Good Morning Paul,
The parts for the external 40m LP filter are provided to supplement the LP filter that is on the RXTX board so that the 40m spurious output meets the FCC requirement of -43dB, otherwise the 40m spurious output is about -40bB.
A kW transmitter at -43bB spurious output is allowed 50mW spurious output. At -40bB the 40m spurious output of a one watt RXTX board would be 0.1mW so even amplified 20 times the spurious output would only be 2mW, much below what a kW is allowed.
The external LP filter parts are included in the RXTX kit to meet the FCC -43dB requirement.
Regards,
Tony, kb9yig
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On Sep 24, 2021, at 6:23 PM, Paul Egan <paul@...> wrote:
I'm interested in the 40, 30, 20m version but wondering about the low pass filter. Is one required for each band?
I think the kit comes with parts for one filter?
Would these filters be usable if I were to add a 5w or 20w amp?
I having a hard time finding info about the rig but think I may have arrived at the right place.
Thanks.
73,
Paul VA3ZC
