Doublet Antenna question
 

Currently I have a coax fed trapped 75/40M dipole up between two
trees. The spacing of the trees (a bit over 110 feet) allows this
antenna with no extra length allowed, except for minimal support line and
insulator length.

I plan on replacing this dipole with 450 ohm ladder line feed doublet
so I can operate on more than just 75/40M, however a full 1/4 wave length
for 75 would be too long to fit between these trees.


My QUESTION(s): How effective would a balanced fed dipole of about
100 feet length be on 75M ? Should it tune OK with a tuner such as the
new MFJ balanced tuner? Or, if I were to put either the old 40M traps,
or wind coils for the new dipole to shorten 75M resonance, would it then
tune OK on all bands from 75M down with balanced feed?

Ed K7AAT

Doublet Antenna question
 

A G5RV would fit and meet your needs for all band operation with a tuner.

"Ed" wrote in message
. 93.175...

Currently I have a coax fed trapped 75/40M dipole up between two
trees. The spacing of the trees (a bit over 110 feet) allows this
antenna with no extra length allowed, except for minimal support line and
insulator length.

I plan on replacing this dipole with 450 ohm ladder line feed doublet
so I can operate on more than just 75/40M, however a full 1/4 wave length
for 75 would be too long to fit between these trees.


My QUESTION(s): How effective would a balanced fed dipole of about
100 feet length be on 75M ? Should it tune OK with a tuner such as the
new MFJ balanced tuner? Or, if I were to put either the old 40M traps,
or wind coils for the new dipole to shorten 75M resonance, would it then
tune OK on all bands from 75M down with balanced feed?

Ed K7AAT

Doublet Antenna question
 

I am running a 100 ft bowtie antenna ok with link coupled transmatch, fed
with 450 ohm twin lead and it tunes 75 thru 10 meters
Each side of center feedpoint has a pair of 50 ft wires, that are connected
at the ends with a piece of 6 ft wire.
"Ed" wrote in message
. 93.175...

Currently I have a coax fed trapped 75/40M dipole up between two
trees. The spacing of the trees (a bit over 110 feet) allows this
antenna with no extra length allowed, except for minimal support line and
insulator length.

I plan on replacing this dipole with 450 ohm ladder line feed doublet
so I can operate on more than just 75/40M, however a full 1/4 wave length
for 75 would be too long to fit between these trees.


My QUESTION(s): How effective would a balanced fed dipole of about
100 feet length be on 75M ? Should it tune OK with a tuner such as the
new MFJ balanced tuner? Or, if I were to put either the old 40M traps,
or wind coils for the new dipole to shorten 75M resonance, would it then
tune OK on all bands from 75M down with balanced feed?

Ed K7AAT

Doublet Antenna question
 

On Sun, 16 Oct 2005 18:28:36 GMT, Ed
wrote:
I plan on replacing this dipole with 450 ohm ladder line feed doublet

Hi Ed,

The answers to your questions are found in the quote above.

If those bands on the old antenna were already resonant, and they
matched, then you didn't need 450 Ohm ladder line.

If you are going to use 450 Ohm ladder line on a generic doublet, it
stands to reason you won't be resonant much anywhere (or you don't
count on it) and you anticipate tuning and use this line for low loss.

The only thing left to be said is about the lobe structure at any
particular frequency. Long, long antennas at high frequency develop
sharp lobes and nulls. That being said, it is more a matter of where
you are pointed and where you want to be heard. The solution to that
is to use a fan tail design for the higher bands' sake.

Using a doublet, ladder line, and a tuner is classic - it works fine.

73's
Richard Clark, KB7QHC

Doublet Antenna question
 

"Ed" wrote in message
. 93.175...

Currently I have a coax fed trapped 75/40M dipole up between two
trees. The spacing of the trees (a bit over 110 feet) allows this
antenna with no extra length allowed, except for minimal support line and
insulator length.

I plan on replacing this dipole with 450 ohm ladder line feed doublet
so I can operate on more than just 75/40M, however a full 1/4 wave length
for 75 would be too long to fit between these trees.


My QUESTION(s): How effective would a balanced fed dipole of about
100 feet length be on 75M ? Should it tune OK with a tuner such as the
new MFJ balanced tuner? Or, if I were to put either the old 40M traps,
or wind coils for the new dipole to shorten 75M resonance, would it then
tune OK on all bands from 75M down with balanced feed?

Ed K7AAT

If you are not satisified with the antenna you have then I would put up
about 130 feet of wire and feed it in the middle with the balanced feed. If
you can not get up the full 130 feet or so of wire, put it all up and let
the ends hang down. That is the support ropes could be attached 10 to 15
feet from each end and then you let whatever is left over hang down. Just
don't let the ends reach close enough to the ground where someone could
reach them. Shock and RF burns.

If you go to the 100 feet and feed it with open wire , you are trying to
make the antenna into a g5rv if you use whatever length of feedline the g5rv
calls for. Not really that good of an antenna for working all bands.

Doublet Antenna question
 

Ed wrote:
My QUESTION(s): How effective would a balanced fed dipole of about
100 feet length be on 75M ?

Make it 102 ft. and you will have the G5RV length about which
virtually everything in the world is known. It works so well
on 75m that you should not be able to notice the difference.
How easy/hard it is to match will depend upon the feedline
length.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

On Sun, 16 Oct 2005 18:28:36 GMT, Ed
wrote:



My QUESTION(s): How effective would a balanced fed dipole of about
100 feet length be on 75M ? Should it tune OK with a tuner such as the
new MFJ balanced tuner? Or, if I were to put either the old 40M traps,
or wind coils for the new dipole to shorten 75M resonance, would it then
tune OK on all bands from 75M down with balanced feed?

Ed,

When you analyse the performance of a centre fed dipole antenna
system, you will find that for most practical dipoles, the challenge
is getting most of the power to the feed point, rather than the ohmic
losses in the radiator itself.

By the time the dipole is long enough to obtain acceptable performance
from a practical feed system, the loss in the radiator itself is
typically less than 0.5dB (unless you contrive do something pretty
silly).

It turns out that it becomes quite challenging to implement an
efficient feed system (especially over a wide frequency range) where
the dipole is less than about 35% of a wavelength at the lowest
frequency.

Now, the 100' you nominate is so close to the length of a G5RV that
you could draw some information from analyes of the G5RV. I wrote one
that focusses on the performance of common distortions of G5RV's
design and examines particularly the feed system performance, which I
suggest to you is the most significant influence on antenna system
efficiency in this case. Unlike many other analyses of the G5RV, this
does not just consider ham band performance, it models performance
every 100KHz from 1MHz to 30MHz, so you can see a continuous view of
the behaviour. The article is at http://www.vk1od.net/G5RV/ .

But you weren't asking about a G5RV were you. Look at Figure 10 and
the "Classic tune feeder" topic which is a 30m dipole fed with 23m of
ideal 600 ohm open wire feeder. (Ladder line won't perform quite that
well, especially when wet). That topic is directly relevant to your
proposal.

Nothing in the feed system affects the pattern (in three dimensions),
that is determined by the length of the dipole, and its environment.

Owen
--

Doublet Antenna question
 

On Sun, 16 Oct 2005 21:20:22 GMT, Owen Duffy wrote:

On Sun, 16 Oct 2005 18:28:36 GMT, Ed
wrote:



My QUESTION(s): How effective would a balanced fed dipole of about
100 feet length be on 75M ? Should it tune OK with a tuner such as the
new MFJ balanced tuner? Or, if I were to put either the old 40M traps,
or wind coils for the new dipole to shorten 75M resonance, would it then
tune OK on all bands from 75M down with balanced feed?

Ed,

When you analyse the performance of a centre fed dipole antenna
system, you will find that for most practical dipoles, the challenge
is getting most of the power to the feed point, rather than the ohmic
losses in the radiator itself.

By the time the dipole is long enough to obtain acceptable performance
from a practical feed system, the loss in the radiator itself is
typically less than 0.5dB (unless you contrive do something pretty
silly).

It turns out that it becomes quite challenging to implement an
efficient feed system (especially over a wide frequency range) where
the dipole is less than about 35% of a wavelength at the lowest
frequency.

Now, the 100' you nominate is so close to the length of a G5RV that
you could draw some information from analyes of the G5RV. I wrote one
that focusses on the performance of common distortions of G5RV's
design and examines particularly the feed system performance, which I
suggest to you is the most significant influence on antenna system
efficiency in this case. Unlike many other analyses of the G5RV, this
does not just consider ham band performance, it models performance
every 100KHz from 1MHz to 30MHz, so you can see a continuous view of
the behaviour. The article is at http://www.vk1od.net/G5RV/ .

But you weren't asking about a G5RV were you. Look at Figure 10 and
the "Classic tune feeder" topic which is a 30m dipole fed with 23m of
ideal 600 ohm open wire feeder. (Ladder line won't perform quite that
well, especially when wet). That topic is directly relevant to your
proposal.

Nothing in the feed system affects the pattern (in three dimensions),
that is determined by the length of the dipole, and its environment.


Hmmm.

Duffy (http://www.vk1od.net/G5RV/) says, see Cebik
(http://www.cebik.com/wire/g5rv.html)

Cebik (http://www.cebik.com/wire/g5rv2.html) says, see Duffy
(http://www.vk1od.net/G5RV/)


I'm going around in circles. :-)

Doublet Antenna question
 

On Sun, 16 Oct 2005 16:21:31 -0700, Wes Stewart
wrote:


Hmmm.

Duffy (http://www.vk1od.net/G5RV/) says, see Cebik
(http://www.cebik.com/wire/g5rv.html)

Cebik (http://www.cebik.com/wire/g5rv2.html) says, see Duffy
(http://www.vk1od.net/G5RV/)


I'm going around in circles. :-)

Wes,

A bit of mutual citation, bit obvious isn't it when there isn't some
indirection like a few intermediate authors / articles!

Nevertheless, LB Cebik deals more with patterns, and I deal more with
the feed system, and of course the big picture means considering them
both. I happily link to LB for people to read some useful info on the
other aspect. Is that too cosy for you?

More importantly, if you found any faults with my analysis, let me
know?

Owen
--

Doublet Antenna question
 

Ed wrote:
My QUESTION(s): How effective would a balanced fed dipole of
about
100 feet length be on 75M ?

Make it 102 ft. and you will have the G5RV length about which
virtually everything in the world is known. It works so well
on 75m that you should not be able to notice the difference.
How easy/hard it is to match will depend upon the feedline
length.


Thank you, Cecil. Very few here responded to my questions the way I
had hoped, although there was some very good info in those responces.

I had wondered what the effect of inductance in the dipole legs would
have on a balanced fed antenna. It now appears that to get decent
results on 75M I don't need to do that, anyway.

I had not thought much about adding dropping wires to the ends of my
dipole legs, as one fellow suggested, because the trees are so conical
shaped that their lower branches would likely be in the way of the
vertical wires coming down off the ends.

I guess I need to research the G5RV antenna. Someone else here
posted a nice URL to a site on it and I will be perusing it more.

Cecil, I definitely can make my dipole 102 feet accross the top. I
am guesstimating that I will need approximately 35 or 40 feet of feedline
from the shack to the feedpoint. Do you see any issues with that?

Ed K7AAT

Doublet Antenna question
 

If those bands on the old antenna were already resonant, and they
matched, then you didn't need 450 Ohm ladder line.

If you are going to use 450 Ohm ladder line on a generic doublet, it
stands to reason you won't be resonant much anywhere (or you don't
count on it) and you anticipate tuning and use this line for low loss.

Thanks, Richard.

My main concern was that trying to tune a 100 foot dipole on 75M
might cause problems due to the dipole being shorter than halfwave on
75M. From what I am now concluding from your comments, and others',
this probably won't be an issue?


Ed

Doublet Antenna question
 

).

It turns out that it becomes quite challenging to implement an
efficient feed system (especially over a wide frequency range) where
the dipole is less than about 35% of a wavelength at the lowest
frequency.

Yes, my 100 foot length would be about 42% ofthe wavelength of my
lowest operating band, 75M.... perhaps it wouldn't be any problem for my
cheap MFJ balanced line tuner to feed it?

I appreciate your comments. I'm off shortly to study the website you
pointed me to. Thanks.


Ed K7AAT

Doublet Antenna question
 

On Mon, 17 Oct 2005 02:48:13 GMT, Ed
wrote:

My main concern was that trying to tune a 100 foot dipole on 75M
might cause problems due to the dipole being shorter than halfwave on
75M. From what I am now concluding from your comments, and others',
this probably won't be an issue?

Hi Ed,

An antenna can be too long, an antenna can be too short. Somewhere
over the span of all the HF bands, one antenna qualifies for one of
those two conditions. The issue is can you cope?

A tuner can usually resolve the problem of match, but it cannot do
anything about line loss for certain situations. Using the ladder
line answers that.

Finally, unless you demand the point shaving of eking out every tenth
dB for contesting, the combination of a 100 foot doublet, a tuner and
ladder line will give you just as good service as a tuned dipole.

73's
Richard Clark, KB7QHC

Doublet Antenna question
 

Ed wrote:
Cecil, I definitely can make my dipole 102 feet accross the top. I
am guesstimating that I will need approximately 35 or 40 feet of feedline
from the shack to the feedpoint. Do you see any issues with that?

That's a very good length for 40m, 17m, & 10m. You can analyze the
antenna yourself by downloading the free demo version of EZNEC
from www.eznec.com. If you want, I'll send you a model of your
antenna so all you have to do is click the mouse.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

Ed wrote:
My main concern was that trying to tune a 100 foot dipole on 75M
might cause problems due to the dipole being shorter than halfwave on
75M. From what I am now concluding from your comments, and others',
this probably won't be an issue?

Walter Maxwell of "Reflections" fame recommends a minimum length
for a dipole of 3/8 wavelength. 102 ft is 3/8 wavelength on
about 3.6 MHz so it should and does work well. That's the length
of my dipole.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

On Sun, 16 Oct 2005 23:45:42 GMT, Owen Duffy wrote:

On Sun, 16 Oct 2005 16:21:31 -0700, Wes Stewart
wrote:


Hmmm.

Duffy (http://www.vk1od.net/G5RV/) says, see Cebik
(http://www.cebik.com/wire/g5rv.html)

Cebik (http://www.cebik.com/wire/g5rv2.html) says, see Duffy
(http://www.vk1od.net/G5RV/)


I'm going around in circles. :-)

Wes,

A bit of mutual citation, bit obvious isn't it when there isn't some
indirection like a few intermediate authors / articles!

Nevertheless, LB Cebik deals more with patterns, and I deal more with
the feed system, and of course the big picture means considering them
both. I happily link to LB for people to read some useful info on the
other aspect. Is that too cosy for you?

Clearly you have missed the humo(u)r that I intended.


More importantly, if you found any faults with my analysis, let me
know?

To be honest, I didn't look at it closely enough to do any such thing.
You always to seem to be quite thorough, so I would not expect any
glaring errors.

Doublet Antenna question
 

Fred W4JLE wrote:
A G5RV would fit and meet your needs for all band operation with a tuner.

Hi Fred,
The standard G5RV is a pretty good antenna for 80m, 40m, 20m, & 12m.
Not bad on 15m, but the SWR on the coax for 30m, 17m, & 10m is
greater than 40:1 according to EZNEC.

I have optimized my G5RV for 40m, 17m, & 10m operation by making the
series balanced section 36 feet of 450 ohm ladder-line.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

Owen Duffy wrote:
The article is at http://www.vk1od.net/G5RV/ .

Owen, that's the best G5RV article I've ever seen. When
anyone has questions on the G5RV, I'm going to point them
to that article.

However, it does contain an error. You say:

" ... it ... does not have acceptable feed performance on
any WARC bands"

Yet your own SWR data shows a low SWR point at 25 MHz. The
G5RV actually has a lower SWR on the coax on 24.95 MHz
than it does on 21.3 MHz according to EZNEC.

Also, someone is preparing an article showing how length
selection of the "matching section" using relays can transform
the G5RV into a truly all-HF-band antenna requiring no tuner.
After that article is published, it would be nice if you
included that information in your article.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

Owen Duffy wrote:
More importantly, if you found any faults with my analysis, let me
know?

Just found one and replied to your posting. You and Cebik
seem to disagree about 12m where you say it won't work on
any WARC band and he says the impedance at the twinlead/coax
junction is "Resistive (90-100 Ohms)", i.e. SWR=2:1
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

No time to read all the other posts, but in short...


You are proposing a slightly shorter than 1/2 wave dipole for 75. This
should be no problem as it will have a little capacitive reactance and a
tuner should handle it.

The G5RV is pretty much the same thing, except it has some feed line
gymnastics to get a "fairly good" (50 ohm) match on many bands. This is
nothing more than an "antenna tuner in feed line" which doesn't require a
knob rather than one in a box which does. (:-)

My 40M dipole works on 30M as a slightly LONG dipole. [[ It also works on
75 as a really short one, but not too good]]

73, Steve, K,9.D;C'I


"Ed" wrote in message
. 93.175...
).

It turns out that it becomes quite challenging to implement an
efficient feed system (especially over a wide frequency range) where
the dipole is less than about 35% of a wavelength at the lowest
frequency.

Yes, my 100 foot length would be about 42% ofthe wavelength of my
lowest operating band, 75M.... perhaps it wouldn't be any problem for my
cheap MFJ balanced line tuner to feed it?

I appreciate your comments. I'm off shortly to study the website you
pointed me to. Thanks.


Ed K7AAT

Doublet Antenna question
 

On Mon, 17 Oct 2005 16:05:54 GMT, Cecil Moore wrote:

Owen Duffy wrote:
More importantly, if you found any faults with my analysis, let me
know?

Just found one and replied to your posting. You and Cebik
seem to disagree about 12m where you say it won't work on
any WARC band and he says the impedance at the twinlead/coax
junction is "Resistive (90-100 Ohms)", i.e. SWR=2:1

No, I said:

"Contrary to oft stated views, the Classic G5RV is not an all band
antenna, it:
* does not have acceptable feed performance on 1.8MHz;
* does not have acceptable feed performance on any WARC bands;
* does not have acceptable feed performance on 28MHz."

Two main factors were in my mind in determining whether performance
was "acceptable", they we
- the magnitude of the losses on this particular model in-band for the
band in question; and
- whether the losses changed rapidly on adjacent frequencies, such
that installations with small differences (eg height, earth parameters
etc) were not assured of acceptable losses.

For example, it is possible to tweak a G5RV a little to minimise the
feed losses on 10.1MHz, and they can be low enough, but it is a very
sharp notch and likely to be not realisable with seasonal changes in
soil moisture etc.

I have reviewed the specific case you mention about 25MHz. Two of the
feed arrangments are marginally under the criteria that I set, but
they are under it and for consistency they should have been included
in the "acceptable" category. Omitting them was an error on my part.

I have ammended the article accordingly Cecil, thanks for the
feedback.

It is important to keep in mind that the article is analysis of a set
of common feed configurations of a dipole at a specific height over
specific ground, and that the results may vary in other
configurations.

Owen
--

Doublet Antenna question
 

On Mon, 17 Oct 2005 05:27:08 -0700, Wes Stewart
wrote:


A bit of mutual citation, bit obvious isn't it when there isn't some
indirection like a few intermediate authors / articles!

....

Clearly you have missed the humo(u)r that I intended.


Wes, I did take it as light hearted, and hence my response above.

I am not an academic, nor do I have the experience of that university
environment, but I think there is probably more than a little humour
to be had from examples of self-citation, mutual-citation,
self-citation indirectly by n levels (more subtle than mutual
citation)... etc.

Thing that had my head spinning was trying to follow the logic (I use
the term loosely of course) of some recent threads.

Owen
--

Doublet Antenna question
 

Owen Duffy wrote:
I have ammended the article accordingly Cecil, thanks for the
feedback.

So one more myth is busted. You had me thinking that I was the
only one capable of making a mistake.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

You are proposing a slightly shorter than 1/2 wave dipole for 75.
This should be no problem as it will have a little capacitive
reactance and a tuner should handle it.

Thank you, Steve. This was my main concern.


The G5RV is pretty much the same thing, except it has some feed line
gymnastics to get a "fairly good" (50 ohm) match on many bands. This
is nothing more than an "antenna tuner in feed line" which doesn't
require a knob rather than one in a box which does. (:-)

I have pretty much decided to just feed ladder line with a balanced
tuner rather than make a G5RV. This should give me more flexibility.


Ed

Doublet Antenna question
 

That's a very good length for 40m, 17m, & 10m. You can analyze the
antenna yourself by downloading the free demo version of EZNEC
from www.eznec.com. If you want, I'll send you a model of your
antenna so all you have to do is click the mouse.


Thanks for the offer, Cecil, but at this time I will decline. I plan
on just putting up as much wire as I can effectively mount between the
two trees, about 100 feet, and just feed it at the center with ladder
line. A new balanced tuner will tune the whole thing. I expect this to
give me a bit more flexibility than the G5RV would.


Ed K7AAT

Doublet Antenna question
 

Ed wrote:
Thanks for the offer, Cecil, but at this time I will decline. I plan
on just putting up as much wire as I can effectively mount between the
two trees, about 100 feet, and just feed it at the center with ladder
line.

That's the antenna I was offering to model for you. You will,
no doubt, run into some pitfalls, for instance an impedance
of 8 ohms or 4000 ohms that your tuner may not be able to handle.
EZNEC can predict such problems before they bite you.

As a data point, the MFJ-974 gives you a matching range of 12-2000
Ohms.

EZNEC can also predict your radiation patterns which are important
on the high bands if you want to hit certain areas of the world.
Rotating my dipole in AZ by 15 degrees made a lot of difference.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

On Tue, 18 Oct 2005 03:18:39 GMT, Cecil Moore wrote:

Ed wrote:
Thanks for the offer, Cecil, but at this time I will decline. I plan
on just putting up as much wire as I can effectively mount between the
two trees, about 100 feet, and just feed it at the center with ladder
line.

That's the antenna I was offering to model for you. You will,
no doubt, run into some pitfalls, for instance an impedance
of 8 ohms or 4000 ohms that your tuner may not be able to handle.
EZNEC can predict such problems before they bite you.

As a data point, the MFJ-974 gives you a matching range of 12-2000
Ohms.

EZNEC can also predict your radiation patterns which are important
on the high bands if you want to hit certain areas of the world.
Rotating my dipole in AZ by 15 degrees made a lot of difference.

For any given frequency, would that 8 ohms or 4000 ohms be decided by
the length of the dipole or the length of the ladderline, or both?

bob
k5qwg

Doublet Antenna question
 

Bob Miller wrote:
For any given frequency, would that 8 ohms or 4000 ohms be decided by
the length of the dipole or the length of the ladderline, or both?

Both. For instance the resonant impedance of a G5RV on the lower
part of 80m is usually about 8 ohms. If the feedline for a one
wavelength dipole is 1/2WL, the impedance will be about 4000 ohms.
The feedline impedance seen by your tuner is somewhat unpredictable
and EZNEC can tell you what ballpark impedance to expect. EZNEC
has saved me an enormous amount of time - 10 minutes of simulation
Vs 10 hours of antenna erection time.
--
73, Cecil http://www.qsl.net/w5dxp

Doublet Antenna question
 

The loss in a switched transmission line tuner is somewhat greater
than in a conventional tuner which can be adjusted for an exact,
low-loss, impedance match.
---
Reg.

Doublet Antenna question
 

That's the antenna I was offering to model for you. You will,
no doubt, run into some pitfalls, for instance an impedance
of 8 ohms or 4000 ohms that your tuner may not be able to handle.
EZNEC can predict such problems before they bite you.

OK. I'll take you up on the offer, afterall. Figure 100' of #14
copperweld, centerfed with 450ohm ladderline or with 600 ohm open wire
line (2"). Height should be about 45' at ends and 35 feet center.
Length of feedline is projected at about 45 feet.

I'll go with the 600 ohm wireline feed if I can find it, otherwise,
the cheap 450 ohm plastic stuff for now and build wireline next summer.



EZNEC can also predict your radiation patterns which are important
on the high bands if you want to hit certain areas of the world.
Rotating my dipole in AZ by 15 degrees made a lot of difference.

Not real concerned with the patterns of anything above 40M. I'm
mainly interested in 80/75/60/40M use. I'll take what I get and see
how it goes..... might be nice to see 20M and 10M patterns, though.
Thanks.


Ed

Doublet Antenna question
 

600 ohm open wire line is available from W7FG [800-807-6146].

50 feet $23
100 feet $40.

I've used it for years at the KW level. No problems.

I'm just a satisfied customer and have no financial interest in their
business.



Ed wrote:

That's the antenna I was offering to model for you. You will,
no doubt, run into some pitfalls, for instance an impedance
of 8 ohms or 4000 ohms that your tuner may not be able to handle.
EZNEC can predict such problems before they bite you.


OK. I'll take you up on the offer, afterall. Figure 100' of #14
copperweld, centerfed with 450ohm ladderline or with 600 ohm open wire
line (2"). Height should be about 45' at ends and 35 feet center.
Length of feedline is projected at about 45 feet.

I'll go with the 600 ohm wireline feed if I can find it, otherwise,
the cheap 450 ohm plastic stuff for now and build wireline next summer.



EZNEC can also predict your radiation patterns which are important
on the high bands if you want to hit certain areas of the world.
Rotating my dipole in AZ by 15 degrees made a lot of difference.


Not real concerned with the patterns of anything above 40M. I'm
mainly interested in 80/75/60/40M use. I'll take what I get and see
how it goes..... might be nice to see 20M and 10M patterns, though.
Thanks.


Ed

Doublet Antenna question
 

600 ohm open wire line is available from W7FG [800-807-6146].

50 feet $23
100 feet $40.


Thanks. I've noted the number (what an interesting set up numbers!),
and will call in a few weeks when I'm ready to order.


Ed