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Author Topic: What to do next  (Read 2462 times)
KL7SB
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Posts: 19




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« on: August 03, 2008, 03:55:18 PM »

After years of living with wire antennas and the occasional less than optimum radial ground mounted vertical, I've finally managed to put up a 70 foot tower (7 sections of Rohn 25), with two beams, a TH3 3 element tribander and a Cushcraft 6/2/70cm yagi on a Tailtwister rotor.  All I can say is everything WB2WIK has ever said about it being a different hobby with good antennas and height is true (at least on the HF side, there just isn't much VHF weak signal work going on up here except EME, and the three band beam is still a compromise).

Now that I'm hooked, I want something for the WARC bands.  I'm considering a few options, and I'm wondering what would make the most sense.  I'd prefer not to replace the rotor, and I don't have the option at least now to put up a second tower.

1)  Replace the TH3 with a TH11.  Fairly straightforward, somewhat expensive, especially with shipping up here (actually tried this once, the antenna got destroyed somewhere between Hy-gain and HRO).

2)  Replace the TH3 with a 3 element Steppir.  I've used a Steppir when I was operating in Iceland/TF3 and was very impressed.  It is also easy to add their "triangle" of rotatable dipoles, so I could add 30-40m to it (someone still has to explain to me how they claim "gain" on dipoles).  Downside is highly expensive plus a wait.

3)  Someone up here is selling a A3WS, that is the Cushcraft 3 ele 12/17m yagi.  This would be the cheapest, and probably what I would do, if I could.  Problem is, I don't see how the spacing, weight, wind load with the other antennas could work, and I'd like to be conservative about that.

Any thoughts and thanks.
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W3LK
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Posts: 5639




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« Reply #1 on: August 03, 2008, 04:24:20 PM »

Another possibility is a LPDA from Tennadyne.

73,

Lon - W3LK
Naugatuck, Connecticut
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
KL7SB
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Posts: 19




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« Reply #2 on: August 03, 2008, 05:33:29 PM »

Thanks Lon:

What are the advantages and disadvantages of Log Periodics as opposed to multi band yagis?

73

Steve KL7SB
Anchorage, AK
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KL7SB
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Posts: 19




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« Reply #3 on: August 03, 2008, 05:37:00 PM »

ooops I mean Log Periodic Dipole Arrays (LPDA) vs. multi band yagis
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W3LK
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Posts: 5639




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« Reply #4 on: August 03, 2008, 07:26:41 PM »

Essentially continuous coverage from 13 to 30 mHz. Smiley

Read the Tennadyne page.

73,

Lon - W3LK
Naugatuck, Connecticut
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K4SAV
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Posts: 2409




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« Reply #5 on: August 03, 2008, 08:44:22 PM »

...."(someone still has to explain to me how they claim "gain" on dipoles)."....

OK.
All antennas have gain.  The question is how much?  Gain is relative to something and can also be negative.  SteppIR claims 2.1 dBi for their 30 meter dipole, and 1.8 dBi for their 40 meter dipole.  A standard half wave dipole's gain is 2.14 dBi.  All those are free space numbers.

Jerry, K4SAV
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K4SAV
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« Reply #6 on: August 03, 2008, 08:50:29 PM »

I should have added: All those are relative to an isotropic source.  If you want to make the numbers relative to a dipole (dBd), just subtract 2.14 from all the numbers.
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KL7SB
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Posts: 19




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« Reply #7 on: August 04, 2008, 01:39:32 AM »

Hey Lon:

Yep looks interesting.  Unless I can put the A3WS on the same tower as the TH3, that could be the answer.  I'll have to do some math, but it looks like I could probably go for a T8 or T10 which would give me 10-30.

Steve KL7SB
Anchorage, AK
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K0OD
Member

Posts: 3005




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« Reply #8 on: August 04, 2008, 07:21:00 AM »

Consider getting on 60 Meters this fall when the band quiets down. There's been no KL7 activity lately on the 5 MHZ band. Most DX is done on CH 5 which is 5403.5, or sometimes Channel 4.  Remember USB only with a 50 ERP power limit.  

Recently, the third Saturday evening (2300-0300) of each month has been designated a Trans-Atlantic Activity Night. You'll find more DXers on at that time.      
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WB2WIK
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Posts: 21757




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« Reply #9 on: August 04, 2008, 09:47:08 AM »

The T10 or T12 would be an excellent choice, I think.  LPDAs don't have as much gain as Yagis (most LPDAs, no matter how many elements they have, are equivalent to maybe a 2-3 element Yagi at best) however they are very broadband, match well, very simple, no moving parts, no tuning and do provide tremendous side rejection for nulling stuff, which of course is one of the primary advantages of any sort of beam antenna.

The 3L SteppIR has more gain, but does have moving parts and they can (and do) fail.  I hadn't heard of any failures at all initially (which surprised the heck out of me!) but lately I've heard of half a dozen, and I suppose we'll be hearing of more failures as the field population grows and ages.

If the beam was on a roof tripod or something, a failure wouldn't be a big deal to me.  But atop a 70' guyed tower, it's a real nuisance to be serving antennas.

The TH11's a pretty good antenna, also, but very large and heavy and might overstress your mast or tower, depending on the details of those.  If you're using a 2" O.D. thickwall mast intended for use as an antenna mast, and the tower is well guyed, preferably with torsion bars (at least at the top section), the TH11 on a 25G will work.  If you're using a smaller mast and don't have torsion bars on the top section to prevent tower twisting, the TH11 may be a "bit much" for a 25G.

Mosely, Force-12, Cushcraft and others also make pretty good "5-band" and "6-band" HF antennas.  They're all good in various ways.

WB2WIK/6

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KL7SB
Member

Posts: 19




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« Reply #10 on: August 05, 2008, 01:47:53 AM »

Steve:

Yep, my main concern about the SteppIR is putting more electronics in a hard to access area.  Climbing a tower in winter here is only for the foolhardy (or my friend Bob KL3BD, but of course he also climbs Mt. McKinley for fun and radio testing).  Last thought here, would it make sense to try to put up the A3WS, along with the TH3 and A6270-13S (the Cushcraft VHF/UHF), or would the spacing just be impossible.  At this point I'm leaning towards the LPDA, but wondering if I'll be losing much in the way of gain over the TH3 currently up.  I see that I am going to need a second tower at some point. P.S. you probably don't remember me from back then, but I do remember you running the repeater on Mt. Olive NJ.  My call then was WB2IDP.  My brothers Bob (then WA2SLY now KC7KNY) and Michael (then WA2RAT now W7RAT) and my dad WA2QAO (sk 1980) were also active back then.

Jerry:

Thanks for the info on dbd vs. dbi.

73

Steve KL7SB
Anchorage, AK
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K7MH
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Posts: 427




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« Reply #11 on: August 05, 2008, 04:09:38 PM »

I do not think the spacing is going to be that big of a deal really. How much spacing can you give them is the big question. I didn't see anyone addressing how much spacing you would really need but  would bet they can be closer together than you are thinking.
Put up a 3 or 4 element 5 band quad and you won't regret it! I have a 2 element 5 band quad (now 6 with 6 meters) and it is a whole new world over the Cushcraft A4 I used to have. I have a friend with a Force 12 5 band beam, not sure which one, and it plays well too.
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KL7IPV
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Posts: 984




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« Reply #12 on: August 20, 2008, 10:15:19 PM »

The one thing you have to think about when you hang antennas up is the extra snow and ice loading you can get there. When I lived in south Anchorage, that was something I saw on my own tower and TH3JR. It may be because I lived close to the inlet off south Seward Hwy, I don't know. It didn't seem to hurt the antennas for operation and SWR but the extra loading tends to bend the elements. Good luck.
Frank
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