Analogue frequency synthesis information resources

Hello, I consider these old crystal based analogue synthesizers as a means for frequency synthesis. Two crystal oscillators mixed to produce another frequency.

Are there any resources on the web about this old technique?

Thank you

There is a class of synthesizers called "direct synthesizers" (not to be confused with DDS), that use multiple crystal or saw oscillators, mixed together in various ways with a switch matrix. They used to be very hard to make because the switching matrix was difficult, but they now have "crosspoint" video switches that can do stuff like 2:8 on a cheap chip that make the technology worth revisiting.

This has been useful information I could find a few more links when searching for direct synthesizers, but not practical examples. I know some PACE CBs used this type of synthesis in 70s-80s but no other information

Yep, the classic papers and design concepts just are not on the web anymore! It is a shame.

Here is a paper on a basic very low frequency one:
http://www.google.com/url?sa=t&sourc...q97HpPYDZ6nydQ

yes, that is a good start. Although it uses the harmonics of the fundamental for mixing, but this is the main idea. I have seen an HP direct synthesizer Last News and the pdf here http://www.hpmemory.org/an/pdf/an_96.pdf
The pace 143 schematic is a good practical example for the 27MHz CB band http://www.cbtricks.com/radios/pace/...3_cb143_sm.pdf

No other documents on this though...