[AMRadio] Mod xmfr
I have no information on the 813's distortion when used that way. Have you found any curves showing the effect of screen voltage on plate current? The linearity of those would tell something. Alot of external things affect distortion, the modulation xfmr is real important. Patrick From: Brett gazdzinski [EMAIL PROTECTED] Subject: RE: [AMRadio] Mod xmfr One thing I don't like about doing different things with tubes is there is no real info on running 813's triode connected. What's the distortion values? I have a Gonset G76 that uses zero bias and drives the screen grid of a pair of 6dq6 tubes as modulators. I don't think its real clean. Brett N2DTS
Re: [AMRadio] Mod xmfr
Ahh yes. The class-B 813 modulator. Glad to see it! I'd like to comment about it from an audio standpoint as I have done this for audio with 807's. I don't know how tough the 813 control grids are. I would suggest using some resistors to limit the current to the modulators' control grids to about 15 mA average (suggested based on the class C conditions in the tube manual; 20K worked for for 807's but the drive voltage was much less). It is really the screen grids that must be driven to get the plate current up. The peak screen voltage may also be as much as 750 volts (1500 g-g) for the 813 (the same value as the G2 DCV would be if it were operating AB1). An old audio output transformer from a tube amplifier makes a good driver transformer because it will stand the voltage well. The author might have some suggestions too. Patrick From: Jim Wilhite [EMAIL PROTECTED] Subject: Re: [AMRadio] Mod xmfr Check here: http://www.amwindow.org/tech/htm/813/813.htm
RE: [AMRadio] Mod xmfr
One thing I don't like about doing different things with tubes is there is no real info on running 813's triode connected. What's the distortion values? I have a Gonset G76 that uses zero bias and drives the screen grid of a pair of 6dq6 tubes as modulators. I don't think its real clean. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Patrick Jankowiak Sent: Tuesday, October 12, 2004 6:31 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] Mod xmfr Ahh yes. The class-B 813 modulator. Glad to see it! I'd like to comment about it from an audio standpoint as I have done this for audio with 807's. I don't know how tough the 813 control grids are. I would suggest using some resistors to limit the current to the modulators' control grids to about 15 mA average (suggested based on the class C conditions in the tube manual; 20K worked for for 807's but the drive voltage was much less). It is really the screen grids that must be driven to get the plate current up. The peak screen voltage may also be as much as 750 volts (1500 g-g) for the 813 (the same value as the G2 DCV would be if it were operating AB1). An old audio output transformer from a tube amplifier makes a good driver transformer because it will stand the voltage well. The author might have some suggestions too. Patrick From: Jim Wilhite [EMAIL PROTECTED] Subject: Re: [AMRadio] Mod xmfr Check here: http://www.amwindow.org/tech/htm/813/813.htm __ 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] Mod xmfr
In a message dated 10/12/04 6:02:49 PM, [EMAIL PROTECTED] writes: One thing I don't like about doing different things with tubes is there is no real info on running 813's triode connected. What's the distortion values? See ER #57, Jan. 1994 for a set of curves and other info. on the 813 triode connected. Dennis D. W7QHO Glendale, CA
[AMRadio] Mod xmfr
Hey guys: Thanks for all this education on the plate modulator for my 2 x 813's. Seems to me that: 1. current carrying capability of the wire is first; 2. turns ratio ( creating impedance ) comes next; Just how difficult would it be to make one? Our predecessors did. E/I core or over/under on one core? I understand Hypersil cores are easy to get. Might have a challenge counting high numbers...hi hi 73 Steve WA2TAK
Re: [AMRadio] Mod xmfr
Steve, There was a series in ER (Electric Radio), by W3BYM, Tom Marcellino. He built an AM 2-813s modulating 2-813s. It is a beautiful looking and sounding rig. Very much in the class of T-368s or BC-610s. Perhaps even better! If interested, I'll hunt through the collection and get the specific editions for you. Bob - N0DGN [EMAIL PROTECTED] wrote: Hey guys: Thanks for all this education on the plate modulator for my 2 x 813's. Seems to me that: 1. current carrying capability of the wire is first; 2. turns ratio ( creating impedance ) comes next; Just how difficult would it be to make one? Our predecessors did. E/I core or over/under on one core? I understand Hypersil cores are easy to get. Might have a challenge counting high numbers...hi hi 73 Steve WA2TAK Bob Bethman - N0DGN +---+--+ | N0DGN AMRadio Manassas, VA|REAL Tube Radio and AM| +---+--+ | Manassas Radio - Home of Homemade Kielbasa Pirogi| +---+--+ | Bob Bethman\\\|/// The absence of a danger | | rbethman(at)comcast.net \\ ~ ~ // signal does *NOT* mean | | (/ @ @ /) that everything is OK | +-oOOo-(_)-oOOo+ | http://home.comcast.net/~rbethman| | 1 BC-610I w/BC-614I,1 T-213/GRC-26 w/BC614I 1 '51 Collins R-390A | | 1 '67 EAC R-390A, Heathkit DX-60, Apache, Mohawk, SX-101, HT-32A | +--+ | Amateur Astronomer - Celestron Nexstar 8 | | 12 f5 Dob coming soon! Being built | | Meade ETX-60 (Got it back!) | | 38 Deg 46.8' N - 77 Deg 28.5' W| +--+ | Opinions expressed are that of my own and do not necessarily | | coincide with or represent those of ANYONE else | +--+ ALL E-mail received and sent scanned by AVG Norton Anti-Virus
Re: [AMRadio] Mod xmfr
I have info I got somewhere off the web about K1JJ's pair of 813's modulated by a pair of 813's. Joe W4AAB - Original Message - From: Rbethman [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Monday, October 11, 2004 12:07 PM Subject: Re: [AMRadio] Mod xmfr Steve, There was a series in ER (Electric Radio), by W3BYM, Tom Marcellino. He built an AM 2-813s modulating 2-813s. It is a beautiful looking and sounding rig. Very much in the class of T-368s or BC-610s. Perhaps even better! If interested, I'll hunt through the collection and get the specific editions for you. Bob - N0DGN [EMAIL PROTECTED] wrote: Hey guys: Thanks for all this education on the plate modulator for my 2 x 813's. Seems to me that: 1. current carrying capability of the wire is first; 2. turns ratio ( creating impedance ) comes next; Just how difficult would it be to make one? Our predecessors did. E/I core or over/under on one core? I understand Hypersil cores are easy to get. Might have a challenge counting high numbers...hi hi 73 Steve WA2TAK Bob Bethman - N0DGN +---+--+ | N0DGN AMRadio Manassas, VA|REAL Tube Radio and AM| +---+--+ | Manassas Radio - Home of Homemade Kielbasa Pirogi| +---+--+ | Bob Bethman\\\|/// The absence of a danger | | rbethman(at)comcast.net \\ ~ ~ // signal does *NOT* mean | | (/ @ @ /) that everything is OK | +-oOOo-(_)-oOOo+ | http://home.comcast.net/~rbethman| | 1 BC-610I w/BC-614I,1 T-213/GRC-26 w/BC614I 1 '51 Collins R-390A | | 1 '67 EAC R-390A, Heathkit DX-60, Apache, Mohawk, SX-101, HT-32A | +--+ | Amateur Astronomer - Celestron Nexstar 8 | | 12 f5 Dob coming soon! Being built | | Meade ETX-60 (Got it back!) | | 38 Deg 46.8' N - 77 Deg 28.5' W| +--+ | Opinions expressed are that of my own and do not necessarily | | coincide with or represent those of ANYONE else | +--+ ALL E-mail received and sent scanned by AVG Norton Anti-Virus __ 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] Mod xmfr
That's it!!! Joe W4AAB - Original Message - From: Jim Wilhite [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Monday, October 11, 2004 7:53 PM Subject: Re: [AMRadio] Mod xmfr Check here: http://www.amwindow.org/tech/htm/813/813.htm - Original Message - From: Crawfish [EMAIL PROTECTED] To: [EMAIL PROTECTED]; Discussion of AM Radio amradio@mailman.qth.net Sent: Monday, October 11, 2004 7:38 PM Subject: Re: [AMRadio] Mod xmfr I have info I got somewhere off the web about K1JJ's pair of 813's modulated by a pair of 813's. Joe W4AAB - Original Message - From: Rbethman [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Monday, October 11, 2004 12:07 PM Subject: Re: [AMRadio] Mod xmfr Steve, There was a series in ER (Electric Radio), by W3BYM, Tom Marcellino. He built an AM 2-813s modulating 2-813s. It is a beautiful looking and sounding rig. Very much in the class of T-368s or BC-610s. Perhaps even better! If interested, I'll hunt through the collection and get the specific editions for you. Bob - N0DGN [EMAIL PROTECTED] wrote: Hey guys: Thanks for all this education on the plate modulator for my 2 x 813's. Seems to me that: 1. current carrying capability of the wire is first; 2. turns ratio ( creating impedance ) comes next; Just how difficult would it be to make one? Our predecessors did. E/I core or over/under on one core? I understand Hypersil cores are easy to get. Might have a challenge counting high numbers...hi hi 73 Steve WA2TAK Bob Bethman - N0DGN +---+--+ | N0DGN AMRadio Manassas, VA|REAL Tube Radio and AM | +---+--+ | Manassas Radio - Home of Homemade Kielbasa Pirogi | +---+--+ | Bob Bethman\\\|/// The absence of a danger | | rbethman(at)comcast.net \\ ~ ~ // signal does *NOT* mean | | (/ @ @ /) that everything is OK | +-oOOo-(_)-oOOo+ | http://home.comcast.net/~rbethman | | 1 BC-610I w/BC-614I,1 T-213/GRC-26 w/BC614I 1 '51 Collins R-390A | | 1 '67 EAC R-390A, Heathkit DX-60, Apache, Mohawk, SX-101, HT-32A | +--+ | Amateur Astronomer - Celestron Nexstar 8 | | 12 f5 Dob coming soon! Being built | | Meade ETX-60 (Got it back!) | | 38 Deg 46.8' N - 77 Deg 28.5' W | +--+ | Opinions expressed are that of my own and do not necessarily | | coincide with or represent those of ANYONE else | +--+ ALL E-mail received and sent scanned by AVG Norton Anti-Virus __ 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 __ 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] Mod xmfr?
Hi all: I need to better understand the workings of a plate modulator for AM. Considering the RF amp with 2 x 813's and the modulator with 2 x 813's - what are the equations and math to work out the required wattage, impedance, step ratio etc. And, just how much can one depart from the ideal arrangement and with what effects? ( should I not be able to find the right xmfr for this amp I'm planning to build ). PS: I am seeking that modulator xmfr at this time. Tnx, Steve WA2TAK
Re: [AMRadio] Mod xmfr?
Hi all: I need to better understand the workings of a plate modulator for AM. Considering the RF amp with 2 x 813's and the modulator with 2 x 813's - what are the equations and math to work out the required wattage, impedance, step ratio etc. And, just how much can one depart from the ideal arrangement and with what effects? ( should I not be able to find the right xmfr for this amp I'm planning to build ). PS: I am seeking that modulator xmfr at this time. I would refer you to a website with all the links necessary to figure it all out.. http://www.qsl.net/wa5bxo/amtech.html I'm privileged, and honored to be able to call John/WA5BXO my friend. 73 = Best Regards, -Geoff/W5OMR
RE: [AMRadio] Mod xmfr?
Actually Steve, the idea is pretty simple. When using a class C final amplifier the output RF voltage is directly proportional to the plate to cathode voltage. Most of the time the cathode is grounded so we just say plate voltage or plate modulation. This means that if the plate voltage is doubled then the RF output voltage will also double. It's sort of like saying that if we raise the voltage to a lamp it will put out more light, etc. Power or Wattage is generally measured or expressed in average values unless otherwise stated. The is the difference from a horse pulling continuously on a wagon there by exerting a max of one horsepower, verses jerking periodically on it. A lamp will put out the same amount of light will 110 volts DC as it would with 110 volts AC from the wall power. The wall power is measured in RMS (root mean square) value. The peak voltage of the AC wave is ((sqrt of 2) * 110 volts) or (about 1.414 * 110). The RMS voltage value of the wave is (sqrt of .5 * peak) or ( about .707 * peak). To modulate a class C rig to 100% (pos and neg) requires the peak voltage to be equal that of the DC supply so the average audio power required is half the DC power to the plate. For more on this see http://www.qsl.net/wa5bxo/asyam/aam3.html . I'm glad to see questions of this nature. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, October 10, 2004 7:12 AM To: amradio@mailman.qth.net Subject: [AMRadio] Mod xmfr? Hi all: I need to better understand the workings of a plate modulator for AM. Considering the RF amp with 2 x 813's and the modulator with 2 x 813's - what are the equations and math to work out the required wattage, impedance, step ratio etc. And, just how much can one depart from the ideal arrangement and with what effects? ( should I not be able to find the right xmfr for this amp I'm planning to build ). PS: I am seeking that modulator xmfr at this time. Tnx, Steve WA2TAK __ 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] Mod xmfr?
Corrections to the last email: Actually Steve, the idea is pretty simple. When using a class C final amplifier the output RF voltage is directly proportional to the plate to cathode voltage. Most of the time the cathode is grounded so we just say plate voltage or plate modulation. This means that if the plate voltage is doubled then the RF output voltage will also double. It's not perfectly linier but that can be compensated for is circuitry design. It's sort of like saying that if we raise the voltage to a lamp it will put out more light, etc. Power or Wattage is generally measured or expressed in average values unless otherwise stated. This is the difference from a horse pulling continuously on a wagon there by exerting a max of one horsepower, verses jerking periodically on it. A lamp will put out the same amount of light with 110 volts DC as it would with 110 volts AC from the wall power. The wall power is measured in RMS (root mean square) value. The peak voltage of the AC wave is ((sqrt of 2) * 110 volts) or (about 1.414 * 110). The RMS voltage value of the wave is (sqrt of .5 * peak) or ( about .707 * peak). To modulate a class C rig to 100% (pos and neg) requires the peak voltage to be equal that of the DC supply so the average audio power required is half the DC power to the plate. For more on this see http://www.qsl.net/wa5bxo/asyam/aam3.html . I'm glad to see questions of this nature. John, WA5BXO
RE: [AMRadio] Mod xmfr?
The load that is represented by the final is Ep/Ip = load impedance in ohms. The tube manuals gives the proper plate to plate load impedance for a given voltage and class of operation for your modulators. The impedance ratio for your XFMR would be the (PTP impedance) : (final EP/Ip) Turns ratio would be sqrt of impedance ratio. Example - only examples not necessarily real values for 813s Push pull modulators need plate to plate load of 10 K ohms Final amplifier is 1500 volts and .300 ams = 5000 ohms Z ratio = 2 : 1 Turns ratio = sqrt of 2 = 1.414 : 1 Where the modulator side has 1.414 times as many turns as the final side. This can be tested by putting 10 volts AC in final the side and measuring 14.14 volts on modulator side. Some times it is easy to compensate for ratio differences by raising or lowering the voltage on the final while maintaining the same power input. For example suppose you could not find an exact transformer of Z = 2 : 1 But you found one that was 1.5 : 1 This means the final would need to have a higher voltage and less current. 10 K ohms / 1.5 = 6667 ohms Consider raising the plate to 1700 and lowering the current to .255 amps This would get the impedance up to where it is a match for the XFMR/modulator yet still run about the same power. The turns or voltage ratio would be sqrt of 1.5 = 1.22 Good questions Steve John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, October 10, 2004 7:12 AM To: amradio@mailman.qth.net Subject: [AMRadio] Mod xmfr? Hi all: I need to better understand the workings of a plate modulator for AM. Considering the RF amp with 2 x 813's and the modulator with 2 x 813's - what are the equations and math to work out the required wattage, impedance, step ratio etc. And, just how much can one depart from the ideal arrangement and with what effects? ( should I not be able to find the right xmfr for this amp I'm planning to build ). PS: I am seeking that modulator xmfr at this time. Tnx, Steve WA2TAK __ 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] Mod xmfr?
For a close idea of the 813s' needs as far as using them for AM goes, have a look at the transmitting tube manual such as the RCA TT-4. Pick a set of data that gets you close to the RF output you desire. ++ For the PA, 1600VDC at 150mA per tube (300mA) provides 360 watts of carrier from 480 watts input. For the modulator operating AB1 at 1500VDC, a 9300 ohm P-P load is called for in order to get 260 watts output. The rule of thumb is that the modulator should be able to provide an amount of power equal to or greater than half the DC input to the RF PA stage. This rule if accurate for sinewave modulation and a condition of proper impedance matching. So, the modulator, operating at either 1500VDC, or 1600VDC just like the PA, would have more than enough power for the rule. (RF PA 480 watts DC input /2 = 240 watts, and the modulator makes 260 watts) Just barely!! and you might lose a bit in the modulation transformer, but it will still be OK for the sinewave operation. Voice is not a sinewave, so it is useful to either make use of speech processing, or make the modulator able to put out twice or more of what the rule of thumb gives, if you can get away with it. That is another topic, and does not really reflect upon the impedance choices. ++ Next, what is the secondary impedance of the modulation transformer? It is the E/I of the RF PA stage, so that it is in the example 1600/0.3 = 5333 ohms. The modulation transformer could have an impedance ration of: 9300 to 5333 = 1.74 to 1 The turns ratio (voltage ratio) is the square root of that: SQRT 1.74 = 1.32 to 1 ++ 813's can put out more power operated class AB2. 813's as a modulator might be better somehow triode connected (G1 through 20K to G2 and drive G2) and operated closer to class B. I don't have any data for that but I would like to see it discused if anyone has done it.
