RAN Technology

Hallicrafters AT-10 Antenna Tuner


Vintage Ham Radio 0 Comments 06/07/2021 

One even Dachis doesn't know about!

Posted By: Robert Nickels (ranickels)

 

A while back I acquired a six channel HF transceiver made by the Radio Industries division of Hallicrafters, probably in the 1960s, called an SBT-20.    It is capable of 20 watts SSB or 5 watts AM (or CW with an optional board) in the range of 2-12 MHz and thus was probably aimed at commercial and light-duty military applications.   The radio could by ordered with full 2-12 MHz range coverage, or where the six channels all had to be within one (or more) frequency ranges.   Because different tuned circuits had to be installed for each range, this allowed users to only pay for what they needed.

The unit I have was set up for only one frequency range, which I thought was a shame since I could use my frequency syntherzer modication to over 160, 75, 60, and 40 meters if the tuned circuits were adapted.   I've completed that for all but the PA, where a proper resonant tank circuit is needed for each band, and I'll post more information and photos of the SBT-20 when I've done so.

But in the meantime, a very rare accessory has come my way:  the companion AT-10 antenna coupler - courtesy of my friend Al Culbert KØAL.   He'd read my post looking for information on the SBT-20 and realized the coupler should be united with the radio.

My first thought was "But I'll probably never use it" - however after looking inside, I am so impressed I'll make a point out of using it!   What a nicely done (albeit overkilled?) job!    It is actually four tuners in one, each of which could be switched to match the transceiver to a long-wire or whip non-resonant antenna.   This was pretty common practice for marine HF radios as well, since only  a few preset coupler positions would suffice for the frequencies that would be used. 

As the interior photo shows, there are four large roller inductors (the 4th is hidden under the SWR pickup box on the right).   Since they were set-and-forget adjustments, instead of knobs the shafts have plastic screwdriver adjustements that can be locked in place.    The component are clearly capable of handling much more than 20 watts and the roller inductors are much classier than the typical marine coupler which uses airdux type coils with clips that must be manually positioned.    This is actuall four couplers in one box, where each acts basically as a loading coil for a short antenna.

The AT-10 is shown on a copy of a SBT-20 sales brochure (sorry for the low resolution) - but is not even mentioned in Chuck Dachis'  "Hallicrafters Bible" as an accessory, which is unusual indeed.

More surprising, the small diagram which is probably the only documentation on the planet - was found stuffed inside.   Older hams will recognize Trevose Electronics as a big ham dealer from years ago.

 

Click on the image title or on the image itself to open the full-sized image in a separate window.

Description Comment  
"Documentation"

  

Mystery Transmitter

where's the copper subchassis from?
Category: Vintage Ham Radio
 I didn't set out to buy this homebrew CW transmitter, it was included in an auction lot that I wanted so I had to take it to get the desired item.   But even though I always like to see good quality homebrew gear, this one is just a mystery.Most of the transmitter, including 6CL6 oscillator and buffer stages and a 6146 PA are built on a sub-chassis that is clearly part of a com...  READ MORE
- Robert Nickels (ranickels),  07/15/2021 
  

The Vector VR-50

last gasp from Swan/Atlas founder Herb Johnson
Category: Vintage Ham Radio
 Most hams are aware that Herb Johnson W6QKI founded Swan in Benson Arizona to make single-band SSB transceivers and then moved his operation to Oceanside CA where Swan thrived throughout the 1960s.   Swan merged with Cubic Corporation in 1967, and Johnson managed Swan as its subsidiary until 1973. Johnson founded Atlas Radio in 1974, with the assistance of Southcom International fo...  READ MORE
- Robert Nickels (ranickels),  07/12/2021 
   The Harvey-Wells Company was formed through a partnership between Clifford Harvey W1RF, and John Wells W1ZD in 1939.   Cliff Harvey had earlier founded Harvey Radio Labs in 1933, and prior to that, he was associated with the Hendricks and Harvey Company, another partnership. Producing police radios, transceivers, transmitters, and crystals. Their most popular product was the TBS-50 trans...  READ MORE
- Robert Nickels (ranickels),  06/18/2021 
    I became aware of a few hams playing with a thing designed to receive digital TV in Europe on your laptop - a little plug-in dongle that used an RTL-2832 IC and sold for $20 or so.    Some clever fellows had determined that it could be put into "radio mode" in which it would generate an IQ stream over USB, and by writing to control registers in the tuner IC, it could...  READ MORE
- Robert Nickels (ranickels),  06/13/2021 
    I'm always thinking about interesting combinations of equipment to try out on the air.   One day while rearranging the shack I was getting ready to connect my Globe Scout Deluxe back up with a Collins 51S-1 receiver when the LED (the energy-efficient version of the old light bulb) came on.When I first started playing with DVB-T dongles back in 2012 I wanted an upconverter so I ...  READ MORE
- Robert Nickels (ranickels),  05/29/2021 
  

6AG7-6LG Novice Transmitter

Classic circuit with some modern twists
Category: Vintage Ham Radio
 There's a good chance that more homebrew ham transmitters have been built using a 6L6 than any other tube, and when combined with the superior performance of the 6AG7 oscillator, it's a hard combination to beat (click here for an explanation of the 6AG7's benefits)I'll be adding more info about this project soon, but one of my goals was to reproduce what was a budget-friendly...  READ MORE
- Robert Nickels (ranickels),  05/21/2021 
    All who operate AM in the midwest know and probably have talked to Masa, AB9MQ, who is a very active AM operator.    Having become interested in ham radio while still living in Japan in the early 1960s,  Masa's memories of the "dream rigs" is a bit differen than most US hams, and because the markets were still quite regional at the time, much of the ham gear...  READ MORE
- Robert Nickels (ranickels),  05/18/2021 
  

Hudson American Corporation

Manufacturer of marine radios in the 1940s
Category: Vintage Radio
 I enjoy playing with old marine radios that operated in the AM mode between 2-3 MHz.    This was the standard for "ship to shore" radio and telephone service from marine radio operators from after WWII until about 1970 when SSB was phased in and AM became obsolete.     Through this era a number of manufacturers were major players including RCA (Ra...  READ MORE
- Robert Nickels (ranickels),  05/02/2021 
    I've always thought that knurled aluminum knobs were a high-class option for radio gear, and while they are more durable than plastic they do accumulate tarnish, corrosion, and grunge from dirty fingers over the years and start to look poor.   Fortunately it is easy to restore them to a new attractive appearance using a bead blaster. Mine is a Harbor Freight floor-standing...  READ MORE
- Robert Nickels (ranickels),  04/29/2021 

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