Sent DB2 back: Homemade HDTV antenna idea?
 

I sent my DB2 antenna back. Didn't perform any better
IN the house than cheap rabbit ears.

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?

So..... what if I take some coax and strip off a long
section so that the inner wire is bare...no shielding.

Then I get this "end" outside ... maybe up an outside
wall..... or along a banister on my apartment.

This likely to work well? It would be cheap anyway!

Sent DB2 back: Homemade HDTV antenna idea?
 

On Tue, 04 Mar 2008 15:28:49 -0600, wrote:

I sent my DB2 antenna back. Didn't perform any better
IN the house than cheap rabbit ears.

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?
Wrong.

So..... what if I take some coax and strip off a long
section so that the inner wire is bare...no shielding.

Then I get this "end" outside ... maybe up an outside
wall..... or along a banister on my apartment.

This likely to work well?
No.
It would be cheap anyway!
Yes. But you could save even more by simply attaching a shoelace to
the end of the coax.

Sent DB2 back: Homemade HDTV antenna idea?
 

On Tue, 04 Mar 2008 15:28:49 -0600, wrote:

I sent my DB2 antenna back. Didn't perform any better
IN the house than cheap rabbit ears.

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?

So..... what if I take some coax and strip off a long
section so that the inner wire is bare...no shielding.

Then I get this "end" outside ... maybe up an outside
wall..... or along a banister on my apartment.

This likely to work well? It would be cheap anyway!

Probably work somewhat on UHF channels, but it will work a lot better
with any kind of antenna up there, and if you want VHF channels,
you'll need more than a bare end, esp 2-5.

J.

Sent DB2 back: Homemade HDTV antenna idea?
 

wrote

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?

Wrong.

Partly right. A lesser quality antenna high and in the clear outside will
generally outperform a better one indoors at ground level. The experimenter
in me would try making a dipole antenna out of the end of the coax. Strip
off about one foot of the outer insulation, exposing the shield. Now strip
back the shield, intact, making a foot long "wire." That's one half of your
dipole. Now completely strip off the inner conductor's insulation. That's
the other half of your dipole. If the coax is held "vertically," the two
dipole wires are to be extended horizontally (I think - are UHF signals
horizontally polarized?), making a T with the coax. Hang that thing up, in
the clear, and see what happens. If the picture still stinks, connect a
decent outside TV antenna to the end of your coax!

Sent DB2 back: Homemade HDTV antenna idea?
 

Correction!

"Howard Lester" wrote

in me would try making a dipole antenna out of the end of the coax. Strip
off about one foot of the outer insulation,

OOPS! Make that six inches, not one foot.

Sent DB2 back: Homemade HDTV antenna idea?
 

I commend you for your resourcefulness, but if you're gonna build for
the outside, why don't you take an ohmmeter down to the hardware store
or scrapyard and find something more durable than unshielded coaxial?

Sent DB2 back: Homemade HDTV antenna idea?
 

wrote

I commend you for your resourcefulness, but if you're gonna build for
the outside, why don't you take an ohmmeter down to the hardware store
or scrapyard and find something more durable than unshielded coaxial?

Who are you directing this to, and what good is an ohmmeter at a scrapyard
or hardware store?

Sent DB2 back: Homemade HDTV antenna idea?
 

On Mar 4, 4:28*pm, wrote:

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?

Right now the active element of my HDTV antenna is two 6" aluminum
rods jammed into the ends of a short horizontal plastic tube. I
drilled and tapped through the inner ends of the rods for stainless
steel screws which hold the rods in and connect to the 300-75 Ohm
matching transformer. Come spring I'll redo it by mounting slightly
longer rods in opposite sides of a plastic box which will protect the
connections from the rain better.

It's actually a home-made replacement part for a Radio Shack UHF
antenna that was damaged in a storm.
Depending on whose formula I use, the end-to-end distance should be 15
to 16 inches. The original was 14.6" but it was made for older, higher
UHF channels.

Jim Wilkins

Sent DB2 back: Homemade HDTV antenna idea?
 

wrote:
I sent my DB2 antenna back. Didn't perform any better
IN the house than cheap rabbit ears.

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?

So..... what if I take some coax and strip off a long
section so that the inner wire is bare...no shielding.

Then I get this "end" outside ... maybe up an outside
wall..... or along a banister on my apartment.

This likely to work well? It would be cheap anyway!

Of course, a thinking person would have taken the DB-2 antenna an placed it
in a suitable location outside and used it as originally intended and
probably had a good signal with little effort, no experimentation, and no
return necessary. To quote the maker: "...the DB2 was originally designed
for outdoor use..."

http://www.antennasdirect.com/DB2_Indoor_antenna.html

--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com

Sent DB2 back: Homemade HDTV antenna idea?
 

Sent DB2 back: Homemade HDTV antenna idea?
 

On Wed, 5 Mar 2008 06:21:17 -0700, "Howard Lester"
wrote:

wrote

I commend you for your resourcefulness, but if you're gonna build for
the outside, why don't you take an ohmmeter down to the hardware store
or scrapyard and find something more durable than unshielded coaxial?

Who are you directing this to, and what good is an ohmmeter at a scrapyard
or hardware store?

Maybe you can trade the ohmmeter for an antenna!

(old joke - name five ways you can use a barometer to measure the
height of a building!)

J.

Sent DB2 back: Homemade HDTV antenna idea?
 

In article Jim Wilkins writes:
On Mar 4, 4:28=A0pm, wrote:

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?

Right now the active element of my HDTV antenna is two 6" aluminum
rods jammed into the ends of a short horizontal plastic tube. I
drilled and tapped through the inner ends of the rods for stainless
steel screws which hold the rods in and connect to the 300-75 Ohm
matching transformer. Come spring I'll redo it by mounting slightly
longer rods in opposite sides of a plastic box which will protect the
connections from the rain better.

It's actually a home-made replacement part for a Radio Shack UHF
antenna that was damaged in a storm.
Depending on whose formula I use, the end-to-end distance should be 15
to 16 inches. The original was 14.6" but it was made for older, higher
UHF channels.

I don't know what formulas you are using, but a good start is 468 feet/f
(in MHz). With that, you are not in *any* television band, as your antennas
are all in the 300-400 MHz range.

Why are you using an impedance transformer? Remember the impedance of
a dipole is about 73 ohms. Your coax is about the same. The 300:75 ohm
transformer just gives you a 4:1 SWR, probably resulting in a fair amount
of pickup by the coax as well as the antenna.

Alan
wa6azp

Sent DB2 back: Homemade HDTV antenna idea?
 

On Mar 5, 1:00*pm, (Alan) wrote:
In article Jim Wilkins writes:





On Mar 4, 4:28=A0pm, wrote:

So..... I recognize that what I need is an OUTSIDE
antenna and one as high as possible.... matter of fact
these two parameter are more important then the
'design" of the antenna I gather?

Right now the active element of my HDTV antenna is two 6" aluminum
rods jammed into the ends of a short horizontal plastic tube. I
drilled and tapped through the inner ends of the rods for stainless
steel screws which hold the rods in and connect to the 300-75 Ohm
matching transformer. Come spring I'll redo it by mounting slightly
longer rods in opposite sides of a plastic box which will protect the
connections from the rain better.

It's actually a home-made replacement part for a Radio Shack UHF
antenna that was damaged in a storm.
Depending on whose formula I use, the end-to-end distance should be 15
to 16 inches. The original was 14.6" but it was made for older, higher
UHF channels.

* I don't know what formulas you are using, but a good start is 468 feet/f
(in MHz). *

That, also this, set to Channel 59, which is currently the highest one
worth receiving here.
http://www.k7mem.150m.com/Electronic...vhf_quick.html

With that, you are not in *any* television band, as your antennas
are all in the 300-400 MHz range.

End to end = BOTH elements.

* Why are you using an impedance transformer? *Remember the impedance of
a dipole is about 73 ohms. *

Two 6" rods = open dipole, like the original. They are hex standoffs
because I didn't have any 3/8" aluminum rod or tube.


* * * * Alan
wa6azp-

Sent DB2 back: Homemade HDTV antenna idea?
 

On Mar 5, 1:51*am, wrote:
I commend you for your resourcefulness, but if you're gonna build
for
the outside, why don't you take an ohmmeter down to the hardware
store
or scrapyard and find something more durable than unshielded
coaxial?

What in the hell is unshielded coax? If it has no shield, it isn't
coax.

GG

Sent DB2 back: Homemade HDTV antenna idea?
 

* the outside, why don't you take an ohmmeter down to the hardware
store

An ohmmeter won't help, except to show that the coax isn't open or
shorted. The "75 Ohms" is the ratio of voltage to current and it's
controlled by the distributed series inductance and parallel
capacitance.

Sent DB2 back: Homemade HDTV antenna idea?
 

In article Jim Wilkins writes:
On Mar 5, 1:00=A0pm, (Alan) wrote:
Jim Wilkins writes:

It's actually a home-made replacement part for a Radio Shack UHF
antenna that was damaged in a storm.
Depending on whose formula I use, the end-to-end distance should be 15
to 16 inches. The original was 14.6" but it was made for older, higher
UHF channels.

I don't know what formulas you are using, but a good start is 468 feet=
/f
(in MHz).

That, also this, set to Channel 59, which is currently the highest one
worth receiving here.
http://www.k7mem.150m.com/Electronic...vhf_quick.html

Actually, you should look at:

http://www.k7mem.150m.com/Electronic...as/dipole.html

which gives the formula 468/f. The page you give is for building yagis,
and the reaction between the elements makes the lengths different than
for dipoles.

With that, you are not in *any* television band, as your antennas
are all in the 300-400 MHz range.

End to end = BOTH elements.

Yes, exactly, as in the web page I referred to.

Why are you using an impedance transformer?
Remember the impedance of a dipole is about 73 ohms.

Two 6" rods = open dipole, like the original. They are hex standoffs
because I didn't have any 3/8" aluminum rod or tube.

I was asking about why you used the 300 ohm to 75 ohm impedance
transformer. You have 75 ohm cable, and an approximately 75 ohm
antenna -- the transformer just makes things bad.

Two 6 inch rods adds up to 12 inches, not 15 inches.

Alan

Sent DB2 back: Homemade HDTV antenna idea?
 

John McGaw wrote:

Of course, a thinking person would have taken the DB-2 antenna an placed it
in a suitable location outside and used it as originally intended and
probably had a good signal with little effort, no experimentation, and no
return necessary. To quote the maker: "...the DB2 was originally designed
for outdoor use..."

http://www.antennasdirect.com/DB2_Indoor_antenna.html

A "thinking" person would send it back and get the DB4
or something for high VHF bands

Sent DB2 back: Homemade HDTV antenna idea?
 

"Alan" wrote

Two 6 inch rods adds up to 12 inches, not 15 inches.

He's probably got the two rods spaced 3" apart. A *little* knowledge can be
a dangerous thing! ;-)

In my earlier proposed "experimental" wire dipole, I suggested a 12" one,
never remembering what frequencies UHF TV occupies. So for 300 - 400 MHz, it
should have been measured to be about 16" +/- overall for 350 MHz.

Sent DB2 back: Homemade HDTV antenna idea?
 

On Mar 5, 6:21*pm, "Howard Lester" wrote:
"Alan" * wrote

*Two 6 inch rods adds up to 12 inches, not 15 inches.

He's probably got the two rods spaced 3" apart. A *little*
knowledge can be
a dangerous thing! ;-)

In my earlier proposed "experimental" wire dipole, I suggested a
12" one,
never remembering what frequencies UHF TV occupies. So for 300 -
400 MHz, it
should have been measured to be about 16" +/- overall for 350 MHz.

I found this a while back in HDTV Magazine. Definitely check 'page 2
rev 2'

http://www.prism.gatech.edu/~wn17/

GG
GG

Sent DB2 back: Homemade HDTV antenna idea?
 

"G-squared" wrote

I found this a while back in HDTV Magazine. Definitely check 'page 2
rev 2'

http://www.prism.gatech.edu/~wn17/

THAT is hysterical, and incredibly ingenious. It probably works a little
better than a dipole, huh? ;-)

I wonder if that'd qualify as an acceptable rooftop tv antenna in a
subdivision ruled by a homeowner's association (per the FCC ruling years
ago). Put a rotator on it and....

Sent DB2 back: Homemade HDTV antenna idea?
 

G-squared wrote:

I found this a while back in HDTV Magazine. Definitely check 'page 2
rev 2'

http://www.prism.gatech.edu/~wn17/



Very cool!!

Sent DB2 back: Homemade HDTV antenna idea?
 

"Howard Lester" wrote:

Partly right. A lesser quality antenna high and in the clear outside will
generally outperform a better one indoors at ground level. The experimenter
in me would try making a dipole antenna out of the end of the coax.

I live in an apartment complex and it difficult for me
to mount an outside antenna..... I'm not handy...don't
have any tools.... no mast to mount it to.

What I need is some kind of "flexible" antenna that can
be hung up for a tree or even mounted upside a
wall..... then taken down and rolled up when moving

I know ham radio operators on field day often take a
bow an arrow and shoot an antenna wire up into a tree
and then can easily roll it back up when done.

Does anything like this exist for HDTV for someone like
me? Or can I just MAKE one for 100 feet of coax? Maybe
make this dipole? Or just strip off a few feet to
expose bare wire?

I'm just playing around for now..experimenting...if I
need to buy another real antenna I will but not now

Sent DB2 back: Homemade HDTV antenna idea?
 

On Thu, 06 Mar 2008 10:09:58 -0600, me wrote:

Does anything like this exist for HDTV for someone like me? Or can I
just MAKE one for 100 feet of coax? Maybe make this dipole? Or just
strip off a few feet to expose bare wire?

When I visited my cousin, I was surprised to see that she could get TV
reception with her antenna connected to a sat dish, It wasn't real good,
but it was there. Redoing her setup and hooking up a cheap STB antenna in
front of the window gave here excellent ATSC reception. Might try touching
the coax to a metal window frame on the side towards the stations if you
don't want to sprung for a $2 bowtie antenna.

--
Want the ultimate in free OTA SD/HDTV Recorder? http://mythtv.org
My Tivo Experience http://wesnewell.no-ip.com/tivo.htm
Tivo HD/S3 compared http://wesnewell.no-ip.com/mythtivo.htm
AMD cpu help http://wesnewell.no-ip.com/cpu.php

Sent DB2 back: Homemade HDTV antenna idea?
 

On Mar 6, 5:08*am, "Howard Lester" wrote:
"G-squared" * wrote
I found this a while back in HDTV Magazine. Definitely check
'page 2
rev 2'
http://www.prism.gatech.edu/~wn17/

THAT *is hysterical, and incredibly ingenious. It probably works a
little
better than a dipole, huh? * ;-)

I wonder if that'd qualify as an acceptable rooftop tv antenna in a
subdivision ruled by a homeowner's association (per the FCC ruling
years
ago). *Put a rotator on it and....

I suspect you'd have a _real_ bad time in a storm but if you think
about it, one of those perforated metal commercial trash cans would be
as good electrically but being partly open would be far less of a wind
load. Better yet, a welded wire 'basket' could be less ugly and even
less wind load.

GG

Sent DB2 back: Homemade HDTV antenna idea?
 

Howard Lester wrote:
"G-squared" wrote

I found this a while back in HDTV Magazine. Definitely check 'page 2
rev 2'

http://www.prism.gatech.edu/~wn17/

THAT is hysterical, and incredibly ingenious. It probably works a little
better than a dipole, huh? ;-)

I wonder if that'd qualify as an acceptable rooftop tv antenna in a
subdivision ruled by a homeowner's association (per the FCC ruling years
ago). Put a rotator on it and....




You don't tell the HOA it's a TV antenna, you tell the HOA it's a
squirrel trap and let the HOA think you're doing the whole neighborhood
a favor.

--
jer
email reply - I am not a 'ten'

Sent DB2 back: Homemade HDTV antenna idea?
 

"Jer" wrote

You don't tell the HOA it's a TV antenna, you tell the HOA it's a squirrel
trap and let the HOA think you're doing the whole neighborhood a favor.

Or paint it orange and call it a wind sock...