Posted by
N2EY on
May 19, 2007; 2:25am
URL: http://elecraft.85.s1.nabble.com/OT-G5RV-antenna-baluns-tp447606p447607.html
In a message dated 5/17/07 1:53:57 PM Eastern Daylight Time,
[hidden email] writes:
> Jim, the original G5RV is a 1-1/2 wave 20 meter *only* antenna that offered
> a good match for the coaxial line by using an open-wire matching section. As
> you know, such matching sections are frequency-dependent, like any fixed
> tuned matching network. The G5RV allowed the use of the newly-available (at
> affordable prices) coaxial lines that appeared at the end of WWII.
Well, now I'm confused.
Some years back, I remember reading "the original G5RV article" on the
internet - but now I can't find it anywhere on the 'net. I have found lots of
references to "the original G5RV article", but not the article itself.
Worse, the references don't agree with each other! Some say it was in the
November 1966 issue of RSGB Bulletin, while others say it was July 1958.
Both those dates seem too "new" to me, because coax certainly wasn't new
even in 1958.
My 4th edition RSGB Handbook (copyright 1968) doesn't have a thing on the
G5RV, either. It does have the W3EDP end-fed, though - 84 foot wire and 17 foot
counterpoise.
Does anyone have a scan of the original G5RV article?
>
> Louis Varney (G5RV) contributed to the discussion of using his 20-meter
> "G5RV" on other bands. That's what causes a lot of confusion.
>
It's certainly true that the G5RV can be optimized to present a very low SWR
on 20 meters. But if it was meant to be a 20-only antenna, why the 102 foot
length? That's too long for a 20 meter extended-double-Zepp.
> At the time Varney published his original design, many Hams operated on
> only
> one band.
But when was that?
I agree, though, that there was a time when it was not unusual for hams to
operate on just a few frequencies on one band, and to use only one mode.
>
> That changed dramatically in the years after WWII, particularly in the
> 1950's. The rapid availability of surplus parts and entire rigs, a rather
> affluent post-war society here in the USA, and a large number of commercial
> and kit rigs appearing on the market in the 50's made multi-band operation
> "normal" for most Hams.
>
Yup. In fact, this happened more than once: in the 1930s, the bankruptcy of
many early radio companies put a lot of parts (mostly receiving tubes and power
transformers) originally meant for BC sets on the 'surplus' market at rather
low prices. And then the sudden end of WW2 did it on a much larger scale.
In fact, the first-generation Heathkits were largely based on surplus parts.
That's why so many odd tube types were used in them.
> Hams, always willing to "try anything" for an antenna -- even loading up
> the
> bedsprings (literally!), wanted to use Varney's G5RV design on more than 20
> meters. Of course, the G5RV is nothing more than a doublet fed with open
> wire line, an efficient multi-band design that had been popular since the
> 1920's. Varney's contribution was the use of a specific open wire line
> section to match to coaxial line on 20 meters without the need for an
> antenna tuner (ATU). Ignoring the matching section and simply using it as a
> multi-band doublet worked fine, as long as one used a suitable matching
> network (ATU) and avoided the coax section.
>
> The problem was that Hams wanted to use coaxial lines. Not only were they
> easier to run into the shack, virtually all post-War rigs were designed for
> coaxial feedlines for simpler bandswitching and TVI-proofing. So the battle
> to find a suitable compromise between efficiency and the use of coax in a
> multi-band "G5RV" started in earnest.
>
> Varney himself wrote about those attempts, emphasizing the need for a
> matching network (ATU) on any but the 20 meter bands or if the dimensions of
> the antenna or feeders were changed in any way.
>
All true - but as I read the article, he found a combination of lengths of
antenna wire and balanced feeder that gave a reasonable match on "all HF
bands". It sounded to me as if the antenna were meant for folks who had limited
space, and could only have one antenna.
However, it must be remembered that, in those days, "all HF bands" did not
include 160, 30, 17 or 12 meters. And "reasonable match" could mean an SWR of 3
or so on the coax line on some bands - which wasn't a problem for most tube
rigs, nor for short runs of coax.
Plus, G-land, 80 meters was 3500 to 3800 kHz, and 40 meters 7000 to 7100 kHz.
IOW, what was considered "low SWR" and "doesn't need a tuner" in those days
might cause today's hams to thing something was awfully wrong.
Does anybody have a link or scan to the original G5RV article?
73 de Jim, N2EY
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