[Drake] Re: Drake 2-B as Selective Demodulator

[Garey Barrell]

Yikes!

I always hate to see things like this......  :-)

Unfortunately, this is a VERY nice idea.   Essentially all he's doing is 
making the BFO "tunable", using the Main tuning capacitor and dial 
mechanism, and using the Q-Multiplier socket on the rear panel to access 
the "INPUT" of the resulting "tunable IF".   He's just using the back 
end of the receiver from the Passband tuner through AF out.  Another way 
of looking at it is he is using the R-390 as a tunable front end for the 
2-B.   I like that better!  :-)

On the bright side, it IS an easily made and reversible modification.

For the old timers, he's making the 2-B into a Q-5'er, which was a WW II 
aircraft receiver that tuned from 190 to 540 kHz.  It had an 85 kHz IF 
that was undercoupled to make it very selective, at least by 1950 
standards.  My receiver at one point consisted of a different aircraft 
receiver of the same family that covered 3-6 MHz with a WIDE IF at 1415 
kHz IF.  I could hear the entire 50 kHz Novice band without touching the 
Main tuning!  However, by coupling my clock radio to the IF and tuning 
IT to 1415 kHz, I had double conversion to 455 kHz AND Passband tuning.  
The addition of a Heathkit Q Multiplier to the clock radio (not a 
trivial exercise since the clock radio was AC/DC !) greatly improved my 
signal slicing capabilities.  Still later, a Q-5'er was coupled to the 
IF of the clock radio, giving me triple conversion, dual passband 
tuning, and really tight selectivity.  I was down to only three or four 
signals at one time!  And LOTs of knobs.

Another very interesting project going on these days is the "Softrock" 
series of software designed receivers.  This is a small board that 
interfaces to the sound card of a computer, using the computer for all 
the "back end" duties.  It is also tunable over ~+/- 12 kHz.  Software 
is available to provide all sorts of DSP filtering capabilities and 
other features of "modern" rigs.  By setting the Softrock for 455 kHz 
(or ANY IF up to 30 MHz) it can be used for ANY receiver.  It's also 
CHEAP, a complete kit for less than $10 !!   Of course you gotta have a 
computer, but if you're reading this ......

A good description of the FIRST version of this unit is shown at

<http://www.amqrp.org/kits/softrock40/>

The latest version is still available from the designer, Tony Parks, 
KB9IYG, at <raparks @ ctcisp.com> less spaces.

73, Garey - K4OAH
Atlanta

Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>



Chris Kepus wrote:
> W4THU converted a Drake 2-B receiver to a 455 KHz SSB/CW demodulator.  He
> states on his web site that, "The conversion of the 2-B is simple and all of
> the mods are removable in just a few minutes."
>
> http://radioworks.com/Hamshack/shack6ademod.htm
>
> I have sent him several e-mails but I apparently cannot get through his spam
> filters or he is just too busy to respond.  
>
> Has anyone on this list performed this conversion?  Has it worked well?  I
> have a couple of 2B's, one of which is a good candidate for this conversion.
> Is there someone out there who can help me with the specific way to do this
> mod?
>
> Thanks es 73,
>
> Chris
> W7JPG
>
>
>
>