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Julian, G4ILO wrote:

The idea of using a counterpoise made from a "roll-up" short wave
antenna seems a good one. Unfortunately as so often I find myself
cursing the fact that I do not live in the US because I have no Radio
Shack shops where I can obtain one.

I almost bought the radio shack antenna until I realized it was insulated
wire. I guess that if it is only partly unwound, then the end will have a
coil on it.
I wouldn't want to have that on the end of a dipole but I just don't know
about that the use in a counterpoise. (I hope some else comments on this )

If we can assume this is OK to do then you could just solder a wire or a
clip to the end of the measuring tape or use a small nut and bolt scraping
the shield.

You can also take a plastic chalkline that carpenters use, discard the
string, put wire on the spool with clips on the end.
If you take 2 of those and some chopsticks and rubber bands then you also
have a dipole with open feed ladder line.
This idea is Bonnie Crystal, KQ6XA's Idea and it is called the "MINIBAC"
Here is the page on it

I am using some # 22 wire and I get 77 feet on each chalk line. The secret
is to completely unwind each line.

73 DE Sharyl W3VET


Just to you Julian,
Is it SWR bars on the transmitter that you are referring to for your
measurements?
If you are using an antenna analyzer you may be near a commercial
transmitter 5 miles or so and the readings can be pretty weird.

--- In FT817@y..., "Sharyl - W3VET" <w3vet@a...> wrote:

I almost bought the radio shack antenna until I realized it was

insulated

wire. I guess that if it is only partly unwound, then the end will

have a

coil on it.
I wouldn't want to have that on the end of a dipole but I just

don't know

about that the use in a counterpoise. (I hope some else comments on

this )

It might work on the lower bands (I used a coil of wire to shorten
the standalone 40m counterpoise for the ATX, as detailed in Monday's
posting) but the problem is as the counterpoise length increases the
coil value decreases, which will tend to cancel each other out. A
better solution would be a steel measuring tape, if you can find one
that is not painted, so the turns short together when they are reeled
in.

Just to you Julian,
Is it SWR bars on the transmitter that you are referring to for your
measurements?
If you are using an antenna analyzer you may be near a commercial
transmitter 5 miles or so and the readings can be pretty weird.

I did the measurements using a separate SWR meter, or using the
Elecraft K2 which has a built-in SWR readout.

Julian, G4ILO

By the way for those who don't know,
the radio Shack roll up is designed like a very small chalk line reel.
works the same.
cheers,
sas

the radio Shack roll up

One note -- I think the RS reel is only ~23 feet long, which means it is
probably too short to be effective for 40m or below, although I think one of
the SW rcvr makers (Sony? Grundig?) also makes these and perhaps they are
longer.

73
John Newell






























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Waters and Stanton have something similar. It is called the Sangean
ANT-60 short wave antenna. It holds 7 metres of wire and costs 15
quid. I don't know if it is the same as the Radio Shack one that has
been mentioned.

Julian, G4ILO

--- In FT817@y..., "Sharyl - W3VET" <w3vet@a...> wrote:

By the way for those who don't know,
the radio Shack roll up is designed like a very small chalk line

reel.

works the same.
cheers,
sas

I have been using the Radio Shack roll up as a counterpoise for a few months now and it works great
on 20 meters and up.
I can always get a match very quickly with my AT mono band whip antennas and have worked some
great DX from the kitchen table!.

73 Bill
W9WCR

--- In FT817@y..., julian@t... wrote:

...It holds 7 metres of wire and costs 15
quid. I don't know if it is the same as the Radio Shack one that has
been mentioned...
...
--- In FT817@y..., "Sharyl - W3VET" <w3vet@a...> wrote:

By the way for those who don't know,
the radio Shack roll up is designed like a very small chalk line

reel.

A small spool of hookup wire, an alligator clip, and a rubber band
work pretty well, too.

Frank
AB2KT

I tried the radio shack swl radio antenna as a counterpoise to a
Maldol whip antenna. Interstingly using the MJF analyzer, mine shoeda
resonance of 25M rolled up or extended, however it will show different
reactance depending on the amount that is rolled up (duh! it acts a
coil). Next I set the frequency on the MFJ to a working frequency of
28.500Mhz and rolled out until it showed an SWR of 1.1! and I marked
the spot with red tape, it I did not check the length but I can if
someon is interested. The reactance was 0 and the resistance was 100
ohms, I guess you can actually transmit with just the SWL antenna!? I
figured that if it was tuned it would act as tuned counterpoise when
attached to ground side of the Maldol. It seems to me that the idea
of using a "counterpoise" as opposed to a "ground plane" is in reality
just turning your quarter wave whip into a lazy dipole.

I just threaded it through the retainting slot that mates with the BNC
dimples and connected it up. I will get some lug in the future to make
it easier to connect it but for now it works ok since it have ha nice
snug fit.

I am able to get the FT817 down to 2-1 bars on the SWR meter by
adjusting the whip length. I might be able to get it down to 0 by
adjusting the counterpoise length, but I am a bit lazy right now.

Have fun fellow experimenter,

laz -- k2laz

using a "counterpoise" as opposed to
a "ground plane" is in reality
just turning your quarter wave
whip into a lazy dipole.

Ha! Glad someone said it out loud -- this has been my surmise also. I
would be interested in hearing from someone who's better versed in antenna
theory whether or not this is in fact correct!

73
John Newell
KB1FPM

































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using a "counterpoise" as opposed to
a "ground plane" is in reality
just turning your quarter wave
whip into a lazy dipole.

Ha! Glad someone said it out loud -- this has been my surmise

also. I

would be interested in hearing from someone who's better versed in

antenna

theory whether or not this is in fact correct!

is very interesting on this point.

Frank
AB2KT

Frank AB2KT --

Tnx for the link. This keeps getting funnier. I was
reading that page last night, but only got to #1. I really
enjoy Cebik's articles, though I confess I don't always
understand it all.

The discussion on the page you mention raises questions what
an antenna like the MP-1 (or the AP-10) with the appropriate
"counterpoise" <slap me! :-)> really is, and which part of
it is really doing the radiating (if the "counterpoise" is
the correct length)??? Only at #7 now, maybe the answer
lies further on!

Tnx es 73
John Newell

John --

The discussion...raises questions what
an antenna like the MP-1 (or the AP-10) with the appropriate
"counterpoise" <slap me! :-)> really is, and which part of
it is really doing the radiating (if the "counterpoise" is
the correct length)???

The $64,000 Question?

The article doesn't put it quite this way, but here's the gist, I
think:

Clearly the counterpoise radiates, unless you've gone out of your way
to waste the radiation, which is the point that Bonnie KQ6XA has been
making repeatedly.

But unlike an orthodox dipole, a lot of that radiation is involved in
heavy interaction with the "radiator" radiation, with phase
reinforcement or cancellation, secondary effects of ground reflection
and coupling, and so on.

One possible outcome is a very eccentric radiation pattern. But it may
be possible to smooth that out by redistributing and spreading out the
interaction through multiple radials or counterpoises, capacitance
hats, and so on. In the limit, this is a disk, of course; but still a
radiator, although with the "flattest" interactions with the vertical
element. Thus the classic advice to use as many radials (the best
approximation to a disk) as your patience will allow.

So an MP-1 with a proper single-wire elevated counterpoise is just a
half-loaded dipole with a radiation pattern to make your hair stand on
end. An MP-1 *without* a proper elevated counterpoise is just a waste
of watts. :-)

That's how I read it, anyway.

Frank
AB2KT

Going back to the question of what antennas we use and why the work (or
don't), which continues to be a hot topic here, I have ordered a copy of Les
Moxon G6XN's book _HF Antennas for All Locations_ (RSGB via ARRL), which was
highly recommended to me. Along the way, I found an interesting article on
the ARRL website that some of you may find interesting:
The basic point is that we can get a
new look at verticals if we think of them as asymmetric dipoles. Verne
W6MMA's products are "wicked nice" engineering but they do not seem to be
plug-n-play (which is fine, we're experimenters?) -- so I am going to
continue to read and experiment and hope we can share feedback about what
works. The little FT-817 really does seem to encourage us to figure out how
to make more compact ants work well.

73
John Newell
KB1FPM

John --

The discussion...raises questions what
an antenna like the MP-1 (or the AP-10) with the appropriate
"counterpoise" <slap me! :-)> really is, and which part of
it is really doing the radiating (if the "counterpoise" is
the correct length)???

The $64,000 Question?

The article doesn't put it quite this way, but here's the gist, I
think:

Clearly the counterpoise radiates, unless you've gone out of your way
to waste the radiation, which is the point that Bonnie KQ6XA has been
making repeatedly.

But unlike an orthodox dipole, a lot of that radiation is involved in
heavy interaction with the "radiator" radiation, with phase
reinforcement or cancellation, secondary effects of ground reflection
and coupling, and so on.

One possible outcome is a very eccentric radiation pattern. But it may
be possible to smooth that out by redistributing and spreading out the
interaction through multiple radials or counterpoises, capacitance
hats, and so on. In the limit, this is a disk, of course; but still a
radiator, although with the "flattest" interactions with the vertical
element. Thus the classic advice to use as many radials (the best
approximation to a disk) as your patience will allow.

So an MP-1 with a proper single-wire elevated counterpoise is just a
half-loaded dipole with a radiation pattern to make your hair stand on
end. An MP-1 *without* a proper elevated counterpoise is just a waste
of watts. :-)

That's how I read it, anyway.

Frank
AB2KT

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contain confidential or proprietary information and may be subject to the
attorney-client privilege or other confidentiality protections. If you are
not a designated recipient, you may not review, copy or distribute
this message. If you receive this in error, please notify the sender by
reply e-mail and delete this message. Thank you.