Renee,
As a long-time user of longwires, I can tell you that their performance is
very much dependant upon a good ground. However, that is mostly an issue
separate from the RFI/TVI issues you are encountering. I did operate from
an apartment (two different locations) with a random wire and tuner. The
"ground" I used was a counterpoise system that consisted of multiple wires
of different lengths run around the floor baseboards of the shack and
connected to the grounding stud of the tuner. You do not mention if your
longwire is fully on the building roof or if it is ties to the building,
but runs out to a tree. (If it runs to a tree, at least the building is in
a little less of the field radiated from the wire.) I presume your tuner
is in the shack, but if you have the Icom remote tuner, so much the better
IF it is up on the roof. You might be aware that MFJ makes a Ground Tuner,
which may be able to improve (by reducing the impedance of) the path to
whatever ground you are using. If you are using the electrical system 3rd
wire for your ground, you may well be radiating appreciable currents within
the building wiring. Since you have roof access, do you have the
capability to drop a ground wire from either the roof or your shack window
to a ground rod or rods on the outside? That would place most of the RF
current on a path outside of the building wiring.
Improving the antenna ground path may help to improve RF performance of the
longwire, but it probably will do little for RFI issues. One way to reduce
the RF flowing on your ground system (whatever it may consist of) would be
to use antennas that are not dependant upon ground for their operation. A
longwire depends upon ground at the tuner. A "standard" 1/4 wave vertical
depends upon ground (typically, a radial "system") at its feedpoint.
Dipoles/inverted-Vs and loop antennas, as well as the 1/2 wave verticals,
are not ground dependant. You want a ground connection at the rig and
tuner for electrical safety, but ground RF currents are minimal with those
antenna types. The chokes that Robie, AJ4F, mentions are good starting
points. Of course, even with ground currents controlled, fundamental RF
overload to TVs and phones, due to close proximity of your antennas to
building wiring (both power and telephone) and the devices themselves, can
still occur; that requires other techniques which have been discussed on
this reflector many times. The ARRL RFI book is certainly a great store of
info. Good luck.
73, Dale
WA9ENA
Robie Elms <aj4f@swbell.net>@contesting.com on 02/07/2001 05:46:21 AM
Please respond to Robie Elms <aj4f@swbell.net>
Sent by: owner-rfi@contesting.com
To: NZ8C@aol.com, rfi@contesting.com
cc:
Subject: Re: [RFI] Apartment RFI problem
Renee,
I found that a lot of RFI is caused by RF currents flowing in AC power
system of my house. These currents apparently came from current induced
(or
coupled) into the shield of the coaxial feed line from my antenna. I
installed a choke type balun at the antenna and a AC line filter at my
transmitter. This elininated the problem. The balun that I used came from
the Wireman , http://www.thewireman.com/ , in South Carolina and the filter
from ICE (Industrial Communications Engineers) http://www.inducomm.net/
.
The ARRL has a good book on RFI - The ARRL RFI Book.
I hope this information gives you some assistance. Please let me know if
you have specific questions.
73,
Robie - AJ4F
----- Original Message -----
From: <NZ8C@aol.com>
To: <rfi@contesting.com>
Sent: Wednesday, February 07, 2001 1:09 AM
Subject: [RFI] Apartment RFI problem
>
> Hello all!
> I am hoping someone here can help us out. My husband and I are both hams.
> Currently we are running an Icom 756Pro into either a random wire or a
> vertical, depending on the band. We live in a 3rd floor apartment which
is
> the top floor in this building. The antennas are up on the roof. Because
of
> our location grounding is a problem. We seem to have problems using the
> longwire on 40 and 80 meters as we are getting into phones and TVs. On
> 10/15/20 meters using the vertical we get into AM radios and phones. Is
there
> anything we can do or filters we can buy that can help eliminate these
> problems?
> 73,
> Renee
>
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