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Re: [IRCA] DXing with a One Tube Radio
On 29-Dec-08, at 9:39 PM, Deane McIntyre wrote:
Some of you may recall the books by Alfred Morgan such as The Boy
Electrician and The Boys First Book of Radio and Electronics that
had instructions on how to build, among other things, crystal radios
and a one tube regenerative radio. In the case of the regenerative
radio,
a 1H4H triode tube was used with the filament operated off a 1.5
volt D cell
and a 45 volt battery for the plate voltage. Later editions used a
6BF6 tube
instead as the 1936 vintage 1H4G tube became difficult to find. The
circuit
was close to that used in the early radios of the 1921 - 1925 time
period,
when AM broadcasting was getting started.
Having read that in those days of few stations these one tube regen
radios
were capable of DX, I built one, using a 1H4G tube, and am having fun
DXing with it. I finished it last night and soon had logged
CKRM-620 Regina,
KIRO-710 Seattle among many other stations. Best DX tonight so far
was WGN-720
Chicago, also had KNRS-570 Salt Lake City, KNBC-680 San Francisco
among
many other stations. Best daytime DX was CBK-540. Am having a lot of
fun with this - with seven local 50 kW stations here in Calgary,
was wondering if I would get
much DX at all but with careful adjustment of the regeneration the
selectvity
is not too bad - was even able to log with good signals KBOI-670
next to
local 50 kW CFFR-660.
As 45 volt B batteries are just about a thing of the past, I am
using four
somewhat elderly 9 volt batteries in series that gives 32 volts. Total
cuurent draw is only 0.9 mA (and 50 mA from the D cell for the
filament)
so the batteries should last a long time. Antenna is a 50 foot wire
outside
run from the house to the garage.
A few people have asked for further information on my one tube radio
I wrote
about last night.
<http://www.bignick.net/Morgan_Radio/images/Morgan.pdf>
is a scan of the article of the 6BF6 version. The version I built
used a 1H4G
tube, taken from a older book by Morgan, but is otherwise almost
identical to the
one in the article linked to.
Finding the parts might be somewhat of a problem, I had all the parts
on hand
except for the coil. The parts needed are:
Vacuum tube - 1H4G. 1E4G, 1G4GT, 30, 1LE3 or 1LF4 are all almost
identical
to the 1H4G if you want a battery powered (1 D cell) version. Or use
a 6BF6
or just about any low gain triode tube if you build the circuit in
the article above.
Socket for tube (1H4G, 1E4G and 1G4GT use a standard octal (8 pin)
socket, 30 needs a
four pin socket, 1LE3 and 1LF3 a loctal socket which might be hard to
find.
Two variable capacitors - one about 365 pf for tuning, one about 100
pf for
antenna coupling.
Coil (which I wound myself on a 3 inch dia cardboard tube using 26
gauge enamel insulated
copper wire, 54 turns for antenna coil, 20 turns for regen coil
spacked 1/4 inch from each
other)
resistor, 2.2 or 2.7 meg ohms
100 pF mica capacitor
0.003 uF or so capacitor, any type, for audio coupling to headphone
headphone jack
100 k ohm volume/regen control
headphones, 2,000 ohm resistance or better
D battery with holder (to heat tube filament)
3-5 series connected 9V batteries
Antenna and ground connection
Something to build the circuit in/on
Most of these items are available from Antique Electronic Supply if you
don't have a large pile of electronic junk
<http://www.tubesandmore.com>
Photos of my radio:
<http://deane.bio.ucalgary.ca/1H4regen1.jpg>
<http://deane.bio.ucalgary.ca/1H4regen2.jpg>
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