[AMRadio] Gates BC-1T


A.R.S. - W5AMI ars.w5ami at gmail.com
Tue May 8 11:20:45 EDT 2007


Don,

Embedded replies/more questions below:

On 5/6/07, D. Chester <k4kyv at charter.net> wrote:
>
> "I'd also like to hear from anyone that has tuned it to 160.  Will it go
> there without mods, other than re-tapping coils, etc."
>
> I changed out the fixed capacitors in the output circuit.  Scaled them all
> down proportionally from 1230  kc to 160m, and reduced the number of active
> turns in the fixed coil.   Whether or not you can just retune it depends on
> the original broadcast frequency.  I suspect you could just retune it if the
> original frequency was at the top end of the BC band.
>
Do you recall what values of fixed capacitance on C11 - C14 did the
trick for 160?  I'm also seriously wanting to allow it to go on 80
too, but that might require some sort of variable cap, or pop-in fixed
caps in series with the others.  If you were to dual band it, what
would you do on the output section?  Or ....would you even consider it
;)


> "What sort of drive do the drivers require from an external VFO, exciter?"
>
> I modified the oscillator unit in mine.  Changed the xtal oscillator stage
> into a grounded grid VFO buffer.  Grounded the control grid, disconnected
> the feedback capacitor from the cathode, and ran a coupling capacitor to a
> BNC  connector on the back of the osc unit to feed the VFO output to the
> cathode of the 12BY7.  It drives well with 50 ohms output from the VFO @
> about 200-250 milliwatts.
>
> I removed the frequency adjust capacitors from the xtal oscillator, and
> mounted a variable capacitor with a real shaft  for a knob in the place of
> one of the xtal frequency adjust trimmers, and used that capacitor to tune
> the resonant circuit between the 12BY7 stages from the front  panel.
> Otherwise, you have to open the transmitter, remove the cover  from the osc
> unit, and take an insulated tuning wand to adjust the slug tuned coil every
> time you change frequency.  I had to remove about 1/3 of the turns  from the
> slug tuned coil to make it resonate all across 160m.

Same here Don, I wonder if L3 and C9 on the output of the osc would
have enough range for 80 meters.  Of course I can't forget the output
of the driver stage either.  Looks like I would have some concern with
C15 and C7.  C15 in particular since it's fixed.

Was the plate choke on the finals (L9 I think) okay, or did you have
to replace it with something else.  I guess I could wait and see if it
smokes ;)  Ameritron and P. Dahl has some nice ones that will easily
cover 160 and 80 meters.

BTW, thanks to all who have responded with the very helpful info.
I've got a folder growing in thickness with all the notes.  I should
be getting the transmitter next week or the week after.  Also, in case
anyone finds a large transmitter that is too far to drive for pickup,
there is a special service provided by North American Van Lines just
for this sort of thing.  Email me directly, and I can put you in touch
with the right person.  The price w/insurance will be a lot less than
what you might think.  You don't have to do anything, nor does the
shipper.  They take it from the seller, and bring it right into your
shack, or wherever you want it.


73
Brian / wa5am
ex - w5ami



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