[MrFixr55]

I have several "Farm" radios for a few reasons:
First, they are usually a lot cheaper than house current versions, precicely because of the issues mentioned above on how to power them.

Secondly, the circuitry is interesting in their own right. There are various systems. Some, very similar to "car radios", even with the same 6V tubes and B Vibrator, running off a 6V car battery. Others, like the 37-624, using "2V tubes" with filaments in series -parallel and a vibrator B supply, also running off a 6V car batteries. There are also sets using "space charge" tubes that ran from 30VDC from Delco farm power systems. Soe used a 2V lead acid or "Air Cell" "A Battery" for the filaments and anywhere between 90 and 135V worth of "B Battery Blocks". One of the easier ones to deal with are sets made in late 1838 and later which used the same octal and later miniature "1.4V" tubes that were used in the portables of the 1940s through late 1950s before transistors took over. These were powered by a 1.5V and 90V batteries. An alkaline D Cell will run the filaments for quite a while. B power can come from 9V transistor batteries or build a simple supply for that.

Thirdly, these represent important history. These radios were used in areas where AC Power was not available, usually in rural areas of the Midwest, Great Plains, Deep South, etc. areas of the US, where utility power was not available until after WWII. The radio was the link between the rural farm family, usually living a hardscrabble life, and the outside world. The farmer may have used it to find out commodity prices, the family may have listened to religious services on Sunday, and, occasionally, entertainment.

Which type of power (6V, 30 V or 2V a Battery and 90 - 135V B Battery) depended on location and if the farm was mechanized. If the farm had a Delco system or "WinCharger", they had a 6V or 30V radio and the luxury of listening to it when they wanted. If they were not mechanized, then they had the A and B battery radio and used it sparingly.

It is surprising that as many of these that did have serviced, considering their obsolescence upon electrification. Often, radio sellers would hold "bonfire parties" along with sales of AC powered radios after electrification, where these battery radios were all piled up and set on fire.
 
To someone who is a 3rd - 4th generation Irish - German American whose US ancestors all lived in the New York Metro Area, these artifacts of the Depression and Dust Bowl period are touchstones to those that sacrificed greatly and worked hard to feed the USA during a period of great turmoil.

I have 4 of these farm radios:
- Coronado 650, ca 1937 (2V, 90V set, not yet working) This set was marketed to the rural Midwest and had a 455KHz trap to
attenuate the ship to shore Morse Code great Lakes navigation radio traffic.
-RCA 5BT, ca 1937 (2V, 135V Broadcast set with a power supply that I built)
-RCA 6BT, ca 1936 (2V, 135V Broadcast / SW set with a power supply that I built). The 5BT and 6 BT were great performers. The
6BT had the option of running from a 6V Vibrator supply for B power and tapping the 6V battery for 2V filament power.
-RCA 14BT2 ca 1940 (1.5V / 90V power, chassis, battery and tubes similar to those of battery operated portables of the time).