[AMRadio] Halli HT37 Phasing Mod problem

jeremy-ca km1h at jeremy.mv.com
Wed Nov 28 09:27:12 EST 2007

Ive owned many phasing rigs starting with a HB W2EWL, all the Central 
Electronics, and a pair of HT-37's.

While a single tone can be used to get a good indicated null it is only at 
that one frequency. It is better to use two tones. If that isnt possible 
then use a tape loop or digital recorder with a fairly flat speech 
recording. Something recorded off the BCB with good AVC works well. Then 
adjust and make sure the high frequencies are suppressed as well as the low.


----- Original Message ----- 
From: <ne1s at neandertech.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Wednesday, November 28, 2007 8:49 AM
Subject: RE: [AMRadio] Halli HT37 Phasing Mod problem

> ----- Original Message -----
> Subject: RE: [AMRadio] Halli HT37 Phasing Mod problem
> Date: Tue, November 27, 2007 21:16
> From: "Gary Schafer" <garyschafer at comcast.net>
>> 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.
> Never owned an HT-37, but have played with various other phasing-type
> rigs, one of them home-grown (by me).
> Here's a few more ideas:
> Use your scope to trace a "Lissijous figure" - in this case a circle - to
> dial in the correct phase and amplitude relationship between the two
> quadrature audio channels. You'll wand to feed a sine wave into the audio
> input of the rig for this; a 1Kc tone should work OK. Make sure you don't
> overdrive the audio stages! Also, with the same setup, you can use a
> selective receiver (something with a bandpass of 500Kc/s or less) to sift
> out the lower sideband (1 KHz below the transmit (virtual) carrier
> frequency), carrier (which should be very weak, but probably audible)),
> and the upper sideband.(1 KHz above the carrier freq.). Tune in the
> sideband you want to suppress and null it out. Then tune in the opposite
> sideband, select the other sideband on the transmitter, and do the same.
> There will be a compromise between ultimate opposite sideband suppression
> and getting the best suppression possible for both USB and LSB operation.
> I've never used the Lissajous figure method myself, but it makes sense it
> should work. I've used the 2nd method several times.
> 73/GL,
> -Larry/NE1S
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