Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out of
my shack window but I would like to use a low loss ladder line for the main
run up to the antenna feed point. Is it OK to place a 4:1 balun just outside
of the window for the transition?

Kash, AG4EL

"Kash J. Rangan" wrote in message
...
Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out
of my shack window but I would like to use a low loss ladder line for the
main run up to the antenna feed point. Is it OK to place a 4:1 balun just
outside of the window for the transition?

Kash, AG4EL


you can, but how long of a run will it be from the shack to the antenna??
unless it is a very long distance just go with the coax... the added loss
and complexity of the balun and then the mismatch of the ladder line to the
dipole at the far end is probably going to be more than just going with coax
all the way.

On Jun 10, 3:36�pm, "Kash J. Rangan" wrote:
Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out of
my shack window but I would like to use a low loss ladder line for the main
run up to the antenna feed point. Is it OK to place a 4:1 balun just outside
of the window �for the transition?

Kash, AG4EL

The G5RV antenna uses a combination of coax and ladder line, so this
type of antenna is in use by 1000's of Hams.

The 4:1 balun is a bad idea for a multiband antenna, due to the
impedances involved at the various operating frequencies. Just
transistion from the ladder line to the coax and use a 1:1 choke balun
at the antenna input of your tuner. You did not mention an antenna
tuner, but you will need one for multiband operation.

In general keep the coax length as short as possible.

Gary N4AST

In message
,
writes
On Jun 10, 3:360 Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out of
my shack window but I would like to use a low loss ladder line for the main
run up to the antenna feed point. Is it OK to place a 4:1 balun just outside
of the window 0
Kash, AG4EL

The G5RV antenna uses a combination of coax and ladder line, so this
type of antenna is in use by 1000's of Hams.

The 4:1 balun is a bad idea for a multiband antenna, due to the
impedances involved at the various operating frequencies. Just
transistion from the ladder line to the coax and use a 1:1 choke balun
at the antenna input of your tuner. You did not mention an antenna
tuner, but you will need one for multiband operation.

In general keep the coax length as short as possible.

If I remember correctly, the original design of the G5RV does NOT use
coax. [If interested, check it out on Google.]
--
Ian

If I remember correctly, the original design of the G5RV does NOT use
coax. [If interested, check it out on Google.]
--
Ian- Hide quoted text -

- Show quoted text -

I think you are right. Most of the commercial antennas called "G5RV"
have coax supplied with them or instruct you to attach a certain
length coax.

One of Reg Edwards programs, Dipole3 models a twin lead-coax miltiband
antenna. It also has a G5RV feature.

Gary N4AST

wrote in message
...
On Jun 10, 3:36?pm, "Kash J. Rangan" wrote:
Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out
of
my shack window but I would like to use a low loss ladder line for the
main
run up to the antenna feed point. Is it OK to place a 4:1 balun just
outside
of the window ?for the transition?

Kash, AG4EL

The G5RV antenna uses a combination of coax and ladder line, so this
type of antenna is in use by 1000's of Hams.

The 4:1 balun is a bad idea for a multiband antenna, due to the
impedances involved at the various operating frequencies. Just
transistion from the ladder line to the coax and use a 1:1 choke balun
at the antenna input of your tuner. You did not mention an antenna
tuner, but you will need one for multiband operation.

In general keep the coax length as short as possible.

Gary N4AST


Another thing to consider is that the length of the 450/300 ohm twinlead
feedline is an important factor when considering the operational bandwidth
of said "dipole" antenna (it's only a dipole when operated at its resonant
length).

The twinlead is utilized as part of the radiating system when operated on
certain bands. This unusual impedance is why the tuner is needed. Shortening
the twinlead and using more coax limits this antenna's ability to operate
over wide frequency ranges. My Van Gordan All Bander's twinlead enters my
shack and then connects to a balun, which is then fed by coax that is
connected to my MFJ-989C tuner. I can often tune down into the 160 meter
band using this setup, though I wish my twinlead feedline length was a bit
longer for even greater tuning flexibility.

By the way, my All Bander also works great on six meters.


Ed, AJ4PJ

"Kash J. Rangan" writes:

Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out of
my shack window but I would like to use a low loss ladder line for the main
run up to the antenna feed point. Is it OK to place a 4:1 balun just outside
of the window for the transition?

I use a combination of window line and coax for my 80m antenna. I
don't have enough space for a full size dipole, so I had to shorten it
somewhat. From memory, about 6m of window line makes up for about 3m
of missing wire on each dipole leg. Easier to do than loading coils,
that's why. EZNEC claims that losses are negligible, don't know if
that's really so or a transmission line model is inappropriate here.

Totally by accident, the antenna also ended up with a resonance in the
30m band.

Jon LA4RT, Trondheim, Norway

In Varney's original r.s.g.b. article in July 1958 he showed it both
ways, 100% open wire feeder to a tuner, or 34' of open wire feeder to
any length of 72 ohm coax or twin lead to a tuner or the transmitter.

bob
k5qwg

On Thu, 11 Jun 2009 10:43:38 +0100, Ian Jackson
wrote:

In message
,
writes
On Jun 10, 3:360 Is it advisable to use a combination of Coax and a ladder line to feed a
simple horizontal multiband dipole antenna?

In my new QTH it would be very easy for me to get a short run of coax out of
my shack window but I would like to use a low loss ladder line for the main
run up to the antenna feed point. Is it OK to place a 4:1 balun just outside
of the window 0
Kash, AG4EL

The G5RV antenna uses a combination of coax and ladder line, so this
type of antenna is in use by 1000's of Hams.

The 4:1 balun is a bad idea for a multiband antenna, due to the
impedances involved at the various operating frequencies. Just
transistion from the ladder line to the coax and use a 1:1 choke balun
at the antenna input of your tuner. You did not mention an antenna
tuner, but you will need one for multiband operation.

In general keep the coax length as short as possible.

If I remember correctly, the original design of the G5RV does NOT use
coax. [If interested, check it out on Google.]

I agree with Gary N4AST: the direct answer to your question is:

* Use the shortest length of good quality coax you can get away with.
* Use a good quality 1:1 current (choke) balun at the ladderline/coax
junction.
* If you find the tuner can't reach a match on some bands, only then
consider a 4:1 balun; even so choose a 4:1 **current** balun.

On the topic of G5RVs, some (unscrupulous) antenna suppliers provide a
nice long length of RG58 as part of the package to "tame" the VSWRs.
Take a look at some of the losses that introduces:
http://www.karinya.net/g3txq/g5rv/

73,
Steve G3TXQ

Ed Cregger wrote:

Another thing to consider is that the length of the 450/300 ohm twinlead
feedline is an important factor when considering the operational bandwidth
of said "dipole" antenna (it's only a dipole when operated at its resonant
length).


I have to chuckle when you bring this up in a discussion of that true
chimera, the G5RV. I've heard so many antennas called G5RV's that the
term means nothing any more - kinda of like scotch tape.

So yeah, I guess we should call it a doublet. Of course, all doublets
are dipoles at some point, and all dipoles are doublets.......

- 73 de Mike N3LI -