Phil's design of a valve FM pulse counting tuner using safe 25 volt HT line

This is a working version of one of the easiest valve FM tuners that can be built on earth. It has a low frequency IF of around 250KHZ and as a result there are no IF coils to wind. There is a total of 6 Valves in this design. The RF section is a double triode ECC88 and half of the triode is a grounded grid RF amplifier resulting in very stable RF performance. The other half is a autodyne converter using the cathode tap electron coupled oscillator idea. The other 3 ECC88 triodes that follow are resistance coupled IF amplifiers followed by the limiter. The 5th valve that follows is a EB91 or 6AL5 double diode to form as a voltage doubling pulse counting detector resulting in very good mono reproduction. It also uses a safe 25 volt HT line making it ideal for absolute beginner's to valves to construct. There are only 2 RF coils to wind. Stereo reception is posible with this receiver but needs a slight modification regarding the deemphasis network in the discriminator and a simple phase correction circuit to follow the decoder. Also be warned that stereo reception only works well on the very strong FM signals such as UK Radio 2 or if you are lucky to live near a strong local station and relies on the best outdoor antenna system you can possibly go for, clear of hills or tall buildings as the signal level needs to be 70 db for hiss free reception. As you can see in the video there are no solid state active devices helping this design out and for its low HT line it works as good as sets that use a 250V HT Line. The link for construction details of this design is http://philsvalveradiosite.co.uk/philsvalveradiosite/valvevhffmpulsecountingr...

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[thawatchaie]

Thank for your VDO .I can not see any IF & Out Put Transformer.

[vhfbroardcaster]

@thawatchaie This type of FM tuner does not need any IF transformers, the reason being because of its low IF of 250 KHZ and in that case resistance coupled amplifiers can be used which is the great advantages of building this type of receiver. Also because at the time of composing this video it was linked to my EL84 power amplifier and as you may not see the output transformers, thay are underneath the chassis.

[albertusj]

sounds pretty damn good! I'm also thinking of building an FM reciever now that I'm getting bored building valve amps. I have two headphone valve amps so far and one 10W class A stereo amp for speaker use.

[rockangel1967]

AWESOME!! i found you by coincident when i was looking for tube stereo decoders. I plan to build a tube heterodyne FM but now i found your website. With your consent i will build this radio? thanks for the many accurate details and huge amount of good information!