[Elecraft] my KPA1500 and 160M

[David Gilbert]

More likely that the ferrite core is getting hot from excessive VSWR.  
High current could, but rarely does, heat up the coil, but it's high 
voltage which often heats up the core.  At low power (and therefore low 
VSWR voltage) it wouldn't necessarily be a problem, but at high power it 
easily could.  I know this from personal experience with a 160m 
Inverted-L that initially had a high VSWR that with high power heated up 
a MUCH better common mode choke (homebrew per K9YC guidelines) than the 
Balun Designs stuff.

73,
Dave   AB7E


On 9/2/2020 5:12 AM, Bill Johnson wrote:
> I would agree that the coil could overheat.  The model number is left out.  The Balun Design coil chosen may not be satisfactory for your power despite the 5KW rating.  Which Balun are you using?
>
> Bill
> K9YEQ
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of David Gilbert
> Sent: Tuesday, September 1, 2020 12:28 PM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] my KPA1500 and 160M
>
>
> One distinct possibility is that the 4:1 balun is getting hot at 1500 watts.  Have you tried running the KPA1500 at a lower power?
>
> 73,
> Dave  AB7E
>
>
>
> On 9/1/2020 9:36 AM, w5sum at comcast.net wrote:
>> This morning I put up a W7FG true ladder line 160M doublet.   Upon
>> testing, the K3 internal atu does great, matches at 1.3:1.  But when I
>> throw the KAP1500 in line, it gets all pissed off, throws up and
>> faults out.  Says SWR is 99:1 !!!
>>
>> The Antenna:  The Apex is at 50'.  It is in a inverted Vee config,
>> with both ends approx 20' off the ground.   I'm using 59' of the 600
>> ohm true ladder line to a Balun Designs 5KW 4:1 Balun. This is fed
>> with 22' of Wilson LMR400
>>
>> Both the K3 internal atu, AND the KPA1500 internal atu get a great
>> match on 80M, 1.2:1   with no issues.
>>
>> Honestly, most of the work on 160M is FT8 running 20 watts or less, so
>> just using the K3 to get a successful match on 160M is fine
>>
>> I just wonder why the KAP1500 doesn't like the same antenna the K3 likes.
>>
>> Any ideas here fellers?
>>
>> thanks and 73
>>
>> 73 and GL OM DE w5sum
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