Strange reception issues on Ch55 and 56 from Rowridge

On 07/10/2018 12:26, Jeff Layman wrote:
On 07/10/18 09:58, Jeff Layman wrote:

I'll go up in the loft soon and play around a bit with the position of
the aerial.

Ten minutes in the loft and I am amazed at the difference a few inches
can make (no smut, please...). There seemed to be absolutely no logic
where to try the aerial (NB no amp used). I could go from a signal
quality of 1 or 2 and a very intermittent picture to a steady 9 with
barely 6 inches movement. I found it didn't matter where the aerial was
- I tried it high up just under a fluorescent light and 3 feet below it
resting on a cardboard box. Both gave a quality of 9 or 10, yet in
between the signal was lost almost entirely. In the end, for simplicity,
I simply lowered the aerial about 8 inches on the original mount. That
gave a quality of around 7 on Ch55 and 8 or 9 on 56. Strangely, in that
position it was pointing through breeze blocks rather than the tiles,
and from what I'd read I had expected that to give a poorer signal than
through tiles.

Standing waves

Bill

It sounds more like something is desensing the receiver on the weaker
channels to me though. Brian

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"Bill Wright" wrote in message
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On 07/10/2018 09:58, Jeff Layman wrote:
Yes, Rowridge is received across The Solent. Also, it was very wet
yesterday with a good bit of rain all day. However, this morning it is
dry and sunny. Despite that, about 10 minutes ago I was getting "No
service" on Ch55 and 56. But now there is no problem - good picture on
all Com7/8 channels. Signal strength is steady at 9, with signal quality
6 - 8. How can it vary so much over a few minutes? NB all this is without
a masthead amp connected.

I'll go up in the loft soon and play around a bit with the position of
the aerial. There is a lot of good info at
http://aerialsandtv.com/loftaerials.html#AttenuationLevelsThroughRoofs
on how changing position just a foot or two can affect reception
markedly.

There's even better info he
http://www.wrightsaerials.tv/article...sat-201007.pdf

Failing any improvement there I'll try the amp again, as an
outside aerial isn't an option.
That will reduce outage times and durations but might not eliminate them.
Masthead amps can't do magic.

Bill

On 07/10/18 23:14, Bill Wright wrote:
On 07/10/2018 09:58, Jeff Layman wrote:
Yes, Rowridge is received across The Solent. Also, it was very wet
yesterday with a good bit of rain all day. However, this morning it is
dry and sunny. Despite that, about 10 minutes ago I was getting "No
service" onÂ* Ch55 and 56. But now there is no problem - good picture on
all Com7/8 channels. Signal strength is steady at 9, with signal quality
6 - 8. How can it vary so much over a few minutes? NB all this is
without a masthead amp connected.

I'll go up in the loft soon and play around a bit with the position of
the aerial. There is a lot of good info at
http://aerialsandtv.com/loftaerials.html#AttenuationLevelsThroughRoofs
on how changing position just a foot or two can affect reception
markedly.

There's even better info he
http://www.wrightsaerials.tv/article...sat-201007.pdf

Very informative. But it seems that with the move of Com7/8 when they
were on Group A frequencies to Ch55 and 56 seems to suggest that unless
you're going to use a Group A and separate Group C/D aerial, you are
more-or-less stuck with a log-periodic. And, as I've found out, it's
those damn high frequencies which seem to cause most problems when you
are trying to find that "sweet spot" in the loft. I'm also waiting to
see what happens to reception when we get a day of heavy rain.

One thing I'd add to watch out for today is solar panels. The previous
owner of this place seemed to like experimenting, and we have a couple
of (disconnected) thermal solar panels very near to where the aerial is.
I think they have been there since the late 80s. Maybe they are
interfering a bit, but short of moving the aerial away completely, I'll
never know.

Failing any improvement there I'll try the amp again, as an
outside aerial isn't an option.
That will reduce outage times and durations but might not eliminate
them. Masthead amps can't do magic.

Couldn't agree more.


Bill



--

Jeff

On 07/10/18 20:56, Ian Jackson wrote:
In message , Jeff Layman

Lofts are often full of reflections. These create loads of frequency
dependent peaks and nulls in the RF field. Moving an aerial only
slightly can produce a great change of signal strength from channel to
channel - and this can be particularly marked if is high gain (and hence
highly directional). A low-gain aerial is often less-critical about
where you place it.

About a week on and until today the reception was excellent. But with
the heavy rain this morning Ch55 was way down on signal quality again (0
- 3) with pixelation and sometimes a blank screen. But Ch56 was still
coming through fine (quality 7).

I still find it hard to understand why there is so much difference
between adjacent channels on 746MHz and 754MHz, but there obviously is.

--

Jeff

Jeff Layman wrote:

I still find it hard to understand why there is so much difference
between adjacent channels on 746MHz and 754MHz

Different radiation patterns to accommodate continental transmitters?

On 14/10/18 12:05, Andy Burns wrote:
Jeff Layman wrote:

I still find it hard to understand why there is so much difference
between adjacent channels on 746MHz and 754MHz

Different radiation patterns to accommodate continental transmitters?

Dunno. How would you find out? I've been searching the internet for
Rowridge radiation patterns but haven't come up with anything useful.
Maybe Mark C knows something about the Com 7/8 antennas "halfway up the
pole" at Rowridge.

--

Jeff

Jeff Layman wrote:

Andy Burns wrote:

Different radiation patterns to accommodate continental transmitters?

Dunno.Â* How would you find out?

http://s1211.photobucket.com/user/MikeDimmickTx/library/Radiation%20Patterns/Meridian/Rowridge%20group?sort=3&page=1

Not sure if they're Carver-approved though (the ukfree.tv ones probably
aren't)

Andy Burns wrote:

http://s1211.photobucket.com/user/MikeDimmickTx/library/Radiation%20Patterns/Meridian/Rowridge%20group?sort=3&page=1

Oops they're DAB, not DTT

On 14/10/18 13:47, Andy Burns wrote:
Andy Burns wrote:

http://s1211.photobucket.com/user/MikeDimmickTx/library/Radiation%20Patterns/Meridian/Rowridge%20group?sort=3&page=1

Oops they're DAB, not DTT

Never mind. Thanks for trying.

I searched on the tx.mb21.co.uk for anything to do with Rowridge in the
last year. Google found some hits, but as far as I can see they didn't
have anything to do with Rowridge.

--

Jeff

Jeff Layman wrote:

Andy Burns wrote:

http://s1211.photobucket.com/user/MikeDimmickTx/library/Radiation%20Patterns/Meridian/Rowridge%20group?sort=3&page=1
Oops they're DAB, not DTT

Never mind. Thanks for trying.

Actually they seem to be a mish-mash of DTT, DAB and FM, but photobucket
isn't an ideal indexing system ...