[Elecraft] Data transmission on 30 meters with PX3 problem

[Bob Nielsen, N7XY]

Back in my early days as a ham (1950s), I inadvertently discovered that 
the metal housing of a D104 microphone was very effective in performing 
such a touch test.

Bob, N7XY


On 9/2/18 7:19 AM, John Oppenheimer wrote:
> On 09/02/2018 07:56 AM, Don Wilhelm wrote:
>> That W3EDP antenna is a strong suspect, as is any off-center fed antenna
>> or end fed antenna.  They can produce large amounts of RF in the shack.
> Hi Gwen,
>
> Don is correct. The W3EDP with a large choke Balun, as pictured, between
> the Unun and KX3 is an OCF Doublet with a resonant frequency of 11 MHz.
> It is rather difficult, if not impossible, to isolate a dipole end
> impedance using a choke Balun. The KX3, being at the high impedance
> point on 30 meters, will experience a rather high RF voltage.
>
> A way to determine if the rig is part of the antenna is to use what I
> call a "touch test." Observe SWR while transmitting, if touching the KX3
> antenna BNC jack causes the SWR to change, then the KX3 is part of the
> antenna. At the extreme, the touch results with a RF burn. I have
> experience RF burn at 15 watts.
>
> John KN5L
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