The AM Forum

With the help of my brave stepson. I have it for sale or trade elsewhere on this forum.

I'm going to go over the rotator to make sure it's still reusable. I still have the inverted Vee up.

So does anyone have any ideas on a loaded dipole I can make out of stuff available at Home Depot, which will handle 800 watts reliably?

73s
geo VE3GZB

What band and how do you want to feed it?

20m only. 800 watts, I have 100 feet of RG/6 if that stuff is man enough for the job.

I have a good tuner, an MFJ-969. I run everything off the balanced feedline outputs and I prefer to not use baluns (I hate it when they are the source of RFI or a mismatch when a good old fashioned direct connection will work best).

73s geo VE3GZB

RG-6 coax cable is not a balanced transmission line.

A full size dipole for 20m is only 33 feet long.  Do you really need to load it in order to make it shorter?

Maybe he wants to run two lines in parallel?  That would be a balanced feedline!!  Probably work pretty good with a balanced tuner too!

The MFJ-969 is rated at 300W PEP. Good luck running 800W through it.

Load your balanced 40 meter dipole up on 20 using the MFJ.
Take the top off the MFJ for 3 reasons.
To see the balun inside, increase the Q of the coil and to watch for arcs when turning up the power.

My error. The model number of my tuner is not MFJ 969, it is MJF 986. I misread the small lettering.

73s geo

Yea, unfortunately.

The proximity from the top of the TV mast to the nearby hydro lines, CATV lines, phone lines, it is much closer than I care for.

I fear the E field off the ends of a full 20m dipole would affect and carry through the village along those medium at 800W output and I would generate all manner of RFI and TVI in that manner.

It already happened once before when I had the end of a 20m inverted Vee too physically close to the house-bound CATV coax, just on 120W PEP.

I've installed a LP filter and that helped an awful lot of course, but if I increase power to 800W, I need the aid of distance in every respect to ensure that my transmissions do not impose such a strong field upon village communication and power infrastructure.

73s geo

Geo, you have a tower and a rotor, its begging for a rotatable antenna. I still like the MOXON ant. concept. If that is to ugly, then a rotary dipole on 20 M. Again, you can shorten the elements to 10 feet if center loaded. However, its better not to and in that case you can re-cycle your TV antenna. Get the elements off it and use them as extended tips for the 10 foot conduit. Conduit is slit with hacksaw and use hose clamps to secure. Per a prior post, if you can find inexpensive Aluminum, great! Otherwise the electrical conduit at 20 feet overall is not heavy even after mounting it on 2x2 - 4 foot length as shown in 63 ARRL Hdbk for the 15 meter rotary dipole. I can copy and post that page if desired. For the 15 meter unit the L- was 4 " 1 " copper 1/8 inch tubing for the loading coil. I figured 5 uh is needed for 20 meters. You can build the thing in an afternoon, place it up on a 7-10 foot step ladder, tune it, and put your RX on it. Then take a listen on 20 M... get a feel for the directivity. If you have a higher step ladder, so much the better, ideally its fiberglass.  

Alan
W4AMV

I have enough RG/6 to do this and this idea is something that has crossed my mind a number of times!

73s geo

Constructing a stand alone item such as a Moxon, to withstand the high winds we have here at times, the snow, I do not believe I could do this successfully. There are too many devils in the details which can go wrong given a good gust of wind and a dumping of snow/freezing rain. Mechanical simplicity serves me best here and a dipole fits that bill.

The biggest hurdle I'm finding is that I cannot find any local sources for Fiberglass pole or some other strong lightweight non conductive material which is suitable for dipole construction.

I looked at PVC pipe and just a 10ft. length of it, held in the middle, sags alarmingly. I wouldn't dream of putting 25+ feet up on top of a TV mast.

I have been communicating with a fellow who owns Maple Leaf communications (http://www.mapleleafcom.com/), about 1 hour north of me. With his help, I may be able to find materials which are proper enough for durable construction and can withstand the Rf power I plan to put through it.

73s geo

I agree. If you can handle the length than for 20 M I would try a ZEPP in lieu of the dipole. OTH, simple dipole is fine and even better as a flat top as opposed to inv Vee. The tower you have serves as a center support for the VEE apex, so that may be your best bet. Also, it would be neat to put up 2-VEEs for 20 M that are at right angles to each other, than switch betweem them for some directivity/diversity. I would use separate feeds for both and place one of the VEEs say 10 feet below the other. Make the wire BLACK in color and the insulators and feed BLACK and it is very hard to see! Unless it snows!  :)

QSL.

73s geo

As I said in one of several previous threads on roughly the same topic, get two 20 meter ham sticks (they're roughly 100 inches long), a dipole mast mounted bracket (to screw both ham sticks into), a small TV-type rotor, feed it with your coax, and you got yourself a rotatable 20 meter antenna. It's simple, neat, doesn't look ugly, and saves a lot of screwing around and running around trying to design and fabricate something from scratch.

Yea, the only problem I encountered unfortunately is that the ham sticks (whip antennas) were all loaded types with a max. power rating of typically 300W. The limitation on their power rating is apparently due to the max. voltage that the loading coil can withstand. Apparently these can develop corona when over powered.

It's a shame because it really IS an IDEAL solution!

There's just nothing out there in the form of a whip antenna that is really designed to handle higher power. I've asked other store owners who I can find on-line as well (even on evilBay) and they all say the same thing.

Tomorrow I'll head up to Maple Leaf Communication, north of me, and see what they have in terms of building material for antennae. Hopefully he may have some fiberglass poles?

Even if I reuse the boom from the Yagi, I would still love to find a pair of 16 ft fiberglass poles which I could then mount onto the boom, thread some number 14 insulated wire on them, attach the Coax and call it Macaroni!

73s,
geo

You allready have the tower up. Why not just put a 3 element tribander up. It is a little narrower than a 20m dipole and you can tell the neighbors that it is a big high performance TV antenna. They dont look all that big when they are up on the tower.

Now you have 3 bands covered. Hang a 40m wire dipole off of the tower and you got the bull by the horn.................

screw the neighbors.  if you let them control what you do on your own property you'll never have a decent antenna.

Put up a quad.  2 el. has smaller turning radius than beam and works better at low heights.  you could even hang a horizontal one wave 20m. loop off your tower.   affix an X of fishing poles, each one 11 feet long to the tower top, so you have two cross pieces 22 feet long at right angles to each other.   string wire from one tip to the next to make the loop.   Should be 66 feet total lenth of wire.   feed at the corner or in the middle of one side.   Balanced antenna so you can use balanced feedline.   Get a 275 w. Johnson matchbox.   It will handle your 800 w. no problem.  Now you got an antenna for 20 15 10 and probably 17.   my 20 m. center fed dipole works on 17 FB with my KW matchbox and ladder line.     you now can work in all directions on 20 without having to have a rotator and you got a multiband antenna.   stubs, traps, loading coils, all that sh**t suck.   I won't even comment on that thing with the spiral elements. ::)

In the real world, I can't do that. TVI and RFI are real issues and any self respecting ham would do his or her best to prevent that from becoming an issue. It's also the law.



A 2 element antenna isn't out of the question! I have to weigh cost and availability of materials in my area and size against how close I am to village utilities.

But I can't and won't ignore the concerns of community and family. They don't want the neighbourhood looking like a frankenstein lab experiment, and neither do I. I'm convinced this can be done and still look like it can fit in a village suburban setting, that's why it's worth exploring.

73s geo VE3GZB

Geo,
Looking at the picture of your QTH you could put up one of these.............

http://www.eham.net/reviews/detail/340

There seems to be many happy with this one, if you are interested in the 'upper bands' only. I would personally get one and shitcan my A3S and buy a rotatable 40M dipole .........The A3S is  not the construction it used to be. Money is not like it used to be for me and Ham radio.....maybe you too......dunno

The spacing of houses in your 'hood' looks pretty spacious and you should not have any neighbor problems UNLESS you live in a HOA situation..........(Home-owner's Association)

Fred

The TAK antenna looked like outer space Area 51 stuff, but a nice winner antenna for 40M

Sweet!! But the price is out of my reach. Such is life. We either have time, or money. Some of us have not enough of either!

73s geo

ask bob morton when you see him, about the TGM mini-quad, from stratford..about the size of a t.v. antenna...

..sk..

   Good to hear one ham that puts family first! Could be like this guy:

http://www.youtube.com/watch?v=O7kirdtdI1c

Jim
WD5JKO

Went to see Bob at Maple Leaf Communications today, great guy, LOTS of stuff!!

We talked about different designs and we decided that for my space limitations and performance needs, a variation on a "Slinky" style of dipole would suit me.

Something like this:

http://www.nonstopsystems.com/radio/frank_radio_antenna.htm

I got from him Three lengths of military surplus fiberglass poles, 8' long each, some various diameters of short lengths of aluminum tube, some connectors and U clamps.

Yvonne and I got back home this afternoon and while she enjoyed the beautiful weather outdoors today under my watchful eye, I was busy in the driveway putting the antenna together. I'm using marine epoxy within the aluminum tube to provide chemical contact with the Three X 8' lengths of fiberglass pole, using external clamps around the aluminum tube to provide tension against the fiberglass poles.

I have to make a mounting plate, for that I can get a piece of scrap steel from the farm. I'm using along the fiberglass poles a parallel pair of my favourite wire, speaker wire, coiled every 5", held on with nylon tie wraps and outdoor RTV silicone.

To relive sag on the dipole, I'm going to extend the mounting post to which it will be mounted and I'm going to fasten some strands of 40 pound fishing line from the top of the mounting post to the mid section of each "arm" of the dipole, just to relieve sag.

I've wound more wire than I need on the antenna and I'm going to tune it by placing it up on the deck in the back yard, connecting it up to my antenna measuring device and I'm going to simply measure and snip until I get it close to resonating at 14.2Mhz.

I'm still going to use speaker wire for my transmission line, I've decided that is the best resource I can call upon to give me a balanced transmission line in my budget that matches the antenna relatively closely. Besides, I know it works.

I'll watch how it goes up and how it weathers in this windy, climate with the hot hots and the cold colds, and see how well it bears.

73s geo VE3GZB

..gud luk geo...all this messing around, wont werk..best you should have gotten a light bulb and put that up there...why ask, when you dont take advice from the guys who have done this, fer 40,50, 60 yrs?...i guess next is something like a square wheel... geez...the guys here are the best, and you wont read/listen to what they suggest...and btw, it is not illegal to get into other folks tv, audio etc...who told you this?..it is their fault, if your station is clean, but again what do i know...only had my ticket since august 26, 1975...when there was a real exam...10 wpm cw receive and transmit, plus written theory, and knowing the federal radio act...no a/b/c/d crap...

...sk..

  ( that means signing clear, in CW)...
..and further, if you are not an advanced class ham in canada, you are not permitted to work on any transmitter, or have an rf output beyond 560 watts p.e.p. ..i'll look you up, and see...



..sk..

There's no need for such bitterness.

I have to work within what I can afford, work within what materials are available to me in my area - because shipping costs will eat up the budget too quickly - and I have to work within the space I have.

I cannot put up a full length dipole for 20m because I don't have the linear space from my tower to the power lines, and I don't believe I have the necessary antenna construction materials and experience for a first time tower antenna project to put up something more complex like a Moxon design and expect it to remain up, in one functioning piece.

There are too many points in the practical construction of a Moxon which depend on maintaining fairly constant dimensions relative to other components, something that is not so easy to maintain up on a tower in a high wind.

After all, the last thing anyone wants is to wake up after a rain or wind storm at night and see pieces of their antenna in their neighbour's window or car windsheld.

I explored different ideas presented here, I weighed them against what would fit here and what I can afford and I brought these ideas to Bob at Maple Leaf Communications, who is also a ham and has a wonderful array of antennas on his property. We discussed which would be most practical based on what materials I could afford in my budget and a short dipole is what we ended up agreeing upon.

73s geo VE3GZB

geo, you are right, and i apologize...you want wire?..tell me...i've got miles of the stuff... i was thru grand valley twice on friday...might be thru there next week...i'll drop it off..you dont need to be there, i'll just leave it on your porch, or whatever...how about a half wave, dipole for 20, coax fed, as a sloper?...off the top of your tower, running at a 45* angle, facing into europe?..

..sk..

Geo,

Your idea of winding helical linear coils onto the fiberglass poles will work fine. It will give you a shortened 20M dipole as you desire and will have reasonable efficiency.

As for tying down the wire coils to the fiberglass rod, I would suggest using black electrical tape wound tightly over the wire.   Then spray it with a can of clear epoxy, the stuff you can find in any hardware store. This will seal it and keep out the rain.  

The tie wraps and RTV idea you mentioned above will break down and fall off within 5 years from UV and wind. Plus it is not as clean looking or smooth for wind.

Using the antenna analyzer will work fine to tune the coil lengths and then seal them off tightly with electrical tape and epoxy spray. There are other spray products that are good for the WX too.

* Be sure to tune the dipole at the center without using feedline. A short 3" temporary jumper coax is OK, but keep it short for 20M. Feedline will add errors in the initial tuning. The dipole center is the truth. Keep the ends away from objects and at least 10' off the ground when tuning it.

BTW, I think coax would be a better bet. Coil up about six turns at the feedpoint and this will prevent feedline radiation. Then you can tape the coax to the mast and run it anywhere.   You can connect the coax directly to the 50 ohm rig output with no tuners.

The problem with the speaker wire is it is balanced and sensitive to all objects. You will need to run it isolated an inch or so from all objects for the full run to the shack, just like the old TV twin lead days. Plus it will need a bal to unbal transformation at the rig. (tuner or balun)

I'm sure someone has some coax they can give you for the project.

Take a few pics and post them when you get it built.

Good luck.

T

  "  I'm sure someone has some coax they can give you for the project. '


I dont know 'bout u, but jest about any home i've been in has lots 'o cable tv coax in the cellar, basement, attick walls, etc.   U just gotta mine it, rip it out and use it... its all over the place, and FREE if you get it...


I ran zip cord fer a feeline, outdoors, fer a few years..... it werked; but appropriate feedlines will werk beter.

gud luck,

klc

..geo..i might be going thru grand valley this week...do you need some wire?..understand, i've been picking this stuff up for 40yrs, and i dont want anything for it...as a ham, if a guy needs something, tubes, antenna parts, wire, etc., and i dont need it, i pass it along to anyone who requires it...this comes back, in kind..some day i might need something, guys have helped me...it is an unusual group...there are guys who will take advantage of course, but by and large you will find guys are willing to just say "take it, you need it, i dont"...
..again, i drive thru grand valley often..you want/need some wire, just say the word...

..tim..

..sk..