OTA Antenna - trying to get smarter
 

Okay, I think I've figured out what my future is going to be in
regards to what VHF/UHF Stations I need to plan to get reception on.

Similarly, via tvFool and so forth, I have all sorts of neat technical
numbers that get into specifics on each channel.

Two part question:

Part I:

I figure that the very old fashioned technique of two people shouting
"better...worse" won't cut it except through pure luck.

Question: What (inexpensive?) hardware is recommend for measuring
reception signal strength?

Intent is to optimize one's OTA antenna installation & pointing,
preferably without getting my wife frustrated as my helper (ie, less
guesswork). I'm also not sure if this is merely a simple S:N "signal
strength" issue or something more...ie, minimizing dropped packets?


Part II:

Next, the tvFool report spreadsheet appears to use -100dB as their
rule of thumb (cutoff criteria) between a 'red' reception zone and
their 'gray' reception zone. Obviously, actual reception depends on a
lot of factors.

Q2) How many -dB of signal should I be looking to design to in order
to have a reasonably good confidence in getting reliable reception?

Obviously, the lower the -dB number is, the better, but what seems to
be missing from the guidance I've found to date is anyone who clearly
says "you need to have at least -XX dB of digital signal, so if
Station A is -YY, then you need an antenna system with at least (XX-
YY=ZZ) dB of gain...or however this math should work.

I'm fundimentally looking at is my parent's installation, where they
fortunately don't have any significant clutter or multipath
problems...they're simply in the boonies. They have a small cluster
of stations at around -77dB (yellow reception zone at TVfool), and
then a big cluster of desired stations at -120dB (gray zone). What
magnitude of dB gain antenna should be expected to do the job for
each?

Mom still hasn't yet sent me a digital photo of their current antenna
for me to count elements, so I'm still waiting on that piece of data.


-hh

OTA Antenna - trying to get smarter
 

On Thu, 24 Jan 2008 14:39:54 -0800 (PST), -hh
wrote:

Okay, I think I've figured out what my future is going to be in
regards to what VHF/UHF Stations I need to plan to get reception on.

Similarly, via tvFool and so forth, I have all sorts of neat technical
numbers that get into specifics on each channel.

Two part question:

Part I:

I figure that the very old fashioned technique of two people shouting
"better...worse" won't cut it except through pure luck.

Question: What (inexpensive?) hardware is recommend for measuring
reception signal strength?

Probably an HDTV! Maybe one of these $89 PC cards will do it,
actually. But most TVs have some kind of signal strength indicator,
my Sony has that (once I found it!), a DB number, and packet error
count. Does not show multipath or any other analog numbers, and for
that matter, all it knows is the amplified signal from my powered
antenna.

Intent is to optimize one's OTA antenna installation & pointing,
preferably without getting my wife frustrated as my helper (ie, less
guesswork). I'm also not sure if this is merely a simple S:N "signal
strength" issue or something more...ie, minimizing dropped packets?

Mine seems to vary over time, but then I have almost nothing *but*
multipath in my signal! But some days, it's a lot better if I turn
the antenna this way rather than that - or put a pie plate on one
side.

J.

OTA Antenna - trying to get smarter
 

-hh wrote:

Part I:

I figure that the very old fashioned technique of two people shouting
"better...worse" won't cut it except through pure luck.

Question: What (inexpensive?) hardware is recommend for measuring
reception signal strength?

Intent is to optimize one's OTA antenna installation & pointing,
preferably without getting my wife frustrated as my helper (ie, less
guesswork). I'm also not sure if this is merely a simple S:N "signal
strength" issue or something more...ie, minimizing dropped packets?

All ATSC tuners that I have seen have a signal strength meter of some
sort. Some go from 0 to 100, others such as the Samsungs use 1 to 10
bars. If you know the actual digital broadcast channel, even if you
don't get a lock on the station, you can enter the channel in the tuner
and see what the signal strength is for the station. For a weak or
multipath signal, the meter is likely to bounce around, so this can
require some patience and a lot of adjustments of the antenna.


Part II:

Next, the tvFool report spreadsheet appears to use -100dB as their
rule of thumb (cutoff criteria) between a 'red' reception zone and
their 'gray' reception zone. Obviously, actual reception depends on a
lot of factors.

Q2) How many -dB of signal should I be looking to design to in order
to have a reasonably good confidence in getting reliable reception?

Obviously, the lower the -dB number is, the better, but what seems to
be missing from the guidance I've found to date is anyone who clearly
says "you need to have at least -XX dB of digital signal, so if
Station A is -YY, then you need an antenna system with at least (XX-
YY=ZZ) dB of gain...or however this math should work.

I'm fundimentally looking at is my parent's installation, where they
fortunately don't have any significant clutter or multipath
problems...they're simply in the boonies. They have a small cluster
of stations at around -77dB (yellow reception zone at TVfool), and
then a big cluster of desired stations at -120dB (gray zone). What
magnitude of dB gain antenna should be expected to do the job for
each?

Mom still hasn't yet sent me a digital photo of their current antenna
for me to count elements, so I'm still waiting on that piece of data.

-120 dBm on tvfool.com is a weak signal. How far away are those
desired stations? Those stations are likely to require a deep fringe
setup. If you post the zip code, I can provide some antenna advice. You
need to look at the UHF part of your parent's antenna as well.

Alan F

OTA Antenna - trying to get smarter
 

|
|Q2) How many -dB of signal should I be looking to design to in order

I don't know the actual cutoff point, and it could vary based on the
tuner design. A friend who is a retired EE claims ATSC reception is
more a signal to noise ratio issue rather than looking for a strong
signal, but there is a point when a low quiet signal won't do the job.

Steve

OTA Antenna - trying to get smarter
 

Alan F wrote:

All ATSC tuners that I have seen have a signal
strength meter of some sort. Some go from 0 to
100, others such as the Samsungs use 1 to 10 bars.

Are those "bars" any more reliable than the number of bars displayed on
a cell phone to show *its* signal strength?

OTA Antenna - trying to get smarter
 

On Jan 25, 10:04*am, (Cinder Lane) wrote:

Are those "bars" any more reliable than the number of bars displayed on
a cell phone to show *its* signal strength?

Sometimes, I will get a high reading of like 80% and have brief
blackouts-- most tuners need 20% to function, but only when the wind
is blustery. A minor antenna adjustment can correct this, so I usually
switch tuners unless I'm running off my DVR.

OTA Antenna - trying to get smarter
 

In article Steven Stone writes:
|
|Q2) How many -dB of signal should I be looking to design to in order

I don't know the actual cutoff point, and it could vary based on the
tuner design. A friend who is a retired EE claims ATSC reception is
more a signal to noise ratio issue rather than looking for a strong
signal, but there is a point when a low quiet signal won't do the job.

Both ATSC and NTSC reception performance is a function of the signal
to noise ratio.

A "low quiet signal" still has a signal/noise -- there is the base
noise level in the universe, the thermal noise from the environment,
and the electronic/thermal noise in the first stages of the receiver.
(Look up "noise figure".)

Either depends on s/n for results. NTSC, requires a substantially
higher s/n than ATSC to get a reasonable picture.

Alan

OTA Antenna - trying to get smarter
 

Alan F wrote:
-hh wrote:
Part I:
Intent is to optimize one's OTA antenna installation & pointing,
preferably without getting my wife frustrated as my helper (ie, less
guesswork). *I'm also not sure if this is merely a simple S:N "signal
strength" issue or something more...ie, minimizing dropped packets?

* All ATSC tuners that I have seen have a signal strength meter of some
sort. Some go from 0 to 100, others such as the Samsungs use 1 to 10
bars. If you know the actual digital broadcast channel, even if you
don't get a lock on the station, you can enter the channel in the tuner
and see what the signal strength is for the station. For a weak or
multipath signal, the meter is likely to bounce around, so this can
require some patience and a lot of adjustments of the antenna.

It essentially sounds then like just a generic ATSC tuner box should
be sufficient; no particular need to buy an extra widget just to
measure signal, as it is duplicative.

(sidbar to JXStern: an HDTV for myself is inevitable, but my interim
is for something small & light that I can carry from my house over to
my Parent's house to get them set up with ATSC...such as a tuner box).


Part II:
[My parent's] have a small cluster
of stations at around -77dB (yellow reception zone at TVfool), and
then a big cluster of desired stations at -120dB (gray zone). *What
magnitude of dB gain antenna should be expected to do the job for
each?

* -120 dBm on tvfool.com is a weak signal. How far away are those
desired stations? Those stations are likely to require a deep fringe
setup. If you post the zip code, I can provide some antenna advice.

Their Zip is 19963, but they're around 5 miles from the town center,
so also plug in "Bay Avenue" for the street and 35ft height.

The -120dB DT stations I was referring to are ~78 miles to their North
(15 degrees magnetic), coming from Philadelphia.

You need to look at the UHF part of your parent's antenna as well.

Agreed. I don't expect it to be too much of a problem, as a good deal
of the NTSC that they currently receive is UHF (16, 29, 47, 64), so
they already have a decent number of UHF elements (an exact count is
still not yet known to me...its on my 'To Do' list for my next trip
to see them).

For new antenna options (their existing is getting old) and post-2009,
I've looked into the issue of "low VHF" for antenna replacement
options, and I've found that WPVI (ABC) is currently transmitting DT
on 61, but after 2009 is planning on moving their DT back down to VHF
6. As such, I'll need to make sure that any future antenna continue
to cover this VHF frequency too.


-hh

OTA Antenna - trying to get smarter
 

-hh wrote:
Part II:
[My parent's] have a small cluster
of stations at around -77dB (yellow reception zone at TVfool), and
then a big cluster of desired stations at -120dB (gray zone). What
magnitude of dB gain antenna should be expected to do the job for
each?
-120 dBm on tvfool.com is a weak signal. How far away are those
desired stations? Those stations are likely to require a deep fringe
setup. If you post the zip code, I can provide some antenna advice.

Their Zip is 19963, but they're around 5 miles from the town center,
so also plug in "Bay Avenue" for the street and 35ft height.

The -120dB DT stations I was referring to are ~78 miles to their North
(15 degrees magnetic), coming from Philadelphia.

You need to look at the UHF part of your parent's antenna as well.

Agreed. I don't expect it to be too much of a problem, as a good deal
of the NTSC that they currently receive is UHF (16, 29, 47, 64), so
they already have a decent number of UHF elements (an exact count is
still not yet known to me...its on my 'To Do' list for my next trip
to see them).

For new antenna options (their existing is getting old) and post-2009,
I've looked into the issue of "low VHF" for antenna replacement
options, and I've found that WPVI (ABC) is currently transmitting DT
on 61, but after 2009 is planning on moving their DT back down to VHF
6. As such, I'll need to make sure that any future antenna continue
to cover this VHF frequency too.

That zip code is definitely at deep fringe range from the Philadelphia
stations at ~78 miles and Baltimore at ~73 miles. There are 3 Salisbury,
MD stations to the south for PBS, CBS, ABC. There will be 2 VHF stations
in Philly after the analog shutdown: as you listed, WPVI-DT ABC 6 on low
VHF 6 and WHYY-DT PBS 12 on VHF 12. The rest will stay on UHF. BTW,
WBAL-DT NBC 11 and WJZ-DT CBS 13 in Baltimore will switch to VHF 11 and
13 in February, 2009 if you parents can get the Baltimore stations with
a rotator.

But because of WPVI-DT, your parents will need full VHF and UHF
antenna coverage. If their current antenna works, I would give that a
try to see what digital stations you can get with it. If the antenna has
been up there for years, the co-axial cable may be RG-59 or even twin
lead. If so, I would replace the cable with quad shielded RG-6 before
replacing the antenna if you get most of the digital stations. RG-59 has
measurably higher loss per foot for the high UHF channels than RG-6, so
RG-6 is strongly recommended. Even if the cable is RG-6, if it has been
exposed to the elements for years, check the cable for cracks and
connections for corrosion. Moisture can seep in through the cracks and
act as an attenuator.

Does your parents antenna setup have a pre-amp?

If you replace the antenna, the optimum approach for deep fringe range
setups is considered to be to use separate antennas for VHF and UHF. Any
combined VHF/UHF antenna has design compromises to cover the 3 very
different bands. A common deep fringe setup is to use the AntennasDirect
91-XG for UHF (http://www.hdtvprimer.com/ANTENNAS/XG91.html) and a VHF
only antenna such as a Winegard HD-5030. But if you want to keep it
simpler, then the Winegard HD8200P is considered a excellent deep
fringe, albeit a very large antenna. Reportedly the HD8200P is being
replaced by the HD8200U which can be shipped via UPS as the HD8200P is
too long for UPS.

Good luck,
Alan F

OTA Antenna - trying to get smarter
 

Alan F wrote:

* That zip code is definitely at deep fringe range from the Philadelphia
stations at ~78 miles and Baltimore at ~73 miles. There are 3 Salisbury,
MD stations to the south for PBS, CBS, ABC. There will be 2 VHF stations
in Philly after the analog shutdown: as you listed, WPVI-DT ABC 6 on low
VHF 6 and WHYY-DT PBS 12 on VHF 12. The rest will stay on UHF. BTW,
WBAL-DT NBC 11 and WJZ-DT CBS 13 in Baltimore will switch to VHF 11 and
13 in February, 2009 if you parents can get the Baltimore stations with
a rotator.

There's also an obscure Atlantic City station (PBS?) that they get at
times. I do know that they have a rotor for their existing antenna,
but they're not using it much at all anymore (they're simply making
due with fewer channels). A multi-directional system that eliminates
the need for a rotor would be a 'nice to have', but my understanding
of these is that they require each channel to be individually
filtered, which gets complicated, etc.


* But because of WPVI-DT, your parents will need full VHF and UHF
antenna coverage. If their current antenna works, I would give that a
try to see what digital stations you can get with it.

"Test with current, then adjust" is exactly my plan.

If the antenna has
been up there for years, the co-axial cable may be RG-59 or even twin
lead. If so, I would replace the cable with quad shielded RG-6 before
replacing the antenna if you get most of the digital stations. RG-59 has
measurably higher loss per foot for the high UHF channels than RG-6, so
RG-6 is strongly recommended. Even if the cable is RG-6, if it has been
exposed to the elements for years, check the cable for cracks and
connections for corrosion. Moisture can seep in through the cracks and
act as an attenuator.

Its an old enough installation that it has to be RG-59 (at best).
Replacing the exposed-to-outdoor cable is a no-brainer, but when it
comes to cable that's indoors _and_ downstream of the amplifier, is
there that much of a benefit or not? I'm not sure how easy/hard it
will to replace the wiring inside the house, as I'm not sure of the
cable run - it very well may have been moved to be inside of walls,
etc, over years of renovations.

Does your parents antenna setup have a pre-amp?

I'm almost positive that they have an amplifier somewhere, but I don't
know how physically close it is to the antenna. Obviously, the closer
to the source, the better.



* If you replace the antenna, the optimum approach for deep fringe range
setups is considered to be to use separate antennas for VHF and UHF. Any
combined VHF/UHF antenna has design compromises to cover the 3 very
different bands. A common deep fringe setup is to use the AntennasDirect
91-XG for UHF (http://www.hdtvprimer.com/ANTENNAS/XG91.html) and a VHF
only antenna such as a Winegard HD-5030. But if you want to keep it
simpler, then the Winegard HD8200P is considered a excellent deep
fringe, albeit a very large antenna. Reportedly the HD8200P is being
replaced by the HD8200U which can be shipped via UPS as the HD8200P is
too long for UPS.

Thanks; will keep this in mind. They're waterfront, so I'm also
concerned about wind loads (the current rooftop system has guy wires
to keep it from torquing its mount), although I can see how two
"medium" antennas might be better than one "huge".

Thanks,

-hh

OTA Antenna - trying to get smarter
 

A quick PS:

Just realized that I had an image of my parent's current antenna rig
in the background of a photo from a few months ago.

Here's the crop from that photo, to start to figure out what it is,
via catalog search:


http://www.huntzinger.com/photo/2008...beach-2007.jpg


IIRC, Weingard uses that double-boom arrangement...are they the only
ones?


-hh

OTA Antenna - trying to get smarter
 

I've found that if I mount an antenna off a chimmney or vent pipe the
gases from those sources accelerate oxidation and deterioration of any
metal in the way, including the antenna, reducing reception and
weakening supports.

Steve

OTA Antenna - trying to get smarter
 

-hh wrote:
Alan F wrote:
That zip code is definitely at deep fringe range from the Philadelphia
stations at ~78 miles and Baltimore at ~73 miles. There are 3 Salisbury,
MD stations to the south for PBS, CBS, ABC. There will be 2 VHF stations
in Philly after the analog shutdown: as you listed, WPVI-DT ABC 6 on low
VHF 6 and WHYY-DT PBS 12 on VHF 12. The rest will stay on UHF. BTW,
WBAL-DT NBC 11 and WJZ-DT CBS 13 in Baltimore will switch to VHF 11 and
13 in February, 2009 if you parents can get the Baltimore stations with
a rotator.

There's also an obscure Atlantic City station (PBS?) that they get at
times. I do know that they have a rotor for their existing antenna,
but they're not using it much at all anymore (they're simply making
due with fewer channels). A multi-directional system that eliminates
the need for a rotor would be a 'nice to have', but my understanding
of these is that they require each channel to be individually
filtered, which gets complicated, etc.

A multi-directional antenna setup with filters for 70+ miles can get
rather complicated, expensive, and really requires that person who has
it knows how to maintain or tweak it.

But because of WPVI-DT, your parents will need full VHF and UHF
antenna coverage. If their current antenna works, I would give that a
try to see what digital stations you can get with it.

"Test with current, then adjust" is exactly my plan.

If the antenna has
been up there for years, the co-axial cable may be RG-59 or even twin
lead. If so, I would replace the cable with quad shielded RG-6 before
replacing the antenna if you get most of the digital stations. RG-59 has
measurably higher loss per foot for the high UHF channels than RG-6, so
RG-6 is strongly recommended. Even if the cable is RG-6, if it has been
exposed to the elements for years, check the cable for cracks and
connections for corrosion. Moisture can seep in through the cracks and
act as an attenuator.

Its an old enough installation that it has to be RG-59 (at best).
Replacing the exposed-to-outdoor cable is a no-brainer, but when it
comes to cable that's indoors _and_ downstream of the amplifier, is
there that much of a benefit or not? I'm not sure how easy/hard it
will to replace the wiring inside the house, as I'm not sure of the
cable run - it very well may have been moved to be inside of walls,
etc, over years of renovations.

Does your parents antenna setup have a pre-amp?

I'm almost positive that they have an amplifier somewhere, but I don't
know how physically close it is to the antenna. Obviously, the closer
to the source, the better.

Looking at the antenna photo you provided, your parents antenna
appears to be a Channel Master 3678 Double Boom which a good deep fringe
antenna. Underneath the antenna on the mast is a rectangular black item
which is probably the pre-amp. Then the cylinder further down the mast
is probably the rotator. I would keep this antenna setup if it is not
too corroded. If you can get up there, look at the pre-amp for
corrosion. If it needs to be replaced, the Channel Master 7777 pre-amp
would be a logical choice for their situation.

If the cable is RG-59, you want to replace as much as it as you can.
Although if you can get all of the Philadelphia digital stations and who
knows the Salisbury stations from the backside, you may want to leave it
alone. But as to why replace RG-59, check this website, which is very
useful for antenna info:
http://www.hdtvprimer.com/ISSUES/erecting_antenna.html

Under antenna basics, look at the chart under Tranmission cable titled
Cable loss in dB per 100 feet. RG-59 has 2-4 dB higher loss per 100 ft
at UHF channel 50 than RG-6. RG-11 is still better, but RG-11 is pricey
and so thick as to be hard to bend:
http://www.hdtvprimer.com/ANTENNAS/basics.html.

If you replace the antenna, the optimum approach for deep fringe range
setups is considered to be to use separate antennas for VHF and UHF. Any
combined VHF/UHF antenna has design compromises to cover the 3 very
different bands. A common deep fringe setup is to use the AntennasDirect
91-XG for UHF (http://www.hdtvprimer.com/ANTENNAS/XG91.html) and a VHF
only antenna such as a Winegard HD-5030. But if you want to keep it
simpler, then the Winegard HD8200P is considered a excellent deep
fringe, albeit a very large antenna. Reportedly the HD8200P is being
replaced by the HD8200U which can be shipped via UPS as the HD8200P is
too long for UPS.

Thanks; will keep this in mind. They're waterfront, so I'm also
concerned about wind loads (the current rooftop system has guy wires
to keep it from torquing its mount), although I can see how two
"medium" antennas might be better than one "huge".

The separate antennas for UHF and VHF can require more maintenance and
wind load issues. They may be better off with a single sturdy deep
fringe VHF/UHF antenna setup.

Alan F