On Mon, 10 Jan 2005 17:13:19 -0000, David W.E. Roberts
wrote:


Looks like I need to extend the pole :-(

Full length (with bracket in the middle) is 1530cms.
Presumably this is half wave (wavelength of 3m?).

Yes - 100 MHz is a wavelength of 3 metres, so a half-wave dipole is 1.5m
long. And a quarter-wave spacing from the pole would be 0.75m. Don't be
too fussed about the spacing - dipoles are far less critical in dimensions
than multi-elements eg yagis. If you reduced it to 0.5m you will not get
an ideal pattern, but you can afford to lose a bit of signal and will not
notice it except on distant stations.

[Aarrgh again - if the radio is Frequency Modulation then what is the
wavelength of the carrier which is having its frequency modulated?]
This would imply putting the dipole about 750cms away from the mast.
Which means I need about 500mm of extension.

100 MHz is the carrier frequency. The frequeny deviation is negligible
compared to the carrier frequency so all of the signal is within the
bandwidth of the dipole.

With the 'trombone' shape, should the twin diploles be in line with the
signal source, or at right angles?
i.e. looking from the transmitter, should you see one dipole (with the
other hidden behind it) or see both dipoles as you would with a TV
aerial?

Absolutely not important. Fit it whichever way is easiest. If there is
no balun then check that the element connected to the coax inner is at the
top. Also run and fix the coax along the horizontal support boom to the
mast - don't cut the corner.

-Arthur

"David W.E. Roberts" wrote in message
...
I know it is not for a Digital TV,but...

...is there a better FM aerial than one of the 'halo' ones that at least
50%
of people seem to have?

I have also seen ones that look like really old (1950s) TV aerials which I
presume are for FM.

Progress report:

new dipole is installed - standing off from mast by about 1.5m.

The signal is slightly better than the 'halo' in its current orientation
(i.e. 45 degrees).

Four solid bars on the NAD receiver instead of 3-4 from the old aerial.

Thanks to all for help/advice.

Pictures will be posted for constructive comment once the scaffolding is
down.

Cheers
Dave R

"David W.E. Roberts" wrote in message
...
snip
Progress report:

new dipole is installed - standing off from mast by about 1.5m.

The signal is slightly better than the 'halo' in its current orientation
(i.e. 45 degrees).

Four solid bars on the NAD receiver instead of 3-4 from the old aerial.

Having one of those "Don't know why I bother" moments.

Having neglected to label up the co-ax terminals for the FM aerial feeds in
the loft I decided to do the usual trick of unplugging them one by one from
the amplifier in the loft and waiting for the signal to disappear at the
radio.

This proved more difficult than I thought as the signal didn't seem to go
away when the co-ax was unplugged from the amp.

In the bedroom I was getting 3 bars on the co-ax alone and 4 bars when the
aerial was connected through the amp.
I also got 4 bars when I used a femalefemale connector to bypass the amp
and connect the bedroom system directly to the roof aerial.

In the lounge, I swapped the leads around (old TV lead goes direct outside
to aerial, co-ax to loft does FM).
I get no signal from the fly lead, but if I plug into the old TV aerial then
I get a reasonable FM signal.

So:

do I just have very dodgy co-ax which acts as an acceptable FM aerial?

If not, what is going on?

Next step is a wire coathanger in the back of the tuner - and see it this
out-performs the roof installed aerial.

Hardly seems worth all the hassle of installing an aerial for a minor signal
boost.
Next thing to do is see if I can get a clean feed using all PF100 to the NAD
in the bedroom to see if that improves the signal at all.

Ho hum.
Dave R

On Wed, 12 Jan 2005 17:56:59 +0000, David W.E. Roberts wrote:


"David W.E. Roberts" wrote in message
...
snip
Progress report:

new dipole is installed - standing off from mast by about 1.5m.

The signal is slightly better than the 'halo' in its current orientation
(i.e. 45 degrees).

Four solid bars on the NAD receiver instead of 3-4 from the old aerial.

Having one of those "Don't know why I bother" moments.
snip

In the bedroom I was getting 3 bars on the co-ax alone and 4 bars when the
aerial was connected through the amp.
I also got 4 bars when I used a femalefemale connector to bypass the amp
and connect the bedroom system directly to the roof aerial.
snip
Next thing to do is see if I can get a clean feed using all PF100 to the NAD
in the bedroom to see if that improves the signal at all.

Ho hum indeed.
Latest results a

Co-ax in the wall (no amp or aerial) 2 bars
Aerial direct to tuner (new co-ax) 3 bars
Aerial through amp.(old + new co-ax) 4 bars

All three setups gave what sounded like acceptable stereo reception.

Now puzzled as to why my previous test gave a better result using [new
co-ax plus the old co-ax in the wall] than new co-ax all the way.
Both setups used the same aerial feed, the same femalefemale coupler.

Perhaps the signal strength has gone down as night falls.

Whatever, signal must be getting into the old co-ax so something isn't
right.

Dave R

On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts
wrote:


"David W.E. Roberts" wrote in message
...
I know it is not for a Digital TV,but...

...is there a better FM aerial than one of the 'halo' ones that at least
50%
of people seem to have?

I have also seen ones that look like really old (1950s) TV aerials
which I
presume are for FM.

Progress report:

new dipole is installed - standing off from mast by about 1.5m.

The signal is slightly better than the 'halo' in its current orientation
(i.e. 45 degrees).

Four solid bars on the NAD receiver instead of 3-4 from the old aerial.

Thanks to all for help/advice.

Pictures will be posted for constructive comment once the scaffolding is
down.

Cheers
Dave R


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

Arthur

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


"David W.E. Roberts" wrote in message
...
I know it is not for a Digital TV,but...

...is there a better FM aerial than one of the 'halo' ones that at least
50%


new dipole is installed - standing off from mast by about 1.5m.


I didn't bother extending the arm on my FM dipole, and connected it as
it was (about 8 inches from mast roughly). Works exceptionally well,
though I have noticed some attenuation from the east (where the mast
masks the aerial). Whether extending the distance from aerial to mast
would've eliminated the masking I don't know, but it's not important.

Marky P.

On Wed, 12 Jan 2005 18:23:32 +0000, David WE Roberts
wrote:

On Wed, 12 Jan 2005 17:56:59 +0000, David W.E. Roberts wrote:


"David W.E. Roberts" wrote in message
...
snip
Progress report:

new dipole is installed - standing off from mast by about 1.5m.

The signal is slightly better than the 'halo' in its current orientation
(i.e. 45 degrees).

Four solid bars on the NAD receiver instead of 3-4 from the old aerial.

Having one of those "Don't know why I bother" moments.
snip

In the bedroom I was getting 3 bars on the co-ax alone and 4 bars when the
aerial was connected through the amp.
I also got 4 bars when I used a femalefemale connector to bypass the amp
and connect the bedroom system directly to the roof aerial.
snip
Next thing to do is see if I can get a clean feed using all PF100 to the NAD
in the bedroom to see if that improves the signal at all.

Ho hum indeed.
Latest results a

Co-ax in the wall (no amp or aerial) 2 bars
Aerial direct to tuner (new co-ax) 3 bars
Aerial through amp.(old + new co-ax) 4 bars

All three setups gave what sounded like acceptable stereo reception.

Now puzzled as to why my previous test gave a better result using [new
co-ax plus the old co-ax in the wall] than new co-ax all the way.
Both setups used the same aerial feed, the same femalefemale coupler.

Perhaps the signal strength has gone down as night falls.

Whatever, signal must be getting into the old co-ax so something isn't
right.

Dave R

Now you've really confused me! OK, let's try to get this straight.
Co-ax in the wall (no amp or aerial) 2 bars. Right, that must be the
FM signal just dropping itself into the end of the cable (or right
through the cable it's cheap or knackered).

Aerial direct to tuner (new co-ax) 3 bars. OK, this would be the
most accurate reading. If your cable is CT100 or equivalent & around
10-12m in length, there will be very little loss at FM frequencies.

Aerial through amp (old & new co-ax) 4 bars. Now, I believe the new
co-ax is from aerial to amp, then old co-ax from amp to tuner. In
this case, the amp is improving the signal through the old co-ax,
hence there will be less loss. Beware of tuner signal strength meters
though. The stronger the amp, the more bars will light up on the
tuner. This isn't necessarily an indication of a better signal from
the aerial, just the amp adding it's own boosted signal, therefore
giving an inaccurate reading. In my naive day, I bought a 40dB amp to
put in line with my FM aerial to improve the signal. The meter was
whacked right up to full on all receivable stations! But when the
excitement died down & I actually listened to the radio, the quality
of reception was just the same. Hissy stations were still hissy
regardless of what the meter said, all because the amp was producing a
false reading.

Sorry for going on a bit. Hope I didn't lose you in the translation
somewhere.

Marky P.

Four solid bars on the NAD receiver instead of 3-4 from the old
aerial.


That's probably 10dB!

Bill

"Arthur" wrote in message
...
On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts
wrote:
snip
Pictures will be posted for constructive comment once the scaffolding is
down.

Cheers
Dave R


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

Arthur

Will do.
For the moment, think of those postcards of 'Wales at Night'.
Tomorrow morning I will expose you to the full horror.

Cheers
Dave R

"Marky P" wrote in message
...
On Wed, 12 Jan 2005 18:23:32 +0000, David WE Roberts
wrote:
snip
Now you've really confused me!
snip

For a confused person you seem remarkably lucid ;-))

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

It may not be a good, clean signal but the FM receivers seem to work fine on
it.

As Bill posts, the one bar on the tuner may be a major gain in signal
strength and quality, however....

I guess if the co-ax can pick up FM radio then it is noisy.

I think I have found a use for the rest of my new cable :-)

Cheers

Dave R