RE: [AMRadio] Matching a 100 watt PA am to drive 833'S
Perhaps I missed it but why would you want to change the 845 driver circuit, are you missing the tubes? John, WA5BXO
Re: [AMRadio] Matching a 100 watt PA am to drive 833'S
In a message dated 1/5/05 3:49:42 PM, [EMAIL PROTECTED] writes: > I think it would be a terrible mistake to mutilate a high quality > transmitter by going from a design as superbly engineered as the BC-1F, and > converting it to something as jury-rigged as using a power transformer for a > driver transformer, or one output transformer feeding a second reverse > connected output transformer to feed the grids. > I would have to agree.. Dennis D. W7QHO Glendale, CA
RE: [AMRadio] Matching a 100 watt PA am to drive 833'S
I'll take a very wild stab at it. From the RCA TT-4 handbook, the 833's at 3000VDC require 400V peak G-G volts, that is 242 V RMS. The drive is 20W. That makes the current 82 mA. That makes the impedance 2950 ohms G-G. If you have an old output transformer such as a 6K CT to 0-4-8-16 ohm type, and were to connect the transformer's 16 ohm winding to the 8 ohm winding on the power amp, then the secondary would look like 3000 ohms, close enough. You could also do a chinsel-cheeze method and use a dual-primary power transformer (120V each primary) set up for 240VCT, and with a secondary voltage of 12VAC. Use one with at least 5 amps rating on the 12v winding. Hook the 12VAC winding to the power amp's 8 ohm output. The series'd two 120V windings of the power transformer (240VCT) now looks like 3200 ohms, close enough. You might be surprised how good a power transformer can sound when operated far below its ratings. I think it would be a terrible mistake to mutilate a high quality transmitter by going from a design as superbly engineered as the BC-1F, and converting it to something as jury-rigged as using a power transformer for a driver transformer, or one output transformer feeding a second reverse connected output transformer to feed the grids. Don K4KYV
Re: [AMRadio] CRA Collins AM Net
8 PM EST. We do not change the time when going to or from EDST. Thanks Dave, W3ST Publisher of the Collins Journal Secretary to the Collins Radio Association www.collinsra.com Nets: 3805 Khz, Monday/Wednesdays 8 PM EDST 14250 Khz Saturday, 12 Noon EDST - Original Message - From: "Schichler, Alfred" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Wednesday, January 05, 2005 10:56 AM Subject: RE: [AMRadio] CRA Collins AM Net > I noticed that it says "8 PM EST" (which would be 0100 GMT) in the top part > of the message, but "8 PM EDST" at the bottom (which would be GMT). > Just to clarify things, I was wondering which is correct. > > Thanks, > Al, NE2D > > > -Original Message- > From: David Knepper [mailto:[EMAIL PROTECTED] > Sent: Tuesday, January 04, 2005 8:33 AM > To: Collins Mail List; Discussion of AM Radio > Subject: [AMRadio] CRA Collins AM Net > > > Again, please join the CRA gang with your AM equipment tomorrow evening > (Wednesday) on 3805 Khz at 8 PM EST on AM This is not your ususal "in for > the numbers" kind of thing but an opportunity to try AM on the lower end of > 75 meters where the band is less crowded. You need not be running Collins, > certainly. > > Thank you > > Dave, W3ST > Publisher of the Collins Journal > Secretary to the Collins Radio Association > www.collinsra.com > Nets: 3805 Khz, Monday/Wednesdays 8 PM EDST > 14250 Khz Saturday, 12 Noon EDST > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] CRA Collins AM Net
I noticed that it says "8 PM EST" (which would be 0100 GMT) in the top part of the message, but "8 PM EDST" at the bottom (which would be GMT). Just to clarify things, I was wondering which is correct. Thanks, Al, NE2D -Original Message- From: David Knepper [mailto:[EMAIL PROTECTED] Sent: Tuesday, January 04, 2005 8:33 AM To: Collins Mail List; Discussion of AM Radio Subject: [AMRadio] CRA Collins AM Net Again, please join the CRA gang with your AM equipment tomorrow evening (Wednesday) on 3805 Khz at 8 PM EST on AM This is not your ususal "in for the numbers" kind of thing but an opportunity to try AM on the lower end of 75 meters where the band is less crowded. You need not be running Collins, certainly. Thank you Dave, W3ST Publisher of the Collins Journal Secretary to the Collins Radio Association www.collinsra.com Nets: 3805 Khz, Monday/Wednesdays 8 PM EDST 14250 Khz Saturday, 12 Noon EDST __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
[AMRadio] Matching a 100 watt PA am to drive 833'S
I'll take a very wild stab at it. From the RCA TT-4 handbook, the 833's at 3000VDC require 400V peak G-G volts, that is 242 V RMS. The drive is 20W. That makes the current 82 mA. That makes the impedance 2950 ohms G-G. If you have an old output transformer such as a 6K CT to 0-4-8-16 ohm type, and were to connect the transformer's 16 ohm winding to the 8 ohm winding on the power amp, then the secondary would look like 3000 ohms, close enough. You could also do a chinsel-cheeze method and use a dual-primary power transformer (120V each primary) set up for 240VCT, and with a secondary voltage of 12VAC. Use one with at least 5 amps rating on the 12v winding. Hook the 12VAC winding to the power amp's 8 ohm output. The series'd two 120V windings of the power transformer (240VCT) now looks like 3200 ohms, close enough. You might be surprised how good a power transformer can sound when operated far below its ratings. From: Don Moore R Moore <[EMAIL PROTECTED]> Subject: [AMRadio] Matching a 100 watt PA am to drive 833'S To: amradio@mailman.qth.net Cc: amradio@mailman.qth.net Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=us-ascii I have a older BC 1F series gates transmitter. I would like to do away with the 845 driver tubes and drive the 833's with a 100 watt PA amp. Does anybody have any Ideas what I would need to match the amp to the driver transformer of the 833's. Don Moore W5FFK
RE: [AMRadio] Matching a 100 watt PA am to drive 833'S
Hello Don (s) I have that Gates driver deck with I believe an intact driver. I also have most of the manual possibly for that transmitter. The driver received feedback directly from the finals to help compensate the impedance shifts you mentioned Don. What might be of interest tho a bit over kill is the Gates 5kw audio driver deck that used a quad of EL34's or 6550's to drive the pair of 2500 modulators. Now that has drive! I would guess that the reason for eliminating the 845s is due to their high cost. A pair of equally expensive but more commonly found 211-VT4C triodes would work in place of the 845's to the best of my knowledge. Some of the old PA amps also had a 100 volt output winding that might be adaquate for drive. Not sure the actual Imp.or availability of center tap. Typically a mono bridged solid state stereo amp can approach 100v levels as well with some mfg's claiming 100V line capability in that configuration. If info from or a copy of the 1K manual is needed please E-mail me and I will try to get one made up thats readable. This one was worn out by many engineers use and am not sure if it's complete.I believe the schematic is intact tho taped together. I also have most of the Iron for the 1K tramsmitter with at least one LV powersupply transformer burnt. Not parting with the 10v filament transformers. need them for my 813's. Bill KB3DKS/1
