[TowerTalk] SteppIR and SO2R

[Dick Green WC1M]

I've been running SO2R for about 19 years, and I've had one or more SteppIR antennas for the last 15 years. Some of my experiences might be helpful.

You've received many replies on this, and I agree with the consensus that you can't do effective SO2R with a single SteppIR because the tuning time is way too long. You can't even do effective SO2R with a single Acom 2000a because its  tuning time, which is way faster than the SteppIR, is too slow for SO2R band switching (I have a 2000a and an Alpha 87A.)

I faced a similar problem back when my only tower was a U.S. Tower 72' motorized rotating tubular crankup. I had a TH-7 on it, which was already the max load (or more) and there was no way the tower could handle a second antenna. I ended up putting a small tribander, a Force-12 C3E, on a 48' AB-577 military surplus crankup mast about 200 feet away, and running separate feedlines to the shack. This worked very well, though I had to build a somewhat complicated switch box in order to get maximum flexibility -- i.e., any antenna to any radio. It had to deal with the TH-7, which was one of up to 6 antennas on an SO2R 2x6 switching system (also had a 160/80 trapped vee in the trees, an 80m delta loop in the trees, and a 40m 4-square), as well as the additional feedline from the C3E. Initially it was driven by band decoders on each radio, not with a CAT interface.

When I got my first 4-el SteppIR, I put it on the AB-577. It can handle the load, but it's tricky to erect a load that big and it required multiple people to hold the guys while the mast was raised. A 3-El would be quite a bit easier. Not sure about the DB-18, with its double trombones. I left the AB-577 up all the time, but I could have cranked it down if necessary to please the neighbors (none of my neighbors can see my antennas.) I had to build another interface box to allow either radio to talk to the SteppIR because the two radios were from different manufacturers and used different CAT protocols. I used a PIC microprocessor to translate the CAT commands from the radio on the SteppIR to the SteppIR controller protocol.

This worked well for a few years, but every time I wanted to make a change to the antenna config I had to rewire or otherwise modify the antenna switch box. It became a box of spaghetti on top of relays and semiconductors. I ended up writing a PC-based antenna switching program called AntennaMaster, which uses a computer-connected relay control box to switch the many antenna relays in my station. It interfaces with the contest logging software (Writelog, N1MM or WinTest) to get the rig frequencies and other info, and uses that to tune the SteppIR(s) and do other tasks like controlling my many antenna rotators.

Writing AntennaMaster was a good move because about 12 years ago I built a 110-foot tower with a 3-stack of 4-el SteppIRs, and a 40m monobander. Later I moved the 160/80 trapped vee to it, and put a 10m monobander on top. It has its own 2x6 SO2R switch box, which makes the switching even more complicated. Never could have done it with a hardware switch box. I have a MicroHam stackmatch that allows me to assign two antennas in the stack to one radio and the remaining antenna to the other radio. AntennaMaster deals with tuning all three controllers as needed, though most of the time I don't split the stack like that because I have a bunch of secondary antennas on the old 2x6 box that I use on the second radio: a 20m monobander on the tubular crankup, a 15m monobander and a C3E on a pair of AB-577s, the 4-square and the delta loop. Also have the 40m and 10m monobanders on the tower and a Beverage for RX.

My point in telling you all this is that once you get sucked into SO2R, you may come down with a disease known as  EEHRSS: Ever-Expanding Ham Radio Station Syndrome!

[Note: I haven't made AntennaMaster generally available because I don't have time to support it. N3RS is the only other user. I'd consider making it open source, but haven't spent time exploring that option.]

Now, with all that said, it's certainly possible to run two radios on a single tribander simultaneously. We did that in WRTC2014 (I was on the Board of Directors for that), and I'm sure something similar was done in previous WRTCs and WRTC2018. We used a triplexer. Also, I believe there are tribanders out there with multiple feedlines (Optibeam?) You would need some good filtering for isolation to do that.

A better option, if you have the room, would be to use an AB-577 or similar mast with a second antenna -- a tribander or a SteppIR. Or build a second crankup (see EEHRSS above.)

While I always want to have the most effective antennas possible, especially on the run radio, you don't necessarily need a lot of antenna or power on the second radio. When I first started doing SO2R, 100W to a dipole worked OK. So a small tribander with high power would be more than adequate. If you build flexibility into the system, as I did, you can always switch the second radio to your better antenna and use the lesser antenna on the run radio to hold your frequency.

Hope this helps.

73, Dick WC1M