[Elecraft] K3 & Beringer HA400

[Don Wilhelm]

Steve,

Thanks for those details.  I am almost certain Jim Brown K9YC would 
refer to this as a "pin 1" problem, and that is the reason that bypass 
caps are not likely to help.
You might be able to minimize it with some work to the Beringer - look 
carefully at how the cable shields are routed.  If they connect to the 
PC board directly, this is the classic pin 1 problem - they should be 
connected in such a way as to route the energy on the outside of the 
shield to the *outside* of the enclosure rather than going first to the 
PC Board ground plane..
Perhaps you can make some mods to that equipment, perhaps it is just not 
worth it.  Many enclosures for inexpensive equipment are plastic, so 
there is no way to avoid the pin 1 problem in those cases.  Once the RF 
energy gets inside the enclosure, there is no telling in which circuits 
it might cause problems.  In the hamshack, metal enclosures for audio 
equipment is almost mandatory, and if designers would pay attention to 
the pin 1 situation, many user headaches would be solved.

Note that in days of old, connectors used to mount on the enclosure, and 
thus prevented this pin 1 problem because the RF would flow on the 
outside of the enclosure and not make it to the inside, but in more 
modern times, connectors mount directly on the PC board and may or may 
not connect from the board ground plane to the enclosure - and even if 
it is connected to the enclosure, it is likely to be on the inside - RF 
travels on surfaces due to 'skin effect', so visualize the paths - the 
inside of a metal enclosure is a different conductor than the outside at 
RF frequencies - and you will see the difficulties presented.

73,
Don W3FPR

Steven Pituch wrote:
> Don and Dick,
> It does not occur with "TX Test"  However, it is not any worse if I use my
> ALS600 at 400 Watts, or I totally disconnect the amp and just use 50 Watts
> out of the K3.
>
> I think it is RF related, but only run into this problem with the HA400.  I
> do run 450 Ohm ladder line into my shack up to my link coupled tuner but
> just thought that it shouldn't happen to a proper design.
>
> If I run with the front panel audio volume to zero and use the front phones
> jack to the HA400 I get it bad if I plug the phones into the HA400 with the
> HA400 volume set to about a 3.
>
> I have the same problem with the line out.
>
> If I disconnect the audio "IN" into the HA400.  I still get the buzz in the
> phoes when I talk.  So it is RF getting into the HA400.
>
> I wonder if some bypass caps in the HA400 might help.
>
> Steve, W2MY
>   
>