Speech Compressor for FT-817, 818 B Grade

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Speech Compressor - unleash your DX potential

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

Please Note:  these speech compressors may transmit a repeated click noise if compression is switched off and PTT is keyed but there is no audio input. The click disappears as soon as you start talking normally, or when low level audio is picked up by the mic. This means that the clicking should not present a problem in normal operation, since PTT is not usually held down for long periods while not speaking.

The clicking noise can be avoided by either:

  • Releasing PTT when not talking into the microphone.
  • Removing the speech compressor and connecting the microphone directly to the radio when you do not want to use compression, instead of turning compression off with the slide switch.

The click is typically once or twice a second, and whether it occurs or not seems to depend on the background noise level, and possibly the temperature. We have been investigating the cause, but do not yet have an ETA for when we will have some compressors that never make a clicking noise.

We are currently selling these compressors at a small discount.


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 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