[AMRadio] Halli HT37 Phasing Mod problem


Gary Schafer garyschafer at comcast.net
Tue Nov 27 21:16:30 EST 2007


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.

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.

Sometimes the Rf phasing coil will have little effect when tuning it. It
depends on how tightly it is coupled to the next stage.

73
Gary  K4FMX

> -----Original Message-----
> From: amradio-bounces at mailman.qth.net [mailto:amradio-
> bounces at mailman.qth.net] On Behalf Of DOXEMF at aol.com
> Sent: Tuesday, November 27, 2007 11:59 AM
> To: amradio at mailman.qth.net
> Subject: [AMRadio] Halli HT37 Phasing Mod problem
> 
> Hello,
>  I have been trying to get this like new HT37 on the air for awhile.
>  The audio phasing modulator has been near impossible to properly ballance
> espeially using the manual instructions.
>  So far have replaced a leaky low pf brown drop silver mica
> that corrected some of the problem but still am not able to get a properly
> phased output from the modulator.
>  The audio seems ok up up to the rf stage where it won't align. The
> carrier osc is on freq ok but the carrier phasing adjustments do not work
> out.
>   Where would be a good location to apply a ballanced audio signal to
> bypass most of the original circuit?.
>   Has anyone come up with an alignment procedure using modern test gear?
> 
> Thanks,
> Bill,
> KB3DKS/1
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