Figure 1: A TenTec Corsair II was recently added to the Shack’s radio table.
The oversaturated and underexposed large aperture time lapse photo of the new TenTec piece didn’t come out exactly the way I envisioned, but it’ll do for now. Attached to the camera was an old 35mm Pentax lens from somewhere in the 1960s or 1970s, because it seemed fitting to photograph an antique radio with an antique lens. Unfortunately, the particular antique lens I used was known to be a little more subject to flare than are the modern versions of lenses. So, the pic took on a funky look due to the odd lighting I found to be needed.
Really – the idea was to preface the top of the page with something interesting and eye catching, but not as hard on the eyes as it turned out to be. Sometimes dumb luck just doesn’t seem to work – even though in another life I had a photography hobby.
Figure 2 : The Corsair finds itself nestled in next to the Omni A, and under the Triton on my bench
When it comes to radios (not lenses) – I’m covering the late seventies and early eighties pretty well. The Triton IV (top left) heralds from 1976, while the Omni-A (middle bottom) comes out of 1979 like a blast from the past. The newest addition is the Corsair II (lower left) – which is a product of 1983. And the wonderful Alda 103 (top right) – accompanied the Omni-A on its trip out of 1979. These things all have a few things in common. For starters, they’re all (mostly) analog radios. And they’re all (mostly) made of discrete transistors.
Figure 3: A closer look at the Corsair II (left of photo). Click to enlarge
The first thing I did with the Corsair was to check the output voltage coming from the TenTec power supply that accompanied the radio. These old power supplies can suffer from shifted component values over the decades. It turned out that the TenTec power supply was putting out around 14.5 volts – a shade on the high side. I took the cover off, and ran the adjustment trimmer down to a more appropriate 13.8 volts. The previous owner had mentioned a little problem with the display not always working. I noticed this too – but the problem seemed to go away when the voltage was reduced.
It took a little while to get used to the Corsair II’s pass-band tuning and its other various selectivity features. Once I got the hang of them, I found that they’re pretty useful. I made the first QSO on thirty meters, and got a nice comment on the sound of my signal. This is pretty standard fare for TenTecs. While I’m obviously on a quest to find the best of the analog-based TenTecs, I’m not sure the Corsair II is the one. It’s able to pull pretty tiny signals out of the aether – with the PBT, notch, BP, and XTAL filters, no doubt. But, thus far I haven’t been able to “quiet” the receiver to the level I’ve grown accustomed to having in my ears while using the Omni-A radio. The Omni-A presents a signal without background rush, and is a wonderful thing for the ears. When tweaking the Corsair II’s controls, it seems there is always at least a small hint of “rush” in the sound of the received audio. It doesn’t quite get to the level of “quiet” that the slightly older Omni A does.
The Corsair’s built-in keyer let me dust off the old Bencher paddle and Autek keyer, which I’d mothballed quite a while ago in favor of TenTec keyers that have the *very* low key line resistance that is needed by old TenTec Radios. The keyer is nothing fancy – no weight controls or such on the front panel. But, the 35 yo Bencher feels good in the hand once again.
The Corsair was close to the end of the line for TenTec full-on analog (well, almost) – radios. There’s only the Argosy and the Delta, which are not yet in my possession. The Delta is the last of them I think. Maybe someone will let me know if I’m in error on that. I’d guess the Delta is from mid-late eighties.
There’s a couple good articles on the web about the Corsair, and the “rush” sound issue I’ve described. It appears to be that the Corsair, coming on the heals of the Omni D, a few years later on, used many discrete transistors but also began to make use of op-amps in pretty good supply. The early op-amps were noisier than later ones, and there is an article that describes how to improve noise in the receiver by about 15 db by swapping out the old style op-amps for some newer ones. Here’s the link to that article:
I looked for the little conversion boards that are described in the article, but the company no longer lists them AFAICT. The article dates from 2005, so this is not terribly surprising, I would say.
Here’s another article by a Ten Tec Corsair II officionado, with some interesting insights:
to be continued …