Vacuum tube 'down converters'
On my SX-101A I notice it has an band marking for a converter for either the 6 or 2 meter band (as well as a converter spot on the band selector). I'd love to find a vacuum tube converter. What sort of converters are out there that will put out the 30-34.5 MC that the radio wants? I'd love to find something but I haven't a clue as to where to begin looking or who made them. Any ideas / suggestions?
Keep your eyes peeled for vintage converters made by AMECO. They usually had Nuvister front ends and were real hot receivers.
Originally Posted by KB2FCV
"A minute of measurement trumps a decade of debate."
Thanks!! I'll keep my eye out for one. I did a little research and looked up Ameco, sounds like with a little work you could set them up for whatever IF output you need with not too much difficulty. That will be neat to have that working.
They've been turning up on eBay quite often in the last several weeks.
I have a couple of Ameco converters I have yet to use. I have a 2M one that uses Nuivsters and I believe it downconverts to 10M, so getting it to the range you want would likely not be too hard. I am going to get my trusty old NC-155 running again and try out that converter.
I have another very interesting Ameco 6M converter that uses tubes and as near as I can tell runs 12V on both the filaments and B+ and downconverts 6M to the AM broadcast band! Why anyone would want that I have no idea.
Another outfit that made them was International Crystal. I have one of their tube-type 6M converters that I was told was for 2M, and since my NC-155 already has 6M I never used it.
Also consider some military surplus Guard Channel Receivers, such as from the ARC-27 and ARC-34. They are designed for 220 MHZ and up and have IF outputs down in the HF range. I have an ARC-34 guard receiver I paid 50 cents for years ago, and Fair Radio has been selling ARC-27 guard receivers for years now for under $20.
Make sure the converter is equipped with the proper crystal for the IF
range you are looking for! IFs in the 28, 14, 7 and 30MHz ranges were all very popular. Unfortunately, the correct crystal is probably worth than the converter today.
Look for names like Tapetone, Janel, "W2AZL," Tecraft and even EF Johnson. Johnson made a small 6N2 converter (six and two meters combined) in a small package. Again, it came from the factory with 3 or 4 IF range options. The correct 6N2 converter for the 30.5 MHz IF is either 250-43-4 or 250-43-42. Unfortunately most sellers on eBay are flippers and don't have a clue what IF range the converters are for, so you may have to ask for the crystal frequencies and work the math.
You'll also have to consider the power supply. Some, like the Amecos, will need to steal power from the receiver or a separate supply. Converters like the 6N2 and a few others, have their own built in AC supply. National also made converters for specific receivers. I'm not sure if the NC303 used the same IF range for VHF converters as the SX-101?
For a Hallicrafters rig, the companion HA6 and HA2 transverters might be worth looking at; but they will be ham band IFs--they can be pricey if in good condition. I see you also own a HT-32A and a SX-101A; I am restoring a pair myself. I am eventually to modify a Johnson 6N2 transmitter to work as a transverter on 6 and 2 mtrs, along with the 6N2 converter, to have a really vintage VHF station.
Last edited by K1ZJH; 12-06-2010 at 03:36 PM.
Hi \robert. Such things were made to convert them to car radios! Gonset made a similar device as well.
Originally Posted by WB5WSV
"A minute of measurement trumps a decade of debate."
The weird tuning range of the SX-101A and NC300/303 allowed tuning all four MHz of the two meter band on a single slide rule scale. However most of us using these receivers "back in the day" didn't bother using those scales, we used a 28 MHz tuning range (L.O. at 116 MHz in the converter, so 28.00 MHz = 144.00 MHz receive frequency) to get better calibration and resolution and make SSB and CW signals easier to tune in.
So if you want a converter, don't sweat it if you don't get the 30+ MHz I.F. version, it's not that great anyway.
Ameco made converters for all sorts of frequency ranges including the 6-meter and 2-meter amateur radio bands. The converters for the 6-meter and 2-meter ranges came in 2 different versions. The CB-6 and CB-2 used "normal" miniature tubes with the r.f. amplifier being a 6ES8 and the CN-6 and CN-2 which used Nuvistor tubes. The 6ES8 tubes are not that common but the 6BQ7 is the same tube and are readily available. The Nuvistor converter was also available that covered the 220 MHz band (now 222 MHz).
The Nuvistor converters have a slightly lower noise figure than those using the 6ES8. However, either model converter works very well. I have at least 15 of the Ameco converters, both the miniature tube front end and the Nuvistor front end.
The Hallicrafters SX-101 Mark IIIA and the SX-101A had a converter band that covered 30.5 MHz to 34.5 MHz calibrated for 6-meters and 2-meters. The National NC-300 and NC-303 had a converter band in the same frequency band that was also calibrated for 6-meters and 2-meters. Heath, in the RX-1 Mohawk, used 22.0 MHz to 26.0 MHz for the converter band.
There are other tube-type converters made by various manufacturers that are also available. These include ones made by National, Heath, Johnson, WRL, International Crystal, and several others as well as all sorts of home brew converters.
Being somewhat of a "converter junkie", I have between 30 and 40 converters made by several manufacturers (including Ameco, WRL, Heath, International Crystal, Tecraft, Gonset, RME, as well as home brew) for the HF bands, for 6-meters, 2-meters, 222 MHz, and 70 cm. With the exception of the Heath XC-6 and XC-2 which were designed to be used with the RX-1 Mohawk, most of my converters use either the 10-meter band (28.0 MHz to 30.0 MHz) or the 11/10-meter bands (26.0 MHz to 30.0 MHz) as the intermediate frequency. Since my Collins 75A-1, 75A-2, and 75A-3 receivers have full coverage between 26.0 MHz and 30.0 MHz, I often use that particular range.
The 6ES8 is one of the only remote-cutoff triodes and is completely different from the 6BQ7, although they share the same basing and might sub for each other in cases where there's no AGC.
Originally Posted by K9STH