RadioBanter - View Single Post - wire plus mfj-1020c question

Geoffrey S. Mendelson · November 19th 08, 08:49 PM posted to rec.radio.shortwave

wrote:
Here's my plan:

- String up about 30' of copper wire in my suburban backyard using
insulators and rope.

ok.

- Solder a feedline to one end of the antenna wire. The feedline will
be made of ordinary insulated wire, not coax.

ok.

- Solder a banana plug to the end of the feedline.

ok.

- Bring the feedline into the house through a window.

ok.

- Attach the feedline to the antenna input (SO-239) of a MFJ-1020c
active antenna/preselector.

ok, MFJ actually suggests this some of their tuners.

- attach the MFJ-1020c to my Sony 7600GR using some sort of pl-259 to
mini (1/8") patch cable. Universal Radio has a PL-259 to mini adapter
(#1619). Alternatively, Durham Radio has this cable, which I'm
assuming will work for my purposes:

My experience with an ICF-2010, is that you want a really flexible
cable from the radio out. The 2010 came with short cords with moulded
plugs and little boxes at the other end. Using regular coax puts a
lot of strain on the radio.

Are there any problems with this setup, other than the lack of
shielding for the feedline?

No ground.

For example, is there a problem with using a banana plug to connect
the antenna to the MFJ-1020c?

See above.

Also, any thoughts on grounding? I think there is a difference
between lightning grounding and RF noise grounding, but I can never
figure this out.

Grounding serves two purposes. Although it does not look like it,
radio is really an AC circuit between the transmitter and the receiver.
An antena such as a dipole does not need a ground for reception as each
side works fine for it.

A single wire uses the ground as the "other half", and usually works
better with a ground, or a counterpoise wire. Since this only carries radio
wave level voltages and currents, it can be a small wire.

The other purpose is to shunt electrical energy from a lightening strike
or induced energy from a nearby strike to ground away from your radio.
That wire should be significantly larger and may be subject to building codes.

The use of a non shielded feed line may be a problem if you have an electricaly
noisy house. It's easy to tell, stand near the window (inside the house) with
your radio antenna's extended and listen for noise. Then stand outside.
If it becomes less noisy, you may want to use a sheilded feed line (coax)
into the house.

If you do, do not do anything with the shield at the antenna end except
seal it so that rain and snow won't get into it. Where it enters the house,
ground the shield. To keep things cheap, you can use rg-6 (TV) coax, F
connectors and an F connector grounding block. Make sure the grounding
block is OUTSIDE the house and follow any building codes about grounding
it.

What ever you do, unplug the antenna from the tuner when not using it
if possible, especialy during thunderstorms.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM