What a pain. It took forever and every time the wind blows, and the SWR at 3820 swings from 1.1:1 to 3:1! I'm sure it is just the metal stuff nearby interacting. I can't really put it any higher, so it will just have to do. I figured it would be tough to tune, but I wasn't expecting it to be quite that tough.
I guess, what do I expect from a hamstick dipole.
I really need to think of something better. What I need is something a little more sturdy. I thought about making a "hustler" dipole with a pair of hustler mobile masts & resonators. But that would be expensive, but I bet I could make something similar with some coils. What I really think I need is the stiffness, and the loading being near the end would make it a little more efficient.
For now, we'll see how the hamsticks work in real life.
It sounds to me like an intermittent connection at the center insulator, maybe, perhaps. Can you stiffen things up with a piece of 2x4 or some 1.5" pvc pipe and U-bolts or hose clamps>? Just an idea.
Bob
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Ham radio is something you DO and LEARN. NOT something you BUY!
What a pain. It took forever and every time the wind blows, and the SWR at 3820 swings from 1.1:1 to 3:1! I'm sure it is just the metal stuff nearby interacting. I can't really put it any higher, so it will just have to do. I figured it would be tough to tune, but I wasn't expecting it to be quite that tough.
I guess, what do I expect from a hamstick dipole.
I really need to think of something better. What I need is something a little more sturdy. I thought about making a "hustler" dipole with a pair of hustler mobile masts & resonators. But that would be expensive, but I bet I could make something similar with some coils. What I really think I need is the stiffness, and the loading being near the end would make it a little more efficient.
For now, we'll see how the hamsticks work in real life.
73 de Joseph Durnal NE3R
Hi Joe,
Did you really expect an extremely short, loaded dipole to less critical of tuning and of the proximity of nearby objects within it's near field?
Exactly, what were you expecting? Just curious...
73.
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73 de Steve, NL7W
Not in but around Palmer, Alaska
USAF Retired and a Telecommunications Professional
Did you chop off the parts of the whip that extend into the fiberglass coil section? Once you get the right length you really should trim it so it only goes in a inch or so. The wind whipping around could have the bottom part of the whip flexing inside the coil and causing your problems.
Extremely short dipoles like ones made from 75M Hamsticks will be very touchy to tune, have almost no bandwidth, and they have very low radiation efficiency.
For a mobile antenna the 75M Hamstick beats a coat hanger but not by much...
I have done the Hamstick dipole thing on 20M and had pretty good luck with it, but at 20M the antenna, even though it's a short dipole, is a lot more efficient and broadbanded than the 75M equivalent.
For anything below 20M, stick with wire. String out as much as you can and use a tuner. It'll work a lot better.
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Fred
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While a 75m Hamstick dipole will always be beaten handily by a wire dipole when the Hamstick dipole is polarized horizontally, assuming the same height of install, a VERTICALLY polarized Hamstick dipole will often handily beat a wire dipole for the same band if the dipole must be close to the ground. On 75m, a half wavelength of elevation would put the wire dipole 37.5 m up in the air, or about 123 feet above ground level. Obviously this is not possible for a lot of us.
I currently have a vertical dipole up 21' on a FRP mast, made from a pair of 75m hamsticks. Fed with about 75' of 50 ohm RG-8/U, it is naturally a 1.1:1 SWR when tuned, and both pulls in and sends out significantly better than my 75m wire dipole did with the same coax and radio (granted the wire dipole had a 6:1 voltage balun in the mix as well, but being a horizontal dipole only 21' AGL, it was a serious cloudwarmer).
EZNEC shows quite clearly that even with the lossy 75m Hamsticks, I am more than 3 db up on the wire dipole at decent takeoff angles, and the closer I get to the horizon, the better the Hamstick dipole is when compared to the wire dipole. If you want to get your signal out some distance, there's something to be said for it.
Granted, I would do a lot better with an aluminum tubing dipole of the same dimensions with cap hats and proper loading coils, and I am likely to build one of those in the not too distant future. Still, for about $50 in parts that I could bolt together quickly, the Hamstick dipole is quite respectable.
As noted, the bandwidth on the thing is razor thin, as one would expect; however, with a Yaesu FC-700 tuner (which supposedly can't tune much more than a 3:1 SWR) I can consistently get well below 1.5:1 SWR throughout 75m. In fact, since I tuned the thing to have its natural low SWR point at about 3860 kHz, I can quite easily tune down to below 1.2:1 SWR from 3800 to about 3920, where things start to climb a bit in the "best tune" department.
I've worked Hawaii, Alaska, Mexico and as far east as Alabama with a Heathkit HW-12 and this tuner/anetnna setup on 75m; once my FT-100D comes back from the shop and I have better discrimination, more power, and my audio DSP back, I expect I will do even better. I have a Hustler 5BTV on the way, which should be even better, even with the lossy traps on 80m, but as an emergency/mountaintopping antenna that can be put together by anyone for that cheap, there's something to be said for the Hamsticks.
I do agree that the wild swings in SWR are either from an interaction problem or poor connections. Get that thing as high up as you can, get the feed line to come off the antenna at 90 degrees to the radiators, and put it up as a vertical. Any horizontal dipole that's so close to the ground is a cloudwarmer and (largely) a waste of time unless you're doing NVIS or don't mind paying the power bill for 100W out but instant QRP for DX. And of course, if you're comparing horizontal dipoles at the same mounting height, a wire dipole (even heavily folded back on itself) is far, far superior.
How about this, These sticks have a threaded mount for the whip and whip adjustment. Remove this section and replace this section with aluminum tubing with one end threaded. The aluminum tubing would be thick enough not to flex like the steel whip.
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I'd thought about that, but the coils in the Hamsticks are very far from ideal as loading coils. I actually did model some stuff in EZNEC based on what you describe, and performance was marginally improved up to about 3-4 feet of tubing added -- beyond that things plummeted in terms of gain, interestingly enough, and there was at best maybe 2/3 of a db of gain with any length of alumunim tubing added to move the Hamsticks away from the dipole center -- not really enough to make it worthwhile IMHO. Raising the antenna from 21' at the dipole center to 42' at the dipole center dropped the radioation angle and gave another 1.8 db of gain -- if I was going to spend money on forwarding the 75m Hamstick vert dipole-based design, I'd get more guy rope and double my mast height. I actually already have the extra mast sections, so I'd just need a few friends and some good stout weatherproof antenna rope.
I don't think there's a huge reason to further the design, myself. My Hustler will certainly beat it across multiple bands, and without having to be raised in the air (I understand the Hustlers actually work as well on the ground with proper radials and you don't have to figure out how to put 1/4 wave radials at an altitude that way!), in addition to being less "peaky" in its tuning.
The Hamstick dipole will probably live on for me as a rugged go-anywhere low-band antenna for mountaintopping and ARES/RACES use, or possibly as the basis for further experiments of other kinds. Until the Hustler gets here, it's not as bad as some might think... And the surprised responses I get from people when I tell them I'm QSOing them on a Hot Water 12 with a 75m Hamstick dipole vertical at 21' are worth the extra aggravation of having to retune any time I touch the VFO's dial.
Tuning 75M Hamstick Dipole
I actually already have the extra mast sections, so I'd just need a few friends and some good stout weatherproof antenna rope. 
Linear Mode
