A Double-Valve Short Wave Radio

Using a basic tried and tested circuit using a double-triode valve and easily obtainable parts, this little set gives a good account of itself and can be built into the Radar Rooms 'universal chassis' for convenience. Full constructional details are given, along with a selection of video clips showing the kind of results easily obtainable.

[@clarefreeman3909]

Nice job once again Clare

[@lishaton]

Thank YOU Clare :-)

[@Radio478]

Thanks for this video, it was really helpful 👍

[@lishaton]

Thank you! This is actually a very useful little circuit, but there are in fact many, many more out there! I recently completed a larger 2x band SW project in a proper cabinet (I made for it), incorporating 4 assorted valves (and valve rectifier), with an RF amp, TRF circuit, regenerative detector/AF amp and pentode o/p stage. I'm tempted to do a video of making one of these if I have a minute!

[@Radio478]

@@lishaton thank you for your reply, yes it would be great if did make a video of it☺👍

[@old-developer-q9b]

Thank you for your uploads of excellent videos.
One question: is the reaction coil turns more turns than the tuning coil?

[@lishaton]

Glad you're enjoying them! Yes, in my experience the reaction ('ticker coil' is the US name) is always more turns than the aerial coil. In this case it's 38 turns for the reaction as opposed to 25 turns for the aerial.
Interestingly, my first ever valve radio was from the 'Beginners Guide to Radio' and had the coils initially wound on a 'broom handle'! The coils were then slipped off the handle and the turns bunched together with sellotape on both sides. The aerial coil had 40 turns and the reaction coil was 60 turns. Both were then laid flat on the wooden baseboard on top of each other with one slightly overlapping the other.
If you make this radio and it DOESN'T oscillate with the reaction fully clockwise, then try reversing the connections to JUST the reaction coil. (NOT to both this AND the aerial coil)

[@TechTed1]

good video

[@lishaton]

Positive comment appreciated :-) Thanks!

[@adrielrowley]

Thank you for part two.
To clarify, this uses the same schematic, the difference being the use of a 6SL7 tube and the windings? So if we desired to pull in FM, we use the previous winding specifications?
Would it be possible to switch between the two winding sets for different bands?

[@lishaton]

This receiver is completely different to the super-regen VHF one I've shown in another video. It is just an 'ordinary' regenerative receiver with a variable reaction ( or 'tickler' U.S.) control. You can make it work on several other bands, simply by either substituting a 'plug in' type of coil, or by just using a multi-pole switch to switch in both the aerial and the reaction coils for each band. Watch out for your layout though, as wiring can easily become too long and messy! Check your layout carefully before starting a build.
In days of old, you used to be able to buy the plug in type coil from several different manufacturers, with long, medium and several short wave bands, but not VHF/FM. Actually, upon reflection, it would make quite an interesting project to combine both this short wave set AND the super-regen set circuits into the same box, using a common AF speaker amp? Food for thought?

[@sciencefollower]

APPRECIATED

[@lishaton]

Thank you! :-)