I want to setup a bowtie panel antenna to receive UHF Terrestrial TV transmissions in my area. I live between two stations approximately 180 degrees from each other.
Is it practical to build and setup a Bow-tie Panel Antenna and leave off the reflector to cause the antenna to receive signals front and back ?
How much does the reflector add to the gain ? -or- is the reflector primarily there to prevent the antenna from receiving signal reflected off large buildings/mountains from being received by the back of the antenna ?

Any help is appreciated.
Thanks

In article <6e98dc29-c716-4ac4-a999-df0ad79e3cb9n@googlegroups.com>,
sidwelle@gmail.com says...
>
> I want to setup a bowtie panel antenna to receive UHF Terrestrial TV transmissions in my area. I live between two stations approximately 180 degrees from each other.
> Is it practical to build and setup a Bow-tie Panel Antenna and leave off the reflector to cause the antenna to receive signals front and back ?
> How much does the reflector add to the gain ? -or- is the reflector primarily there to prevent the antenna from receiving signal reflected off large buildings/mountains from being received by the back of the antenna ?
>
> Any help is appreciated.
> Thanks
>
>

The reflector does several things. It gives gain to the antenna, it
sets the impedance of the antenna, and in a minor sense it prevents the
signals off the back from being received very well.

Antenna gain can only be had by modifying the antenna pattern. Just
like a light bulb with a reflector. The more gain , the narror the
beam. Think of a light bulb , it sends light out in almost all
directions. PUt a reflector and it sends the light out in mostly one
direction and is much brighter. It also works similar in reverse when
receiving light or radio/TV waves.

YOu can try with out a reflector and see if you get the signal you need
for the stations.

On Thu, 6 Jan 2022 11:07:59 -0500, Ralph Mowery
<rmowery42@charter.net> wrote:

>In article <6e98dc29-c716-4ac4-a999-df0ad79e3cb9n@googlegroups.com>,
>sidwelle@gmail.com says...
>>
>> I want to setup a bowtie panel antenna to receive UHF Terrestrial TV transmissions in my area. I live between two stations approximately 180 degrees from each other.
>> Is it practical to build and setup a Bow-tie Panel Antenna and leave off the reflector to cause the antenna to receive signals front and back ?
>> How much does the reflector add to the gain ? -or- is the reflector primarily there to prevent the antenna from receiving signal reflected off large buildings/mountains from being received by the back of the antenna ?
>>
>> Any help is appreciated.
>> Thanks
>>
>>
>
>The reflector does several things. It gives gain to the antenna, it
>sets the impedance of the antenna, and in a minor sense it prevents the
>signals off the back from being received very well.
>
>Antenna gain can only be had by modifying the antenna pattern.

Or by making the antenna bigger, to intercept more power.

--

I yam what I yam - Popeye

On a sunny day (Thu, 6 Jan 2022 07:47:44 -0800 (PST)) it happened Sid 03
<sidwelle@gmail.com> wrote in
<6e98dc29-c716-4ac4-a999-df0ad79e3cb9n@googlegroups.com>:

>I want to setup a bowtie panel antenna to receive UHF Terrestrial TV transmissions in my area. I live between two stations
>approximately 180 degrees from each other.
>Is it practical to build and setup a Bow-tie Panel Antenna and leave off the reflector to cause the antenna to receive signals
>front and back ?
>How much does the reflector add to the gain ? -or- is the reflector primarily there to prevent the antenna from receiving signal
>reflected off large buildings/mountains from being received by the back of the antenna ?
>
>Any help is appreciated.
>Thanks

Antennas and RF fields are a bit of a mystical thing for the not initiated.
I have a big nice bowtie (was once for TV) and got no usable signal at all
in this location for DVB-T.

Using a cheap Chinese DVB-T2 reeiver from ebay.
So now the magic
Took a piece of 75 Ohm coax made the magic move and removed something like 12 cm from the shield, then moved it around along the wall
INSIDE and hit a point where reception was error free, bended it a bit and taped it to the wall with double sided tape.
http://panteltje.com/pub/DVB-T2_antenna_IXIMG_0757.JPG
It is probably the iron of the bridge,
And no, the transmitter is miles away.
The magical hotspot is well guarded as you can see,

In article <v56etgd4fv65afprqva0sarcdap39tnpb6@4ax.com>,
jlarkin@highlandsniptechnology.com says...
>
> >Antenna gain can only be had by modifying the antenna pattern.
>
> Or by making the antenna bigger, to intercept more power.
>
>
>

Bigger antennas only work better because they modify the pattern.

Big does not get you anyting unless the antenna is designed to use the
larger size.

Ralph Mowery wrote:

<snip>

> Bigger antennas only work better because they modify the pattern.
>
> Big does not get you anyting unless the antenna is designed to use the
> larger size.

Notwithstanding big business' belief in too-big-too-fail, bigger isn't
better for a microwave bowtie antenna etched on FR-4.

In regards to the OP's question, instead of reflector removal, perhaps,
if your budget permits, you can put two reflective bowties back-to-back?

https://www.ebay.com/itm/123382428258?epid=17026547448

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

On Thu, 6 Jan 2022 12:21:41 -0500, Ralph Mowery
<rmowery42@charter.net> wrote:

>In article <v56etgd4fv65afprqva0sarcdap39tnpb6@4ax.com>,
>jlarkin@highlandsniptechnology.com says...
>>
>> >Antenna gain can only be had by modifying the antenna pattern.
>>
>> Or by making the antenna bigger, to intercept more power.
>>
>>
>>
>
>Bigger antennas only work better because they modify the pattern.
>
> Big does not get you anyting unless the antenna is designed to use the
>larger size.

If a dipole gathers a milliwatt, another dipole some modest distance
away will gather another milliwatt. Seems to me that the powers can be
added without altering the far-field patterns.

--

I yam what I yam - Popeye

On Thu, 06 Jan 2022 07:47:44 -0800, Sid 03 wrote:

> I want to setup a bowtie panel antenna to receive UHF Terrestrial TV
> transmissions in my area. I live between two stations approximately 180
> degrees from each other.
> Is it practical to build and setup a Bow-tie Panel Antenna and leave off
> the reflector to cause the antenna to receive signals front and back ?
> How much does the reflector add to the gain ? -or- is the reflector
> primarily there to prevent the antenna from receiving signal reflected
> off large buildings/mountains from being received by the back of the
> antenna ?
>
> Any help is appreciated.
> Thanks

UHF bowties are easily made; its harder to make the mounts.
Suggest two bowties, one on each side, with two feedlines or
a two-signal combiner.

On 2022-01-06 17:46, Jan Panteltje wrote:

> Antennas and RF fields are a bit of a mystical thing for the not initiated.
> I have a big nice bowtie (was once for TV) and got no usable signal at all
> in this location for DVB-T.
>
> Using a cheap Chinese DVB-T2 reeiver from ebay.
> So now the magic
> Took a piece of 75 Ohm coax made the magic move and removed something like 12 cm from the shield, then moved it around along the wall
> INSIDE and hit a point where reception was error free, bended it a bit and taped it to the wall with double sided tape.
> http://panteltje.com/pub/DVB-T2_antenna_IXIMG_0757.JPG
> It is probably the iron of the bridge,
> And no, the transmitter is miles away.
> The magical hotspot is well guarded as you can see,
>
>

Your action reminds me of Mr Bean's TV aerial:
<https://www.youtube.com/watch?v=Sm3_qEMTdc4&ab_channel=MrBean>

Arie

In article <om9etg5bfjcn9ngm3piu4o1q1324tlanj8@4ax.com>,
jlarkin@highlandsniptechnology.com says...
>
> If a dipole gathers a milliwatt, another dipole some modest distance
> away will gather another milliwatt. Seems to me that the powers can be
> added without altering the far-field patterns.
>
>
>
>

That is true about gain if the spacing and impedance matching are
correct, but the pattern still changes. If the dipoles are too close or
too far apart the phasing is not correct and the signals cancel.
Instead of gain, the pattern breaks up and you may get no signal at all
or a very small signal. They still modify the pattern in some way.

If and only if the spacing is correct two dipoles will double the
signal, not counting on a small loss of interconnecting cables . To
double that you need 4 dipoles for 8, to double that you need 16 dipoles
all phased correctly. With each set of dipoles the beam will narrow so
you have to aim the antenna closer to the station.

On Thursday, January 6, 2022 at 12:38:05 PM UTC-6, Arie de Muijnck wrote:
> On 2022-01-06 17:46, Jan Panteltje wrote:
>
> > Antennas and RF fields are a bit of a mystical thing for the not initiated.
> > I have a big nice bowtie (was once for TV) and got no usable signal at all
> > in this location for DVB-T.
> >
> > Using a cheap Chinese DVB-T2 reeiver from ebay.
> > So now the magic
> > Took a piece of 75 Ohm coax made the magic move and removed something like 12 cm from the shield, then moved it around along the wall
> > INSIDE and hit a point where reception was error free, bended it a bit and taped it to the wall with double sided tape.
> > http://panteltje.com/pub/DVB-T2_antenna_IXIMG_0757.JPG
> > It is probably the iron of the bridge,
> > And no, the transmitter is miles away.
> > The magical hotspot is well guarded as you can see,
> >
> >
> Your action reminds me of Mr Bean's TV aerial:
> <https://www.youtube.com/watch?v=Sm3_qEMTdc4&ab_channel=MrBean>
>
>
> Arie

I see a lot of articles where combiners are mentioned, but I find it hard to find good information on the subject.
From what I have read if the two antennas are not combined correctly the signal received from one antenna is simply radiated out by the 2nd antenna.
Some splitters are advertised as combiners and other websites caution against using splitters/combiners are combiners.
Can I get some clarification on the subject ? maybe some links to info on the subject, where to buy one, how to build one ?
Thanks

In article <d2255b5c-a796-4ed2-bafb-800ed2bebe04n@googlegroups.com>,
Sid 03 <sidwelle@gmail.com> wrote:

>I see a lot of articles where combiners are mentioned, but I find it hard to find good information on the subject.
>From what I have read if the two antennas are not combined correctly the signal received from one antenna is simply
>radiated out by the 2nd antenna.

Some power is _always_ radiated out by the antenna. In fact, even
with a single antenna, at least 50% of the power which reaches the
antenna from the transmitter, is re-radiated by the antenna. If the
antenna system is mismatched to the feedline and load, even more of
the power will reflect from the mismatch point and re-radiated.

What's important, in the case of a "stacked" antenna pair, is that the
signals from the two antennas reach the combining point in the proper
phase. This helps minimize the mismatch and thus the amount of "lost"
power.

The worst case is if the two signals reach the combiner 180 degrees
out of phase, and cancel at the combining point. You'll get no power
into your TV or tuner, and everything will be re-radiated (or lost as
heat into the cables' resistance).

>Some splitters are advertised as combiners and other websites caution against using splitters/combiners are combiners.
>Can I get some clarification on the subject ? maybe some links to info on the subject, where to buy one, how to build one ?

https://www.americanradiohistory.com/Archive-All-Audio/Audio-Magazine.htm
has an excellent archive of PDFs of the late, lamented Audio Magazine.
I subscribed to this quite steadily from my college years in the
1970s until they folded/merged (into High Fidelity Magainze, I think).

What I found, looking back, is a very nice five-part series of
articles on FM antennas, feedlines, preamplifiers, and distribution
systems, by M.J. Salvati, in the January - April issues in 1978 and
the January issue in 1979.

This was followed up by the article I had remembered reading when it
first appeared - "Kill FM interference with two antennas", by Richard
Modafferi, in the January 1980 issue.

Although the specific equipment models described in these six articles
are surely all obsolete by now, the information and knowledge is not -
I gave them a quick skim and they're a great read.

On Thu, 6 Jan 2022 14:13:52 -0500, Ralph Mowery
<rmowery42@charter.net> wrote:

>In article <om9etg5bfjcn9ngm3piu4o1q1324tlanj8@4ax.com>,
>jlarkin@highlandsniptechnology.com says...
>>
>> If a dipole gathers a milliwatt, another dipole some modest distance
>> away will gather another milliwatt. Seems to me that the powers can be
>> added without altering the far-field patterns.
>>
>>
>>
>>
>
>That is true about gain if the spacing and impedance matching are
>correct, but the pattern still changes. If the dipoles are too close or
>too far apart the phasing is not correct and the signals cancel.
>Instead of gain, the pattern breaks up and you may get no signal at all
>or a very small signal. They still modify the pattern in some way.
>
>If and only if the spacing is correct two dipoles will double the
>signal, not counting on a small loss of interconnecting cables . To
>double that you need 4 dipoles for 8, to double that you need 16 dipoles
>all phased correctly. With each set of dipoles the beam will narrow so
>you have to aim the antenna closer to the station.

I think signals from multiple dipoles can be combined without altering
the far-field pattern. I can think of several ways to do that.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

In article <e1metglue8alf2jalkt3nm3f7at3lmb3kp@4ax.com>,
jlarkin@highland_atwork_technology.com says...
>
> I think signals from multiple dipoles can be combined without altering
> the far-field pattern. I can think of several ways to do that.
>
>
>

Then you have exceeded the laws of antennas.

Care to tell a way to do that in any prctical antenna ?

jla...@highlandsniptechnology.com wrote:
===================================
>
> >
> >Antenna gain can only be had by modifying the antenna pattern.
>
> Or by making the antenna bigger, to intercept more power.
>

** Both remarks are ambiguous as written.

The first can be reworded as
" for a given ( VHF / UHF ) antenna, increased forward gain = more directivity".

The second can be restated as :
" an antenna array has more forward gain than a single unit "

Simples.

....... Phil

On Thu, 6 Jan 2022 16:42:26 -0500, Ralph Mowery
<rmowery42@charter.net> wrote:

>In article <e1metglue8alf2jalkt3nm3f7at3lmb3kp@4ax.com>,
>jlarkin@highland_atwork_technology.com says...
>>
>> I think signals from multiple dipoles can be combined without altering
>> the far-field pattern. I can think of several ways to do that.
>>
>>
>>
>
>Then you have exceeded the laws of antennas.
>
>
>Care to tell a way to do that in any prctical antenna ?

It's widely done in radar systems. It's called spoiling the beam.
This is typically done to the transmit beam, so multiple overlapping
receive beams can be used per TX pulse.

All it takes is some random detuning of the drive phases at the
various elements.

Joe Gwinn

In article <d2setgldhnfr1v7h31h9gl61jimta3otfi@4ax.com>,
joegwinn@comcast.net says...
> > I think signals from multiple dipoles can be combined without altering
> >> the far-field pattern. I can think of several ways to do that.
> >>
> >>
> >>
> >
> >Then you have exceeded the laws of antennas.
> >
> >
> >Care to tell a way to do that in any prctical antenna ?
>
> It's widely done in radar systems. It's called spoiling the beam.
> This is typically done to the transmit beam, so multiple overlapping
> receive beams can be used per TX pulse.
>
> All it takes is some random detuning of the drive phases at the
> various elements.
>
> Joe Gwinn
>
>

The antenna uses around 1000 to 2000 dipoles. The beam width is about 1
or 2 degrees. The antennas are phased electrically so you sweep that
small segment over a larger area. It replaces the mechanical need to
rotate the whole antenna.

So with the beam width being so small instead of 180 degrees of a dipole
you have modified the pattern of a single dipole.

John Larkin wrote:
===============
>
> I think signals from multiple dipoles can be combined without altering
> the far-field pattern. I can think of several ways to do that.
>

** Yep - one type is called a "collinear " antenna.

https://en.wikipedia.org/wiki/Collinear_antenna_array

The one caveat is the "pattern" is only being considered in the horizontal plane.
Standard practice for any broadcast antenna set up.

...... Phil

In article <63ea7b65-0507-4902-b23a-6a30f61c7adan@googlegroups.com>,
pallison49@gmail.com says...
>
> > I think signals from multiple dipoles can be combined without altering
> > the far-field pattern. I can think of several ways to do that.
> >
>
> ** Yep - one type is called a "collinear " antenna.
>
> https://en.wikipedia.org/wiki/Collinear_antenna_array
>
> The one caveat is the "pattern" is only being considered in the horizontal plane.
> Standard practice for any broadcast antenna set up.
>
>
>

The collinear modifies the horizontal patern by taking some signal from
the vertical. Think of a baloon. You press it from the top and bottom
and the horizontal gets larger. If the antenna is high enough stations
close in will often loose most of the signal as the pattern shoots over
the top of lower stations. Been there and done that .

Pattern still modified for gain.

On Thu, 6 Jan 2022 16:42:26 -0500, Ralph Mowery
<rmowery42@charter.net> wrote:

>In article <e1metglue8alf2jalkt3nm3f7at3lmb3kp@4ax.com>,
>jlarkin@highland_atwork_technology.com says...
>>
>> I think signals from multiple dipoles can be combined without altering
>> the far-field pattern. I can think of several ways to do that.
>>
>>
>>
>
>Then you have exceeded the laws of antennas.

Laws of antennas? Or folklore?

>
>
>Care to tell a way to do that in any prctical antenna ?

One obvious way: run a feeder from N antennas to a central point.
There, run each signal into a receiver. Combine the receiver outputs.
The RF phase information is lost.

There's probably a passive way to combine an array of dipoles but keep
the same far-field pattern.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

On Thursday, January 6, 2022 at 7:47:48 AM UTC-8, sidw...@gmail.com wrote:
> I want to setup a bowtie panel antenna to receive UHF Terrestrial TV transmissions in my area. I live between two stations approximately 180 degrees from each other.
> Is it practical to build and setup a Bow-tie Panel Antenna and leave off the reflector to cause the antenna to receive signals front and back ?

Sure; a dipole antenna has a figure-eight reception pattern, you'd be aiming a lobe at each of the
sources.

> How much does the reflector add to the gain ?

Usually, a reflector removes one lobe, replacing it with a stronger 'other' lobe (but
this is all frequency-dependent, the reflector spacing can be important). That'd be 3 dB gain.
There's usually a broad range of acceptable sensitivity for an antenna, the 'extra gain'' isn't crucial.

In article <63ea7b65-0507-4902-b23a-6a30f61c7adan@googlegroups.com>,
pallison49@gmail.com says...
>
> > I think signals from multiple dipoles can be combined without altering
> > the far-field pattern. I can think of several ways to do that.
> >
>
> ** Yep - one type is called a "collinear " antenna.
>
> https://en.wikipedia.org/wiki/Collinear_antenna_array
>
> The one caveat is the "pattern" is only being considered in the horizontal plane.
> Standard practice for any broadcast antenna set up.
>
>
>
>

https://www.everythingrf.com/community/what-is-a-collinear-antenna

The horizontal pattern stays the same, but the vertical pattern changes.

If the antenna is somethat higher or lower than another antenna even
the horizontal pattern will seem to change as one antenna over shoots
the other.

Ralph Mowery wrote:
==================
>
> > > I think signals from multiple dipoles can be combined without altering
> > > the far-field pattern. I can think of several ways to do that.
> > >
> >
> > ** Yep - one type is called a "collinear " antenna.
> >
> > https://en.wikipedia.org/wiki/Collinear_antenna_array
> >
> > The one caveat is the "pattern" is only being considered in the horizontal plane.
> > Standard practice for any broadcast antenna set up.
> >
> >
> The collinear modifies the horizontal patern by taking some signal from
> the vertical.

** Did you read my caveat comment at all ?

> Pattern still modified for gain.

** But not relevant to the original question re BROADCAST reception.

Context, context, context, context !!!!!!.

....... Phil

On Thursday, January 6, 2022 at 1:42:33 PM UTC-8, Ralph Mowery wrote:
> In article <e1metglue8alf2jal...@4ax.com>,
> jlarkin@highland_atwork_technology.com says...
> >
> > I think signals from multiple dipoles can be combined without altering
> > the far-field pattern. I can think of several ways to do that.
> >
> >
> >
> Then you have exceeded the laws of antennas.
>
>
> Care to tell a way to do that in any prctical antenna ?

I think he's talking about a wollenweber array of dipoles, with preamplification
then phase-shifting and combination afterward. That worked with lots of operators
trying combinations, for directing fighter craft against bombers, around (for instance)
Berlin, 1943. The linkage used by wool thread spinners to gather their product
is a 'wool-weaver' which is what the dipole array must have suggested.

Alert operators can do the tuning dynamically (those fighter craft MOVED).

John Larkin wrote:
===============
> >>
> >> I think signals from multiple dipoles can be combined without altering
> >> the far-field pattern. I can think of several ways to do that.
> >>
>> >
> >Then you have exceeded the laws of antennas.
> Laws of antennas? Or folklore?

** Smartarse.

> >Care to tell a way to do that in any prctical antenna ?
>
> One obvious way: run a feeder from N antennas to a central point.
> There, run each signal into a receiver. Combine the receiver outputs.
> The RF phase information is lost.
>
** Loud ring goes off !!
That idea is *outside* the parameters of the question re:

" signals from multiple dipoles can be combined "

> There's probably a passive way to combine an array of dipoles but keep
> the same far-field pattern.

** But JL has no idea nor cares a hoot what it is.

..... Phil