G5RV Balun ?

[Gary]

I've looked at several commercial G5RV's and most seem to lack a balun
when the coax is connected to the 450 Ohm ladder line. I would suspect
a 4:1 balun at the coax to ladder line connection would make for a
better operating antenna or perhaps running the ladder line into the
shack here to the 4:1 balun built into my tuner. Though the normal
length of the ladder line coming off the G5RV may not be long enough
to reach my tuner, much less the problem of keeping it away from the
aluminum siding, tower etc. Would my best bet be to get a 4:1 balun
and feed that one end with coax and the other end with the ladder
line of the G5RV ?

Any input appreciated.

Thanks in advance !

73 Gary

[KC1DI]

Hi Gary,

The impedence at the input end of the twin lead is low on most bands ,
thus there is no need for and impedence transformation at that point. A
1:1 Choke balun is a good Idea to keep RF off the Sheild of the Coax.
But I've used the G5RV both with and without a Choke and they both will
will quite well. If you put a 4:1 balun in the system you will be
bringing the impedence down to about 17 ohms on 20 meters for instance.
not a good match to 50 ohm Coax. The best thing would be to bring the
Ladder line all the way to a balnced tuner in the shack. But the one
with coax will work quite well Especially on 40 & 20 Meters. There is a
lot of info on the net about the G5RV some good Some questionable.

hope this helps 73 , Dave KC1DI

[Cecil Moore]

Gary wrote:
> I've looked at several commercial G5RV's and most seem to lack a balun
> when the coax is connected to the 450 Ohm ladder line.

Some G5RV manufacturers know that most hams don't realize they
need a balun and a balun increases cost and decreases profit.

> I would suspect
> a 4:1 balun at the coax to ladder line connection would make for a
> better operating antenna or perhaps running the ladder line into the
> shack here to the 4:1 balun built into my tuner.

Nope, a 1:1 current choke is what one needs. For instance, the
resonant impedance at the coax/twinlead junction on 80m is about
10 ohms for a 5:1 SWR on the coax. A 4:1 balun would take it to
2.5 ohms for a 20:1 SWR on the coax. A 4:1 balun at the coax to
twinlead junction makes a G5RV worse, not better.
--
73, Cecil http://www.qsl.net/w5dxp

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[F8BOE]

Hello,

The G5RV as you describe it is a farce!

If you have a balanced tuner (symetrical), ladder-line and two pieces of
wire, you can simply construct a Levy antenna. It works great on most HF
bands depending on the tuner's quality and you can even get the 160m band
with 2 x 20m dipole and 15 to 17 m twinlead.

73 de F8BOE Olivier ...-.-

[Bob Miller]

see Louis Varney's article at:

http://www.qsl.net/aa3px/g5rv.htm

he has a few words on feedlines, baluns, etc...

bob
k5qwg

[Ingo Braun]

Bob Miller schrieb:

of course ...

the G5RV is much the same as the double-zepp or doublet antenna !

if you have an antenna tuner with balanced line connector, you dont
need a balun ... just keep the ladder line 12.80m for current coupling,
or keep it 23.60m for voltage coupling. the legs will be 41m together !

this is proved antenna and it works very good from 160m to 10m !

[Reg Edwards]

> The G5RV as you describe it is a farce!
>

================================

Thank heavens for the logical, common sense of a Frenchman.

Vive L'entante Cordiale.
----
G4FGQ

[Reg Edwards]

The best rearrangement by far, for a G5RV, is to use a 600-ohm
open-wire line all the way from the dipole to the shack. With a few
feet extra just as a precaution.

You could also beneficially increase the length of the dipole if you
have enough room in your back yard. Another 10 or 20 feet would do no
harm.

[Mike Coslo]

Good advice Reg. Is it a G5RV any more tho'?

- Mike -