Kendall Amateur Radio Society

KB5TX


Club Activities

 

The LPA at K5NOF Fixed and Reinstalled

 

 

This is a 12 element Log Periodic Array manufactured in 2013 by M2 Communications in Fresno, California, mounted at 70 feet AGL at K5NOF.  Nominal gain is 5 dBd at 10 mHz up to 9 dBd at 30 mHz; not exactly a flame-thrower but close to it.  Find where the DX is listening and this antenna is a pile-up buster.

The M2 LPA 12 uses fiber glass rods to insulate the elements from the boom.  These rods pass through an element to boom clamp.  Metal elements are slipped onto the fiberglass rod, then the phasing line connections are placed on top and the entire assembly is bolted together through the fiberglass insulating rod.  The Texas ice storm of February 2021 placed enough weight on Element 5 (counting from rear to front) to break the fiberglass insulating rod.  You can see the elements hanging from the phasing lines.

Much has been written about mounting a large antenna on a tower.  Fortunately, our long time member and one of our directors, Marsh – WA5UBO is a skilled tower climber with all the necessary equipment to do the job safely. With the help of Don KI5AIU & Greg AB5I to be his ground crew.   He coordinated with Perry’s Crane Service, Kerrville, TX, and down the LPA came.  Once on the ground, it was decided to replace all the fiberglass insulating rods  because of deterioration through the years as well as the RG-213 feed line.

M2 could not have been more helpful.  This antenna had been out of production for a long time, so the fiberglass rods and the Element 5 hardware were manufactured from scratch and after a couple of months all was available to do the fix.  The fix took a while longer because we decided on a couple of “backyard modifications”  First to replace the old stainless-steel boom support lines with Phylistran, and secondly, add a third boom support line half way between the mast and the forward boom support line attachment point.

We had all ready to go up the tower, long before the weather would let us do it.  This antenna is BIG, weighing 75 pounds, with a boom length 45 feel and rear element length of 52 feet tip to tip.  Marsh – WA5UBO would look for a weather break, and when he saw a forecast for dry and calm WX, he would schedule the pick with Perry’s Crane of Kerrville, TX.  We had three false starts having to cancel due to weather. But no worries, Mr. Perry was great to work with and finally came the day, 6 May 2022.

Marsh and helpers, Don, KI5AIU and John, KK5ZRP arrived early to have all ready to go when the crane arrived.  It took 30 minutes for Mr. Perry to set up and deploy the Jib  boom with Don’s help.  Down came the hook to be connected to the boom straps fore and aft of the mast and to the mast itself, and up she went.

You can see the preliminary lift below left with Marsh up the tower in the background.  The idea here is to insure all is in balance; you can see it is.  So without further ado, the antenna, with new thrust bearing installed on the mast, was positioned directly over the tower thrust bearing plate where Marsh could guide it into the rotor connection, while the crane operator gently lowered it into the rotor seat. Then Marsh connected the thrust bearing, then connected the rotor, unhooked the crane cable and then removed the lifting straps from the beam. The final work here was to attach the coax for 360 degree rotation around the tower and waterproof same. But not done yet.

 
Marsh made a second climb up the west 70’ tower at K5NOF (40m 4el M2 Yagi) to reconnect a 400’ tower to tower hi-line used to support an OCFD (Windom) antenna.  Cargo straps were used to ratchet the line in place where it could be connected.  Don’t scoff at a Windom.  It needs a turner but is a “hot” multi-band antenna and the go-to antenna at K5NOF for general communication.

A final thanks to M2 Communications, Inc. in Fresno, CA for a great antenna and superb support.  The LPA-12 is no longer manufactured but their next generation of LPA’s are equally good.  If you want an antenna which ships with all the parts, and the connecting bolt holes line up, see www.m2inc.com for their great antenna line from HF to Satellite.  Finally, special thanks to KARS Members Marsh, Don, Greg and John.

 
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