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Monday, January 30, 2012

My .02 KW Linear Amplifier

Once again, die-hard QRP guys should probably look away at this point...

My Cycle 23/Cycle 24 refurbishing project continues. The JBOT amplifier in the 17 meter SSB rig is now working nicely, but unfortunately just as I got ready to make some contacts, the Coronal Mass Ejection hit us and conditions on 17 deteriorated badly. Looking for something to do, I noticed that in some pictures of my old Azores station, sitting alongside the SSB transmitter there was a small cabinet with a QRO/QRP switch on the front panel. Ah yes! My Ramsey Kit linear amplifier! This is a MOSFET-based device. Mine was designed for 20, but I changed the low pass filter and put it on 17. Later, in Italy, it went on 20 meters and for some reason I went back to the 20 meter low pass filter.

Yesterday I blew the dust off this thing, pulled out the 20 meter LP filter and replaced it with a filter that will let my 17 meter RF reach the antenna. Today I fired it up. Wow! 20 Watts! Look out 17 meters!

I really like the QRO/QRP switch -- it gives me the opportunity to lean back and say (just like the big guns) "Wait a second Old Man, let me turn on my LINEAR!" I even have a little fan in the box that you can hear when I go to the QRO position. Unfortunately it doesn't make the lights flicker. But we can dream...

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  1. If a gallon is a KW then your little blaster would be 4 Teaspoons :-).

    Do you wear proper body protection when operating that bomb? I think Ramsey amp's. are better known as smoke and flame generators, HA! You and OM Roberto XE1GXG are brave souls, indeed.

    OK, I confess; I have one of those languishing in the ol' junque box. I'm trying to work up enough courage to fire it up :-)

    73.......Steve Smith
    Snorting Rosin and ducking

  2. Wait a sec, wait a sec...my Ramsey P.O.S. (guess what that stands for) amp has several hefty modifications, e.g. bigger resistors across the 16NF06 MOSFETS, my super-duper glued-together transformer, and the silly RCA connectors have been replaced with BNCs. Speaking of QRO, these past weekend club station XE1TD participated in CQ 160m CW. It was fun to operate CW with the big Kenwood linear putting out all of 500W into a full size dipole in the outskirts of Guadlajara. In the spirit of contests, only cheap Costco coffee was consumed (instant) to go with the quesadillas...now back to the Rockmite at 400mW...need a QRPp-QRP option...maybe the Farhan Justa Bunch amp is the way to go!!

  3. Roberto,

    I think the JBOT would make a good "tail end" to a RockMite (or any other radio in that power class). You can probably lop off the driver and simply drive the P-P final directly.

    73.......Steve Smith WB6TNL
    "Snort Rosin"

  4. I should have said, "lop off the pre-driver.."



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