[Elecraft] 12 meter K3 RFI from nearby FM station

[Bob McGraw K4TAX]

I can't imagine 2 KW ERP FM directly causing that issue.   In reading 
the original post, he was getting splatter on 12M which would indicate 
the antenna was connected.   Nothing mentioned about the Preamp being on 
or off.  Normally for 12M it is on, maybe PRE II is on as well.   There 
are precautions stated n the manual in this regard.   As a result of any 
reactive input termination, it could be oscillating.   If so, all bets 
are off.  Birdies abound!

Then disconnecting "all cables" and I don't take this to mean antenna 
disconnected as well, but powering from a battery still show evidence of 
the problem.  I could see with the antenna connected, corrosion on the 
antenna element(s) or feed line connectors acting as a diode  or even a 
metal gutter, downspout and etc.  and being excited by the FM carrier 
plus subcarrier/pilot making it appearance as multiple birdies modulated 
by the FM audio.  However, with "everything" disconnected except for 
power cable and the problem remain,  very strange.  The K3S is built 
better and shielded better than this.

73
Bob, K4TAX



On 2/11/2016 11:03 AM, Alan wrote:
> On 02/10/2016 03:57 PM, Jim Brown wrote:
>> Yes, this hit me between the eyes as well. The K3 has Pin One Problems
>> at many (most?) connectors, so RF current flowing on shields of cables
>> plugged into those connectors will couple into the K3. I've been
>> preaching to Wayne about Pin One Problems since 2004, when we met in
>> Dayton.
>>
>> If the problem is around 90 MHz, I'd use multiple one-turn and two turn
>> chokes with #43 material on every cable except the SO239 output, which
>> IS actually bonded to the chassis. Also choke the power cable.
>
> But it sounds like he was still getting the problem with no cables 
> connected to the K3:
>
> On 02/10/2016 06:58 AM, Jon Zaimes wrote:
> ...
> > Even when ALL cables are removed (only the power lead connected).
> > Grounding or ungrounding made no change. I tried the radios on a
> > battery but still had the RFI. Tried some ferrites on the power
> > lead but no change.
>
> I suppose it could be a "pin 1" problem on the power leads.  It's kind 
> of hard to avoid that with an Anderson PowerPole connector. Probably 
> additional low-pass filtering on the DC input would help.
>
> Alan N1AL
>
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