[AMRadio] Any Halli SX140 experts out there?

[Charlie Cheney]

A pure sine wave has no harmonics. Don't you need a square wave for a 
calibrator signal?

73, Charlie K1LDZ

On 6/1/2021 11:11 AM, CL in NC via AMRadio wrote:
> The Halli SX140 hamband only RX used a 3.5MC crystal for a calibrator, a totally useless idea except to set the bottom edge of the bands, that would still be out on the top edge.  First I tried an off the shelf solid state calibrator selectable from 25 Khz to 1 Mhz, handy since it would run off of 6.3VAC with onboard rect/filter/regulator, it was so dirty, you could not find which note to use out of the forest of signals.  Then I modified the receivers calibrator to run with a 100K crystal, nice clean sine wave, cannot hear it but a couple spots on one or two bands.  Tried my sig gen on 100K same thing as the homebrew calibrator, the signal was unreadable except one or two spots, you might hear it on 3.5, but not on 3.6 and up the band.  Some bands, at 0 DBM out of the sig gen, no harmonic could be heard.   The calibrator is coupled only via the proximity of the oscillator triode in the dual section of the 6AZ8, where the  pentode half is the RF amp.  I tried a gimmic cap to the antenna, did not help.  I'm thinking the untuned output of the RF amp is actually acting like a short to the 100K and its harmonics, the fixed value inductors operating more like RF chokes, effective on the hambands, but a short at 100K killing any useful signals.
>
> When I put a 3.5MC crystal in the Halli as specified, I get a good note on the bottom of each band, but it is already aligned such that the bottom of all the bands are fine, it is the rest that needs the calibrator.
>
> Charlie, W4MEC in NC
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