[Elecraft] KPA1500 RFI on 10 Meters

[Eric Swartz - WA6HHQ, Elecraft]

Scott - what is your 1500 s/n?
Eric
/elecraft.com/

On 12/17/2019 1:04 PM, K9MA wrote:
> 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