K3 going expeditionary

[Steve Hall]

I highly recommend you run a power lead to the battery (ideally) or the
main power bus in the car interior rather than tap off the limited
accessory socket.   Keep well under the fuse rating that feeds the
accessory plug if you go that route.
Steve WM6P
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

[Jim Brown-10]

Yes, and this should definitely be twisted pair, contrary to what's on a
highly regarded mobile site. Also, radio equipment in vehicles should
NOT by bonded to the frame/chassis/vehicle metal.

OTOH, coax return for HF mobile antennas SHOULD be bonded to vehicle
metal, because that's what serves as its counterpoise (often called a
ground plane).

BTW -- a major obstacle to this being a good ground plane is that the
metal parts of many (most?) vehicles are insulated from each other by
paint. An ohmmeter study between parts of the chassis is a worthwhile
effort.

73, Jim K9YC

On 8/24/2020 3:01 PM, Steve Hall wrote:

> I highly recommend you run a power lead to the battery (ideally) or the
> main power bus in the car interior rather than tap off the limited
> accessory socket.   Keep well under the fuse rating that feeds the
> accessory plug if you go that route.
> Steve WM6P
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

[Clay Autery-2]

Yup....  When I did my alternator and battery upgrade (including a
complete replacement of the power/ground cables with much heavier
cable), for my stereo install, I discovered that very thing....  even in
a TRUCK with a frame.
I mapped out and installed massive ground continuity cables from every
metal body part to the frame, and finished up by MEASURING the
resistance from point to point all over the body, bed, cab, frame, and
engine to insure that the entire ground plane was continuous and super
low resistance.

Maybe overkill, but it works great, and it gives me comfort to know that
vibration dampening and oxidation aren't compromising the counterpoise.

Side bonus, was that the 12VDC ground plane was so good afterwards, that
I have been able to take out a lot of the home run grounds from a bunch
of lights, et al... ofsetting weight gain by some bit.

73,

______________________
Clay Autery, KY5G
[phone]

On 08/24/20 17:40, Jim Brown wrote:

> Yes, and this should definitely be twisted pair, contrary to what's on
> a highly regarded mobile site. Also, radio equipment in vehicles
> should NOT by bonded to the frame/chassis/vehicle metal.
>
> OTOH, coax return for HF mobile antennas SHOULD be bonded to vehicle
> metal, because that's what serves as its counterpoise (often called a
> ground plane).
>
> BTW -- a major obstacle to this being a good ground plane is that the
> metal parts of many (most?) vehicles are insulated from each other by
> paint. An ohmmeter study between parts of the chassis is a worthwhile
> effort.
>
> 73, Jim K9YC
>
> On 8/24/2020 3:01 PM, Steve Hall wrote:
>> I highly recommend you run a power lead to the battery (ideally) or the
>> main power bus in the car interior rather than tap off the limited
>> accessory socket.   Keep well under the fuse rating that feeds the
>> accessory plug if you go that route.
>> Steve WM6P
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

[Jim Brown-10]

On 8/24/2020 8:17 PM, Clay Autery wrote:
> Side bonus, was that the 12VDC ground plane was so good afterwards, that
> I have been able to take out a lot of the home run grounds from a bunch
> of lights, et al... ofsetting weight gain by some bit.

Important fundamental concept, Clay, that I learned in an IEEE EMC
workshop. DC follows the path of least RESISTANCE. AC follows the path
of least IMPEDANCE. If there is a transmission line with, for example, a
chassis in parallel with the transmission line return, above about 1
kHz, all the return current will be in the transmission line, NOT in the
lower resistance chassis.

That's because the return patch through the chassis includes a lot of
INDUCTIVE REACTANCE, which increases in proportion to frequency, while
the path through the transmission line, if matched, never rises about Zo
of the line. The whole point of using the transmission line is to reduce
noise and crosstalk. It's only effect on DC (as compared to the chassis
path) is to slightly reduce the DCR of the return path by adding the
transmission line return in parallel. With coax, of course, the shield
is the return. Wtih 2-wire line, one conductor is the "hot" lead, the
other the return. AND -- 2-wire line and coax are no different in this
regard! The KPA500, for example, uses twisted pair for wiring from the
input coax to the amp input stage.

73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]