Years ago, Bob Bruninga, WB4APR, talked about a “good” antenna for APRS SATCOM applications. It was a 19-inch vertical antenna that would function on both the 2m and 70cm bands, and had lobes that were up around the 30-degree mark. Looking for information on that antenna last night I found a page Bob had written expanding on the idea. This page provides designs for i-gate antennas on 2m and includes the 19-inch antenna as well as a new design, a 3/4-wave 2m antenna.
I’m seriously considering building one or both of these antennas this weekend to test out these antenna designs.
The Arrow Antenna for satellites has an optional diplexer that allows easy operation of 2m and 70cm from a single feedline. I’ve used this configuration for over ten years with no problems. I’m not sure, exactly, what happened but the diplexer failed. After ordering a new one I started digging into the hardware to see if I could see anything that was the matter.
Looks like one of the surface mount parts got a little warm. The picture does not show the hole that had melted through the shrink wrap but the bottom right component definitely got too hot. The solder is completely gone from one side which was definitely affecting the circuit. I’ll likely try to repair this even though I have a new one in service right now.
Yesterday I had a broken QSO with K9?H?. We were running CW and between the fading, the Doppler shift, and my poor CW skills I couldn’t quite get the full callsign and exchange. And then, of course, I was also chasing myself all over the transponder. This morning was completely different, however.
The pass of FO-29 was going to be high. Being that I’m still working on my antennas and not knowing what to expect I was just hoping to hear myself. Tuning around the center of the transponder I clearly heard N8HM calling CQ. I was able to find myself on the transponder and tune myself onto Paul’s frequency. To my surprise he heard me and we were able to have a somewhat broken QSO. I’m not hearing the downlink that strongly (clearly an antenna issue) but we were able to swap grid squares and have a short QSO. Turns out Paul is just up the road in DC making this perhaps the closest distance satellite contact I’ve had.
I need to go back through my logs but I think this may be my first FO-29 QSO. It is, at least, my first FO-29 QSO in many years.
I had a good pass of FO-29 this morning so I figured I’d give it a try with my 2m/70cm loop antenna. I wasn’t expecting great things as this is not a gain antenna and I’m not sure how much of the signal is actually radiated up but I figured I’d give it a shot. Turns out it does… okay. I never heard the beacon but I was able to find myself on CW. It’s been years since I operated a satellite much less a transponder satellite so I was having a hard time tracking for Doppler. I’ll have to hook up with my satellite Elmer, again, and make sure I’m tuning the correct side (do I try to stay in the same place on the satellite transponder by adjusting my uplink or do I try to chase my downlink through the transponder?).
Another observation is that the loop doesn’t do very well. I’m definitely getting into the satellite with ~10 watts but I’m not hearing the satellite that well. A preamp might help here but I suspect getting some proper antennas would as well.
Opened the mailbox this afternoon and found my QSL from Victor Cuesta YV4DYJ of whom I worked on AO-51 back in September. Very cool. Glad I was able to make this contact using 5 watts and my hand-held station in my front yard.
Things I need to purchase:
Things I need to do:
- Complete the construction of the 2.4GHz parabolic antenna.
- Mount the rotators and mast pipes.
- Mount antennas to mast pipes.
- Replace coax.
- Setup better power distribution using the RigRunner 4008 and battery backup using the Super Powergate 40S and AGM batteries.
- GROUND EVERYTHING!
- Have fun.
I just worked a pass on AO-16. Heck yeah it was early. But having the bird all to myself at 5:45 in the morning means I get to test my antennas without stepping on anyone else. I did work N8OQ but it wasn’t easy. And I’m not really sure which antenna I was using because they aren’t labelled. That’s going to be something on today’s to-do list.
Anyway, on whatever I’m using now, I was able to hear the bird much further to the south than I was to the north. I was still inside the footprint when I lost it so I’m not happy with it quite yet.
Things to do today:
- Figure out which coax goes to which antenna.
- Measure for new coax.
- Account for the rotators and get them cleaned up.
- Buy rotator cable.
- Work AO-51 passes.
Now comes the interesting part. How do I hold up my antennas so they can twist and turn as required? I don’t plan to be in the same location in two years so I don’t want to do anything permanent. I currently have a 30-foot pole up next to the house that has been attached near the top of the house for stabilization. I don’t know what kind of weight it can handle but I have been thinking about trying to mount the azimuth rotator to the top and then have a short piece of pipe hold the array up (including an elevation rotator. I wonder if anyone has ever done this.
The most important part to a radio station is the antennas. You could probably lump in the feedline as well but I think I have that figured out for the moment.
So what antennas do I already have and what do I need.
- 11-element 2m beam (single polarization, currently horizontal) – operational condition
- 24-element 70cm beam (single polarization) – needs minor repairs to get it operational
- M2 2MCP22 2m circular polarized yagi
- M2 436CP42 U/G circular polarized yagi
There really isn’t anything wrong with the 2m beam I currently have. But I want to have better. Since I already own it I’ll probably just stick with it until I have everything else covered. Why fix it if it isn’t broken.
The 70cm side of the house is another story. I don’t think my current antenna is appropriate for satellite operations. It is rather large and is going to be difficult to mount, turn, elevate, etc. I’m not sure of what it is worth but I might be able to sell it in order to pay towards a shiny new M2 antenna.
Of course M2 is quite proud of their work. The436CP42 U/G has a price tag of $420 for 16.8dBdc of gain and their 436CP30 is $357 with 14.15dBdc of gain. I’m not exactly sure which one I should look at. With a couple of HEO satellites in process of being launched I wonder what it will take to reach out and touch them reliably. I don’t want to have to use a pre-amp to receive the signals coming back to Earth as this sometimes causes more problems.
On the 2m side I’m facing the 2MCP22 at $360 for 12.25dBdc of gain or the 2MCP14 at $245 for 10.2dBdc of gain. Again, I want to be able to reach out and touch a HEO without the use of amplifiers or anything other than my 50-watts out of my TS-790A. Simplicity is best, I feel like.
Now this just covers a Mode B or Mode J system and nothing else. I think the 1.2 GHz and 2.4 GHz is going to be just as important as the 2m and 70cm side of the house but I also think that if I can base my operations in Mode B or Mode J then I can move on up from there.
I’m ready to take the next step. I have a set of azimuth and elevation rotators and I even have a 2M beam. I think it is time I get serious about my satellite operations. Not that I don’t have fun working the FM birds via my HT and an Arrow Antenna but I think it will be more fun to automate some of it and be able to work from the comfort of my chair inside.
Here is a list of things I need to buy, build, or gather:
- 2m and 70cm Antennas
- Antenna Support
- Rotator Control
- 1.2 GHz
- 2.4 GHz
I’ll try to cover in detail each of these items in later blog entries so I can keep track of what I want to do.