[Johnson] Johnson Adventurer/122 VFO power question

[SX-25]

Carl,

Thanks for your helpful information. I have carefully went over my Adventurer manual and it does not contain this excerpt so I have printed out your email and included it in my manual for future reference.

I appreciate your taking the time to clear this up because I could not understand why Johnson would leave the Adventurer owners hanging.

Thanks again and hope your New Year is happy, healthy and safe.

Vern WA9VLK





From: Carl Nord 
Sent: Wednesday, December 31, 2008 8:43 AM
To: 'SX-25' ; johnson at mailman.qth.net 
Subject: RE: [Johnson] Johnson Adventurer/122 VFO power question


Hi Vern,

 

The following is from the Adventurer manual

 

VFO EXCITATION:

 

The Johnson Adventurer is designed for VFO input as well as crystal operation. The VFO input is to the left of the crystal socket on the front panel and requires a two pin plug (Millen type 37412 or equivalent). If one side of the transmission line from the VFO is grounded such as the shield on a coaxial line, this ground side should be connected to the top pin of the VFO input socket. The output of the VFO should have a 50 to 150 mmfd isolation capacitor in the grid lead (bottom VFO pin) to avoid placing a DC short on the input grid.

 

If the Johnson Viking Model 240-122 VFO is used, a 1OK ohm 4 watt resistor should be connected between pins #3 and #4 on the power socket (this may be two 20K ohm 2 watt resistors in parallel, two 5000 ohm 2 watt resistors in series or a single 10K 4 watt resistor) R51, the 18K 2 watt resistor in the VFO, should be changed to a 20K ohm 10 watt resistor. These changes are required for correct operating voltages and power dissipation for the VFO. The lead from pin 8 of PLS1 should be changed at the key jack J50 so that it will be connected to the ungrounded side of C69 (at key jack). After these changes have been made, the VFO power plug may be inserted in the socket at tsar of the transmitter and the RF output from the VFO connected to the VFO socket (the center coaxial conductor to the bottom VFO input pin). Since the keying circuit is connected to the VFO keying circuit through the power plug, the key should be plugged into the VFO. This keys both the VFO and the transmitter.

 

Carl
WA1KPD
Visit My Boatanchor Collection at http://home.comcast.net/~chnord/wa1kpd.html

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