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Old 29-01-2015, 18:53   #16
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Re: Marine TV Antennas

Quote:
Originally Posted by W3GAC View Post
...having both horzonal and vertical elements shouldn't help much since TV signals are horz polarized by convention and there is very high attenuation in opposite or cross pole reception, as it's called...
Historically, the Television Broadcast Service has used horizontal polarization, but vertical polarization is also allowed, creating what is known as circular polarization (if the vertical and horizontal powers are equal) or elliptical polarization (if the power is not balanced between the H and V fields). This is mentioned in a recent FCC report, which I excerpt below:

Quote:
Polarization. FCC rules require that television stations transmit a horizontally-polarized wave, but stations may add a vertically-polarized component in phase quadrature at a power level up to that of the horizontal polarization to achieve elliptical or circular polarization of the transmitted wave. Since the total radiated power is increased by up to a factor of two by this method, improved coverage may result.
Source: http://data.fcc.gov/download/incenti...s_2013July.pdf

Many television stations transmit with circular or elliptical polarization. Receiving antennas which are designed for circular polarization will generally produce better reception than linearly polarized receiving antennas, if the transmitted signal is circularly or elliptically polarized. The FCC says about 14-percent of TV Broadcast Stations are using circular polarization, but, based on my experience as a professional Broadcast Engineer for 37-years, I believe in major markets a higher percentage of stations are likely to be using circular or elliptical polarization. This is done for competitive reasons: to try to produce the best possible signal into as many TV receivers as possible.

To suggest that using an antenna with circular polarization for reception of Broadcast TV signals in the USA will be of no value is not quite accurate. However, there are few antennas available for receiving in circular polarization, and very few viewers have them.

de K8SS
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Old 29-01-2015, 19:26   #17
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Thumbs up Re: Marine TV Antennas

Have had many difficulties with TV reception.
Until I purchased an oceantalk marine standard definition digital tuner.
This has 2 small whip antennas & 2 tuners (diversity) that combine the
signal to make 1 good one, this will work whilst at sea & boat is
Moving.
How ever this system is hugely over priced.
The new HD unit is aus$900+
Have looked for alternatives to to this unit for 2 reasons
1/ overpriced
2/ service is non existent oceantalk Australia would not return
calls & could not even buy one (not recamend end)
Further investigation revealed DVBT tuners designed for cars
These retail for $100 & up.
You will need to buy extra cable for the antennas
the higher they are mounted the better
The car units have as many as 4 antennas but 2 is
enough as long as they use the diversity system.
The antennas are small & not directional.
Recamend the box is mounted inside in a dry location
however some of them have conformal coated circuit boards
They are claimed to work at speeds above 200kph
Active antennas are available but would suggest that this is
Not needed, I would advise that you use quality coax cable
to reduce signal loss
I would further suggest that you look for one that decodes
MPEG 4 as I believe this will be the future of HD TV
Means you will not have to upgrade later
Reception with my unit is crystal clear, it will work with
Any TV
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Old 29-01-2015, 22:05   #18
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Re: Marine TV Antennas

Before going through all the trouble of an expensive, on the mast or arch mounted, special 'marine' digital "over-the-air (OTA)" television antenna and coax runs, etc., try one of these inexpensive 'indoor' (household) amplified antennas first and see if it works well enough:

"Satechi HD Digital Indoor Flat Amplified TV Antenna w/ Wall Mount (Powered by USB)"
Satechi HD Digital Indoor Flat Amplified TV Antenna w/ Wall Mount (Powered by USB) - Newegg.com

Just mount it up as high as possible in the cabin, power it with a USB cord source (standard +5V), and tune your teevee in.

It just might work. I noticed a marked performance improvement over several other OTA TV antennas. If it doesn't, you're not out much, and it can be used elsewhere (EG: you can feed an FM radio). OTA TV broadcasting is all I watch anyway.

Some general info on broadcast reception--
Back when the terrestrial television 'analog to digital' transition was in progress, I was using a plain rabbit-ear VHF/wire loop UHF 'tunable' antenna, and a couple of other 'flat' types, at home (home is well inland, up fairly high on a ridge).
The television broadcasters were busy 'tuning up' their new digital OTA signals all over S. Texas; and I was getting my ATSC converter boxes, feeding plain old analog CRT TV's, to pick up stations from as far as 275 miles away (even Mexican stations). The reception was excellent, even then with plain rabbit ears.
After about a week or two those far away stations dialed their transmitter power down a bit and I rarely see them now. Still get ~45-50 channels (incl subchannels) from ~60 mile radius.
Thinking if I mounted a decent antenna (maybe even the one linked above) in the attic, or outside, I might get comparable coverage again, in most atmospheric conditions.
At sealevel, reception isn't as good of course, but it just depends on many factors.

Long ago (~1983-87) when we were building out the early AMPS mobile phone networks (the first 'cellular' analog system, EG: Motorola 'brick' phones), down near the coast (S. Padre Island area), you could sometimes draw your dialtone from cellsites as far away as Houston, across ~200 miles of the Gulf of Mexico (and these were just 3-5 watt handsets and bag phones). It's all just FM , as we used to joke (doesn't stand for 'Freq Modulation').
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Old 30-01-2015, 12:18   #19
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Re: Marine TV Antennas

Quote:
Originally Posted by Tx J View Post
Before going through all the trouble of an expensive, on the mast or arch mounted, special 'marine' digital "over-the-air (OTA)" television antenna and coax runs, etc., try one of these inexpensive 'indoor' (household) amplified antennas first and see if it works well enough:

"Satechi HD Digital Indoor Flat Amplified TV Antenna w/ Wall Mount (Powered by USB)"
Satechi HD Digital Indoor Flat Amplified TV Antenna w/ Wall Mount (Powered by USB) - Newegg.com...............
And turn it toward the transmitter. And turn it again when the boat swings.

Again, if your boat moves you will need an omnidirectional antenna. If you stay at the dock to may not.
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Old 30-01-2015, 14:21   #20
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Re: Marine TV Antennas

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Originally Posted by rwidman View Post
And turn it toward the transmitter. And turn it again when the boat swings.

Again, if your boat moves you will need an omnidirectional antenna. If you stay at the dock to may not.
And you're making a major assumption that that inexpensive antenna I recommended isn't at least reasonably 'omnidirectional".

I mentioned it as a worthwhile 'experiment' y'all might want to try out, trying to be a little helpful.
Because I've personally used it, in several different locations (widely separated) and orientations, and found little "directionality" about it.
I purposely experimented with it , hence my original trial rec for anyone so inclined to give it a try-out; for just a few $ at risk, compared to the major hassle of an expensive, mast mounted antenna which still might disappoint.

Its 'flat' appearance may just be visually deceiving, I'm not going to take one apart just to see what's inside, but they work quite excellently (even with the USB power disconnected, IE: in an unpowered condition).
When I mentioned trying it inside the cabin, I should have mentioned that you can even mount it flat to the overhead and it seems to work fine (and is out of the way, not that it is very big to begin with).
That would seem to me to indicate that this antenna wasn't particularly non-omni in either orientation/azimuth nor polarity. But I'm just an ol' EE who spent a career slinging bits, bytes, code, electrons, and microwaves, FO lightwaves too, heh; starting with vacuum tubes and discrete SS systems, right into today's neat stuff.

I've gotten several of those antennae, installed one for the ex's new big screen TV, not too far from a major "antenna farm" (for some stations), and she was delighted with the picture and tuning improvements (even now picking up distant LP stations).

Again, I simply suggested to any openminded CF'ers that they consider trying such an inexpensive antenna option trial, before committing to something 'fancier' that may prove to be unnecessary.
I know, too, that politically in the US, there are certain elements who just can't stand the idea of "free" OTA mass television broadcasting (paid for of course by 'commercials'), and would like everyone to have to purchase their viewing from one of the rapacious cable/sat/etc companies (not BS'ing either, there have been substantial lobbying efforts towards that goal). But OTA is here, now, and you just pick it up however you can.

I fully realize (now) that antennae may also be the open air version of the dreaded "anchor" topics.

I have no interest/stake in that particular model antenna, there may be others even better, look around.
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Old 30-01-2015, 16:01   #21
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Re: Marine TV Antennas

[QUOTE=Tx J;1737172]....... But I'm just an ol' EE who spent a career slinging bits, bytes, code, electrons, and microwaves, FO lightwaves too, heh; starting with vacuum tubes and discrete SS systems, right into today's neat stuff.

But never television or radio.
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Old 30-01-2015, 17:10   #22
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Re: Marine TV Antennas

[QUOTE=rwidman;1737239]
Quote:
Originally Posted by Tx J View Post
....... But I'm just an ol' EE who spent a career slinging bits, bytes, code, electrons, and microwaves, FO lightwaves too, heh; starting with vacuum tubes and discrete SS systems, right into today's neat stuff.

But never television or radio.

...groan...

I may have been skritching on Smith charts before you were shaving... but yeah, t&r was just an 'incidental' area (w/ actual time in a television operating center). But my primary focus was on managing and technical troubleshooting far more complex systems.

crystal radios-- check
various antenna array noodling-- check
various comms & radar-- check
early mainframes, mini's, etc., etc-- check
slinging machine code, assembler, etc-- check
massive and embedded systems-- check
UPS generating and batt backups (including diesel&gas turbines)-- check
debugging and redesign-- check
etc etc

It was too many fun. A good book for an idea: "The Soul of a New Machine", by Tracy Kidder, (there's an external link downpage on the Wikipage to download a copy to read, if it works). The Soul of a New Machine - Wikipedia, the free encyclopedia

Dang near everything's just a PnP 'blackbox' today.

For all I know that little TV antenna has some sophisticated beamforming phased array elements inside, who knows? It works PFG. For $30 I guess I could see if it has some screws holding it together and open one up (the manual and mfg doesn't provide any schematics, drat).

Do you have any concept of what's inside your basic little 'smartphone'? For an 'oldtimer', I find them mind-boggling (and I date from plain MTS's through CDMA/GSM in that field). Six or eight different uber-complicated radios and fancy antennae, mainframe equivalent computing power, etc., huge, complex supporting infrastructure; just fantastic stuff.
And most users don't have a clue.

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Old 30-01-2015, 18:08   #23
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Re: Marine TV Antennas

The best digital TV antenna make yourself for around $5. Have made one with great success. It is rather directional so I mounted on aft pulpit rail so it can be turned. It sounds dumb but works great.
http://www.repeater-builder.com/ante...er-antenna.pdf
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Old 30-01-2015, 18:15   #24
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Re: Marine TV Antennas

[QUOTE=Tx J;1737270]
Quote:
Originally Posted by rwidman View Post


...groan...

I may have been skritching on Smith charts before you were shaving... but yeah, t&r was just an 'incidental' area (w/ actual time in a television operating center). But my primary focus was on managing and technical troubleshooting far more complex systems.

crystal radios-- check
various antenna array noodling-- check
various comms & radar-- check
early mainframes, mini's, etc., etc-- check
slinging machine code, assembler, etc-- check
massive and embedded systems-- check
UPS generating and batt backups (including diesel&gas turbines)-- check
debugging and redesign-- check
etc etc

It was too many fun. A good book for an idea: "The Soul of a New Machine", by Tracy Kidder, (there's an external link downpage on the Wikipage to download a copy to read, if it works). The Soul of a New Machine - Wikipedia, the free encyclopedia

Dang near everything's just a PnP 'blackbox' today.

For all I know that little TV antenna has some sophisticated beamforming phased array elements inside, who knows? It works PFG. For $30 I guess I could see if it has some screws holding it together and open one up (the manual and mfg doesn't provide any schematics, drat).

Do you have any concept of what's inside your basic little 'smartphone'? For an 'oldtimer', I find them mind-boggling (and I date from plain MTS's through CDMA/GSM in that field). Six or eight different uber-complicated radios and fancy antennae, mainframe equivalent computing power, etc., huge, complex supporting infrastructure; just fantastic stuff.
And most users don't have a clue.

Well you are certainly a much more accomplished and experience person than I am but you're still wrong.

You can be anything you want to be on the Internet.
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Old 31-01-2015, 07:01   #25
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Re: Marine TV Antennas

If you are within a large TV market and close to the broadcast towers, anything up to and including a metal coat hanger will get you digital TV. So home-built or inexpensive units may very well work for you if you never leave those areas. But most of us need a little more because we are cruising over large areas and find ourselves in distant fringe areas more than we are sitting close to major markets. So we need something more to bring in those signals. That mean spending more money for the omnidirectional antennas and the need for a signal booster. An old bicycle wheel our piece of aluminum just isn't going to work 99% of the time for us. So what will work and what you will need is very dependent on where you will be using it. Chuck
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Old 31-01-2015, 07:12   #26
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Re: Marine TV Antennas

Quote:
Originally Posted by DeborahLee View Post
The best digital TV antenna make yourself for around $5. Have made one with great success. It is rather directional so I mounted on aft pulpit rail so it can be turned. It sounds dumb but works great.
http://www.repeater-builder.com/ante...er-antenna.pdf
See my post #19 above.
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Old 31-01-2015, 07:24   #27
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Re: Marine TV Antennas

Since the magic word ("digital") has been mentioned, let's make it clear: There is no such thing as a "digital antenna". An antenna is an antenna. A TV antenna is a TV antenna. The antenna does not know or care if the signal is analog or digital, it just picks up a signal and delivers it to the receiver.

Companies advertising antennas as "digital" are just trying to fool consumers into thinking they are getting something better.
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