Re: Are these output watt rating crazy?

 

Jerry Gaffke
Apr 25  
The 80m LPF is also used for 60m, so the cut-toff freq is high enough to pass the third harmonic of 160m.This is not a sine wave:    https://groups.io/g/BITX20/message/48122
Hi,

I just entered the lowest ubitx LFP into a filter program and see that it is actually a 40m LPF.  It has a pretty good cutoff, so it cuts off what it need to for 60m and 80m, but would do almost nothing for 160m as it won't cutoff anything until the 4th harmonic and will only do about a 13dB cut there so not really effective until the 5th harmonic.  So basically useless on 160m.

Besides that, the input impedance to the filter on 160m comes out to about 10 ohms so not what the PA is designed to see.  On 60m it shows as 20 ohms a little better, but not great.

73,


Mark.

 

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