RF in Shack

[Bill_Harris]

"The only problem I can see is a lot of RF floating
around in the shack. I think you'd be better off
running coax of the shack to the long wire and attach
your counterpoise at that junction." (Julius n2wn)

This can be a  problem when feeding a random length wire antenna, especially on different bands.  For a "cool" operation, I try to stay close to the low impedance feed point, (odd multiple of 1/4 wavelength) and attach a counterpoise, again, 1/4 wavelength for the lowest band.  30m will load on a wire cut for 80 and 15m will load on a 40m wire. For 20 and 10m you may have to cut a dedicated wire for each band.  If multiple antennas is out of the question, then some form of loading, to bring the feed point  impedance down, should do the trick. End loading would be preferred.  An external AT will do nicely, but you may have to put an RF choke on the input  of the AT if  the antenna is being voltage fed. QRP operation may not be a big problem with circulating currents.  They will be present but not in the magnitude as with QRO operation.
That's my 2 cents on the subject.  Of course, your mileage may vary. Good luck.

KXBill
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[Stuart Rohre]

Coax, will only exacerbate RF in the shack on an end fed long wire.  You
will have radiation back down the outside of the shield and if the coax is a
critical fraction of  a quarter wave at the shack end, it will radiate
there.

The unbalance in end feed with ladder line is only 10 per cent per L. B.
Cebik.

If the lengths are adjusted, you can expect minimal radiation problems in
the shack.

Or, feed the end wire from a parallel tank outside.  Then, you can on one
band at least, feed that with a link to coax.

73,
Stuart
K5KVH



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