Same stage gains mentioned in dB found here on the homebrew UBITX receiver where I measured each 50 ohm block separately with a 50 ohm termination, except that I¡¯m using a 45 MHz LC filter with 3-4 dB loss. ?
But not having built anything until a couple years ago I¡¯m very sympathetic to trying to measure each stage correctly until you get good at using whatever tools you have, and how hard it is to measure the sub¡ª80 dBm levels. ?Having a standard like the old 3 band Elecraft 1 and 50 microvolt standard is a big time saver for deciding whether or ?not the system is good/not good.
You¡¯re getting a lot of good advice if you can do those measurements.
Good luck. Scott Ka9p
Make something good happen!
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On Dec 22, 2018, at 11:01 PM, jim via Groups.Io <
ab7vf@...> wrote:
Frankly, I would not mind seeing other measurements ...at least to form SOME sort of baseline ...As I said ...Quick and dirty
Don't like 'em ..delete 'em ....Measure your own and share There has been a whole LOT of theory/smoke and mirrors/hand-waving and just plain (imho) bs bandied about ....But DO provide some sort of REFERENCE ...Top o' audio pot was easy-peasy and very low bandwidth
Jim
On Saturday, December 22, 2018, 6:17:58 PM PST, Jerry Gaffke via Groups.Io <
jgaffke@...> wrote:
Assuming your signal generator can correctly inject the levels shown in the chart,
you should get rational results here regardless of the different frequencies.
Namely,?
? Perhaps 1 or 2 dB loss through the LPF at L1,2,3,4
? 6dB through the mixers
? Maybe 3 or 4 dB through the two crystal filters
? And around 10 or 12 dB through the 45mhz amp, 16dB through the 12mhz amp.
I do like the way you went about the measurements though,
looking only at the audio with the scope means just about any scope could be used there.
Or perhaps a diode peak detector and a dc voltmeter.
The signal generator could be an si5351 driving a step attenuator.
Jerry
On Sat, Dec 22, 2018 at 05:51 PM, jim wrote:
different frequencies ....
?
