[AMRadio] Mod xmfr

[Patrick Jankowiak]

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?

[Brian Carling]

Yes I have always been told by G3UUR that an ideal turns ratio is 
around 1.4:1

Now would that typically be with a centre tap on the primary side for 
the P-P mod tubes?

In other words the 1.4 side gets a centre tap?
I am also looking at voltage ratios of suitable ready-made 
old transformers...

Encore un fois, s'il vous plait, Don!

(By the way Don, you had a BODACIOUS signal down into 
central Florida on 160m a couple of weeks back calling CQ 
but I could not raise you with my PW station)

73 - Brian

On 11 Oct 2004 at 17:10, Donald Chester wrote:

> 
> >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 ).
> 
> Regardless of tube or impedances, if you are running a common power supply 
> supplying the same voltage for modulator and final, you need a modulation 
> transformer with a somewhere between 1.3:1  and 1.6:1 turns ratio.  The 
> lower ratio (1.3:1) will give higher positive peak capability and more 
> headroom before flat-topping.  The higher ratio (1.6:1) will allow the 
> modulator tubes to run cooler, but your modulation percentage will be 
> limited to just a little over 100% both positive and negative, leaving 
> little headroom in the positive direction before peak clipping sets in.
> 
> Most modulation transformers with a given turns ratio will match a wide 
> variety of actual impedances.  For example,  a 2:1 impedance ratio (1.4:1 
> turns ratio) could match 8000 ohms plate-to-plate to a 4000 ohm modulating 
> impedance, or the same transformer could be used to match  16000 ohms 
> plate-to-plate to o 8000 modulating impedance.  Modulating impedance is 
> final amp plate voltage divided by final amp plate current.
> 
> Just be sure that the ratings of the transformer (maximum voltage and 
> current) are not exceeded.  Running a given transformer at higher impedances 
> tends to result in some low frequency rolloff, and running it an lower 
> impedances tends to roll off some of the highs, due to inductances and 
> internal capacitances of the windings.
> 
> Optimum turns ratios will vary if the plate voltage on the modulator is 
> different from that of the final.
> With lower modulator plate voltage you need less  step-down in the mod xfmr 
> and vice versa.  Also, if you are interested in extended positive peaks, you 
> will need less stepdown.
> 
> Don k4kyv
> 
> 
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> Help: http://mailman.qth.net/mmfaq.html
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Re: [AMRadio] Mod xmfr

[W7QHO]

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

RE: [AMRadio] Mod xmfr

[Brett gazdzinski]

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
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Re: [AMRadio] Mod xmfr

[Patrick Jankowiak]

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

[Crawfish]

That's it!!!
Joe W4AAB
- Original Message - 
From: Jim Wilhite <[EMAIL PROTECTED]>
To: Discussion of AM Radio 
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" 
> 
> 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 
> > 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
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> > 
> 
> 
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> 

Re: [AMRadio] Mod xmfr

[Jim Wilhite]

Check here:
http://www.amwindow.org/tech/htm/813/813.htm

- Original Message - 
From: "Crawfish" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; "Discussion of AM Radio" 


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 
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>



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Re: [AMRadio] Mod xmfr

[Crawfish]

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 
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?

[Donald Chester]

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 ).


Regardless of tube or impedances, if you are running a common power supply 
supplying the same voltage for modulator and final, you need a modulation 
transformer with a somewhere between 1.3:1  and 1.6:1 turns ratio.  The 
lower ratio (1.3:1) will give higher positive peak capability and more 
headroom before flat-topping.  The higher ratio (1.6:1) will allow the 
modulator tubes to run cooler, but your modulation percentage will be 
limited to just a little over 100% both positive and negative, leaving 
little headroom in the positive direction before peak clipping sets in.


Most modulation transformers with a given turns ratio will match a wide 
variety of actual impedances.  For example,  a 2:1 impedance ratio (1.4:1 
turns ratio) could match 8000 ohms plate-to-plate to a 4000 ohm modulating 
impedance, or the same transformer could be used to match  16000 ohms 
plate-to-plate to o 8000 modulating impedance.  Modulating impedance is 
final amp plate voltage divided by final amp plate current.


Just be sure that the ratings of the transformer (maximum voltage and 
current) are not exceeded.  Running a given transformer at higher impedances 
tends to result in some low frequency rolloff, and running it an lower 
impedances tends to roll off some of the highs, due to inductances and 
internal capacitances of the windings.


Optimum turns ratios will vary if the plate voltage on the modulator is 
different from that of the final.
With lower modulator plate voltage you need less  step-down in the mod xfmr 
and vice versa.  Also, if you are interested in extended positive peaks, you 
will need less stepdown.


Don k4kyv

Re: [AMRadio] Mod xmfr

[Rbethman]

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+
|   |
| 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] Mod xmfr

[StephenTetorka]

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

[AMRadio] Mod xmfr?

[Patrick Jankowiak]

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.

RE: [AMRadio] Mod xmfr?

[John Coleman, ARS WA5BXO]

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
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Post: mailto:AMRadio@mailman.qth.net

RE: [AMRadio] Mod xmfr?

[John Coleman, ARS WA5BXO]

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?

[John Coleman, ARS WA5BXO]

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
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Post: mailto:AMRadio@mailman.qth.net

Re: [AMRadio] Mod xmfr?

[Geoff/W5OMR]

> 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

[AMRadio] Mod xmfr?

[StephenTetorka]

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