Log periodic mounting

I'm using a Vision V10-040 Super Log Periodic aerial but thought the
supplied tail mount was a bit weedy for 1.2m of double boom metalwork,
it felt as if it was really wanting to droop as I was fitting it.

I decided to try it with a U-bracket mounted underneath and used a spare
with a tilt adjustment to get the nose up to point just above horizon.

Here's a pic: http://i40.tinypic.com/33dz04x.jpg

Is there any risk of the U-bracket upsetting the aerial characteristics?

I don't think so but I've never seen a log mounted like this, is it just
because logs are short & light or is there another reason?
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

"fred" wrote in message ...
I'm using a Vision V10-040 Super Log Periodic aerial but thought the
supplied tail mount was a bit weedy for 1.2m of double boom metalwork, it
felt as if it was really wanting to droop as I was fitting it.

I decided to try it with a U-bracket mounted underneath and used a spare
with a tilt adjustment to get the nose up to point just above horizon.

Here's a pic: http://i40.tinypic.com/33dz04x.jpg

Is there any risk of the U-bracket upsetting the aerial characteristics?

I don't think so but I've never seen a log mounted like this, is it just
because logs are short & light or is there another reason?
--
fred

The twin booms of this log periodic are effectively a transmission line.

For this reason the LP should be insulated from the supporting stub-mast.

Mechanically it looks robust but electrically it is a disaster.

This LP could be mounted to the stub-mast (at the centre of gravity - ie not
at the exact centre of the boom) but you must use insulating spacers where
the clamp attaches to the twin booms.

Cheers, David

I have a very old log here and the U bracket has the tops of the arms of the
U made of plastic so it won't short out the transmission line/boom.
Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"fred" wrote in message ...
I'm using a Vision V10-040 Super Log Periodic aerial but thought the
supplied tail mount was a bit weedy for 1.2m of double boom metalwork, it
felt as if it was really wanting to droop as I was fitting it.

I decided to try it with a U-bracket mounted underneath and used a spare
with a tilt adjustment to get the nose up to point just above horizon.

Here's a pic: http://i40.tinypic.com/33dz04x.jpg

Is there any risk of the U-bracket upsetting the aerial characteristics?

I don't think so but I've never seen a log mounted like this, is it just
because logs are short & light or is there another reason?
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

In article , David Butler
writes

The twin booms of this log periodic are effectively a transmission line.

For this reason the LP should be insulated from the supporting stub-mast.

Mechanically it looks robust but electrically it is a disaster.

This LP could be mounted to the stub-mast (at the centre of gravity - ie not
at the exact centre of the boom) but you must use insulating spacers where
the clamp attaches to the twin booms.

Thanks for the explanation, yes, that makes sense.

I suppose I could modify it with insulated saddles per Brian's example
but I'd be wondering if a few pF of stray capacitance to the bracket
through my bodged insulation was affecting things.

To remove all doubt, I think I'll go back to a tail mount and try to
beef things up there, opening up the holes in the Vision to take a
bigger clamp and mod it a bit more to give it a firmly lockable tilt.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

In article , Brian Gaff
writes
I have a very old log here and the U bracket has the tops of the arms of the
U made of plastic so it won't short out the transmission line/boom.
Brian

Thanks, is the plastic thick to keep a good distance between the 'live'
arms and the brackets, and is it exotic plastic like PTFE or just PVC?

I think I'll take the easy route and go back to a tail mount but it
would be nice to hear how others have done it.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

"Brian Gaff" wrote in message
m...
I have a very old log here and the U bracket has the tops of the arms of
the U made of plastic so it won't short out the transmission line/boom.
Brian

That's the Antiference TS21. See:

http://www.wrightsaerials.tv/aerialp...cient/047.html

Bill

"fred" wrote in message ...
In article , Brian Gaff
writes
I have a very old log here and the U bracket has the tops of the arms of
the
U made of plastic so it won't short out the transmission line/boom.
Brian

Thanks, is the plastic thick to keep a good distance between the 'live'
arms and the brackets, and is it exotic plastic like PTFE or just PVC?

I think I'll take the easy route and go back to a tail mount but it would
be nice to hear how others have done it.

I've been worried by this, because we sometimes put aerials in very exposed
locations. I have some spare parts for Blake logs and these let me fit two
clamps on above the other.

Bill

This is made by Antiference and the plastic is basically inserts of some
black plastic with holes drilled for the bolts. Its not sophisticated. The
main thing is to use a plastic which does not degrade when out of doors I'd
imagine.
Why are you using a log? I used to use it as it was super wide band and had
a clean polar responce.
21 element.
Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"fred" wrote in message ...
In article , Brian Gaff
writes
I have a very old log here and the U bracket has the tops of the arms of
the
U made of plastic so it won't short out the transmission line/boom.
Brian

Thanks, is the plastic thick to keep a good distance between the 'live'
arms and the brackets, and is it exotic plastic like PTFE or just PVC?

I think I'll take the easy route and go back to a tail mount but it would
be nice to hear how others have done it.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

As these designs do vary though the basic idea is the same its odd that
they just do not do as this early version did. It was on my chimney on a
rotator for over 14 years and is still good but at the moment its in my
shed.

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Bill Wright" wrote in message
...

"fred" wrote in message ...
In article , Brian Gaff
writes
I have a very old log here and the U bracket has the tops of the arms of
the
U made of plastic so it won't short out the transmission line/boom.
Brian

Thanks, is the plastic thick to keep a good distance between the 'live'
arms and the brackets, and is it exotic plastic like PTFE or just PVC?

I think I'll take the easy route and go back to a tail mount but it would
be nice to hear how others have done it.

I've been worried by this, because we sometimes put aerials in very
exposed locations. I have some spare parts for Blake logs and these let me
fit two clamps on above the other.

Bill

Yes well I'm sure it is.. cannot see it myself any more. The only weak link
was that bit of thin coax and the enclosed socket, but it does still work
see my earlier post.
Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Bill Wright" wrote in message
...

"Brian Gaff" wrote in message
m...
I have a very old log here and the U bracket has the tops of the arms of
the U made of plastic so it won't short out the transmission line/boom.
Brian

That's the Antiference TS21. See:

http://www.wrightsaerials.tv/aerialp...cient/047.html

Bill