[SignalOne] Low pass filter

[Ulrich Graf]

Hello Signal/One enthusiasts,

last weekend I had a discussion with my friend about signal/one
technologies. Therefor he presented me two 1030 milspecs out of his
s/1 collection. These radios were supplied with the computer control
board upon the receiver compartment. The transmit/receive relay and
the directional coupler were mounted on a small pcb besides the
antenna connector. The compartment of the standard board for transmit
low pass filtering and transmit/receive switching was empty. We could
not find any substitute board with low pass filter components. A brief
measurement of harmonics suppression showed values of more than 40 dB
for 7-MHz-signals. Since the pa is a push-pull arrangement the third
harmonic should be down not more than typically about 10 dB w/o lp
filter. So where is the filtering accomplished? Any hint?

vy 73

Uli, DK4SX