TV antenna troubles

Just wondering if i could get*a bit of advice, just bought the boat and found that there is a tv antenna hidden under the brow.**It has coax and three wires together, a red, a yellow and a black. The coax i can manage. I guess its 110, the antenna is a two inch thick dish about a foot and half in diameter, blue on the bottom, white on the top. Has no markings in regards to make/model. how should i proceed. thanks in advance for any suggestions.

Rip it out and throw away the tv. Actually, our antenna, which is a Shakespeare, has only a coax connected to it. Down below, that coax plugs in to a box with a coax "in from ant" socket. The box has power connections to AC and DC, with a selector switch to choose which power source you wish to use. The box also has a coax "out to tv" socket. Maybe its time to upgrade/replace the antenna so you know for sure what you have and how it is to be connected (instructions are included and simple). They are not particularly expensive.

I don't know if this will help much but on my new to me boat my setup is similar to dwhatty. I have a small dish type antenna forward of the helm. It has I believe a co-axial cable that runs to I think a antenna amplifier in the aft stateroom that is 115v AC powered. A co-axial cable runs from the*amplifier*to the TV. When purchased the boat had an old analog TV. We tossed it and replace with a new flat screen. Hooked the new TV up to the co-axial cable from the amplifier and we get about 10 channels, most in HD.*The amplifier or whatever it is must be powered otherwise without it we get nothing.

A non-moveable dish doesn't sound useful on a boat. Is there any type of receiver box at the other end? A picture might help too.

Sound like what we have. There is a strange looking controller down below that turns it. I'll try and post a photo.

I've figured out how to post an image, this will help i'm sure.

oh yeah, exactly what I have.* here is the controller that is down below and this also shows where the cable comes out.* you will see it goes into a splitter, the one cable continues on through the engine room and provides antenna service to the aft cabin.* Our antenna is stuck all the way to the right (won't rotate left anymore) and that killed our reception so we are replacing it with a long range antenna from Best Buy.*

dwhatty's post was absolutely correct. The antenna that you have was mostly a gimmick when off-air was analog and mostly on VHF channels. Now that off-air TV is ALL digital, and for the most part, ALL on UHF channels you are much better off with rabbit ears on top of the TV. If you do not get a signal with rabbit ears, you are certainly not going to get one with that thing but if you are intent on trying it, I think I do have a couple of controllers that would work, free for the shipping.

rhprop wrote:

dwhatty's post was absolutely correct. The antenna that you have was mostly a gimmick when off-air was analog and mostly on VHF channels. Now that off-air TV is ALL digital, and for the most part, ALL on UHF channels you are much better off with rabbit ears on top of the TV. If you do not get a signal with rabbit ears, you are certainly not going to get one with that thing but if you are intent on trying it, I think I do have a couple of controllers that would work, free for the shipping.

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Oh good point, it is*not a digital antenna!* no wonder we get such crappy reception with it.**

Yeah, *I'd have to go with "rip it out".* I climbing into the "brow" on our boat.

Pineapple Girl wrote:

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Oh good point, it is*not a digital antenna!* no wonder we get such crappy reception with it.**

Yeah, *I'd have to go with "rip it out".* I climbing into the "brow" on our boat.

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There is no such thing as a digital antenna. To pick up digital signals you need an antenna that receives UHF and I would bet even these old ones do. The location of that thing is probably the issue, among other things. Some digital is still being broadcast on VHF just to confuse things so ideally you want an antenna that receives VHF and UHF and if you are on the extreme ends of reception, get one with a signal booster. Chuck

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Capn Chuck wrote:

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Pineapple Girl wrote:

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Oh good point, it is*not a digital antenna!* no wonder we get such crappy reception with it.**

Yeah, *I'd have to go with "rip it out".* I climbing into the "brow" on our boat.

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There is no such thing as a digital antenna. To pick up digital signals you need an antenna that receives UHF and I would bet even these old ones do. The location of that thing is probably the issue, among other things. Some digital is still being broadcast on VHF just to confuse things so ideally you want an antenna that receives VHF and UHF and if you are on the extreme ends of reception, get one with a signal booster. Chuck

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X2. And, if at the extreme ends, as we are, even a booster may not help. Forgetting about the TV and watching nature does help.

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Capn Chuck wrote:

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Pineapple Girl wrote:

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Oh good point, it is*not a digital antenna!* no wonder we get such crappy reception with it.**

Yeah, *I'd have to go with "rip it out".* I climbing into the "brow" on our boat.

*

There is no such thing as a digital antenna. To pick up digital signals you need an antenna that receives UHF and I would bet even these old ones do. The location of that thing is probably the issue, among other things. Some digital is still being broadcast on VHF just to confuse things so ideally you want an antenna that receives VHF and UHF and if you are on the extreme ends of reception, get one with a signal booster. Chuck

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One of my "pet peeves" is antennas advertised as "digital antennas".* You are correct, there is no such thing as a digital antenna.* It's an antenna.

You are also correct that, for some unknown reason, the US government deleted the lower half of the VHF TV spectrum, but kept the upper half plus UHF.* So, the antenna must pick up VHF as well as UHF.

To complicate matters, the FCC allowed stations to keep their old channel designations so what you see on the air as channel 5, may actually be broadcasting on channel 44 (UHF).

And for the suggestion to use "rabbit ears", that's fine for a boat in a slip.* A boat anchored will most likely swing with the tide or current and you will have to continually adjust the rabbit ears (which are direcional).* The saucer shaped antennas you see advertised for boats are omnidirectional which means they pick up signals in all directions


-- Edited by rwidman on Thursday 13th of January 2011 06:00:29 PM

Trash it! *If you are within the B contour of a TV station, with digital TV, if you do not get reception on rabbit ears, you will not get sufficient signal without going to a Yagi antenna mounted outside. These types of antennas were nothing but rabbit ears mounted in an enclosure with a small motor to rotate it.

An amplifier does not improve the receiving efficiency of an antenna. It will only overcome cable losses on the way to your TV.

Omni-directional means that an antenna is equally INEFFECIENT in all directions.*

" There ain't no free lunch "


You can put a Yagi outside with a rotator or you can put rabbit ears inside and get up and move them if the boat moves, or if you are that close to the transmitting tower, just straighten out a clothes hanger and attach to the back of the TV ( thats all an omni-directional antenna is.)


I have spent 40 years in broadcasting, retiring as S.V.P Engineering. You can take my advice or go to Radio Shack

Geez guys, can't I watch some sports or news or mindless sitcoms*while at my slip working on boat projects?** I'm not in the midst of an adventure*/ nature*EVERY time I am at my boat.*

Obviously I don't understand TV signals in the least.* * what is a B contour?* what's a Yagi antenna?* Do TVs even HAVE rabbit ears anymore??* LOL, those are rhetorical questions!*

Anyways, I am installing my new "long range" antenna from best buy this weekend since the old one is busted and I DO like to turn on the idiot box every once in awhile.

Don't get overwhelmed with all of the tech speak. For a boat that moves around, get an omni-directional, a signal booster will help, mount it as high as you can, be sure it will receive UHF and VHF and don't worry about all of the rest. Be careful spending extra money for "long range" antennas, a lot of this is marketing ploys to get your money. Follow my suggestions and you will be fine. Chuck

rhprop wrote:These types of antennas were nothing but rabbit ears mounted in an enclosure with a small motor to rotate it.

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There is no rotation.* It's an antenna that picks up signals from all directions.

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rhprop wrote:

Omni-directional means that an antenna is equally INEFFECIENT in all directions.*

A highly directional antenna pointed directly at the transmitting tower is certainly more efficient than an omnidirectiona antenna and, provided that all the transmitters are in the same general direction, it would be the best antenna for a home, business, etc.

I really don't think anyone wants to get up in the middle of a game or show to readjust the TV antenna as the boat swings on the hook.* That is why I recommend an omnidirectional antenna for a boat.* The major marine antenna companies must agree with me because that's pretty much all they manufacture and sell.

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The contour is the signal strength of the TV station at a given distance from the transmitting antenna. Antennas and their ability to receive signals are very basic and the advertising hype is just that. Antennas are nothing more than wires, or elements, *arranged in a pattern *and no antenna of a given number of elements of a given length will *be no more efficient than another of an equal number of elements, regardless of what the marketing hype says. Any antenna will work better outside than inside and at VHF and UHF ( TV bands ) will work better mounted higher than lower.

If your Best Buy super duper signal booster is not a multi element yagi , you will be just as well off taking the clothes hanger and putting it outside your window.


This is kinda like buying the magic pill on late night tv that will instantly shed 20 pounds or you can diet and exercise.

They sell them because people who do not care to bend a clothes hanger will buy them. The same reason people will spend $100 *or more on a marine VHF antenna when it is nothing but a wire covered with a fiberglass tube. Physics are physics and hype is hype. Some people will buy what works, others will buy the hype.

Capn Chuck wrote:

Don't get overwhelmed with all of the tech speak. For a boat that moves around, get an omni-directional, a signal booster will help, mount it as high as you can, be sure it will receive UHF and VHF and don't worry about all of the rest. Be careful spending extra money for "long range" antennas, a lot of this is marketing ploys to get your money. Follow my suggestions and you will be fine. Chuck

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I agree with everything except the necessity for an amplifier. The amplifier only overcomes the cable losses to the TV , it does not improve the efficiency and unless it is a really big boat or really tall mast, or you are splitting the signal it is not necessary and because the amplifier has a " noise factor " itself, it can actually make the signal worse if the noise contributed is greater than the cable loss that has to be compensated by the amplification in the TV tuner.

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rwidman wrote:

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rhprop wrote:These types of antennas were nothing but rabbit ears mounted in an enclosure with a small motor to rotate it.

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There is no rotation.* It's an antenna that picks up signals from all directions.

The pix of the antenna which is the topic of the original post is a bow tie *in an enclosure *rotated by a small rotor. That is what the pictured controller does. There are omnidirectional disc antennas, which are also junk, but this was not one of them.

I would sure like to be your Best Buy, Radio Shack, West Marine salesman. I would be fixed for life.

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rhprop wrote:


rwidman wrote:

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rhprop wrote:These types of antennas were nothing but rabbit ears mounted in an enclosure with a small motor to rotate it.

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There is no rotation.* It's an antenna that picks up signals from all directions.

The pix of the antenna which is the topic of the original post is a bow tie *in an enclosure *rotated by a small rotor. That is what the pictured controller does. There are omnidirectional disc antennas, which are also junk, but this was not one of them.

I would sure like to be your Best Buy, Radio Shack, West Marine salesman. I would be fixed for life.

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rhprop,

I didn't post on this thread so I could be insulted, I posted to try and help someone with a problem and clear up the misconceptions about "digital" antennas.

I assure you that my Glomex TV antenna has no motor turning a bow tie antenna and neither did the Dantronics UFO that it replaced.* I will also reassure you that either of these antennas perform better than a straight piece of wire (coat hanger).

While some folks may be proud of beating an antenna manufacturer out of a small profit by using a bent coat hanger for an antenna, I have a little more pride in my boat than that.* Perhaps a coat hanger antenna would look fine on a derelict boat tied to a run down dock somewhere.

Perhaps a coat hanger or rabbit ear antenna would work nearly as well as the marine antenna I installed, but as I pointed out above, I don't really want to get up and*climb to the flybridge in the middle of a show to reorient the antenna.* Besides, I wouldn't be able to see the TV while adjusting the antenna so it would be a two person job or I would need an additional TV receiver on the flybridge for monitoring purposes.

I believe your last few posts were not intended to add to the thread, only to start an argument.* You were partially successful, but I am done.* You may carry on if you wish.


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Not wanting to add to any debate or rancor on this subject, I would like to ask a related but different question.

Is there and relatively easy way to test the transmission capabilities of the coax that runs from my masthead antenna to the TV? I believe my old monster 2-foot diameter Shakespeare, which I've already disassembled once to clean out the spiderwebs and bee nests, is less than efficient anymore, and while replacing I would probably want to install a new coax, but pulling it off the mast and un-routing it is a pain. Can I measure gain/loss without any fancy RF - measuring equipment?

ARoss wrote:

Not wanting to add to any debate or rancor on this subject, I would like to ask a related but different question.

Is there and relatively easy way to test the transmission capabilities of the coax that runs from my masthead antenna to the TV? I believe my old monster 2-foot diameter Shakespeare, which I've already disassembled once to clean out the spiderwebs and bee nests, is less than efficient anymore, and while replacing I would probably want to install a new coax, but pulling it off the mast and un-routing it is a pain. Can I measure gain/loss without any fancy RF - measuring equipment?

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The short answer is No, but if the ends have been sealed and the outer insulation does not crack when you bend it, you can be reasonably assured that it is OK. I have coax from the WW11 era that is just as good for the frequencies that it was designed for as it was when new.

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For those of you who can live with an omni-directional antenna, I ran across this on another board:

http://www.boatenna.com/index.htm

basic, no hype, well made, no enclosure to contribute to loss, low loss 300 ohm ribbon cable, actually made for a marine environment and the cost is pretty reasonable for anything with " marine " attached to the name. And no amplifier is necessary or recommended.

I agree with everything except the necessity for an amplifier. The amplifier only overcomes the cable losses to the TV , it does not improve the efficiency and unless it is a really big boat or really tall mast, or you are splitting the signal it is not necessary and because the amplifier has a " noise factor " itself, it can actually make the signal worse if the noise contributed is greater than the cable loss that has to be compensated by the amplification in the TV tuner.

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Not to overwhelm anyone with tech speak, but there are some times when an amplifier can be usefull, so I wouldn't dismiss their use quite so quickly. I can easly see a cable run of over 20 feet on a lot of boats.......Arctic Traveller*
<h2>Signal Amplifiers, Preamplifiers</h2> Many people think that connecting an external amplifier to the antenna will improve the performance of the antenna.This is usually wrong.Receivers always have more gain than is necessary.(The receiver has an Automatic Gain Control circuit, AGC, which will reduce strong signals.The AGC makes all stations the same strength at the demodulator.When you add a preamplifier, the TV receiver lowers its own gain, usually by an equivalent amount.)

Normally the signal to noise ratio will be set by the receivers first transistor.But if an external amplifier is added, the first transistor in that amplifier determines the S/N ratio.(Since the external amp will greatly magnify its own noise as well as the signal, the receivers noise becomes insignificant.)Since there is no reason to think the external amps first transistor is quieter than the receivers first transistor, there is generally no benefit to the S/N ratio from an external amplifier.

But an external amplifier will compensate for signal loss in the cable if the amplifier is mounted at the antenna.Without this amplifier, a weak signal, just above the noise level at the antenna, could sink below the noise level due to loss in the cable, and be useless at the receiver.

RG-6 will lose 1 dB of the signal every 18 feet at channel 52.For a DTV channel, 1 dB can be the difference between dropouts every 15 minutes (probably acceptable) and every 30 seconds (unwatchable).This author recommends a mast-mounted amplifier whenever the cable length exceeds 20 feet.(If you are in a good-signal area or you have no high-numbered UHF channels, you can to an extent ignore this advice.)

The preamplifier should have a gain equal to the loss in the cable (for your highest channel) plus another 10 dB (to keep the receivers first transistor out of the picture).

The amplifier can usually exceed this target by another 10 dB without causing trouble.
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(If you follow the above rule, the cable length becomes irrelevant, and reducing the cable length yields no benefit.)

When figuring the cable loss, be sure to include the loss in any splitters and baluns.If a 2-to-1 splitter were 100% efficient then you would figure a 3 dB loss since each TV gets half of the power.But splitters are usually 80% to 90% efficient.
2-to-1 splitter3.5-4 dB
3-to-1 splitter5-6 dB
4-to-1 splitter7-8 dB
75W-to-300W balun0.2-2 dB(a balun is an adapter)

The antenna and the amplifier both have gains measured in dB, and some people add these two numbers (and then maybe subtract the losses) to find the strength of the signal at the receiver.But this sum is worthless.The net gain in front of the amplifier should always be kept separate from the net gain that follows.

You might not need an amplifier if the antenna is too big.But an amplifier can never make up for an antenna that is too small.


<h2>Receiver noise</h2> Actually there is a reason to think the external amplifier is quieter than the receiver.Long ago designers made an effort to make the TVs first amplifier stage very quiet.But now 90% of homes use cable or satellite boxes (strong sources) and most of the rest are rural homes using antennas that have mast-mounted amplifiers.So the TVs noise is rarely a factor.Some TV makers no longer put any effort into making their sets quiet.

Suppose you live in an apartment 15 miles from the transmitter.Your indoor antenna mostly works, but you are troubled by dropouts and some snow appears on analog channels.Will adding an amplifier right at the TV improve things?Yes, if it is quieter than the TV.Unfortunately TV makers see no reason to publish the noise figures for their receivers.So buying an amplifier for an indoor antenna is a total crapshoot.This author recommends that you try a Channel Master Titan or Spartan amplifier, but make sure you can return it if it is no help.
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Higher is better , so any antenna that can be "up top" is better than mounted down low.