OT:. G5RV's

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OT:. G5RV's

Ken G Kopp
As usual, Jim is correct ...

I have Lou Varney's original article.  The G5RV was designed as a 20M
--ONLY-- antenna.  It's now achieved some kind of cult ... read voodoo ...
status. (;-)

If one has an antenna that is partially fed with balanced line that's then
directly (!) spliced to a specific length of coax and then still requires a
tuner, why not run the balanced line directly to the tuner ... assuming it
has a balun ... or provide one at the tuner?

This same argument would apply to Varney's design for a 20M only dipole.

Maybe he didn't have a tuner of any kind, and wanted to use coax feed line
because there was a coax connector on his rig. (;-)

73

K0PP
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Re: OT:. G5RV's

Wes Stewart-2
In my 1999 paper, /"Balanced Transmission Line in Current Amateur Practice"/
(http://k6mhe.com/n7ws/Ladder_Line.pdf), published in the /ARRL Antenna
Compendium, Volume 6, /pp 174-178, I have this statement: "A popular multiband
wire antenna is the so-called G5RV. This antenna is rarely used as was intended
by Varney, but for some reason, the 102-foot length has taken on mystical
properties,...."

It's a pity that too many newcomers, as well as many oldsters, are enamored by
this piece of wire.  First, a 102' length is not resonant on 20-meters, so in
common jargon, it's *not* a 20-meter antenna, any more than any other random
length would be. Second, I understand that the conventional wisdom is that it
has "gain" on 20-meters.  Maybe so, but the usual application has the wire
strung up between available supports that may, or may not, direct the "gain" in
a useful direction.  A coax-fed, rotatable, resonant dipole would run rings
around a G5RV.

(While it's off-topic on this off-topic subject, the fascination with the
"magical" 43-foot vertical is equally bewildering to me.)

In my published paper, space limited any discussion of tuner loss, however, in
1994 (type)written correspondence with editor Dean Straw I gave him examples of
the horrific losses that could be incurred even with high quality tuners, when
used as proposed the the article* that got me going on this subject.  It's
interesting to note that to my knowledge, loss in tuners had never been
mentioned in any ARRL publications before this correspondence. Shortly
thereafter, "/How to Evaluate Your Antenna Tuner" /was published in 1995.  
Coincidence I'm sure.

BTW, any ARRL publication before 1994 with charts of transmission line loss that
include open-wire line is incorrect.  It's easily seen by inspection, but
apparenty I was to first to inspect it. Dean and I hashed out a correct
attenuation chart.

Wes  N7WS

* "/The Lure of the Ladder Line", QST, /December 1993, pp. 70-71




: On 8/4/2016 11:08 AM, Ken G Kopp wrote:

> As usual, Jim is correct ...
>
> I have Lou Varney's original article.  The G5RV was designed as a 20M
> --ONLY-- antenna.  It's now achieved some kind of cult ... read voodoo ...
> status. (;-)
>
> If one has an antenna that is partially fed with balanced line that's then
> directly (!) spliced to a specific length of coax and then still requires a
> tuner, why not run the balanced line directly to the tuner ... assuming it
> has a balun ... or provide one at the tuner?
>
> This same argument would apply to Varney's design for a 20M only dipole.
>
> Maybe he didn't have a tuner of any kind, and wanted to use coax feed line
> because there was a coax connector on his rig. (;-)
>
> 73
>
> K0PP

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Re: OT:. G5RV's

Alan Bloom
 > It's a pity that too many newcomers, as well as many oldsters, are
 > enamored by this piece of wire.

The G4RV is definitely a compromise antenna.  However its advantage is
that is has low-enough SWR to be easily matched by most tuners on a
number of bands.

 > ... the horrific losses that could be incurred even
 > with high quality tuners,

It's true that tuner losses are the manufacturers' dirty little secret.
Loss is rarely specified, partly because it can be pretty bad, and
partly because it is hard to measure, but also because it is not
constant - it depends on the particular impedance being matched.

One exception is the old Drake tuners.  Their Pi-L topology makes the
loss almost independent of the load impedance.  If you can get it to
match, you know that almost all the power is going into the feed line.
For example, the MN-2700 that I designed when I was at Drake was
specified at 0.5 dB maximum insertion loss and I did a lot of testing
and tweaking to achieve that on all bands.

Alan N1AL
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Re: OT:. G5RV's

Joe Subich, W4TV-4
In reply to this post by Wes Stewart-2
On 8/4/2016 4:41 PM, Wes Stewart wrote:
 > First, a 102' length is not resonant on 20-meters, so in common
 > jargon, it's *not* a 20-meter antenna, any more than any other random
 > length would be.

*Not* true ... 102' is three half-waves on 20 meters:
    984/2 * (3 -.05) / 14.15 =  102.6'

Check the ARRL antenna book for the formula of a "harmonic wire" -
in this case three half waves.

73,

    ... Joe, W4TV

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Re: OT:. G5RV's

John-489
In reply to this post by Wes Stewart-2
Wes......

Over the years, immediately after a change in QTH, I have used the G5RV
as an interim antenna. My personal experience is that it is a reasonable
performer, as compared to a single band, resonant half-wave dipole, at
the same height, fed by the same coax/length.

While I certainly don't accept as Gospel everything that Tom W8JI
publishes, I generally find his work to be sound and educational.

How do you reconcile your position versus Tom's on this antenna?

I'll attempt to list the link here, but if it doesn't "take", just
search "W8JI G5RV". His hands-on A/B testing is interesting, along with
his modeling showing well less than 1db difference between the G5RV and
resonant half-wave dipole on 80 40 20, and within 1.5 db on 15. He
suggests a length ratio of roughly 80/20% versus the apparent standard
of 67/33%.

Like all antennas, construction, proximity to interfering objects, and
height make a huge difference in performance.

73 John W4II

http://www.w8ji.com/g5rv_facts.htm
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Re: OT:. G5RV's

k6dgw
In reply to this post by Wes Stewart-2
Ummm ... my HP48GX says 102' is very very close to 3 half-waves at 14
MHz which sounds sort of resonant-ish.  Maybe a little known bug in my
calculator?

On a similar path, I decided to try out the 80-10 EFHW from MyAntennas
as an HOA Stealth antenna strung along the top of a 6' fence.  It's 130'
long, has a 6 turn series inductor wound on a Sch 40 PVC fitting a short
distance out from a heavy-ish box with an SO-239.  I figured there might
be a 50 ohm resistor in the box a la the famous B&W folded dipole that
graces many National Guard Armories.

The impedance sweep when I got it yielded close enough to 50+j0 ohms on
all bands ... except 60 m that my K3/100 is happy without the KAT3.  It
also revealed nearly infinite impedance between the bands, sort of
ruling out the resistor [I've come to believe it's a transformer, maybe
of the "auto" variety].

It works surprisingly well.  On 80 and 40 it's pretty NVIS, which
happens to be what I'm looking for.  Above 40, the pattern starts to
become more complex and much less vertical if I can believe EZNEC.  6'
AGL is obviously not optimal ... except for our HOA and the CC&R's ...
but I'm very surprised at how well it does, especially at the bottom of
the cycle.

This list seems to have a number of antenna experts aboard [and maybe a
few who play antenna experts on TV] ... would anyone like to 'splain to
me how it achieves low SWR on all bands?  I could probably ferret that
out with enough time, but if someone already knows ...

73,

Fred K6DGW
Sparks NV
Washoe County DM09dn

On 8/4/2016 1:41 PM, Wes Stewart wrote:

> It's a pity that too many newcomers, as well as many oldsters, are
> enamored by this piece of wire.  First, a 102' length is not resonant on
> 20-meters, so in common jargon, it's *n
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Re: OT:. G5RV's

Guy Olinger K2AV
Hi Fred,

Loss *anywhere* would broaden the antenna. Famously the B&W folded dipole,
fed at the center of one wire, and terminated with an RF resistor at the
center of the other, has for decades been serving commercial installations
with widely separated operating frequencies not connected by any fortunate
harmonic relationship. That antenna has roughly an intentional 3 dB loss at
a designed position in the antenna. See
https://www.bwantennas.com/images/fdipole.gif for a drawing.

In the case of your EFHW, the broadening loss is the dielectric loss in the
fence itself, and in the ground very close underneath.

The B&W folded dipole as a solution sticks in the craw of a lot of hams,
because we always think there is some way to navigate the problems and keep
the 3 dB for ourselves. The thought of heating up the air with half the
power out from out two kilo-buck brick-on-key PileUpBuster brand amp just
bothers us no end.

And where the power to the antenna cannot be increased by 3 dB to
compensate, if we regularly work the barely open paths on the low bands for
new DX and contest multipliers, that 3 dB can make a huge difference.

BUT...

If we are just dodging the HOA, vs creating a remote site, or not operating
at all, what you describe seems quite reasonable. One half wave on 80, two
on 40, three on 30m, four on 20m, etc. allow a rather simple feed
mechanism, and any sloppiness will be mitigated to some degree in the
unavoidable dielectric loss of the fence and ground.

In the past, particularly with tetrode final tube(s), a pi network would
absorb ugly antenna impedances just by load and tune, easily servicing
impedances that would croak transistor amps. Back in 1959 I regularly
worked the traffic nets end-feeding 120 feet of wandering wire up about 20
feet against a ground pipe, fed with about 30 feet of coax directly from an
807 tetrode and a pi network. I was not loud, but I won a BPL medallion. A
later addition of a home brew 250TH amp improved things quite a bit for the
folks on the other end, but the antenna was as much as I could ever do from
that location.

73, Guy K2AV

On Thu, Aug 4, 2016 at 6:22 PM, Fred Jensen <[hidden email]> wrote:

> Ummm ... my HP48GX says 102' is very very close to 3 half-waves at 14 MHz
> which sounds sort of resonant-ish.  Maybe a little known bug in my
> calculator?
>
> On a similar path, I decided to try out the 80-10 EFHW from MyAntennas as
> an HOA Stealth antenna strung along the top of a 6' fence.  It's 130' long,
> has a 6 turn series inductor wound on a Sch 40 PVC fitting a short distance
> out from a heavy-ish box with an SO-239.  I figured there might be a 50 ohm
> resistor in the box a la the famous B&W folded dipole that graces many
> National Guard Armories.
>
> The impedance sweep when I got it yielded close enough to 50+j0 ohms on
> all bands ... except 60 m that my K3/100 is happy without the KAT3.  It
> also revealed nearly infinite impedance between the bands, sort of ruling
> out the resistor [I've come to believe it's a transformer, maybe of the
> "auto" variety].
>
> It works surprisingly well.  On 80 and 40 it's pretty NVIS, which happens
> to be what I'm looking for.  Above 40, the pattern starts to become more
> complex and much less vertical if I can believe EZNEC.  6' AGL is obviously
> not optimal ... except for our HOA and the CC&R's ... but I'm very
> surprised at how well it does, especially at the bottom of the cycle.
>
> This list seems to have a number of antenna experts aboard [and maybe a
> few who play antenna experts on TV] ... would anyone like to 'splain to me
> how it achieves low SWR on all bands?  I could probably ferret that out
> with enough time, but if someone already knows ...
>
> 73,
>
> Fred K6DGW
> Sparks NV
> Washoe County DM09dn
>
> On 8/4/2016 1:41 PM, Wes Stewart wrote:
>
> It's a pity that too many newcomers, as well as many oldsters, are
>> enamored by this piece of wire.  First, a 102' length is not resonant on
>> 20-meters, so in common jargon, it's *n
>>
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>
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Re: OT:. G5RV's

Elecraft K3
In reply to this post by John-489
John,

I think this is a reasonable conclusion.  Early on I used a G5RV and it was invaluable reference for my later antenna building experience.  I went to build doublets in the same space and I still keep an 80m doublet in the air.

Recently I have gotten into building no compromise rotatable dipoles.  By no compromise I mean full sized monoband rotatable dipoles - no traps, coils or cap hats 1/2 wave off the ground in free space.  These are relatively easy to build without a huge tower if you keep the weight down.  That’s not too hard to do without a boom to support the parisitic elements.  Great bang for the buck.

Another country heard from,

73 de Eric, KG6MZS
 
> On Aug 4, 2016, at 3:14 PM, John Frazier <[hidden email]> wrote:
>
> Over the years, immediately after a change in QTH, I have used the G5RV as an interim antenna.
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Re: OT:. G5RV's

Don Wilhelm
In reply to this post by Wes Stewart-2
Wes and all,

Yes, the G5RV, the Off-Center-Fed antennas (Carolina Windom for one
example) and the 43 foot vertical have become "magical" antennas, and I
am not certain why.

My best guess is that they are "salvation" for hams who want to operate
on multiple bands with one antenna, and they can be made to "work" in
one fashion or another.

All need a tuner of some sort, and the 43 foot vertical needs a remote
tuner at the base for efficient operation, or at least a matching
section for each band at the base for efficient operation.  One could
feed that vertical with low loss open wire line and put the matching
tuner in the shack, but most choose to feed with coax along with the
attendant losses incurred if no matching is done at the vertical base.

IMHO, resonant fan dipoles are a much better solution - whether those be
constructed as inverted Vee's or whether as parallel dipoles separated
by 1 foot or more to reduce interaction.

I use resonant parallel dipoles here.  The 80 and 40 inverted vee's are
supported on a 50 foot tower and the 80 meter legs are perpendicular to
the 40 meter legs, so there is no interaction.

I have another 3 band band fan dipole for 20, 15, and 10 hung as a
horizontal dipole with the radiators separated 1 foot from each other
(other than at the center point) and a similar 3 band fan dipole for 30,
17, and 12 meters.
That means 3 coax lines into the shack, or a remote antenna switch -
which I use because I have other antennas to deal with, a 60 meter
inverted vee, and a Gap Titan vertical.

As far as I am concerned, resonant dipoles are the preferred solution.  
Other antennas may work, but are a compromise, and some (particularly
the OCF antennas) produce RF-in-the-Shack that can be difficult to suppress.

There is no "magic" with antennas.  Some antenna designs were created
when we had PA output circuits that could handle a wide range of antenna
impedances and used low loss open wire feedlines.  That is no longer the
case with the transceiver (or amplifier) that needs to operate into a 50
ohm load, and ATUs with limited matching range.

So take your pick and know the hazards and consequences of that choice.
Any antenna that you can feed power to will radiate, but some do it
better than others.  My choice is to use center fed dipoles which at any
length can be easily tamed, and I shy away from the OCF antennas which
can create RF-in-the-Shack problems.
There is no "magic" with antennas, the knowledge base for radiation from
a wire (or piece of aluminum) has been around for many long years, but
the resulting feedpoint impedance is what we commonly deal with along
with all its hazards and consequences.

73,
Don W3FPR

On 8/4/2016 4:41 PM, Wes Stewart wrote:

> In my 1999 paper, /"Balanced Transmission Line in Current Amateur
> Practice"/ (http://k6mhe.com/n7ws/Ladder_Line.pdf), published in the
> /ARRL Antenna Compendium, Volume 6, /pp 174-178, I have this
> statement: "A popular multiband wire antenna is the so-called G5RV.
> This antenna is rarely used as was intended by Varney, but for some
> reason, the 102-foot length has taken on mystical properties,...."
>
> It's a pity that too many newcomers, as well as many oldsters, are
> enamored by this piece of wire.  First, a 102' length is not resonant
> on 20-meters, so in common jargon, it's *not* a 20-meter antenna, any
> more than any other random length would be. Second, I understand that
> the conventional wisdom is that it has "gain" on 20-meters.  Maybe so,
> but the usual application has the wire strung up between available
> supports that may, or may not, direct the "gain" in a useful
> direction.  A coax-fed, rotatable, resonant dipole would run rings
> around a G5RV.
>
> (While it's off-topic on this off-topic subject, the fascination with
> the "magical" 43-foot vertical is equally bewildering to me.)
>

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Re: OT:. G5RV's

Lynn W. Taylor, WB6UUT
In reply to this post by Guy Olinger K2AV
What happens if the antenna is well above ground, away from any fences?

On 8/4/2016 3:55 PM, Guy Olinger K2AV wrote:
> If we are just dodging the HOA, vs creating a remote site, or not operating
> at all, what you describe seems quite reasonable. One half wave on 80, two
> on 40, three on 30m, four on 20m, etc. allow a rather simple feed
> mechanism, and any sloppiness will be mitigated to some degree in the
> unavoidable dielectric loss of the fence and ground.


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Re: OT:. G5RV's

Jim Brown-10
In reply to this post by Guy Olinger K2AV
On Thu,8/4/2016 4:31 PM, Walter Underwood wrote:
> There is one efficient way to broaden an antenna’s frequency range—lower the Q. That is usually done with large-diameter elements. You can cover all of the 80 meter band with reasonable SWR using a “cage dipole”. That is what they do at W1AW. At VHF/UHF, you may see bowtie antennas, which are also low-Q.

Exactly right.  I've used that technique on my 160M Tee vertical.

On Thu,8/4/2016 4:37 PM, Elecraft K3 wrote:
> Recently I have gotten into building no compromise rotatable dipoles.  By no compromise I mean full sized monoband rotatable dipoles - no traps, coils or cap hats 1/2 wave off the ground in free space.  These are relatively easy to build without a huge tower if you keep the weight down.  That’s not too hard to do without a boom to support the parisitic elements.  Great bang for the buck.

Exactly right -- height matters, and 1/2 wave is an excellent height for
any dipole. I have two half wave fan dipoles for 80 and40 at right
angles, up about 140 ft. Same idea, but  organic supports (redwoods).
:)  Nothing's free though -- tree climbers cost money, and so does 130
ft of tower, safely installed. :)

73, Jim K9YC

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Re: OT:. G5RV's

Nr4c
In reply to this post by Wes Stewart-2
Let's see,  102 + 33 = 135. Isn't that pretty close to the length of an 80 Meter Dipole?  The G5RV looks like two back-to-back inverted "L" antennas. The twin lead is not feed line but part of the radiator.

Sent from my iPhone
...nr4c. bill


> On Aug 4, 2016, at 4:41 PM, Wes Stewart <[hidden email]> wrote:
>
> In my 1999 paper, /"Balanced Transmission Line in Current Amateur Practice"/ (http://k6mhe.com/n7ws/Ladder_Line.pdf), published in the /ARRL Antenna Compendium, Volume 6, /pp 174-178, I have this statement: "A popular multiband wire antenna is the so-called G5RV. This antenna is rarely used as was intended by Varney, but for some reason, the 102-foot length has taken on mystical properties,...."
>
> It's a pity that too many newcomers, as well as many oldsters, are enamored by this piece of wire.  First, a 102' length is not resonant on 20-meters, so in common jargon, it's *not* a 20-meter antenna, any more than any other random length would be. Second, I understand that the conventional wisdom is that it has "gain" on 20-meters.  Maybe so, but the usual application has the wire strung up between available supports that may, or may not, direct the "gain" in a useful direction.  A coax-fed, rotatable, resonant dipole would run rings around a G5RV.
>
> (While it's off-topic on this off-topic subject, the fascination with the "magical" 43-foot vertical is equally bewildering to me.)
>
> In my published paper, space limited any discussion of tuner loss, however, in 1994 (type)written correspondence with editor Dean Straw I gave him examples of the horrific losses that could be incurred even with high quality tuners, when used as proposed the the article* that got me going on this subject.  It's interesting to note that to my knowledge, loss in tuners had never been mentioned in any ARRL publications before this correspondence. Shortly thereafter, "/How to Evaluate Your Antenna Tuner" /was published in 1995.  Coincidence I'm sure.
>
> BTW, any ARRL publication before 1994 with charts of transmission line loss that include open-wire line is incorrect.  It's easily seen by inspection, but apparenty I was to first to inspect it. Dean and I hashed out a correct attenuation chart.
>
> Wes  N7WS
>
> * "/The Lure of the Ladder Line", QST, /December 1993, pp. 70-71
>
>
>
>
> : On 8/4/2016 11:08 AM, Ken G Kopp wrote:
>> As usual, Jim is correct ...
>>
>> I have Lou Varney's original article.  The G5RV was designed as a 20M
>> --ONLY-- antenna.  It's now achieved some kind of cult ... read voodoo ...
>> status. (;-)
>>
>> If one has an antenna that is partially fed with balanced line that's then
>> directly (!) spliced to a specific length of coax and then still requires a
>> tuner, why not run the balanced line directly to the tuner ... assuming it
>> has a balun ... or provide one at the tuner?
>>
>> This same argument would apply to Varney's design for a 20M only dipole.
>>
>> Maybe he didn't have a tuner of any kind, and wanted to use coax feed line
>> because there was a coax connector on his rig. (;-)
>>
>> 73
>>
>> K0PP
>
> ______________________________________________________________
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Re: OT:. G5RV's

k6dgw
In reply to this post by Lynn W. Taylor, WB6UUT
My EFHW [granted, it is technically only one half-wave on 80 m] got a
pretty good write up in QST not long ago, after I had it installed, and
he elevated the far end into a tree.  While his review was pretty
qualitative [:-(] which has become more common in QST these days, he
still got the same impedance sweep 3-30 MHz as I do.  So, I'm not sure
the electrical characteristics are all that dependent on dielectric loss
in my fence.  The fence is very dry wood, our relative humidity runs in
single digits most of the time, it was 6% last evening.

At any rate, it looks like I'm going to sell my KPA500/KAT500, just have
to get up the nerve to part with them.  The antenna is rated at 500W
ICAS [whatever that means quantitatively these days], but I'm loathe to
nuke Toady, the neighbor's Lab whose run is directly on the other side
of the fence.  I do occasionally turn on a couple of lamps in the
bedroom on capacitative switches on 80 with 100W, that's enough.

My only connection with MyAntennas was to write them a $140 check, but I
really am surprised how well it performs in a highly non-optimal
configuration.  All this "matching bafflegab" was unheard of when I was
a young ham.  You fed your dipole with 75 ohm twin-lead, coupled it to
the PA with a 2 or 3 turn link coil, and as the reactance of the link
changed the resonance, you compensated by "re-dipping the plate."

Of course, when I was a young ham, dirt was pretty young too. :-)

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

On 8/4/2016 4:48 PM, Lynn W. Taylor, WB6UUT wrote:

> What happens if the antenna is well above ground, away from any fences?
>
> On 8/4/2016 3:55 PM, Guy Olinger K2AV wrote:
>> If we are just dodging the HOA, vs creating a remote site, or not
>> operating
>> at all, what you describe seems quite reasonable. One half wave on 80,
>> two
>> on 40, three on 30m, four on 20m, etc. allow a rather simple feed
>> mechanism, and any sloppiness will be mitigated to some degree in the
>> unavoidable dielectric loss of the fence and ground.
>
>
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Re: OT:. G5RV's

Edward R Cole
In reply to this post by Ken G Kopp
Jim and all:

Interesting comments on the G5RV (I've never built one but have a
local friend that uses one).

For years I used wire dipoles on HF bands: I made a 80/40m trap
dipole, 80/40m dipole with removable clip at 40m length which we call
the "Iditarod Special" as it was simple to use at remote checkpoints
on the trail for changing prop day/night over 150-900 mi range in
winter.  Sometimes the antenna was only 8-foot off the ground (high
as one could reach without ladder), but worked surprisingly well for
extreme NVIS.

I had a 80/40/20m fan inverted-V at home before putting up my tri-band yagi.

Now the inverted-V is 80/40m fan style.  It works better on 3800-4000
than on 40m where bandwidth seems narrow.  The center is fed with
commercial 1:1 balun at 40-feet and ends are 20-feet high which works
well for NVIS.

I can tune it higher than 7100 using my tuner which is a Drake
VN-2000 "oldie but goodie".  The tri-band yagi also needs help
resonating which the Drake handles fine.

Accidentally my 600m inverted-L is 43 feet high.  I have a 122-foot
long top leg of two parallel wires and the vertical is three parallel
wires.  Base coil is 11x10 inch diameter fed near ground end with
coax.  Ground radials are also very short for 472-KHz and consist of
2-foot wide by 50 to 70 foot long chicken wire lain on the
ground.  Efficiency is 0.8 % but it works for both Tx and Rx, having
my signal been heard over 4,000 miles away in Buffalo, NY.  Normal
ground-wave distance is about 250 mi running 100w output from
amplifier (converted NDB transmitter driven by my K3 at 0.1mw).

73, Ed - KL7UW

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
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Re: OT:. G5RV's

Don Wilhelm
In reply to this post by k6dgw
Fred,

Dirt was young when I was first licensed too.
I do remember those days of link coils that you slowly advanced into the
PA inductor and re-dipped the plate until the current draw was correct
for the power level that you wanted to operate.  Those were the days of
plug-in coils for each band.  Yes, I do have some of those plug-in coils
and swinging link coils in my stash of "old stuff" in the attic.

Then came the Johnson Matchbox with its band switching capability (I
have one of those too), and multi-band PA stages with a Pi-Network.

Those days are past.  Many new hams do not know how to 'dip the plate'
and then increase the "loading " and re-dip the plate until the plate
current was as desired.

I now do not recommend a transceiver to a new ham if it has 'tuning' and
'loading' knobs - the information about how to do that properly is just
not abundant today as it was in years past.

Add to that fact that the re-tuning had to be repeated for each band
change or significant QSY in the band.

We have come a long way with the advent of solid state PA stages and
broadband tuning with only a Low Pass Filter at the PA output - but the
penalty of that is we now have to operate the PA stage into a 50 ohm
load.  That is where the ATU comes into play.  The variability in the
antenna feedpoint impedance has been moved from the PA output stage to
the "tuning unit" to allow us to feed antennas that present an impedance
of other than 50 ohms to the PA stage.

73,
Don W3FPR

On 8/4/2016 8:41 PM, Fred Jensen wrote:
>  All this "matching bafflegab" was unheard of when I was a young ham.  
> You fed your dipole with 75 ohm twin-lead, coupled it to the PA with a
> 2 or 3 turn link coil, and as the reactance of the link changed the
> resonance, you compensated by "re-dipping the plate."
>
> Of course, when I was a young ham, dirt was pretty young too. :-)
>

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Re: OT:. G5RV's

Don Wilhelm
In reply to this post by Nr4c
Bill,

That is correct, but the currents on the 33 feet feedline should be
balanced and of opposite polarity - so they cancel.  The current at the
radiator center will be less than that of a full size 80 meter radiator,
so it will be less efficient than a full size 80 meter dipole with the
current maximum at the feedpoint center.

There are numerous ways to phrase this, but bottom line is that a 102
foot radiator on 80 meters will not be as good an antenna as a full size
radiator.  The current will be at a max at the parallel line to coax
junction, but will be reduced when the current magnitude reaches the
radiator.

Low SWR does not mean radiation efficiency.

Low SWR does mean the best efficiency for a match to a 50 ohm PA stage,
but the overall radiation efficiency depends on the antenna and its
feedline.  One has to compute the losses involved as well as the current
into the antenna system.

Of course, I must say that if you can feed power into an antenna system,
that power will all be radiated (other than feedline loss).  In the
example given for a 102 foot radiator, the balanced currents on the
feedline will not contribute to power loss - the current on that
balanced portion of the feedline will be greater than that presented to
the antenna, and the balanced feedline will be operating at an SWR
consistent with the impedance at that feedpoint.

As I have previously stated, there is little "magic" in antennas - the
principles have been around since the days of Maxwell and other greats
such as L.B Cebik W4LNR (SK) and John Kraus W8JK (SK) who have
substantiated those facts.  Non-resonant antennas can be great
performers, but one must deal with the feedpoint impedances that they
present.  Those two antenna gurus did not consider the matching problems
to their antennas, they properly presented the antenna radiation properties.

73,
Don W3FPR

73,
Don W3FPR

On 8/4/2016 8:34 PM, Nr4c wrote:
> Let's see,  102 + 33 = 135. Isn't that pretty close to the length of an 80 Meter Dipole?  The G5RV looks like two back-to-back inverted "L" antennas. The twin lead is not feed line but part of the radiator.
>
>

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Re: OT:. G5RV's

Wes Stewart-2
In reply to this post by Nr4c
I know handbook descriptions have declared this for years.  They're simply
wrong.  The folded part is a transmission line, it doesn't radiate and it has an
impedance different from the antenna.  Why not just add a hundred feet or so of
transmission line to a 10' dipole and call it a 160 antenna? Doesn't work, does
it?  Use the same logic on your example and it doesn't work either.  Sorry.

On 8/4/2016 5:34 PM, Nr4c wrote:
> Let's see,  102 + 33 = 135. Isn't that pretty close to the length of an 80 Meter Dipole?  The G5RV looks like two back-to-back inverted "L" antennas. The twin lead is not feed line but part of the radiator.
>
> Sent from my iPhone
> ...nr4c. bill
>

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Re: OT:. G5RV's

Wes Stewart-2
In reply to this post by k6dgw
I guess a little discussion of semantics is in order.  Yes, EZNEC shows for
example, that a 12 AWG wire, 102' long and say 50' above avg ground shows an
impedance of ~98 +j0 at 14.32 MHz, so it is resonant in the 20-meter band,
because the reactance is zero, and it could be called a "resonant dipole.".  
However, It also shows resonances at 4.61, 9.45, 18.74, 23.92 and 28.40 MHz. In
common ham jargon as I called it, this length would not be considered a resonant
dipole for those frequencies other than 4.61 MHz where it is one half wavelength
long.

But if someone wants to call it a 20-meter dipole, be my guest.

On 8/4/2016 3:22 PM, Fred Jensen wrote:
> Ummm ... my HP48GX says 102' is very very close to 3 half-waves at 14 MHz
> which sounds sort of resonant-ish.  Maybe a little known bug in my calculator?
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Re: OT:. G5RV's

Wes Stewart-2
In reply to this post by Alan Bloom
The tuner loss also depends on how it is adjusted.  For example the very popular
high-pass Tee with three adjustable elements has an infinite number of possible
combinations that will effect a match on the same load Z.  One of them is the
lowest loss solution, all of the others aren't.

As I said earlier, in a letter to Dean Straw dated February 2, 1994 I offered an
example where the SPC tuner, then current in the handbooks, could be used to
match an impedance of 4.34 +j46 to 50 ohm. (I forget where this came from but it
was a real possibility)  I assumed Qc = 1000 and Ql = 300 (generous). I used
Touchstone to calculate the minimum loss and maximum loss solutions The best
case was 1.6 dB and the worst case was 7.8 dB.

With lower Q components, Qc = 500, Ql =200, the losses were 2.4 to 9.5 dB!

Wes  N7WS


  On 8/4/2016 2:00 PM, Alan Bloom wrote:

> > It's a pity that too many newcomers, as well as many oldsters, are
> > enamored by this piece of wire.
>
> The G4RV is definitely a compromise antenna.  However its advantage is that is
> has low-enough SWR to be easily matched by most tuners on a number of bands.
>
> > ... the horrific losses that could be incurred even
> > with high quality tuners,
>
> It's true that tuner losses are the manufacturers' dirty little secret. Loss
> is rarely specified, partly because it can be pretty bad, and partly because
> it is hard to measure, but also because it is not constant - it depends on the
> particular impedance being matched.
>
> One exception is the old Drake tuners.  Their Pi-L topology makes the loss
> almost independent of the load impedance.  If you can get it to match, you
> know that almost all the power is going into the feed line. For example, the
> MN-2700 that I designed when I was at Drake was specified at 0.5 dB maximum
> insertion loss and I did a lot of testing and tweaking to achieve that on all
> bands.
>
> Alan N1AL

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Re: OT:. G5RV's

Alan. G4GNX
In reply to this post by Don Wilhelm
Don,

With respect for your wisdom and your good advice, in the UK in particular
(home of the G5RV) the 'ordinary' ham has real-estate issues, big time!

Louis Varney's garden/back yard was of average British size, which is
actually quite small when compared to 'average' gardens that I've seen in
the USA. That was his prime reason for designing a compact wire antenna.

We have other issues with planning regulations and erecting a mast or tower
over 40ft in height would probably meet with a brick-wall attitude from the
local planning authorities. Attitudes towards structures in the UK are very
different to the USA and there are many snobs who claim offense when they
see something that appears above the roof line of an average house.

My back yard is even smaller than Louis's and I just don't have space for
lengthy wires or even slopers. Even erecting tall supports is difficult as
there's limited ground to dig holes to fill with concrete supports.

Maybe in the USA, the use of G5RV antennas doesn't make too much sense, but
to us Brits, compact antennas are often the only thing we can use.


73,

Alan. G4GNX

-----Original Message-----
From: Don Wilhelm
Sent: Friday, August 05, 2016 12:41 AM
To: [hidden email]
Subject: Re: [Elecraft] OT:. G5RV's

Wes and all,

Yes, the G5RV, the Off-Center-Fed antennas (Carolina Windom for one
example) and the 43 foot vertical have become "magical" antennas, and I
am not certain why.

My best guess is that they are "salvation" for hams who want to operate
on multiple bands with one antenna, and they can be made to "work" in
one fashion or another.

All need a tuner of some sort, and the 43 foot vertical needs a remote
tuner at the base for efficient operation, or at least a matching
section for each band at the base for efficient operation.  One could
feed that vertical with low loss open wire line and put the matching
tuner in the shack, but most choose to feed with coax along with the
attendant losses incurred if no matching is done at the vertical base.

IMHO, resonant fan dipoles are a much better solution - whether those be
constructed as inverted Vee's or whether as parallel dipoles separated
by 1 foot or more to reduce interaction.

I use resonant parallel dipoles here.  The 80 and 40 inverted vee's are
supported on a 50 foot tower and the 80 meter legs are perpendicular to
the 40 meter legs, so there is no interaction.

I have another 3 band band fan dipole for 20, 15, and 10 hung as a
horizontal dipole with the radiators separated 1 foot from each other
(other than at the center point) and a similar 3 band fan dipole for 30,
17, and 12 meters.
That means 3 coax lines into the shack, or a remote antenna switch -
which I use because I have other antennas to deal with, a 60 meter
inverted vee, and a Gap Titan vertical.

As far as I am concerned, resonant dipoles are the preferred solution.
Other antennas may work, but are a compromise, and some (particularly
the OCF antennas) produce RF-in-the-Shack that can be difficult to suppress.

There is no "magic" with antennas.  Some antenna designs were created
when we had PA output circuits that could handle a wide range of antenna
impedances and used low loss open wire feedlines.  That is no longer the
case with the transceiver (or amplifier) that needs to operate into a 50
ohm load, and ATUs with limited matching range.

So take your pick and know the hazards and consequences of that choice.
Any antenna that you can feed power to will radiate, but some do it
better than others.  My choice is to use center fed dipoles which at any
length can be easily tamed, and I shy away from the OCF antennas which
can create RF-in-the-Shack problems.
There is no "magic" with antennas, the knowledge base for radiation from
a wire (or piece of aluminum) has been around for many long years, but
the resulting feedpoint impedance is what we commonly deal with along
with all its hazards and consequences.

73,
Don W3FPR

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