One of my interests is World War 2, and collecting the old military radio gear is a natural extension.
The one on the left is a T20 transmitter with a frequency range from 4.0 to 5.3 MHz. The one on the right is an R23 low-frequency receiver with a frequency range from 190 to 550 kHz. I have others, but they all look like the ones above, either receivers or transmitters. The ARC5s saw action in every service in the war. They flew in planes, sailed on ships, and traveled across the battlefields. Some were natural aluminum; others were painted likes these.
This unit served as the laison receiver in many of the bombers including B29s. As you can see, this one is in fantastic shape. It has an AC power supply in place of the dynamotor; other than that, it is stock.
This receiver/transmitter unit was part of a portable communications unit housed in a half-ton truck. The rather-beat-up panel in the lower left has a generator starter switch, mic and headset jacks, and the CW/AM switch. This unit has been on 75 AM. It puts out about 40 watts of AM using two 807s modulated by four 6L6s in parallel-push-pull. Since the original mic used a carbon element, no amplification is used to drive the modulator tubes, just a transformer. Therefore, I use a solid-state audio amp to talk with it. The receiver is VFO and crystal-controlled, and the transmitter is crystal-controlled only.
This is somewhat of a rare find. This transmitter had two different part numbers (as do many military radios): the BC-191 was a ground unit; the BC-375 was used in aircraft. They were the same unit. It uses the hard-to-find VT-211.
One is used as a driver, two as modulators, and the fourth as the final amplifier. The plug in tuning unit on the bottom is a TU-8 that covers 6.2 to 7.7 MHz. To change bands you have to change the tuning unit. This unit is sitting under the bench waiting restoration.
This receiver was made by Collins Radio and was used throughout the military. Although not WW2 vintage (1948 til ?), it was one of the last non-single-sideband receivers. Its successor, the 51J4, was the first receiver to use the Collins mechanical filter.