One valve regenerative receiver runs off 12 volts HT - Part 1

What happens if you use 12 volts as the high tension for a homebew valve receiver?

The answer is you lose the need for a mains power supply, eliminate AC hum problems and can prod around inside without getting bitten. Construction is also much quicker.




This video describes a 1 valve regenerative receiver using a 12AX7 mains valve. The filaments are wired in series and the whole lot is run from a 12 volt gel battery.

It tunes about 470 - 1900 kHz, allowing reception of signals on either side of the AM broadcast band. Eventually I'll add more coils for HF coverage.

The set was built in a day based on the refined Thames & Kosmos Radio Ace circuit here:
http://cool386.tripod.com/kits/ace.html I didn't need to change any component values as those given worked first time.

But I did (i) add an LM386 audio amplifier (22k plate resistor replaces the transformer primary) to provide speaker reception and (ii) wind the coil on a ferrite rod, complete with a winding for the antenna (about 70 turns with the tap at around 10 turns from ground).

If you don't want the LM386 stage, just wire some 2k impedance headphones instead of the transformer primary (satisfactory reception on local stations) or do like the original and use a power transformer to step down to low impedence phones.

As for valves, I agree that the 12AU7 provided the easiest regeneration. A 12AT7 was less active but could still be made to oscillate across the whole band. A 12AX7 also worked but only oscillated in the top half of the band with the coil tap used.

The performance achieved speaks for itself. But you won't need an external antenna unless planning to receive distant stations.

Category:

Science & Technology

Tags:

• radio
• AM
• battery
• valve
• vacuum
• tube
• receiver
• homebrew
• low
• voltage
• high
• tension
• HT
• 12AU7
• regenerative
• broadcast
• 160
• metres
• Thames
• Kosmos
• Ace
• Radiomann

[alexismex1]

hello VK3ye

Sorry to be blind,but where is that description to see above!!!!! in your video i did not see_ thanks

[vk3ye]

@alexismex1 Yep it's there - checked today. In the cool386 link in the description above. There's 2 diagrams, the modified one about 2/3 down.

[alexismex1]

Hello Vk3ye,

very good this radio, i have search in cool386 but did not find the schematic,please can you tell me where it is? Thank you so much Alexis

old Xe1iak

[vk3ye]

@alexismex1 See the link in the description above for the circuit

[hairymolly057]

yery nice radio,can you send me a shematic,thanks in advance

[vk3ye]

@hairymolly057 Glad you liked the radio. See the link in the description for the circuit.

[Shuspano]

It is lie. It not the single-tube receiver. It consists of one valve, and tens transistors in IC of the amplifier of a speaker

[hrbear]

Excellent! From 5:21 to 5:24 you received a greek radio station ;-)

[roger6146]

Just finished building a similar set using a 1Q5GT instead of a 12AU7. I also used an LM386 to drive a loud speaker. But the "magic" is in the front-end. The sensitivity and selectivity of these regenerative sets is just amazing!