Any experience with the G5RV multiband wire antenna?
 

The G5RV antenna can be found by googling. Anyone using this
arrangement. It uses a coax feed to balanced feed (which variously acts
as radiating elements, depending on the band). The author says a balun
is not needed but then describes an RF choke that sounds a lot like a
balun. I am also concerned about TVI with this system.

John

Any experience with the G5RV multiband wire antenna?
 

jawod wrote:
The G5RV antenna can be found by googling. Anyone using this
arrangement. It uses a coax feed to balanced feed (which variously acts
as radiating elements, depending on the band). The author says a balun
is not needed but then describes an RF choke that sounds a lot like a
balun. I am also concerned about TVI with this system.

http://www.cebik.com/wire/g5rv.html

http://www.vk1od.net/G5RV/
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

jawod wrote:

The G5RV antenna can be found by googling. Anyone using this
arrangement. It uses a coax feed to balanced feed (which variously acts
as radiating elements, depending on the band). The author says a balun
is not needed but then describes an RF choke that sounds a lot like a
balun. I am also concerned about TVI with this system.

John


I'm not crazy about them at all. I'm not a fan
of switching feedline types midroute to the antenna.
This applies to other antennas as well. The G5RV
was designed mainly as a 20 meter antenna. I'm
not sure who decided it was the magical platform
for a multiband antenna, but someone did...
Someone should get a rope I think... :/
You would be much better ditching the coax and
choke, and running straight ladder line, if feeding
all bands with a tuner. I think coax fed antennas
should see a proper match at the feedpoint of
the antenna. If I'm going to use coax, I'm going to
run coax the whole way.
Some run the "carolina" windoms the same way pretty
much.. :( I've directly tested simple coax fed
dipoles against both of these antennas. It was
fairly ugly. The simple dipole thrashed both of them
handily. There is a good bit of loss in all that
feedline clutter. Some bands worse than others.
If you are going to run a tuner and ladder line for
all band use, a simple dipole on the lowest band
to be used is a fairly decent compromise. No need
to add excess feedline clutter. And loss. :(
If you use ladder line all the way, and tune carefully
using the least inductance, you will have a
fairly efficient system on most all the bands.
Most tuners include a 4:1, but some prefer a 1:1
balun instead.
MK



--
http://web.wt.net/~nm5k

Any experience with the G5RV multiband wire antenna?
 

To summarise - dump it !

Any experience with the G5RV multiband wire antenna?
 

The choke balun is used because the G5RV is fed with balanced line. They
work well, last a long time and require a tuner. I have never had any TVI
with one, nor did I ever expect any.

"jawod" wrote in message
...
The G5RV antenna can be found by googling. Anyone using this
arrangement. It uses a coax feed to balanced feed (which variously acts
as radiating elements, depending on the band). The author says a balun
is not needed but then describes an RF choke that sounds a lot like a
balun. I am also concerned about TVI with this system.

John

Any experience with the G5RV multiband wire antenna?
 

If SETUP right , There the best HF I've ever used.

Any experience with the G5RV multiband wire antenna?
 

Ricke wrote:
If SETUP right , There the best HF I've ever used.

Maybe the only one? :-) The G5RV, with tuner, is a pretty
good 80m, 40m, 20m, and 12m antenna. If the series section
is varied from 20 feet to 36 feet, it becomes a very good
all-HF-band antenna. With the addition of a parallel 1000pf
capacitor with the series section at 22 feet, on 75m my "G5RV"
has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Hi John,

The "Center Feeded Dipole" (feeding with twin-leads) would give you better
performances and no TVI.

But if you prefer the G5RV do not use any balun (with magnetic stuff). In
somme cases, baluns brings losses (if high SWR on the line). You may find
many people that will say that their G5RV works perfectly well with a balun
..... they are lucky !!!
It is better to connect the coax directly to your antenna tuner.

Good luck

Jean-Marc
F4DRH
www.barbaxoops.com






"jawod" a écrit dans le message de news:
...
The G5RV antenna can be found by googling. Anyone using this arrangement.
It uses a coax feed to balanced feed (which variously acts as radiating
elements, depending on the band). The author says a balun is not needed
but then describes an RF choke that sounds a lot like a balun. I am also
concerned about TVI with this system.

John

Any experience with the G5RV multiband wire antenna?
 

F4DRH wrote:
Hi John,

The "Center Feeded Dipole" (feeding with twin-leads) would give you better
performances and no TVI.

But if you prefer the G5RV do not use any balun (with magnetic stuff). In
somme cases, baluns brings losses (if high SWR on the line). You may find
many people that will say that their G5RV works perfectly well with a balun
.... they are lucky !!!
It is better to connect the coax directly to your antenna tuner.

Good luck

Jean-Marc
F4DRH
www.barbaxoops.com






"jawod" a écrit dans le message de news:
...

The G5RV antenna can be found by googling. Anyone using this arrangement.
It uses a coax feed to balanced feed (which variously acts as radiating
elements, depending on the band). The author says a balun is not needed
but then describes an RF choke that sounds a lot like a balun. I am also
concerned about TVI with this system.

John



Thanks to all for advice!

It seems likely that, as I re-enter ham radio, I will be using a rig
with an SO-239 plug as an output. The unit I am considering has an
internal ATU. So, it would appear likely that SOME coax will be used.
I've read articles that indicate a simple PVC pipe wound with 20 or so
turns of coax is sufficient for a coax to dipole configuration.

I guess I am trying to have a multiband dipole antenna that uses the
low-loss ladder line as part of the antenna on some bands. This seems
consistent with the G5RV.

Any thoughts on other designs to accomplish this? Many articles seem to
steer clear of series traps in the dipole. I must have TVI as a high
potential concern..

Anyway THANKS!

Jean-Marc: nice antenna system...your twin lead looks like coax...is it?

john

Any experience with the G5RV multiband wire antenna?
 

Jean-Marc: nice antenna system...your twin lead looks like coax...is it?

john

Hi John,

Here is my twin lead detail:
http://www.barbaxoops.com/modules/xc...&album=7&pos=2

.... and the twin lead installed on the center feed (click on picture to
enlarge):
http://www.barbaxoops.com/modules/xc...&album=7&pos=4
http://www.barbaxoops.com/modules/xc...&album=7&pos=4

The antenna tuner (MacCoy):
http://www.barbaxoops.com/modules/xc...&album=7&pos=0

Good luck

Jean-Marc
F4DRH
www.barbaxoops.com

Any experience with the G5RV multiband wire antenna?
 

Maybe the only one? :-) The G5RV, with tuner, is a pretty
good 80m, 40m, 20m, and 12m antenna.

Depends what you compare it to... I bet my paralleled
80/40/20 dipoles would beat it on all those bands.
Maybe even 12m. I'm not going to lose too awful much
even though I'm running 213 coax. You may have some
cases on the higher bands where the gain may be
better than the dipoles in some directions, but thats still
not a matter of efficiency.

If the series section
is varied from 20 feet to 36 feet, it becomes a very good
all-HF-band antenna. With the addition of a parallel 1000pf
capacitor with the series section at 22 feet, on 75m my "G5RV"
has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole.

You would be the exception to the rule. And I still really doubt
it's the total equal of a simple coax fed dipole on 80m.
The "usual" G5RV that most people tend to buy and run
is one of the most pathetic 80m antennas I've ever used
in my life. Truly a disgusting POC...:( I had the mispleasure
of being stuck on the G5RV at not one, but two field days
in a row. I'd never experienced working FD on a dummy
load until that time. I lost about 3 mm of tooth due to the
constant grinding of my teeth on those weekends.
After that, I *swore* I would never, ever, be stuck on
one of those things ever again. Never, nada, zilch.
Now, I've heard people that had fairly decent signals
with various perversions of the G5RV, but again, they
seem to modify them to work halfway well, and many
run amps, which also help them look a bit better than
they really are. If people want to run those, be my guest,
but keep them at least 500 yards from me. I'll be using
my usual coax fed dipoles.
This trails off to the "carolina" windoms that many people
run in the same appx manner.
Well, on the first FD after the two G5RV nightmares,
I brought all my own stuff to build dipoles on the spot.
I got to the FD, and the first antenna they suggested I
use was a carolina windom that was up in the air
pretty well. Maybe 50 ft up or more. It was fed with
the usual "clutter" and a tuner. "tuner/coax/choke/antenna.
I can't remember if any ladder line was involved on
that one...
Anyway, the first thing out of my mouth was *NO!!!!!".
I'll build a regular ole dipole, thanks, but no thanks.
Not trying to be rude, but I'd had my fill of dummy loads.
Anyway, I built a 40 meter dipole on the spot, and
threw it up in a different tree. It was actually lower
in height than the windom. I then brought out a coax
switch, and hooked both the windom, and the coax
fed dipole to the rig. Now, at first glance, you
would think the windom was doing all the good.
It was "working", and seemed to be just fine.
But then, I'd switch over to the dipole, and
*everything* would jump 2 S units on that radio.
All signals, noise floor, the whole shooting match.
The windom owner like to fell over. He had no
idea that he was taking that big a hit vs a simple
dipole. Needless to say, the windom wasn't used
after that test. People can run whatever they want,
but many have delusions that these "compromise"
clutter fed all band antennas are just as good as a
simple dipole. It's rarely the case by what I've seen.
Did you actually compare with a coax fed dipole
using a switch, etc? If not, saying it's equal is
just theory at this point. I'd have to see it to believe
it... :/ Heck, I see the difference from a properly fed
tuner/ladderline/dipole setup vs a coax fed dipole.
The coax fed always wins here by a slight amount.
As far as I'm concerned, a coax fed dipole is as good
as you can get in the real world on those lower bands as
far as system efficiency. In the 95+% bracket I think.
Your tunerless setup may be equal, but that's
not the usual setup for most people. Most use
a tuner also. I use the coax fed dipole as the benchmark
by which all others are measured on 80m. Most all lose,
unless they are a gain antenna like arrays or whatever.
Of course, with the dipoles on 80m, I'm usually talking
NVIS, or medium distances. I'm not a dxer much.
But...I had no problem at all taking to EU this past
winter on that dipole in the couple of times I tried
it down in the dx window. . No amp. I haven't run an amp
in 5 years. First call and solid copy too. I forgot where
they were. I think one on G land. One in Spain, germany,
etc..With just 90-100w from the 706. :) But a big NVIS
signal is really what I shoot for. Can't get much better
than a coax fed dipole or loop. Simple is best I think. :)
MK

Any experience with the G5RV multiband wire antenna?
 

wrote:

The G5RV, with tuner, is a pretty
good 80m, 40m, 20m, and 12m antenna.

Depends what you compare it to... I bet my paralleled
80/40/20 dipoles would beat it on all those bands.

Not by enough to notice on the other end. The G5RV has
a slight amount of gain over your 40m dipole. It has
low loss on the ladder-line matching section and an SWR
of less than 4:1 on the RG-213 coax. Where are the losses?

If the series section
is varied from 20 feet to 36 feet, it becomes a very good
all-HF-band antenna. With the addition of a parallel 1000pf
capacitor with the series section at 22 feet, on 75m my "G5RV"
has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole.

You would be the exception to the rule. And I still really doubt
it's the total equal of a simple coax fed dipole on 80m.

It's a 3/8WL dipole on 75m, fed with low-loss ladder-line,
a parallel door knob cap, and an SWR of 1.3:1 on the RG-213
coax. Where are the losses?

The "usual" G5RV that most people tend to buy and run
is one of the most pathetic 80m antennas I've ever used
in my life.

Well, maybe. The one I bought in 1988 was well designed with
a w2du balun and RG-8x coax. It worked well with a tuner and
I made lots of improvements as I learned more about it.

There was probably something wrong with the particular G5RV's
that you have been exposed to.

Some people run a 4:1 balun at the coax/twinlead junction on
a G5RV. That's the absolute worst thing to do on 75m as the
impedance at that point is already low at 16 ohms.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

If SETUP right , There the best HF I've ever used.


I agree ...... the only HF wire antenna I have ever used. You have to pay
close attention to the matching at 20m and then it works great. I use 300
ohm ladder line for the feed as I find that works the best. Build one and
try it out .......then you can see for yourself.


--
Bill Booth VE3NXK
Sundridge ON, Canada
79.23.37 W x 45.46.18 N
FN05ns

Visit my weather WebCam at http://www.almaguin.com/wxcurrent/weather.html

Any experience with the G5RV multiband wire antenna?
 

On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote:

Ricke wrote:
If SETUP right , There the best HF I've ever used.

Maybe the only one? :-) The G5RV, with tuner, is a pretty
good 80m, 40m, 20m, and 12m antenna. If the series section
is varied from 20 feet to 36 feet, it becomes a very good
all-HF-band antenna. With the addition of a parallel 1000pf
capacitor with the series section at 22 feet, on 75m my "G5RV"
has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole.

Now that is one of those things about a G5RV, no two are alike.

What are the key factors that "define" a G5RV? The things that I
recall from Varney's article we

- 31m long dipole
- centre fed
- flat top / inverted V
- open wire section of half wave length on 20m, from his physical
description, Zo about 520 ohms, but IIRC he suggests Zo is not
critical
- undefined length of either coax of open wire line of undefined, but
low Zo (50 - 120 ohms though he seemed to think figure 8 flex has a
lower Zo than it probably does).
- balun or no balun at the coax to open wire line transition,
depending on his article, he changed his mind.

My question is how many of these characteristics can be dispensed
with, or varied significantly and still legitimately speak of it as a
G5RV?

I am watching the argument between those who swear by a G5RV and those
who swear at a G5RV and suspect that one of the reasons (and not the
only reason) is they are not talking about the same thing.

There is a tendency to call anything with a ~30m centre fed dipole a
G5RV, and yet that component's pattern is independent of everything
else (excluding feedline radiation) and its efficiency is quite good
independently of everything else. It is "everything" else that
contains the losses that result from the dipole's feedpoint load
impedance, and it is the "everything else" that makes or breaks the
antenna.

Owen
--

Any experience with the G5RV multiband wire antenna?
 

Depends what you compare it to... I bet my paralleled
80/40/20 dipoles would beat it on all those bands.

Not by enough to notice on the other end.

So you say. If I can tell the difference between a tuner/
ladderline fed dipole vs a coax fed dipole, I bet I could
tell the difference. But I use the receiver, and switch
between the antennas. Much more accurate than
relying on reports.

The G5RV has a slight amount of gain over your 40m dipole.

That just means I'm almost sure to be louder in the
other two directions.. :/

It has
low loss on the ladder-line matching section and an SWR
of less than 4:1 on the RG-213 coax. Where are the losses?

At the ladderline/choke/coax junction I would suspect.



You would be the exception to the rule. And I still really doubt
it's the total equal of a simple coax fed dipole on 80m.

It's a 3/8WL dipole on 75m, fed with low-loss ladder-line,
a parallel door knob cap, and an SWR of 1.3:1 on the RG-213
coax. Where are the losses?

Does that version use the choke? Being the data is incomplete,
hard to say at this point. But if there is loss, I can probably
find it.. :/

The "usual" G5RV that most people tend to buy and run
is one of the most pathetic 80m antennas I've ever used
in my life.

Well, maybe. The one I bought in 1988 was well designed with
a w2du balun and RG-8x coax. It worked well with a tuner and
I made lots of improvements as I learned more about it.

Hummm...Does that mean it's not really a G5RV anymore?

There was probably something wrong with the particular G5RV's
that you have been exposed to.

No doubt about it.

Some people run a 4:1 balun at the coax/twinlead junction on
a G5RV. That's the absolute worst thing to do on 75m as the
impedance at that point is already low at 16 ohms.

I bet those did use a 4:1...Kinda makes sense as they were
the absolute worst wire antennas I'd ever used on 80m.
But like Owen points out, you have so many perversions
of the G5RV, it's hard to tell what is what. I *think* the
versions I used were made by the same company that
makes the carolina windoms, but not sure. I don't
really keep up with antennas I know I'll never be using.. :/
What boggles my mind is why people would want to use
a compromise antenna at a field day, when you have
enough room to fit 49 full size antennas... :/
Or at home for that matter.. If I have room for full size
antennas, I'm gonna use them. Life is too short for
compromise antennas. I guess I'm spoiled. I've never
had to run those funky things due to lot size, etc..
Even if I did, I think I could cook up something better
than the usual G5RV. Whatever I use will never mix
feedline types midroute to the antenna, I know that
for sure. It's like a crapshoot hoping things will pan
out at the junction. I couldn't live that way. :(
MK

Any experience with the G5RV multiband wire antenna?
 

Owen Duffy wrote:
My question is how many of these characteristics can be dispensed
with, or varied significantly and still legitimately speak of it as a
G5RV?

Well, with G5RV himself recommending ladder-line all the way
to the transmitter (ARRL Antenna Compendium #1) "If this form
(of the G5RV) is employed, almost any length (of balanced line)
may be used from center of the antenna to the matching network
(balanced) output terminals", the paintbrush is pretty broad.

I started out with a standard G5RV and modified it on a per
band basis to perform on all eight HF bands. 36 ft. of ladder-
line works on both 40m and 17m, my two favorite bands. When I
switch to 75m, I use 23 ft. of ladder-line with a parallel
1000pf cap. I call that the *PC-50* point, the point at which
a (P)arallel (C)apacitor will cause a match to (50) ohms.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

wrote:

W5DXP wrote:
It has
low loss on the ladder-line matching section and an SWR
of less than 4:1 on the RG-213 coax. Where are the losses?

At the ladderline/choke/coax junction I would suspect.

The only thing there that could be lossy would be the choke.
Why would a 1000 ohm choke be lossy?

It's a 3/8WL dipole on 75m, fed with low-loss ladder-line,
a parallel door knob cap, and an SWR of 1.3:1 on the RG-213
coax. Where are the losses?

Does that version use the choke? Being the data is incomplete,
hard to say at this point. But if there is loss, I can probably
find it.. :/

Yes, but the impedance at that point is very close to 50 ohms
and the choke has about 1000 ohms of choking impedance.

Well, maybe. The one I bought in 1988 was well designed with
a w2du balun and RG-8x coax. It worked well with a tuner and
I made lots of improvements as I learned more about it.

Hummm...Does that mean it's not really a G5RV anymore?

Call it a modified G5RV. It still looks like a G5RV.

Whatever I use will never mix
feedline types midroute to the antenna, I know that
for sure. It's like a crapshoot ...

Not a crapshoot at all - just an application of a series section.
Do you object to 1/4WL of 75 ohm twinlead feeding a full-wave loop?
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Not a crapshoot at all - just an application of a series section.

I'm not really talking about yours though. I'm talking about
the "usual" G5RV that is fed with a tuner, etc, ad nausium.
Most people don't change sections when they change
bands. They just redial the tuner and go.
If you change very much with a G5RV, it's not a G5RV
anymore. IE: If you feed a 102 ft dipole with ladder
line, but no choke or coax, it's not a G5RV anymore.
It's a 102 ft dipole fed with ladder line.
A series transformer for a loop is not quite the same to
me as it's almost always a single band solution.
I won't be expecting that transformer to work for all bands.
Like I said, if the "G5RV" or others of it's ilk are appealing
to you, be my guest. But trying to talk me into using one,
or even accepting it as something I would actually use is
futile. :/
Tell me this...What is the advantage of using the choke,
coax, etc, vs just running straight ladder line the whole
way? If I had to tuner feed a 102 ft dipole for all bands, thats
the way I would do it. There would be no coax, or choke.
MK

Any experience with the G5RV multiband wire antenna?
 

On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote:

Ricke wrote:
If SETUP right , There the best HF I've ever used.

Maybe the only one? :-) The G5RV, with tuner, is a pretty
good 80m, 40m, 20m, and 12m antenna. If the series section
is varied from 20 feet to 36 feet, it becomes a very good
all-HF-band antenna. With the addition of a parallel 1000pf
capacitor with the series section at 22 feet, on 75m my "G5RV"
has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole.

Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ?

In that article, on 75m you model a feedpoint impedance of 36-j324,
28' of 300 ohm ladder line, for a Z of 15+j4 (seems to indicate 46.7
deg length of 300 ohm line with 0.007dB loss (optimistic)).

At that point, were 50 ohm coax connected directly, the VSWR at the
load end of the 50 ohm coax would be 3, however you shunt the 17+j4
with 1000pF to give a new Z of 12.5-j8 that results in a VSWR at the
load end of the 50 ohm coax of around 4.1, driving a little more loss
into the coax section.

Presumably when you say that the capacitor improves the VSWR on 75m,
you mean the VSWR on the coax. Did I miss something, how does the
capacitor improve the VSWR on 75m?

Owen

PS I couldn't make the numbers work for 22' as in your quote, where I
got a VSWR at the load end of the coax of 27. I couldn't see where the
VSWR of 1.3 comes from?
--

Any experience with the G5RV multiband wire antenna?
 

On Tue, 10 Jan 2006 21:14:40 GMT, Owen Duffy wrote:

On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote:

Ricke wrote:
If SETUP right , There the best HF I've ever used.

Maybe the only one? :-) The G5RV, with tuner, is a pretty
good 80m, 40m, 20m, and 12m antenna. If the series section
is varied from 20 feet to 36 feet, it becomes a very good
all-HF-band antenna. With the addition of a parallel 1000pf
capacitor with the series section at 22 feet, on 75m my "G5RV"
has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole.

Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ?

I have made a mistake during my analysis, let me try again:

In that article, on 75m you model a feedpoint impedance of 36-j324,
28' of 300 ohm ladder line, for a Z of 15+j4 (seems to indicate 48.2
deg length of 300 ohm line with 0.007dB loss (optimistic)).

At that point, were 50 ohm coax connected directly, the VSWR at the
load end of the 50 ohm coax would be 3, however you shunt the 17+j4
with 1000pF to give a new Z of 17.3-j3.0 that results in a VSWR at the
load end of the 50 ohm coax of around 2.9, almost identical to the
case without the capacitor.

Presumably when you say that the capacitor improves the VSWR on 75m,
you mean the VSWR on the coax. Did I miss something, how does the
capacitor improve the VSWR on 75m?

Owen

PS I couldn't make the numbers work for 22' as in your quote, where I
got a VSWR at the load end of the coax of 27. I couldn't see where the
VSWR of 1.3 comes from?
--
--

Any experience with the G5RV multiband wire antenna?
 

wrote:
If you change very much with a G5RV, it's not a G5RV
anymore. IE: If you feed a 102 ft dipole with ladder
line, but no choke or coax, it's not a G5RV anymore.

But that's exactly what G5RV recommended as one form of
his G5RV antenna.

Tell me this...What is the advantage of using the choke,
coax, etc, vs just running straight ladder line the whole
way?

The advantage is a pretty good match on 80m, 40m, 20m and
12m that's not guaranteed with straight ladder-line. Some
lengths of ladder-line present additional problems. For
instance, if one happens upon a current maximum point
located at a 4:1 balun, one can take 16 ohms down to 4
ohms. That's going in the wrong direction.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Owen Duffy wrote:
Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ?

Nope, that's just an off-the-shelf vanilla G5RV.

In that article, ...

Forget that article which only shows why the *standard* G5RV is
a fairly well matched antenna on 80m and 40m.

Presumably when you say that the capacitor improves the VSWR on 75m,
you mean the VSWR on the coax. Did I miss something, how does the
capacitor improve the VSWR on 75m?

I'm sure you know this already. Given an SWR circle on a Smith Chart
that crosses the horizontal resistive line at less than 50 ohms and
given the 1/50 conductance circle, those two circles will cross at
two points. Where they cross in the capacitive reactance region is
the point on the transmission line where a parallel capacitance will
bring the impedance at that point to 50+j0 ohms. This is a common
matching technique for 75m mobile antennas. The same thing can be
done with a coil installed where the circles cross in the inductive
reactance region. This technique is described in the ARRL Antenna
Book.

What I have done on my G5RV is find the point where the SWR circle
intersects the 1/50 conductance circle in the capacitive reactance
region on 3.8 MHz and install a 1000 pf parallel cap there. My series
section line is 22.5 ft. of Wireman #554 at that point. The 50 ohm
SWR is reduced from about 5:1 to 1.3:1 on 3.8 MHz.

Given an SWR circle crossing the 1/50 conductance circle, there's a
point where a cap will result in 50 ohms. A little farther, a cap
will result in 300 ohms. A little farther, a cap will result in
450 ohms, etc. These are the points just past the current maximum
point where one can hang a capacitive stub to achieve a purely
resistive impedance.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Owen Duffy wrote:

On Tue, 10 Jan 2006 21:14:40 GMT, Owen Duffy wrote:


On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote:


Ricke wrote:

If SETUP right , There the best HF I've ever used.

Maybe the only one? :-) The G5RV, with tuner, is a pretty
good 80m, 40m, 20m, and 12m antenna. If the series section
is varied from 20 feet to 36 feet, it becomes a very good
all-HF-band antenna. With the addition of a parallel 1000pf
capacitor with the series section at 22 feet, on 75m my "G5RV"
has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole.

Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ?


I have made a mistake during my analysis, let me try again:

Now you tell me after I spent 15 minutes replying to it. :-)
The details are there so I won't repeat it here.

In that article, on 75m you model a feedpoint impedance of 36-j324,
28' of 300 ohm ladder line, for a Z of 15+j4 (seems to indicate 48.2
deg length of 300 ohm line with 0.007dB loss (optimistic)).

At that point, were 50 ohm coax connected directly, the VSWR at the
load end of the 50 ohm coax would be 3, however you shunt the 17+j4
with 1000pF to give a new Z of 17.3-j3.0 that results in a VSWR at the
load end of the 50 ohm coax of around 2.9, almost identical to the
case without the capacitor.

Presumably when you say that the capacitor improves the VSWR on 75m,
you mean the VSWR on the coax. Did I miss something, how does the
capacitor improve the VSWR on 75m?

What you missed is that the frequency must be changed to obtain the
benefit. The capacitor is *not* installed at the 17+j4 point. It is
installed at the 1/50 + j1/X admittance point. You can either increase
the length of the feedline past the 17+j4 point to the 1/50 + j1/X
admittance point or increase the frequency thus electrically lengthening
the feedline to the 1/50 + j1/X admittance point. You cannot keep both of
those values constant as you tried to do above.

You already know what I am trying to say. I must not be saying it
very well. When a parallel cap is used on a 75m screwdriver antenna
to achieve 50 ohms, the screwdriver is tuned to 1/50 + j1/X, i.e.
slightly inductive. When a parallel coil is used, the screwdriver
is tuned to 1/50 - j1/X, i.e. slightly capacitive.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

On Wed, 11 Jan 2006 00:13:14 GMT, Cecil Moore wrote:

Owen Duffy wrote:
Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ?

Nope, that's just an off-the-shelf vanilla G5RV.

In that article, ...

Forget that article which only shows why the *standard* G5RV is
a fairly well matched antenna on 80m and 40m.

But... in that article which recommends 28' of 300 ohm ladder line you
say "To improve the 75m SWR, try installing a 1000pF capacitor (mica
or doorknob) in parallel across the ladder line at the ladder line to
coax junction. Remove the capacitor for all other bands."

IMHO, just considering in isolation what is shown on that page there
is something inconsistent about the Smith chart, the impedances,
lengths, and assertions about the SWR improvement.

....

What I have done on my G5RV is find the point where the SWR circle
intersects the 1/50 conductance circle in the capacitive reactance
region on 3.8 MHz and install a 1000 pf parallel cap there. My series
section line is 22.5 ft. of Wireman #554 at that point. The 50 ohm
SWR is reduced from about 5:1 to 1.3:1 on 3.8 MHz.

This implies you are trying to "tune out" the shunt capacitive
reactance at a point on the line where the shunt resistive component
is 50... but you need the opposite sign of reactance reactance (so
that the susceptances subtract), you need an inductive reactance in
that case.

If "your G5RV" has a feedpoint impedance of 36-j324 (that seems
reasonable), your 22.5 ft. of Wireman #554 will transform that to
21.53-j53.33, and the VSWR in 50 ohm line connected at that point
would be 5.3.

A shunt capacitance CANNOT improve the 50 ohm VSWR at that point

The effect of the shunt 1000pF capacitance is to change the impedance
at the junction to around 3.6-j25, which would cause a VSWR of around
17 in the 50 ohm line.

However:

If the ladder line was around 31' in length, then the Z at that point
would be around 21+j25 (equivalent to 50 ohms R in parallel with +43
ohms X), and a shunt 1000pF (~ -42 ohms X) capacitor would give nearly
perfect VSWR on the 50 ohm line.

In summary, in a general sense, if you want to use a shunt capacitor
as you propose, you need to find length of line such that the
admittance at that point is 1/50-jB (negative susceptance is
inductive), and the correct shunt capacitor has a reactance of 1/B.

Flawed explanation aside, the only way that 22.5' works is if your
feedpoint Z is quite different to 36-j324.

Owen
--

Any experience with the G5RV multiband wire antenna?
 

On Wed, 11 Jan 2006 00:36:25 GMT, Cecil Moore wrote:


You already know what I am trying to say. I must not be saying it
very well. When a parallel cap is used on a 75m screwdriver antenna
to achieve 50 ohms, the screwdriver is tuned to 1/50 + j1/X, i.e.
slightly inductive. When a parallel coil is used, the screwdriver
is tuned to 1/50 - j1/X, i.e. slightly capacitive.

Negative susceptances are inductive. An inductive reactance of j5 is a
susceptance of 1/j5 or -j1/5.

I agree with your words, the sign of the admittances is wrong.

Owen
--

Any experience with the G5RV multiband wire antenna?
 

Owen Duffy wrote:
But... in that article which recommends 28' of 300 ohm ladder line you
say "To improve the 75m SWR, try installing a 1000pF capacitor (mica
or doorknob) in parallel across the ladder line at the ladder line to
coax junction. Remove the capacitor for all other bands."

Yes, but installing the cap will raise the resonant frequency.

What I have done on my G5RV is find the point where the SWR circle
intersects the 1/50 conductance circle in the capacitive reactance
^^^^^^^^^^
region on 3.8 MHz and install a 1000 pf parallel cap there. My series
section line is 22.5 ft. of Wireman #554 at that point. The 50 ohm
SWR is reduced from about 5:1 to 1.3:1 on 3.8 MHz.

This implies you are trying to "tune out" the shunt capacitive
reactance at a point on the line where the shunt resistive component
is 50... but you need the opposite sign of reactance reactance (so
that the susceptances subtract), you need an inductive reactance in
that case.

Sorry, I misspoke. Where I said "capacitive reactance region"
above, it should have been "inductive reactance region".

If "your G5RV" has a feedpoint impedance of 36-j324 (that seems
reasonable), your 22.5 ft. of Wireman #554 will transform that to
21.53-j53.33, and the VSWR in 50 ohm line connected at that point
would be 5.3.

"If" is the important word. My G5RV is obviously different from your
values. It's made out of insulated wire and I'm not sure it is exactly
102 feet long.

Flawed explanation aside, the only way that 22.5' works is if your
feedpoint Z is quite different to 36-j324.

And it is obvious that's the case. The "450" ohm ladder-line is 22.5 ft.
long and a 1000 pf capacitor resonates it on 3.8 MHz. Whatever the
feedpoint impedance needs to be to cause those conditions, that's
what it is.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Owen Duffy wrote:

Cecil Moore wrote:
You already know what I am trying to say. I must not be saying it
very well. When a parallel cap is used on a 75m screwdriver antenna
to achieve 50 ohms, the screwdriver is tuned to 1/50 + j1/X, i.e.
^ should be -
slightly inductive. When a parallel coil is used, the screwdriver
is tuned to 1/50 - j1/X, i.e. slightly capacitive.
^ should be +
Negative susceptances are inductive. An inductive reactance of j5 is a
susceptance of 1/j5 or -j1/5.

I agree with your words, the sign of the admittances is wrong.

Yes, you are correct - sorry. But it now seems that you understand
what I was trying to say. If one takes an ordinary G5RV and
installs a parallel 1000pf capacitor at the coax/twinlead junction,
one will raise the resonant frequency and lower the SWR on the
coax for 75m operation. Very close to 50+j0 ohms can be achieved
on 75m through that simple act. When I lived in AZ, I switched that
cap in automatically using a relay and the frequency output signal
on my IC-745.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

On Wed, 11 Jan 2006 04:25:59 GMT, Cecil Moore wrote:


Yes, you are correct - sorry. But it now seems that you understand
what I was trying to say. If one takes an ordinary G5RV and
installs a parallel 1000pf capacitor at the coax/twinlead junction,
one will raise the resonant frequency and lower the SWR on the
coax for 75m operation. Very close to 50+j0 ohms can be achieved
on 75m through that simple act. When I lived in AZ, I switched that
cap in automatically using a relay and the frequency output signal
on my IC-745.

OK.

I played around a bit using the feedpoint impedances that I modelled
for my "Feeding the G5RV" article. With 31' of 554, I needed about
2000pF to "tune" it for low 50 ohm VSWR at 3.6MHz.

I plotted the impedance presented to the coax for a range of
frequencies from 3.5 to 3.8MHz, they are at
http://www.vk1od.net/temp/G5RV-W5DXP.GIF . The Smith chart is
normalised to 50 ohms. The solution seems fairly narrow band, the VSWR
at 3.55 was 6, at 3.6 it was 1.3, and at 3.65 it was 5.

Of course, implementations will have slight differences in actual
feedpoint impedances, and the outcome is very sensitive to slight
differences in feedpoint Z. This "no-tuner" matching scheme will
probably need significant customisation for each implementation.

Owen
--

Any experience with the G5RV multiband wire antenna?
 

"Owen Duffy" wrote
Of course, implementations will have slight differences in actual
feedpoint impedances, and the outcome is very sensitive to slight
differences in feedpoint Z. This "no-tuner" matching scheme will
probably need significant customisation for each implementation.


==========================================
The World-famous G5RV.
---------------------------------
What everyone appears to forget, is that Zo of the balanced twin-line
section, on all bands except at 14.15 MHz, has a considerable affect
on feedpoint impedances, swr, losses, etc.

When describing systems and performance nobody ever mentions what Zo
of the feedline actually is. Omission of Zo reduces any following
discussion to blythe, innocent nonsense.

R.L.Varney himself never gave a value to Zo. He didn't need to. He was
concerned mainly with 14.15 MHz. It would be unfair to accuse him of
not understanding the serious effects of Zo on other bands.
----
Reg.

Any experience with the G5RV multiband wire antenna?
 

Owen Duffy wrote:
I played around a bit using the feedpoint impedances that I modelled
for my "Feeding the G5RV" article. With 31' of 554, I needed about
2000pF to "tune" it for low 50 ohm VSWR at 3.6MHz.

I'm just reporting what it took for my actual antenna under the
existing conditions at my QTH. The cap is actually 950 pf for
a minimum SWR of 1.3:1 on 3.9 MHz. The optimum value of the cap
would no doubt change at lower frequencies. With 22.5' of
Wireman #554 and a 950 pf cap, the 3:1 bandwidth is 145 kHz.
Adding sections of ladder-line lowers the resonant frequency.

Incidentally, this is a method for modifying the G5RV to work,
not only without a tuner, but with built-in tuners. When using
a built-in tuner, the antenna configuration doesn't have to
be changed as often. My IC756PRO will tune my present configuration
from 3.72-4.0 MHz. or 280 kHz.

I plotted the impedance presented to the coax for a range of
frequencies from 3.5 to 3.8MHz, they are at
http://www.vk1od.net/temp/G5RV-W5DXP.GIF . The Smith chart is
normalised to 50 ohms. The solution seems fairly narrow band, the VSWR
at 3.55 was 6, at 3.6 it was 1.3, and at 3.65 it was 5.

Changing the length of the series section will shift the resonant
frequency. I can vary mine from 22.5 ft. to 38.5 ft for a near-
perfect SWR on all HF ham frequencies.

Of course, implementations will have slight differences in actual
feedpoint impedances, and the outcome is very sensitive to slight
differences in feedpoint Z. This "no-tuner" matching scheme will
probably need significant customisation for each implementation.

IMO, that is what ham radio is all about - warm up the old MFJ-259B
and get with the program. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Reg Edwards wrote:
R.L.Varney himself never gave a value to Zo. He didn't need to. He was
concerned mainly with 14.15 MHz. It would be unfair to accuse him of
not understanding the serious effects of Zo on other bands.

However, in The ARRL Antenna Compendium #1, he did describe the
matching section well enough to calculate his Z0. It is #14
copper open-wire separated by 1.75 inches. I'll bet that's
an improvement over 300 ohm twinlead.
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Reg Edwards wrote:
R.L.Varney himself never gave a value to Zo. He didn't need to. He
was
concerned mainly with 14.15 MHz. It would be unfair to accuse him
of
not understanding the serious effects of Zo on other bands.

However, in The ARRL Antenna Compendium #1, he did describe the
matching section well enough to calculate his Z0. It is #14
copper open-wire separated by 1.75 inches. I'll bet that's
an improvement over 300 ohm twinlead.
--
73, Cecil
==========================================

Cec, the facts are, G5RV never mentioned Zo, either because he never
attached any importance to it, or he didn't understand its relevance
to other bands.

When considering other than 14.15 MHz perhaps he should have done. In
any event, everybody else has followed suit.

Now we have the situation where dozens of people are busily seriously
comparing all-band versions, one with another, and unknown to each
other they are all using different value Zo transmission lines.

Many of those who purchased the antennas, or just copied G5RV's
construction, havn't the foggiest idea what their particular Zo is.
Yet, from an analysis point of view, which you are involved with, it
is a crucial matter.

Your own Zo is a non-standard 375 ohms because you measured it. Yet
you describe its performance to others as if everybody else's Zo is
the same, whereas there is no hope of anybody else reproducing your
particular results.

Its all a load of nonsense!

If anybody, at this very late stage in the art, should still wish to
acquaint themselves with the less than mediocre performance of a G5RV,
then download program DIPOLE3 from website below.

DIPOLE3 is a general purpose program which deals with a dipole of any
length, at any frequency, plus balanced-twin feedline of any length
and any Zo, plus balun, plus coax line of any length and Zo, plus
L-tuner. So it happens to include a G5RV.

All the data for the original G5RV can be inserted in the program by
depressing one key. Modifications to the system, such as changes in
Zo, can easily be done and changes in performance immediately seen.

The final important output figure is overall loss between transmitter
and radiated power. Individual losses in the antenna, in the two
transmission lines, and in the tuner, are reported seperately. Even
the tuner L and C settings and their circuit locations are predicted.

It is very easy to sweep over the HF frequency range to check when low
swr happens to fall into amateur bands. (Unfortunately it doesn't do
this very often.)

It is also easy to change the length of transmission line (as Cecil
recommends and advertises) to try to obtain an swr of less than 2:1.
But you can use any dipole length other than 102-feet to play with
this useful aspect.

Accuracy is better than needed for the intended purposes and is
generally as good as the accuracy of program input data. There is only
one known trivial bug which occurs when dipole length is extremely
short compared with wavelength. But clearly this is not of
consequence.

What more could you want from a G5RV? There's nothing to do but erect
it and then compare it with a dipole of any other length with an open
wire feedline of thick wire, of no particular length, all the way to
the shack. Plus a choke balun.

I'm still on Red, South African, Western Cape.

Download DIPOLE3. Its free to USA citizens.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Any experience with the G5RV multiband wire antenna?
 

Reg Edwards wrote:
Cec, the facts are, G5RV never mentioned Zo, ...

Now Reg, you know that most statements using the word
"never" are false. Here's a quote from G5RV, himself,
from "The G5RV Multiband Antenna ... Up-to-Date" in
The ARRL Antenna Compendium, Vol. 1.

"If you decide to use 300-ohm ribbon type feeder for
this (series) section, it is strongly recommended that
the type with 'windows' be used. ... Since the VF of
standard 300-ohm ribbon feeder is 0.82, the mechanical
length should be 28 ft. However, if 300-ohm ribbon with
windows is used, its VF will be almost that of open-wire
feeder, say 0.90, so its mechanical length should be
30.6 ft."
--
73, Cecil http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

Now Cec, your reference to my use of the English language, which you
well understand, is an admission that you have lost the argument -
whatever that may be.

And you, more than most people, should realise that it's fatal to use
ARRL publications as Bibles.

The facts are, the Zo of the G5RV trannsmission line is indeterminate.
Everybody has a different but unknown value.

And it follows that, so are all the interminable discussions on the
subject which take place on this and other newsgroups. Hardly
educational. They approach amusing nonsense!

But no doubt you will wish to further dig yourself in and have the
last word. Go ahead! ;o) smiley
----
Reg.

Any experience with the G5RV multiband wire antenna?
 

Owen Duffy wrote:
http://www.vk1od.net/temp/G5RV-W5DXP.GIF

Owen, what software did you use to generate that graphic?
--
TNX & 73, Cecil, http://www.qsl.net/w5dxp

Any experience with the G5RV multiband wire antenna?
 

In article ,
says...
The G5RV antenna can be found by googling. Anyone using this
arrangement. It uses a coax feed to balanced feed (which variously acts
as radiating elements, depending on the band). The author says a balun
is not needed but then describes an RF choke that sounds a lot like a
balun. I am also concerned about TVI with this system.

I've been using a "shorty" version of the G5RV (not the full length
version, due to space limitations -- mine is capable of operating on 40-
10 meters) with moderate success, even at QRP power levels. Rig is an
FT-817 with no amplifier, so max power is five watts, often quite a bit
lower.

--

-- //Steve//

Steve Silverwood, KB6OJS
Fountain Valley, CA
Email:

Any experience with the G5RV multiband wire antenna?
 

There's more nonsense, old wives tales and gobbledegook generated by
THAT antenna than all other antennas put together.

Just erect the longest and highest dipole you have space for and feed
it with 450-ohm open-wire line all the way to the shack. If you don't
have a balanced tuner, use an unbalanced tuner with a choke balun. An
unbalanced tuner will probably be better anyway.

To lengthen a dipole make an inverted-U. Or make a Z with it.
----
Reg.