EMRFD Message Archive 1973

Message Date From Subject
1973 2008-08-20 02:52:49 Rick High Voltage Transmitters
I agree Geoff. I often design and build solid state transmitters for a voltage well above 13.8.
I've frequently used 24 and 48 volts. Many inexpensive modern transistors will handle the
higher voltage, and linearity and efficiency usually improve. For field use I can add a spare
pack of 8 AA cells in series to get 24 volts for the PA. For home use I sometimes use an
unregulated supply--just a transformer, bridge rectifier, and a really big capacitor.

If you must use one 6v (or 3v) battery, you have a choice between stepping up the battery
voltage or the RF voltage. There are good ways to do both, and it's interesting to experiment
with different options. It sure is easy to build a 5 watt RF amplifier if you have a 24 volt
supply. Vacuum tube designers use higher voltage when they want good performance and
higher output power, and so do audio power amplifier designers.

Best Regards,
Rick kk7b
1977 2008-08-20 15:08:51 Don Hackler Re: High Voltage Transmitters
High power solid state broadcast transmitters use lots of 60 or 80 volts
designs.
It's a compromise between voltage ratings on the LDMOS devices and the
amount of current you have to deal with. Welding cable is often used to
supply power to the amplifier modules.



Rick wrote:
> I agree Geoff. I often design and build solid state transmitters for a voltage well above 13.8.
> I've frequently used 24 and 48 volts. Many inexpensive modern transistors will handle the
> higher voltage, and linearity and efficiency usually improve. For field use I can add a spare
> pack of 8 AA cells in series to get 24 volts for the PA. For home use I sometimes use an
> unregulated supply--just a transformer, bridge rectifier, and a really big capacitor.
>
> If you must use one 6v (or 3v) battery, you have a choice between stepping up the battery
> voltage or the RF voltage. There are good ways to do both, and it's interesting to experiment
> with different options. It sure is easy to build a 5 watt RF amplifier if you have a 24 volt
> supply. Vacuum tube designers use higher voltage when they want good performance and
> higher output power, and so do audio power amplifier designers.
>
> Best Regards,
> Rick kk7b
>
>
>