Tuned dipole Q:
 

My 160/80m trap dipole can be operated without
a tuner from 1.800 to 1.930. I mainly operate in
that range (usually on 1.893) and I have a tuner for
operating above 1.930. Easy.

My question is this - is it better to resonate high and
use a tuner to go lower or do it the way I'm doing now
(resonate low and use a tuner to go higher)?

Or will it even matter enough to notice??? My guess
is (at these freqs) no......

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

On Wed, 26 Jan 2005 15:05:39 -0600, "Ken Bessler"
wrote:

My 160/80m trap dipole can be operated without
a tuner from 1.800 to 1.930. I mainly operate in
that range (usually on 1.893) and I have a tuner for
operating above 1.930. Easy.

My question is this - is it better to resonate high and
use a tuner to go lower or do it the way I'm doing now
(resonate low and use a tuner to go higher)?

Or will it even matter enough to notice??? My guess
is (at these freqs) no......

Dear Ken,

Your trap dipole is resonant only in the sense that you see
approximately 50 + j 0 ohms at the input to the feedline. I will
assume that it is not actually of the length of a "resonant dipole"
(about 260 ft.).

Therefore, we are talking about a "resonant" antenna/feedline
"system".

The next issue is the radiation pattern of the antenna. Regardless of
how you use it (i.e., with or without a tuner), it will have a pattern
that is a function of its configuration and operating frequency.
Whether or not a tuner is involved is not a factor.

The only real issue is efficiency. Everything else being equal, the
tuner is going to rob you of some of your power. How much will depend
on many factors - the primary ones being the actual impedance seen by
the tuner and the specific design of the tuner - especially its
inductor.

Therefore, it would appear that you are doing the best thing - namely,
to use the tuner only when you have to.

Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html

On Wed, 26 Jan 2005 21:27:31 GMT, W9DMK wrote:
On Wed, 26 Jan 2005 15:05:39 -0600, "Ken Bessler"
wrote:

My 160/80m trap dipole can be operated without
a tuner from 1.800 to 1.930. I mainly operate in
that range (usually on 1.893) and I have a tuner for
operating above 1.930. Easy.

My question is this - is it better to resonate high and
use a tuner to go lower or do it the way I'm doing now
(resonate low and use a tuner to go higher)?

Or will it even matter enough to notice??? My guess
is (at these freqs) no......

Dear Ken,

Your trap dipole is resonant only in the sense that you see
approximately 50 + j 0 ohms at the input to the feedline. I will
assume that it is not actually of the length of a "resonant dipole"
(about 260 ft.).

Therefore, we are talking about a "resonant" antenna/feedline
"system".

The next issue is the radiation pattern of the antenna. Regardless of
how you use it (i.e., with or without a tuner), it will have a pattern
that is a function of its configuration and operating frequency.
Whether or not a tuner is involved is not a factor.

The only real issue is efficiency. Everything else being equal, the
tuner is going to rob you of some of your power. How much will depend
on many factors - the primary ones being the actual impedance seen by
the tuner and the specific design of the tuner - especially its
inductor.

Therefore, it would appear that you are doing the best thing - namely,
to use the tuner only when you have to.

However, I would like to see an answer to his question:

1. Is it best to cut "high" and tune for "low" when necc.?
-or-
2. Is it best to cut "low" and tune for "high" when necc.?

-- when operating on a band (i.e., 75/80M or 160M) where a 50 to
100 kcs. shift in freq. is a large'ish percentage change in
wavelength.

3. ..or, is it Mox Nix?

73
Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK

I read somewhere that as the length of each leg of the dipole approaches 5/8
wave the gain increases.
(The reason for the 5/8-wave vertical )
So - from that - I would gues you'd have a smidgen better antenna by cutting
it long and tuning to match.
But for the record - I would cut it so as to use the tuner less often.

On 26 Jan 2005 22:35:18 GMT, Allodoxaphobia
wrote:

On Wed, 26 Jan 2005 21:27:31 GMT, W9DMK wrote:
On Wed, 26 Jan 2005 15:05:39 -0600, "Ken Bessler"
wrote:

My 160/80m trap dipole can be operated without
a tuner from 1.800 to 1.930. I mainly operate in
that range (usually on 1.893) and I have a tuner for
operating above 1.930. Easy.

My question is this - is it better to resonate high and
use a tuner to go lower or do it the way I'm doing now
(resonate low and use a tuner to go higher)?

Or will it even matter enough to notice??? My guess
is (at these freqs) no......

Dear Ken,

Your trap dipole is resonant only in the sense that you see
approximately 50 + j 0 ohms at the input to the feedline. I will
assume that it is not actually of the length of a "resonant dipole"
(about 260 ft.).

Therefore, we are talking about a "resonant" antenna/feedline
"system".

The next issue is the radiation pattern of the antenna. Regardless of
how you use it (i.e., with or without a tuner), it will have a pattern
that is a function of its configuration and operating frequency.
Whether or not a tuner is involved is not a factor.

The only real issue is efficiency. Everything else being equal, the
tuner is going to rob you of some of your power. How much will depend
on many factors - the primary ones being the actual impedance seen by
the tuner and the specific design of the tuner - especially its
inductor.

Therefore, it would appear that you are doing the best thing - namely,
to use the tuner only when you have to.

However, I would like to see an answer to his question:

1. Is it best to cut "high" and tune for "low" when necc.?
-or-
2. Is it best to cut "low" and tune for "high" when necc.?

-- when operating on a band (i.e., 75/80M or 160M) where a 50 to
100 kcs. shift in freq. is a large'ish percentage change in
wavelength.

3. ..or, is it Mox Nix?

I don't consider 50 - 100 kHz to be a sufficiently large shift to make
any difference. It's only 2 1/2%, which is nothing.

So, you are correct - es macht Nichts aus!

Remember, "resonance" is not all it's cracked up to be. In fact, it's
almost irrelevant at the typical heights above ground encountered (45
ft or less for 80 and 160 m). I'm not saying that you do not need to
cut a dipole to the frequency. What I am saying is that at low heights
all the power goes straight into the clouds, anyway. The reason most
people like "resonance" is for the ease of matching to the rig's
output stage - not that the antenna works any better. You probably
don't care in which direction in the horizontal plane the energy goes
- it's going to be wrong half of the time, anyway - right?


Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html

On Wed, 26 Jan 2005 18:30:36 -0500, "Hal Rosser"
wrote:


I read somewhere that as the length of each leg of the dipole approaches 5/8
wave the gain increases.
(The reason for the 5/8-wave vertical )
So - from that - I would gues you'd have a smidgen better antenna by cutting
it long and tuning to match.
But for the record - I would cut it so as to use the tuner less often.



Do you suppose, by any chance, that Louis Varney had anything like
that in mind when he invented the G5RV antenna specifically for the 20
m band with its 1.5 wavelength flat-top ( about 3/4 wavelength on each
side)?


Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html

On Wed, 26 Jan 2005 15:05:39 -0600, "Ken Bessler"
wrote:

My 160/80m trap dipole can be operated without
a tuner from 1.800 to 1.930. I mainly operate in
that range (usually on 1.893) and I have a tuner for
operating above 1.930. Easy.

My question is this - is it better to resonate high and
use a tuner to go lower or do it the way I'm doing now
(resonate low and use a tuner to go higher)?

Or will it even matter enough to notice??? My guess
is (at these freqs) no......


My opinion is that it is better to use the longest antenna reasonably
possible and use the tuner to trim it.
Buck
--
For what it's worth.

W9DMK (Robert Lay) wrote:
Do you suppose, by any chance, that Louis Varney had anything like
that in mind when he invented the G5RV antenna specifically for the 20
m band with its 1.5 wavelength flat-top ( about 3/4 wavelength on each
side)?

I read somewhere that Louis wanted that nice
cloverleaf pattern on 20m from his home QTH.
--
73, Cecil http://www.qsl.net/w5dxp


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Buck wrote:
My opinion is that it is better to use the longest antenna reasonably
possible and use the tuner to trim it.

The proper choice of feedline length will tune it
to system resonance without a conventional tuner.
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil Moore wrote:

Buck wrote:
My opinion is that it is better to use the longest antenna reasonably
possible and use the tuner to trim it.

The proper choice of feedline length will tune it
to system resonance without a conventional tuner.

And of course, I'm talking about ladder-line, not coax.
--
73, Cecil http://www.qsl.net/w5dxp


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