{Collins} Re: KWM-2A Neutralization, 6146W's



Scott:
The important thing is to measure the RF out at the Dummy Load, while you're doing Neutralization. You always neutralize for minimum RF out, as given below.

There are three separate steps to Neutralization, being Final, Driver, and Negative Feedback, in that order.

The following are the Neutralization Checklists from my Notes.

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John Painter
W5LQS
  a.. NEUTRALIZATION PROCEDURES:
  1.. First, mark (label) C117 and C120, so they won't be confused during procedures.
  2.. Remember to re-peak Exciter and re-dip PA, each time any neutralization capacitors are changed.
PA Neutralization Adjustment Steps - Checklist:

  1.. High Voltage (+800 VDC) - Disable. (Remove 5R4 from 516F-2)
  2.. PA Screen Voltage (+275 VDC) - Disable: pull PA Disable Jumper, Jacks J5, J6. (Unsolder it, if it's hard-wired).
  3.. Monitor RF voltage across Dummy Load (use scope or RF VTVM).
  4.. Band Switch - 28A. Tuning Dial 100.
  5.. Meter Switch - Grid.
  6.. Emission Switch - Lock.
  7.. Grid Current - Max. (Use Exciter Tuning and Mike Gain.)
  8.. PA Tuning - Max. RF voltage on Dummy Load.
  9.. Mike Gain - Set RF voltage on Dummy Load to 0.5 VRMS or 1.4 V. pk to pk.
  10.. Neutralizing Capacitor, C184 - Tune for min. RF voltage out.
  11.. The neutralizing capacitor is mounted on the "floor" of the High-voltage cage. Access to the screwdriver adjustment is from below the chassis.
Driver Neutralization Adjustment Steps - Checklist:

  1.. Driver neutralization requires the Final Amplifier fully powered up.
  2.. Substitute a 6CL6 Driver tube with cut-off heater pins (4 and 5).
  3.. Monitor RF on Dummy Load.
  4.. Band Switch - 28A. Tuning dial 100.
  5.. Meter Switch - Plate.
  6.. Emission Switch - Lock.
  7.. Exciter and PA Tuning - Max. RF voltage out. (Use Mike Gain.)
  8.. Mike Gain - Set RF voltage on Dummy Load to 0.3 VRMS or 0.8 V. pk. to pk.
  9.. Neutralizing Capacitor, C117 - Tune for min. RF voltage out.
  10.. Viewed from under the chassis, the neutralizing capacitor is the right-hand ceramic capacitor, mounted to the right of the feed-thru capacitors.
Negative Feedback Adjustment Steps - Checklist:

  1.. Feedback neutralization requires Final Amplifier and Driver fully powered up.
  2.. Band Switch - 28A. Tuning Dial 100.
  3.. Meter Switch - Plate.
  4.. Emission Switch - Tune.
  5.. Exciter Tuning - Peak Plate Current.
  6.. PA Tuning - Dip Plate Current.
  7.. Emission Switch - Lock. Repeat Exciter and PA max and dip procedure.
  8.. Feedback Capacitor, C120 - Adjust so that Plate Current dip and Grid Current dip coincide.
  9.. Check that Plate Current and Grid Current dips coincide on 21.3, 14.15, 7.15, and 3.7 MHz.
Viewed from under the chassis (rig upside down), the neutralizing capacitor is the left-hand ceramic capacitor, mounted to the right of the feed-thru capacitors.

----- Original Message ----- 

From: "Jan Erik Holm" <sm2ekm@xxxxxxxxx>
To: <collins@xxxxxxxxxxxxx>
Sent: Monday, January 10, 2005 10:15 AM
Subject: {Collins} Re: KWM-2A Neutralization, 6146W's


When, plate current dip (minimum)= output power max
the thing is neutralized.

73 Jim SM2EKM
-----------------------------------------------------

Freeberg, Scott (STP) wrote:
> 
> I've never neutralized anything before so I have to ask how do you know =
> if the neutralization is good or bad? I didn't know this so I couldn't =
> judge how good the neutralization turned out.=20
>  
> 73, Scott WA9WFA
> CCA98-762=20

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Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
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