Most hams have probably never seen one of these SB-500 two meter transverters. No, I don’t have one (actually, I do have one but it will need to be refurbished), but I did have one back in the day. In the early 70’s the 2 meter ham band was still mostly AM (Johnson and Gonset radios come to mind – and of course the Heatkit lunchbox) but FM was on the rise (usually with converted low band land mobile radios). A few weak-signal fans were using CW. Pretty much nobody was using SSB, though, and when Heathkit introduced the SB-500 it did not create a firestorm of interest. It took in a signal from a ten meter (28MHz) transmitter and heterodyned it up to 2 meters (144 MHz), retaining whatever modulation was present. Then it transmitted the new signal. Anyone with a ten meter SSB transmitter could rig one of these to generate a two meter SSB signal. It was a turnkey setup if you had the SB-401 transmitter with which it was designed to mate. Like most, I wasn’t excited about it but approved of the idea in general.
That changed for me when Amsat-Oscar 6 was launched in 1972. This satellite, built by amateur radio enthusiasts, was in a low earth orbit similar to the weather satellites. One of the things it could do was to take in a span of spectrum (100KHz, I think) in the two meter band and translate the whole chunk down to ten meters and retransmit that span, including whatever signals were there. Thus, a whole group of people could be simultaneously using the system and each could be involved in his/her own conversation. That looked like fun! The satellite’s power budget was extremely limited, though. Only efficient modes of operation were permitted. This meant CW or SSB; I was equipped for neither on two meters.
I was using the Heathkit SB-301/401 on HF, though, so the SB-500 was a perfect solution. I managed to pick an SB-500 locally and after some work had it operational. I rigged omnidirectional antennas for the uplink and downlink frequencies and began listening. The satellite had an orbital period of around 110 minutes and an overhead pass lasted maybe 20 minutes. The inclination was such that I could usually hear two consecutive passes (three if the middle one was directly overhead). I used both CW and SSB and had many enjoyable contacts through Oscar 6.
While Oscar 6 was still operational, Oscar 7 was launched. It had new capabilities but still had the 2 meter/10 meter translator so my setup worked well with both satellites. I had a lot of fun with both. I shut down my “ground station” when I relocated and never got set up for satellite work again but kept up with happenings. Eventually the batteries on Oscar 6 failed so we were down to one satellite. Around 1980 Oscar 7 also went silent due to a battery failure. Nearly 20 years later, someone noticed that it was back up! A shorted battery had put it out of commission but when the battery eventually rotted away it left an open circuit and the solar panels could again power the system. There is no storage, of course, so when the satellite is in Earth’s shadow it shuts down but most of the time it is up and fully operational despite being over 40 years old!
Clearly, I need to rig something to listen for the 10 meter downlink. I suspect that when I have done so, I will get the bug to relive my experiences all those decades ago and actually use it. The good news is that it will be much easier to set up a 2 meter SSB/CW rig these days.