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Author Topic: 2 metre Yagi, for SSB question.  (Read 2039 times)
2E0ILY
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Posts: 131




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« on: April 11, 2012, 09:57:50 AM »

I am on the lookout for a decent 2 metre Yagi for SSB usage. Now, here in the UK, and probably everywhere, SSB 2 metres is apparently on horizontal polarisation. Does that mean there's a specific antenna for it, or will turning any Yagi through 90 degrees on it's mount convert from vertical to horizontal polarisation? As you can tell, I am new to this..... Wink I have been given a 70 Cms Yagi that has two sets of reflectors and two independent dipoles, with two independent cables, so it can be used horizontal or vertically polarised. Is there any disadvantage in these types to having two separate antennas, of independent polarisation? Can they be got for 2 metres as well? Be kind please! Thanks.
« Last Edit: April 11, 2012, 10:01:16 AM by BASIL » Logged

Best regards, Chris Wilson.
WB2WIK
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Posts: 20540




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« Reply #1 on: April 11, 2012, 10:03:18 AM »

Horizontal polarization is preferred on 2m (and all the VHF bands) for all work except FM, where vertical is dominant.  There are good reasons for this.

Most "vertically polarized" beams will work fine if rotated 90 degrees on axis so all the elements are in the horizontal plane.

Some beams are optimized for a portion of the band, though.  If the beam is optimized and tuned for 147 MHz (center of our FM band here in the States), it may not work as well down at 144 MHz where most all SSB activity is as one that is optimized for the lower part of the band.

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KM3F
Member

Posts: 494




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« Reply #2 on: April 11, 2012, 10:16:02 AM »

Right in your home country is a very fine antenna company called INNOVANTENNA.
Give them a call with your questions on the use of their antennas.
Tel 0800-0124-205
Good luck.
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WB6BYU
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Posts: 12983




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« Reply #3 on: April 11, 2012, 01:47:33 PM »

2m beams from American companies sometimes come in two versions, one for weak
signal work optimized for 144 - 145 MHz and one cut for FM operation on 146 - 148 MHz.
European designs typically cover 144 - 146, which is the whole band in IARU Region 1.
Newer designs can cover the whole 144 - 148 MHz range (IARU Region 2) rather than
needing two different designs.

Just about any yagi can be used for either vertical or horizontal polarization just by
mounting it differently.  Other than an American antenna cut for 147 MHz, any of the
common designs should work for you.  Here are some designs to consider:

http://www.mydarc.de/dk7zb/
http://www.g0ksc.co.uk/
http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf
http://www.yu7ef.com/LowTemperatureAnt.htm
http://www.k7mem.150m.com/Electronic_Notebook/antennas/yagi_vhf.html

You would only need an antenna of each polarization if you need a high-gain vertical
beam to work distant repeaters or simplex FM stations.  In many cases an omnidirectional
vertical is quite adequate for the local FM repeaters rather than using a beam.
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2E0ILY
Member

Posts: 131




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« Reply #4 on: April 11, 2012, 02:00:24 PM »

Thanks for the great replies. I like making stuff and being in the motorsport game have good fabrication facilities, so have knocked up a J antenna for FM, but making a Yagi is probably not cost effective, especially if I can find a good used one at a rally or in the ads. Now I know the ins and outs of what I am looking for I should be able to shop with a lot more confidence Wink Thanks very much everyone.

BTW, now I have a call sign can I change my user name, or should I just re register and start again with my call sign as user name?

Cheers! Oh, no, sorry : 73   Wink
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Best regards, Chris Wilson.
KE4VVF
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Posts: 61




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« Reply #5 on: April 11, 2012, 06:44:26 PM »

I use a Cushcraft 14820T fed with two different coax lines.  It is 11 foot long and has 10 elements vertical and 10 elements horizontal.  I switch between the two polarizations via a switch to change between SSB and FM.

It's not the most fab antenna but it suffices for my limitations of length and weight.  It may be right for you and can be easily turned with a TV rotor.

You can read mine and other's reviews here.
http://www.eham.net/reviews/detail/1658
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KM1H
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Posts: 30




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« Reply #6 on: April 14, 2012, 12:12:32 PM »

http://www.bigskyspaces.com/w7gj/6mTable.htm

The above includes just about every 2M (or 6M) yagi design know, commercial and homebrew. Pick the boom length you require and go from there to a source.

Carl
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KF6A
Member

Posts: 214




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« Reply #7 on: April 16, 2012, 12:59:23 AM »

........but making a Yagi is probably not cost effective, especially if I can find a good used one at a rally or in the ads........
False. Buying a used antenna can be hit or miss with missing parts, corroded tubing, etc. Building it yourself is the most cost effective method, especially smaller VHF antennas. You may want to practice building smaller antennas before tackling large HF yagis though.
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KA1MDA
Member

Posts: 543




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« Reply #8 on: April 16, 2012, 11:46:21 AM »

Quote
"Buying a used antenna can be hit or miss with missing parts, corroded tubing, etc. Building it yourself is the most cost effective method"

It all depends on the situation. All but one of my antennas were obtained second hand, including a Hustler 6BTV with a spare 80m resonator and stinger ($75), Hygain VB-66DX ($50), KLM 2M-16LBX ($25), K1FO DSFO-432-25 ($25), and a Directive Systems 2345LY (free). I got the 1296 looper for free because it had been dropped, deforming most of the elements. It took quite a while the make them all round again and lined up and spaced properly! Oh yeah, the 45 foot Rohn 25G tower was used also ($100)!

The secret is to only consider used antennas that are still fully assembled. That way, you can inspect the antenna's condition at the seller's location first, then disassemble it yourself, carefully marking the the sub assemblies. That way, you know the antenna is complete, and more importantly, you'll know how to put it together again!

Tom, KA1MDA
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GM3SEK
Member

Posts: 44




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« Reply #9 on: April 17, 2012, 12:18:17 AM »

Thanks for the great replies. I like making stuff and being in the motorsport game have good fabrication facilities, so have knocked up a J antenna for FM, but making a Yagi is probably not cost effective, especially if I can find a good used one at a rally or in the ads.


Not at all!  For a start, you won't ever buy a used high-performance Yagi at a rally (=hamfest) in the UK. They simply aren't there.

Since you have the fabrication facilities you can very easily build your own, and end up with a much better antenna. Almost any Yagi "wants to work", in the sense that it'll send more RF in the forward direction than elsewhere - but that does not mean it is working to its full potential.

A good Yagi design looks almost the same as a poor one, and it probably requires exactly the same number of holes and saw-cuts. So why waste time and money building a poor design, when you could be building a good one instead?

Go to the VHF/UHF Long Yagi Workshop page on my website, follow the links, do some reading and then build your own!

http://www.ifwtech.co.uk/g3sek/diy-yagi/



73 from Ian GM3SEK


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KF6A
Member

Posts: 214




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« Reply #10 on: April 17, 2012, 02:13:19 AM »

........The secret is to only consider used antennas that are still fully assembled........
Since the context is someone asking questions instead of giving advice it should be fairly obvious the one asking the question isn't savvy enough to be privvy to the "secret". Even after "secret" is revealed those ignorant to building homebrew aluminum antennas wouldn't know what to look for anyway. Stated differently, one needs experience before being able to recognize what is or is not usable and a deal. Your response is noted but I stick by my statement as I've had too many acquaintances ask for my assistance with their "new antenna" after they acquired a "really good deal" at a hamfest.

Hamfest antennas are OK places to pick up random aluminum tubing for misc antenna projects but more often than not you are buying someones problem, which is usually why it is being sold at the hamfest. GM3SEK's observation holds true to my observations from the hamfests I've been to in southern california and northern california.
« Last Edit: April 17, 2012, 02:19:03 AM by KF6A » Logged
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