80 Watt Sender - observations

[Yuri D.]

Starting a project to get my 80W.S.a and Umformer U80a working. Interesting observations so far:

• The plug uses 8 pins
• Only 5 of the 8 are used
• Both filament and anode circuits use a common (-). In other devices both filament and anode have their own (-).
• The Umformer supples a massive -300 V control grid bias through one of the pins in the power plug. This is very uncommon for Wehrmacht devices.
• The telegraphy tone is generated by a circuit with a crystal oscillator.

All the tubes in this set are original to this device - they carry date stamps from the same period, and all test in the GUT area of the RPG 4/3 meter. This transceiver probably had not seen any action, since the tubes do not show any signs of being used.

[Yuri D.]

Last night I tested the voltages with my dad. With 800 volts at 375 mA, electrocution is a real danger, therefore basic safety necessitates two people being present when working.

All three voltages showed up properly on the transmitter:

• Filament: +12
• Anode: +800
• Control grid bias: -300

There was a substantial voltage drop for anode and bias voltages due to the voltage dividers and additional resistance in the schematic of the transmitter. Looks like all the wiring and connections are all intact :-)

Next step - put the tubes back and fire it up at 10 Watts. My power supplies do not have horsepower to activate the 80W.S.a at full 80 Watts. The limit of my 1000 volt supply is 200mA, not the 375mA which is required for A3 communication. To test with full power, I will need to use the U80a :-) with two car batteries connected in parallel.

[Yuri D.]

The U80a is an interesting machine. The generator circuit of this Umformer creates +800 Volts on the primary high-voltage windings, and -300 Volts from a secondary set of windings on the high-voltage side of the dynamotor. In this context, it is unique within the Umformer family.

[rv12p2000]

Hello

-300 Volt voltage is probably using to keying this transmitter in cw mode

i think to use grid bias keying ?
the 2xrv12p2000 is using for am and modulate by g1 see fug10

the diagram of the transmitter help understanding of use of this negative voltage
the princip is MOPA master oscillator and power amplifier
you have some technical informations at this url : http://www.radiomuseum.org/r/telefun...r_a_80wsa.html see note

Some informations ans schematic diagram 30 ws : http://www.rkk-museum.ru/vitr_all/exhibits/421.shtml

schematic diagram : http://www.rkk-museum.ru/vitr_all/exhibits/s421.shtml

sorry i don't read the russian (cyrillic)
regards rv12p2000

[Yuri D.]

Hello

-300 Volt voltage is probably using to keying this transmitter in cw mode

i think to use grid bias keying ?
the 2xrv12p2000 is using for am and modulate by g1 see fug10

the diagram of the transmitter help understanding of use of this negative voltage
the princip is MOPA master oscillator and power amplifier
you have some technical informations at this url : http://www.radiomuseum.org/r/telefun...r_a_80wsa.html see note

Some informations ans schematic diagram 30 ws : http://www.rkk-museum.ru/vitr_all/exhibits/421.shtml

schematic diagram : http://www.rkk-museum.ru/vitr_all/exhibits/s421.shtml

sorry i don't read the russian (cyrillic)
regards rv12p2000

-300 Volts were used for a) control grid voltage for the final drivers of the keyed transmitter, b)suppressor grid voltage (injection of modulation into the final drivers), and c) control grid bias when the transmitter is not keyed

This is translated directly from the instruction manual D 978/1

[trfh]

Grid bias -300V - another case

Starting a project to get my 80W.S.a and Umformer U80a working. Interesting observations so far:

• The Umformer supples a massive -300 V control grid bias through one of the pins in the power plug. This is very uncommon for Wehrmacht devices.

Yuri,

you say the -300V is "massive" and "uncommon for Wehrmacht devices".

I was working on a Lorenz Lo40k39 transmitter a while back. It's SGLE/0.2 power unit supplied about 900 volts HT, but this was arranged so that when the key is up, one third of the HT supply is for negative bias (to cut off all the valves), and the other two thirds is on the PA anode. So with the key up we have -300V grid bias, and +600V anode supply (with respect to earth).

When the key is down, the 900V remains, however it is now all across the PA valves, and the grid bias falls to 0 volts - thus producing the expected RF output.

The reason for such a high negative bias voltage is to be absolutely sure of cutting off all the valves when the key is up. This has to work reliably, even when the mains voltage is low, or the valves need extra bias due to variations in their specifications. And there is no problem with a bit more voltage on the bias than you really need provided the capacitors will stand it!

Richard

[Yuri D.]

Yuri,

you say the -300V is "massive" and "uncommon for Wehrmacht devices".

I was working on a Lorenz Lo40k39 transmitter a while back. It's SGLE/0.2 power unit supplied about 900 volts HT, but this was arranged so that when the key is up, one third of the HT supply is for negative bias (to cut off all the valves), and the other two thirds is on the PA anode. So with the key up we have -300V grid bias, and +600V anode supply (with respect to earth).

When the key is down, the 900V remains, however it is now all across the PA valves, and the grid bias falls to 0 volts - thus producing the expected RF output.

The reason for such a high negative bias voltage is to be absolutely sure of cutting off all the valves when the key is up. This has to work reliably, even when the mains voltage is low, or the valves need extra bias due to variations in their specifications. And there is no problem with a bit more voltage on the bias than you really need provided the capacitors will stand it!

Richard

Hello Richard. I have no arguments about your explanation. And probably you would see a bias voltage like this with the larger transmitters. The reason I say this is uncommon, is because out of all the Wehrmacht Panzer transmitters, this is the only one that I've seen which gets the grid bias voltage supplied by the Umformer. Although the -300 Volts is quite high, the delivered current is low (7 mA).

[Yuri D.]

More progress on the transmitter. I hooked up all three voltages to the unit, connected the ground and antenna. To quickly test the configuration, I turned on an Mw.E.c. The first test was made using CW (A1). The tone was received on the Mw.E.c in the "Tg" mode. What was great to see was that the 80W.S.a from 1944 was perfectly calibrated. On all three frequency ranges, the Mw.E.c picked up the CW signal on the exact frequency it was transmitted on - with no drift or deviation. The 80W.S.a was operating for two hours so frequency stability was achieved. Next steps involve taking photos and shooting a video. After this, I'll start testing my U80a Umformer and will run the 80W.S.a from it.

[Yuri D.]

Both the transmitter and Umformer work perfectly:

Here is the video of them working together from a 12 Volt auto battery.

http://www.youtube.com/watch?v=Odz-cVDAHcI

[Dufleuve]

Just great !

[Yuri D.]

Here is a second video of testing it with an Mw.E.c receiving the signal.

http://www.youtube.com/watch?v=RKjCp...lpjPFQG6xnK6IA

[Dufleuve]

Now you have to restore some KFZ like Funksammler to put it in