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Old 25-04-2008, 04:27   #1
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homemade tv antenna

Several years ago I had a tv antenna made of aluminum bar bent into a circle (about 2 ft. in diameter) which could be hung by a halyard. Mine was on the boat when I bought it and I think it was store bought but I'm sure there used to be plans out there for building your own. I can't find one for sale anywhere and would like to have another one (for the life of me I don't know what happened to the one I used to have).

Is there anyone out there who is familiar with the antenna I'm talking about and if so do you know where I could purchase one or where I could find plans to build one ( I have plenty of aluminum around) or could you please discribe how to build one.

Any help would be appreciated.
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Old 25-04-2008, 05:04   #2
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Mobetah,

Here's the instructions for making a tv antenna.

Make you own .....

"6-66 antenna".
Can be used for FM/VHF/UHF and is omnidirectional.
Cost: ~$4.00 + splitter and coax.

Take a 66 inch length of small copper tubing and form it into a circle. then put a 'gap' of exactly 6 inches where the two ends of the circle of tube come together and use rubber hose slipped over the 'ends' to maintain the 'gap'. Drill two small holes through the tubing near the 'ends' for small screws, washers and thumbscrews to affix a screw-on 'splitter/amplifier'. Attach lightweight coax cable to the splitter.

Tie on lightweight line/cord to make a 'cradle' so that the antenna is horizontal to the horizon. Raise the antenna on a flag halyard on your spreader - enjoy. Dont let the antenna touch the mast or shrouds.

No need to cut...

Just bend the 66" length so there is a 6" gap.

The total 'circle' of copper and hose will be about 72 inches
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Old 25-04-2008, 06:54   #3
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Thanks Rick,
That sounds very similar to the one I was trying to describe except in copper ..... Unless someone else has any ideas, I'll give your design a try and let you know how it works out.
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Old 25-04-2008, 07:29   #4
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Mobetah,

Bruce Bingham's "Sailor's Sketchbook" has the exact plans you are looking for. I used it to make one a batch of years back and it worked GREAT!

Greg
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Old 25-04-2008, 09:28   #5
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Well, when all stations go to digital next year it will be a moot point!
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Old 25-04-2008, 11:52   #6
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Nimble - not true. With a converter box you can still use your antenna. I'm using one of the aluminum circle antennas and get the digital stations on my LCD HDTV on the boat.
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Old 25-04-2008, 12:31   #7
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Well, when all stations go to digital next year it will be a moot point!
An antenna is an antenna - absolutely no difference between a "digital-capable" antenna and one for analog, except for the dishonesty on the part of the manufacturer's marketing department.

The only real difference (as far as an antenna is concerned) between most of today's analog TV broadcasts is that the majority of today's digital broadcasts are in the UHF band, not VHF. So, depending on where your cruising grounds are, you could get better reception with a smaller, dedicated UHF antenna.

If you're less than 15 miles or so from the transmitters, a cheap $3 UHF loop antenna will work just about as well as a Shakespeare amplified TV antenna - because the Shakespeare is a compromise loop which depends on an amplifier for UHF performance (the size of the loop is tuned for VHF's longer wavelength).

A note on Vasco's antenna - make sure you use a 300Ω-75Ω balun, since the natural impedence of a loop antenna is 300Ω...

Try this variation on Vasco's design: take 25" of stainless seizing wire, and make 90 bends 1.5" from each end. Bend the remaining 22" into a 7" diameter loop, and bend the ends of each 90 into a tight loop.

Since you might have to run to RadioShack to buy the balun (or "matching transformer" as RS calls it), you might as well save the time and pick up this bowtie antenna - has better gain of the loop. Some stores may have the loop antenna...

The attached PDF shows enough detail for the average cruiser to fab it with...
Attached Files
File Type: pdf UHF Loop Antenna.pdf (36.0 KB, 4386 views)
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Old 25-04-2008, 13:53   #8
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http://www.usbwifi.orconhosting.net.nz/

Now have great fun making some of these beauties, and have improved wi-fi on the boat. Only test I have done is to place my Nokia 770 at the centre of a Cooling fan guard about 8" diam. Made a huge difference to the number of hotspots picked up!
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Old 25-04-2008, 16:59   #9
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I just bought my first digital converter box. Plugged it into the rabbit ears and everything is amazingly crystal clear. Much better reception than I got before.

If you're really trying to go cheap, a simple length of stainless steel wire works pretty well. Just plug it into the centre hole.
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Old 25-04-2008, 19:36   #10
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TV

G'day, I use the VHF radio aerial thru a set top box. The 50' height of the mast makes up for a lot of Technical Mis Matches. I have a spare VHF aerial on the back rail for close in shore areas where the TV might be used. You could wire in a coaxial switch & select TV or radio to make a neater install. I am 40ks from the TV stations & getting good TV. No extra aerial. One less thing to worry about!!

Regards Bill Goodward
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Old 07-06-2008, 15:18   #11
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Vasco, I used your plans and a 66 inch piece of 3/8 inch copper tubing to build an antenna. It works great ..... went from good reception on one public service channel (using the rabbit ears) to ecellent reception on two channels, good reception on two more channels and fair reception on a fifth channel.

I just got my $40 card for the coverter box yesterday ..... can't wait to try it and see what happen to my reception.

Thanks everyone ............. Bill A.
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Old 10-06-2008, 23:56   #12
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The loop antenna asked about is called a Boatenna. I bought one used on ebay a few years ago. Works very well.

Here is a link for DIY antenna for digital channels:
DIY HD Antenna - Hack a Day

I love HD, but one bad thing is that reception distances will be much less. Analog tv gets fuzzy but is tolerable down to a real degraded level. Digital becomes unwatchable when more than a minimal amount of the data stream is lost.

Here at home near the Pentagon I get over 20 digital channels using rabbit ears. But when the landing pattern at National Airport is bringing the aircraft down along the Potomac river, the planes seriously mess with the signal and the picture will break up, then freeze.

In contrast, using the boatenna, when I am dockside down near Calvert Cliffs on the Chesapeake, I can pick up several analog channels from Baltimore with quality from acceptable up to good. I get very clear channels from Annapolis, and from Salisbury and Ocean City over on the eastern shore and Atlantic coast. And some nights I can even pick up PBS station WHYY in Philadelphia! Fuzzy, sure, but watchable. Won't be able to do that in digital. (I tried tuning digital and got 3 stations in very marginal, unwatchable quality.)
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Old 11-06-2008, 10:34   #13
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HD is basically UHF. The bad news is that any money spent on a conventional VHF antenna today will be wasted when VHF goes off the air in February. The good news, is that the little inexpensive circular UHF antennas are all you'll need for HD, if you're in range of a good signal.
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Old 12-06-2008, 09:13   #14
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HD is basically UHF. The bad news is that any money spent on a conventional VHF antenna today will be wasted when VHF goes off the air in February. The good news, is that the little inexpensive circular UHF antennas are all you'll need for HD, if you're in range of a good signal.
Yeah - what Hellosailor said. With a caveat: in some television markets, there will still be some VHF channels, just digital instead of analog. You just need to check and see what's there in your particular area.

And regarding Trekka's problem - what you are experiencing is severe multipath signal degradation due to receiving signals from the broadcast source and some signal reflected off the aluminum bodies of aircraft. This was certainly a problem with 1st and 2nd generation 8-VSB digital tuners. The later generation tuners (last 3-4 years) are much better at multipath discrimination. Trekka - how old is your digital tuner? I have an old Mitsubishi DirecTV/ATSC tuner, and a year-old PC-based digital tuner for my PC, and there's just no comparison - the PC tuner runs rings around the older Mitsu...
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Old 12-06-2008, 10:36   #15
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My HDTV was made last year. I also have a USB HDTV tuner for my pc. The single pole antenna that came with that does as good a job of tuning as does the regular rabbit ears and loop for the HD. My location is very good for reception. Most of the towers are on the hills in the west and north of the city. I'm on a plain just across the river. But the flight path when all the traffic to National comes in along the river puts them between me and the towers in their last minute of final approach.
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