Ramsey Electronics AA7, Instruction Manual

AA7

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rather than only a receiver or scanner, make sure it is not possible to  transmit 
by accidentally pressing a mike button or CW keyer. Transmitted RF into the 
AA7 is likely to ruin one or both of the transistors. 
 

Transistor Placement Information: 

   Both transistors may be ordered from Ramsey Electronics, but they also may 
be found at a local electronics parts distributor.  You may use either "SK" or 
"ECG" replacements: 
 
              3N201 = ECG454 or SK3991 
              2SC2498 = ECG10 or SK9139 
 

LED Power On Indicator 

   A visual power on indicator can be an enjoyable and practical enhancement 
of your completed kit. LEDs (Light Emitting Diodes) are available at low cost 
and are ideal for this purpose, providing you don't mind the extra current drain. 
Voltage for a standard LED is easily taken from the appropriate top terminal of 
S2.  The sw9V terminal is the middle of three terminals in the row 
nearest the center of the PC board.  This positive DC must be connected to the 
anode (longer wire) of the LED. The cathode lead is connected through a 
proper current limiting resistor of about 1K ohm to the closest PC-board ground 
point.  (Note: This can be locations such as the black wire of the battery, the 
mounting case of either jack, but it CANNOT be the antenna.)  Mount the LED 
at any convenient point near the switch. 
 

TROUBLESHOOTING GUIDE

   The fact that there are two independent preamplifiers makes the AA7 easier 
to diagnose than many other devices. If a problem occurs only when S1 is 
pressed inward, troubleshooting can be concentrated on that part of the circuit. 
If the problem is common to both settings, then the components and 
connections common to both preamps should be checked. Make sure you 
have not omitted any of the jumper wires required. 
 
   There are other characteristics or phenomena associated with preamplifiers 
and active antennas which do NOT mean that your AA7 is malfunctioning: 
 

Strong AC hum in the HF setting:

  The antenna is too close to an AC cord or 

power line, and/or the RF gain is set too high. 

 
HF signals stronger at VHF than at HF setting:

  As explained in the AA7 

circuit description, either preamp may be used for HF. Signal strength will be 
greater with the VHF preamp, but the HF signal-to-noise ratio should be better 
with the dual gate MOSFET HF section.