[Elecraft] KPA1500 RFI on 10 Meters

[K9MA]

Hi Eric,

I was able to tighten those screws a little, but it made no difference. 
Adding ferrites to the control cable near the PS helped slightly, 
suggesting that that is the source. The RF is definitely being received 
by the antenna, about 100 feet away: its strength depends on the antenna 
direction, and it is at least 7 dB weaker with a dummy load.

I have submitted a request to tech support.

73,
Scott K9MA



On 12/17/2019 13:44, Eric Swartz - WA6HHQ, Elecraft wrote:
> Hi Scott,
>
> We have seen this in rare cases on a few 1500s. It appears to be 
> caused by the ground connection between the rear RF INPUT SO-239 
> flange and the chassis.
>
> Very slightly loosening (not too far!) and then firmly re-tightening 
> all four screws on this SO-239 connector will insure a good ground 
> connection between this connector and the rear panel. (There are lock 
> washers between the nuts and the SO-239 inside.)
>
> If the screws are loosened too far, you may have to remove the bottom 
> cover of the amp to hold the interior nuts in place while you 
> re-tighten the four screws.  (Make sure the 50V power and control 
> cables are disconnected when you remove any covers on the amp.)
>
> 73,
> Eric
> /elecraft.com/
>
> On 12/14/2019 1:43 PM, K9MA wrote:
>> I guess it just shows how little I've been on 10, but I've had the 
>> KPA1500 for over a year now, and I just noticed that when I turn it 
>> on, my noise floor on 10 goes up about 3 dB. (And that's from an 
>> urban noise floor.) It's pretty flat over much of the band, not 
>> typical switching supply noise. Has anyone else experienced this and 
>> found a cure? (Other than using the old amp tube.)
>>
>> 73,
>>
>> Scott K9MA
>>
>

-- 
Scott  K9MA

k9ma at sdellington.us