Ed,
Your dummy load choices at 1500 watts range from expensive and good
(Bird) to cheap and not-so-good. For example the MFJ-264 is listed as
handling 1500 watts but if you read the fine print (the derating curve
printed on its case ) you're limited to 8 seconds at 1500 watts. And
each time you stress that dummy load its resistor value climbs by a few
ohms.
Frustrated with the commercial options available, I built a dummy load
using a huge heatsink from a salvage VHF transmitter and a
series/parallel combination of four 50 ohm 250 watt resistors purchased
on eBay.
https://www.ebay.com/itm/1PCS-Anaren-RFP-250-50RM-RFP250-50-RF-Power-Flanged-Resistors-250-Watts-50-ohm/133028134252?hash=item1ef9183d6c:g:uHQAAOSwyFhcvsvw
-larry (K8UT)
------ Original Message ------
From: "Ed G" <[email protected]>
To: "Larry (K8UT)" <[email protected]>; "[email protected]"
<[email protected]>
Sent: 2020-06-15 10:57:32 AM
Subject: RE: [Elecraft] KPA1500 Operation on 6 Meters
Hi Larry,
Yes, exact same problem is there with a known good dummy load in
place of the Steppir yagi I normally use.
--Ed—
Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
Windows 10
From: Larry (K8UT) <mailto:[email protected]>
Sent: Monday, June 15, 2020 10:09 AM
To: Ed G <mailto:[email protected]>; [email protected]
<mailto:[email protected]>
Subject: Re: [Elecraft] KPA1500 Operation on 6 Meters
Ed,
Not seeing that here. SWR value unchanged at 10, 20, 30, 35 watts of
drive. Suggest you test into a dummy load to see if the problem goes
away, which would suggest some issue with power level into the feedline
or antenna.
-larry (K8UT)
------ Original Message ------
From: "Ed G" <[email protected]>
To: "[email protected]" <[email protected]>
Sent: 2020-06-15 9:48:55 AM
Subject: [Elecraft] KPA1500 Operation on 6 Meters
>Folks,
> I am trying to understand some odd KPA1500 operation on 6
meters. When setting the power output of my K3 to give varying amounts
of drive to the KPA1500, I am seeing SWR as displayed on the KPA1500
changing by a significant amount depending on the drive level. This is
with the KPA1500 tuner bypassed. An LP-100A on the output of the
KPA1500 is also used and displays the correct low SWR at all drive
levels that I would expect to be seeing on the KPA1500 display.
> For example, with 5 watts drive from the K3, I see 1.3 SWR on
the LP-100, and 2.5:1 on the KPA1500 display. As I increase drive, the
KPA1500 SWR display goes down proportionally, until I get to about 40
watts drive. At the 40 watt drive level, I am seeing a nice healthy
1600 watts output, and both the LP-100 and the KPA1500 are showing the
same 1.3 SWR. 15 watts drive shows 1.3 on the LP100 and 2.0:1 on the
KPA1500 display. So I am not sure why the SWR sensing and display in
the KPA1500 is behaving this way? I do not see this oddity on any
other bands.
> I might also add that attempting to get the KPA1500 internal
tuner to bring down the high SWR as seen on the KPA1500 results in a
drop in SWR displayed on the KPA1500 to where SWR almost equals that on
the LP-100, but using the tuner I would expect that to be even better.
>--Ed—
>
>
>
>
>--
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