Mosley TA-33-JR-N WARC

My Teenage Mosley TA-33-JR-N WARC

My Mosley TA-33-JR-N WARC Multiband HF Yagi is going to be 14 years old next month. I’ve never had a single problem with this antenna. It has been installed on my roof tower since May 2004. I’ve worked the world with this “Junior” antenna!

Back in October 2016 I began seeing high SWR numbers and decided to go up on the roof and take a look. Here’s what I found:

Mosley TA-33-JR-N WARC
This is LMR-400 after 12 years in the Southern California sun

OK, before you say it, yes, this is Times Microwave (the genuine article). The outer jacket had disintegrated in the sun. I noticed the increased SWR after it had rained one day. Further, it had seemed to improve after a few days, and I reasoned this was because something had dried out.

Mosley TA-33-JR-N WARC
Feed point connection on the TA-33-JR-N WARC

I was concerned these bolts might not come out very easily. However, with some gentle taps they came right out. Some evidence of corrosion can be seen. When I installed this antenna in 2004, at the suggestion of one of my elmer’s at the time, I sprayed the elements and boom with Krylon ‘clear coat’ to help prevent corrosion. I think it was a sound decision, since the antenna still looks great overall considering its age.

Mosley TA-33-JR-N WARC
Of course, I had to replace the sun damaged feedline

Mosley TA-33-JR-N WARC – Coax Balun

At the suggestion of the fine folks at Mosley, I added a 6 inch (inside diameter) loop consisting of FIVE turns of the new LMR-400 Ultra Flex coax.

Mosley TA-33-JR-N WARC
The Mosley engineer told me to mount it on the boom close to the feedpoint.
Mosley TA-33-JR-N WARC
The patented Mosley Feed System

From the Mosley website:

COAX AND FEED SYSTEMS

Feed Systems – The Simpler, The Better…
Despite popular belief, linear radiators, normally employed in 2 and 3 element parasitic arrays, have a driving point impedance of close to 52 ohms when open at the center. To feed such a radiator it is only necessary to connect a 52 ohm line at this point to achieve the best possible match of line to antenna. However, because of certain design characteristics, some beam antennas require elaborate and, sometimes, unstable matching devices such as Gamma or T-Match systems or variations of these systems. Such devices are usually difficult to adjust and to maintain in adjustment when used in multi-band beams.
MOSLEY TRAP MASTER beams, however, are so designed as to not require any unwieldy matching arrangements. Mosley beams are fed by connecting the line directly to the open center of the radiator. Thus, an excellent match is achieved over the entire width of each Ham band resulting in extremely low SWR near resonant frequencies of each band and the ability to range from one end of the band to the other without excessive SWR. By eliminating such matching devices, MOSLEY TRAP MASTER beams provide their users with stable and dependable operation without the necessity of frequent trips to the roof or up the tower
to make readjustment.
Mosley TA-33-JR-N WARC
New coax in the harsh California sun!

The end result was well worth the bit of effort it took to add the coax balun. The antenna exhibits excellent SWR. The Mosley TA-33-JR-N WARC will be my main HF antenna for the foreseeable future, and certainly, for as long as I live at this QTH.

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Author: K6HR

Licensed since 1994. Active on HF / VHF / UHF / Satellite.

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