Apologies if this is a stupid question.

I'm re-jigging the TV aerial which is in our loft. I put it up myself
some years ago.

At that time, I very neatly stripped away the outside braided copper
sleeving (at the aerial end), twisted it, and connected it to one of the
two terminals on the aerial; I connected the aerial cable itself to the
other terminal. The aerial has always worked fine.

Looking at this arrangement this weekend, I wondered why I'd done it: in
effect I am connecting the two together, since the two terminals are at
opposite ends of the same cross-piece on the aerial (i.e. the rear-most
cross-piece).

But any fule kno that you shouldn't allow the braid to come into contact
with the aerial co I don't see how it can work!

So what are you actually *supposed* to do with the earthing braid at
the aerial end of things? (My old Reader's Digest DIY book doesn't
mention the 'top' end of the aerial installation.)

Cheers
John

On Mon, 13 Jun 2005 09:57:16 +0100, John wrote:


Looking at this arrangement this weekend, I wondered why I'd done it: in
effect I am connecting the two together, since the two terminals are at
opposite ends of the same cross-piece on the aerial (i.e. the rear-most
cross-piece).

For DC you are infact shorting out the end of the feeder but at the
radio frequencies you are talking about it's not a short cct.

All the best ..

T i m

In article ,
John wrote:
Looking at this arrangement this weekend, I wondered why I'd done it: in
effect I am connecting the two together, since the two terminals are at
opposite ends of the same cross-piece on the aerial (i.e. the rear-most
cross-piece).

But any fule kno that you shouldn't allow the braid to come into contact
with the aerial co I don't see how it can work!

RF doesn't behave like DC. You've got a folded dipole there which will
have a supposed impedance of 75 ohms at the frequency it's working at.

However, better quality aerials will have a 'balun' transformer that gives
a more exact match.

So what are you actually *supposed* to do with the earthing braid at
the aerial end of things? (My old Reader's Digest DIY book doesn't
mention the 'top' end of the aerial installation.)

You've done it the correct way.

--
*42.7% of statistics are made up. Sorry, that should read 47.2% *

Dave Plowman London SW
To e-mail, change noise into sound.

In article , John
wrote:

But any fule kno that you shouldn't allow the braid to come into contact
with the aerial co I don't see how it can work!

Because resistance =! Impedance, at the resonant frequency of the aerial.

So what are you actually *supposed* to do with the earthing braid at
the aerial end of things? (My old Reader's Digest DIY book doesn't
mention the 'top' end of the aerial installation.)

You are supposed to clamp it under the saddle provided. The type of aerial
you describe is just a "contractor" type with no balun. I heartily
disapprove of those, due to the mismatch. You can get away with a great deal
when you have analogue TV, but you will find that once it is shut down, your
whole installation will need doing properly.

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

Andy Luckman (AJL Electronics) wrote:
In article , John
wrote:

But any fule kno that you shouldn't allow the braid to come into contact
with the aerial co I don't see how it can work!

Because resistance =! Impedance, at the resonant frequency of the aerial.

So what are you actually *supposed* to do with the earthing braid at
the aerial end of things? (My old Reader's Digest DIY book doesn't
mention the 'top' end of the aerial installation.)

You are supposed to clamp it under the saddle provided. The type of aerial
you describe is just a "contractor" type with no balun. I heartily
disapprove of those, due to the mismatch. You can get away with a great deal
when you have analogue TV, but you will find that once it is shut down, your
whole installation will need doing properly.

Not neccessarily. Our old aerial and installation gives us DTV just
fine.

It does of course depend upon reception quality and other factors in
your area which are impossible to gauge from the OPs question.

Andrew

Andy Luckman (AJL Electronics) wrote:
In article , John
wrote:

But any fule kno that you shouldn't allow the braid to come into contact
with the aerial co I don't see how it can work!

Because resistance =! Impedance, at the resonant frequency of the aerial.

So what are you actually *supposed* to do with the earthing braid at
the aerial end of things? (My old Reader's Digest DIY book doesn't
mention the 'top' end of the aerial installation.)

You are supposed to clamp it under the saddle provided. The type of aerial
you describe is just a "contractor" type with no balun. I heartily
disapprove of those, due to the mismatch. You can get away with a great deal
when you have analogue TV, but you will find that once it is shut down, your
whole installation will need doing properly.

what would you recommend instead? Im about to put a new aerial system
in, and am in a poor reception area.


NT

In article .com,
wrote:

Not neccessarily. Our old aerial and installation gives us DTV just
fine.

Depends on your definition of "fine" I can guarantee that if an analyzer
was put on your aerial, I would be able to point to a deficiency. Most
likely multiplex flatness.

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

In article .com,
wrote:
You are supposed to clamp it under the saddle provided. The type of
aerial you describe is just a "contractor" type with no balun. I
heartily disapprove of those, due to the mismatch. You can get away
with a great deal when you have analogue TV, but you will find that
once it is shut down, your whole installation will need doing properly.

what would you recommend instead? Im about to put a new aerial system
in, and am in a poor reception area.

A decent make - Televes - for example. But expect to pay three times that
of a shed type. TLC sell them.

--
*Bills travel through the mail at twice the speed of cheques *

Dave Plowman London SW
To e-mail, change noise into sound.

In article .com,
wrote:


what would you recommend instead? Im about to put a new aerial system
in, and am in a poor reception area.

It does depend on many factors. Although others may disagree, I would ALWAYS
inssit that it is set up on an analyser that reads all the relevant
parameters. You can have too much signal as well as too little. You can also
have lots of signal and lots of noise. For that reason, see if you can find
a professional installer in your area and ask for the levels to be recorded.
We issue a "certificate of conformity" at the end of our jobs.

Aerials differ greatly. Avoid anything called a "contractor" aerial. See
what the range of channel frequencies are and order the aerial for that
range only. Some areas require a wideband response. There are a range of
aerials that have been benchmarked and found satisfactory. These include the
Triax Unix 52. Ideally get one so marked.

Despite the propaganda put about by the once respected "Antiference"
company, a balun IS REQUIRED. So is the correct grade of cable which should
be certified to EN50117. Many quality satellite cables are to this spec, but
it will be marked as such if it complies.

One of the drawbacks of digital, is that you can no longer say "that's a
good picture, it suits me". Unless the signal parameters are within the
correct range, you get nothing, or constant breakup, with digital.

Hope that helps?

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

On Mon, 13 Jun 2005 13:54:19 +0100, "Andy Luckman (AJL Electronics)"
wrote:

[snip]

Despite the propaganda put about by the once respected "Antiference"
company, a balun IS REQUIRED.

[more snip]

Thanks for clearing that up for me, I always thought it was odd to
have to terminate 75 ohm cable to what appears to be a nice set of 300
ohm terminals. Would one of the 'cable co special' 300 ohm to 75 ohm F
connector type tubular baluns work in this application, if you cut the
fork spades down to just the crimped part and put that in the
terminals?


--
"I think computer viruses should count as life. I think it
says something about human nature that the only form of life
we have created so far is purely destructive. We've created
life in our own image." - Stephen Hawking

Andy Luckman (AJL Electronics) wrote:
In article .com,
wrote:

Not neccessarily. Our old aerial and installation gives us DTV just
fine.

Depends on your definition of "fine"

No visible or audible problems.

I can guarantee that if an analyzer
was put on your aerial, I would be able to point to a deficiency. Most
likely multiplex flatness.

What difference would "fixing" that make to my experience of digital
TV? It's already better than analogue.

Andrew

On Mon, 13 Jun 2005 13:09:15 GMT, Chipmunk
wrote:

"I think computer viruses should count as life. I think it
says something about human nature that the only form of life
we have created so far is purely destructive. We've created
life in our own image." - Stephen Hawking

And I suppose a virus is the last thing Mr Hawking needs ..

Virus: Voice mode: Homer Simpson / On .... ;-)

All the best ..

T i m

Andy Luckman (AJL Electronics) wrote:
In article .com,
wrote:


what would you recommend instead? Im about to put a new aerial system
in, and am in a poor reception area.

It does depend on many factors. Although others may disagree, I would ALWAYS
inssit that it is set up on an analyser that reads all the relevant
parameters. You can have too much signal as well as too little. You can also
have lots of signal and lots of noise. For that reason, see if you can find
a professional installer in your area and ask for the levels to be recorded.
We issue a "certificate of conformity" at the end of our jobs.

Aerials differ greatly. Avoid anything called a "contractor" aerial. See
what the range of channel frequencies are and order the aerial for that
range only. Some areas require a wideband response. There are a range of
aerials that have been benchmarked and found satisfactory. These include the
Triax Unix 52. Ideally get one so marked.

Despite the propaganda put about by the once respected "Antiference"
company, a balun IS REQUIRED. So is the correct grade of cable which should
be certified to EN50117. Many quality satellite cables are to this spec, but
it will be marked as such if it complies.

One of the drawbacks of digital, is that you can no longer say "that's a
good picture, it suits me". Unless the signal parameters are within the
correct range, you get nothing, or constant breakup, with digital.

Hope that helps?


thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

You wouldnt think tronics is my home ground, but there ya go.


NT

In article .com,
wrote:
thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

They all should have for best results. It's in the cable connection box.
And it's a pretty simple device - only a few turns of wire for each
winding. Can't cost more than a few pennies.

IIRC, the actual impedance of a folded dipole is 300 ohms, and many
countries use a 300 ohm balanced feeder system. But this has to be spaced
off the wall to work properly, so costs more to install.

But as with all aerials, what actually works ok in individual
circumstances is somewhat of a black art.

I've got a DAB and Freeview tuner (used only for radio) both connected to
a horizontal FM aerial and both work ok - or as well as either do at best.
;-) Mind, I can see Crystal Palace mast from this window.

You wouldnt think tronics is my home ground, but there ya go.

RF is a minefield. ;-)

--
*I just got lost in thought. It was unfamiliar territory.

Dave Plowman London SW
To e-mail, change noise into sound.

In message , John
writes
Apologies if this is a stupid question.

I'm re-jigging the TV aerial which is in our loft. I put it up myself
some years ago.

At that time, I very neatly stripped away the outside braided copper
sleeving (at the aerial end), twisted it, and connected it to one of the
two terminals on the aerial; I connected the aerial cable itself to the
other terminal. The aerial has always worked fine.

Looking at this arrangement this weekend, I wondered why I'd done it: in
effect I am connecting the two together, since the two terminals are at
opposite ends of the same cross-piece on the aerial (i.e. the rear-most
cross-piece).

Ah, but you're thinking DC and the aerial is picking up signals of tens
of megaherts (65MHz). At these frequencies, that DC short circuit looks
like 75ohms (I could get shot down in flames here)

--
geoff

In message .com,
writes


Andy Luckman (AJL Electronics) wrote:
In article , John
wrote:

But any fule kno that you shouldn't allow the braid to come into contact
with the aerial co I don't see how it can work!

Because resistance =! Impedance, at the resonant frequency of the aerial.

So what are you actually *supposed* to do with the earthing braid at
the aerial end of things? (My old Reader's Digest DIY book doesn't
mention the 'top' end of the aerial installation.)

You are supposed to clamp it under the saddle provided. The type of aerial
you describe is just a "contractor" type with no balun. I heartily
disapprove of those, due to the mismatch. You can get away with a great deal
when you have analogue TV, but you will find that once it is shut down, your
whole installation will need doing properly.

Not neccessarily. Our old aerial and installation gives us DTV just
fine.

In fact, I get better digital reception with my 20+ year old aerial than
I do with my supposedly better 2 year old one

--
geoff

In message .com,
writes

thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

You wouldnt think tronics is my home ground, but there ya go.

Me too, but I remember at MSDS the aerials department was known as the
home of black magic. You didn't wander in there without a crucifix and
some garlic

--
geoff

In article , raden
writes
In message .com,
writes

thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

You wouldnt think tronics is my home ground, but there ya go.

Me too, but I remember at MSDS the aerials department was known as the
home of black magic. You didn't wander in there without a crucifix and
some garlic


Contrary to popular belief aerials are quite understandable you just
need to know the right things, and that knowledge isn't made known to
all)
--
Tony Sayer

In message , tony sayer
writes
In article , raden
writes
In message .com,
writes

thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

You wouldnt think tronics is my home ground, but there ya go.

Me too, but I remember at MSDS the aerials department was known as the
home of black magic. You didn't wander in there without a crucifix and
some garlic


Contrary to popular belief aerials are quite understandable you just
need to know the right things, and that knowledge isn't made known to
all)

One coat hanger fits all ?

--
geoff

In message , "Andy Luckman
(AJL Electronics)" writes
Depends on your definition of "fine" I can guarantee that if an analyzer
was put on your aerial, I would be able to point to a deficiency. Most
likely multiplex flatness.
If you put an analyzer such as a 141T on the aerial it would definitely
show flatness, unless it is a very robust aerial.



--
Bill

In article ,
raden wrote:
Ah, but you're thinking DC and the aerial is picking up signals of tens
of megaherts (65MHz). At these frequencies, that DC short circuit looks
like 75ohms (I could get shot down in flames here)

Well you will. Because 65 MHz isn't anything near a broadcast TV frequency
these days. ;-)

--
*I never drink anything stronger than gin before breakfast *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article .com,
wrote:
thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

They all should have for best results. It's in the cable connection box.
And it's a pretty simple device - only a few turns of wire for each
winding. Can't cost more than a few pennies.

IIRC, the actual impedance of a folded dipole is 300 ohms, and many
countries use a 300 ohm balanced feeder system. But this has to be spaced
off the wall to work properly, so costs more to install.

The cable is ultracheap, being little more than speaker wire, but here
labour costs rule.

NT

In article , Chipmunk
wrote:

Thanks for clearing that up for me, I always thought it was odd to
have to terminate 75 ohm cable to what appears to be a nice set of 300
ohm terminals.

It's only 300 ohm in free space. When you start adding reflectors and
directors, the impedance drops. The point Antiference were trying to make is
that the feedpoint is 75r. Conveniently missing the fact that there is a
balance to unbalance mismatch remaining of course.

Would one of the 'cable co special' 300 ohm to 75 ohm F
connector type tubular baluns work in this application,

It depends. I personally would just get a "proper aerial".

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

In article .com,
wrote:

No visible or audible problems.

Compared to what?

What difference would "fixing" that make to my experience of digital
TV? It's already better than analogue.

Depends on the answer above, but reliability of service mostly.

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

In article .com,
wrote:

thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

The balun is in the feed box and often is a stripline PCB.

BTW. I can supply approved kit as well as the free advice. :-)

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

raden wrote:

Ah, but you're thinking DC and the aerial is picking up signals of tens
of megaherts (65MHz). At these frequencies, that DC short circuit looks
like 75ohms (I could get shot down in flames here)

More like 650 MHz for TV in the UK [1], but you've got the right idea.

[1] 471-848 MHz UK TV band


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

Andy Luckman (AJL Electronics) wrote:
In article .com,
wrote:

thanks, will start by checing out TLC site for aerials. Do teh bteer
aerials have the balun in them, or is it fitted somewhere else?

The balun is in the feed box and often is a stripline PCB.

BTW. I can supply approved kit as well as the free advice. :-)


will be checking your site out too then. You dont sell round tuits in
bulk do you?

NT

In article .com,
wrote:

will be checking your site out too then.

Site's a bit long in the tooth now and needs some serious time spent
updating it. Email me direct if you like, once you know what you want. I
will do you a better price than our normal retail of course.

You dont sell round tuits in
bulk do you?

Only square ones. :-)

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

Andy Luckman (AJL Electronics) wrote:
In article .com,
wrote:

No visible or audible problems.

Compared to what?

No visible or audible problems. It's an absolute measure, not relative
to anything else.


What difference would "fixing" that make to my experience of digital
TV? It's already better than analogue.

Depends on the answer above, but reliability of service mostly.

No difference then.

Andrew

In message , "Dave Plowman (News)"
writes
In article ,
raden wrote:
Ah, but you're thinking DC and the aerial is picking up signals of tens
of megaherts (65MHz). At these frequencies, that DC short circuit looks
like 75ohms (I could get shot down in flames here)

Well you will. Because 65 MHz isn't anything near a broadcast TV frequency
these days. ;-)

Did I leave a "0" out there ?

.... cough

A Zero's nothing between friends

bugger, bugger, bugger

I know what I meant, even if I didn't type it

--
geoff

In article ,
raden wrote:
Well you will. Because 65 MHz isn't anything near a broadcast TV
frequency these days. ;-)

Did I leave a "0" out there ?

... cough

A Zero's nothing between friends

bugger, bugger, bugger

I know what I meant, even if I didn't type it

I know the feeling well. ;-)

--
*Cover me. I'm changing lanes.

Dave Plowman London SW
To e-mail, change noise into sound.

Mark Carver wrote:

[1] 471-848 MHz UK TV band

470 - 854 MHz actually.

--
Andy

Andy Wade wrote:
Mark Carver wrote:

[1] 471-848 MHz UK TV band


470 - 854 MHz actually.

Ah yes, every bit of sideband counts :-)

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