How to make the FT-817 Contest Friendly with a BX-8×7

If you are working CW the narrow filter is a must and the SSB filter can help with helping he front end deal with the kilowatters but how does one get heard?

The BX-8×7 : Dynamic Compressor kit V2.0 for FT-8×7  is an Easy to build external Dynamic Compressor designed by a german ham and  is ideal for QRP operators

It is especially for the Yaesu FT-817, but can also be used for other transceivers with the same microphone interface such as the FT-857, FT-897 or FT-900.

When transmitting SSB, dynamic compressor increases average transmitted power, and thus the audibility of a weak signal at the distant receiver, by at least one S-unit. This accessory is of special interest to amateur radio operators who work with lower transmitting power or wish to be better heard in a pile-up.

Check the link out for an audio sample from a real QSO

MP3 file with two CQ calls during a summer thunderstorm situation. First call made without compressor, the second with the compressor turned on.


Based on SSM2165 (Analog Devices)
PCB with all SMD parts preassembled.
Powered over RJ45 cable (10 mA), no power supply or battery required.

The build time is less than 2  hours and makes an excellent addition to your 817 kit. I have taken a scope to the radio and can confirm it does add about an S unit to your talk power by use of the compressor




  1. Andrew VK1AD · March 17, 2017

    I purchased the kit in 2016. Brilliant, works exactly as described and no RF feedback in to the microphone line. 🙂

    73, Andrew VK1AD

    Liked by 1 person

  2. ve3ips · March 17, 2017

    I can assure you Andrew that the Australians are ahead of the adoption curve over the canadians


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