Speech Compressor for FT-817, 818

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Speech Compressor - unleash your DX potential

***apparent improvement can be up to 6dB!***


The FT-817 FT-818 is a great radio but the SSB speech power does lack "punch". This great little external AF dynamic compressor from Box 73 in Germany will aid readability and maximise the performance of your radio (essential when using QRP). Speech Compressors work by raising the average level of your audio signal, giving greater "talk power".

Plug and Play! Connects between the radio and microphone (lead included). The compressor function can be switched in or out, the module draws its power directly from the transceiver (approx. 10mA). The compression level is adjustable. Modifications to the microphone or transceiver are not required.

Click here for instructions. The speech compressors that we sell are fully built and ready to use, so the construction part of the instructions can be ignored, but there are some operating instructions near the end of the document. The potentiometers inside the compressor may need a bit of adjustment to suit you and your radio (page 10 of instructions).

The compressor is also suitable for use with the FT-900, FT-857, FT-897 and FT-450 (all versions).

Note: if using an external speech compressor, any internal speech compression in the transceiver should be turned off. Otherwise there will be too much compression, resulting in distorted audio.

Video: demonstration of how speech compression works



Speech compression is not recommended for use on FM.

Microphone cable

Occasionally people have problems plugging their microphone into the compressor. This is because the Yaesu microphones are fitted with an oversized rubber boot that shrouds the RJ45 connector. If the RJ45 connector does not click firmly into the body of the speech compressor, gently retract the rubber boot a few millimetres and the connector will engage properly (100% success rate!).

Video: how to fix a microphone cable that does not plug in properly


 Also available from our international agent(s):  



54 Reviews Hide Reviews Show Reviews

  • 5
    FT-818 Speech Compressor

    Posted by Steve W on 24th Feb 2024

    I have had incredible reports using this device QRP 6 watts on my FT-818. Today I was using my OCF dipole on 15 meters here in WA State and heard a station from Finland. Keep in mind, this antenna was not particularly resonant on 15 meters. no tuner and the SWR on my radio meter was about mid-scale. I estimate just north to of 2:1 SWR. I tried answering his call and was heard first time 5/3. I was floored! last week QRP from Washington State to Japan… heard 5/9 using a vertical with tuner at 6w. I love this device.

  • 5
    FT-817 Speech Compressor

    Posted by Mike on 13th Nov 2020

    This is an outstanding product. I highly recommend this to anyone trying to make SSB contacts with the 817 or 818.

  • 5
    speech compressor

    Posted by Steve on 4th Apr 2020

    Easy to build works great .

  • 5
    Great so far

    Posted by james roff on 17th Jan 2020

    Purchased after looking at many options on the internet and for overall price I went for this. Definitely notice the improvement in voice level and has made an improvement to my qrp 2m activity just an 818 2 element Yagi about 4m above ground.

  • 5
    Speech Compressor for FT-817, 818

    Posted by Wayne Montague on 4th Dec 2019

    Item shipped quickly to Canada. The build involved 2 pots, 2 sockets and a large SMD capacitor. The only thing to really pay attention to is to put the pots in the right place. Plugged the completed assemby into the FT-817 and the difference between IN and OUT was obvious. The "tune" feature is a really nice touch. It gets a 5 for value, fast shipping, ease of assembly and working as advertised.

  • 5

    Posted by Albert on 3rd Nov 2019

    great product to combine with the original 817 microphone in ssb I always had excellent reports

  • 4
    Speech compressor

    Posted by Victor on 1st Nov 2019

    Works well. Only problem was a loose connection from microphone. Only solution was to use a rubber band. [Admin: thanks for your review. I suspect that your microphone is not locking in properly. Retract the rubber boot on the mic connector and all will be well.]

  • 4
    +1 S unit at least

    Posted by oh1bpp on 24th Oct 2019

    Product keeps what is promised, much better reports keep coming and audio is better. Only negative thing was that in the kit version, in the box the holes for mic cables were too tight and I had to enlarge those. Too tight holes resluted in loose mic connection and nothing happened when I pushed the PTT

  • 1
    I didn't know it was a kit. So I am disapointed. I have not yet soldered it

    Posted by JULIEN LE TALBODEC on 23rd Oct 2019

    Why you didn't say before bying that the product was a kit one, [Admin-thanks for your review. We sell the processor as a kit or a built unit. You selected the kit option - so that was what we sent. Feel free to return it to exchange for a built unit if you wish.]

  • 5
    I love it

    Posted by Frank Leon on 22nd Oct 2019

    It gives me more 6db with my modified MH-31 mike! I always work from the field with QRP. SSB now is a great fun! The local delivery company is not the best, but Aaron from the Sotabeams customer service helped me as quicly as possible to find my parcel. Great job, thanks!