| Title: | Amateur Radio |
| Notice: | Classifieds in #8, please register in #3 |
| Moderator: | CVG::EDRY M |
| Created: | Wed Jun 15 1994 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 504 |
| Total number of notes: | 3678 |
Out here in the UK, we now have an experimental allocation at 73Khz.
Unlike the US LF allocation we are permitted 1W ERP, and thus have
an interest in high power generation at this frequency (because the
antennas are so small and hence inefficient).
Most of the transmitters described so far have been based on hi-fi
audio amplifiers, but it occurs to us that it might be better to use
a switched mode PSU (with external oscillator) as the basis.
These are designed to operate at very high efficiency, and as
long as there was no amplitude component in the signal, there
is no need for linearity. We note that a good output filter is needed,
but I am proposing to use a magnetic loop antenna, and these have a
bandwidth of only a few hertz anyway. So the system would look like
a self-radiating high queue tank circuit!
My question is however - do switched mode PSUs operate at these
sort of frequencies?
Stewart
G3YSX
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 497.1 | power fets in simple class-C should do.. | TEKVAX::KOPEC | Consider a spherical chicken; .. | Fri Mar 21 1997 21:38 | 17 |
power FETs are very confortable at these frequencies.. I'd bet with a
couple of Siliconix "littlefoot" FETS driven by a squarewave you could
crank 15-20W with no trouble.
but, the switchmode PSU controllers are aimed at a very different
animal.. they want to deliver DC, and have all the control circuitry do
do same..
BUT.. if you wanted to do AM, you might well be able to convince a
switchmode controller to do most of the work for you.. by using a
detected version of the output as the feedback.. hmm.. I've been
kicking around building a low-power AM transmitter (for generating a
signal to receive on the antique AM BC sets in the house), and maybe this
would make a nice linear setup...
...tom
| |||||