[IRCA] Great Sensitivity Improvement for ULR's ... Little Work (and No $$) Required

[D1028Gary@xxxxxxx]

Hello All,
 
     If you have an SRF-59, SRF-39FP or a DT-200VX  ultralight radio and 
would like to get an extra edge in sensitivity, there is a  very simple change you 
can make... which gives great results.
 
     First discovered by Guy Atkins in DT-200VX  experiments, the simple act 
of placing the loopstick outside of the cabinet not  only provides a major 
boost in sensitivity, but reduces interactive noise with  the other receiver 
components, provides greater isolation to enhance  nulling ability, and improves 
coupling to external signal-boosting accessories  (Q-stick, Booster Bars, etc.).
 
     For the DT-200VX, after opening the back  cover, remove all glue bonding 
the tiny loopstick to the plastic posts, and  remove the black tape patches 
holding the antenna lead-in wires in  place.  Gently remove the tiny loopstick, 
and place it outside the cabinet  (where it can be secured by mounting on an 
insulating material of  choice).  A low-band alignment can also be easily 
performed, by shifting  the coil along the ferrite bar to peak a 600 kHz (or 
thereabouts) weak  signal.
 
     For the SRF-59/39FP, carefully note the exact  dial position at the far 
left stop, then remove the two screws and  battery.  Carefully separate the 
front and back halves, and if using an  SRF-39FP, carefully pry the positive 
battery terminal out of its slot. With  a very small flat-bladed screwdriver, 
carefully break up and remove all the  yellow material around the four antenna 
connecting terminals, and break the glue  bond holding the loopstick to the 
circuit board. Take care not to cut the small  antenna wires during these steps. 
Lift the loopstick from the circuit  board.
 
     All of the SRF-59/39FP antenna wires except  terminal #2 (the tap point 
wires) have enough slack to be mounted outside  the cabinet.  For the tap 
point wires, to provide slack, remove one  turn from each side of the tap point, 
and temporarily desolder one side from  terminal #2.  Route the tap point wires 
so that the loopstick may be  mounted outside the cabinet, then resolder the 
second tap point wire to  terminal #2. To avoid pinching the small antenna 
wires, sand or cut a small  routing slot in the back panel, to accommodate the 
antenna wires.  Place  the loopstick outside the top of the cabinet, and follow 
the following  steps to reassemble the radio.
 
     Place the orange dial needle at the exact point  noted before 
disassembly, and ensure that the tuner is still set at the lowest  frequency (max CCW).  
Carefully attach the circuit board to the front  panel, observing the battery 
terminal slots and tuner gear alignment. Do not  force the tuner gears-- 
separate and try again if there is binding.  Once  front panel is securely in 
place,  RF alignment may be performed, if  desired (strongly recommended).  Attach 
back panel to front panel, routing  the antenna wires through the previously 
cut slot. Secure the back panel with  two screws, and reinstall battery.  
Secure the loopstick with tape or other  insulating material, preferably with a 
slight separation between loopstick and  cabinet.
 
     This configuration should provide a serious boost  in sensitivity over 
stock units, as well as slightly improved nulling  ability. It should also 
provide greatly superior coupling to external  devices such as the Q-Stick, 
Booster bars, blank ferrite bars and other external  devices.  If you have an extra 
SRF-59, SRF-39FP or DT-200VX laying around  (or have the desire and ability to 
modify your one and only unit), why not give  it a try?  Outside of the 
hard-core transplants of huge, ultra-sensitive  loopsticks, this new class of ULR's 
is the most sensitive group  available.
 
                                                                              
   73,  Gary  DeBock        



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