[Elecraft] Rigblaster Pro RF issue

[Don Wilhelm]

Bill,

The very best way to combat RF Feedback is to eliminate it at its source -
the antenna.  Balanced resonant antennas with a balun at the feedpoint
usually are no problem.  Balanced fed non-resonant antennas with careful
consideration to the run of the parallel feedline away from the antenna are
not usually a problem either.  Offcenter fed antennas and end fed wires are
difficult to tame, as are balanced antennas having a high impedance
feedpoint at the shack end of the feedline.  Vertiacal with an adequate
ground system are usually tame, but verticals with an inadequate ground or
resonant ground plane suffer from the same RF-in-the-shack problems as end
fed wires.

All that being said, one can experiment with counterpoise wires at the shack
end to determine if the RF is really the problem.  Cut a quarterwavelength
wire for the band to be tested and attach one end to the tuner or amplifier
ground - the far end is open circuit, just like the end of an antenna - it
will contain high RF Voltages, so be certain it is in the clear and out of
contact range of humans and pets.

If the counterpoise wire solves the problem, it can be used permanently, or
one can vow to solve the real problem in the antenna system.

In addition to considerations at the antenna system, be certain the mic jack
is grounded, and be certain a shielded cable is used between the RigBlaster
and the transceiver - that may or may not help.  Often grounding only one
end of the cable shield will help - experiment to determine which end is
more effective, but usually the end connected to the transceiver is the one
to ground.

Be certain you have not negated the ground isolation between the computer
and the transceiver with your connections to the RigBlaster - there are many
'sneak' ground paths that can exist, do not ignore any of them.  If you
extend the transceiver ground area to other cables and the computer that is
just more area for stray RF to impinge upon and cause trouble.  Suspect
everything until it can be eliminated from th esuspect list.

73,
Don W3FPR


> -----Original Message-----
> Sorry that is not a directly K2 related question, but this list
> has more ham
> brains located in one place than any other place I know.  I have always
> appreciated the help I have found here from the members.
>
> I am running a RIGblaster Pro with my K2.  Under QRP conditions, I have no
> problems.  However, on 40m & 80m QRO with an external amp, I am
> finding that
> I am getting serious RF getting back into the rigblaster.  I have isolated
> it to the rigblaster's microphone cable that connects the K2 to the
> rigblaster.  I am certain this is the path of the RF because I can replace
> the rigblaster mic cable with the K2s regular microphone and use
> its PTT and
> couple the sound from my headphones into the mic and get transmit without
> the RF crap on output.  My question is this.  What is the best way to
> eliminate the RF on the rigblaster's mic cable?  Would several
> ferrite beads
> do the job?  Anyone else ever have this problem or have suggestions?
>
> 73, Bill Allen  WA5PB
>