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2m yagi
Topic Started: 20 Feb 2012 - 11:20 (433 Views)
GingerbreadMan
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i was just looking for a small 2m yagi when i came across this on the bay and thought why not try build it myself as the pics nearly tell all.

what do you all think??


http://www.ebay.co.uk/itm/VHF-Tape-Measure-Yagi-Beam-Antenna-HAM-Radio-2m-2-meter-/110786021772?pt=LH_DefaultDomain_0&hash=item19cb5c898c


cheers

colin

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Miko
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26 Charlie Tango 155
Hi Colin, looks interesting and cheap to build. The 'Hairpin' matching device intrigues me and wonder if there is a formula for the calculation of the length of this ?

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UKDAN
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If you google tape measure yagi a few sites come up with details, I had a look for some of the components the other day & am coming up short on the 4 way pipe fittings.
Edited by UKDAN, 6 Mar 2012 - 11:49.
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Burner
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26 CT 018

Seen then on fleabay looks like they will measure up to the job
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Roy2812
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26 charlie Tango 2812
Following on from your initial post, I had a quick look at my Ancient copy of "Out Of Thin Air" which was published by IPC mags in 1981 as a PW publication. Looking at Fred Judd's article on "Compact 2m Aerials" he shows the complete breakdown and measurements for an end fire array, among others [beam types]. Fred was not a great one for detailed theory and so measurements graph plots and scope display pics rule. From this publication I used a 12el "ZL special" for some ten years, which I built directly off his drawing. It worked from Just outside Swansea, 15ft above ground down into Spain regularly and well up into Eastern Europe with comparative ease. [Earlier today I just had to climb up into the damn loft to see where it was hiding]. Undoubtedly the article will be available in photocopy form from PW upon request if not the whole publication. There were two of these mag style books. Out Of Thin Air and a later follow up edition which I loaned out and so lost. :doh2:

The very simple two ele [both driven] radiators - as a close spaced array, will provide about 4dBd and the end fire with two driven elements acting as driven element/director and driven element/reflector will provide a little over 6dBd. As its so easy to make these from bits and pieces this is a lot of antenna for money. My first was made of thin garden cane and bits of wire clipped together to throw in the back of the car. The second was made of plastic waste water pipe and copper half inch [in those days] tube. I don't think that I purchased any of it, the bits all being liberated from a skip.

Matching of the ZL is easy if fed with 50 ohm coax. Using a couple of short lengths copper wire from the scrap box, which is crossed to phase match, and a 20pF variable cap [once set up and sealed with a glue gun to make it waterproof] a steady 1-1 across the whole of the 2m band is quite easy to achieve.

Illegal to offer scanned copies of copyright material of course in a public forum - even short articles, without publishers permission. However I always answer any e-mail request for assistance ;)

Cheers.

Roy H

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MadMark1
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163 Charlie Tango 020

Ive also built a few yagi's for 2 mtrs, One is a 3 Element and the other is a 7 ELement.

If anyone wants any info on these such as measurements construction etc just let me know.



Mark
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M5AGV
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If your intrested in building yagis, have a look at DK7ZB's website ( http://www.qsl.net/dk7zb/start1.htm ). These are very easy to build and they are also a proven design. Another website is YU7EF ( http://www.yu7ef.com/ ) some of his designs are available from WiMo in Germany, but there are full plans on there to build your own.
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