2 • BX-8x7
© Box 73 Amateurfunkservice GmbH 2014
The kit for this dynamic compressor was
originally introduced in [1] based on an
idea of Phil Salas, AD5X. It was develo-
ped especially for the FT-817, but can al-
so be used for other transceivers with the
same microphone interface, such as the
FT-857, FT-897 or FT-900.
The dynamic compressor is plugged in
between the microphone and the transcei-
ver. It does not require a separate power
supply, and can be switched on or off as
needed. No modifications to the original
microphone or to the transceiver are re-
quired.
The integral AF tone generator, which fa-
cilitates antenna tuning in SSB mode, can
be keyed via two existing buttons on the
microphone. As a result, the general prac-
tice of whistling for tuning is no longer re-
quired.
With the exception of one tantalum capa-
citor, the SMD components are preassem-
bled. Only a few wired components re-
main; these can be easily installed even by
less experienced builders.
Construction Manual for
Dynamic Compressor V2.0 for FT-8x7
When transmitting SSB, a dynamic compressor increases average trans-
mitted power, and thus the audibility of a weak signal at the distant re-
ceiver, 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.
