Chassis – Prep and Paint

As mentioned in Post #1, I found a nice Bud aluminum chassis (17x8x2) at a local hamfest.  I laid out and marked the positions of the tubes, transformers, RF coil sockets, crystal filter unit, etc.  However, there was not enough room to fit the 2A5/42 audio output tube (or it’s output transformer for that matter)!  I conceded to the idea that I would have to build the audio output circuit on a separate chassis.

But luck once again came to the rescue.  While visiting a local “junk” dealer to acquire some tubes and Hammarlund coil forms, I found a larger NOS Bud aluminum chassis (17x10x3) and an old receiver cabinet amongst the piles of vintage goods.  This new chassis would be more than sufficiently sized to accommodate the entire receiver circuit without resorting to an outboard audio amplifier.  It was also a perfect fit in the old cabinet.

I proceeded to lay out the parts and mark locations on the new chassis.  Once again, I was met with another obstacle.  Continue reading …..

Parts Acquisition

Over the last few weeks I’ve been acquiring parts to complete the 1934 superhet receiver.  As with many projects around here, it seems a bit of luck plays a hand in some finds.

Through some casual searching online, I found a source (oldradioparts.com) for many of the necessary parts, including some useful items for future transmitter projects.  National ceramic tube sockets (4, 5, and 6 pin), cloth wire, vintage mica and paper caps, high inductance RFCs, National SE / ST style variables, and National vernier dial lamps were amongst the goodies:

I decided to try and source the IF transformers and crystal filter by Continue reading …..

After doing a fair amount of building transmitters over the past couple of years, I felt it was time to finally dive into a receiver project.  I’ve built a few simple regens, but I wanted to try something more elaborate and that could at least have a fighting chance in crowded band settings like Field Day, et.al.

After comparing the performance of my National HRO-5TA1 and National SW-3 during our recent 1930s Field Day operation, it was clear a “single-signal” (S.S.) superhet would fit the requirements.  Some form of increased selectivity in the IF chain would be needed.  Back in the 30s, either a regenerative IF amplifier or crystal filter was used to accomplish the needed “single-signal” selectivity.  I chose to use a crystal filter and base the receiver on an article in May 1934 QST, “A De Luxe Crystal Type S.S. Receiver” by LeRoy Moffett, Jr., W9IJ.

The receiver design described in that article is basically the quintessential circuit of the time, other than the monitor portion, and similar receivers Continue reading …..