Category: Ham Radio

Some months ago I’ve received from the local A.R.I. radio club an old antenna rotor. I think it is a Daiwa but there is no label on it. It looks like a Kenpro KR400 too… boh? It was used for many years on the roof of a local OM. It was covered with grease, dirt and many other “bleah” things.

First thing to do, I’ve cleaned it with turpetine. This powerful spirit clean up grease with ease and it smells really good to!

Second thing, open it and check it’s gears. To open it, simple uncrew the four screw on the bottom. It’s gear set is ok, no broken teeths, just a lot of dirty of old dark gray grease. I’ve carefully separed the aluminium ring that was screwed with the top alauminium enclosure.

It makes with the inner-bottom alluminium motor/gearset assembly, a bearing. Now, there are a lot of stell ball aroud.

I’ve collected the bearing’s balls, cleaned and left apart for future re-assembly. Separing the inner-bottom assembly from the top alluminium enclosure revealed that there is another bearing there. More steel balls to be cleaned…

Third thing, clean with soap the rotor spliced in: top alluminium enclosure, inner-bottom assembly and bottom alluminium ring.

Fourth thing, paint this three pieces with a strong synthetic paint, re assembly everything applying some grease on the ball bearing tracks.

 

 

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.

My military HF manpack radio PRC320, 3 months after I’ve bought it, started to make a whistle and was not able to tune on any frequency. After few minutes it went KO. No audio at all. Damn! How to fix it? Let’s take a look inside!

Opening the radio is an easy task:

• Disconect battery, antena connector and headset cables
• Unscrew all the allen screws
• Take apart gently, front and back pannels. They slide out the aluminium enclosure.

This is what I seen inside it

The Unit n° 5 is the first suspect. This module is the power supply. As a general rule in electronics servicing, check the power supply first! Let’s open it to verify if it’s doing it’s job.

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Now, with extreme care I’ve reconnected front and back pannel and powered the radio via its external power supply cable. After measuring the voltages on 6 and 112V points my suspects where confirmed. No way to have some power supply, there’s no output voltage. I’ve removed the module from the radio to troubleshoot it.

Repair that module is not an easy task because it’s semiconductors are all obsolete and hard to find parts. Still at the moment I don’t have a suitable replacement for TR1: the main 24V to 12V stabilizer, that fried. I’ve found also the BC107 on the step up section KO. Giving a chance to a BD139 in place of TR1 resulted in a semi funcional radio: I could listen to radio stations but i couldn’t transmit! Ok, let’s search for a complete new module! This is not a trivial task: this modules are very hard to find, I’ve found one new, serviced from a guy that does this job, radio servicing, during his military career, on ebay for 80€! It’s not cheap.

Now with this new module in place the radio comes to life again in RX and TX! Nice… but I have still to deal with the old broken module. I’ll update this post when I’ll fix it. At the moment this file could help you, Module 5 schematics