Don, Embedded replies/more questions below:
On 5/6/07, D. Chester <[EMAIL PROTECTED]> 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 ______________________________________________________________ AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
