xpyttl wrote:
Hi Jason

Nice questions, let me try to answer a few ..

wrote in message
ups.com...

1. i've seen transmitter schematics that were simple, and others
that
were complex. as a general rule of thumb, are the more complex ones
trying to compensate for frequency drift, or maybe eliminate higher
harmonics? how efficient and/or stable are the simple transmitter
schematics?

One obvious thing is that CW transmitters tend to be simple, SSB
transmitters complex. But there are a thousand design variables.
One big
one is the complexity of the ICs employed. Today you can have a very
stable
VFO with just a few parts. You tend to pay a little bit of a price
in phase
noise, but frequency drift is not an issue. With an analog VFO, you
can add
a lot of complexity trying to get around frequency drift, but phase
noise is
never an issue. Years ago, all you had was analog. A few years ago,
DDS
(direct digital synthesis) was complex and expensive. Today, analog
VFOs
tend on the expensive side! It is similar with amplifiers. In many
radios,
all, or most, of the PA is in a single brick, instead of a fistfull
of
parts. Ditto with almost everything up and down the chain.

Frequency is also an issue and again that is changing with
technology. A
few years ago, it was hard to get directly to VHF. You typically had
several oscillators getting mixed up, frequency multiplied, etc.
This was
especially true if you had an analog VFO because it is very hard to
get
stability at VHF, and multiplying the frequency also multiplies the
drift in
an analog VFO. There are still reasons you might want to do some
mixing up
to get to VHF with a DDS VFO, but DDS parts up into the gigahertz
range are
now cheap parts.

It was only a few years ago that a DDS VFO cost hundreds of dollars.
Today
you can buy a chip with a VHF synthesizer and amplifier and modulator
for

Good info to know. I was kinda looking around to make a (mostly) IC
transmitter like that... (anything 70cm and under). Are you aware of
any chip PN's or schematics I could dive into to learn?

Thanks,
Dave