P220 VHF Preamp Parts List:

The preamp's input is closest to the coil L1.

C1 - 5pF (5) ceramic disc
C2 - 10pF (10 or 100) monolithic ceramic (yellow)
C3 - 5pF (5) ceramic disc
C4 - 10pF (10 or 100) monolithic ceramic (yellow)
C5 - 100pF (101) ceramic disc
C6 - 1uF (105) (yellow) monolithic ceramic
C7 - .01uF (103) (blue) monolithic ceramic

R1 - 100k - 5% (brown - black - yellow - gold)
R2 - 470 ohm - 5% (yellow - violet - brown - gold)
Above resistors are 1/8 watt.

R3 - 22 ohm surface mount *Pre-Installed
R4 - 47 ohm surface mount *Pre-Installed
R5 - 22 ohm surface mount *Pre-Installed

L1 - 1.750 inch (1-3/4") - #24 AWG copper magnet wire.  This 2.5 turn coil is created by 
winding the magnet wire around a 9/64" (.141 inch) drill bit.  Wind the coil in the 
direction shown in the photos so the coil will install properly onto the PC board.  
Wind the coil with lots of spacing between turns.

Tin the ends by burning the insulation off with a soldering iron.  This is done by melting 
solder around the wire.  It takes time, but the insulation will eventually burn off, leaving 
a nicely tinned wire.  Tin a distance of approximately 1/8 to 3/16 inch for insertion into 
the printed circuit board.  DO NOT trim any wire from the length, and insert the coil into 
the silkscreened side of the board with very little sticking through. Proper alignment is 
when about 1/32" to 1/16" is between the coils bottom and the surface of the board.  Solder 
the wire into the holes, and trim any excess lead length (on the soldered side) as necessary.

Adjusting the coil is done with a small plastic tool or tooth pick. Adjust the pitch to tune 
the preamp to your desired frequency, or best noise figure if you own such equipment.  

The coil shown in the photos is tuned for 220.000 MHz.

Adjusting the coil for maximum gain usually results in a little more than 11 dB of gain, 
2 dB noise figure, and around 16 to 18 dB of input return loss (a match of 1.29 : 1 VSWR).


LP - Printed circuit choke (part of the printed circuit board traces)

Q1 - 2SC2570A Transistor

J1 & J2 - SMA female board mount connectors.

Masters Communications P220 circuit board