|[AMRadio] Halli HT37 Phasing Mod problem|
DOXEMF at aol.com
DOXEMF at aol.com
Tue Nov 27 23:04:54 EST 2007
"Gary Schafer" writes:
>If you are trying to align it using a tone and looking for a flat response on the scope and you have any hum in the circuit you will never get it aligned. Hum can come from poor filter caps in the power supply or audio leads picking it up.<
Yep, I was following the alignment recommendation of 1KC test tone and was gettinh some hum from a possible ground loop with the signal gen. I believe the supply caps are OK but should replace them anyway. Did replace the one inside the modulator. Might have a HK leakage problem in one of the tubes also.
>The best way that I have found to align phasing rigs is to talk into the mike while listening to the opposite side band and tune things for minimum (best side band suppression). A nice long ooooooh works good. You will need to switch side bands and do the same on the other as they interact. You can
>tune it for really great suppression on one side band while the other one won't be so great.
>Find the point where the suppression is nearly equal on each side band while listening to the opposite side.<
I will try that. Just have to get my primary receiver repaired and setup in the new shack. Been using a RS DX 390 for easy listening but the plastic case lets in too much RF from the open transmitter chassis. It would have to be in the next room to not be overloaded. I will be using AM mode primarily but would also like it to sound good and operate properly on SSB.
>Sometimes the Rf phasing coil will have little effect when tuning it. It depends on how tightly it is coupled to the next stage.<
That is what I thought might be the case since the output actually looks ok in DSB at some points of alignment. Will wrestle with it some more in the coming weeks.
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