I have been playing with the Radio Broadcast's One tube Reflex "Knock-Out" radio from Nov.23 and am hooking up the parts but have a question about the speaker hook up. I have added the schematic below.
I see there is a Jack in the circuit that controls the filament. If I assume the speaker would plug into it I see A+ on one lead and B- on the other lead.
Is this correct?

Here is a similar circuit from Audels where the B+ feeds thru the phones to the primary of the RF transformer and back to B- thru a cap.

Not having any luck receiving any noise from the first schematic. All the hype at the time for this circuit suggests that I have something hooked up wrong, but have not found it. Any thoughts on the first schematic?

Hi Brian,

Yep, if that set is quiet, something isn't right. The one tube reflex is a pretty decent performer.

Be sure you are using Hi Z phones... typically 2K ohms.

Thanks, Tim

ya - Blonde moment I had the Audio Transformer connected backwards. It is one I had on hand and a high ratio of 1:7 1K to 7K.

I ended up turning on the house transmitter and was able to hear KCEA without a lot of volume. Selectivity was poor as it covers most of the dial. But it is working.

The variable condensers are both 5 plate rotor types. Don't know if this would affect the tuning.

Hi Brian,

Sounds like progress!

That thing will tune sharp if the two tanks are properly sychronized. ie when both tanks are peaked up on the same frequency it will scream. Might want to verify turns counts on each RF transformer.

I've built a couple of these and find them to be pretty surprising.

Hang in there, Tim

Hi Tim
In trouble shooting this radio I posted on 2 another threads about the coils I made and the variable condensers I used. On the one about the coils there is a link to a site to calculate turns, dia of form and wire size. If I plugged in the numbers I was supposed to use and the numbers I did use I found my 3" dia form to have about 50% more wire than required on all coils. The condensers turned out to be way under sized with 5 plates instead of like 20. So I will be looking to make new coils and gather up the proper size condensers before I move onto the next stage - a 2 tube version of the Radio Broadcasters Knock out radio from about 1924. Am looking to recreate what may have been done then.

If someone has come up with successful coil data for use with the standard 365mmf tuning caps available today, that would be helpful. I would guess that the coil windings connected to the caps would be calculated for the broadcast band, but what about the primaries of each coil set?