The AM Forum

I recently upgraded my antenna systems with a Tennadyne T-8 LPA to replace my old KLM KT-34A which was about 25 years old. After assembly of the T-8 I realized I needed to make some modification to it for better mechanical strength and better electrical connections. The boom comes in 3 sections and is held together with an insert and a few self tapping screws, not acceptable in my book, I felt these were points of failure, so I welded all the joints and plug welded all the screw holes for better strength and electrical conductivity. The elements attached to the boom were also a problem being held by only one screw passing through the boom holding the element in place. I removed the screws and welded the elements to the boom on both sides and again plug welded all the screws holes. For added strength at the boom, I made 12" long inserts for each element to relieve some of the stress at the joints where the elements pass through the boom. You can see in the pictures where I did the welding and mods.

This is the completed antenna on milk crates waiting to be installed on the tower. I fed the T-8 with hardline and Belden 8214 for the flexible jumper. I also moved the balun which was supposed to be installed at the fed point to the mast mounting point because I felt that with the coax running along the bottom of the boom, addition voltages could develop on the feedline Also The center mounting insulator seemed to me to be to small for the size and weight of the antenna, so I machine a new center insulator out of a block of PVC and made it about twice the size of the original. The second picture show the antenna at the top of the tower with a homebrew 6 meter beam, KLM 13 element 2 meter beam and a 2/440 vertical at the top. All being fed with hardlind. I have had great performance with the T-8 and have made alot of DX contact.....I am really happy I went with a LPA.

Nice looking welds Joe. It looks like TIG or your a real hotshot MIG welder. Where is the spatter?  ;D
I'm sure you will have many years of great performance!

Mike

Pretty slick, Joe.  First class installation.

You and I have been talking about these plans for a few years now.  Looks like you reinforced it to handle any ice load.  Frank/ GFZ and Chuck/ KW have done similar mods and both arrays are still up.

Have fun on the higher bands, OM.

T

I was going to ask you this Joe the last time we talked, but it slipped my mind. With the parallel boom arrangement of the LPA, if you had a "severe" rain, snow, ice event, would the performance of the antenna be compromised if any of this moisture, especially ice and snow, accumulated between the booms (i.e. possible bridging).

Hey Pete, so far I can say that I haven't had any problems with ice bridging between the booms or rain degrading the performance. That was one of my concerns when I was first looking at the design. 

I can picture snow on the top boom; starts to melt; starts dripping to lower boom; temps drop; icicles form between top and bottom boom. These antennas are made in Michigan where winters can be harsh, so I suspect they've determined it's not an issue.

Joe,
What do the booms have for vents and/or drains? I presume the ends are open?

Mike

Joe,

It looks great! I have no doubt I'll hear your back-scatter signal on 15 meter AM very soon! Let me know when you have everything cleaned up and done and I will schedule you for some work at my place.

Rob

Mike, yes the end are open for drainage and venting, the only thing bad about that is the birds and bees can build nests in there.

Rob, I've been on 15 AM with my 32V3 and 75A3 and I have heard you on back scatter several times. Of course I heard the stations you were talking to. I tried turning my ant towards you but couldn't hear you direct.

How about screens to allow venting but keep the critters away?

By the way, nice welding job!

Eric

Best way to feed a LPA is to have the feed line running through the bottom boom and exiting the rear of the boom and then free hanging to the mast.  This may not always be possible, depends on how the antenna is made.  I used this method on my HB 6 meter LPA beam.  I also did this when I installed commercial grade Jerrold LP TV antennas.

Interesting that you upgraded the center insulating block,  doesn't hurt.  I once had a big heavy LP TV antenna blow off the mast when the center insulator failed.  This happened at a hospital.  The manager asked me if I had the replacement part in my truck. LOL, I told him the only way to get the insulator was to make one.  Using 1/2" plexiglass (they had some in their shop) and their drill press, I made a new one in about an hour.

Joe, great looking antennas and nice job on the welding.  Should give you many years of trouble free service.

Fred

An LPA is a dream antenna to me.
Fred

Antenna looks great Joe.  I am sure you will have lots of fun with it. 

What kind of tower and rotor are you using?  I can't tell from the  photo's.

Joe, GMS

FB skyhook. And it certainly worked well aimed this way : )

Hey Joe....The tower is just a Rohn 25 at 65 feet guyed. The rotor I went with was a ProSisTel Big Boy PST-51 double worn gear drive DC motor, Italian made unit. I have to tell you, I was always a Tail-twister or Ham-M guy and swore by them, but I never liked the amount of play in them (sometimes 4 or 5 degrees) They were very noisy ( I could hear them run inside my shack) and the wedge brake made this tremendous clunk that made you turn your head.  The Big Boy is so quiet, I had to go outside to see if the antennas were turning, there is almost no play, and unlike the Hy-Gains, the Big Boy ramps up slowly so as to not mechanically shock the tower or antennas and then ramps down slowly to again not shock the structures. The overall construction of the Big Boys are far nicer than the Hy-gains also, the castings are really nice and heavy, all wiring sealed inside the housing, just been real happy with it. They are larger than the Hy-Gains and no rotor plate is available so I had to drill out one of the Rohn's.  Now why can't an American Manufacture like Hy-Gain make something just as nice?

Thanks for the details Joe.  That sounds like quite the rotor and something for me to keep in mind if I go to larger arrays.  I have always in the past put the rotor down near the ground to help keep the tower from twisting.  My new tower is an 82' crank-up so I will have to top mount it. 

Catch you on the air one of these days.

Joe, GMS

Joe,

Those Italian-made Big Boys are bad ass.  Good choice. I know of three in operation and they just work and work without problems.  You could turn a full size 75M rotary with the big one... and some do.


The next step up from what you have is a rotating tower.   If I knew back 15 years ago what I know now, I wud have gone with guyed, rotating towers. Wuda cost the same as the two 190' self supporters, maybe less.  [sigh...]

T

Hey Big T...you read my mind, I already purchased two T-10's that will get the same treatment as I did with the t-8 and the plan is in the future a rotating tower at 90 or 100 feet, Rohn 55 minimum and feed the two T-10's in phase. The T-8 was more of a trial for now.

Ah, so I see our trips to Chuck's QTH had the desired effect... ;D

BTW, I just realized you put these antennas up in the winter.  That's the mark of a commercial installer. When called, they don't care what season it is...

T


Pictured below, WA2PJP in April, 2011.  At a more innocent time ... before wild dreams of stacked logs and 10-20M whirlwide dominance:

Heh. Chuck and Tom both told me I should put up some logs here last time we were on 75 together.

I'd have to remove the house and 3 neighbor's houses first.

Got a roll of old acid core solder for a counterpoise.

What was the diameter of the element inserts? How long? Aluminum or wooden dowel?

I just bought a used T8. Have yet to get it and learning a lot while I wait  :)