pot set to in the DYC-817? I presume you are using the standard MH-31 microphone? For my ears, it sounds just a very little muffled but without a comparison with the compressor in and out of the circuit, it’s hard to say what is the microphone and what is the compressor. It certainly sounded relatively loud.

73 Ed.

I don’t know in numbers. I transmitted into a dummy load while I was listening with headphone on my station rig without antenna connected. I adjusted until I had a propper audio.

That’s correct.

I just did a similar adjustment.
I had no other SSB radio available so I did the adjustment with my FT1xde able to receive in AM mode - of course running the 817 in AM into a dummy load.
I needed to set both potentiometers to the very left rotation. But I noticed a good difference.
Will test it in tomorrows activation under hard SOTA conditions.

73 Joe

So first activation using the DYC-817 successful. As written I have both potentiometers to the left. SSB mic gain in the menu is set to 55.
I had a brief first test during the QSO with of Lars @SA4BLM and later also Guru @EA2IF could hear the result.
Lars commented on tiny bit of overmodulation. I see the ALC kicking in faster. I will need to pay attention not to talk too loud.
Tested 20m and 17m using my vertical upper-outer-antenna.

So far so good. :+1:

73 Joe

I am using this accessory for all my SSB HF & VHF & UHF SOTA operating. Most definitely worthwhile.

Hi Joe,
Since I still can’t rotate my yagi and its permanently beaming to NA, I had to make the contact with you with my inverted vee broadband folded dipole, which serves me well but it’s, unfortunately, a zero gain, low performer antenna, so the signal I was receiving from you today was far too weak for comfortable testing and a good detailed comparison. I definitely could feel the speech processor effect in your modulation and it was good with no distorsion or any wrong things while the QSB was bringing your signal up and I was able to copy you well enough.
Thanks for the QSO and the test report here.


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This is interesting as it was also Lars who helped me with my first test of the unit, which started my search for the possible RF ingres - it would be good if Lars is available when I test again. Most likley now is Saturday 11th January - is anyone else available with this compressor also on that day, so we can make a sort of “net” to allow each of us to adjust the settings?

73 Ed.

Hi All
I have purchased the DYC-817 from Sotabeams and it as arrived today. I am activating two summits tomorrow so I will carry out a few tests and let you know how I get on.


Thanks Paul - can you let us know where you have the pots inside the unit set to please? I’ll try to be on tomorrow from the home QTH and listen for you if I see you spotted.

If propagation isn’t working well, I’ll try to hear you via a WebSDR receiver, so if you can mention when the compressor is on, and when you have it turned off, that’s be great. I’ll also see if I can make a recording.

73 Ed.

UPDATE: Your alerts say you are only going to be on 145 FM - the compressor is not meant to be used on FM! only SSB.

Hi Ed
Yes I am also taking the HF setup so will have dipole for 20/40m as well. Will only use the HF on second summit.
I have not changed any of the setting as it is pre built. I will open it up when I get back tomorrow

OK, understood, I’ll try to hear you on Cyrn-y-Brain when you are spotted.
I suspect the compression level may be set to minimum in that case - what the input level is set to, is anyones guess - possibly half way.

73 Ed.

Hi Paul,
I see I missed you when you were on 20m on your first summit Moel y Gamelin - but 20m here at that time was horrible. Here’s hoping I might hear you on your second summit.

73 Ed.

UPDATE: Saw the spots for GW/NW-043. Nothing heard on 20m. On 40m you were there for a couple of seconds before you got swamped by contest stations (also via WebSDR).

Hi Ed
I managed about 15 QSO’s between 20/40/60m with some good reports. I carried out a few tests and the chasers said that there was an improvement with the unit tuned on. As I said mine is a pre made unit supplied by Sotabeams and I have not altered any of the preset settings so a thumbs up from me.

Hi Paul,
Thanks for doing the tests.
If it’s not glued together, could you carefully open the case and report where the potentiometers are set please? My guess would be compression at minimum and input level at a middle setting but that could be a wrong assumption on my part. Then those of us who built the “kits” can set them the same as a starting point.

Can you also confirm that your set-up was without any amplifier, so just the FT-817/ND/818 at 5/6 watts? It sounds like you didn’t get any RF into the unit (which is what I believe is happening to mine and others when we use more than 5 watts).

73 Ed.