RadioBanter - View Single Post - Loop Antennas / minijack works-clips don't / impedence??

Telamon · August 19th 06, 09:48 PM posted to rec.radio.shortwave

In article . com,
wrote:

RHF wrote:
wrote:
Thanks.

I was asking if the tubing made a difference, so that I could
TEST using insulated wire directly on the antenna... and then get
some tubing once I see that the wrapping works and how many wraps
are needed.

1 - If you Wrap the Insulated Wire Directly on-to the Whip
Antenna : Then you have a Fixed {Permenant} Installation on the
one Radio.

DANR - Yes - The Tubing will make a difference.

Since the Insulated Wire will be closer to the Metal of the Whip
Antenna and therefore coupling to it more effectively. You will
find that few turns are required with the Direct-Wrap. More Turns
when the Tubing is used 'in-between' the Wire and the Whip Antenna.

TIP # 1 - Instead of Tubing for your first attempt. Try a few wraps
of Paper taped around the Whip Antenna as a Thin Core to make the
Coupling Coil more easier to Put-On or Take-Off as needed.

TIP # 2 - With the Tubing the Coil Assembly can be positioned
{move} In-and-Out on the Whip Antenna so that the Coupling Effect
between the Whip and Coil can be varried {adjusted} for the best
reception.

Well, I went from 10 wraps, to about 40 wraps (of the same 22 gauge
insulated wire), directly around the antenna. I extended the bottom
(thick) part of the antenna, just enough to fit the wraps (-the wraps
are NOT spaced out). I then attached antenna and ground wires of the
loop to the ends of the wire wrapped around the antenna.

Well, off of the rod by itself, I can hear CHU Canada, but it's below
1 on the S-Meter. Using the inductive connection (40 wraps), it gives
a signal of 4 -- but it's VERY noisy. (I tried reversing the
antenna/ground to no avail).

With the antenna clip directly to the top (thin part) of the rod
antenna (rest of rod not extended), I get signal of 6 but very noisy.
When I connect the ground clip to the battery, it get's MUCH quieter
(than without ground, or with inductive connection) and it stays at a
signal of 6. Direct connection of the antenna to a radio with an
antenna jack is still much better! (I did a test with the clips to
that radio - in order to make sure it's an antenna connection issue).

So, as of now, the inductive connection isn't helping. Suggestions or
recommendations?

I emailed Universal about the AA-1, to ask if it's ok to use with
active antennas (it's also $60...which is a bit much, considering).

The radio input is a differential mode input. This means it see a signal
relative to its internal ground. Most local noise is common mode so an
antenna setup that picks it up and presents it to the radio input causes
the radio to respond to it without a ground connection. Connecting an
antenna to just the antenna terminal causes any received station by the
antenna to look the same as any local noise it also picks up since both
are presented to the radio as a signal to ground. Connecting an antenna
to the radio antenna terminal and ground causes the received station to
appear differentially across the radio input so the radio responds to it
and the common mode locally picked up noise is the same on the antenna
and ground terminal so it is rejected as a common mode signal.

--
Telamon
Ventura, California