In March I started looking for a 1.2m fibreglass dish as it was evident that the steel dish I was using for 10GHz would not be able to handle the extra weight of the SSPA and power supply mounted at the feed point. After making a few enquiries I found a Prodelin 1132 1.2m offset dish together with a feed arm. I also decided to change the lightweight patio stand used to mount the slew drive and dish for a stronger mount.

It’s been cold and bright for the last few days with good moon conditions so I setup the slew drive and dish outside to test moon tracking with the KN3G controller.

The first day was a bit frustrating. It took me a long time to get the dish pointed accurately at the sun and after calibrating azimuth and elevation I kept using the EEPROM Init button instead of the new EEPROM Save button that I had added. Eventually I got things working correctly and managed to track the moon for a while, receiving the DL0SHF beacon between -7dB and -13dB. A problem with my laptop charger meant that I had to stop tests earlier than planned.

I eventually got round to putting the KN3G controller into a case and have now completed some more bench tests. The controller has been configured with GPS, sun and moon tracking options so that once the Arduino sketch has been loaded it runs as a standalone unit, without the need for a PC or laptop. An unshielded 4 core cable is used for the motors and CAT8 S/FTP for the Hall sensor power and output. The cables are 15m long and so far I haven’t experienced any issues with detecting pulses.

Although it’s been a bit cold working in the garage over the last few days with the temperature close to 0°C, I’ve now completed the metal work for mounting the slew drive on a short stub mast.

The mast to bracket base plates I used for the 10GHz setup last year have been adapted for the dual axis slew drive. By installing the slew drive using M10 10mm spacers I have sufficient clearance between the two base plates for a full 360 deg. azimuth rotation.

The slew drive for the 10GHz offset dish arrived at the start of December and over the last few days I’ve been testing it on the bench with the KN3G controller I started working on in October.

The slew drive has two-channel Hall effect encoders built into each motor housing, one for azimuth positioning and one for elevation. Each sensor generates 2 pulses per revolution (ppr) on 2 channels but the KN3G controller just needs to use one channel. The motor reducer gear ratio is 575:1 and the slew drive gear ratio is 62:1 so there should be 575 x 62 x 2 ppr = 71300 pulses for a full 360 degree rotation of the slew drive. This is equivalent to 71300 / 360 = 198 pulses per degree, or 360 / 71300 = 0.00505 degrees per pulse.

For my first experiments on 10GHz I used a homebrew W1GHZ 10GHz transverter with a 432MHz IF. I recently bought a MKU 10 G5 transverter from Kuhne electronic (now part of Alaris Holdings) and plan to install it at the dish along with the DU3T LNA and Kuhne SSPA.

The transverter is small, measuring only 100 x 80 x 14mm, and has two 2.54mm pin headers, a 2 row 4 pin header for power and a 2 row 13 pin header for PTT, monitoring and frequency selection. I’m only planning to use a few of the control connections so I soldered the sockets provided to a double sided prototype board with some screw terminals.

I’ve taken part in various EME contests on 2m since 2015 and I’m very pleased to have secured 1st place in the 144MHz Category C Mixed Mode section of the 10th A.R.I. Italian EME Trophy 2024. A big thank you to the organisers and all the stations that took part, it’s always a very enjoyable contest.

During the ARRL EME Contest in August and September I was struggling to keep the dish pointed at the moon using manual methods, especially for azimith positioning. I did some research and came to the conclusion that a dual axis slew drive, normally used for solar tracking, was the way to go. These slew drives have been in use for a number of years by radio amateurs across the world to move dishes much larger than 1m offset dish, so a 3 inch model should fine. I ordered one directly from the manufacturer in China and whilst I wait for it to arrive I decided to build a KN3G controller using an Arduino Mega 2560 and Nextion 5-inch display.

Since conducting the receive tests on 10GHz during the ARRL EME Contest last month I’ve been busy finalising the sequencer and control circuits and started testing the amplifiers on the bench. I’m hoping to have transmit capability for the second leg of the contest in two weeks time.

Microwave amplifiers for amateur use, especially solid state ones, are a lot more expensive than HF and VHF amplifiers, a combination of lack of demand and high device prices. The W1GHZ transverter only outputs around +10dBm (1mW) so I need two stages to get to the +40dBm (10-12W) level, considered to be the minimum for EME when using a 1m dish. After considering whether to buy or build and a lot of searching I eventually settled on a driver amplifier from Rob, PA3GIE and a second-hand Kuhne unit for the final stage, purchased from Jac, PA3DZL.

The dish used for the 10GHz EME tests during the ARRL contest has been moved to the back garden where I have visibility of the moon from 80 deg. to 235 deg. azimuth when it’s at 25 - 30 deg. elevation or more. At the moment the centre of the dish is only 1.4m off the ground so I’ll gain a bit more moon visibility when I move it higher.