A DTV antenna
 

In article ,
Gordon wrote:

1) Right now all the digital transmissions are in the UHF band.
but in 6 weeks, three stations will move back to their VHF
assignments in the VHF high band.
How well can I expect my antenna to work in that frequency band?

Not terribly well. "Short" antennas (significantly less than 1/2
wavelength) have a very reactive impedance, and don't couple
efficiently to the E/M wave.

It may work well enough for your area (depending on the VHF signal
strength) or maybe not.

2) I have not trimmed or dressed the twin lead from the bowties.
I understand that twin-lead can act as antennas.

Yup. Sometimes a problem, sometimes not.

Sensitivity of twinlead to external fields can be reduced by twisting
the twinlead (one rotation every six inches or every foot is a decent
starting point) and by keeping it a few inches away from anything
metal. Use insulating standoffs to run it down the antenna mast.

Or, convert from the twinlead to a 75-ohm coax (e.g. RG-8) using a
balun, and run coax down to your TV.

So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

Trim it back to a reasonable minimum length, don't loop it back along
itself or run it next to itself (or other twinlead, or anything
metal), and twist it periodically.

4) Any suggestions for alternitive DIY designs?

You may want to consider adding a "folded dipole" in parallel with the
bowtie arrangement, with the dipole being cut to the wavelength of the
lowest-frequency VHF channel you'll want to receive.

If you need more gain or directivity on VHF than a dipole will give
you, then using a log-periodic antenna (the classic rooftop VHF/UHF
type) may be your best bet. These *can* be home-brewed but they're
more complex than a simple bowtie-and-reflector.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

A DTV antenna
 

This seems to be the only news group devoted to the topic of antennas.
(and the origins of the universe). So maybe you guys can help me
with this.

I have been experimenting with fabricating a decent
indoor DTV antenna. I have tried several things. What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

It seems to give pretty good performance. It could be better.
But I am wondering about a few things.

1) Right now all the digital transmissions are in the UHF band.
but in 6 weeks, three stations will move back to their VHF
assignments in the VHF high band.
How well can I expect my antenna to work in that frequency band?

2) I have not trimmed or dressed the twin lead from the bowties.
I understand that twin-lead can act as antennas. So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

3) Any suggestions to improve this design?

4) Any suggestions for alternitive DIY designs?

Thanks

A DTV antenna
 

On Apr 24, 10:33*pm, Gordon wrote:
This seems to be the only news group devoted to the topic of antennas.
(and the origins of the universe). *So maybe you guys can help me
with this. *

I have been experimenting with fabricating a decent
indoor DTV antenna. *I have tried several things. *What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

It seems to give pretty good performance. It could be better.
*But I am wondering about a few things.

1) Right now all the digital transmissions are in the UHF band.
*but in 6 weeks, three stations will move back to their VHF
*assignments in the VHF high band.
*How well can I expect my antenna to work in that frequency band?

2) I have not trimmed or dressed the twin lead from the bowties.
* I understand that twin-lead can act as antennas. *So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

3) Any suggestions to improve this design?

4) Any suggestions for alternitive DIY designs?

Thanks

If you search for "diy hdtv antenna" or "diy dtv antenna" you will
come up with other ideas. Someone posted a question a while back here
about a design that apparently is pretty forgiving and not too hard to
construct and is claimed to give decent gain; see
http://www.digitalhome.ca/ota/superantenna/.

Dave P's comments are good, though RG-8 is 50 ohm, not 75 ohm. Good
RG-6 type cable should work well for at least short runs, and it is
nominally 75 ohms. I don't know about your TV (or converter box), but
pretty much all the ones I've seen that receive digital TV broadcasts
have 75 ohm F connector inputs anyway, so you may as well go straight
to RG-6 at the source (the antenna).

Cheers,
Tom

A DTV antenna
 

On 25 Apr 2009 06:33:45 +0100, Gordon wrote:

I have been experimenting with fabricating a decent
indoor DTV antenna.

Hi Gordon,

This is a goal in conflict if we are to take it at face value. For
one, DTV has design demands that call for widebandedness. This, and
the combination for VHF coverage combine to drive the design to being
large. This is typically the domain of outdoor antennas, and for good
reason (large for DTV is going to be honestly large).

I have tried several things. What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

It seems to give pretty good performance. It could be better.
But I am wondering about a few things.

1) Right now all the digital transmissions are in the UHF band.
but in 6 weeks, three stations will move back to their VHF
assignments in the VHF high band.
How well can I expect my antenna to work in that frequency band?

This is a simple matter of scaling. If the frequency shift is by an
order of, say, 2:1; then the size will increase by an order of 1:2.
Frequency and size are in an inverse relationship. Try doubling the
size of your current design, and looking for a gallon size peanut
butter jar.

2) I have not trimmed or dressed the twin lead from the bowties.
I understand that twin-lead can act as antennas. So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

This is an indoor antenna. It is going to suffer from any number of
things in proximity and your attempts to dress the leads probably were
not responsible for the signal quality change you observed. I will
bet that attempt to make a neat assembly had a lot of re-arranging
going on in addition to the lead dressing.

3) Any suggestions to improve this design?

4) Any suggestions for alternitive DIY designs?

Wait until you have a problem before you try solutions. As I said
above, your goal is in conflict with interior available dimensions.
The truth of the matter is that a simple rabbit ears antenna might do
just as well as the best of the DIY designs littering pages across the
WWW.

73's
Richard Clark, KB7QHC

A DTV antenna
 

Richard Clark wrote in
:

On 25 Apr 2009 06:33:45 +0100, Gordon wrote:

I have been experimenting with fabricating a decent
indoor DTV antenna.

Hi Gordon,

This is a goal in conflict if we are to take it at face value. For
one, DTV has design demands that call for widebandedness. This, and
the combination for VHF coverage combine to drive the design to being
large. This is typically the domain of outdoor antennas, and for good
reason (large for DTV is going to be honestly large).

I know. I'm trying to find a good compromise. But it may not
exist. Unfortunatly, I can't mount an outdoor antenna. I rent,
and the landlord won't alow it.

I have tried several things. What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

It seems to give pretty good performance. It could be better.
But I am wondering about a few things.

1) Right now all the digital transmissions are in the UHF band.
but in 6 weeks, three stations will move back to their VHF
assignments in the VHF high band.
How well can I expect my antenna to work in that frequency band?

This is a simple matter of scaling. If the frequency shift is by an
order of, say, 2:1; then the size will increase by an order of 1:2.
Frequency and size are in an inverse relationship. Try doubling the
size of your current design, and looking for a gallon size peanut
butter jar.

I've done the math. Channel 2 has a wavelength of about 18 feet and
channel 50 is about 1.4 feet. More than a 2:1 ratio. I do catch a
break since the VHF lo band is going to be vacated in this area. So
channel 8 is the lowest frequency I need to worry about (wavelength
of approx 5.5 feet).


2) I have not trimmed or dressed the twin lead from the bowties.
I understand that twin-lead can act as antennas. So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

This is an indoor antenna. It is going to suffer from any number of
things in proximity and your attempts to dress the leads probably were
not responsible for the signal quality change you observed. I will
bet that attempt to make a neat assembly had a lot of re-arranging
going on in addition to the lead dressing.


Actually, I tried to keep the situation as controlled as possible.
I initially had the leads just drapped down the "mast" (dowel) to
a balun. It was my wife that tried to improve the asthetics by
neatening up the twinleads. Then she complained that reception
was bad. That's when I was experimenting with the dressing of
the leads. Right now I have it "dressed ugly", but it works.

3) Any suggestions to improve this design?

4) Any suggestions for alternitive DIY designs?

Wait until you have a problem before you try solutions. As I said
above, your goal is in conflict with interior available dimensions.
The truth of the matter is that a simple rabbit ears antenna might do
just as well as the best of the DIY designs littering pages across the
WWW.

No, the rabbit ears didn't work very well at all. That's why I have been
experimenting. I have seen a lot of the DIY designs littering the
WWW. This dual bowtie design is mine, tho.


73's
Richard Clark, KB7QHC

A DTV antenna
 

On 26 Apr 2009 00:56:11 +0100, Gordon wrote:

I've done the math. Channel 2 has a wavelength of about 18 feet and
channel 50 is about 1.4 feet. More than a 2:1 ratio. I do catch a
break since the VHF lo band is going to be vacated in this area. So
channel 8 is the lowest frequency I need to worry about (wavelength
of approx 5.5 feet).

Hi Gordon,

Yes, you've got the minimum specifications there. The widest part of
your antenna, at an optimum, would be something under 3 feet (half the
channel 8 wavelength) - still pretty big for indoors, especially if
the stations are in an awkward angle.

And speaking of stationS (accent on the plural), your design
requirements are going to be complex if they are not all on the same
axis/direction. And speaking further of stationS, you will need to
cover a broad range of frequencies.

The usual, optimal design is called a Log Periodic Dipole Array (or
variants of Log _______ ). It would qualify for being both
widebanded enough for one, or many, adjacent channels (growing in
length and element count for additional channels). This is why I
described the optimal antenna as being "honestly" big.

Smaller antennas are not going to deliver performance - but, again,
you may not need optimum, nor performance when the time comes. The
bow tie you've described elsewhere seems a suitable compromise.

Actually, I tried to keep the situation as controlled as possible.
I initially had the leads just drapped down the "mast" (dowel) to
a balun. It was my wife that tried to improve the asthetics by
neatening up the twinleads. Then she complained that reception
was bad. That's when I was experimenting with the dressing of
the leads. Right now I have it "dressed ugly", but it works.

Twinlead is fairly robust "except" when it is in close (three widths)
to metal or an RF absorber. As marginal as your situation sounds, my
bets are still with clutter near the antenna which is MORE prone to
disturbance than the line is.

No, the rabbit ears didn't work very well at all. That's why I have been
experimenting. I have seen a lot of the DIY designs littering the
WWW. This dual bowtie design is mine, tho.

When the band shift comes, rabbit ears could work quite well. Don't
take the plunge into elaborate designs until you have some basis of
comparison is all I am suggesting.

73's
Richard Clark, KB7QHC

A DTV antenna
 

K7ITM wrote in news:9134ad02-e551-4c5c-becf-05717feb8546
@y6g2000prf.googlegroups.com:

If you search for "diy hdtv antenna" or "diy dtv antenna" you will
come up with other ideas. Someone posted a question a while back here
about a design that apparently is pretty forgiving and not too hard to
construct and is claimed to give decent gain; see
http://www.digitalhome.ca/ota/superantenna/.

I have done that. In fact I have seen plenty of designs: Yagis,
The Coathanger antenna, etc. I have printed up the design of the
Grey-Hoverman. I could even build up a copy of the pVC design
and place it against the house, outside.
We actually had the Radio Shack model that is mentioned
on that site. my dad had it in the pre-CATV days. When I began to
set up the DTV reciever, I asked my dad about the old antenna, but
he didn't know what became of it.


Dave P's comments are good, though RG-8 is 50 ohm, not 75 ohm. Good
RG-6 type cable should work well for at least short runs, and it is
nominally 75 ohms. I don't know about your TV (or converter box), but
pretty much all the ones I've seen that receive digital TV broadcasts
have 75 ohm F connector inputs anyway, so you may as well go straight
to RG-6 at the source (the antenna).

I'm not sure what type of RG I am using. I should point out that I
have the twinleads running down the dowel to a balun. From there,
about 3 to 4 feet of coax runs to the converter box. I could just
put the converter closer to the antenna and slip the balun right
onto the converter.

A DTV antenna
 

Gordon wrote:
Unfortunatly, I can't mount an outdoor antenna. I rent,
and the landlord won't allow it.

Isn't there a federal law allowing TV antennas?
Or did you sign a personal contract agreeing
not to install a TV antenna?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

A DTV antenna
 

Unfortunatly, I can't mount an outdoor antenna. I rent,
and the landlord won't allow it.

Isn't there a federal law allowing TV antennas?
Or did you sign a personal contract agreeing
not to install a TV antenna?

The OTARD rule (to which you're referring) allows installation of an
over-the-air TV antenna, but it only applies if the antenna is
installed in an area which is exclusively for the tenant's use.

People who rent houses are usually able to take advantage of it.
Apartment dwellers often can't, because they aren't renting the whole
building and thus don't have "exclusive use" rights to the roof or
exterior.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

A DTV antenna
 

In message , Richard Clark
writes







When the band shift comes, rabbit ears could work quite well. Don't
take the plunge into elaborate designs until you have some basis of
comparison is all I am suggesting.

I would start with sticking a screwdriver in the TV antenna socket.

While a properly designed and constructed DTV antenna, mounted in the
right place, will undoubtedly work well, some of the homebrew designs
you find on the internet are probably even less efficient than a
screwdriver.
--
Ian

A DTV antenna
 

Dave Platt wrote:
Unfortunatly, I can't mount an outdoor antenna. I rent,
and the landlord won't allow it.
Isn't there a federal law allowing TV antennas?
Or did you sign a personal contract agreeing
not to install a TV antenna?

The OTARD rule (to which you're referring) allows installation of an
over-the-air TV antenna, but it only applies if the antenna is
installed in an area which is exclusively for the tenant's use.

People who rent houses are usually able to take advantage of it.
Apartment dwellers often can't, because they aren't renting the whole
building and thus don't have "exclusive use" rights to the roof or
exterior.


But if you have a terrace or a porch, you may install a receiving
antenna for broadcast or satellite on that porch.

A DTV antenna
 

Ian Jackson wrote:
In message , Richard Clark
writes







When the band shift comes, rabbit ears could work quite well. Don't
take the plunge into elaborate designs until you have some basis of
comparison is all I am suggesting.

I would start with sticking a screwdriver in the TV antenna socket.

While a properly designed and constructed DTV antenna, mounted in the
right place, will undoubtedly work well, some of the homebrew designs
you find on the internet are probably even less efficient than a
screwdriver.

I have seen some very clever antennas on the internet. More clever than
the BS this newsgroup is top-heavy with.

A DTV antenna
 

Dave Platt wrote:
The OTARD rule (to which you're referring) allows installation of an
over-the-air TV antenna, but it only applies if the antenna is
installed in an area which is exclusively for the tenant's use.

People who rent houses are usually able to take advantage of it.
Apartment dwellers often can't, because they aren't renting the whole
building and thus don't have "exclusive use" rights to the roof or
exterior.

However, they do have exclusive rights to their balcony
or patio so that's something to consider.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

A DTV antenna
 

On 25 Apr 2009 06:33:45 +0100, Gordon wrote:

This seems to be the only news group devoted to the topic of antennas.
(and the origins of the universe). So maybe you guys can help me
with this.

Cosmology is often easier to understand than the antenna designs.

I have been experimenting with fabricating a decent
indoor DTV antenna.

Please define "decent". You know, the numbers.
How big? (max allowed length, width, height)
How much bandwidth (VHF, UHF, or both?)
Minimum (average) gain?
Mounting limitations?
Omni or directional? Rotator?

I'm also partial to NEC2 models of creative designs. They often show
problems that are not obvious until after the antenna is built. If
you're going to design your own, spend the time building a model.

I have tried several things.

You seem to have done your homework. Also see:
http://www.hdtvprimer.com/ANTENNAS/comparing.html
Some are indoor antennas, which should give you a clue as to what to
expect.

What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

2 element yagi like design?

It seems to give pretty good performance. It could be better.

But I am wondering about a few things.

1) Right now all the digital transmissions are in the UHF band.
but in 6 weeks, three stations will move back to their VHF
assignments in the VHF high band.
How well can I expect my antenna to work in that frequency band?

Dunno. I haven't seen any dimensions. Plug the current design into
an NEC model and see what comes out at VHF frequencies. My guess is
that it will be worse than hideous. You would do better with
adjustable rabbit ears.

2) I have not trimmed or dressed the twin lead from the bowties.
I understand that twin-lead can act as antennas. So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

Lose the twin lead. The problem with balance line is that any
mechanical imbalance (i.e. proximity to walls, objects, people, etc)
will unbalance the line, causing some radiation. Such radiation shows
up as loss, something you can barely tolerate with such a minimal
antenna. If your design is setup for a 300 ohm match, install a balun
and run 75 ohm RG-6/u coax instead.

3) Any suggestions to improve this design?

Improve how? More gain? More bandwidth? Smaller? Numbers please.

4) Any suggestions for alternitive DIY designs?

Yes, but you may find them rather unconventional.

I once built a log periodic antenna on a sheet of plywood, using #14
AWG house wire and two parallel wires for the transmission line.
Elements were arranged on both sides of the plywood and secured with a
staple gun. This was for a ladyfriend, who was stuck with severe
limitations on outside antenna installations. I hung it from the
ceiling, which was the only place suitable for the monstrosity. 4-6dBi
gain from 60 to 800MHz (no channel 2). Where were a few ghosts, but
it worked much better than the rabbit ears and UHF loop it replaced.
However, it only lasted about a month. The landlord found out and
demanded its removal while muttering something about attracting flying
saucers and alien visitors. Oh well.

Another TV antenna I built took advantage of the chicken wire buried
under the stucco outside of the house. The chicken wire acted as the
antenna reflector, which was conveniently arranged in the right
direction. The driven elements were 4ea phased bow-tie dipoles,
hidden behind a decorative wood grating. It didn't work as well as I
predicted, but good enough to get decent OTA TV reception.

If you have a suitable window facing the right direction, you can do
something with aluminum foil tape. I use aluminum duct tape cut down
to size for this purpose. For electrical connections, copper stained
glass tape soldered to the coax cable. Any antenna with horizontal
polarization will work. You won't get much gain, but the outside
window location will somewhat compensate for the lack of gain by
offering a less cluttered line of sight to the TV xmitter.

Anyway, use your imagination, but also run the numbers and do a model.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

A DTV antenna
 

On Apr 26, 12:17*am, (Dave Platt) wrote:
Unfortunatly, I can't mount an outdoor antenna. *I rent,
and the landlord won't allow it.

Isn't there a federal law allowing TV antennas?
Or did you sign a personal contract agreeing
not to install a TV antenna?

The OTARD rule (to which you're referring) allows installation of an
over-the-air TV antenna, but it only applies if the antenna is
installed in an area which is exclusively for the tenant's use.

People who rent houses are usually able to take advantage of it.
Apartment dwellers often can't, because they aren't renting the whole
building and thus don't have "exclusive use" rights to the roof or
exterior.

--
Dave Platt * * * * * * * * * * * * * * * * * AE6EO
Friends of Jade Warrior home page: *http://www.radagast.org/jade-warrior
* I do _not_ wish to receive unsolicited commercial email, and I will
* * *boycott any company which has the gall to send me such ads!

Unless they have a balcony which is their "own space".

A DTV antenna
 

On Sun, 26 Apr 2009 16:54:12 -0700, Jeff Liebermann
wrote:

What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

Like this?
http://www.hdtvprimer.com/ANTENNAS/DoubleBow.html

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

A DTV antenna
 

Dave Platt wrote:
Unfortunatly, I can't mount an outdoor antenna. I rent,
and the landlord won't allow it.
Isn't there a federal law allowing TV antennas?
Or did you sign a personal contract agreeing
not to install a TV antenna?

The OTARD rule (to which you're referring) allows installation of an
over-the-air TV antenna, but it only applies if the antenna is
installed in an area which is exclusively for the tenant's use.

People who rent houses are usually able to take advantage of it.
Apartment dwellers often can't, because they aren't renting the whole
building and thus don't have "exclusive use" rights to the roof or
exterior.


It's considerably more subtle than that, since there are large
commercial interests at play (unlike for ham antennas)..

Go to the FCC OTARD page and get the real scoop.
http://www.fcc.gov/mb/facts/otard.html

As a practical matter, the courts/adminstrative law judges have held
that the landlord's control does not cover, for instance, the air space
outside your window, so if you can mount the antenna within the window's
dimensions(either inside or outside), you're good to go. It is ok for
the landlord to prohibit, say, attaching to the wall outside, though.
Whether the window frame itself is "under your control" is another question.

A DTV antenna
 

Jeff Liebermann wrote in
:

On Sun, 26 Apr 2009 16:54:12 -0700, Jeff Liebermann
wrote:

What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

Like this?
http://www.hdtvprimer.com/ANTENNAS/DoubleBow.html


Sort of. At least that's the right configuration.
What I did was to go out and buy a pair of bowties
from Radio Shack. Then I got a dowel at Ace Hardware.
I clipped the bowties 7" apart (measured on center).
to the dowel. The bowties came with about 12" or so
of twin-lead attached. I ran these to a balun and
then through a short length of coax to the DTV converter.
I don't have a reflector, but one could be used to
improve directionality.

A DTV antenna
 

Jeff Liebermann wrote in
:

On 25 Apr 2009 06:33:45 +0100, Gordon wrote:

This seems to be the only news group devoted to the topic of antennas.
(and the origins of the universe). So maybe you guys can help me
with this.

Cosmology is often easier to understand than the antenna designs.

I have been experimenting with fabricating a decent
indoor DTV antenna.

Please define "decent". You know, the numbers.

Decent is subjective. When I first hooked up the
converter box I used the rabbit ears. They didn't
work worth a darn. Signal strength (according to
the OSD indicator) was 40 at best. THe picture
and sound were constantly breaking up. I then hooked
up a bowtie and got better reception, but only barely.
That's when i got the idea for the double bowtie. Now
my worst signal strength is 40 and my best is 75.
Still could use some improvement, but picture quality
is good.


How big? (max allowed length, width, height)

That's the thing. I don't have room for a ginormus
antenna.

How much bandwidth (VHF, UHF, or both?)

Right now, UHF 27 to 48.
After the change over, add VHF 8, 10, and 12.

Minimum (average) gain?
Mounting limitations?

Prefer indoor not outdoor. A high ceiling makes that
mounting arangement unusable. Although I could hang
a flat antenna on the wall around the corner from the
TV.

Omni or directional? Rotator?

All the stations are located within a 7 degree cluster, due
east from my location. Directional is good. No rotor needed.


I'm also partial to NEC2 models of creative designs. They often show
problems that are not obvious until after the antenna is built. If
you're going to design your own, spend the time building a model.

I have tried several things.

You seem to have done your homework. Also see:
http://www.hdtvprimer.com/ANTENNAS/comparing.html
Some are indoor antennas, which should give you a clue as to what to
expect.

What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

2 element yagi like design?

It seems to give pretty good performance. It could be better.

But I am wondering about a few things.

1) Right now all the digital transmissions are in the UHF band.
but in 6 weeks, three stations will move back to their VHF
assignments in the VHF high band.
How well can I expect my antenna to work in that frequency band?

Dunno. I haven't seen any dimensions. Plug the current design into
an NEC model and see what comes out at VHF frequencies. My guess is
that it will be worse than hideous. You would do better with
adjustable rabbit ears.

2) I have not trimmed or dressed the twin lead from the bowties.
I understand that twin-lead can act as antennas. So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

Lose the twin lead. The problem with balance line is that any
mechanical imbalance (i.e. proximity to walls, objects, people, etc)
will unbalance the line, causing some radiation. Such radiation shows
up as loss, something you can barely tolerate with such a minimal
antenna. If your design is setup for a 300 ohm match, install a balun
and run 75 ohm RG-6/u coax instead.

3) Any suggestions to improve this design?

Improve how? More gain? More bandwidth? Smaller? Numbers please.

4) Any suggestions for alternitive DIY designs?

Yes, but you may find them rather unconventional.

I once built a log periodic antenna on a sheet of plywood, using #14
AWG house wire and two parallel wires for the transmission line.
Elements were arranged on both sides of the plywood and secured with a
staple gun. This was for a ladyfriend, who was stuck with severe
limitations on outside antenna installations. I hung it from the
ceiling, which was the only place suitable for the monstrosity. 4-6dBi
gain from 60 to 800MHz (no channel 2). Where were a few ghosts, but
it worked much better than the rabbit ears and UHF loop it replaced.
However, it only lasted about a month. The landlord found out and
demanded its removal while muttering something about attracting flying
saucers and alien visitors. Oh well.

Another TV antenna I built took advantage of the chicken wire buried
under the stucco outside of the house. The chicken wire acted as the
antenna reflector, which was conveniently arranged in the right
direction. The driven elements were 4ea phased bow-tie dipoles,
hidden behind a decorative wood grating. It didn't work as well as I
predicted, but good enough to get decent OTA TV reception.

If you have a suitable window facing the right direction, you can do
something with aluminum foil tape. I use aluminum duct tape cut down
to size for this purpose. For electrical connections, copper stained
glass tape soldered to the coax cable. Any antenna with horizontal
polarization will work. You won't get much gain, but the outside
window location will somewhat compensate for the lack of gain by
offering a less cluttered line of sight to the TV xmitter.

Anyway, use your imagination, but also run the numbers and do a model.

A DTV antenna
 

Ian Jackson wrote in
:

I would start with sticking a screwdriver in the TV antenna socket.

While a properly designed and constructed DTV antenna, mounted in the
right place, will undoubtedly work well, some of the homebrew designs
you find on the internet are probably even less efficient than a
screwdriver.


You mean, like the beer can antenna?? Sorry, I don't have
a link.

A DTV antenna
 

Cecil Moore wrote in news:R0QIl.15486$pr6.5577
@flpi149.ffdc.sbc.com:

Gordon wrote:
Unfortunatly, I can't mount an outdoor antenna. I rent,
and the landlord won't allow it.

Isn't there a federal law allowing TV antennas?
Or did you sign a personal contract agreeing
not to install a TV antenna?

There may well be. But my landlord has shown an
active disregard for any such landlord/tennent laws
and there may also be neighborhood CC&R's.

I did find plans on the internet for a huge dual
Hoverman design. A terrible overkill for my
purposes. But, I could lean such a thing against
a wall outside of where the TV is located.

A DTV antenna
 

Gordon wrote:
Cecil Moore wrote in news:R0QIl.15486$pr6.5577
@flpi149.ffdc.sbc.com:

Gordon wrote:
Unfortunatly, I can't mount an outdoor antenna. I rent,
and the landlord won't allow it.
Isn't there a federal law allowing TV antennas?
Or did you sign a personal contract agreeing
not to install a TV antenna?

There may well be. But my landlord has shown an
active disregard for any such landlord/tennent laws
and there may also be neighborhood CC&R's.

Your landlord may show a disregard, but he can't actually do anything.
As in, he can't evict you (what would be the grounds? whatever is in
your lease/rental contract is superseded by federal law in this case)
(granted, he can try to evict you, and you'd potentially have to go to
court to fight it, but he can't get the sheriff out to remove you, and
if he does a "self-help" eviction, he's committing a felony: breaking
and entering, burglary, etc.)

CC&Rs are even more toothless here. There's a presumption that what you
want to do is legal, and the HOA would have to prove otherwise, and in
the mean time, you get to keep your antenna. Read the FCC page.


I did find plans on the internet for a huge dual
Hoverman design. A terrible overkill for my
purposes. But, I could lean such a thing against
a wall outside of where the TV is located.

A DTV antenna
 

On Apr 25, 1:33*am, Gordon wrote:
This seems to be the only news group devoted to the topic of antennas.
(and the origins of the universe). *So maybe you guys can help me
with this. *

I have been experimenting with fabricating a decent
indoor DTV antenna. *I have tried several things. *What I have
now is two bowties spaced about 7 inches apart on a wood dowel.
A peanut butter jar with rocks in it makes up the base.

It seems to give pretty good performance. It could be better.
*But I am wondering about a few things.

1) Right now all the digital transmissions are in the UHF band.
*but in 6 weeks, three stations will move back to their VHF
*assignments in the VHF high band.
*How well can I expect my antenna to work in that frequency band?

2) I have not trimmed or dressed the twin lead from the bowties.
* I understand that twin-lead can act as antennas. *So what
is the best way to manage the twinlead? Cut it back? I noticed
that when i laid the leads together, in an attempt to make a
neat assembly, I got signal cancelation.

3) Any suggestions to improve this design?

4) Any suggestions for alternitive DIY designs?

Thanks

Gordon, I installed a large radio shack "tagi" type TV receiving
antenna in my attic 10 years since the house came wired for it. I
pointed the antenna in the general direction of the transmitting
antennae in my area and received excellent analog reception even with
the 5-10dB attenuation that occurs with VHF and UHF from the wooden
roof with asphalt shingles. I even have a rotor but never had to
really use it.

Now, with DTV, the exact same antenna gives me excellent reception as
well, just as good as analog (but of course "better" due to the nature
of DTV broadcasts).

I think for DTV that uses both UHF and VHF, you should be able to use
the same antenna that you used with the analog system that used UHF
and VHF and (as you know) you will probably find that the digital
signal is better in any case. Whatever their technology, these are all
multiband receiving antennas and the spectra for DTV and analog TV are
much the same. There are no technical aspects that need to be covered
here because there really is no problem.

Regards,

73 de AI4QJ

A DTV antenna
 

A DTV antenna
 

"Gordon" wrote in message
...

snip


That's the thing. I don't have room for a ginormus
antenna.

.... but since you've built a small antenna and it's working, you may have
options for _placement_ that will enhance your reception further. It may
work better at one east-facing window than another and it may work best at a
particular height off the floor at that "better window." (Outside TV
antennas are sometimes installed after one guy walks the roof with the
antenna on a stick, while somebody else monitors the signal; the antenna is
finally mounted when they pick the "sweet spot," like on a tennis racket.)

Adding coaxial cable usually reduces the signal, but if your "better window"
only requires a smidgeon more of coax, maybe you should try it.

A DTV antenna
 

"Sal M. Onella" wrote in
:


"Gordon" wrote in message
...

snip


That's the thing. I don't have room for a ginormus
antenna.

... but since you've built a small antenna and it's working, you may
have options for _placement_ that will enhance your reception further.
It may work better at one east-facing window than another and it may
work best at a particular height off the floor at that "better
window." (Outside TV antennas are sometimes installed after one guy
walks the roof with the antenna on a stick, while somebody else
monitors the signal; the antenna is finally mounted when they pick
the "sweet spot," like on a tennis racket.)

Adding coaxial cable usually reduces the signal, but if your "better
window" only requires a smidgeon more of coax, maybe you should try
it.




I don't have any east facing windows. I did take the antenna outside
and put it up on a pole. Just as an experiment. I was not able to
get much better performance. But it was only 6 or 7 feet high.
I supose I could add another element. It would be a cheap enough
experiment. Eliminating the coax is a real possibility.