Uwe wrote in message ...
So a 50 resistor serves as my dummy load and a meter connected to
the dummy load indicates around 10 volts RMS. If I did my homework that
would indicate around 2 watt output.

E squared over R, yes, two watts is about right.

All this at B+ of 200v and an anode
current of about 35mA (I am running the transmitter off an adjustable bench
tube power supply at this point).

Seven watts input, two watts output is a bit low. How are you
adjusting the controls?

Does all this compare with the numbers you get with your transmitter??
I will need to build a power supply for the final version and would be
interested to know what you use for B+. In order to get 5 Watts I would have
to crank up the B+ quite a bit.

IIRC that design called for 300 or 350 volts B+, which would work out
to 15 watts or so input. The output network is not optimized for 200
volts B+, and in addition the efficieny is better with more plate
voltage.

Actually I don't care at this point since I am still practicing for my code
exam, so I can't even use the transmitter right now.

What study methods are you using?

How do you monitor your transmitting tone with a device like this.

Several ways:

1) Connect an audio oscillator to the key so that both it and the
transmitter are keyed at the same time. This can be a bit tricky
because the two circuits must not interact.

2) Listen to the transmitted signal on your receiver when
transmitting. This requires that you have a way of reducing the
receiver gain while transmitting, but not completely silencing the
receiver. What sort of receiver do you have to go with the
transmitter?

73 de Jim, N2EY

So a 50 resistor serves as my dummy load and a meter connected to
the dummy load indicates around 10 volts RMS. If I did my homework that
would indicate around 2 watt output.

Uwe, The 10 Vrms that your meter indicates may not be accurate at 3.5 or 7
MHZ. It is probably OK at 60 hz. What you can derive from the 10 Vrms is that
the AC-1 is producing power, just not sure how much.
One thing you might try is a method to remove the frequency dependency of
your measurements. Use a 10:1 voltage divider (10k and a 1.11k). Run this
thru a Germanium or Schottky detector diode and a .01 filter capacitor. You
now have a DC voltage that is proportional to power, and relatively frequency
independent.
To calculate the RMS voltage across the 50 ohm load: Read the DC volts out
of the detector-Vdc. Then Vrms=(Vdc*.707)*10.
Example: You read 2Vdc out of the detector. Vrms=14.14 volts. Power into the
50 ohm load is then: 14.14^2/50=4 Watts. The diode drop in the dector will
introduce some error at QRP levels, hopefully not too much for what you are
trying to do.
73 Gary N4AST

So a 50 resistor serves as my dummy load and a meter connected to
the dummy load indicates around 10 volts RMS. If I did my homework that
would indicate around 2 watt output.

Uwe, The 10 Vrms that your meter indicates may not be accurate at 3.5 or 7
MHZ. It is probably OK at 60 hz. What you can derive from the 10 Vrms is that
the AC-1 is producing power, just not sure how much.
One thing you might try is a method to remove the frequency dependency of
your measurements. Use a 10:1 voltage divider (10k and a 1.11k). Run this
thru a Germanium or Schottky detector diode and a .01 filter capacitor. You
now have a DC voltage that is proportional to power, and relatively frequency
independent.
To calculate the RMS voltage across the 50 ohm load: Read the DC volts out
of the detector-Vdc. Then Vrms=(Vdc*.707)*10.
Example: You read 2Vdc out of the detector. Vrms=14.14 volts. Power into the
50 ohm load is then: 14.14^2/50=4 Watts. The diode drop in the dector will
introduce some error at QRP levels, hopefully not too much for what you are
trying to do.
73 Gary N4AST

Doug, that is much more power than I had hoped to get.
I am unsure about the max. values for the 6v6, therefore I stayed low.

When I increase the plate voltage to 325V my 2. grid runs about 280V and the
plate current increases to about 65 mA. I don't really dare to do that
without knowing the max values on that tube.
I guess I could lower the 2. grid voltage by increasing the value of the
resistor connectd to it.
I don't know if that would lower my plate current to what you get.


And yes I have a few 807's lying around, so eventually I could build
something more powerful, but at this point I need to work on my code,
otherwise all of this is a mute point.

You are right about monitoring the CW, it spills over to my receiver and I
can monitor it there, even if I run the transmitter with a dummy load.

So eventually I guess I could just use an arrangement that on transmitt I
would automatically shorten out my receivers antenna.
Hate to use a computer chip (for example) to do it though, I will have to
look for a lower tech way to accomplish this switching.

regards Uwe


in article , Troglodite at
wrote on 3/12/04 08:36:


I run my 6V6's at about 325 volts on the plate, 250 on the screen. The plate
is
loaded to about 40ma, which is about 13 watts input. You can push it beyond
this, but there's really no point since you have to quadruple your power to
gain one S unit on the receiving end. You'll get about 8 watts out which is
fine. If you want something heftier, you can go to a 6L6, 807 or 6146 tube.
There is a compromise with single tube transmitters though, as the power goes
up they tend to chirp, that is, the frequency slides a bit as they are keyed.
It's not objectionable on the 6V6 transmitters, which is why I favor this
power
level.

I started out in 1954 with a surplus ARC-5 receiver and a simple 6V6
transmitter. With it I gained code proficiency and managed to work 28 states
before my Novice licence expired. (They were only good for a year back then.)

For monitoring, you can just use your receiver with the antenna disconnected,
or you can construct any number of monitor devices which you will find in the
ARRL handbook. You can get more sophisticated but you don't have to. There is
a
special satisfaction in communicating with very simple equipment.

Doug Moore KB9TMY

Doug, that is much more power than I had hoped to get.
I am unsure about the max. values for the 6v6, therefore I stayed low.

When I increase the plate voltage to 325V my 2. grid runs about 280V and the
plate current increases to about 65 mA. I don't really dare to do that
without knowing the max values on that tube.
I guess I could lower the 2. grid voltage by increasing the value of the
resistor connectd to it.
I don't know if that would lower my plate current to what you get.


And yes I have a few 807's lying around, so eventually I could build
something more powerful, but at this point I need to work on my code,
otherwise all of this is a mute point.

You are right about monitoring the CW, it spills over to my receiver and I
can monitor it there, even if I run the transmitter with a dummy load.

So eventually I guess I could just use an arrangement that on transmitt I
would automatically shorten out my receivers antenna.
Hate to use a computer chip (for example) to do it though, I will have to
look for a lower tech way to accomplish this switching.

regards Uwe


in article , Troglodite at
wrote on 3/12/04 08:36:


I run my 6V6's at about 325 volts on the plate, 250 on the screen. The plate
is
loaded to about 40ma, which is about 13 watts input. You can push it beyond
this, but there's really no point since you have to quadruple your power to
gain one S unit on the receiving end. You'll get about 8 watts out which is
fine. If you want something heftier, you can go to a 6L6, 807 or 6146 tube.
There is a compromise with single tube transmitters though, as the power goes
up they tend to chirp, that is, the frequency slides a bit as they are keyed.
It's not objectionable on the 6V6 transmitters, which is why I favor this
power
level.

I started out in 1954 with a surplus ARC-5 receiver and a simple 6V6
transmitter. With it I gained code proficiency and managed to work 28 states
before my Novice licence expired. (They were only good for a year back then.)

For monitoring, you can just use your receiver with the antenna disconnected,
or you can construct any number of monitor devices which you will find in the
ARRL handbook. You can get more sophisticated but you don't have to. There is
a
special satisfaction in communicating with very simple equipment.

Doug Moore KB9TMY

In article , Uwe
writes:

When I increase the plate voltage to 325V my 2. grid runs about 280V and the
plate current increases to about 65 mA. I don't really dare to do that
without knowing the max values on that tube.
I guess I could lower the 2. grid voltage by increasing the value of the
resistor connectd to it.
I don't know if that would lower my plate current to what you get.

Uwe,

How are you tuning up the transmitter? Are you adjusting the plate capacitor
for minimum current?

73 de Jim, N2EY

In article , Uwe
writes:

When I increase the plate voltage to 325V my 2. grid runs about 280V and the
plate current increases to about 65 mA. I don't really dare to do that
without knowing the max values on that tube.
I guess I could lower the 2. grid voltage by increasing the value of the
resistor connectd to it.
I don't know if that would lower my plate current to what you get.

Uwe,

How are you tuning up the transmitter? Are you adjusting the plate capacitor
for minimum current?

73 de Jim, N2EY

in article , N2EY at
PAMNO wrote on 3/13/04 15:42:

In article , Uwe
writes:

When I increase the plate voltage to 325V my 2. grid runs about 280V and the
plate current increases to about 65 mA. I don't really dare to do that
without knowing the max values on that tube.
I guess I could lower the 2. grid voltage by increasing the value of the
resistor connectd to it.
I don't know if that would lower my plate current to what you get.

Uwe,

How are you tuning up the transmitter? Are you adjusting the plate capacitor
for minimum current?

73 de Jim, N2EY

Jim,

Sofar I have connected a scope to the antenna and tuned for max waveform eg.
highest voltage. That is also the setting where my dummy load with bulbs is
brightest.
The original instructions for the AC1 explain how to tune but use
expressions like 'turn the capacitor clockwise' which is useless to me when
I am not using their exact part.

They have an alternative way to tune by inserting a mA meter into the key
lead but I do not get the little dips in current they are describing. For me
it is more of a linear increase in current from the highest capacity setting
(lowest current) to the setting where the cap is all open and the current is
highest.

The way things are the max output occurs more or less at the lowest anode
current of my power supply (about 35mA at 200V B+).

Why do I tune for minimum current??

73 Uwe KB1JOW

in article , N2EY at
PAMNO wrote on 3/13/04 15:42:

In article , Uwe
writes:

When I increase the plate voltage to 325V my 2. grid runs about 280V and the
plate current increases to about 65 mA. I don't really dare to do that
without knowing the max values on that tube.
I guess I could lower the 2. grid voltage by increasing the value of the
resistor connectd to it.
I don't know if that would lower my plate current to what you get.

Uwe,

How are you tuning up the transmitter? Are you adjusting the plate capacitor
for minimum current?

73 de Jim, N2EY

Jim,

Sofar I have connected a scope to the antenna and tuned for max waveform eg.
highest voltage. That is also the setting where my dummy load with bulbs is
brightest.
The original instructions for the AC1 explain how to tune but use
expressions like 'turn the capacitor clockwise' which is useless to me when
I am not using their exact part.

They have an alternative way to tune by inserting a mA meter into the key
lead but I do not get the little dips in current they are describing. For me
it is more of a linear increase in current from the highest capacity setting
(lowest current) to the setting where the cap is all open and the current is
highest.

The way things are the max output occurs more or less at the lowest anode
current of my power supply (about 35mA at 200V B+).

Why do I tune for minimum current??

73 Uwe KB1JOW

"Uwe" wrote in message
...
They have an alternative way to tune by inserting a mA meter into the key
lead but I do not get the little dips in current they are describing. For
me
it is more of a linear increase in current from the highest capacity
setting
(lowest current) to the setting where the cap is all open and the current
is
highest.

It seems as though your Plate Tuning capacitor has too little capacitance to
resonate at the frequency you are using.

The way things are the max output occurs more or less at the lowest anode
current of my power supply (about 35mA at 200V B+).

Why do I tune for minimum current??

The combination of the Plate Tuning capacitor and the inductor in the output
circuit comprise a parallel-resonant tuned circuit, which has its highest
impedance at resonance. Therefore, when the two are resonant, current is at
its lowest point. Tuning for maximum voltage on the antenna is not
guaranteed to get the plate circuit on frequency, at least not the frequency
you want. On many of those older tube transmitters, there was enough range
in the plate tuning capacitor that the circuit could be tuned to the second
harmonic of the desired frequency. Ie, if your desired frequency was 3500
kHz, the circuit could also be tuned to 7000 kHz. Measuring antenna voltage
(which many cheap rigs did, by using a "Relative Output" meter, just an rf
voltmeter connected across the antenna terminal) could lead you to adjust
for the wrong resonance frequency. (In the 1960s the 80-meter Novice subband
was 3.7-3.75 MHz, putting the second harmonic outside of any amateur band
and generating a lot of QSL cards from the FCC for unsuspecting owners of
transmitters like the Knight T-60, which had only a relative output meter.)

If you can find someone who has a "dip meter," you can determine whether
your plate circuit can be tuned to resonance, and, if not, how far off it
is. A dip meter is an oscillator with an exposed coil, and an analog meter
that dips when the oscillator is positioned near a resonant circuit. You
adjust the dip meter knob until its meter dips and read the frequency off
the dial. The dial calibration is not great, but if you have a
general-coverage receiver you can listen for the oscillator signal.

I would also investigate the coupling capacitor from the tube plate to the
ungrounded terminal of the plate tuning capacitor. It may have dried out and
shorted. Carefully measure for dc voltage from the ungrounded terminal of
the plate tuning capacitor to the chassis. There shouldn't be any. If there
is, replace the capacitor. As a rule of thumb, its voltage rating should be
4x the plate voltage, capacitance about 1000-1500 pF.

"PM"