Mark Keith wrote:
I think it would *still* probably slightly beat your antenna. I'm fairly
certain even your G5RV will not be a complete equal to my coax fed
dipole.

But you, yourself, have admitted that the difference is negligible. It
is indeed around 0.4 dB according to all my calculations. And the reward
is that one gets eight antennas for the price of one, i.e. 8 HF band coverage.
If you were feeding your 75m dipole with ladder-line, I wouldn't have nearly
as strong an argument.

Myself, I think multiband 102 ft dipoles should be fed only with ladder
line...Why are you not using your cut ladder line method for G5RV's?
Enquiring minds wanna know...:/

Because it is so easy to achieve nearly a 50+j0 ohm feedpoint impedance at
the series section to coax junction. It is actually relatively difficult
to achieve nearly a 50+j0 ohm impedance using my variable length ladder-
line scheme at the operating position with a 102 foot dipole. But it is
easy with a 130 foot dipole. I simply got tired of the bad rap you and
others were giving G5RVs and chopped my 130 foot dipole to 102 feet. Now
you have to suffer the consequences. :-) What I am trying to demonstrate
is how series matching section transformers work not just at 1/4WL and
1/2WL but at many other lengths.

Why would someone prefer a G5RV over
your normal 80m size all band ladder line fed antenna for FD on 80m?
Enquiring minds wanna know that too...:}

Many hams cannot string a 130 foot dipole but can manage a 102 foot dipole.
I've pushed the 130 foot dipole for years. Now I'm pushing the 102 foot
dipole. Sorry if that is politically incorrect. I simply cannot stand by
and allow new old wives' tales to take over ham radio.
--
73, Cecil, W5DXP



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Cecil Moore wrote in message ...
Brian Kelly wrote:
I've read the whole thread thru Tuesday AM, I get your point . .
. . . see if it's possible to cover that range with some
single specific length of ladderline and the two-section BC variable
cap? If yes I think you have a real keeper idea.

Maybe you'll like this one. 110 ft dipole at 40 ft, fed with 110 ft of
450 ohm ladder-line and tuned with a single control dual-gang variable cap,
i.e. no conventional antenna tuner.

.. . . OK but 110 feet of feedline to an antenna at 40 feet is a whole
lot of feedline to deal with under normal installation condx. At least
around here in suburbia.

Such an antenna system covers the entire
75-80m band with a 50 ohm SWR ranging from 1.7 at 3.5 MHz to 1.0 at 4.0 MHz,
according to EZNEC. Full band coverage at the twist of one knob? You likeie?

Sure do, could be extremely useful, I've moved it into my "idea book".
It's an easily tunable 80/75 variation on the similar antennas in your
website.

For a coax fed dipole, EZNEC reports an SWR=2:1 bandwidth of 170 kHz.

That's roughly what I get with with Nec-Win-Plus. If I make the dipole
131 feet long I get the following SWRs:

3.50 Mhz = 3.2
3.65 Mhz = 1.5 (curve min point)
3.80 Mhz = 3.5
4.00 Mhz = 4.7

So it's not possible to get much bandwidth across 80/75 with a simple
dipole without an ATU no matter how you diddle it. Then you're down to
a low-loss tuning scheme like you've come up with which in this case
is a complete no-brainer. IF one can figure out to what to do with all
the excess feedline without messing it up.

w3rv

Brian Kelly wrote:
. . . OK but 110 feet of feedline to an antenna at 40 feet is a whole
lot of feedline to deal with under normal installation condx. At least
around here in suburbia.

Hey, but not for field day. Whoever heard of a "field" with no room for
110 feet of feedline?

IF one can figure out to what to do with all
the excess feedline without messing it up.

It can be coiled into a big helix as long as the adjacent coils are
a couple of feet apart. You can run an insulated rope to the antenna
feedpoint and coil the ladder-line on the rope with the coils tiewrapped
a couple of feet apart. At the least you would have a conversation piece
to discuss over 807s (the best part of field day. :-) A photo of it would
probably make it into QST since it looks somewhat like a slinky. ;-)
--
73, Cecil, W5DXP



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Cecil Moore wrote:

Mark Keith wrote:
I think it would *still* probably slightly beat your antenna. I'm fairly
certain even your G5RV will not be a complete equal to my coax fed
dipole.

But you, yourself, have admitted that the difference is negligible.

Thats only between mine and yours, and IF your's works as advertised. In
the real world, I have never seen this happen yet. Heck, in theory,
there should be no real difference in using a coax fed 80m dipole, and a
80 dipole fed with my tuner, and ladder line. Using the bare min
inductance of course... In theory, there should not be enough difference
to notice. In theory...So far in the real world, it hasn't worked that
way for me. I saw a noticable difference. Probably about 5 db's worth if
using strong signals in the upper part of an S meters range. Now, in
that case, the loss was quite livable for just average use. It wasn't
near as bad the the G5RV's we used. The feedline loss in THOSE
PARTICULAR G5RV's was quite large on 80m. I actually had quite a bit of
trouble even contacting many other stations. Led to hair loss...

It
is indeed around 0.4 dB according to all my calculations. And the reward
is that one gets eight antennas for the price of one, i.e. 8 HF band coverage.
If you were feeding your 75m dipole with ladder-line, I wouldn't have nearly
as strong an argument.

Myself, I think multiband 102 ft dipoles should be fed only with ladder
line...Why are you not using your cut ladder line method for G5RV's?
Enquiring minds wanna know...:/

Because it is so easy to achieve nearly a 50+j0 ohm feedpoint impedance at
the series section to coax junction. It is actually relatively difficult
to achieve nearly a 50+j0 ohm impedance using my variable length ladder-
line scheme at the operating position with a 102 foot dipole. But it is
easy with a 130 foot dipole. I simply got tired of the bad rap you and
others were giving G5RVs and chopped my 130 foot dipole to 102 feet. Now
you have to suffer the consequences. :-)

How's that? If you change it, it's not quite the usual "g5rv" that I
complain about. It's a different antenna. Actually, I think calling it a
G5RV is silly unless it's used as a 20m monoband antenna as was
originally designed. The G5RV's I saw were really bad on 80m. It's not
just something I'm making up. I was so disgusted with the things after
the 2nd FD, I refused to ever use one again. And I haven't. I bring my
own wire and coax just to make sure I don't get stuck on one. And I
wasn't the only one complaining either...
I won't be suffering with a system efficiency in the mid 90's...

What I am trying to demonstrate
is how series matching section transformers work not just at 1/4WL and
1/2WL but at many other lengths.

Well, thats fine. But I'm trying to tell everyone to live a little! Go
with gusto! You only spin once! Use a full size efficient, resonant,
antenna if you want manly 80m FD results and have the room for it. I
suppose being resonant should not really be an issue, but in this case
it is. It's hard to beat a 50 ohm antenna , fed with 50 ohm line, by a
50 ohm radio. To me, that is the "perfect" setup. It just so happens a
1/2 wave dipole lets all this fall into place. And it just happens that
a 1/2 wave dipole has a near optimum pattern for the usual FD type
operation on 80m. To me, anything else is like sticking a finger on the
perfect painting , and smearing it around before it's dry.. :/
I guess this is what led me to question your choice of the perfect FD
antenna. 80m, being the band of real issue.


Why would someone prefer a G5RV over
your normal 80m size all band ladder line fed antenna for FD on 80m?
Enquiring minds wanna know that too...:}

Many hams cannot string a 130 foot dipole but can manage a 102 foot dipole.

At field day? A lousy 15 more ft a side? Man, they need to find a better
place for field day...
Thats sad....
Here's where we were last
year...http://bvarc.freeshell.org/images/FD2003/index.html
No trouble stringing up a real dipole around that place..."It's a fire
training facility in Richmond Tx."
Note my portable tower and beam I bring on a motorcycle trailer. Thats
why I fear you not on the upper bands.... BTW...My tower was the
lowest, but the highest scoring...Due mainly to superior operating
skills though...No, not by me...:/ I didn't use it...Blame N5XZ...
There are other beams also... If I were to FD by myself, I'd drive down
to the beach and operate off the salt water.
Probably could just sit in the truck and use the mobile setup...
Wouldn't need to get out and do any actual work... :/

I've pushed the 130 foot dipole for years. Now I'm pushing the 102 foot
dipole. Sorry if that is politically incorrect. I simply cannot stand by
and allow new old wives' tales to take over ham radio.

I like your all ladder line design better from an efficiency
standpoint...But claiming a coax fed dipole is nearly invincable as far
as wire ant/dipole efficiency's go, is hardly a wives tail. MK
--
http://web.wt.net/~nm5k

Cecil Moore wrote in message ...

Brian Kelly wrote:
. . . OK but 110 feet of feedline to an antenna at 40 feet is a whole
lot of feedline to deal with under normal installation condx. At least
around here in suburbia.

Hey, but not for field day. Whoever heard of a "field" with no room for
110 feet of feedline?

Well . . it sorta "depends". In the instant case the FD "field" is one
of my daughters' 1/4 acre back yard, three decent-size hardwoods
spread out in maybe a 120 foot straight line and that's it. The other
op will probably be N2EY and he isn't into deep bush ops either.

IF one can figure out to what to do with all
the excess feedline without messing it up.

It can be coiled into a big helix as long as the adjacent coils are
a couple of feet apart. You can run an insulated rope to the antenna
feedpoint and coil the ladder-line on the rope with the coils tiewrapped
a couple of feet apart.

That's slick.

At the least you would have a conversation piece
to discuss over 807s (the best part of field day. :-) A photo of it would
probably make it into QST since it looks somewhat like a slinky. ;-)

I was thinking more along the lines of sniping one of the orange
barrels which are the Pennsylvania State Flower. They're quite readily
available at construction sites along the PA Turnpike and
slinky-wrapping feedline around one of those should do the job.

Let's see here, 2.5 feet diameter times Pi . . 7.85398 feet per wrap .
.. yeah, that would get rid of most of the ladderline. At worst maybe
I'd need a couple of 'em in series.

QRX for the QST cover shot.

w3rv

Mark Keith wrote:
I was so disgusted with the things after
the 2nd FD, I refused to ever use one again. And I haven't. I bring my
own wire and coax just to make sure I don't get stuck on one. And I
wasn't the only one complaining either...
I won't be suffering with a system efficiency in the mid 90's...

It would be easy to try my G5RV modification. For 3.8 MHz, it is
25 ft of "450" ladder-line with a 1000 pf cap in parallel at the
ladder-line/coax junction. I wish you would open your closed mind
and try it sometime.

I guess this is what led me to question your choice of the perfect FD
antenna. 80m, being the band of real issue.

A perfect FD antenna would allow one to change bands relatively
quickly without sacrificing performance. My G5RV does that.

The 110 ft dipole that I came up with has an SWR of less than 1.7:1
over the entire 75-80m band. That sure beats the bandwidth of a
resonant coax-fed dipole.

W5DXP wrote:
Many hams cannot string a 130 foot dipole but can manage a 102 foot dipole.

At field day?

No, at their QTH. Many hams have reported that they just don't have
130 feet of room.

I simply cannot stand by
and allow new old wives' tales to take over ham radio.

I like your all ladder line design better from an efficiency
standpoint...But claiming a coax fed dipole is nearly invincable as far
as wire ant/dipole efficiency's go, is hardly a wives tail. MK

That's not the old wives' tale. The old wives' tale is, "A G5RV
is a terrible antenna that cannot be improved to near perfection."
With minor modifications, a G5RV will compete favorably with any
other HF dipole on any HF band.
--
73, Cecil, W5DXP



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Cecil Moore wrote in message ...
Brian Kelly wrote:
. . . OK but 110 feet of feedline to an antenna at 40 feet is a whole
lot of feedline to deal with under normal installation condx. At least
around here in suburbia.
.. . . .

Cecil check me here if you will. I brought up a CAD program to sketch
your 80/75 dipole and ran into a puzzler as soon as I started to draw
it. Center fed 110' flattop, 110' balanced feedline. No problem. The
question arose when I tried to lay in the tuning caps. My
understanding is that the "input" sides of the two caps are connected
to each of the two wires at the "output" end of the feedline. Then the
"output" side of one cap goes to the shield of the coax and the output
side of the other cap goes to the center conductor of the coax. This
is not possible with a typical double-section variable BC-type cap
because one side of such caps is a common ("ground"). A pair of caps
mechanically coupled via an insulated shaft coupling but completely
isolated electrically from each other should work. Where's the
glitch??

w3rv

(Brian Kelly) wrote in message . com...
Cecil Moore wrote in message ...

Brian Kelly wrote:
. . . OK but 110 feet of feedline to an antenna at 40 feet is a whole
lot of feedline to deal with under normal installation condx. At least
around here in suburbia.

Hey, but not for field day. Whoever heard of a "field" with no room for
110 feet of feedline?

All depends on the situation. Last thing ya need on FD is more
complications.
Which is why I've gone with coax-fed dipoles on FD for years.

The books give all sorts of figures for "open wire line". But many of
them are for the classic lines made of #14 copper spaced 4 to 6 inches
with ceramic spreaders every few feet. Brown poly TV twin lead with
rectangular holes punched in it is a whole 'nother ball game.
'Specially at high SWRs and when it's wet. Which may not be a
consideration in NTX but is a big consideration in EPA.

Well . . it sorta "depends". In the instant case the FD "field" is one
of my daughters' 1/4 acre back yard, three decent-size hardwoods
spread out in maybe a 120 foot straight line and that's it. The other
op will probably be N2EY and he isn't into deep bush ops either.

I'll do deep bush ops anytime the opportunity presents itself. But
this isn't one of those times.

IF one can figure out to what to do with all
the excess feedline without messing it up.

It can be coiled into a big helix as long as the adjacent coils are
a couple of feet apart. You can run an insulated rope to the antenna
feedpoint and coil the ladder-line on the rope with the coils tiewrapped
a couple of feet apart.

That's slick.

Until the rain falls or the wind blows or somebody walks into it in
the dark.

Biggest headache, though, is switching the various lengths for
different bands.

At the least you would have a conversation piece
to discuss over 807s (the best part of field day. :-) A photo of it would
probably make it into QST since it looks somewhat like a slinky. ;-)

I was thinking more along the lines of sniping one of the orange
barrels which are the Pennsylvania State Flower. They're quite readily
available at construction sites along the PA Turnpike and
slinky-wrapping feedline around one of those should do the job.

Would solve the walking-into-it problem too.

Let's see here, 2.5 feet diameter times Pi . . 7.85398 feet per wrap .
. yeah, that would get rid of most of the ladderline. At worst maybe
I'd need a couple of 'em in series.

QRX for the QST cover shot.

If it were me, (which it ain't) I'd either go with a coax fed parallel
or trapper.

Or build a nice split-coil balanced tuner and run the ladder line
right to the tuner. Real ladder line, or at worst that "fretline"
stuff (which I have squirreled away). Lessee, I got the splitstator
cap, and some nice coil forms, and a smaller cap for the link. Oh
yeah, some real all-copper alligator clips for the taps....

Or do it AG6K style.

--

The big question for any FD antenna is "how many QSOs"? All the
simulations and Smith charts don't count for any points - QSOs do. My
personal best is 629 QSOs with one 100W rig, one op, one mode, three
bands and two antennas. Coax fed trapper set up as inverted V for
80/40, quarter wave groundplane elevated 5 feet with 8 sloping radials
for 20.

Anybody here beat that on FD with only dipoles and verticals?

73 de Jim, N2EY

Brian Kelly wrote:
A pair of caps
mechanically coupled via an insulated shaft coupling but completely
isolated electrically from each other should work.

Yes, that's what I had in mind. Mine are side-by-side with a
non-conducting fiber-chain connecting the shafts. Same with my
two rotary coils. When I said "dual-ganged", I meant mechanically
ganged, not electrically ganged.

| |/
Coax center wire--------|/|--------feedline--------
/| |
ganged variable caps to dipole
| |/
Coax braid--------------|/|--------feedline--------
/| |

And of course, there needs to be a choke between the coax and
the caps.
--
73, Cecil, W5DXP

N2EY wrote:
Biggest headache, though, is switching the various lengths for
different bands.

No switching the various lengths on this one, Jim. Just a 110 ft
dipole fed with about 110 ft of fixed length ladder-line with two
series variable caps as the one knob tuner. Covers from 3.5 MHz to
4.0 MHz with an SWR less than 1.7:1 and no lossy coils needed.
--
73, Cecil, W5DXP