E-field antenna, breakthrough or hoax?

Archived from groups: alt.tv.tech.hdtv (More info?)

E-field antenna, breakthrough or hoax?

e-field antenna links:

http://broadcastengineering.com/ne [...] -20040817/

http://www.pcmag.com/article2/0,1759,1749759,000.asp

http://www.dotcast.com/

http://www.winegard.com/

IB

Archived from groups: alt.tv.tech.hdtv (More info?)

inkyblacks@yahoo.com (inkyblacks@yahoo.com) wrote in alt.tv.tech.hdtv:
> E-field antenna, breakthrough or hoax?

"Ya canna change the laws of physics" -- Scotty

If you have a structure with metal studs, aluminum siding, and aluminum-
backed insulation, you have the nice beginnings of a Faraday cage, and
very little signal will get through.

No amount of electronics that sells for less than $50 will overcome this.

In addition, VHF frequencies need larger antennas, and there just isn't
any easy way around this.

--
Jeff Rife | "I don't have to be Ray Liotta: movie star,
| anymore. I can be Ray Liotta: Maya's boyfriend.
| All I want to do is regular, boring, ordinary
| couple things."
| "Then you, sir, have hit the soul-mate lottery."
| -- Ray Liotta and Nina Van Horn, "Just Shoot Me"

Archived from groups: alt.tv.tech.hdtv (More info?)

On Mon, 23 May 2005 18:40:26 -0400, Jeff Rife <wevsr@nabs.net> wrote:

>inkyblacks@yahoo.com (inkyblacks@yahoo.com) wrote in alt.tv.tech.hdtv:
>> E-field antenna, breakthrough or hoax?
>
>"Ya canna change the laws of physics" -- Scotty
>
>If you have a structure with metal studs, aluminum siding, and aluminum-
>backed insulation, you have the nice beginnings of a Faraday cage, and
>very little signal will get through.

Add "Stucco" installed in the last 50 years to that list..

Modern Stucco installations use a metal mesh backing.
Stucco predating the above period used wood lath as a backing and
shouldn't be a problem.

>No amount of electronics that sells for less than $50 will overcome this.

I would go further than that...

For decent reception one must get the antenna outside the BOX..
(faraday cage.) Top of the attic is a good bet..(but not always)..

>In addition, VHF frequencies need larger antennas, and there just isn't
>any easy way around this.

Fortunately, only a few stations are broadcasting DTV mostly in
upper VHF bands. Unfortunately there is the occasional lower VHF (2
thru 6) DTV channel assignment.

I've have found that the signal from a ordinary UHF yagi
antenna+corner reflector is sufficient for my upper VHF (7 - 13)
requirements. (Note: The corner reflector accounts for most of the
UHF antenna gain.)

If one needs to receive the lower(2-6) VHF band signal, rather than
buy a big old VHF/UHF combo antenna, I suggest constructing one or
more tuned dipoles in the attic and then combining the resulting
output with UHF antenna. see

http://www.wfu.edu/~matthews/misc/dipole.html
http://www.hdtvprimer.com/ANTENNAS/types.html

(use a 300-75 ohm matching transformer+ splitter/combiner).

If one carefully looks at the construction of big combination
VHF/UHF antennas, one will find that they don't offer much more gain
than a simple dipole would at same VHF frequencies.

(Check out Plot D [2nd link] for off freq Yagi performance)

Archived from groups: alt.tv.tech.hdtv (More info?)

On Tue, 24 May 2005 14:04:19 GMT, "FDR"
<_remove_spam_block_rzitka@hotmail.com> wrote:

>
>"Tim Keating" <NotForJunkEmail@directinternet11.com1> wrote in message
>news:ev3691hgrjl66la0fvi0cjusesaenq1j6u@4ax.com...
>> On Mon, 23 May 2005 18:40:26 -0400, Jeff Rife <wevsr@nabs.net> wrote:
>>
>>>inkyblacks@yahoo.com (inkyblacks@yahoo.com) wrote in alt.tv.tech.hdtv:
>>>> E-field antenna, breakthrough or hoax?
>>>
>>>"Ya canna change the laws of physics" -- Scotty
>>>
>>>If you have a structure with metal studs, aluminum siding, and aluminum-
>>>backed insulation, you have the nice beginnings of a Faraday cage, and
>>>very little signal will get through.
>>
>> Add "Stucco" installed in the last 50 years to that list..
>>
>> Modern Stucco installations use a metal mesh backing.
>> Stucco predating the above period used wood lath as a backing and
>> shouldn't be a problem.
>>
>>>No amount of electronics that sells for less than $50 will overcome this.
>>
>> I would go further than that...
>>
>> For decent reception one must get the antenna outside the BOX..
>> (faraday cage.) Top of the attic is a good bet..(but not always)..
>
>Doesn't the "cage" have to be grounded for the effect to work?

No..

Archived from groups: alt.tv.tech.hdtv (More info?)

Tim Keating <NotForJunkEmail@directinternet11.com1> wrote in
news:ev3691hgrjl66la0fvi0cjusesaenq1j6u@4ax.com:

> On Mon, 23 May 2005 18:40:26 -0400, Jeff Rife <wevsr@nabs.net> wrote:
>
>>inkyblacks@yahoo.com (inkyblacks@yahoo.com) wrote in alt.tv.tech.hdtv:
>>> E-field antenna, breakthrough or hoax?
>>
>>"Ya canna change the laws of physics" -- Scotty
>>
>>If you have a structure with metal studs, aluminum siding, and
aluminum-
>>backed insulation, you have the nice beginnings of a Faraday cage, and
>>very little signal will get through.
>
> Add "Stucco" installed in the last 50 years to that list..
>
> Modern Stucco installations use a metal mesh backing.
> Stucco predating the above period used wood lath as a backing and
> shouldn't be a problem.
>
>>No amount of electronics that sells for less than $50 will overcome
this.
>
> I would go further than that...
>
> For decent reception one must get the antenna outside the BOX..
> (faraday cage.) Top of the attic is a good bet..(but not always)..

Roof mounts are always the best and higher is almost always better.
Directional is usually cleaner than non-directional. At UHF, though,
height becomes a trade-off because of feedline losses. You can overcome
that disadvantage with a good-quality mast-mount preamp. In most areas,
a rotor is useful as well. You don't need a huge thing for UHF, just a
decent Yagi or bow-tie reflector.

>>In addition, VHF frequencies need larger antennas, and there just isn't
>>any easy way around this.
>
> Fortunately, only a few stations are broadcasting DTV mostly in
> upper VHF bands. Unfortunately there is the occasional lower VHF (2
> thru 6) DTV channel assignment.
>
> I've have found that the signal from a ordinary UHF yagi
> antenna+corner reflector is sufficient for my upper VHF (7 - 13)
> requirements. (Note: The corner reflector accounts for most of the
> UHF antenna gain.)
>
> If one needs to receive the lower(2-6) VHF band signal, rather than
> buy a big old VHF/UHF combo antenna, I suggest constructing one or
> more tuned dipoles in the attic and then combining the resulting
> output with UHF antenna. see

Unless this is planned very carefully, it's a bad idea. What happens all
too often is that one antenna detunes the other and robs the set of the
signals. Also antennas should be at LEAST a half-wave from other
conducting objects off the ends of the elements and further than that in
the direction of reception.


> http://www.wfu.edu/~matthews/misc/dipole.html
> http://www.hdtvprimer.com/ANTENNAS/types.html

> (use a 300-75 ohm matching transformer+ splitter/combiner).

> If one carefully looks at the construction of big combination
> VHF/UHF antennas, one will find that they don't offer much more gain
> than a simple dipole would at same VHF frequencies.
>
> (Check out Plot D [2nd link] for off freq Yagi performance)

Often true, though a good design can be done in a log-periodic array
that's third-harmonic resonant at UHF. You need more elements, more
closely spaced than for VHF alone, or you need to intersperse UHF
parastitic elements, but the result can actually be OK. I'd take a shot
at designing something if someone was interested in manufacture.


--
Dave Oldridge+
ICQ 1800667

A false witness is worse than no witness at all.
God is an evolutionist.

Archived from groups: alt.tv.tech.hdtv (More info?)

"Tim Keating" <NotForJunkEmail@directinternet11.com1> wrote in message
news:f8d691h6l3hek6b6fft655tc538u1lhogf@4ax.com...
> On Tue, 24 May 2005 14:04:19 GMT, "FDR"
> <_remove_spam_block_rzitka@hotmail.com> wrote:
>
>>
>>"Tim Keating" <NotForJunkEmail@directinternet11.com1> wrote in message
>>news:ev3691hgrjl66la0fvi0cjusesaenq1j6u@4ax.com...
>>> On Mon, 23 May 2005 18:40:26 -0400, Jeff Rife <wevsr@nabs.net> wrote:
>>>
>>>>inkyblacks@yahoo.com (inkyblacks@yahoo.com) wrote in alt.tv.tech.hdtv:
>>>>> E-field antenna, breakthrough or hoax?
>>>>
>>>>"Ya canna change the laws of physics" -- Scotty
>>>>
>>>>If you have a structure with metal studs, aluminum siding, and aluminum-
>>>>backed insulation, you have the nice beginnings of a Faraday cage, and
>>>>very little signal will get through.
>>>
>>> Add "Stucco" installed in the last 50 years to that list..
>>>
>>> Modern Stucco installations use a metal mesh backing.
>>> Stucco predating the above period used wood lath as a backing and
>>> shouldn't be a problem.
>>>
>>>>No amount of electronics that sells for less than $50 will overcome
>>>>this.
>>>
>>> I would go further than that...
>>>
>>> For decent reception one must get the antenna outside the BOX..
>>> (faraday cage.) Top of the attic is a good bet..(but not always)..
>>
>>Doesn't the "cage" have to be grounded for the effect to work?
>
> No..

Have you ever just tried to put mesh around your receiver to see what
happens?

Archived from groups: alt.tv.tech.hdtv (More info?)

"Glenn" <jedi128hatesspam@cox.net> wrote in message
news:LkMke.2868$tp.206@fed1read05...
> Given these two choices, I say hoax.
>
> As it relates to digital TV, amplifiers do no good. A digital signal is
> either "on" or "off", either "present" or "absent". You will either
> receive a great picture or none at all. A yagi or bow tie antenna,
> mounted up high on the roof line that faces the transmitter is about as
> good as it gets. Many folks have good luck with indoor antennas like the
> silver sensor (I fit in this group luckily) mounted indoors or in the
> attic space.

I would not say that amplifiers do no good.

I have had two identical Philips indoor "rabbit ears/loop" antennas, one
amp'd one not.

The amp'd antenna receives all local stations without being moved - the
unamped one needed to be rotated slightly to receive some stations.

While not exactly a miracle, the amp did do some good.

Archived from groups: alt.tv.tech.hdtv (More info?)

Glenn (jedi128hatesspam@cox.net) wrote in alt.tv.tech.hdtv:
> Depends on whether you are receiving analog signals or digital, and UHF or
> VHF. For VHF those rabbit ears are no good. They are okay for UHF only.
> Where I live, the signals are all VHF and all digital.

You have your "U" and "V" mixed up, because no city has all their digital
channels on VHF...in fact, most digital channels are on UHF.

Rabbit ears are only for VHF (channels 2-13)...the round circle with them is
the UHF (channels 14-69) antenna.

--
Jeff Rife | "Hey, dogs guard.
| Cats watch...and judge."
|
| -- Salem the Cat

Archived from groups: alt.tv.tech.hdtv (More info?)

In article <mC7le.6602$tp.2475@fed1read05>,
"Glenn" <jedi128hatesspam@cox.net> writes:
>
> Depends on whether you are receiving analog signals or digital, and UHF or
> VHF. For VHF those rabbit ears are no good.
>
The TV rabbit ears work 'okay' for VHF, but have very bad characteristics
for UHF.

>
> Where I live, the signals are all VHF and all digital. The silver sensor
> type works well here. A bow-tie or "yagi" is good, too.
>
Few (if any) cities have ALL VHF for all of the digital channels...
A bow-tie (even indoor) is a good choice for UHF. This, of course,
depends upon the signal environment.


>
> An amplifier
> cannot create a digital signal.
>
An amplifier can improve the reception by providing better characteristics
than the normal TV front end and also potentially provide much better
matching for the antenna/TV front end.

>
> It is either there or it is not there.
>
Actually, a digital signal can be 'very good/perfect', it can have
periodic dropouts or can be altogether unwatchable. Using an appropriate
antenna with (maybe) a preamp and other sundry 'novelty items', the signal
can often (not always) be improved.


>
>> With an analog signal, where the noise can hinder the tuner's ability to
> sort out the chaff from the good signal and amplifier may help, but IMO it
> does nothing for a digital signal.
>
Actually, given the same circumstances, when an analog signal will be
improved, it is very likely that the digital signal will also be improved.

Remember: 'digitally' modulated signals still follow the same propagation
and other rules that the 'analog' modulated signals do.

John

Archived from groups: alt.tv.tech.hdtv (More info?)

In article <vprh91t1om1c59cnebndc730e4mkfe125c@4ax.com> Hermango
<hermango.kill_spam.@hotmail.com> writes:

>"FDR" <_remove_spam_block_rzitka@hotmail.com> wrotd:

>>>
>>> For decent reception one must get the antenna outside the BOX..
>>> (faraday cage.) Top of the attic is a good bet..(but not always)..

>>Doesn't the "cage" have to be grounded for the effect to work?

> No. Back in the 1960's I was stationed at an Air Force radar station
>that had a huge radar that operated down around 500 Mhz. It put out 11 megawatt
>pulses that got into everything! I ran the base theater and when the radar was
>running it was close to impossible to watch a movie. I had a faraday cage
>constructed out of wood framing with standard brass screen wire. All I had to
>do was put the cage around the projector, I didn't have to ground it. It had a
>door I could open to load the film and start/stop the projector. We did the
>same sort of thing with some hi -fi gear we had.

> FYI, this radar used a tube called an Amplitron, which had a 35KV plate
>voltage at 100 amps! The waveguide cross-section was about the size of the top
>of my desk! The antenna had 5 100HP electric motors to turn it.

For many years residents of the small town of Dana, Indiana were similarly
"RF-Terrorized" by the only land-based LORAN-C navigational station. The
ingress radiation was so strong that residents within 10 miles of the
50-megawatt pulse transmitter had to have RF chokes installed in their
phones just to be able to hear the other party. OTA TV-viewing was almost
impossible. Within 1 mile of the station you could get RF burns just from
touching wire fences. Within that same 1 mile radius flourescent lights
would glow at full brilliance while still in their carton.