Hi, to all at GQRP,

Thank you  to Hans and Arv for the work they've done with regard to 
the superdrg radio as reported on the GQRP mailing list.

1)  Following the tip-off I obtained two of the said radios. Rushing 
home to check them out I found that neither of them worked!  I tried 
numerous batteries including fully charged (> 1.3V) NiHMs and brand 
new Alkelines. Still no joy. Rather than return them I opened them up 
and noticed the poor quality of the soldering. I spent around half 
an hour touching up dry joints etc. Still no luck. Finally, in 
desperation and suspecting the battery connections I cut the wires to 
the battery connectors and made direct connections to a bench variable 
power supply. Lo and behold the radio burst into life at approximately 4V!

Further experiments suggested that it operates fine with supply voltages 
of up to 8V. Subjectively, I found that on AM and FM, at least, 
sensitivity  and overall audio power output was good with sensitivity 
increasing significantly at the higher supply voltages.

Mine, at least, seems to work only at supply voltages of > 3.5V. Seems 
there is some sort of quality control problem. Perhaps this is why 
they are so cheap. Or maybe I was just (very) unlucky. I wouldn't 
recommend operating the radios at the higher voltages, especially 
with the volume turned up, but at least my experience suggests it 
won't cause any damage in the short term. I've found that 3AA 
cells (V ~ 4.4) seems to work nicely.

2) Today, armed with the data sheets obtained Hans' web page I 
investigated further concentrating my attention on the LCD/frequency 
counter module. Although I haven't fully analysed the functionality 
of the module I have come to the following conclusions:

  a) the red and black wires connected to the two holes immediately
     underneath the LCD unit, looked at from the front, are the FM
     and AM (or non-FM) local oscillator inputs. The one on the left
     AVFTF is the FM input, The one on the right is the AM input.

  b) When there is no input via the AMin pin, and non-FM mode
     is selected the frequency counter displays 9545  i.e.
     9.999 - 0.455 MHz approximately. Similar behaviour
     was observed with the FM and SW modes.

  c) I tried feeding the output of the VFO from my homebrew 80m
     superhet directly into the AMin pin via a 1 microfarad
     capacitor, having disconnected the radio's input to the
     counter. The signal level put out by my VFO is approximately
     0.1-0.3V as measured on a scope. No additional earth connection   
     was made - though one might well be advisable.

     The freqency counter worked first time! Selecting the
     appropriate mode for the radio and I had a display of the
     frequency to the nearest 1Khz. With a long piece of wire
     drapped across the bench in this lashed-up arrangement there
     was considerable evidence of noise pick up i.e. the last
     digit kept changing by +- 1 or 2 units.

  d) I turned my attention to the 8 way ribbon connector (which
     incidentally has solid cores making stripping and reconnection
     easy). A little proding with a DMM and tracing of the circuitry
     armed with the data sheets etc,. leads me to the following
     tentative identifications for the wires  (labelling them 1 to
     8 from top to bottom as viewed from the front)

       1.     4.37V measured if main slide switch in AM position
              (4 digit mode select?) otherwise 0V
       2.     4.37V measured (low frequency counter mode selected?)
       3.    0V - ground connection
       4.    Power in 4.37V using 3AAs
       5.    AM switch output to rest of radio
       6.    FM switch output to rest of radio
       7.    Switched power to rest of radio controlled by switch
              on LCD module
       8.    Not sure of function

   e) Armed with these hypotheses I proceeded to cut the ribbon
      cable and  connected 3AA cells across ribbon cable lines 3
      and 4. Feeding the VFO signal into the AMin pin I observed
      that with no further connections the display read 3712Khz or       
      there abouts. Nothing could have been simpler! A shortened
      VFO to AMin wire now means that the last digit of the display
      is (touch wood) rock steady. The 10Hz sampling rate of the
      counter means that tuning is nice and smooth.

       I now have  a fully functioning frequency counter for my
       80m superhet. As a  bonus I also have a front panel clock
       and back light, all for 2.99!

3) I'm fortunate in that my superhet is built around a filter strip    
   based on 455Khz 2-pin ceramic resonators thus I automatically
   get a fairly accurate readout of receiver frequency - I say
   'fairly accurate' because I now need to do some more work on
   modifying/aligning the filter - currently my frequency counter
   reads 14Khz low - but this should be easy enough to correct for
   by adding some trimmers.


73s and happy experimenting,

Rick Peterson   2E0JSI/M3JSI