Homebrew Dipole help please?
 

Hi
We have put together a dipole, each leg is 66 feet. We put a 1:1 balun and
it is running about 60 feet of 50 ohm coax. Presently it is about half way
up the tower it is intended for so we could check the SWR before getting it
up to the highest point. Presently each leg has some lags and dips, no major
bends but it is just hanging there, over some bushes and the entire thing is
over top of the house, and not touching anything but is very close to some
steel guy wires (uninsulated).
Now we can only tune this down to a useable SWR on the 80m band. On all
other bands we cannot tune it down to a safe operating range. We are using a
good antenna tuner but cannot get anything useable except for 80m. Here we
are able to tune the SWR right down.

Questions???
Would we be better without that balun?

Is the fact that the dipole is still too low and close to the guy wires (
but not touching) our problem?

Any suggestions please??

Thank you.
Bob

We have put together a dipole, each leg is 66 feet.

Bob-

The feedpoint of a halfwave dipole in free space is about 72 Ohms, which would
result in 1.44 to 1 SWR. A real-world dipole sill be a little different, and
it might be possible to trim it close to 1 to 1.

Your dipole is about halfwave on the 80m band, so it should work there.
However, it is a full wave on the 40m band, two waves on 20m, three waves on
15m, 4 waves on 10m. The input of a full wave antenna (and presumably
multiples of a full wave) is extremely high. It might be higher than your
tuner can match.

The best transmission line may be some kind of balanced open wire feeder, but
you still would have a high impedance to match. One of the old Viking Matchbox
tuners may be capable of matching it without using a BalUn, but changing to a
balance feedline might be all you need to do.

Another alternative is to use a "Trap Dipole" that has parallel-tuned traps at
the ends of the 40m sections. Such a dipole is often shorter on 80m due to the
trap's inductive loading. There are some versions that may have additional
traps for higher frequencies, but just adding the 40m set may make it tuneable
on the other bands. I have one with just the 40m traps that came with a balun
in the center, that worked "OK" on 80m through 10m using a tuner. (It is
twenty years old now, so may not be working as well as it used to.)

73, Fred, K4DII

We have put together a dipole, each leg is 66 feet.

Bob-

The feedpoint of a halfwave dipole in free space is about 72 Ohms, which would
result in 1.44 to 1 SWR. A real-world dipole sill be a little different, and
it might be possible to trim it close to 1 to 1.

Your dipole is about halfwave on the 80m band, so it should work there.
However, it is a full wave on the 40m band, two waves on 20m, three waves on
15m, 4 waves on 10m. The input of a full wave antenna (and presumably
multiples of a full wave) is extremely high. It might be higher than your
tuner can match.

The best transmission line may be some kind of balanced open wire feeder, but
you still would have a high impedance to match. One of the old Viking Matchbox
tuners may be capable of matching it without using a BalUn, but changing to a
balance feedline might be all you need to do.

Another alternative is to use a "Trap Dipole" that has parallel-tuned traps at
the ends of the 40m sections. Such a dipole is often shorter on 80m due to the
trap's inductive loading. There are some versions that may have additional
traps for higher frequencies, but just adding the 40m set may make it tuneable
on the other bands. I have one with just the 40m traps that came with a balun
in the center, that worked "OK" on 80m through 10m using a tuner. (It is
twenty years old now, so may not be working as well as it used to.)

73, Fred, K4DII

"Bob" wrote in message ...
Hi
We have put together a dipole, each leg is 66 feet. We put a 1:1 balun and
it is running about 60 feet of 50 ohm coax. Presently it is about half way
up the tower it is intended for so we could check the SWR before getting it
up to the highest point. Presently each leg has some lags and dips, no major
bends but it is just hanging there, over some bushes and the entire thing is
over top of the house, and not touching anything but is very close to some
steel guy wires (uninsulated).
Now we can only tune this down to a useable SWR on the 80m band.

That is normal, without the tuner...
On all
other bands we cannot tune it down to a safe operating range. We are using a
good antenna tuner but cannot get anything useable except for 80m. Here we
are able to tune the SWR right down.

Thats not totally normal, but could be a tuner deficiency...

Questions???
Would we be better without that balun?

No, it's 1:1.

Is the fact that the dipole is still too low and close to the guy wires (
but not touching) our problem?

That can mess things up, for sure.

Any suggestions please??

#1, feeding an all band dipole with coax is a mistake. Your feed
losses will be very high on most all other bands, except 80. If you
want to use it for all bands with a tuner, you would be better off
feeding it with ladder line, or twin lead. MK

"Bob" wrote in message ...
Hi
We have put together a dipole, each leg is 66 feet. We put a 1:1 balun and
it is running about 60 feet of 50 ohm coax. Presently it is about half way
up the tower it is intended for so we could check the SWR before getting it
up to the highest point. Presently each leg has some lags and dips, no major
bends but it is just hanging there, over some bushes and the entire thing is
over top of the house, and not touching anything but is very close to some
steel guy wires (uninsulated).
Now we can only tune this down to a useable SWR on the 80m band.

That is normal, without the tuner...
On all
other bands we cannot tune it down to a safe operating range. We are using a
good antenna tuner but cannot get anything useable except for 80m. Here we
are able to tune the SWR right down.

Thats not totally normal, but could be a tuner deficiency...

Questions???
Would we be better without that balun?

No, it's 1:1.

Is the fact that the dipole is still too low and close to the guy wires (
but not touching) our problem?

That can mess things up, for sure.

Any suggestions please??

#1, feeding an all band dipole with coax is a mistake. Your feed
losses will be very high on most all other bands, except 80. If you
want to use it for all bands with a tuner, you would be better off
feeding it with ladder line, or twin lead. MK

Hi all

I have it back up without the balun, and still have to use the coax for now.
I am able to tune it now on all bands but I am sure there is a lot of power
loss from the tuner. I grounded out all devices in the shack but still
receiving a lot of RF interference on tv, computer, and home alarm.
Thanks for all the advice, really appreciate it.





"Mark Keith" wrote in message
om...
"Bob" wrote in message
...
Hi
We have put together a dipole, each leg is 66 feet. We put a 1:1 balun
and
it is running about 60 feet of 50 ohm coax. Presently it is about half
way
up the tower it is intended for so we could check the SWR before getting
it
up to the highest point. Presently each leg has some lags and dips, no
major
bends but it is just hanging there, over some bushes and the entire
thing is
over top of the house, and not touching anything but is very close to
some
steel guy wires (uninsulated).
Now we can only tune this down to a useable SWR on the 80m band.

That is normal, without the tuner...
On all
other bands we cannot tune it down to a safe operating range. We are
using a
good antenna tuner but cannot get anything useable except for 80m. Here
we
are able to tune the SWR right down.

Thats not totally normal, but could be a tuner deficiency...

Questions???
Would we be better without that balun?

No, it's 1:1.

Is the fact that the dipole is still too low and close to the guy wires
(
but not touching) our problem?

That can mess things up, for sure.

Any suggestions please??

#1, feeding an all band dipole with coax is a mistake. Your feed
losses will be very high on most all other bands, except 80. If you
want to use it for all bands with a tuner, you would be better off
feeding it with ladder line, or twin lead. MK

Hi all

I have it back up without the balun, and still have to use the coax for now.
I am able to tune it now on all bands but I am sure there is a lot of power
loss from the tuner. I grounded out all devices in the shack but still
receiving a lot of RF interference on tv, computer, and home alarm.
Thanks for all the advice, really appreciate it.





"Mark Keith" wrote in message
om...
"Bob" wrote in message
...
Hi
We have put together a dipole, each leg is 66 feet. We put a 1:1 balun
and
it is running about 60 feet of 50 ohm coax. Presently it is about half
way
up the tower it is intended for so we could check the SWR before getting
it
up to the highest point. Presently each leg has some lags and dips, no
major
bends but it is just hanging there, over some bushes and the entire
thing is
over top of the house, and not touching anything but is very close to
some
steel guy wires (uninsulated).
Now we can only tune this down to a useable SWR on the 80m band.

That is normal, without the tuner...
On all
other bands we cannot tune it down to a safe operating range. We are
using a
good antenna tuner but cannot get anything useable except for 80m. Here
we
are able to tune the SWR right down.

Thats not totally normal, but could be a tuner deficiency...

Questions???
Would we be better without that balun?

No, it's 1:1.

Is the fact that the dipole is still too low and close to the guy wires
(
but not touching) our problem?

That can mess things up, for sure.

Any suggestions please??

#1, feeding an all band dipole with coax is a mistake. Your feed
losses will be very high on most all other bands, except 80. If you
want to use it for all bands with a tuner, you would be better off
feeding it with ladder line, or twin lead. MK