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Chirp with K2/XV222

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Steve Kavanagh

Chirp with K2/XV222

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 ?

73,
Steve VE3SMA
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Don Wilhelm-4

Re: 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 ?
>

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Steve Kavanagh

Re: Chirp with K2/XV222

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 <[hidden email]>
To: Steve Kavanagh <[hidden email]>
Cc: "[hidden email]" <[hidden email]>
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:

Steve Kavanagh

Chirp with K2/XV222 - Fuseholder Issues

In reply to this post by Don Wilhelm-4

It looks like one of the causes of my chirp on 222 MHz with the K2/XV222 combo was
an unreliable fuseholder (an in-line type for an AGC/3AG/1-1/4x1/4 inch fuse). I wonder
if automotive blade type fuses/holders might be more reliable as far as contact resistance
goes. Does anyone have any good knowledge on this ?

73,
Steve VE3SMA
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Steve Kavanagh

Re: Chirp with K2/XV222 - Transverter Issues

In reply to this post by Don Wilhelm-4

Thanks for your comments, Ron. My fuseholder isn't gradually melting....it's a pretty robust one and teh spring effect is fine, but small contact area and dissimilar metals appears to be the issue. It seems like the automotive blade fuses are the wave of the future in ham radio !

73,
Steve VE3SMA
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