SB-401 CW Chirp problem

[Mark Graalman WB8JKR]

 Mark,

 You do not adjust the coils for maximum grid drive, you
adjust the coils for a .5 ma (midscale) reading on the
401 grid meter with the drive level control at 12:00


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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