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Originally Posted by Oskar.B
Switching in the ATU (connecting different taps of the matching coil, moving cap to left, right side of coil). At my power level (25W approximately), can this be done with "regular" spec switches?
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Allow me to attempt to answer this one with a firm and clear 'Hmmm...?".
This one is impossible to answer in the general case I'm afraid. The classical solution is to use something like high quality banana plugs and sockets, moving the wire by hand (with no RF power applied, of course.)
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Originally Posted by Oskar.B
Just wanted to know if I absolutely, definetly need RF-high-voltage-switches. It's hard to tell exactly what voltages will be present in the ATU. But say 200 volts maybe?
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By definition the impedances an ATU/transmatch will encounter are unknown. Yet my experiences leads me to conclude that at 25W you will have to be fairly unlucky for almost anything you can make
not to work. Save the high quality switches for the KW amp, which will be down the road some day.
Where you may run into problems is if you accidentally encounter a very high impedance at a point, where a less than perfect insulator touches a conductor. That is what happened to the nylon coil form, which I mentioned catching fire at 100W.
Truth be told, then I'm more worried about you switching the B+ to the modulation transformer, than what might happen to the switches in your ATU. Do I smell burned out modulation transformer insulation?
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Originally Posted by Oskar.B
You can never have enough of them junk-boxes.
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Absolutely. Also makes for fun digging experiences, as you come across something you had forgotten was in your possession.
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Originally Posted by Oskar.B
Allways something missing . I'm looking around for some koax connectors too, they're not cheap! |
You don't need BNC or N connectors for this project. SO/PL-239 will do quite nicely. Also remember to add an independent safety ground bus wire between the PSU and the TX. I usually add a M8 or M6 bolt, nut and wingnut to the back of all my homemade projects for this very purpose.
No progress on my project today, as I got sidetracked by finding a box of valves in my junkbox, which I just had to test then and there. The bounty of the valves that work includes 7x EL84 and 9x EF80.
Frank N.