Steve,
I would think your assumptions for the cause may be correct.
BUT -- rather than changing the XV222, I would suggest running a larger
gauge wire to the XV222 would be the easiest solution. Assuring that all
connections on the power cord are tight and with very low resistance
should help a lot.
You could change the reverse polarity protection diode to a 95SQ015
(Elecraft PN E560009) and it may help some, but I would suggest that
would be simply masking the real culprit which I suspect is voltage
drops in your power wiring.
73,
Don W3FPR
On 6/11/2013 6:58 PM, Steve Kavanagh wrote:
I got a report of chirp when running CW on 222 MHz during the VHF contest this
past weekend.
This has been confirmed by a few others since the contest. It's quite possible
that the various voltage
drops from the Rover vehicle battery to the XV222 were not leaving enough
headroom for the 78L09
local oscillator regulator. I am not sure this is the problem, but it
certainly is plausible. I am looking
at various approaches to fixing this, but I wonder if there is anything that
can be done to make the
XV222 a bit less sensitive to low voltage. For example:
(1) change the reverse polarity protection diode to something with a lower
voltage drop. The manual
says it's an SG530, for which I cannot find a data sheet....is it the same as
an SB530 by any chance ?
(2) change the regulator to an 8, 8.2 or 8.5 volt unit. All of these exist in
TO-92 format though some
are getting hard to obtain now. Would the oscillator start reliably ? Would
there be enough LO
power for the mixer ?
(3) change the regulator to a low-dropout type. I can't find any 9 volt TO-92
LDO regulators so far.
Does anybody know of a source ? I suppose a tiny SMD board could be
piggybacked....
Has anyone any specific info on these ideas or other possible mods ?
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