Trouble keeping digital signal

[jwgriffen]

I am using a Sensar RV 2500 antenna in a 5th wheel trailer. I have a digital television with its own digital tuner. When I run a scan, depending on the direction of the antenna, I get multiple channels, including network channels from Southwest Michigan and Northwest Indiana. The trouble is I have a perfect picture for a few minutes and then all of a sudden no signal. Then the picture will come back after a few seconds or few minutes. It keeps going back and forth until I give up, move the antenna again and rescan. The problem has occurred with channels from Battle Creek (CBS), Grand Rapids (NBC) and South Bend (NBC). If I aim the antenna toward Lake Michigan I also get stations from Chicago but have the same problem. This problem seems to be worse during daylight hours and not so bad evenings. Any suggestions will be appreciated.

jwgriffen

[Winegard-Mobiletech]

What you are describing is a weak or marginal signal.

You might look to see if the channels you are struggling with are UHF, if they are the Wingman accessory can definitely help.

[jwgriffen]

Thanks for your reply. I initially thought I had a marginal signal too. However, I am in South Haven, Michigan and have been able to get stations as far away as Green Bay, Wisconsin. I was able to keep that station for about 1 hour before the signal just disappeared. I also do have a wingman and I suspect that is why I am able to pick up signal (although not always sufficient) from many stations.

I have the most problem picking up the station from Battle Creek/Kalamazoo which is the closest to my location. Mornings I get network stations from South Bend, Indiana. By mid afternoon I lose them and late afternoon I start to pick up the Grand Rapids, MI stations. Evenings I do get Grand Rapids but the station will last for a while and then start the in and out problem for a while.

I think the location of the sun during the morning and then late afternoon may have something to do with which ones I can get but I remain puzzled with the marginal signal problem that comes and goes.

John Griffen

[KNP 2516]

I don't want to sound negative here, but RV antenna's are poor performers. If you have your camper in a permanent location, you might want to invest in a better - more permanent antenna.

Late morning and early evening, you get a phenomena called Tropospheric ducting.
http://www.angelfire.com/sc/scannerpost/tropo.html

You cannot rely on Tropospheric Ducting to get good television reception. it comes and goes.

Basically what that tells us is that you need a better antenna that is capable or receiving both UHF and VHF signals.

Simple things like buildings 4 or more stories tall, trees, hills, airplanes, migrations of birds, swarms of bugs, rain, snow, etc can all affect your reception.

[winegard]

Good afternoon John -

The Sensar should have no problem pulling in signals from that distance and is an excellent performer working for millions or RV'ers across the country. The Wingman has improved that performance on UHF greatly has of course become important after this transition.

However, what KNP 2516 states about buildings and other obstructions is corret and will greatly vary the signal coming to your antenna. I am going to send your situation to an engineer we know in the area for further review. Hang tight!

[jwgriffen]

Thanks KNP2516 for the information re tropospheric ducting. Whether or not that explains some of my distant station receptions it is pretty interesting and does make sense. If I continue to have the come and go problems for the next several weeks I will look into your suggestion of a permanent antenna best suited for my needs. In the meantime I am getting pretty good at knowing which direction to point the antenna at any given time of the day to have at least a chance of getting a particular network station!

For now at Winegard's request I am "hanging tight" and will await their further information.

[KNP 2516]

Due to the fact that your camper probably isn't all that long, there isn't much advice I can give you - as per a pre amplifier.

But maybe Mr Winegard can suggest a good mid level pre amplifier for you.

I have the habit of always wanting the biggest one you can buy.

I will only say two things on this subject and then I will give it a rest.

If a Wingman antenna took care of 100% of all consumers situations, then I wouldn't need to have spent the money for a 8200U Winegard antenna. Without going too deeply into the subject and saying something that can be disputed with someone with a better education than mine. My opinion on antenna's is that the more elements a antenna has, the more gain it has, due to the fact that when you add elements you also add surface area.

In the analog days there were two effectively transmitters for the TV
station.
A transmitter for the video and a transmitter for the audio.
The video transmitter was Amplitude Modulation see
http://en.wikipedia.org/wiki/NTSC

The audio was FM at a much lower power.

The reason that the video was a higher power is that AM is more susceptible
to noise requiring a stronger signal at the receive and a higher power
output of the video transmitter

http://en.wikipedia.org/wiki/Television_station
"In North America, full-power stations on band I (channels 2 to 6) are
generally limited to 100 kW analog video (VSB) and 10 kW analog audio (FM),
or 20 kW digital (8VSB) ERP. Stations on band III (channels 7 to 13) can go
up by 5dB(W) to 316 kW video, 31.6 kW audio, or 63.2 kW digital. Low-VHF
stations are often subject to long-distance reception just as with FM.
There are no stations on channel 1.

UHF, by comparison, has a much shorter wavelength, and thus requires a
shorter antenna, but also higher power. North American stations can go up
to 5000 kW ERP for video and 500 kW audio, or 1000 kW digital. Low channels
travel further than high ones at the same power, but UHF does not suffer
from as much electromagnetic interference and background "noise" as VHF,
making it much more desirable for TV. Despite this, in the U.S., the FCC is
taking another large portion of this band (channels 52 to 69) away, in
contrast to the rest of the world, which has been taking VHF instead. This
means that some stations left on VHF will be harder to receive after the
analog shutdown. Since at least 1974, there are no stations on channel 37
in North America for radioastronomy purposes."

UHF communications are more "line of sight" communications than lower
frequency VHF.
It is sort a like having a sound vs a light. If you make sound it radiates
in all directions, around buildings, through walls, down into holes
(valley).
Shining a light does not go around corners or through walls and if it is a
pinpoint light it doesn't go down into the valleys.

The earth is round and eventually the beam of light, UHF tv the beam will
no longer touch the earth but go up into the sky.
Here is some information concerning line of sight and how it effects TV
http://www.softwright.com/faq/support/e ... alues.html

http://www.ian-ko.com/ET_Surface/UserGu ... ussion.htm

http://en.wikipedia.org/wiki/Horizon

The height of the transmitting antenna is factored into the power output of
the TV station.
The power output for TV & FM is rated in ERP (Effective Radiated Power)
There are a number of factors the go into this calculation.
Several Key items are:
Height of Antenna. listed both as HAAT (Height Above Average Terrain) and
AMSL (Height Above Mean Sea Level)

Gain of antenna: Just like your receiving antenna has gain in db so does
the transmitter.
Remember 3db gain is equivalent to doubling the output power. or 1/2 the
electric consumption expense

About amplifiers:
The best is to only use a amplifier as close to the antenna as possible
with the highest gain in the area that you are interested in receiving
(UHF) with the lowest possible noise and both at a reasonable cost.

The KEY is that you want a relative "good" level of input at your receiver
(TV) with the minimum noise.
A mast mounted amplifier (doesn't matter if it is called a amplifier or
preamplifier) is the best when you are in a remote area.
In theory it is best if you amplify a "good" signal to a higher level than
a "poor noisy" signal to a higher level. When you start out with crap and
amplify it you just end up with more crap.
All cable has loss and the higher up that you go in frequency (VHF to UHF)
the more loss that the cable has.
If you start with a low level signal at the antenna and then butt it into
coax cable you are going to have less come out at the end than went into it
from the antenna. The amount of loss depends upon a number of factors,
cable type and cable length are the two most important. Cable is rated in
db loss per 100' at X MHz (frequency). RG-6 cable is the cable most used
in TV use. Like all things there is good RG6 and not so good. Belden
1829AC Coax - Series 6 has a loss of 4db/100 feet at 500 MHz (TV Channel
18)
Channel 32 is 580 MHz Channel 52 is 700 MHz a 5 db loss At TV channel 2
the cable would have a loss of 1.4db. So at channel 18 you loose more than
1/2 the power in 100' of cable between the antenna and the TV.

Signal Reception 101
Example
Let's say that the average estimated signal level from WSBT in your area is -41db.
That calculates to .00008 millawatts (000.000.08 watts) of power per meter.

There are three parts to a antenna.
1. Director
2. Radiator (the element/s that the wire connect to)
3. Reflector

The Directors and Reflectors are generally grounded either directly or
through a tuning wire.

With a -41db input and a receiver that can pick up a signal to -55db (most
are in this range, but manufactures do not publish any specifications, you
have 14db of safety factor for all atmospheric signal reduction, trees and
other factors.
You should get a good picture (analog).
If you have a amplifier with 18 db of gain that is like the TV station
increasing their power 64 times (every 3db of gain is equal to doubling the
power). That now gives you 22db of margin, that is great... However all
amplifiers amplify everything both the good signal that you want to
hear/see and bad noise from power lines, ignition systems, electric fences,
motor brush noise etc. Amplifiers also generate their own noise. So a
amplifier with a high gain is great but the internally generated noise must
be at the minimum.

So look for a amplifier that has the best gain and the lowest noise figure.

The Winegard AP 8275 is the highest rated amplifier on the market today with the lowest noise figure.

Belden 1829 AC wire has the best rating for most common Quad Shield wire per 100 feet for loss and shielding.

I just spent several hours tonight replacing F type connectors and wire on my antenna system and hooking up a new pre amplifier. The results was that I could receive 1 station that only had a signal level of about 15 to 20% signal, it now has 100% signal level on my Channel Master CM 7000 box.

I also gained 2 channels that all antenna sites and the FCC said I could not receive in my area.

Both are UHF and are to my south west and there is several mountains between the transmitter and my home.

Electronic's 101 says that if the transmitter was 1000 feet above average terrain - not height in feet above sea level, and your antenna was 1000 feet above average terrain, and you were 40 miles away from the transmitter, you could receive their signal. Line of sight. Even though the horizon is only about 26 miles.

Anything more than 40 miles and it is a crap shoot. Sometimes you can get it and sometimes you cant.

Here is the kicker, my antenna is only 18 feet off the ground.

Until I could get everything rounded up and working properly, I was not going to mount a 16 pound antenna on my main roof and I was not going to climb up and down a ladder and go on and off the roof several dozen times until I figured out what all I needed to do to get my antenna system to work properly.

My two story home has a roof height of about 32 feet and a pitch on the front roof of 9/12.

It is very steep! I have been hurt in several serious automobile accidents and have a loss of equilibrium.
The last thing I would want to do is fall off a roof. Nothing is worth damaging your health.

But I will tell you that the $150 I spent for my 8200U antenna and all the grief I went through to get all the parts of the antenna - when there was parts missing in my brand new box and I even spent $18 on top of that for all stainless steel hardware for my antenna was the best money I ever spent.

When you live 68 miles from some of the transmitters and live in Pennsylvania - where the terrain is very challenging for UHF reception, I cannot complain about the digital reception I now have!

Anything less - in antenna and I would still be stuck watching 4 channels.
I PBS, 1 NBC and 1 ABC / Fox