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

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

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

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.

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.

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

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!

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.

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

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".