OK, so after Nomad's note, my curiosity got the better of me. I tested "pass through" SWR of the Hygain without the input match components. The tests were done through the antenna. Shhhhh! (I don't have a dummy load)
The picture below is without theHygain in-line, transmitting on AM. The Pace tester is showing about a 1:7.1 SWR. The SWR meter on the radio is showing about 1:4 or 1:5.1. (To be as detailed as possible, after leaving the Pace meter, the signal goes through a 2 position coax switch, into another amp, into a TVI filter, into an MFJ meter then on to the beam.)
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The picture below is through the Hygain amp with only the control grid modification performed. There is -7.11vdc on the control grids. The rest of the amp is "stock" (that doesn't mean too much since the amp was built around 1974).
As you can see the Pace meter is now above 3:1 as is the SWR meter on the radio.
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It will definitely have to have the cathode tune modification to make this usable. At least I can now see the difference that the cathode/input tune modification will have.
My goal with this process was to clean up the SSB signal, allow the tubes to last a little longer, keep the amp a little cooler and not hurt my "like new" 139XLR.
Stay tuned.
73's
David
