[AMRadio] 1930's Old Buzzard Open Rack Transmitter


Brett gazdzinski 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...

Brett
N2DTS 

> -----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
> >before
> >it loaded up right.  I have the series cap also, and that 
> does change how
> >the
> >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 
> arrangement 
> 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 
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> 
> 
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