Re: [AMRadio] RF Amp
I think you and Geoff are right. I have and I might as well put it in a box and fire it up. I do want to be sure I pay attention to the comments about having ample and ten some when it comes to audio reserve. I can always turn it down. I'm not sure the floor of my shack will hold all these BC-610's, 1R2 and a monster amplifier-modulator, but it will sure be fun testing it to see. I guess there is an advantage of living alone, you can bust the floor out and not get into trouble! Man, Brett, I would love to have gotten in on that! Transformers, chokes and BIG capacitors are my worst vice. Thanks guys! Rick Brett gazdzinski wrote: Yes, I agree, go oversize if you can. I was lucky to get loads of great parts 20 years ago when no one wanted the stuff, it was all transistors they wanted. I got a load of UTC commercial grade chokes rated for 7000 volts 700ma ccs for $10.00 each! BC610 transformers were free if you would remove them, etc. Good deals can still be got sometimes, I got a nice Peter Dahl power transformer that gives 3000 volts out at 500ma for $75.00 at a fest. I got some nice oil filled caps a few years ago at Gaithersburg for $5.00 each. The really big parts seem rare though... Brett N2DTS __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
Geoff, Thanks for all the excellent info and ideas. You may very well be on to something. I would certainly want an excess of audio power and it may be that the 250TH tubes would have to work real hard to provide it. Maybe I should consider a single 450TL and push pull 250TH to modulate it. That would lope along at 375 watts carrier and I'd still get to benefit of all those tubes. The 100TH's seem to do a good job modulating a single 250TH in the BC-610's, so maybe stepping the entire selection up a notch would work equally well. Thanks for the ideas and help. Rick/K5IZ ARS W5OMR wrote: There's been a lot of good comments in hee, and having been witness to the 'cookie and ether warmer' rig of Johns when it was in it's hey-day and running the full 1kW DC legal limit input power allowed at that time, all I can say is, that was an 'awesome' rig __ AMRadio mailing list 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
RE: [AMRadio] RF Amp
Yes, I agree, go oversize if you can. I was lucky to get loads of great parts 20 years ago when no one wanted the stuff, it was all transistors they wanted. I got a load of UTC commercial grade chokes rated for 7000 volts 700ma ccs for $10.00 each! BC610 transformers were free if you would remove them, etc. Good deals can still be got sometimes, I got a nice Peter Dahl power transformer that gives 3000 volts out at 500ma for $75.00 at a fest. I got some nice oil filled caps a few years ago at Gaithersburg for $5.00 each. The really big parts seem rare though... Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of ARS W5OMR > Sent: Wednesday, December 06, 2006 8:58 PM > To: Discussion of AM Radio in the Amateur Service > Subject: Re: [AMRadio] RF Amp > > > If you've got the iron, I'd build up a 2kVDC supply, to run at 250mA > > on the final, for 500w DC Input to the final. at those > voltages, you > > don't need nearly as big of value components as you would > if you were > > running 4kV on a pair of 450's in the final. > > Of course, build for reserve ;-) Variac the thing, make the current > handling capability double, and make it 2500v. Got an old BC-610 > plate transformer laying around? > > Double up on the modulator supply for the 450T's. You're going to > need 3 or 4kVDC. > Pay attention to your DC power supply, think about things like > critical inductance, capacitors rated for 1.5x the B+ level and so > forth I''ve just gone through all that here, trying to design a (yet > another) power supply for my rig. > > A Power supply for a Class AB(1) or AB(2) or Class B requires a -lot- > more thought be put into it, than say one for a Class C circuit, that > will -always- have a decent amount of current being drawn through it. > > Got any Swinging Chokes? ;-) > > -- > Operating your AM rig without a scope > is like driving our car at night without headlights.(~K4KYV) > > 73 = Best Regards > -Geoff/W5OMR > __ > AMRadio mailing list > 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 > __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
If you've got the iron, I'd build up a 2kVDC supply, to run at 250mA on the final, for 500w DC Input to the final. at those voltages, you don't need nearly as big of value components as you would if you were running 4kV on a pair of 450's in the final. Of course, build for reserve ;-) Variac the thing, make the current handling capability double, and make it 2500v. Got an old BC-610 plate transformer laying around? Double up on the modulator supply for the 450T's. You're going to need 3 or 4kVDC. Pay attention to your DC power supply, think about things like critical inductance, capacitors rated for 1.5x the B+ level and so forth I''ve just gone through all that here, trying to design a (yet another) power supply for my rig. A Power supply for a Class AB(1) or AB(2) or Class B requires a -lot- more thought be put into it, than say one for a Class C circuit, that will -always- have a decent amount of current being drawn through it. Got any Swinging Chokes? ;-) -- Operating your AM rig without a scope is like driving our car at night without headlights.(~K4KYV) 73 = Best Regards -Geoff/W5OMR __ AMRadio mailing list 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
RE: [AMRadio] Pw Supply
> > Why the big hurry, wait to find a good transformer, > > they are around. > > I have wanted one of these since 1955. I have waited long enough > besides, at my age, time is at a premium. Looking for a transformer since 1955, or a power supply? > > > What ratings are you looking for? > > Good question. Actually, I was going to post a question so I could > answer that one. > > I can't make any sense out of the 813 specs, either in the > Handbook or > the data sheet I got on line. > > As near as I can tell, the "typical" voltage for AM is about > 1300 but I > see the Maul talking about 2000. I see plate current at > about 150 but I > see elsewhere 250. I am sort of confused but think that > 2000v ct at 1/2 > amp would do the job. In plate modulated AM service, the 813's will run nice at 2000 volts on the plates at 400ma for 2 tubes. About 600 to 700 watts of carrier output, 3000 watts pep is easy if you have the audio power to drive them. You can drop the voltage or current and just get less power out. You can match them to the mod iron that way if you don't want maximum power out. The 813 is very rugged, I have run them at 2500 volts and 500 ma for short times, they run 2000 volts and 400 ma all day long without problems, and they don't seem to go bad or wear out, I have had the same pair in for the last 15 years... For the modulator I use a pair of 4x150a/4cx250b tubes, 600 watts of audio out at 2000 volts in AB1, no driving power needed, very clean audio.. > > > Is it supposed to fit on the deck over that big hole? > > Roger. > > > Fair radio used to sell a nice oil filled Collins > > transformer, 2250 volt ct at 650ma, 110 or 220 primary. > > With a variac that would give 0 to 1500 volts. > > I don't see anything like that on their site but I will > check further. Lots of stuff is no longer in the fair radio catalog. But lots of people bought the stuff they used to have, so its floating around. The Collins iron would be on the low side voltage wise, and light on the current, but would work at lower powers. 1200 volts at 600ma, you could run 1200 volts at 300ma on the RF deck, and modulate it with 811A's in zero bias. But you would want a separate voltage output from the power supply, through a swinging choke for the modulator. > > > Its always much better to go with choke input, much better > > voltage regulation, much lower startup surge current. > > > With a cap input, the voltage will increase quite a bit, > > but will sag big time under a load. > > Good info. I read somewhere about needing some sort of step > start and > mine has a time delay relay but it doesn't seem to have > anything to do > with charging caps. It connects to something in the RF deck which I > haven't run down yet. It has a high/low switch which applies > either 110 > or 220 to the primary of the HV trans. Would this be > adequate step start? You can do that I suppose, a time delay relay that switches between 220/110, I just use a resistor, like 5 to 10 ohms, the relay shorts the resistor out. > > > What are you going to run off the supply? > > 8UF is not very good for a modulator, I always go > > around 40UF for energy storage. > > Unfortunately, I want to run the modulator and rf deck from > this supply. > That would be 813's/811's. > > This package I bought was a linear so that could explain the > too low cap? I don't think the supply would be big enough. ssb amps are light duty, even the real big ones are light duty. The peak current could be over 700 ma, constant current will be 400 ma for the RF deck, and the modulator resting current of about 40 ma, and the 811A pulls about 350ma peak. Plus the bleeder resistor, say 100ma, that's 850ma on peaks, 540 ma under no modulation. The transformer, choke, rectifiers have to be able to take that current and duty cycle. Its lots better to have separate supplies for rf and modulator. You can run different voltages, use a swinging choke on the modulator power supply, and parts are easier to get when they are not huge. With the parts you have, I suspect it would run a single 813 with 811A modulators at about 200 watts out. Amplifiers also tend to have low voltage plate tuning caps, but in AM service, the voltage doubles under modulation, and really, on peaks can get to 3 times the plate voltage. You can use a 2000 volt cap on an amp running 2000 volts, but need a 6000 volt one under plate modulation to be safe. Most amplifiers can run 1/4 the power of their ssb rating on AM, and I would guess that is so even if you plate modulate it, its just not good for the power. Brett N2DTS > > > js > > -- > PHOTO OF THE WEEK: http://schmidling.com/pow.htm > Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver > http://schmidling.com > > __ > AMRadio mailing list > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Partner Website: http://www.amfo
Re: [AMRadio] RF Amp
There's been a lot of good comments in hee, and having been witness to the 'cookie and ether warmer' rig of Johns when it was in it's hey-day and running the full 1kW DC legal limit input power allowed at that time, all I can say is, that was an 'awesome' rig. But, pay attention to what John said... the 304's were modulated by (4) 813's in Push-pull parallel. (Count 'em - That's (4)! Otis/K5SWK has -great- audio (when that rig is on) and he's running a pair of 833's in the modulator, modulating a -single- 833 in a link-coupled balanced circuit. in MY rig, I'm running around twice the voltage on my 250TH modulators, as I am on the final. That said, since you have the 250's and the 450's.. were I you, I think I'd run the 450's in the Modulator, and the 250's in the final. The legal limit is 1500w PEP output, period. You could run 1kW output, and change the phase of the audio, where the peaks don't reach up, and hit 1500w PEP, or you could probably run 250w with the 450TH's in the modulator, and hit 1500+WPEP with no problem. That's what I -really- wanted to do here, was to run a pair of 450TL's in the modulator, to modulate the 250TH's. I may still, but it's gonna take some re-configuration of the modulator deck. the sockets are too close to the modulation transformer, to allow the 450's to set in there. If you've got the iron, I'd build up a 2kVDC supply, to run at 250mA on the final, for 500w DC Input to the final. at those voltages, you don't need nearly as big of value components as you would if you were running 4kV on a pair of 450's in the final. Find a B&W Butterfly tuning cap, with nuetralizing caps on the end, for cross nuetrization of the grids to plates, and just resign yourself to the fact that you're probably going to have to parallel another capacitor across that one, to resonate the final on 75m. As John said, it -will- need a lot of Capacitance. 450TH/L's run 7.5v @ 12amps, each. A pair is 25 amps (thereabouts) and a single 4-1000 filament transformer will handle that, just fine. -- Operating your AM rig without a scope is like driving our car at night without headlights.(~K4KYV) 73 = Best Regards -Geoff/W5OMR __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
Well, by the time I get it in the shack I will just about have to do that. There is very little left in the cabinet now and it looks like I may need to take that out to be able to maneuver it around. Every door offers a new challenge! Jim Wilhite wrote: You might tear down the RCA and re-assemble it for drill. Then put it on the air. Jim W5JO __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
You might tear down the RCA and re-assemble it for drill. Then put it on the air. Jim W5JO You're absolutely right, Jim. I guess I just have the "builders blues" and want to put all these parts to good use. You know how it is. It's great to operate any of these wonderful old boatanchors and it's great to convert them from one mode of service to Amateur service. But there is nothing more gratifying than putting your own creation on the air. Rick Jim Wilhite wrote: Rick, your RCA will do that. Its efficient too! Jim W5JO __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
You're absolutely right, Jim. I guess I just have the "builders blues" and want to put all these parts to good use. You know how it is. It's great to operate any of these wonderful old boatanchors and it's great to convert them from one mode of service to Amateur service. But there is nothing more gratifying than putting your own creation on the air. Rick Jim Wilhite wrote: Rick, your RCA will do that. Its efficient too! Jim W5JO __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
Rick, your RCA will do that. Its efficient too! Jim W5JO My aim is to construct an amplifier that can lope along at legal limit. Of course, I also want to see all those beautiful tubes pumping out the power. Thanks again! Rick/K5IZ __ AMRadio mailing list 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
[AMRadio] Re: GB> Speaking of radio history...
>Did they read the Onion on the air (snicker)? Well, The Onion paper used to be produced in the same building as our Wisconsin Public Radio facility... but they moved to New York City at some point. We still get free copies every Wednesday - never miss it. Steve WD8DAS __ AMRadio mailing list 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
RE: [AMRadio] Pw Supply
Good info Jim: Certainly something I never considered. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Candela Sent: Wednesday, December 06, 2006 5:24 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Pw Supply John, I don't have a good explanation except I tried this once at a high power level, and the results worked until we put a clamp on Ammeter to look at the combined primary current. We needed 60 volts CT at 200 amperes with 208 vac primary. The secondary isolation from the primary had to withstand 200,000 volts DC. The core was a large 'C' core, and the whole thing sat in a oil tank. The layered layers of mylar insulation resulted in considerable leakage inductance within the transformer. Before we built the beast we tried two 30 volt @ 100 ampere standard transformers to power up a big electro-magnet. It worked but the primary I was 2X what it should have been. Maybe the Tripplett clamp on ammeter was miss-behaving from the every half cycle current draw, but I also recall blowing circuit breakers, and darkening portions of the building. The boss was concerned to say the least. After building the 60v CT transformer prototype, everything worked fine, and had expected primary current. So was it core saturation from high DC current one way only, a power factor issue, or something else? I really don't know, and since that was 1981, my recall could be put in question. After all , over 50 now, so CRS is a fact of being an OM! ;-) I had to make a 0-200amp DC linear series regulator for that supply. A large water cooled heatsink and 32 TO-3 2N6258's in parallel. What a monster that was! Regards, Jim JKO - Original Message From: John E. Coleman (ARS WA5BXO) <[EMAIL PROTECTED]> To: Discussion of AM Radio in the Amateur Service Sent: Wednesday, December 6, 2006 3:28:44 PM Subject: RE: [AMRadio] Pw Supply Jim: (JKO) That is an interesting statement which I had never thought of before. Using two XFMRs like Jack said, seems at first to be a good theory but as you pointed out each transformer will be looking into a half rectifier circuit so that the duty cycle on each core and primary would be alternately 1/120 of a second. I'm just not sure how that computes to heat. The primary current of one XFMR would high for 1/2 of the cycle and low on the other half and alternating half cycles for the other XFMR if phase wiring was proper. If the primary windings were in parallel then the sum of the primary currents would equate to a proper sine wave and the total current of the two would be more that if there was one due to the losses being double but I wouldn't have thought it to be 2X more. This may seem like a dummy's question but is it the unbalanced magnetic swings and DC current through the secondary that would cause the extra loss? I can see where a full wave bridge circuit for each supply and connecting the two power supplies in series would solve this. Elucidated some more please! John, WA5BXO __ AMRadio mailing list 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 __ AMRadio mailing list 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 __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
Wow! Thanks John, that's some seriously good info. I can see there are several things to be considered to be able to operate the amplifier within the specified range and maintain efficiency and linearity. My aim is to construct an amplifier that can lope along at legal limit. Of course, I also want to see all those beautiful tubes pumping out the power. Thanks again! Rick/K5IZ John Coleman ARS WA5BXO wrote: I ran a pair if 304tls in push pull. I think the bias was around 500 volts and the grid current was around 150ma. I drove it with a pair of 812s in push pull at about 110 watts drive. The plate supply on the 304s was around 1600 volts and the plate current was 600ma. Output power was 790 watts. The modulator was four 813s in standard AB2 PPP configuration with 2700 volts on the plates. The tank coil was shortened up and capacitance added to get the Q up for the low load Z. That was an ether heater __ AMRadio mailing list 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
Re: [AMRadio] Pw Supply
John, I don't have a good explanation except I tried this once at a high power level, and the results worked until we put a clamp on Ammeter to look at the combined primary current. We needed 60 volts CT at 200 amperes with 208 vac primary. The secondary isolation from the primary had to withstand 200,000 volts DC. The core was a large 'C' core, and the whole thing sat in a oil tank. The layered layers of mylar insulation resulted in considerable leakage inductance within the transformer. Before we built the beast we tried two 30 volt @ 100 ampere standard transformers to power up a big electro-magnet. It worked but the primary I was 2X what it should have been. Maybe the Tripplett clamp on ammeter was miss-behaving from the every half cycle current draw, but I also recall blowing circuit breakers, and darkening portions of the building. The boss was concerned to say the least. After building the 60v CT transformer prototype, everything worked fine, and had expected primary current. So was it core saturation from high DC current one way only, a power factor issue, or something else? I really don't know, and since that was 1981, my recall could be put in question. After all , over 50 now, so CRS is a fact of being an OM! ;-) I had to make a 0-200amp DC linear series regulator for that supply. A large water cooled heatsink and 32 TO-3 2N6258's in parallel. What a monster that was! Regards, Jim JKO - Original Message From: John E. Coleman (ARS WA5BXO) <[EMAIL PROTECTED]> To: Discussion of AM Radio in the Amateur Service Sent: Wednesday, December 6, 2006 3:28:44 PM Subject: RE: [AMRadio] Pw Supply Jim: (JKO) That is an interesting statement which I had never thought of before. Using two XFMRs like Jack said, seems at first to be a good theory but as you pointed out each transformer will be looking into a half rectifier circuit so that the duty cycle on each core and primary would be alternately 1/120 of a second. I'm just not sure how that computes to heat. The primary current of one XFMR would high for 1/2 of the cycle and low on the other half and alternating half cycles for the other XFMR if phase wiring was proper. If the primary windings were in parallel then the sum of the primary currents would equate to a proper sine wave and the total current of the two would be more that if there was one due to the losses being double but I wouldn't have thought it to be 2X more. This may seem like a dummy's question but is it the unbalanced magnetic swings and DC current through the secondary that would cause the extra loss? I can see where a full wave bridge circuit for each supply and connecting the two power supplies in series would solve this. Elucidated some more please! John, WA5BXO __ AMRadio mailing list 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 __ AMRadio mailing list 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
RE: [AMRadio] Pw Supply
Jim: (JKO) That is an interesting statement which I had never thought of before. Using two XFMRs like Jack said, seems at first to be a good theory but as you pointed out each transformer will be looking into a half rectifier circuit so that the duty cycle on each core and primary would be alternately 1/120 of a second. I'm just not sure how that computes to heat. The primary current of one XFMR would high for 1/2 of the cycle and low on the other half and alternating half cycles for the other XFMR if phase wiring was proper. If the primary windings were in parallel then the sum of the primary currents would equate to a proper sine wave and the total current of the two would be more that if there was one due to the losses being double but I wouldn't have thought it to be 2X more. This may seem like a dummy's question but is it the unbalanced magnetic swings and DC current through the secondary that would cause the extra loss? I can see where a full wave bridge circuit for each supply and connecting the two power supplies in series would solve this. Elucidated some more please! John, WA5BXO __ AMRadio mailing list 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
Re: [AMRadio] Pw Supply
Jim Candela wrote: No you cannot do this. For full wave center-tap rectification the two windings must be on the same core. So much for that great idea. Thanks, js -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
On 12/6/06, Rick Brashear <[EMAIL PROTECTED]> wrote: I know that's right! I can't ever seem to time things right. When I have a chance to get on most everything is long. That's okay, there are plenty of us out there listening when the band goes long, too. I've yet to work anyone in TX, but I did hear a fellow using an ART-13 in an airplane hangar. That was interesting. If you hear a little peanut whistle down in the soup, it will likely be me. I work Paul, W9PJ from Roscoe IL into the northeast using his Ranger only. Not as long of a haul, but I bet folks will hear you just fine. Light 'em up! ~ Todd, KA1KAQ __ AMRadio mailing list 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
RE: [AMRadio] RF Amp
I ran a pair if 304tls in push pull. I think the bias was around 500 volts and the grid current was around 150ma. I drove it with a pair of 812s in push pull at about 110 watts drive. The plate supply on the 304s was around 1600 volts and the plate current was 600ma. Output power was 790 watts. The modulator was four 813s in standard AB2 PPP configuration with 2700 volts on the plates. The tank coil was shortened up and capacitance added to get the Q up for the low load Z. That was an ether heater but it used a lot of power and it was large. The 450s do require a lot of filament and drive. They can be run at lower voltages but as I did the 304s but you will need to make special coils and have a lot of capacitance to 80 mtrs. Or the efficiency will suffer. Also lower voltages generally require a little more drive. These tubes are high current capable if driven hard. And just as point of reference the efficiency of a class C plate modulated amplifier must remain the same for all plate voltages with in the modulation voltage range or the modulation will not be linear. So if the plate voltage is 2000 the efficiency must be the same from at least 1 to 4000 volts. John Coleman WA5BXO __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
I know that's right! I can't ever seem to time things right. When I have a chance to get on most everything is long. I'll try harder to get in there. If that's the 450TL I usually hear you on I KNOW I'm building one. Man, you sound fantastic. I'm not sure my little old Beastly 610 can compete. My major problem is with my antenna. I only have a Butternut vertical up at this time and it is very narrow on 75 and the ground eats most of my signal. Hopefully, in the next few weeks I can get my HyTower and folded dipole up. If you hear a little peanut whistle down in the soup, it will likely be me. 73, Rick A.R.S. - W5AMI wrote: Hey Rick, Being in Dallas, why do I never hear you on the air? You need to get off that 'puter and put some fire on the wire and get in with us from time to time! You can also get a chance to hear me on a 450TL rig, as that's my primary transmitter. 73 Brian __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
On 12/6/06, Rick Brashear <[EMAIL PROTECTED]> wrote: Hey... good idea! I hope they don't notice the "Day/Night" switch on the BTA-1R2! :-D Hey Rick, Being in Dallas, why do I never hear you on the air? You need to get off that 'puter and put some fire on the wire and get in with us from time to time! You can also get a chance to hear me on a 450TL rig, as that's my primary transmitter. 73 Brian __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
Hey... good idea! I hope they don't notice the "Day/Night" switch on the BTA-1R2! :-D Rick Jim Candela wrote: Rick, The tap switch on the plate transformer primary that boosts the B+ from 3000 volts to 5500 volts needs to be hidden. If inspected, you are nice and legal at low tap. Is Brett an "Official Observer"? ;-) Jim JKO __ AMRadio mailing list 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
[AMRadio] Collins 20 v 2
I need a mod transformer and plate transformer for a Collins 20 V 2 Brad KB7FQR __ AMRadio mailing list 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
Re: [AMRadio] Pw Supply
> MFJ has a 900v one for about $100. Is there any reason why I can not > use two of these and tie one side of the secondaries together > and call > that the center tap and have an 1800v ct transformer/s? > Reply from Jim, JKO: No you cannot do this. For full wave center-tap rectification the two windings must be on the same core. If you try this, it may appear to work, but the combined primary currents will be high by 2X from a single transformer. Those MFJ transformers are intended to work into a full wave voltage doubler circuit where 900 x 1.414 x 2 = 2545 volts unloaded, and about 2 kv loaded. This can work, but the capacitors need to be big, and a soft start circuit is needed. Not a good choice for "Push To Talk" B+. Take those two transformers, and with a full wave bridge on each one, series up the DC outputs. You will get the same unloaded voltage, but with MUCH better regulation. You could also run choke input filtering as well, but the output will drop to about 1600 volts. You are better off with better iron and just one transformer. Regards, Jim JKO __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
Rick, The tap switch on the plate transformer primary that boosts the B+ from 3000 volts to 5500 volts needs to be hidden. If inspected, you are nice and legal at low tap. Is Brett an "Official Observer"? ;-) Jim JKO - Original Message From: Rick Brashear <[EMAIL PROTECTED]> To: Discussion of AM Radio in the Amateur Service Sent: Wednesday, December 6, 2006 8:55:57 AM Subject: Re: [AMRadio] RF Amp Brett, I agree and you're correct on all counts. However, I have the iron just sitting in the shed and the thought of those two 450TL's and two 250TH's glowing through a glass window is more than my "being practical" can overcome. __ AMRadio mailing list 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
Re: [AMRadio] Pw Supply
Brett gazdzinski wrote: I would not buy anything from MFJ! The transformers are Ameritron for whatever that is worth. Why the big hurry, wait to find a good transformer, they are around. I have wanted one of these since 1955. I have waited long enough besides, at my age, time is at a premium. What ratings are you looking for? Good question. Actually, I was going to post a question so I could answer that one. I can't make any sense out of the 813 specs, either in the Handbook or the data sheet I got on line. As near as I can tell, the "typical" voltage for AM is about 1300 but I see the Maul talking about 2000. I see plate current at about 150 but I see elsewhere 250. I am sort of confused but think that 2000v ct at 1/2 amp would do the job. Is it supposed to fit on the deck over that big hole? Roger. Fair radio used to sell a nice oil filled Collins transformer, 2250 volt ct at 650ma, 110 or 220 primary. With a variac that would give 0 to 1500 volts. I don't see anything like that on their site but I will check further. Its always much better to go with choke input, much better voltage regulation, much lower startup surge current. With a cap input, the voltage will increase quite a bit, but will sag big time under a load. Good info. I read somewhere about needing some sort of step start and mine has a time delay relay but it doesn't seem to have anything to do with charging caps. It connects to something in the RF deck which I haven't run down yet. It has a high/low switch which applies either 110 or 220 to the primary of the HV trans. Would this be adequate step start? What are you going to run off the supply? 8UF is not very good for a modulator, I always go around 40UF for energy storage. Unfortunately, I want to run the modulator and rf deck from this supply. That would be 813's/811's. This package I bought was a linear so that could explain the too low cap? js -- PHOTO OF THE WEEK: http://schmidling.com/pow.htm Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com __ AMRadio mailing list 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
Re: [AMRadio] T/R switching
David, do you still have the Dow Key relay? 73, John, K5PGW --- DAVID O'NEILL <[EMAIL PROTECTED]> wrote: > >I HAVE A NICE DOWKEY FOR 4O BUCKS > > > > > > > > > Hi Guys, > > I am looking for a dow key relay or some other > type of coaxial relay to > > be used for T/R switching. If any of you have one > laying around that you > > don't need I would be happy to buy it. Or, maybe > some one has a clever > > homebrew way of t/r switching a boatanchor > receiver and transmitter to > > the same antenna. I think I read somewhere about > using open frame relays > > or something. > > > > Thanks in advance, > > > > Bob K6GGO > > > __ > > AMRadio mailing list > > 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 > > > > > > - > Join ISP.COM today - $8.95 internet , less than 1/2 > the cost of AOL > Try us out, http://www.isp.com/ > > __ > AMRadio mailing list > 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 > Have a burning question? Go to www.Answers.yahoo.com and get answers from real people who know. __ AMRadio mailing list 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
Re: [AMRadio] RF Amp
Brett, I agree and you're correct on all counts. However, I have the iron just sitting in the shed and the thought of those two 450TL's and two 250TH's glowing through a glass window is more than my "being practical" can overcome. I have accumulated many high voltage/current capacitors for both the power supply and the RF stage. Granted, it is a tremendous over kill, but it should be able to loaf along at legal limit. Naturally, I wouldn't want to exceed the legal limit. I'm sure I would stand out like a sore thumb if I were to do that. :-D I also agree that all push pull triode amplifiers are basically the same. I was just hoping to hear from someone who had used that particular configuration and see what their results were. Thanks for the info... Rick/K5IZ Brett gazdzinski wrote: I think the 405 TL's will require a LOT if filament power, that's for sure! I also think they like very high voltages, over 3000, which will make things tend to be huge... If you get it built, we are going to monitor you closely, and if you go over 1501 watts pep, you will be in big trouble Besides the power and voltage, all push pull triode setups are the same. You can take any push pull rf deck and just scale it up Brett N2DTS __ AMRadio mailing list 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
[AMRadio] Transformer Case Outline Pinouts
Hello - I am trying to find a pin connection diagram for the UTC special series S-17 transformer. I have looked at the on-line catalogs and they do not have the pinouts, only the specs. The one document on BAMA does not have the "Special Series" transformers. Thanks, Dave N7RK -- *** Dave N7RK Boatanchors Home Page: http://members.cox.net/n7rk Phoenix, Arizona *DXCC Honor Roll**WAZ#22 - 75 Meter SSB* ex-XE2/N7RK, N7RK/ZB2, VK2ERK, ZM0AJN, WB6NRK, WN6IWX Boatanchor and Antique Radio Collector __ AMRadio mailing list 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
RE: [AMRadio] Pw Supply
I would not buy anything from MFJ! Why the big hurry, wait to find a good transformer, they are around. What ratings are you looking for? Is it supposed to fit on the deck over that big hole? Fair radio used to sell a nice oil filled Collins transformer, 2250 volt ct at 650ma, 110 or 220 primary. With a variac that would give 0 to 1500 volts. Its always much better to go with choke input, much better voltage regulation, much lower startup surge current. With a cap input, the voltage will increase quite a bit, but will sag big time under a load. For small supplies with steady loads, that is ok, but for big supplies with loads that vary its not good. On key up, a cap looks like a dead short till it charges up, a choke looks like a resistance in series with the voltage...a big difference... What are you going to run off the supply? 8UF is not very good for a modulator, I always go around 40UF for energy storage. The old Bill Orr handbooks have loads of great info about power supplies in them. Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jack Schmidling > Sent: Tuesday, December 05, 2006 11:12 PM > To: Discussion of AM Radio in the Amateur Service > Subject: [AMRadio] Pw Supply > > I am not having much luck finding a HV xformer for my power > supply so an > idea occurred to me that I would like to pass around. > > MFJ has a 900v one for about $100. Is there any reason why I can not > use two of these and tie one side of the secondaries together > and call > that the center tap and have an 1800v ct transformer/s? > > I am using 866's so I must have a center tap. > > Second question is: > > Mine has the HV going to the choke and then to two 4 mf 3kv caps in > parallel. Is it not more conventional to put a cap on each > side of the > choke or two chokes for a choke input filter? > > What would I gain or lose by moving one of the caps to the HV side? > > Thanks, > > js > > > -- > PHOTO OF THE WEEK: http://schmidling.com/pow.htm > Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver > http://schmidling.com > > __ > AMRadio mailing list > 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 > __ AMRadio mailing list 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
RE: [AMRadio] RF Amp
I think the 405 TL's will require a LOT if filament power, that's for sure! I also think they like very high voltages, over 3000, which will make things tend to be huge, very large plate tuning caps, KW plug in coils wont do for that power level, loads of spacing, and huge tubes make for a HUGE RF deck! And it's a VERY BAD idea to use parts below the power rating. Tubes like the TL, TH, and 4-125/250/400 series don't like low voltages, the efficiency falls way off. Look at the Globe King 500, a 4-250 at 1800 volts, 540 watts in for 300 watts out. Run that tube at 3000 and you could likely get 600 watts out. You will also need a very large high voltage modulation transformer, but if you get it built, you will likely be heard, even without the antenna hooked up! About 350 to 375 watts of carrier is the legal limit if you modulate 100%, and you can do that with a pair of 811's or 812's... If you get it built, we are going to monitor you closely, and if you go over 1501 watts pep, you will be in big trouble Besides the power and voltage, all push pull triode setups are the same. You can take any push pull rf deck and just scale it up to fit the filament voltage, plate voltage and current, drive power... Brett N2DTS > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Rick Brashear > Sent: Tuesday, December 05, 2006 5:08 PM > To: AMRadio@mailman.qth.net > Subject: [AMRadio] RF Amp > > I am thinking about putting a couple of 450TL's in push pull > for the low > bands only. > > * Has anyone here had experience with that configuration? > * What would you suggest for a driver? > * Do you think a couple of 250TH's would do to modulate it? > > It's just in the thinking stage right now, but I have some pretty big > iron I'd like to make use of and at least one 450TL and one > extra 250TH. > > Thanks for any advice... > Rick/K5IZ > __ > AMRadio mailing list > 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 > __ AMRadio mailing list 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
