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Puckdropper
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Joined: 02 Oct 2004
Posts: 749
Location: Not in Chicago

PostPosted: Sun Oct 30, 2011 8:48 pm Reply with quoteBack to top

My reception was pretty marginal due to having the antenna in the basement. Sometimes the station was just unwatchable.

So, I built a folded dipole antenna out of some 300 ohm twin lead. Nothing special, but it works better than the other antennas I had. One channel gained about 10-15 percentage points in strength according to the meter, while another gained only a couple.

For a few minutes of twisting wires, I'm quite pleased with the results.

We'll see if things improve any when a commercial antenna gets here. I'll be nice to actually watch Roy UnderHill make wooden blocks and not have to watch a blocky Roy UnderHill. :-)

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wdegroot



Joined: 03 Feb 2006
Posts: 487
Location: pennsylvanai

PostPosted: Mon Oct 31, 2011 5:22 pm Reply with quoteBack to top

there is a variation to the "folded dipole" made from 300 ohm tv twin line. it is the extended double zepl.
I do not recall the length- I will look.
but you take a long piexe of tv twin lead and split it
making a TEE with a single wire extending to the left and right the ends can be looped and taped to you can support it with fiskline or string
and at the tee you tape it so it does not continue to rup.
NOTE" it differs from the standard twin line dipole as the top is a single wire going to the left and right.

there are also alternate antennas

one is two wires or strings forming a Vee with folded aluminum foil over the to paper clips are used to connect a piece of twin lead tohe edges of the folded foil elements at the poijnt of the VEE.
a third is a aluminum foil bowtie flat on the floor under a throw rug, often on an upper floor.

I once built a FM band yagi antenna ( named for the japanede engineer) it was a 4 foot stick
the first 2 or three enelments were stretched straight aluninum wire 10 gauge used a tv antenna ground wite or clothesline
they started with a shorter piece than a slightly longer piece then a tv wire folded dipole and behind them was a slightly longer piece
front ones were directors ( stapled to the wood
and the rear piece was a reflector
spacing and length is fairly critical
it was so close that placing my hand in between the front directors 18" from the dipole would detune and cause me to loose the station.

the best constucted by " househole engineering" in branchville nj
was a rhombic antenne
a huge diamons shaped affair
I suspect the the long shed like office was built and oriented to point at the enpire state building 50 miles east. in 1946.
there was no cable then. and several poles supported this diamons shaped wire affair. on the roof. at that time they sold tv sets
and the dipole plus reflector or the fan shaped antenna was polular.
they needed to show a clear picture to customers and the rombic antenna, invented by ham radio operators did the job.

there is a story that during the Korean was some hams in california had a rhombic ( rombus)
slnstructed in a western facing valley in the california coast.
they pvided ' telephone patch" service to soldiers in Japan and Korea.
the system using less than 1,000 watts of power
were able to communicate sucessfully when the army or navy with much more power and state of the art equipment failed.
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Puckdropper
Site Admin


Joined: 02 Oct 2004
Posts: 749
Location: Not in Chicago

PostPosted: Mon Oct 31, 2011 5:32 pm Reply with quoteBack to top

The length of the folded dipole is related to the station you wish to pull in. One element is just under 8 1/2" for channel 46, while the other element is 9" for channel 39.

It's supposed to be half of the wavelength, but the one that works well wound up 1/8" shorter than it was supposed to while the one that works ok is the correct size.

_________________
>say "Hello sailor"
Nothing happens here.

>score
Your score is 202 (total of 350 points), in 866 moves.
This gives you the rank of Adventurer.
View user's profileSend private messageVisit poster's websiteAIM AddressYahoo MessengerMSN MessengerICQ Number
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