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Gordon[_2_] · May 1st 09, 05:24 AM posted to rec.radio.amateur.antenna

wrote in
:

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

I guess a bit of background info is in order.
Last March (2008), I decided that I didn't want to pay
$52.00 a month to Comcast for the privelidge of watching
TV or watching my family sit on their asses zoning out
in front of the Boob Tube. So I dropped Cable.
Well, some TV watching is OK. So I hooked up the Rabbit
Ears and Bowtie to watch analoge TV. Reception was poor
to lousy. The problem is that I live in a Triplex that
is oriented East-West. All the transmitters are to the
east of here (in a roughly 10 degree cluster, less than
10 miles away). I am in the western most unit of the
triplex. Which means that I am trying to receive through
the entire length of the unit. The atic space is kinda
tough to get to. The living room has no atic space,
It has a highly slopped ceiling that pretty much follows the
roof line up and over the 2nd floor.
So last June I hooked up a DTV converter box. At first I
used the rabbit ears and got the same poor reception. Then
I tried a set top loop/rabbit ears (a little bit better).
Then I pulled the loop out, and plugged in an old bow-tie
(that made things better). Then I tried the bowtie all
by itself and things got much better. That's when I
decided that a bit more directionality might help. So I
cobbled up the current setup. Two bowties, 7" apart on
a wooden dowel, set in a weighted base. And it actually
works 98% of the time. Today we had good conditions and
the SSI was in the 50s to 70s (yellow and low green)
over all the channels (except for HSN, which is off axis
and I don't care about). So far I have not been able to get
a SSI over 80.
One thing that has helped with the current setup: I am allowing
the twinleads to fall freely down the dowel. I have one
on each side and I am using bread bag clips to keep the
leads separated from each other. It has made reception
more consistent across the channels.
So today I figured I would try to build a better antenna.
I got two dowels and some 14ga wire and (using some plans off
the internet) I built a Hoverman antenna. It didn't work
one whit better than the dual bowtie I already have. At
this point, I may move the hoverman outside and see if I get
better reception there. Or, since the bowtie works so well,
just add more elements to that one.