G5RV

[Robert Boerhorst-2]

Ref question N2EY

You will find the original article from G5RV himself on:
www.remeeus.eu/hamradio/antennes_tuners/g5rv.htm

73,
Rob, PA0RBO, K2 # 2406
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[N2EY]

In a message dated 5/19/07 8:25:36 AM Eastern Daylight Time,
[hidden email] writes:


> Ref question N2EY
>
> You will find the original article from G5RV himself on:
> www.remeeus.eu/hamradio/antennes_tuners/g5rv.htm
>
>

Thanks for the link, but it's not the article I was looking for. I'm looking
for the first article he wrote describing the classic 102 foot dipole with 31
foot open-line matching section.

G5RV described the antenna that bears his call long before 1984.
In fact, I have found various references that say the first/original article
appeared in 1946, 1958, and 1966.

Thanks again for the link

73 de Jim, N2EY


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[Ron D'Eau Claire-2]

That was published in 1984 covering a multiband affair. According to Heys,
G3BDQ, the original G5RV article was published in 1946 for a single band
antenna. In fact the biography box on the first page of the linked article
says Varney designed the original G5RV in 1946.

Varney published several articles about multiband use of his design. There's
an update of the article linked below, also by Varney, available on the ARRL
web site (www.arrl.org).

Varney simply reverted to using his design as a center fed doublet on any
band except 20 meters! Of course, a center-fed doublet (random length
horizontal wire, broken at the center for low-loss open-wire feedline) has
been an well-known, efficient antenna since the 1920's. Varney offered
nothing new in his G5RV design except on 20 meters where the length of the
horizontal wire coupled with the matching section (33 feet of open wire line
of specific size and spacing) produced a tolerably low SWR for common types
of feed lines in use in 1946. It needed a matching network between the
feedline and the matching section on other bands, and was not optimized for
50 ohm coax even on 20 meters! From the referenced article, Varney writes:

"Although the impedance match for 75-ohm twin lead or 80-ohm coaxial cable
at the base of the matching section is good at 14 MHz, and even the use of
50 ohm coaxial cable results in only about a 1.8:1 SWR on this band, the use
of a suitable matching network is necessary on all other HF bands.."

Note the terminology: "Matching section" is the length of open wire line of
specific length, wire size and spacing used to match the center of the
horizontal wire to a feed line at the lower end. "Matching network" is what
we call today an antenna tuner or ATU.

The matching network (ATU) should be at the end of the matching section
(open work line), not at the rig. Putting the tuner at the rig adds
significant losses to the system depending upon the type and length of
feeder used between the rig and the "matching section". Also, note that the
original design was optimized for 80 ohm coax or 75 ohm twinlead, both of
which were fairly common right after WWII.

Post WWII rigs with tunable "pi-network" outputs could handle quite a wide
range of feeder impedances efficiently without resorting to an external
"tuner". We weren't particularly concerned about an SWR of 2:1, 4:1 or more
even if we had the means to measure it. So a 1.8:1 SWR was quite good. Of
course, with today's fixed-tuned rigs that's crowding the point at which the
rig will roll back power or shut down altogether to protect the finals
unless a tuner is used at the output to reduce the SWR the rig "sees".

Used that way, the G5RV is identical to the common multi-band doublet used
since the 1920's. It's efficient if:

1) An efficient tuner is used capable of matching the rig to the antenna,
and

2) No coax or other lossy feed line is used between the tuner and the
radiator.

Bottom line is that the practice of putting the tuner at the rig, and
running coax between the tuner and the radiator with perhaps a balun or unun
thrown in significantly increases the losses.  

Ron AC7AC


-----Original Message-----

Ref question N2EY

You will find the original article from G5RV himself on:
www.remeeus.eu/hamradio/antennes_tuners/g5rv.htm

73,
Rob, PA0RBO, K2 # 2406 _______________________________________________

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[john petters]

Ron D'Eau Claire wrote:

>
> Used that way, the G5RV is identical to the common multi-band doublet used
> since the 1920's. It's efficient if:
>
> 1) An efficient tuner is used capable of matching the rig to the antenna,
> and
>
> 2) No coax or other lossy feed line is used between the tuner and the
> radiator.
>
> Bottom line is that the practice of putting the tuner at the rig, and
> running coax between the tuner and the radiator with perhaps a balun or unun
> thrown in significantly increases the losses.  

Agree absolutely
John G3YPZ
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[N2EY]

Thanks to the efforts of N7WS and G3VGR, I now have pdfs of the 1958, 1966
and 1984  G5RV articles. What an incredible online community - within a few
hours of a request, fellow amateurs a continent and an ocean away supply me with
the information.

In a message dated 5/19/07 2:34:37 PM Eastern Daylight Time,

[hidden email] writes:

>
> Varney simply reverted to using his design as a center fed doublet on any
> band except 20 meters! Of course, a center-fed doublet (random length
> horizontal wire, broken at the center for low-loss open-wire feedline) has
> been an well-known, efficient antenna since the 1920's. Varney offered
> nothing new in his G5RV design except on 20 meters where the length of the
> horizontal wire coupled with the matching section (33 feet of open wire line
> of specific size and spacing) produced a tolerably low SWR for common types
> of feed lines in use in 1946. It needed a matching network between the
> feedline and the matching section on other bands, and was not optimized for
> 50 ohm coax even on 20 meters!

I have to disagree with this somewhat.

The intent of the G5RV design, IMHO, wasn't to make an optimized antenna
for 50 ohm coax or 20 meters, but rather to make one that would be a
reasonable compromise for the HF/MF ham bands of the time.

>From the referenced article, Varney writes:
>
>
> "Although the impedance match for 75-ohm twin lead or 80-ohm coaxial cable
> at the base of the matching section is good at 14 MHz, and even the use of
> 50 ohm coaxial cable results in only about a 1.8:1 SWR on this band, the use
> of a suitable matching network is necessary on all other HF bands.."
>
> Note the terminology: "Matching section" is the length of open wire line of
> specific length, wire size and spacing used to match the center of the
> horizontal wire to a feed line at the lower end. "Matching network" is what
> we call today an antenna tuner or ATU.
>
> The matching network (ATU) should be at the end of the matching section
> (open work line), not at the rig. Putting the tuner at the rig adds
> significant losses to the system depending upon the type and length of
> feeder used between the rig and the "matching section". Also, note that the
> original design was optimized for 80 ohm coax or 75 ohm twinlead, both of
> which were fairly common right after WWII.
>

But the actual added losses of using a tuner at the rig may not be worth
worrying about. It all depends on the situation.

> Post WWII rigs with tunable "pi-network" outputs could handle quite a wide
> range of feeder impedances efficiently without resorting to an external
> "tuner". We weren't particularly concerned about an SWR of 2:1, 4:1 or more
> even if we had the means to measure it. So a 1.8:1 SWR was quite good. Of
> course, with today's fixed-tuned rigs that's crowding the point at which the
> rig will roll back power or shut down altogether to protect the finals
> unless a tuner is used at the output to reduce the SWR the rig "sees".
>

Yup. In fact, towards the end of the hollowstate era, the matching range of
many tube rigs was quite restricted, so that SWR of more than 2 or 3 to 1 was
too much for them.

Even with all-open-line feed, G5RV developed something worthwhile.

The classic dipole fed with ladder line and a tuner can be made to work on
all bands even if random lengths of dipole and feedline are used. But the
impedances at the shack-end of the line may be very high, very low, and/or very
reactive if this is done.

What G5RV did was to come up with a set of values that result in
easier-to-match values of impedance at the shack end of the line.

73 de Jim, N2EY




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[David Cutter]

BUT if you just want to get out for general rag-chewing, then the coax
version combined with a rig with built-in auto matching makes for a very
simple set-up.

For a local ham with bad arthritis, that's all he wanted, ie push-button
technology, no fiddling with knobs as he put it.  I couldn't think of an
easier solution for him.

The only extra  was a switch to make it into a top loaded system for 160m.
For top to ten, this is the simplest and most cost-effective antenna I have
ever used.  After all, even though he lost a few watts in the coax, he was
still getting out and probably within an S point of a properly set up
doublet.  Instead of running 50W he could run 100W, power is cheap and
amateur radio gave him a great buzz.

KISS where-ever possible.

David
G3UNA

----- Original Message -----
From: "john petters" <[hidden email]>
To: "Ron D'Eau Claire" <[hidden email]>
Cc: "'Elecraft'" <[hidden email]>
Sent: Saturday, May 19, 2007 8:39 PM
Subject: Re: [Elecraft] G5RV

>
>
> Ron D'Eau Claire wrote:
>
>>
>> Used that way, the G5RV is identical to the common multi-band doublet
>> used
>> since the 1920's. It's efficient if:
>>
>> 1) An efficient tuner is used capable of matching the rig to the antenna,
>> and
>>
>> 2) No coax or other lossy feed line is used between the tuner and the
>> radiator.
>>
>> Bottom line is that the practice of putting the tuner at the rig, and
>> running coax between the tuner and the radiator with perhaps a balun or
>> unun
>> thrown in significantly increases the losses.
>
> Agree absolutely
> John G3YPZ
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com 

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