TheRadioBoard

A fella in Australia sent me some articles from 1923-24 Radio Broadcast, the theme being "Knock-Out Receivers". I had been wanting to build a reflex set so I latched onto the idea of a 2-tuber that was shown. I went with a pair of 01A tubes.

While I was accumulating parts I found an exact type of the coupling/coil/tickler assembly in the junkbox. What a surprise! That thing would never again see use unless I put it to work in this radio because its doubtful that anyone would recognize it.

I got the radio working a few nights ago. It sure is loud for a 2-tuber. Drives well on the ether on the low end of the band but does start to get cranky at the high end. Radio Rebelde from Cuba was booming in on 600 and they seem to be celebrating Sr. Castro's change of status. Havana is 1000 miles from here and that station would have easily been loudspeaker volume.

Still lots of tweaking to do but it seems like a hot receiver.

Here's a schematic:



And some photos. The cabinet is now complete and ready for finishing.







-Bill

A masterpiece as always, Bill.
Thanks for showing it off here. There sure was a lot of people making their own radios
back then. I imagine that many flopped due to bad design or wiring. But many also
succeeded. Do you get the feeling that you are sitting in the mid 20's when you made
that radio? Of course, it is hard to tell what the mid 20's really was like.

I can once in a while hear Rebelde here on 600 during the winter. I sure will miss
those convertible sofas.

Dave

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Hey Bill,

That looks great!

Interesting to see the variable regen on a reflex. This feature tended to be uncommon on 1920's 1 & 2 tube reflex sets. In my experience, it's an absolute must to get decent performance. Wonder why they didn't do the regen on the detector rather than rf amp, to avoid rf transmission?

Keep us informed as you get it tweaked in!

I have yet to try a reflex using a tube detector. Hmm, next project?

Tim

Hi Tim,
The regeneration IS on the detector. (T-S) It definitely plays its role but I find this particular one way too spongy for easy adjustment. Up to now I'm still running the Detector at a full 90 volts so I imagine dropping it down to something more reasonable (~22ish?) may smooth it out. More to come.

Hi Exray, I have been waiting ages for your next 20's homebrew to appear. Your 'brews' are much of the reason I joined these forums. Nice to see you have done one from Australia. Beautiful. Phil.

I was wondering why we hadn't seen anything new for a while. Nice job as always Bill. It's really too good looking to put in a case.

Bill,

Great workmanship as always! I'm unfamiliar with the reflex design, so it's nice to see something different.

Were the coils difficult to set up? It looks quite involved.

"Rob"

Thanks all for the kudos. Rob, I had gotten as far as cutting out 5 spiderweb forms and even winding some of them when I found the 'official' coil assembly in the junkbox. On the left you see two of them wound with the shiny green wire. The instructions explain the coil construction very well so it would not be difficult to duplicate and it was a cinch to hookup the premade version.

I gave it some good exercise last night. I lowered the detector voltage to 22 volts and that really smoothed out the regeneration as it should be. I might also note that using individual rheostats on each tube is indispensable to control the gain of each stage at different signal strengths and in different portions of the band. (note to Tim...that may be an advantage over the diode detector)

Overall I'm very satisfied with it. It handles nicely although it requires a fair amount of tweaking to properly tune in a station. Audio sounds good. The front end is no match for my local station, nevertheless I could still trim out semi-locals on 1620, 1480 and 1240 utilizing an inline trap. Below 1200 or so it does just fine. Thats typical of most radios here.

A station of any strength above the BCB mud could be considered 'speaker volume'. In fact, for the stronger ones you have to detune things for comfortable headphone listening. The article mentioned a user in New Jersey copying KGO-San Francisco at speaker volume using an indoor antenna

-Bill

hi Bill! hi guys!

wow another great looking set! timely, i was looking at something similar (i think) recently, pictured below.

regards,
phil

PS i'm still doing battling with my soldering iron.

By Jove it looks like a match!