Re: Is push pull hf amp has higher spectral purity
Brian,toggle quoted message. . .
They were all busy looking at the harmonics, didn't think to check for that close in spur.
Would be interesting to see how strong it is on other rigs.
I believe the strength of the spur comes down to how strong that 4'th harmonic of the VFO is.
During transmit, the VFO mixes in after the signal passes through the crystal filter,
so a lousy crystal filter is not contributing to the spur.
Lesson learned: Use high side local oscillators wherever possible.
On Thu, Dec 6, 2018 at 02:56 PM, Brian wrote:
From memory, I measured the spur to be 35dB down on the 7.15MHz signal. Nobody else reported measuring it which surprised me since quite a bit was written about modding the LPF to meet fcc on harmonics.