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Hi Friends. Sorry this one took so long in getting to my
web site. I think that some of you may want to build this one. This is a more
modest version of my #35 dx radio. #44 costs much less to
build than the big ones. There are two parts to this radio. The Antenna Tuning
Unit (ATU), which is pictured to the left. On the right is the Detector Unit (DU).
In normal use, the two coils are placed about 6 inches (15 cm) apart with
the coils directly facing each other. The RF energy comes in from the antenna
and is tuned with the pair of 365 pf capacitors. The basic method of tuning is
as follows: If you want the highest selectivity, the capacitor in series with the
antenna is kept at a minimum value (plates mostly unmeshed). The parallel capacitor
is then used to peak the signal. Conversely, if you need more sensitivity, and
give up some selectivity, turn the antenna capacitor towards maximum capacity.
The two capacitors independently will give you the most control in your reception.
The DU has two controls, the main tuning and coupling. If you want maximum
sensitivity, turn the coupling control towards maximum capacitance. Maximum
selectivity is the opposite, minimum capacitance. The detector tuning control is
always peaked to the desired station. It will take some practice to juggle all the
controls, but the reception will be rewarding.
This radio uses 165/46 litz wire for the
coils. This is a good all around wire with a good balance between price and
performance. The capacitors are standard type 365 pf variables found sold by
different online sellers. Increased performance will be realized if you use
better capacitors, such as ones manufactured by Jackson Brothers.
The coupling capacitor can be a fixed 10 pf type or a trimmer capacitor.
If you can find a shaft type capacitor, that will be better. Make sure you use
an isolated shaft to the knob, otherwise the hand capacity effect will drive
you verrückt. A 1N34A diode will
work fine here, but a better diode to use is the
FO-215 germanium type. The transformer is a
Bogen offered by myself and others. Don't substitute this transformer for
other speaker transformers. This one has a special high impedance tap not
found on other transformers found in the US.
Of course, how you put it together is up to you. I used an oak base
and garolite panels. It's ok if you copy how I did mine. I would be flattered,
but other ideas are good too.
73 and good crystal DX. Dave - N2DS
P.S. Take a look at the nice version of my #44 that
Tom Nickel built.
Very nice construction!
And a very nice set built by Charles Spencer.
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