[Elecraft] KPA500 Coax size requirements

Tue Aug 20 17:35:49 EDT 2019

And since I have my KAT500 and KPA500 and K3S all on the desk within 
easy reach and view, and all interfaced with the ACC buss, thus keeping 
leads short and using one common supply makes lots of sense to me, and 
many less issues to deal with.

I've told many folks,  with the system as configured, I have a 500 watt 
transceiver and an antenna system that is effectively flat from 160M 
through 6M.   All I do is change RX frequency on the K3S and every thing 
else follows.  No RF required to switch things to the correct 
configuration for band, frequency and antenna.

As to manual revisions, I see mine is C5, March 31, 2015.   My KAT500 is 
s/n 1807 purchased  7/21/18.   I haven't kept up with paper revisions.   
However I have firmware 1.075 in the KAT500 and 5.67 in my K3S.  Looks 
like all of that is up to date.

73

Bob, K4TAX

On 8/20/2019 4:21 PM, Mark Musick wrote:
> Yes Bob the manual says that, but that statement in the manual was not revised after the 4.9x firmware update.
> If you look at the manual revisions, that wording has been in the manual since the problem was initially discovered and before the 4.9x firmware update.
>
> 73,
> Mark, WB9CIF
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Bob McGraw K4TAX
> Sent: Tuesday, August 20, 2019 21:11
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] KPA500 Coax size requirements
>
> Because in the manual, page 4, item 2 states "Connect to the station 11 to 15 VDC power supply with the white striped lead to the positive terminal."
>
> I view it best to always follow the manufactures instructions and not re-engineer the product or rewrite the manual.
>
> 73
>
> Bob, K4TAX
>
>
> On 8/20/2019 3:27 PM, Ken K6MR wrote:
>> "The KAT500 can be {should be} powered from the radio 12V supply."
>>
>>
>>
>> Interested why this is true.  Can the KAT500 tell the difference between Elecraft 12V and Generic 12V?  Seems odd.
>>
>>
>>
>> I ran two KAT500s on generic 12V from a DIN rail power supply for 5 years.  Necessary because the tuners and the amps were remoted in a closet 20 feet from the operating desk.  No problems.
>>
>>
>>
>> Ken K6MR
>>
>>
>>
>>
>>
>> ________________________________
>> From: elecraft-bounces at mailman.qth.net
>> <elecraft-bounces at mailman.qth.net> on behalf of Bob McGraw K4TAX
>> <rmcgraw at blomand.net>
>> Sent: Tuesday, August 20, 2019 12:59:11 PM
>> To: elecraft at mailman.qth.net <elecraft at mailman.qth.net>
>> Subject: Re: [Elecraft] KPA500 Coax size requirements
>>
>> Carter:
>>
>> The KAT500 can be {should be} powered from the radio 12V supply.   I
>> don't suggest a separate wall wart.
>>
>> The KPA500 can be powered from either 120VAC or 240VAC, your choice.
>> It should drive on all bands with 20 to 30 watts output from the K2 to
>> reach full 500 watts output from the amp.
>>
>> As to coax, yes RG-8X is OK up to 30 MHz as long as the SWR is low.
>> The Belden Power rating is 1000 watts up to 10 MHz, 370 watts at 50 MHz.
>> Loss is 0.9dB / 100 ft @ 10 MHz and 2.1 dB / 100 ft at 50 MHz.   These
>> power ratings are matched conditions.
>>
>> What is the SWR on your wire loop on the feed line for all bands?   Per
>> Belden, the UL voltage rating is 300 V RMS.  Thus 500 watts at 50
>> ohms, i.e. 1:1 SWR, is 158 volts.  However, 500 watts into 500 ohms,
>> i.e. 10:1 SWR, is 500 volts.  So to answer your question, YES and NO,
>> depending on SWR on the coax between the tuner output and the loop antenna feed point.
>>
>> In general, R-8X is OK at 500 watts below 30 MHz.   From experience, it
>> will get "warm" to the touch.  "Warm" is created by loss which is then
>> heat generated from RF.  And that is RF which is not getting to the
>> antenna.
>>
>> Personally I'd opt for a balanced open wire feed to the loop and a
>> very good 1:1 balun rated for legal limit or more at the KAT500 tuner output.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>> On 8/20/2019 2:11 PM, Carter Craigie wrote:
>>> Hello friends,
>>>
>>> I am contemplating buying a KPA500 amplifier/tuner Combo, and driving
>>> it from my Elecraft K2/100 rig. I hope I would be able to do that!
>>>
>>>     From what I have read on eHam Reviews, it appears that I can run
>>> the amp/tuner combo on 117v. from the convenient wall socket. Is that
>>> correct, as well?
>>>
>>> I cannot find any mention of the coax requirements, from the
>>> radio/combo out to our 80-meter wire loop antenna. Right now, using
>>> only my K2/100 I am able to use  8X coax.
>>>
>>> Will I still be able to use that coax cable with up to 500 Watts output?
>>>
>>> What other considerations do I need to make?
>>>
>>> Thanks in advance,
>>>
>>> Carter Craigie, N3AO
>>> Blacksburg, VA
>>>
>>>
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