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

).

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

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

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

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

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.

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

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

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

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