At the moment my elderly mother has a 10-element Yagi style aerial
mounted in her loft. Digital reception is usually quite good, although
the little slider bar on the reception-quality indicator in one of the
TV menu options only gets half way, and in bad weather the picture
tends to go off a bit, most obviously with rapid movements. I assume a
stronger signal would help.

I have several options. Either get an external aerial fitted to the
chimney, which would have to be done professionally, or install an
amplifier close to the aerial in the loft, which I could probably do.
Which is likely to give the better result, or is it impossible to say
without making measurements? A third option would be to wait until
next summer and DSO, when the power of the digital transmitter is
going to be significantly increased AIUI, and re-assess the situation,
although the question might still arise.

What are the essential differences in performance, if any, between
mast-head amplifiers and signal boosters, and which should I use in
the above circumstances?

She lives in West Cornwall, with a direct line-of-sight across St.
Ives Bay to the Redruth transmitter some 10 miles distant.

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

Over water paths are notoriously variable, so the  problems of multipath 
might be the main cause of problems. I think honestly, you would need 
someone to test a few locations for an aerial to see what is the best for 
all situations. so, I suppose it might be worth trying an amp in the short 
term, though of course they do amplify noise and add cross mod problems of 
their own.

Brian

-- 
Brian Gaff - briang1@blueyonder.co.uk
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Chris Hogg"  wrote in message 
news:fgun9498uanlg8dvccndbtmpge2vnptbkb@4ax.com...
> At the moment my elderly mother has a 10-element Yagi style aerial
> mounted in her loft. Digital reception is usually quite good, although
> the little slider bar on the reception-quality indicator in one of the
> TV menu options only gets half way, and in bad weather the picture
> tends to go off a bit, most obviously with rapid movements. I assume a
> stronger signal would help.
>
> I have several options. Either get an external aerial fitted to the
> chimney, which would have to be done professionally, or install an
> amplifier close to the aerial in the loft, which I could probably do.
> Which is likely to give the better result, or is it impossible to say
> without making measurements? A third option would be to wait until
> next summer and DSO, when the power of the digital transmitter is
> going to be significantly increased AIUI, and re-assess the situation,
> although the question might still arise.
>
> What are the essential differences in performance, if any, between
> mast-head amplifiers and signal boosters, and which should I use in
> the above circumstances?
>
> She lives in West Cornwall, with a direct line-of-sight across St.
> Ives Bay to the Redruth transmitter some 10 miles distant.
>
> -- 
>
> Chris
>
> E-mail: christopher[dot]hogg[at]virgin[dot]net

Chris Hogg wrote:
> At the moment my elderly mother has a 10-element Yagi style aerial
> mounted in her loft. Digital reception is usually quite good, although
> the little slider bar on the reception-quality indicator in one of the
> TV menu options only gets half way, and in bad weather the picture
> tends to go off a bit, most obviously with rapid movements. I assume a
> stronger signal would help.

Signal strength might be your problem, but too much rather than not enough.

Redruth's DTT muxes are adjacent to the analogue channels, if the 
analogue signal level is too high, then the adjacent digital mux can be 
corrupted. 10 miles and LOS to Redruth has the potential to produce a 
thumping great signal. What does the quality of the analogue channels 
look like, are they clean, grainy, or do they suffer patterning ?

Also, as Brian mentions, tidal fading could be another factor. Can the 
aerial 'see' any tidal water ?

Thanks for those comments. The analogue signal is indeed quite strong.
Before digital came along, the only aerial needed was an appropriately
sized dipole that I made from stiff insulated copper wire (2.5 mm ring
main stuff IIRC) attached directly to a coax plug and plugged straight
into the back of the TV, and which gave an excellent picture. Not
quite a bent coat hanger, but not far off! Even after Redruth started
transmitting digital, the analogue picture was still very good with no
problems.

I think what I'll do is try a not-too-expensive masthead amp for
putting in the loft to see what happens, and then wait until DSO
before deciding whether to 'get a man in'. 

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

Chris Hogg wrote:
> Thanks for those comments. The analogue signal is indeed quite strong.
> Before digital came along, the only aerial needed was an appropriately
> sized dipole that I made from stiff insulated copper wire (2.5 mm ring
> main stuff IIRC) attached directly to a coax plug and plugged straight
> into the back of the TV, and which gave an excellent picture. Not
> quite a bent coat hanger, but not far off! Even after Redruth started
> transmitting digital, the analogue picture was still very good with no
> problems.
> 
> I think what I'll do is try a not-too-expensive masthead amp for
> putting in the loft to see what happens, 

For reasons I explained in my post, that's the last thing you want, the 
analogue signals will totally saturate both the amp, and the receivers.

It's counter intuitive, but try attenuating the signal first.

-- 
Mark
Please replace invalid and invalid with gmx and net to reply.

On Sat, 09 Aug 2008 18:40:32 +0100, Mark Carver
<mark.carver@invalid.invalid> wrote:

>Chris Hogg wrote:
>> Thanks for those comments. The analogue signal is indeed quite strong.
>> Before digital came along, the only aerial needed was an appropriately
>> sized dipole that I made from stiff insulated copper wire (2.5 mm ring
>> main stuff IIRC) attached directly to a coax plug and plugged straight
>> into the back of the TV, and which gave an excellent picture. Not
>> quite a bent coat hanger, but not far off! Even after Redruth started
>> transmitting digital, the analogue picture was still very good with no
>> problems.
>> 
>> I think what I'll do is try a not-too-expensive masthead amp for
>> putting in the loft to see what happens, 
>
>For reasons I explained in my post, that's the last thing you want, the 
>analogue signals will totally saturate both the amp, and the receivers.
>
>It's counter intuitive, but try attenuating the signal first.


Is there a simple way of doing that, such as sticking a resistor in
somewhere the aerial downlead, or is it a matter of buying a special
attenuator?

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

In article ,
   Chris Hogg  wrote:
> On Sat, 09 Aug 2008 18:40:32 +0100, Mark Carver
> <mark.carver@invalid.invalid> wrote:

> >Chris Hogg wrote:
> >> Thanks for those comments. The analogue signal is indeed quite strong.
> >> Before digital came along, the only aerial needed was an appropriately
> >> sized dipole that I made from stiff insulated copper wire (2.5 mm ring
> >> main stuff IIRC) attached directly to a coax plug and plugged straight
> >> into the back of the TV, and which gave an excellent picture. Not
> >> quite a bent coat hanger, but not far off! Even after Redruth started
> >> transmitting digital, the analogue picture was still very good with no
> >> problems.
> >> 
> >> I think what I'll do is try a not-too-expensive masthead amp for
> >> putting in the loft to see what happens, 
> >
> >For reasons I explained in my post, that's the last thing you want, the 
> >analogue signals will totally saturate both the amp, and the receivers.
> >
> >It's counter intuitive, but try attenuating the signal first.


> Is there a simple way of doing that, such as sticking a resistor in
> somewhere the aerial downlead, or is it a matter of buying a special
> attenuator?

The proper way is to buy a properly made, screened, attenuator.  This will
keep the characteristic (75 ohm) impedance of the system, avoiding
reflections in the cable which can cause havoc with digital signals.

You used to be able to buy variable ones - don't know if they still exist.

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

charles wrote:
> In article ,
>    Chris Hogg  wrote:
>> On Sat, 09 Aug 2008 18:40:32 +0100, Mark Carver
>>
>>>
>>> It's counter intuitive, but try attenuating the signal first.
> 
> 
>> Is there a simple way of doing that, such as sticking a resistor in
>> somewhere the aerial downlead, or is it a matter of buying a special
>> attenuator?
> 
> The proper way is to buy a properly made, screened, attenuator.  This will
> keep the characteristic (75 ohm) impedance of the system, avoiding
> reflections in the cable which can cause havoc with digital signals.
> 
> You used to be able to buy variable ones - don't know if they still exist.

Maplins do one, and also fixed types:-

http://www.maplin.co.uk/Search.aspx?criteria=attenuator&source=15&SD=Y

-- 
Mark
Please replace invalid and invalid with gmx and net to reply.

On Sun, 10 Aug 2008 08:55:33 +0100, Mark Carver
<mark.carver@invalid.invalid> wrote:

>charles wrote:
>> In article ,
>>    Chris Hogg  wrote:
>>> On Sat, 09 Aug 2008 18:40:32 +0100, Mark Carver
>>>
>>>>
>>>> It's counter intuitive, but try attenuating the signal first.
>> 
>> 
>>> Is there a simple way of doing that, such as sticking a resistor in
>>> somewhere the aerial downlead, or is it a matter of buying a special
>>> attenuator?
>> 
>> The proper way is to buy a properly made, screened, attenuator.  This will
>> keep the characteristic (75 ohm) impedance of the system, avoiding
>> reflections in the cable which can cause havoc with digital signals.
>> 
>> You used to be able to buy variable ones - don't know if they still exist.
>
>Maplins do one, and also fixed types:-
>
>http://www.maplin.co.uk/Search.aspx?criteria=attenuator&source=15&SD=Y


Thanks for that. I'll give it a go!

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

"charles"  wrote in message 
news:4fcc8cc4bbcharles@charleshope.demon.co.uk...
> The proper way is to buy a properly made, screened, attenuator.  This will
> keep the characteristic (75 ohm) impedance of the system, avoiding
> reflections in the cable which can cause havoc with digital signals.
>
> You used to be able to buy variable ones - don't know if they still exist.

Yes, but the cheap ones don't seem to present a constant match, or anything 
like one. Remember the Egen ones with little holes in the side to read the 
number through? The number related to the loss but was not dBs.

In the contract rigging days we didn't use attenuators because of the cost. 
We made Faraday Loops. These were really for use as high pass filters but if 
you coupled them loosely and/or made the loops tiny they worked well as 
attenuators.

Bill