[Elecraft] Chirp with K2/XV222

[Steve Kavanagh]

Thanks, Don.  That diode looks very interesting indeed.  It might be worth getting a bunch for various projects ! The
wiring/switching/fusing is definitely going to get a going over, too.  Some of it is amenable to improvement for sure.  
 
But I suspect it will take a number of little steps unless I just bite the bullet and get a battery voltage booster such as the
ones made by TG Electronics, MFJ and others (or figure out how to make one).
 
Some experiments are in order before deciding what to do.
 
73,
Steve VE3SMA


----- Original Message -----
From: Don Wilhelm <w3fpr at embarqmail.com>
To: Steve Kavanagh <skavanagh72 at yahoo.ca>
Cc: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
Sent: Tuesday, June 11, 2013 7:14:40 PM
Subject: Re: [Elecraft] Chirp with K2/XV222

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 ?
>