Mosley TA-33-JRN

I’m an ham radio operator since year 2008. I’ve started this hobby with simple and relatively cheap equipment: an FT757GX transceiver and a long wire with tuner. During this 11 years of activity mainly focused on HF bands, I’ve tryied to improve my radio station. At first I’ve changed the radio with a IC7000 then an FTDX2000 now I’m using an FDM-DUO SDR QRP transceiver and an FT897.

I’ve quickly realized that changing the radio changes absolutely nothing except it’s intrinsic ergonomicity. The key component of a radio station is the antenna! The first vertical antenna was an 12AVQ, a compromise that worked for many years. The first full sized dipole for the 20mt band, erected at 10mt from ground with 10 mt of free space around, was absolutely the best antenna I ever had! It was silent compared to the noisy long wire or the vertical antenna. Now I’ve changed my QTH from Fano to Gradara, a castle on a 62mt eight hill. Not bad considering that in Fano my old QTH was at sea level with hills around it.

With such a nice location what to put on the roof? A yagi beam antenna for sure! I’ve choosed the Mosley TA33JRN because it have a nice declared gain and it’s size and weight are within my cababilities of a single man putting it on the roof.

First, I’ve bolted two iron supports on the side of the center wall of my roof. This two supports are heavy, very well made. They are the type used from professional antenna installators. They can fix a 60mm diameter pole, they are bolted to the concrete with two wall fixing bolts 14mm diameter, 200mm long and they are separed from one to another with 1mt vertical spacing in order to improve weight load distribution on the concrete wall.

I’ve decided to make a 3 section telescoping pipe. The idea is to assemble the antenna atop the roof with the pole fully retracted then elongate it to the desired height. The first section is a 2mt long 60mm diameter extruded steel pipe with 5mm wall thickness. The second section is 50mm diameter extruded steel pipe with 4mm wall thickness and the last 2mt section is 42mm in diameter and 4mm in wall thickness.

I’ve insert each tube in the other for a 250mm lenght thenfor every insertion I’ve made three 10mm holes. Two, with a bolt soldered, is for quick blocking the pole. The second is for insert a long 8mm screw that block the section in position.

The complete, crude steel pipe, needs some kind of rust protection. I’ve painted it with zinc spry. It is sufficent to prevent corrosion.

Atop the last section, the one wich support the rotor, I’ve soldered four steel rings for guying.

For the rotor I’ve choosed an Yaesu G450. I’m not using a rotor cage because it’s datasheet say that my 0.49m2 antenna is well within it’s load capabilities. This rotor is very well made and doesn’t cost much… about 300€ The last 50 cm pole on the top of the rotor is an alluminium pipe of 50mm diameter and 6mm wall thickness. It supports the yagi antenna.

Last but not the last, I’ve used 4mm size Dyneema rope for guying the pole. This rope is specifically made for yatchs, it’s stronger than steel rope and is insensible to UV light, water and salt from the sea droplets. By the way I’m 1.5km far fom the Adriatic sea… I can see it from my roof.

Take a look at this video, it explains why Dyneema is better than steel cable.

Assembling the Mosley atop the roof procedeed flawless. I’ve assembled the boom first and secured it to the pole. Then, I’ve assembled and secured central dipole, reflector and director elements. They are long at maximum 8.5mt and they weight is within a kilogram… maybe a kilogram and half. Is easy to work with such light elements. I’m working in a telecom company here in Italy that is servicing telephone land lines. For me is a joke climb up a 12mt wood pole and change long (heavy) cables atop of it. If you are not so practic with working on elevated, dangerous places with big pipes/wires/exc… I suggest you to ask for the help of one or two persons. Security first!

One negative note about this antenna is the supplied assembly manual. It’s a joke! It’s completly useless. No complete assembly drawing, parts are listed but the bags that contains parts are not labelled… you must use your own imagination! This is not good! I’ve searched on the net and found some more complete (old) manual from Mosley. Looking at a complete drawing of the antenna helped me a lot.

Mosley_MP-33N_user          TA-33-JR_assembly_instructions        ta33jr

I’ve found this three files that helped me.

Author: l.i.papadopol