SB-401 CW Chirp problem

[Mark Graalman WB8JKR]

 Oops, I shoud have stated, the procedure I just
mentioned is outlined on page 96 of the 401 manual.

73,  Mark WB8JKR

Member ARRL, QCWA, OTC, Society of Cable Telecommunication Engineers
WAS, WAC, WTO, DXCC, GJDXCC, VUCC 2M
Novice 3/71, General 8/72, Advanced 8/79, Extra 8/89


On Sun, 29 Dec 2002 14:24:41 -0500 "Mark V. Johnson"
<mvjohn at SYMPATICO.CA> writes:
> Wondering if anyone has had problems with "Chirp" reports using  an
> SB-401/SB-301 combo. I've gotten them  (chirp reports) on 20 and 15
> meters lately and I have it narrowed down to the  Het Osc in the
> SB-301.
>
> When I listen to my signal  on another receiver while transmitting
> into
> a dummy load, I can hear the frequency shift enough to be "chirpy".
> When
> I transmit using only the SB-401 in stand alone (I have the optional
> Xtal pac) the chirp goes away.
>
> I did find that the SB-301 Het OSc adjustment has an effect. It
> seems
> that if you have the Het Osc adjustment too high, it  causes the
> chirp...Must be over driving the  transmitter. Yet, the manuals
> (SB-301/401) have you adjust the Het Osc coils in the SB-301 for
> maximum
> grid drive in transmit on teh SB-401. When I back them off and
> adjust to
> the spec's listed in the receiver (less than -3VDC at the  Het Osc
> test
> point), the chirp goes away, yet the Sb-401 grid drive is not at
> maximum.
>
> Seems these combo's (sb-301/401) are very adjustment sensitive....
>
> The Het Osc circuit in the SB-301 seems to be OK...Tube (6AB4)  is
> new
> and has good gain, voltages are to spec....The 6AW8 Het Osc amp in
> the
> SB-401 is good...Voltages are fine.......I'm using RG-62 cut to the
> proper length.....When I scope the Het Osc signal, it looks
> fine....Symmetrical Sine Wave...No crap...
>
>
> Anyone have similiar expereince??? Many Thanks!!
>
> MV Johnson VE3DJU/VE3DDI
>
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