I found an old love and changed into a new love.
Cushcraft ATB-34
3 Element trap Yagi
About 30 Years ago I bought my first beam antenna. A cushcraft ATB-34 trap yagi for 20, 15 and 10m.
My reasons for the choice of the ATB-34 were: Not too largely and good antenna gain on all bands. So
the element spacing was one of the points and that I can handle it over the roof of a 3 storage house on
the mainstreet.
Now in 2006 I had to administer an estate. There in the
garden I found the old ATB-34 on a mast. I am very happy it's coming
just in time, just before ordering a new one. And again after 30 Years the same reason for the choice. I moved into a small
village and the garden is too small for my KLM
KT34-XA Beam with 10m-boom length.
Up on the mast the ATB-34 looks great.
Wake up is coming by disassembling the antenna. Sure, abt. 30 Years up in the air it is
really not a new one. There is nothing
found that looks like stainless steel.
All is very red iron now! 30 Years ago, by assembling the antenna they used a kilo of
weather
resistant military outdoors grease.
Thank you very very much! We had no problem by loosening any nut from the thread of the
bolts.
But all looks devilish, see pictures 1-8
for
details.
Pic.1 Pic. 2
Pic. 3 Pic. 4
Pic. 5 Pic. 6
Pic. 7 Pic. 8
Is that all rubbish?? I can't
belief what I saw. The boom has deep dent marks (Pic. 4-5-8). By fixing the element
mounting plates with the U-Bolts on the boom they screwed down the nuts so strongly that
the boom deformed more than visible. Also I found that the mounting plate of the driven
element is interchanged with one of the others. The distance of the drill holes for the
U-Bolts are too short, because for
the driven
element (see pic.6) are larger U-Bolts to use than for the reflector or director element.
The next mistake
I found are the drilled connection points trough the driven element. Loose connection of the
feed points in the live time of the antenna must have been a problem. That can be the reason for
the differences in the metric adjustment of the element lengths, other than the given
values in the Cushcraft manual.
Assumption: Depending on the
bad connection of the feed line they tried to find better SWR in readjusting the element
lengths.
What do we learn from it? 1. We have to do "RFIM" and again and again "RFIM"! (read fu.......ing instruction manual) 2. Use professional tools or semi professional tools. If you miss it, borrow it from your neighbour. 3. If you do things for the first time, ask experts before doing.
Please please do so! Might bee I like to pick up another 2nd hand beam in a few years. |
Is it better to buy a new one? Don't worry. Lets look to find some most advanced technological aid, like we have on board.
Abrasive paper different graining, 180 and 240 for pre and fine polish of the element tubes. Is that really necessary?
I don't know, but it looks much better and I like to
have a new antenna. Some other tools are helpful and will find in all houses.
Before the manual work begins, we should order all parts that must be replaced. I have myself decided to order all parts in
stainless steel quality, like it is the standard by new antennas. Not really necessary, the old clamps had been good for 30 Years.
If the reworked antenna will work again 30
Years I am 92 Years old, so god will. Hope I am not the last radio ham in 2036!
Lets go now - DX is waiting - Well done! Looks like a new one.
old after polishing
Important is polishing all parts inside
and outside where we telescoping the element tubes. We need
excellent low transition resistance through all the element tapering.
Before telescoping the element tubes use conductive paste. A thin coating on the end of the inner tube is effctual.
Long time low transition resistance will occur. Through the element slit you can see the copper paste.
And now the traps!
.....go page 2 ==> AB-34