The AM Forum

For a little fun..

The directly heated 2E24 is a somewhat neglected gem, perhaps due to its directly heated cathode. It uses a center tapped filament rated 6.3V@0.65A. It has a 10W CCS, 13.5W ICAS plate dissipation. The filament heating time is specified as <2 seconds. It seems to be the quick-heating version of the more popular indirectly heated 2E26.

It was designed for mobile and emergency communications gear and would be interesting where energy economy is wanted as the filament would not have to be kept hot during standby.  The 2E24 is useful as a modulator and an RF amplifier and should be a great "QRP" tube where the rest of the set is solid state.

The AB2 data given is for audio service, but with there is no reason it could not be used as a linear RF amplifier. A pair of them can make 42W with 0.43W of drive, -15V bias, 400V on the plates, and only 125V on the screen. Resting and maximum signal plate current for a push pull pair are an efficient 18 and 150mA. For linear RF service, a slightly higher idling current might be wanted to improve linearity at low signal levels.

Plate-modulated RF ratings allow a 13.5W carrier CCS and 18W ICAS per tube. For CW, 20W CCS and 27W ICAS are available. Drive is about 0.2W and bias is about -50V. The full ratings apply below 125MHz.

The 2E24 is very inexpensive, perhaps because it was made in quantity for mobile use, the product life cycle of that equipment was fairly short compared to tube consumption, and the need for supplying grid current in order to get useful power from it keeps most audio hobbyists disinterested. It can be found for $4 on the internet.

Does anyone know of equipment that uses the 2E24?

What is the tube used in?   

Receiver/Transmitter RT-66, RT-67 and RT-68. Military FM vehicle radio Jeep "Bumpy" transceivers. Freq. range for the set is 20 to 54 mHz. with over lapping freq.

And yes, I have all 3...

I used a 2E24 in a compact 10M AM mobile rig in mid-1950s. Good little tube; several other locals used it too. Rapid-heating filament didn't work out on our monitored frequency with our break-in method though, so it was replaced with a 2E26 as you surmised is a direct replacement. We used three quick carrier blips to break-in and the 2E24 was not conducive to that kind of operation.

Bob - NE

When I got involved in 2 meter FM back in the early 1960s one of the more popular rigs was the Motorola P33BAM series of portable radios.  They used sub miniature tubes (1AD4, etc.( in the exciter chain and the higher power models had a 2E24 in the final.  Power in mine had the nicad pack and inverter; and the RX was solid state.  Two frequencies, and were sitting in the cat bird seat!!! LOL!

Also, I had a few VRC-19 military mobiles, I remember the receivers and transmitter stages were mostly sub mini's, and I would swear it used 2E24 tubes in the final.  Again, this for a converted 2-meter FM base station.
 
Thanks for the memories!

Pete

        I had an RT-68 back in the day,  They sounded quite good
if you didn't use the Military Mic.  Mine was fed high quality
Rock and Roll off a Dokorder 10 1/2 " Reel to Reel.  Running
in the 44mcy (ish) area we excited a HB doubler to the 88 mcy
(ish) area.  Had a 6 element yagi suspended in my attic
pointed North from my hilltop QTH South of town.  Worked
quite well. My 72 Coupe De Ville (With Skirts) Picked it up
all the way to the southern shore of lake Erie!  Even solid
into downtown CLE.

        Even though the rig was monaural, I found I could inject
19 kc from an old HP somethin' or other, and get the stereo
light to come on. 

     Commercial Free since 73

Yes Thanks for the "Flashback"

/Dan

We had a Motorola transmitter that used a single 2E26. It was equivalent to a microwave terminal operating at 900mhz. We would get about 8 watts out. B/W was capable of 6- 3kc audio channels (can't remember) using an external mux to input the transmitter and the receive info was connected to the receive port of the mux unit.