Re: 80 Meters Harmonics Fix Proposal

Warren Allgyer <allgyer@...>
 

Howard

When I measured 80 meter harmonics the particularly troublesome ones were 5th at 18 MHz and 7th at 25 MHz. In both cases the attenuation of the stock uBitx at those frequencies was limited by the layout of the board and by the coupling of relays sharing both filter input and output in the same frame. In such cases the characteristics of the filters, both existing and any modifications are immaterial. The attenuation of the stock filter supplied is more than adequate. But the harmonics bypass the filter and go via I/O coupling straight to the output. Please measure the 5th and 7th harmonics on CW. I think you will find you have not done much to improve the stock situation.

WA8TOD

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