Chasing Three DXPeditions on 23cm EME

 May 30, 2025

The last few days have been very exciting. While I missed the MD/EA8DBM Isle of Man activity through my inattention, I did rebound and work Alex's MJ/EA8DBM Jersey Island operation. Alex rigged up a dish mount to the back of his van which works out really well until the wind blows too hard.  

MJ/EA8DBM operating from the tricked out van on batteries no less.  EA8DBM Photo. 

 The next dxpedition up was that of IS0/HB9COG on Sardinia by the dynamic duo of HB9COG and HB9CRQ. The boys were running with a 1.5M dish and 100 watts. That's a pretty small station for me, but I've learned to never pass up any dxpedition, especially with very experienced ops at the helm. It took three hours of chasing, but I finally got a decode, and then a complete contact. In the log!

Older picture, but same 1.5M dish of IS0/HB9COG.         HB9Q Photo

Last up was MU/EA8DBM. Alex took a ferry over to Guernseys Island for another DXCC operation. It seems his dish was finally giving it up after all the rain and wind, so his signal was way down. Alex heard me, but he could tell I was not hearing much back - he graciously switched to Q65-120D and we completed without drama. 

MU/EA8DBM dish looking more than a bit worn.     EA8DBM photo.

Q65-120D to the rescue once again. MU/EA8DBM logged.

23CM EME - Squeezing the Juice

May 25, 2025

The slew drive is a huge improvement, it just works to keep me fully struck by moonbeams. :-) 

After reading how LMR-400/LMR-600 cable deteriorates over time I replaced the very old and suspect LMR-400 jumper at the dish feed with a fresh length of LMR-600 Superflex. The SWR dropped to 1.2:1 and my TX signal was just a tad ( the correct technical term would be modicum) better. 

Fresh 7/8 inch hardline is on the way to replace the 15 year old LMR-600 main transmission line. The bank was kind enough to second mortgage the condo for it. A half db here, a half db there, and it starts to matter. 

On the receive side things just continue to work well. I'm still impressed by the OK1DFV septum feed - I'm pondering adding a choke ring. I worked ON4MU today who also has a 2.4M folding dish but just 150 watts on transmit. Q65-120D to the rescue.

Is the juice worth the squeeze? Sure, why not - the improvements I've made in the last two months have opened a another tier of stations to work - just now, while the moon was at perigee, In the last week I've added nineteen new stations for a total 23cm EME station count of 217.

 

ON4MU in the log. Click on image for hi-res

                                  

They'll Be Days Like This (Momma Said)

April 24, 2025

All the station improvements paid off this morning. I've been chasing the Galapagos Islands DXpediion of HD8G on 23cm EME for the last few days. It has been slow going, but finally it was Q65-120D to the rescue. Thanks to Bruce, PY2BS the HD8G EME op for his patience and skill. 

How I feel put to music!

A large part of moon bounce is tenacity!

The Galapagos side of the contact - folding 2.4M dish to folding 2.4M dish.

Testing the AG6EE 23cm Pre-Amp

 April 23, 2025

Now that I have my 23cm EME station back stable and tracking the moon tightly, it is time to see how the AG6EE pre-amp plays. Petr has packaged the pre-amp module, filters, isolation relay and a 50 ohm termination into a single package. A male N connector connects directly to the RX feed port doing away with any short stubs of coax.

Working several stations and shooting some sun noise figures shows me at least a 1.5db receive improvement over my current setup. When we have the next blue bird day here in Montana I'll breakout SpectraVue and do some better science. 

When13.8 vdc is supplied to the AG6EE pre-amp it goes into receive mode, remove the DC power and it drops into transmit mode switching the pre-amp's front end into a 50 ohm termination. 

When you hear KB2SA and his 1.9M dish in the speaker at -16 you know things are working. 

There is nothing wrong with the WD5AGO pre-amps I've been using for many years, but I have to run 2 inches of semi-flex coax ahead of the pre-amp to hook things up. That degrades the noise figure.  

It's all in one elegant package.

Slew Drive Part II

 April 21, 2025

While the slew drive itself functions perfectly, my tripod wasn't up to the task. Things were just too top heavy and unstable with 65 pounds (22 kg) of slew drive sitting at the apex. So I sketched out a drawing of what I needed and went off to visit the local welding/machine shop to throw some steel at the problem. 

It turned out quite well, especially after a few coats of green paint. The land I operate from is not my own, so to avoid having to dig and pour a concrete base I drove four 24 inch (61cm)  3/4" (19mm) diameter tent stakes through holes in the base to hold things in place. So far it looks to be a very big improvement over what I had.

Steel plate and schedule 40 pipe solve a lot of issues!

Big Boy Tracking - Slew Drive Time

 April 7, 2025

All this tariff nonsense made me realize that if I wanted a slew-drive now was the time to act before Chinese products prices went sky high. I checked with Paul, W2HRO at Sub-Lunar and he had stock on the 3 inch drives. Ship it!

I assembled the mount and used three M10 washers on each of the azimuth bolts as spacers to make sure nothing would bind. 

As usual there was the fun of figuring out how to marry it to my Green Heron RT-21 controller. It turns out the manufacturer ships these drives with various color codes for the wire connections and even different encoder pulse counts per 360 degrees. My particular unit had a pulse count of 35962 X2 and the wires were color coded as follows:

DC Motor +    Heavy Red
DC Motor -     Heavy Black
Hall A pulse     Blue
Ref. Voltage +    Brown
Ref. Voltage Return     Gray
Hall B not used     Orange  

Bench testing showed all was good and ready to go. However, lifting the 65 pounds (22kg) of slew-drive chest high to slip it onto the tripod mast was a full-focus challenge. Umph!

I have some shimming of the tripod to do to make it plumb and then we'll see if I can really track the moon within 0.1 degree. Thanks to Paul, W2HRO and Frank, KH6FA for sharing what I needed to know saving me hours of fiddling.

Getting ready to solder connectors in place and see if the motors move.

Not square, level, or plumb ... yet.

Telling PSTRotor the good news.

First RF - OK1DFC Lighweight Septum Feed

February 8, 2025

I was able to obtain a prototype of the new lightweight OK1DFC 23cm septum feed for the 2.4 meter W2HRO folding dish. Initial testing revealed a very significant improvement on receive as expected, and even a boost on transmit. With 400 watts at the feed my echoes are consistently averaging  -20.5 db near perigee. The dish with the patch feed was never better than -24 db. Bitter cold temperatures precluded too much testing or adjusting to find the exact focus sweet spot, never-the-less we have a winner!

Two representative contacts just past perigee: KB2SA (1.9m dish, 400 watts) -20/-20, W1FKF (2.0m dish, 400 watts) -21/-21.  

As a bonus the new feed is 24% lighter than the patch feed so mast deflection is not an issue.

More details here. Kudos to Bill, KB2SA for the concept, and Zdenek, OK1DFC for making it a reality!

Note that the W2HRO folding dishes have used two different mast diameters - originally 1.25 inches and currently 1.5 inches. If you order one of these feeds from OK1DFC be sure to let him know which diameter mount to 3D print for you.  

Made from 1mm sheet aluminum the OK1DFC septum feed is lightweight.

 

Echo testing near perigee, with 400 watts at the feed.

OK1DFC 23cm septum feed ready to mount. 1.184 kilograms or 2 pounds 9.7 ounces

Sweet Winter Sunshine

January 7, 2025

Shoveled a path from several snow storms and had a great EME session on 23cm.

Winter storms are a great time for amplifier building. Version 2.0 of a KISS amp.

The guts built around a W6PQL pallet - an easy 500 watts with 6 watts of drive..