[Elecraft] RF burns ... was K3: Very distorted audio on transmit

[David Gilbert]

Old timer here ...

I remember once building a DDRR antenna (before I learned what a joke 
that idea was) for 20m on the floor on my apartment using just wire for 
both the ring and the "ground plane".  It was essentially a vertical 10 
inches or so of wire with a quarter wave parallel wire transmission line 
configured in a circle to "match" it to my SB-101 barefoot.  I somehow 
managed to make some stateside CW contacts with it, but I had to wear 
thick gloves to avoid the severe RF burns (as in black holes deep into 
my fingers) from the hand key.  Needless to say it only lasted one evening.

73,
Dave   AB7E




On 3/11/2014 4:24 PM, Joe Subich, W4TV wrote:
>
> > Is having the Microham directly on top of the KAT500 Tuner with the
> > microphone cable almost touching the RF out a potential issue? If so,
> > this might be an easy fix for now.
>
> No, not if your antenna system is properly designed and there is no
> common mode current on the outside of the feedline.  If you do have a
> common mode issue, arrangement of equipment may make minor differences
> as the effective line length changes but rearranging equipment is not
> going to *fix* an antenna system issue.
>
> Old timers will recognize common mode as "getting bit by the mic" or
> getting a "tickle" when touching metal portions of the key <G>.  That
> was an extreme level of common mode RF (several volts).  Just a volt
> or two can seriously upset modern solid state equipment or impact low
> level microphone audio (a dynamic mic has a level generally less than
> 20 mV).
>
> 73,
>
>    ... Joe, W4TV