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W4JBM's Conar Twins Page

Back in the Spring of 2002 I went to a hamfest with the intent of buying the stuff to build a simple homebrew tube station. I didn't have a lot of luck finding parts, but at one table I came across a pair of radios that caught my eye.


The Twins

The radios were matching Transmitter and Receiver sets from Conar. I'd never heard of them at the time, but looking at them they were cute, simple rigs. If you spend much time trying to come up with a minimalist vacuum tube transmitter and superhet receiver, you'd probably arrive at a very similar design. It was slim pickings on parts that day, so I decided it would both be cheaper and more fun to lug home a complete novice station instead of boxes of questionable (and overpriced) parts.

The receiver fired up fine and worked. I did go through a do an alignment on it, but for a 40 year old receiver it didn't take much tweaking. The speaker was okay and audio sounded good. The two things the receiver lacks are an accurate dial (not even a crystal calibrator) and selectivity.

You can actually forgive the first one because at the time it was built a novice would operate using crystals, so these could be "spotted" on the dial. Once you tuned in your transmit frequency, you'd cruise up and down the dial a bit. In fact it's not unusual to find pencil marks that denote were to tune with certain crystals.

And the second one isn't as bad as you might think. There is no filtering, but with the interstage IF transformers peaked at 455 kHz and the BFO properly aligned, the bandwidth isn't even as bad as some of the simple superhet stories I had read made me fear.

One trick I use with receivers that have high impedance screw terminal inputs is to use a television balun to connect the antenna. This seems to provide me the best performance.

When I powered up the transmitter everything seemed okay, but I couldn't get it to tune up with the old television crystal I was using. From what I read in the manuals and old handbooks, I suspected it wasn't oscillating.

I borrowed a real FT-243 crystal from Steve AA4BW. It still didn't seem to tune up but a note to the Glow Bugs mailing list brought a suggestion from Joe WJ5MH to check the bandswitch (among a couple of other things). The bandswitch? (I said to myself...) Well it can't hurt anything. A shot of contact cleaner and working the switch a couple of times and what do you know--I'm on the air!

Conar transmitters are notorious for their chirp because they don't have a regulated power supply. I had checked the capacitors (using the ESR tester I wrote about in the September 2001 issue of QST) and they looked good. Listening to my own tone, there was noticeable chirp but not as bad as I was expecting. It gives my signal a bit of character but isn't so bad that I get QSLs from the OOs.:-)

Since I don't have many FT-243s and the ones I have aren't in the ham bands, I put together a simple little adapter that lets me use any kind of crystal with the Conar or my other transmitters. This was made from an old FT-243 that was to far from the ham bands to try to grind down.

So there you have it--a classic 1960's novice station. Operating on 40 meters early in the morning isn't too bad. When 15 meters first opens in the afternoon it's operable. As the bands fill up, selectivity does become a bit of an issue. I never operate 80 meters anyway (takes too long a skyhook for my neighborhood). Not a bad station and it doesn't warm up the basement shack in the winter as much as I'd like.

Maybe I need an R-390 and a full gallon amplifier...


Back in History

Operating the Conars got me curious about their roots...

Early last century James E. Smith, a high-school teacher, built a radio receiver to help students learn about the exciting new field of wireless. He eventually went on to start the National Radio Institute in 1914 with a goal to prepare students for jobs as radio technicians, repairmen, and operators in the commercial broadcasting, two-way radios, and the military.

In the early days of radio, NRI was unique with its focus on hand-on experience. They were also a pioneer when it came to training people interested in TV repair. In fact, as early as 1932 students were building their own televisions!

In 1968 the company was purchased by McGraw-Hill and renamed NRI Schools. Smith continued to lead NRI until his death in 1973. In 1999, McGraw-Hill announced it would phase out NRI Schools because of changes in the marketplace. Over it's 85 year history NRI served more than 1.5 million students.

From what I can gather, Conar was tied to the National Radio Institute's student supply division. Beginning in the 1960s they supplied test equipment (both as kits and assembled) to NRI students and graduates. In fact, one source suggests that the Conar name comes from COmpany NAtional Radio.

One of the courses NRI offered in the 1960s was a ham radio correspondence course. The Conar Twins were the culmination of a student's efforts--they built their own station!

The 2R receiver kit (also available as the Model 500) was a simple three-band superhet receiver:

The 3R transmitter kit (also available as the Model 400) was a single tube, crystal controlled transmitter:

I haven't been able to find information on how many of these radios were sold, but today they have almost a cult following. They are cute, simple, and rare compared to things like Heathkits.


Here's an NRI advertisement featuring the twins...

Click to view larger Scan.


Other Resources

AF4K's Conar Twins Page with copies of the manuals and lots of useful information including modifications.

K2TQN's Old Radio's page contains follow-up information about the Conar Twins after his July 2001 QST column


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