Help: HW-101 Carrier Null Problem

[Stewart Lyon]

Hi Ted,
I think your Problem One is that the BFO crystals are off in frequency so
that the carrier you are trying to null out is already way down on the
slope of the filter.  It doesn't take much -- 200-300hz off  will do it.
One way to check it is too disconnect the antenna, turn the AF Gain up
and then switch back and forth between USB & LSB. The "hiss frequency"
should be about the same. If not one (or both) of the crystals is off.  I
don't have a counter so I used a Kenwood TS440 as a frequency meter --
not the most accurate but good enough.

I had this same problem in a SB-401.  The crystal (can't remember which
one) was low in frequency. It took some fancy juggling of the "colpitts"
capacitors to get the crystal upped in frequency and still oscillate.

The method you are instructed to use to measure the null is, in my view,
pretty insensitive. If you get your hands on a hi-freq scope, it makes it
a lot easier.  I have been able to reduce the carrier to a calculated -60
db this way. (1V/1mV)

As to Problem Two, I don't have an answer but I seem to remember
something in Joe Lutz's posting of  the service bulletins.

73, Stu -- W6CUX


On Wed, 6 Jan 1999 23:49:46 -0500 Ted <tlee at WCOIL.COM> writes:
>Hello to all
>
>I need some technical advice on a problem I am having with a HW-101.
>
>Problem One: I cannot get any measureable RF voltage from carrier null
>circuit.  No voltage-- no way to adjust the carrier null.  I have
>replaced the null pot twice and all the diodes in the circuit once
>with
>no results.  I have carrier oscillator injection into the balanced
>modulator at the correct frequency.  I have replaced tube V16, and
>Tube
>V1.  Don't know what to look at next.
>
>Problem Two:  I get full output with the Tune mode but when I switch
>to
>LSB or USB and key the mic I get full output using an audio generator
>for several seconds and then the RF out drops off to zero.  Voltages
>check OK in Audio circuit and do all resistances.  I have no way of
>checking capacitance--Could I have a  bad capacitor somewhere in the
>circuit??
>
>Any help would be greatly appreciate to those of you when a better
>understanding  of what is going on.
>
>73
>Ted N8GPQ

--- --- --- --- --- --- --- --- --- --- --- --- --- --
To subscribe: listserv at listserv.tempe.gov
and in body: subscribe HEATH yourfirstname yourlastname
To unsubscribe:  listserv at listserv.tempe.gov
and in body: signoff HEATH
Archives for HEATH: http://www.tempe.gov/archives
--- --- --- --- --- --- --- --- --- --- --- --- --- --