|[AMRadio] 1930's Old Buzzard Open Rack Transmitter
brett.gazdzinski at verizonbusiness.com
Tue Feb 21 19:45:46 EST 2006
My coil assembly uses a plug in link, using banana jacks.
40 meters is a 3 turn link, 80 meters is a 6 turn link.
160 meters would likely be 8 or 9 turns...
> -----Original Message-----
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Donald Chester
> Sent: Tuesday, February 21, 2006 6:56 PM
> To: amradio at mailman.qth.net
> Subject: RE: [AMRadio] 1930's Old Buzzard Open Rack
> Transmitter FinallySeestheAirwaves!
> >The amount of turns on the link coil impacts what you can
> load up to a LOT.
> >I made my own link for the 812a rig, and had to try various
> link turns
> >it loaded up right. I have the series cap also, and that
> does change how
> >rig loads up, but does not seem to change the efficiency or
> anything else.
> I use a series cap on both my homebrew rigs for 40m and 80m.
> However, even
> with higher capacitance, it wouldn't work on 160. I could
> hit resonance and
> get some loading, but even with the link shoved in all the
> way, it would
> load up maybe 25% of full loading.
> Using trial-and-error I eventually came up with a solution
> that works with
> both transmitters. I put two fixed mica caps in series -
> somewhere about
> .0015 mfd each (not out in the shack where I can look at
> them) - whatever
> value it took to resonate the link with the 2 caps in series.
> I have a 1000
> pf variable in parallel with one of the fixed caps for fine
> tuning. The
> coax cable goes across the other capacitor. The link
> operates as a parallel
> tuned circuit, with the load tapped down using a capacitive
> voltage divider.
> With that lashup I can fully load both transmitters on 160
> with the link
> about 65% into the tank coil.
> The series capacitor would probably work on 160 if I had more
> turns on the
> link. Both my links use 4 turns, and I use the same link to
> load up on 40,
> 80 and 160. I suspect 8 or 10 turns would do the trick, but then it
> probably wouldn't work right on 40. I wired up a switching
> using a 4-pole DT switch to go from the 80/40m circuit to the
> 160m circuit.
> Don k4kyv
> This message was typed using the DVORAK keyboard layout. Try
> it - you'll
> like it.
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