Technical report on rabbits ears

[Eric]

Does anybody know of a technical report of the "indoor aerial" I was told a
few years ago the there is no resemblance between the rabbits ears and
aerial theory, just I have a few people who want to argue the point, and
hoping there might be a URL around that might show I'm right or partly
right.


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.759 / Virus Database: 508 - Release Date: 09-Sep-04

 

[Phil Allison]

"Eric"

Does anybody know of a technical report of the "indoor aerial" I was told
a
few years ago the there is no resemblance between the rabbits ears and
aerial theory, just I have a few people who want to argue the point, and
hoping there might be a URL around that might show I'm right or partly
right.

** Your friends need to eat more carrots.

The "rabbits ear" is simply an adjustable length, rotatable dipole with a V
shape. The length of the two whips is set to suit the channel - longest
for ch 2, medium for FM or ch 7 and shortest for chs 9 and 10. The V shape
broadens the resonant bandwidth ( TV channels are 7 MHz wide ) since a
simple dipole is naturally quite narrow. A dipole has a fig 8 shaped pick
up pattern so the whole assembly rotates to get the best signal strength -
OR to null out a bad ghost or room reflection.

All standard antenna theory.






............ Phil

 

[Allan]

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2qdpomFu5rh2U1@uni-berlin.de...

"Eric"

Does anybody know of a technical report of the "indoor aerial" I was
told
a
few years ago the there is no resemblance between the rabbits ears and
aerial theory, just I have a few people who want to argue the point, and
hoping there might be a URL around that might show I'm right or partly
right.



** Your friends need to eat more carrots.

The "rabbits ear" is simply an adjustable length, rotatable dipole with a
V
shape. The length of the two whips is set to suit the channel - longest
for ch 2, medium for FM or ch 7 and shortest for chs 9 and 10. The V
shape
broadens the resonant bandwidth ( TV channels are 7 MHz wide ) since a
simple dipole is naturally quite narrow. A dipole has a fig 8 shaped pick
up pattern so the whole assembly rotates to get the best signal
trength -
OR to null out a bad ghost or room reflection.

All standard antenna theory.






........... Phil

That's amazing !!
Thanks Phil As simple as it now seems, I never thought of changing the
length of the whips to improve the reception..
Cheers,
Allan

 

[Eric]

I heard a engineering school did tests and came up with the conclusion it
looks like a aerial but that was as far as it got.





"Allan" <allanaws@hotmail.com> wrote in message
news:4143edf1$0$83105$c30e37c6@lon-reader.news.telstra.net...

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2qdpomFu5rh2U1@uni-berlin.de...

"Eric"

Does anybody know of a technical report of the "indoor aerial" I was
told
a
few years ago the there is no resemblance between the rabbits ears and
aerial theory, just I have a few people who want to argue the point, and
hoping there might be a URL around that might show I'm right or partly
right.



** Your friends need to eat more carrots.

The "rabbits ear" is simply an adjustable length, rotatable dipole with a
V
shape. The length of the two whips is set to suit the channel - longest
for ch 2, medium for FM or ch 7 and shortest for chs 9 and 10. The V
shape
broadens the resonant bandwidth ( TV channels are 7 MHz wide ) since a
simple dipole is naturally quite narrow. A dipole has a fig 8 shaped pick
up pattern so the whole assembly rotates to get the best signal
trength -
OR to null out a bad ghost or room reflection.

All standard antenna theory.






........... Phil

That's amazing !!
Thanks Phil As simple as it now seems, I never thought of changing the
length of the whips to improve the reception..
Cheers,
Allan





---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.760 / Virus Database: 509 - Release Date: 10-Sep-04

 

[Phil Allison]

"Eric"

I heard a engineering school did tests and came up with the conclusion it
looks like a aerial but that was as far as it got.

** Pure, urban TV tech, myth.

Do you kneo how the old coil type TV antennas work ?



.......... Phil

 

[Peter Parker]

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2qijq1Fvie65U1@uni-

** Pure, urban TV tech, myth.

Do you kneo how the old coil type TV antennas work ?

Please enlighten us!

At one time I though that maybe the spring was to stop people poking their
eyes out?!
Or was its only function just to hold the main element in (via plastic
stoppers)?

But they wouldn't have thought of that in the 50s or 60s would they?

Years ago I tried one and pulled off the coil.

It made no difference (at least on the local ABC relay on ch 10).

The middle bit is obviously near enough to a half-wave dipole for chs 6-11.

But strangely these things were fed with 300 ohm feeder even though the
characteristic
impedence of a dipole is nearer to 75 ohms. And who knows what it would
have been with the element just 1/10 wavelengh above the TV cabinet?

I did speculate that with some capacitance coupling on the ends the thing
could maybe form some sort of folded dipole thingo for ch 2, but it doesn't
sound right as it would still be too short. Or maybe it somehow reduces the
dipole's Q, giving equally bad performance across most channels? I cannot
see how it would aid impedence matching at the feedpoint.

I've never seen these antennas pictured in American or UK books. So are
they as Aussie as the Hills Hoist? And yes, I'd like to know how they work.

Peter

 

[Phil Allison]

Peter Parker"

"Phil Allison"

** Pure, urban TV tech, myth.

Do you know how the old coil type TV antennas work ?

Please enlighten us!

** The coil - which is electrically isolated - damps the resonance of
the dipole.

This broadens the gain curve so boosting at the high end of the VHF range.

The middle bit is obviously near enough to a half-wave dipole for chs
6-11.

But strangely these things were fed with 300 ohm feeder even though the
characteristic impedence of a dipole is nearer to 75 ohms.

** They were sold when all TVs had ribbon cable inputs - ie the B&W days.

I fitted one with co-ax in the early CTV days and it worked much
better.

I've never seen these antennas pictured in American or UK books.

** Sold round the world AFAIK.

So are they as Aussie as the Hills Hoist?

** Doubt it.



............. Phil