Now that I think more about this a small box with a small power XFMR of 20-30 watts would do the job. Of course you would need to re4ctifiy and filter but you could choose full wave center tap, full wave bridge, voltage doublers or quadrupler. I found that adding a input capacitor to a choke input supply raises the voltage output just about enough to double the power or vise versa. Then you could just forget the HV in the Ranger, as for as plate/screen supply is concerned. Or if a guy was home brewing a modulator of 20 watts or so, he might just use the PS from it.
John, WA5BXO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John E. Coleman (ARS WA5BXO) Sent: Wednesday, November 16, 2005 3:32 PM To: 'Discussion of AM Radio' Subject: RE: RE: [AMRadio] Re: Need list of good AM radios to start lookingfor. You are correct of course Jim. I would mount the resistor in its own case and construct a cable so as to plug the modulator into the new chassis with the resistor and bypass cap, and then the new chassis would plug into the Ranger. To conserve power and heat, another power supply with lower voltage output or variable output would be better. But some time you do with what you have and if the 2000 ohm 50 watt resistor is handy and you have an old scrap chassis well there you go. I once needed a stiff bias supply so I used a single diode and 400 uf filter right off the AC line. Then I placed a 100 watt lamp in series with a large variable 100 ohm 100 watt resistor to ground. Not a very efficient thing to do but it did hold the bias steady on the 805s modulator. This was long before I had access to the HV transistors, ETC. John, WA5BXO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim candela Sent: Wednesday, November 16, 2005 3:37 PM To: Discussion of AM Radio Subject: RE: RE: [AMRadio] Re: Need list of good AM radios to start lookingfor. John, If you go this route with a series dropping resistor, think about the heat and safety of the modification. On the Central Electronics 20a VFO (modified BC-458, arc-5), there is a similar resistor on the back of the chassis that drops the B+ from about 300 to 105 volts (OC3?). The connections are bare, and the resistor gets so hot it will burn you in a split second, and if the heat don't get you the B+ will! I been burned and shocked several times. I keep saying that I'm going to make that more safe, but I never do. I cannot recall if the ranger has keyed HV B+ like a Viking II. If it does, maybe you can use a relay to switch the LV B+ to the final and modulator, and key the relay with the transmit switch. This way you won't have to use a dropping resistor from the HV B+. Those folks that know Rangers out there can jump in to clarify a yah or nah on this idea. Regards, Jim WD5JKO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John Lawson Sent: Wednesday, November 16, 2005 3:22 PM To: Discussion of AM Radio Subject: RE: RE: [AMRadio] Re: Need list of good AM radios to start lookingfor. On Wed, 16 Nov 2005, John E. Coleman (ARS WA5BXO) wrote: > > The best way is still to reduce the supply voltage at the > plate/screen modulation point. A large resistor that has a bypass cap > across it works well. As has been wisely pointed out to me - in the case of the Ranger, placing a suitable variable resistance in the plate line will accomplish this handily, it seems - unless I'm missing something very obvious. These wires are conveniently brought out to pins 2 and 6 on the rear octal plug, with 6 being the line from the supply to the mod trans secondary, and 2 being the 'start' of the secondary. The 'finish' goes to pin 3, and the line to the final plate goes to pin 5. These are jumpered in the mating plug. I'd be inclined to reduce the voltage before the mod trans - thus reducing the DC saturation a bit. But that's probably Nit #68 in the grand scheme of things... Cheers John KB6SCO PS: I'm going to try this, perhaps this weekend if I can get a spare hour of bench-time on it. ______________________________________________________________ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.362 / Virus Database: 267.13.3/172 - Release Date: 11/15/2005 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.362 / Virus Database: 267.13.3/172 - Release Date: 11/15/2005 ______________________________________________________________ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami ______________________________________________________________ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami
