Thursday March 18, 2021
My fear of having taken an overpriced gamble turned out to be just that — a fear that today, proved unfounded.
I’m talking about my recent purchase of a Hallicrafters HA-20 VFO that matches my Hallicrafters SR-400 Cyclone transceiver. The VFO arrived in the mail Tuesday, and the missing voltage regulator tube — an OA2 — arrived in today’s mail.
The tube was NOS — a military tube from 1952 — and it was still sealed in the box.
Inside the HA-20, the chassis was mint; hell, the VFO still has two of the original Hallicrafters brand tubes in it (only 3 tubes total). I installed the tube and for the first time, plugged it in and powered it up. The lights and tubes all light up, no buzzing, no smoke, no fire — woo hoo!
I put it back in its case, and hooked the unit to the Cyclone. The VFO has its own transformer, so it doesn’t draw any power from the transceiver. Fired up the Cyclone and VFO, hooked up the coax, and the Cyclone came to life as it and the HA-20 warmed up. I set the HA-20 to receive and once I adjusted the calibration, it was spot on and received perfectly. It worked as the Transmit VFO, and the final test — the Dual Receive function — was flawless! The only drawback of dual receive is not being able to lower the volume on either frequency, but hey, we’re talking 55-year-old technology, so I have to cut them some slack.
The one thing I didn’t get with my HA-20 was something I didn’t realize wasn’t coming with it — the SWR bridge that detects standing wave and provides that reading to the built-in SWR meter (see schematic above). I wasn’t aware that the bridge was a remoteable unit, but it makes sense. Heathkit did the same with some of its SWR bridges.
Fortunately, the bridge is pretty much the standard type of SWR bridge published in dozens of ARRL handbooks. All I need are a couple of diodes, a few capacitors, some perf board, a project box and a couple of chassis-mount SO-239s. I plan on building one that should make the SWR capability functional on the HA-20.
I could grumble about the fact I paid a fairly high price for the HA-20 that arrived incomplete, but my gut tells me the seller probably didn’t know that an external SWR module was part of the unit. Frankly, I think the SWR function was an afterthought. Looking at the unit, it needed another window or meter on the righthand side to maintain balance of the front panel. I doubt many hams owned the SR-400 or SR-2000 depended on the HA-20 as their sole SWR measuring device.
I’ve been focused on operating my Ten-Tec rigs — the Paragon and now the Omni V.9 — and it was great to fire up the SR-400 and enjoy the beautiful audio.
I still find it maddening that the SR-400 has no audible sidetone when operating CW! It has a beautiful CW and notch filter capability — you would think a sidetone would be part of improving it for CW use. Apparently, the company assumed you would use the HA-1 keyer with this rig, which not only accommodates iambic keyers, but also has an audible sidetone. I have a couple of HA-1s in collection, and I will most likely put one to use with the SR-400 station.
At any rate, I couldn’t be happier to have a complete SR-400 station now with my fully functional HA-20 VFO. My next job is to safely store that station until such time as I have Studio C fully equipped with my desks and shelving units.
73 es CUL …. de KY4Z ….. SK …. SK ….. (dit dit) ….