[Elecraft] K3/100 -Second floor- no RF ground ??

[Julian, G4ILO]

Chuck, I have an almost identical setup to what you are proposing. It's
really difficult to get an effective RF ground on an upper story because the
ground connection has resonance which may result in a high impedance at
higher frequencies. Some people have suggested an MFJ Artificial Ground but
that basically tunes up a wire counterpoise inside the house and I can't see
how that can be good either for low noise or RFI immunity because the wire
must pick up noise and radiate signal.

My two HF antennas are an MFJ magnetic loop and a multiband dipole. I have a
balun on the dipole, and I have never experienced RF on the radio though I
do get a strong field from the magnetic loop that can cause the computer to
act up at high power. I don't regret getting the 100W PA for my K3 as I was
getting frustrated with QRP during the years of no sunspots and now I'm used
to having it I can't easily put the genie back in the bottle, but QRP is
really preferable for many reasons in this kind of situation.

I have experienced the common mode pickup that has been mentioned where RF
radiated by one antenna was picked up by the feeder of another and fed back
down to the shack. It really started when I added 2m antennas to my attic
antenna farm. I would probably never have noticed if I was not a keen PSK31
operator and have an IMD meter but the effect is noticeable as poor transmit
IMD on some HF frequencies. The problem is really only solvable by getting
rid of the 2m antennas, but I have managed to mitigate it to some extent by
making copious use of clamp-on ferrite suppressors on every cable that goes
into the K3. I also found that "grounding" the equipment to the copper pipes
of the central heating system was actually making it worse.

If you just have the one antenna then hopefully you won't have the problem
this bad and won't need to go to such lengths, but I have been trying to
push the envelope of what can be achieved with an indoor antenna system.


callen1155 wrote:
> 
> 
> Hello guys,
> 
> I'm planning on purchasing a K3/100 but am concerned about my second floor
> shack and RF problems.
> 
> First of all:
> 1) I don't have an RF ground (don't really want to drill thru the house
> and siding for the ground strap) and 
> 
> 2) my antenna is a semi-indoor/attic dipole (HOA).
> I'm running a coax from the second floor radio to the attic where i attach
> to a dipole (no balun) and the dipole runs the length of the house each
> way and out the eaves where both wires run out about 35 yards to the
> trees.  
> 


-----
Julian, G4ILO. K2 #392  K3 #222.
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

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