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Testing the DYC-817 Dynamic speech compressor

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.

Hi Ed,
Yes, I’d like to do that test, but it will have to be some other day later. Difficult during the weekend, I’m afraid, and I’ll be entering to the hospital on Monday morning for my so long time expected surgery on Tuesday. It looks like I’ll finally get rid of my rectum cancerous tumour, so I’ll be quite in a “limp mode” for a while. After Tuesday operation I’ll try to show up here in the Reflector ASAP so you all will know I’m alive and kicking.



Good luck with the Op Guru.

Remember, the recovery is a lot quicker if you don’t start doing things before you should!

73 Ed.

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Best wishes for the operation next week Guru. I hope and pray that it will be a complete success and that you recover quickly.

73, Gerald

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Hi all
My 817 option 46 is set at 50 and my SP seams to work great


My good wishes for a fast recovery, Guru.

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Mine too.

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Best wishes Guru

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Best wishes, Guru…Cu soon!
73 Fabio, IK2LEY

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Best wishes Guru!!


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Hi Ed
The tests I’ve done here make a very substantial difference to the transmitted audio and to the average power level.

Is the dc supply from your radio the same as the design voltage?
Andrew VK1DA/VK2UH

I think Andrew raises a good point - is the DYC-817 seeing +5VDC? If you have access to an oscilloscope, it’s a very simple circuit, basically one transistor, two trimmers and an SSM 2165 IC, whose data sheet is online. You should be able to easily confirm the input and output audio waveforms after confirming the IC has proper dc power. Note that trimmer P4 sets the compression ratio so it’s possible the compression level is set low.

I was very impressed with the DYC-817 back when I used it with my FT-817 seven years ago.

73, Barry N1EU