POW KW+ keying circuit

[nomadradio]

I do have one suggestion. The coax leading from the Load control to the relay does not have the shield braid connected. This was a bad habit somebody must have learned from Maco. Connecting the braid to a ground lug on the Load control, and running a wire from the rear end braid to a ground lug on one of the Antenna jack screws tends to make the driver tuning more stable. I just unwrap a half inch or so of the black jacket at each end without taking anything loose. A short piece of stranded hookup wire gets wrapped around the exposed braid and soldered. The other end of each wire gets grounded at that end.

Whether or not the driver Tune control gets twitchy when you turn it, we ground each end of the output-coax braid as a preventive measure.

73

 

[Trainman 8274]

I do have one suggestion. The coax leading from the Load control to the relay does not have the shield braid connected. This was a bad habit somebody must have learned from Maco. Connecting the braid to a ground lug on the Load control, and running a wire from the rear end braid to a ground lug on one of the Antenna jack screws tends to make the driver tuning more stable. I just unwrap a half inch or so of the black jacket at each end without taking anything loose. A short piece of stranded hookup wire gets wrapped around the exposed braid and soldered. The other end of each wire gets grounded at that end.

Whether or not the driver Tune control gets twitchy when you turn it, we ground each end of the output-coax braid as a preventive measure.

73

Hi Nomad,

Thank you for the suggestion! I was wondering if one end would work or both. I will do both, hopefully this weekend. Does the wire size matter when grounding?

73

 

[linearone]

Hi Nomad,

Thank you for the suggestion! I was wondering if one end would work or both. I will do both, hopefully this weekend. Does the wire size matter when grounding?

73

Do a ground connection at each end of the coax. Use whatever you have on hand.

 

[nomadradio]

We use #22 stranded for amplifiers that size. A solid wire is fine so long as you get it to wrap around the exposed end of the shield.

And like the man said, both ends.

73

 

[Trainman 8274]

Thanks for the help! Next question… How much drive will this thing take? Not that I’m going to drive it that hard.. Tubes aren’t cheap! I’m just curious.. I tried it with a Grant LT and Galaxy 86V on am.. It doesn’t seem to swing very much.. I may not have it tuned right… It has a knob on the side and tune and load on the front.. So, what is the correct way to tune it?

Thanks!

 

[nomadradio]

First thing to check is for the "twin peaks" on the Plate Tune knobs.

With the Load control set for max modulated power, spin the driver tune on the side. It should show a peak at *TWO* separate spots in one 360-degree turn of the knob. The peaks might be close together, or they might be 180 degrees apart. The important thing is to see that you have two peaks. If there is only one, a glance at the plates on that control will reveal that they are at one or the other extreme of adjustment. Plates fully apart, or fully meshed together. When you see this, the coil attached to that control has to be adjusted. This rule also holds for the front-panel final Tune control.

Until both Tune controls show those two peaks at a spot in between the two extremes of adjustment, you'll typically lose some power.

Running it with either Tune control at "just one" peak can be hard on the tubes.

The tiny adjustment screw on the rear panel gets set with a SWR meter and a coax jumper added between the radio and amplifier. Once it's tuned up for max modulated power, see what the drive-side SWR meter reads. The rear-panel screw is the input tuning and should be set for minimum SWR while the amp is keyed. Makes life easier on the radio.

Any of those can hold back the power.

73

 

[Naysayer]

Amplifier layout and chassis reminds me of the Elkin amps.