What made you go with a roller instead of a tapped coil? Also curious what gauge the new coil is and what Q your shooting for.
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driving a sb220
- Thread starter Number15
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What made you go with a roller instead of a tapped coil? Also curious what gauge the new coil is and what Q your shooting for.
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No bandswitch to burn up basically and better selection of the optimum L to C ratio instead of selecting the best tap for the entire band. Not sure the gauge, it is edge wound ribbon and came from an old broadcast TX or possibly a military TX. It is good for several Kw in any event. Ultimate Q has yet to be determined.
Roller inductors are nice but do not overlook the need to keep them clean and dust free. Neglect this long enough and sooner or later the contact will line up with a dirty spot on the coil and arc trough. Pitting the silver on the coil and contact. Inductors with double, sliding contacts are the best for this application because they tend to clean the surface as they slide. The pair of contacts also reduces the possibility that a bad connection will form at both contacts simultaneously. Avoid the temptation to find the tuning "sweet spot" while keyed. Changing the setting under load is an invitation for this type of problem.
Roger that. I was looking at the long roller next to the ruler and trying to guesstimate what gauge it was. Going by Richard Measures' math Q x plate current = circulating current it looked kind of light duty for a 3cx3000.
That's not the roller inductor I plan to use. That inductor in the picture is actually edge wound silver plated ribbon 3/8 inch wide and is not a roller type. It was used in an AM transmitter site ATU system and it will handle several Kw in SSB service. As for the 3CX3000A7 output.........this amp is not for 11m so balls to the wall is not planned.
My legal limit here is 2250 watts pep on SSB or a 750 watt carrier on AM or 3 Kw pep on AM. Not really interested in much more than that. Just looking for a very rugged amp that will take a beating especially on AM. I had all the parts scrounged from my broadcast days except a filament transformer which was given to me by a fellow broadcast tech still in the business.Interesting. I can get 3kw out of mine using 100 watts less drive than you. Before I get jumped on, I rebuilt the 220 using all the new upgrades and the 3 500zg tubes. But to swing 400 in? Just plain stupidity and needless if modded correctly.well i drive mine with a brute force 350
so the saturn 2 swinging 50 into the brute force 350 keying 150 swinging 350 into the SB220 which keys 300-500 swinging 3000
and redone for 220volts again the 110 was blowing a AC breaker at 20amps
don't max it over 400 into the sb220 and you will be fine
and min is about 125 to get some good output
thats just my opinion of everyday use which works great
Well, my shack has an amp capable of 6kw, but I slow cruise it at 3.8. No need for more if my system is perfect and I own skipland.