LPDA Going Up Today!

[WA2OLZ]

The stars have aligned and my long awaited Tennadyne LPDA T8 should be resting comfortably atop the roof today!

It has been a long time coming, what with reading all I could find on the subject, building, checking, building again, waterproofing, bug & bird proofing, aligning strong young backs, priority family obligations and the weather (it is currently 26 degrees here). I have no tower (live next to a general aviation airport) so the antenna will be mounted on a piece of black galvanized pipe protruding through the roof. It should, hopefully, end up about ten feet or so above the peak of the roof.

I'm hoping the neighbor kid, a budding photographer, will be around to get some installation pictures. I'll post a few later on assuming it (and I) are still in one piece.

[flintstone mop]

get 'er up there before the real antenna WX starts....this is just the beginning!!!!!
Fred

[WA2OLZ]

You got it, Fred. My blood is definitely getting thinner as I age!

[W3GMS]

Putting antennas and towers up is a look of work with lots of planning.  I know you will reap the rewards once its up in the air. 

I am assembling the pieces to put my new to me used Heights crank up tilt over tower up.  Unfortunately with the other projects around here, it will have to wait until the spring. 

Joe, GMS   

[Steve - K4HX]

Nice antenna! You will have fun on the high bands.

[WA2OLZ]

One day delay in game penalty.

Winds went from calm to gusts over 30 Kts in no time flat! Hopefully tomorrow early morning will be better!

[WA2OLZ]

Pictures of installation. I was the guy on the ground on the other side of the camera
Second set of pics to follow

[K6IC]

Congratulations John.  The T-8  is a very good antenna.   A friend had one up for a number of years,  and worked all over the USA and made many DX contacts,  mostly barefoot.

Hope that you have  coax attached to it.  The upper bands have been quite good lately.  73  Have Fun,  Vic

[WA2OLZ]

Hopefully this, the final photo, will take

[Pete, WA2CWA]

Hopefully this, the final photo, will take

Notice just below the attachment box: Maximum attachment size allowed: 5000 KB, per post: 3

The one picture you attached was 4750 KB.
Lower the resolution of your pictures. They'll load faster and any one on dial-up or slow DSL won't P&M either that they take forever to load or won't load at all.

Here's one of my antenna pictures as a sample; it's only 36 KB.

[w1vtp]

Hopefully this, the final photo, will take

I commend you on your wish for good resolution.  Given the file size limitation for each post as established by the forum, there is a way to keep your resolution by compressing your JPGs without appreciable loss of detail.  Check the uploaded file.  The reduction in file size is by a factor of 10.  This is possible by a utility called "Irfanview" - it is freeware meaning there is no cost for personal home use. 

It was becoming a favorite of some at my facility at Raytheon as a means of reducing file size - the IT people saw the value in this and made a financial arrangement with the producers of the program for proper licensing of the program.

All you need to do is load a given file and save it at 50% compression.  I cannot see any degradition in your file after this file reduction.  Check it out - the picture size is the same as yours - I have uploaded it for your viewing

Al

[w1vtp]

Actually, to cut a fine point, a setting of 34 % yields a 10 times reduction in your file size.  Again, no appreciable reduction in detail

Al

[W3GMS]

Fantastic job on getting the antenna off the ground and on your pipe mast.  Looks good and now give us some feedback on how its performing!

Have fun....

Joe, GMS

[Steve - K4HX]

Nice ant OM!

[KA2DZT]

All the LP antennas I ever installed always had the coax running inside the lower boom section.  Your coax is attached to the outside of the lower section,  this can cause some unbalancing.  Is some cases the coax was attached near the front and then dropped on an angle to the mast.  Maybe non of this is possible with your antenna.

Wondering what the instructions recommend about this issue, if it is even mentioned?

Fred

[W3GMS]

All the LP antennas I ever installed always had the coax running inside the lower boom section.  Your coax is attached to the outside of the lower section,  this can cause some unbalancing.  Is some cases the coax was attached near the front and then dropped on an angle to the mast.  Maybe non of this is possible with your antenna.

Wondering what the instructions recommend about this issue, if it is even mentioned?

Fred

Fred,
I just got on the manufactures web site and you can see how they recommend routing the coax. 
Joe, GMS

[WA2OLZ]

A. Thanks to all for the advice about loading attachments. I appreciate it and will make sure they shrink a bunch from now on!

B. There is a LOT of controversy about the proper care and feeding for an LPDA, especially that from Tennadyne. After a whole bunch of reading I decided to go with the sage wisdom of K6ELQ. The issue boils down to this: The coax connects to the front (leading edge) of the antenna. The manufacturer places a standard 'Collins' balun at this point. The Coax then runs along the bottom boom to the mast. This causes the signal to again be coupled to the boom! In the K6ELQ solution, a second balun is placed on the mast, below the boom, so as to once again decouple. The coax never passes through the lower boom as the design precludes it doing so; the elements feed through the boom, taking up all the available space.
I am definitely not an engineer but the logic worked for me, so I went that way. There are numerous web posting from guys who used the single balun at the feedpoint and had horrendous SWR issues. At any rate - it worked great for me (<1:2) except for a small SWR bump on 17M where it pops up to 1.5:1 or so.

I'm going to try to attach the article by K6ELQ (at the risk of doing something wrong here too. The properties of the file say it is 2.33MB, so hopefully it will work OK.

BTW - I know this is straying rather far afield from A pure AM discussion. Please let me know if it is time to cease and desist!

[Pete, WA2CWA]

The Coax then runs along the bottom boom to the mast. This causes the signal to again be coupled to the boom! In the K6ELQ solution, a second balun is placed on the mast, below the boom, so as to once again decouple.!

Since both booms are active parts of the antenna, I would think running the coax along the bottom boom is not ideal. It might affect performance, resonance points, etc. I would have just attached a PL-259-type right angle connector to the end balun and then just drooped the coax over to the mast. But, maybe on HF it's less of a problem coupling the coax to the lower boom.

[WA2OLZ]

You are spot on, Pete. That has been proven to improve performance with a single balun. Coax along the lower boom definitely causes coupling issues. The reported issue with drooping coax is the propensity for the dangling coax to get windblown and tangled and/or cause varied performance as it gets blown about.

[Pete, WA2CWA]

Take a length of rope and tie it to the lower boom near the balun. Run the other end of rope at roughly a 45 degree angle and tie it to the mast. Make the rope taut. From the balun, loop the coax down to the rope roughly 1 foot below the antenna. Use plastic ties to hold the coax to the rope. May not be pretty, but it should work.

[W3GMS]

With the apparent problems with running the coax on the hot boom, why does the manufacture recommend that method?  You would think by now after making that beam for some time, they would have recommended something different.  I am sure they have received lots of phone calls about that scheme. 

The last time I used an LP was in the Army during the early 70's at Ft. Gorgon, GA.  I all remember is a tower section was used as a boom and it went down to 40M and worked excellent.  I have no recollection on how the coax was run on that beast but probably inside the tower / boom section. 

Joe, GMS

[WA2OLZ]

The original owners of Tennadyne said they never tried toroidal baluns and therefore could not recommend them. The new owner is far more customer oriented, builds a much more mechanically reliable antenna and..... wait for it ..... has never, so far as I know, spoke up about it one way or the other.

Like most facets of our hobby, there is likely no single 'correct' answer. My extraordinarily brief experience indicates the dual balun solution is working FB.

With a lot of help from guys here who know what the are doing I got the following photo down from 5MB to 500KB. Nota s small as some others, but a sizeable reduction

[KA2DZT]

Part of the theory with running the coax inside the LP boom is that there is no need for a balun as the boom decouples currents from running on the coax shield.  Getting the coax inside the boom is certainly not easily done.  The coax needs to be in the boom before the elements are attached.  BUT, the antenna needs to be designed in a way to allow this.

The coax would exit to rear of the boom and then dropped on an angle to the mast.  This causes the coax to be free dangling to the mast, another problem.  I think this method allows the antenna the best performance.

I'm thinking that a piece of tubing attached the the lower boom could have the coax run through it.  Never seen this done but I see no reason why it wouldn't work the same as running the coax in the boom.

Fred

[WA2OLZ]

Fred,

Would that apply to a dual hot-boom configuration as is the case with the Tennadyne?

[Pete, WA2CWA]

The balun provides a nice interface between the antenna and coax and also prevents RF currents from being propagated down the shield of the coax. However, it seems to me that if the coax coming out of the balun  is then strapped to the lower "RF hot" boom for a good 8 or 9 feet before it gets to the mast, the potential for RF propagating back onto the shield of the coax is high, which is something you don't want. If my rope idea didn't appeal to you, you can hang a length of PVC tubing (secure it with maybe, 2 or 3, three inch screws) below the lower boom and run your coax through that back to the mast.