[OT] Best FM aerial?

Thing that is bugging/puzzling me is the amount of signal I get off
the
co-ax.


This sounds as if the receiver is not matched to the feeder. Could it
be that the receiver has a balanced RF input, even though the socket is
coaxial? If that is the case it would pick up a lot of signal on the
coax, and would make all attempts to use an aerial at the other end of
the cable rather pointless.
If the receiver does have a balanced input (be it 75ohm or 300ohm), you
need a balun.
If the aerial socket on the receiver is isolated from the chassis you
can test my hypothesis by connecting the braid and leaving the inner
unconnected. If this results in a signal of any strength being received
then the socket is connected to a balanced tuner input.

Bill
Bill

"Arthur" wrote in message
news
On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts
wrote:
snip
Might be better to post them *before* the scaffolding is down.

Arthur

Again apologies for image size.

http://www.chelsworth-lodge.nildram....NewAerials.jpg

The chimney brackets are a bit close together and grip less of the pole than
is ideal, but they are pretty hefty and feel very solid and secure.

The pole grip compromise comes from two things.

(1) There isn't that much chimney above the ridge to get wires around.

(2) The aim is to get the TV aerial as high as possible to see over
Felixstowe docks.

The standoff for the FM aerial is also a compromise because the aerial comes
with a wall/chimney mount so I had to source additional bits and pieces.
However it is the suggested 1.5m away from the main pole, and pointing
towards Manningtree.

I have not charged the scaffolding firm for the free advert :-)

Cheers
Dave R

On Thu, 13 Jan 2005 10:47:47 -0000, David W.E. Roberts
wrote:


"Arthur" wrote in message
news
On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts

wrote:
snip
Might be better to post them *before* the scaffolding is down.

Arthur

Again apologies for image size.

http://www.chelsworth-lodge.nildram....NewAerials.jpg

The chimney brackets are a bit close together and grip less of the pole
than
is ideal, but they are pretty hefty and feel very solid and secure.

The pole grip compromise comes from two things.

(1) There isn't that much chimney above the ridge to get wires around.

(2) The aim is to get the TV aerial as high as possible to see over
Felixstowe docks.

The standoff for the FM aerial is also a compromise because the aerial
comes
with a wall/chimney mount so I had to source additional bits and pieces.
However it is the suggested 1.5m away from the main pole, and pointing
towards Manningtree.

I have not charged the scaffolding firm for the free advert :-)


Thanks for the picture. I'm sure that as the acknowledged expert on
aerial installation, Bill will give the definitive judgement, but my
comments are these:
- The standoff for the FM dipole is greater than necessary. As previously
discussed, a quarter-wave spacing is probably all you need. The long
boom, hit with a sideways wind, may cause some twisting of the brackets -
or worse, of the whole pole which will take the TV aerial off its correct
heading.
- the overall height in comparison with the bracket spacing, looks just a
*little* long for an exposed coastal position. But at least you are not on
a hilltop.
- I note you have used nylon cable ties to fix the coax to the pole, and
trust that you have not fallen into the trap of over-tightening them which
causes crushing of the coax.

Arthur

On Thu, 13 Jan 2005 11:50:54 -0000, Arthur wrote:

Thanks for the picture. I'm sure that as the acknowledged expert on
aerial installation, Bill will give the definitive judgement, but my
comments are these:
- The standoff for the FM dipole is greater than necessary. As
previously discussed, a quarter-wave spacing is probably all you need.
The long boom, hit with a sideways wind, may cause some twisting of the
brackets - or worse, of the whole pole which will take the TV aerial off
its correct heading.
- the overall height in comparison with the bracket spacing, looks just
a *little* long for an exposed coastal position. But at least you are
not on a hilltop.
- I note you have used nylon cable ties to fix the coax to the pole, and
trust that you have not fallen into the trap of over-tightening them
which causes crushing of the coax.


Also I'm not sure why you have put a 'dog leg' on the dipole support.
Couldn't you have fitted the dipole dirctly onto to stand-off from the
main pole?


Arthur

Thanks for the picture. I'm sure that as the acknowledged expert on
aerial installation,
Cringe making!

Bill will give the definitive judgement, but my
comments are these:
The standoff for the FM dipole is greater than necessary. As
previously
discussed, a quarter-wave spacing is probably all you need. The long
boom, hit with a sideways wind, may cause some twisting of the brackets
-
or worse, of the whole pole which will take the TV aerial off its
correct
heading.
Agreed. The FM aerial is made by Vision (but rebadged I expect). They
have a stupid short side arm, but there's really no need to put it this
far from the mast. Decide on a direction you don't care about (Europe?)
and put the aerial on the side of the mast away from that direction,
about a quarter wavelength away. By the way, those aerials have better
bandwidth than a simple dipole. They are significantly better at the
ends of the FM band.

the overall height in comparison with the bracket spacing, looks just
a
*little* long for an exposed coastal position. But at least you are not
on
a hilltop.
Agreed. Is the mast a scaffolding tube? I hope so. If so it should be
OK.

I note you have used nylon cable ties to fix the coax to the pole,
and
trust that you have not fallen into the trap of over-tightening them
which
causes crushing of the coax.
Agreed. Also, the masthead amp will be out of reach if it ever goes
wrong. They should always be fitted within reach.

Having said all this the job is a damn sight better than most DIY
aerials I get to see!

Bill

On 13 Jan 2005 04:04:17 -0800, "
wrote:

Thanks for the picture. I'm sure that as the acknowledged expert on
aerial installation,
Cringe making!

Bill will give the definitive judgement, but my
comments are these:
The standoff for the FM dipole is greater than necessary. As
previously
discussed, a quarter-wave spacing is probably all you need. The long
boom, hit with a sideways wind, may cause some twisting of the brackets
-
or worse, of the whole pole which will take the TV aerial off its
correct
heading.
Agreed. The FM aerial is made by Vision (but rebadged I expect). They
have a stupid short side arm, but there's really no need to put it this
far from the mast. Decide on a direction you don't care about (Europe?)
and put the aerial on the side of the mast away from that direction,
about a quarter wavelength away. By the way, those aerials have better
bandwidth than a simple dipole. They are significantly better at the
ends of the FM band.

the overall height in comparison with the bracket spacing, looks just
a
*little* long for an exposed coastal position. But at least you are not
on
a hilltop.
Agreed. Is the mast a scaffolding tube? I hope so. If so it should be
OK.

I note you have used nylon cable ties to fix the coax to the pole,
and
trust that you have not fallen into the trap of over-tightening them
which
causes crushing of the coax.
Agreed. Also, the masthead amp will be out of reach if it ever goes
wrong. They should always be fitted within reach.

Having said all this the job is a damn sight better than most DIY
aerials I get to see!

Bill

My one's nice :-)

I'll post a pic when I get hold of a decent camera.

Marky P.

"Arthur" wrote in message
news
On Thu, 13 Jan 2005 11:50:54 -0000, Arthur wrote:

snip
Also I'm not sure why you have put a 'dog leg' on the dipole support.
Couldn't you have fitted the dipole dirctly onto to stand-off from the
main pole?


Arthur

As I think Bill indicated, things are not that simple.

The dipole is integral with a short arm (the 'dog leg') which comes as
standard with a wall bracket.
So as using a standard pole and clamp involves right angle joins, this
forces me to have a dog leg.

If I understand 'wavelength' correctly then a full wave is about 3m, 1/2
wave is about 750cms, 1/4 wave is about 375cms.

The arm built onto the dipole gives a maximum spacing from the mast of
200cms which is nearer 1/8 wave.

I was previously advised (by someone) that half wave was a good distance to
be from the mast.
That is roughly the current spacing (1.5m).
I admit it looks ungainly and like a very large lever.
I will look at adjusting it.
However they may come and take the scaffolding down tomorrow :-)

Cheers
Dave R

"Arthur" wrote in message
news
On Thu, 13 Jan 2005 10:47:47 -0000, David W.E. Roberts
wrote:
snip
- The standoff for the FM dipole is greater than necessary. As previously
discussed, a quarter-wave spacing is probably all you need. The long
boom, hit with a sideways wind, may cause some twisting of the brackets -
or worse, of the whole pole which will take the TV aerial off its correct
heading.

** See other response **

- the overall height in comparison with the bracket spacing, looks just a
*little* long for an exposed coastal position. But at least you are not on
a hilltop.

** However they are bigger than the average bracket :-)
A bit of judicious swinging on the pole didn't seem to shift them in the
slightest.
Biggest downside of the setup is mast flex .
At least it survived the recent blow better than the old mast :-( **

- I note you have used nylon cable ties to fix the coax to the pole, and
trust that you have not fallen into the trap of over-tightening them which
causes crushing of the coax.

Arthur

I experimented and the tie leaves a little notch under the locking point
which just accomodates the cable nicely.

On my rooftop survey I noted that other aerials seemed to have tape around
them (I meant to ask the NG about this but forgot) but I just happened to
have this large bag of cable ties, so..... I also wondered how long tape
lasts in the sun and wind, and if a special tape is used.

The cynic in me guessed that a reel of tape is cheaper than a bag of cable
ties.

Cheers
Dave R

On Thu, 13 Jan 2005 21:53:16 -0000, David W.E. Roberts
wrote:


"Arthur" wrote in message
news
On Thu, 13 Jan 2005 10:47:47 -0000, David W.E. Roberts

wrote:
snip
- The standoff for the FM dipole is greater than necessary. As
previously
discussed, a quarter-wave spacing is probably all you need. The long
boom, hit with a sideways wind, may cause some twisting of the brackets
-
or worse, of the whole pole which will take the TV aerial off its
correct
heading.

** See other response **

- the overall height in comparison with the bracket spacing, looks just
a
*little* long for an exposed coastal position. But at least you are not
on
a hilltop.

** However they are bigger than the average bracket :-)
A bit of judicious swinging on the pole didn't seem to shift them in the
slightest.
Biggest downside of the setup is mast flex .
At least it survived the recent blow better than the old mast :-( **

- I note you have used nylon cable ties to fix the coax to the pole, and
trust that you have not fallen into the trap of over-tightening them
which
causes crushing of the coax.

Arthur

I experimented and the tie leaves a little notch under the locking point
which just accomodates the cable nicely.

On my rooftop survey I noted that other aerials seemed to have tape
around
them (I meant to ask the NG about this but forgot) but I just happened to
have this large bag of cable ties, so..... I also wondered how long tape
lasts in the sun and wind, and if a special tape is used.

The cynic in me guessed that a reel of tape is cheaper than a bag of
cable
ties.


I personally have only used cable ties once on airspaced coax, and after
that experience went back to duct tape which seems to last forever if
applied carefully. I note in Bill's recently posted picture about Emley
that he uses tape on his professional installations. No doubt he will
tell you what sort it is.

Arthur

I note in Bill's recently posted picture about Emley
that he uses tape on his professional installations. No doubt he will
tell you what sort it is.

Tikkitape. Only black is UV proof. I used to use RS Components tape but
the quality was variable. Cable ties aren't good really, but yes you
can accomodate the cable under the cusp of the ratchet thingy. Tape is
better though.

Bill