OK, staring from a point of experience...
First serious and decent amps in the 100W and up class even if home built will
cost not less that 2-5$/watt.? There are big metal parts and expensive transistors
in many.
Most of the cheap "70W" ebay amps have not been seen as working, for long.?
They are still in need of box, likely a real heatsink (adequately sized), low pass
filters and plenty of spare Mosfets and some do not work at all wall above 20M.?
Caveat emptor.
I have built many of the EB series of amplifiers and they are good stable designs that?
generally perform to the limits of the devices used.? Comments like "CB amps" are
generally meaningless and better avoided.? I have seen those apnotes applied
to CB and some are junk and a few were well done.? Quality is often a builder
thing rather than application.? All of the amp modules require a Low pass filter(s)?
and will be likely switched with relays or mechanically.
One last thing what you put in had better be good as 10x that will reflect
all of the flaws in you signal and more people will hear them and comment.
if that is not clear, garbage in, means garbage out.
The biggest issue for those amps are the transistors for them are scarce and often?
very expensive.? I built them as I already had the devices and last look MRF454s
are over 100$ a pair for real ones.
EB63, basic simple amp, the down side is the diode current alone will be high
and that establishes the bias.? Efficiency when built right is over 50% however
at 160M or over 10M the design is not optimal, that's hard to do over a decade
of frequency range.? However with a good low pass filter and clean input the
result is excellent but the transistors used are costly and it can be intolerent
[unstable] of random substitutions.?
AN762? is a later design that uses a 723 voltage regulator to do a precision bias?
and that is an improvement.??The deal is its excellent and not a simple build
plus the devices are near extinct, unless treasure is expended.? Most will
choke at the cost of the machined copper heat spreader alone.
An779 20W amplifer for a SSB transceiver, excellent amp with good efficiency
and low IMD? output.
AN593 amplifier for 160W (28V use) and a version for 12V that does about 80W
SSB and its a good design but one has to pay attention to the mechanical details
or cooling suffers and for 12V use the power is limited.? Since it has the driver is
part of the design its not suited for more than a fraction of a watt input.? For the
80w (13.8V) version max power in would be around 125mW.? Both versions when
correctly adjusted offer very good IMD.? I've built the 28V version.
Others built include AN791 using MRF247 for 80W at 2m. and the datasheet? MRF492
circuit with bias for 6M and near 100W output.? MRF140 28V 160W amp for 6M,
MRF174 for 2M at 150W, and?a utv8100B amp for 60W (with 5W FT817 drive) at 432.
For VHF and UHF I've built far more but there I do use more power but at HF?
I tend to build to the 4-5W level and rely on either my 100W radio if more is
needed or one of several amps that include the EB63, Wa2EBY,?and a
design that is similar to the EB63 with active bias.
Allison
