time for fixing the antenna

[Opcom]

Now that the weather has cooled off, I hope I can get the guys to climb the tower and find my antenna problem. Basically it used to resonate on the ham bands, 7160 was great. Now it 'looks' shorter and resonates at 8Mz, and has actually now has two resonances 100-200KC apart. Storm did that. Eyeballs close to the wires all the way up should show the trouble. I have not been on the air since this issue because it burns up the tuner. Probably something simple, like one side of the ladder line touching metal, or it being twisted to short up top and I can't see it. It is OWL all the way from the tuner to the ends of the dipole so there is nothing to be hidden. Hopefully Radio Candelstine will soon be back on the air, 7160 on your AM dial.

[kc4umo]

Good luck on fixing the antenna.  I need to do the same, broken element on one, rotator stuck on another. And wife want let me up the tower lol.

[Opcom]

Conclusion!

Yesterday two friends from the ham club came over and fixed the darn thing!

I can say that I don't know what I would have done without the help from the ham club. This is a fine example of "members from your ham club helping each other".

The trouble was found to be a short between the two wires of the open wire line, way up near the top.  This trouble has been there for two years, since a big storm in December 2013. I got by because it actually would work on 7160, a local informal AM net is held SAT and SUN at about 11AM-3PM, after which there is SSB activity. I didn't want to be a pest on the ham club for this but was later told I should have asked for help before and that it was expected to ask, that's what the club is for.

About this antenna and transmission line, as a refresher, It's the same "4-legged dipole" mentioned before. It's all made of the same OWL. The line is about a 1" spaced hard drawn copper arrangement with little plastic insulators of 1/4" diameter holding the line conductors spaced properly. It is of good uniform quality and trouble was not expected for many years.

So, about 1 FT down from the center insulator, one side of one insulator had come off the wire. The storm had been so severe that it twisted the antenna center insulator around and I suppose the tension and tangling broke the insulator off and the line became shorted there. I'd taken pictures with a zoom lens and used binoculars but could not see this problem 55 FT up.

The end result is that I was transmitting on a rectangular loop of wire 1" wide having a vertical section some 55' high with the 'dipole' as a bizarre top hat. This fed by the horizontal section (tower to shack) of some 25'. It was 'tunable' with great difficulty for 7160KC, and that was about it.

To fix it, the section of OWL going from the shack wall to the top of the tower was replaced with regular 450 Ohm window line.  Because this ant. has 4 legs and the tower is guyed, it took longer to lower it for fixing.

It took about 6 hours for the whole job, less an hour or so for lunch at CT's Real Deal Bar-B-Que which I highly recommend.

Once it was all done, the resonance was around 7050KC with less than a 2:1 SWR to the 50 Ohm source and a CW mans dream, but more to the point I was able to match this using a 1:1 balun and a tuner to the usual 80M and other frequencies. On 80M it was pretty sharp tuning but that can be expected I think.

Before, I was burning up the balun and the 3KW MFJ tuner with the damaged antenna & SWR >25:1.  The picture shows what we found, where the short was.

[Steve - K4HX]

Mystery solved! Glad you got it fixed Patrick.

[flintstone mop]

You must have a lot of patience to put up with something that you can not deal with.
I am in a similar boat with an A3S Cushcraft 65 feet in the air on a utility pole, that I have no access to, unless hiring a crane truck ($500.00).  The Cushcrap antenna checks as an open circuit now and needs to come down for other intermittent issues. I'll just dump that crap antenna and mount a HEX beam on a smaller tower that will support the HEX about 35 feet high. That's enough to enjoy a Yagi type antenna with fair DX abilities. 60 feet was a dream........not now
Glad you have your station antenna back in service

Fred

[Opcom]

I have a huge amount of patience especially when I can't change something. The lack of access is because I can not climb the tower safely but the access problem has been fixed.

The guys from the ham club said I should have spoken up sooner and they didn't ask for a cent. It still took one guy to go up and look at it, and he saw the shorted spot, and also he removed some stand-offs that were anchoring the open wire feed to the tower. Only after that could it be lowered.

From now on it can be lowered by untying one leg of it. The pulley and rope are all in good shape. I need the 50FT tower because of my location, otherwise a 35FT might be OK.

The Cushcraft antennas have nice specs covering all those bands but are expensive and I have never liked antennas with clamped, screwed, or riveted connections, including butternuts and others like the R-8 and AR-270 verticals. There is always something to come off or maybe it is corrosion. If you get it down from the pole, perhaps welding those aluminum items in place since it's already tuned, might fix it once and for all.

Don't waste that pole.. get someone to climb it and chop off the cushcraft and mount you a short yardarm and pulley, and put up a dipole!

Or make a contraption. - some kind of close fitting rigid but easy sliding sleeve cage thing that can be pulled to the top into some rigid position maybe against brackets. - with a pulley and steel cable, and a shortest possible mast for the beam on it. another crazy idea for stuff.

Just hate to see you have to waste something you already made. Good luck on getting yours fixed up!

[flintstone mop]

I have a huge amount of patience especially when I can't change something. The lack of access is because I can not climb the tower safely but the access problem has been fixed.

The guys from the ham club said I should have spoken up sooner and they didn't ask for a cent. It still took one guy to go up and look at it, and he saw the shorted spot, and also he removed some stand-offs that were anchoring the open wire feed to the tower. Only after that could it be lowered.

From now on it can be lowered by untying one leg of it. The pulley and rope are all in good shape. I need the 50FT tower because of my location, otherwise a 35FT might be OK.

The Cushcraft antennas have nice specs covering all those bands but are expensive and I have never liked antennas with clamped, screwed, or riveted connections, including butternuts and others like the R-8 and AR-270 verticals. There is always something to come off or maybe it is corrosion. If you get it down from the pole, perhaps welding those aluminum items in place since it's already tuned, might fix it once and for all.

Don't waste that pole.. get someone to climb it and chop off the cushcraft and mount you a short yardarm and pulley, and put up a dipole!

Or make a contraption. - some kind of close fitting rigid but easy sliding sleeve cage thing that can be pulled to the top into some rigid position maybe against brackets. - with a pulley and steel cable, and a shortest possible mast for the beam on it. another crazy idea for stuff.

Just hate to see you have to waste something you already made. Good luck on getting yours fixed up!

OK Patrick
Most of your reply has already been done when we first moved here. There is a utility pole mounted arm for a dipole up there with marine grade pulley. That takes care of one end of a full length dipole for 160M, 65 feet high. The older yagis seemed to hold up better than the latest generation of yagis. I agree that riveted and hose clamp connections really suck for RF.
I have plans for a HEX beam and that will go on a lower tower. I'm not really a DX hound and do not want another antenna out of reach like the Cushcrap, especially those wire-y type hex beams. The later generation of these type of antennas seems to be better survival for ice and wind. Not as much gain or extreme F/B ratio as the Yagi, but a better antenna using less aluminum and crappy fitting RF connections.
I no longer have the time and excess money to create a HAZER type of system to raise and lower a Yagi on that pole.
It's one more time to rent a crane truck for its removal and by recycled, and ask them to look over the dipole arm and pulley,,,,maybe replace the pulley with another marine grade unit.

Fred

[N2DTS]

I bought a new Butternut antenna, the 80 and 40 meter version, about 40 feet tall, self supporting.
It was not new when I bought my house 27 years ago, I drove a pipe into the ground 10 feet from the property line and 12 feet away from some small white pine trees.
20 years later it was IN the pine trees but still worked as good as when I put it up (which was poor) it still had a low swr and was still standing, took it down and sold it at a fest, not a single problem with it EVER.

I can not say I ever had anything hold up like that, and it took all the power I could give it, about 700 watts carrier and maybe 3000 watts pep.

Was ok on 40 for DX, maybe ok on 80 DX, needed many more radials then I had room for so it made a good dummy load.
The quality was great though.

[Opcom]

That is the opposite of my findings with one I was called upon to remove. It came apart the wrong way so to speak. However I have no idea how it was treated in the 20 years it was there.

[Opcom]

So... How's the 160M thing work on this? if at all?

What is the real challenge for matching a dipole when each leg is 1/8 wave?  before I destroy something, best to ask?

[Steve - K4HX]

On 1.875 MHz, you'll have something like the following.

Feedpoint Z: 13 - j1340 Ohms

End of Feedline Z: 5.6 - j109 Ohms

Feedline Loss: 6 dB

[Opcom]

Thanks! looks easy to match but lots of power loss.

Would this be a text book case for the matcher being at the antenna end of the feedline? probably a rhetorical question in my case.

If the antenna is inefficient on 160M, then maybe the feedline length can be adjusted so the loss there is reduced. Would that help?

How can I see or calculate the feedline loss and see the results of changing the feedline length?  I should learn to do this.

[KD6VXI]

How can I see or calculate the feedline loss and see the results of changing the feedline length?  I should learn to do this.

Smith chart,  a calculator and dB loss chart.

Or mmana gal,  eznec,  4nec or nearly any other modeling program.

Seems Brian Beezely wrote dos based software years ago that would do it as well....   tl.exe maybe?

--Shane
KD6VXI

[KB2WIG]

P,

Any thought to shorting the feedlines together and loading it as a vertical?? Somewhere on the 'fone , someone ran a eL off of a tower, if I remember correctly. And then there is that shunt feed the tower madness.


klc

[Steve - K4HX]

Matching that impedance will take a hefty, low-loss tuner.

WIG has a good idea on shorting the feedline. This effectively turns the system into a top loaded vertical or T. I did the same thing at a previous QTH with good results. Stations beyond several hundred miles often noticed a large difference in signal strength when I switched the system from a dipole to a T. I put down 16 radials and tuned it with a C-L-C tuner.

There is no adjustment you can make to the feedline, other than making it much shorter or changing it out for a lower loss type (e.g. open wire).

You can perform online feedline calculations at the link below.

http://fermi.la.asu.edu/w9cf/tran/

[K1JJ]

I'll bet a pair of stacked Isotrons on 160M would do the trick.

Happy New Year everyone!   

T

[Opcom]

I've looked and looked at isotrons and see how they resonate but don't see how they radiate efficiently. There are a couple of  papers on it by a David Cuthbert WX7G. isotron.pdf and isotron2.pdf
One thing in there looks like a warning about power so, well.. that's it then! The 160M TX here is a BTA-250 so that's going to burn up the isotron.

Until the big tuner's done, no T setup. Presently there is about 15FT of transmission line from the wall to the MFJ 989 3KW tuner at the operating position. The good news at least the plan is to put the new tuner in a rack against the wall just under the ceramic tubes through which the transmission line wires exit. I should be able to get away with 1-2FT of exposed wire there.

[K1JJ]

I've looked and looked at isotrons and see how they resonate but don't see how they radiate efficiently.

Yep, you're right. A stack of 160M Isotrons  was meant as a HI HI HI HI HI FB FB HI HI HI joke. There are better small antenna methods.  Still, it's interesting as to how they work.

Here's a short thread that pretty well sums it up:

https://www.eham.net/ehamforum/smf/index.php?action=printpage;topic=73943.0

And a summary of what W7XG found in his tests:

"If you want to learn about Isotrons read my two part analysis (with field tests) of the Isotron in AntenneX magazine.

Bottom line is that the Isotron is an "antenna current excitation device" that excites antenna current on the "ground" wire and coaxial cable shield. These two items are the real antenna. As such the Isotron and wire can make a good antenna. But it can be hit-or-miss since almost no one realizes what they are really building.

I would not recommend the Isotron for your attic installation. It will excite RF current on the house AC wiring. A balanced antenna (dipole), as suggested by others here, might be the best solution. "

[Opcom]

I don't put antenna in the house any more but I would like a radio setup so I know when the AM guys are on. The data gear and alarm and video surveillance crap is all noisy and that wiring's like the old MIR station. I only have the radio and antennas in the shack. It could be worth it to put a 100W ham station in the house and run 50FT of coax to the shack, mount a vertical there with an automatic tuner at its base. I have an Alinco setup complete for that.. DX-70, the outdoor tuner, rigblaster for it, and a 23 FT marine vertical that came with a GSB-900DX.

Been frying other fish though:

Today I finally got COL Tucker back on the air with the fixed antenna. Had a nice long CCS-style Roundy with a few folks who were surprised enough that I was back.. A year off the air is a long time. The antenna was broken for 2 years but I forced it for a year on 7160 with a tuner and greatly reduced power to prevent balun-cooking. No other ham freq was possible at all. Just a fluke.

Now that its fixed, it's matchable with a simple 1:1 current balun after the tuner and the balun does not heat at 500W -proof enough it's fixed.

Speakin of 500W, it's been so long since I fired up COl Tucker that I'd forgot how touchy he is about output matching. The loading is by switching of capacitors in 100pF steps but otherwise it is a simple pi net with a roller. 

Just for fun here's the procedure. It may be amusing and is definitely some kind of hackery so it might make y'all laugh.

1.) Tune rig preliminarily with low drive for 200W or so into dummy load. (bypass through the MFJ989)

2.) Adjust MFJ tuner to match the dummy so the meter shows 1:1 SWR.
(For whatever unknown reason, through all the cables etc. the MC Jones dummy gives a 1.15:1 to 1.2:1 match. If I just tune to the dummy straight, and then match the dipole to SWR 1:1 as shown by the MFJ 989, COL Tucker tends to throw up all kinds of cat hair on the envelope. It's because he was matched to the off-kilter dummy load situation, then switched to a load of the proper Z)

3.) Tune COL Tucker fully up to the desired carrier power and tweek to make maximum clean sine wave modulation into the now-matched dummy load.
(with a 500W carrier the MFJs power meter may show 1000W with good modulation)

4.) Switch over to the antenna and adjust the MFJ for a 1:1 SWR, set peak power to compliance 

5.) Varmint, I'ma gonna blow ya to smithereenies! (I mean, call CQ40)

If anyone understands why all this haberdashery is needed - meaning the matching to the dummy load for getting the TX tuning right - I'd like to know it. As far as I understand the TX is just fussy. I did change out the cables, the dummy is 50 Ohms.

Despite the funny business I am real happy to be back on the air with the plate modulated transmitter!

[WD5JKO]

    Pat,

   Glad you are back on. I missed things yesterday since I have been traveling, but I am home now. Back to work tomorrow.

   The dummy load issue is not uncommon to me. My MFJ gallon bucket dummy load has about a 1.7:1 SWR when switched to. Over the years I have dumped a lot of power to it, and sometimes it got pretty darn hot. Those resistor(s) inside are not the same. At one point I was using an old Palomar engineers multi tap mobile antenna matcher to get the dummy load within 1.2:1 SWR.

    As to why COL Tucker is belching when loaded into a load other than 50 ohms resistive is not clear. Perhaps the big old COL is making a parasitic on modulation peaks? That might go back to circuit configuration, and neutralization. I'd try the COL on another band, perhaps 20m on 14330 tonight around 6:30 pm, or 3890 after dark. You might find this a band to band phenomenon. It could also be related to RF getting back into your audio chain as well.

Glad your back Pat!

Jim
WD5JKO