3 x UV199
Homebrew
Regenerative Shortwave Receiver
I purchased this radio several
years ago when I was beginning to become interested in 1920s and homebrew
sets.
It appeared to be in OK condition and was one of my early attempts
to get an old homebrew set playing. Its a 3-tube regenerative circuit
that originally used UV-199 tubes. It is very well made, possibly
a kit. If not, then the builder was very expert at construction.
One collector said the circuit construction and layout resembled that
of a commercially-made See-Ar-Dee receiver.
Among the initial problems I encountered were that both audio transformers
were open. I used replacement windings from AES on the existing cores.
The three tubes that came with the receiver all had open filaments.
I opted to use replacement types from Bill Turner
These replacements use a 5676 sub-miniature tube inside a custom-made
base and glass envelope. This tube requires 1.25 volts at 120 ma as
opposed to the original tubes which used 3.3 volts at 60 ma. Consequently
the range on the rheostats is less than original but not terribly different.
I never was able to get this radio working properly at the time.
I could only receive my one local station across the dial.
After some time I went back into it with a bit more knowledge to see
what could be the problem. I realized that the original builder had
the tuned circuit wired incorrectly and it never had a chance of working!
I'm hesitant to make modifications to a vintage radio but clearly this
one needed some changes. I rewired the tuned circuit to what should
work correctly and I was pleasant surprised to find the dial now full of
stations, easily tunable and with smooth regeneration action.
There are two overlapping tuning ranges and the receiver tunes from
540 to 2100 kcs with consistent regeneration across the entire range.
Audio is more than ample. There is plenty of volume for headphones
at the Detector Output jack. It tends to be too loud at the First
Audio Jack but that may be handy for weak signals. There are a pair
of terminals after the Second Audio for connection to a high-impednace
speaker and volume is good at that point.
I've been running the receiver with 90 volts of B+ and 45 volts of
Detector B+. Filament voltage is 1.25 volts at a total of 360ma.
One rheostat controls the Detector only and the other rheostat controls the
two audio stages.
The cabinet is in pretty nice condition. It was a commerically
made walnut cabinet, albeit maybe a kit, made by International Cabinets.
It is natural walnut with no finish.
...
10 Oct 2007
