Brian, N6IZ on the TopBand reflector writes regarding RFI, intermod,
etc from various sources: (My question will follow.)
> It could also be a junction of sometype in the
> antenna system that is acting as a non linearity (diode effect ?). I
> have had this occur where I joined disimilar metals in the antenna
> element. In my case I had used a cheap steel crimp lug to join the
> 2nd half of my vertical with the bottom copper pipe. When the
> rains came I started hearing BC interference on 160. Replacing the
> lug with a tinned copper lug solved that issue.
>
> I suppose a nearby steel wire fence or other poor connections could
>
> generate enough energy to create the carrier, however the BC
> stations
> would have to be fairly close, maybe less than 10 miles ?
Brian, good input...thanks. It was a subject that might apply
to a portable antenna for DX-pedition use I am working on.
This has to do with the connection of "load wires" at the top
of a pole. These load wires are also part of the guying system. The
antenna will be subjected to salt spray, buffeted by high winds
(up to 100mph!), rain, cold temperatures, etc..... just about
anything that Mother Nature can toss at it.
Being a DXpedition antenna, consider that these load wires and other
stuff must be very convenient to connect. IMV, the twisting
and/or soldering of wires is not the thing to even consider.
Also consider that this would be a multi-multi operation so
one would not want to "generate" any RFI for nearby radios.
So, I have come up with a few methods to attach up to 4 load wires
to the top of the aluminum pole. I would like some learned input
about the possibility of intermod/RFI caused by "diode effects" and
such resulting from any of the following methods of attachment:
1. A bare copper load wire wraps around a stainless steel (SS)
guy thimble, the thimble is attached to a plastic "guy ring" (made
of 1/4" Lexan) with a SS carabin hook (or other similar hook).
A pigtail lead is pre-soldered to the load wire and the other
end is firmly connected to a SS stud on the pole with a solder
lug "approved" for AL/CU connections. That assembly is
then firmly clamped down on the stud with a SS wing nut.
2. A copper load wire, *insulated* with Teflon tubing, wraps
around a stainless steel (SS) guy thimble, the thimble is
attached to a plastic "guy ring" with a SS carabin hook. A
pigtail lead is pre-soldered to the load wire and the other end is firmly
connected to a SS stud on the pole with a solder lug "approved"
for AL/CU connections. That assembly is then firmly clamped
down on the stud with a SS wing nut. So, now the connection
hardware is left "floating", but is still very near hi-voltage RF.
3. A bare copper load wire wraps around a stainless steel (SS)
guy thimble, the thimble is attached to a aluminum "guy ring"
with a SS carabin hook. A pigtail lead is pre-soldered to the
load wire and the other end is firmly connected to a SS stud
on the pole with a solder lug "approved" for AL/CU
connections. That assembly is then firmly clamped down on
the stud with a SS wing nut. A jumper wire firmly connects
the AL guy ring to the mast. So, now any "diode joints" and
the like are shorted out...or are they?
4. The load wire(s) terminate with strong, AL/CU "ring"
connectors and those attach to a single SS stud at the top
of the pole with a SS wing nut. Good RFI, etc, prevention
I think, but mechanically weak unless one can find some
suitable, very strong connectors with 1/4" hole and can
handle say, #12 or #14 insulated flex-weave. Do connectors
like that exist or are they even advisable for this use? any
other ideas?
I'm leaning toward method 3, but I'm open to other ideas.
What say?
73,
Charlie/N0TT
CC: RFI@contesting.com
> Regards,
>
> Brian
> N6IZ
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>
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