NEED HELP! Frequency Synthesizer
 

I am planning to build a 50MHz synthesized VFO. I want to use ICs as
much as possible. I have been looking for VCO chips, the ones I found
were made for 400MHz+ frequencies. Does anybody make synthesizer
components - including VCOs - for below 50Mhz?

Any other help and advice is most welcome!

Of course, the standard answer anymore seems to be the AD985x series of DDS
chips. Far Circuits has a board to build a 0-30 MHz DDS from a 9850, and by
replacing the clock with a 120 MHz part, it will easily get up past 50. I
think the 9854 will play up to 400 but getting a simple, inexpensive clock
could be a push.

High speed prescaler chips are relatively inexpensive. One thought that
occurred to me (but I haven't gotten any farther than collecting the parts)
is to use something like the TR4400/4900 or TRF2050/52 then prescaling down
to something sensible. Typically, you're going into a mixer anyway, so the
square wave the prescaler would leave you with would be an advantage.

I believe Steve Weber was able to make the 4400 play as low as the 50 MHz
region directly - you might poke him one. Although most of these chips are
made for cell phones, I suspect most will work at lower frequencies. It's
usually just a question of doing the math.

...

"Mehrdad Ghassempoory" wrote in message
...
I am planning to build a 50MHz synthesized VFO. I want to use ICs as
much as possible. I have been looking for VCO chips, the ones I found
were made for 400MHz+ frequencies. Does anybody make synthesizer
components - including VCOs - for below 50Mhz?

Any other help and advice is most welcome!

Of course, the standard answer anymore seems to be the AD985x series of DDS
chips. Far Circuits has a board to build a 0-30 MHz DDS from a 9850, and by
replacing the clock with a 120 MHz part, it will easily get up past 50. I
think the 9854 will play up to 400 but getting a simple, inexpensive clock
could be a push.

High speed prescaler chips are relatively inexpensive. One thought that
occurred to me (but I haven't gotten any farther than collecting the parts)
is to use something like the TR4400/4900 or TRF2050/52 then prescaling down
to something sensible. Typically, you're going into a mixer anyway, so the
square wave the prescaler would leave you with would be an advantage.

I believe Steve Weber was able to make the 4400 play as low as the 50 MHz
region directly - you might poke him one. Although most of these chips are
made for cell phones, I suspect most will work at lower frequencies. It's
usually just a question of doing the math.

...

"Mehrdad Ghassempoory" wrote in message
...
I am planning to build a 50MHz synthesized VFO. I want to use ICs as
much as possible. I have been looking for VCO chips, the ones I found
were made for 400MHz+ frequencies. Does anybody make synthesizer
components - including VCOs - for below 50Mhz?

Any other help and advice is most welcome!

That would be the POS-50.

Pete

Leon Heller wrote in message
...

"Mehrdad Ghassempoory" wrote in message
...
I am planning to build a 50MHz synthesized VFO. I want to use ICs as
much as possible. I have been looking for VCO chips, the ones I found
were made for 400MHz+ frequencies. Does anybody make synthesizer
components - including VCOs - for below 50Mhz?

Any other help and advice is most welcome!

MCL might make a VCO that include 50 MHz.

Leon
--
Leon Heller, G1HSM

http://www.geocities.com/leon_heller

That would be the POS-50.

Pete

Leon Heller wrote in message
...

"Mehrdad Ghassempoory" wrote in message
...
I am planning to build a 50MHz synthesized VFO. I want to use ICs as
much as possible. I have been looking for VCO chips, the ones I found
were made for 400MHz+ frequencies. Does anybody make synthesizer
components - including VCOs - for below 50Mhz?

Any other help and advice is most welcome!

MCL might make a VCO that include 50 MHz.

Leon
--
Leon Heller, G1HSM

http://www.geocities.com/leon_heller