[Elecraft] KXPA100 Mobile Operations -- Power Output

[Matt Zilmer]

Thanks, Jim.  Many of us will benefit from your thoughts.  When the
time comes to make a permanent installation with the KXPA100, I'll be
sure and re-read your email.  

I already have the KX3 set up in the mobile.  It is working fine, but
antenna efficiency isn't very good with the Hustler type.  The amp
will give a good boost to output.  Receiving is already pretty good
due to the KX3's performance.

73,
matt W6NIA

On Sun, 12 Jan 2014 10:57:14 -0800, you wrote:

>On 1/12/2014 10:26 AM, Matt Zilmer wrote:
>> Wiring to the
>> KXPA100 is 8 AWG, with two "transfers" to APPs at a relay enclosure
>> for power control in the trunk.  The source is the Civic's battery.
>> The KXPA is located in the trunk.
>
>Several thoughts about this. First, noise pickup on the power wiring 
>will be greatly reduced by making it twisted pair. Second, unless the 
>SWR is REALLY high, much less power will be lost in coax than in the DC 
>wiring. Third, ALL of this wiring should have common mode chokes on it 
>to further minimize noise pickup and RFI.
>
>My strategy would be to locate the amp based on convenience, on making 
>the DC cable shorter, and on the practicality of paths for routing the 
>needed wiring.
>
>I would use the best quality coax I could fit into the available wiring 
>routes. This is an application for the best quality transmitting coax 
>with a heavy copper braid shield.  Remember that the shielding provided 
>by coax depends upon a shield that has very low resistance and very good 
>uniformity.  Belden 9258 would be a great choice -- it's a RG8X form 
>factor (0.242-in o.d.), with #16 stranded copper center and a 95% copper 
>braid shield.
>
>Finally, there is probably little benefit to bonding the radio or the 
>amp to the frame of the vehicle. Thanks to the excessive application of 
>paint and the use of lots of non-metallic parts, chassis bonding of 
>modern vehicles is flaky at best, and a train wreck at worst (it is in 
>my 2006 Toyota big SUV). Indeed, one of the major challenges in a modern 
>vehicle is finding enough conductive structure to form a counterpoise 
>for an HF antenna.
>
>73, Jim K9YC
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