Doubling a reference frequency
 

GM Folks,
My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

The 5Mhz TCXO has an output of 2v P-P sinewave into 50R and I need TTL
level 50:50 M:S at 10Mhz.

Thanks, Mike W

"Mike W" wrote in message
...
GM Folks,
My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

The 5Mhz TCXO has an output of 2v P-P sinewave into 50R and I need TTL
level 50:50 M:S at 10Mhz.

You could use a diode doubler with a tuned 10 MHz amplifier.

73, Leon

Check your counter specs. Some will take 1, 5 or 10 mhz time base
without doing anything.

73
Gary K4FMX

On Fri, 27 Aug 2004 07:32:37 GMT, (Mike W)
wrote:

GM Folks,
My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

The 5Mhz TCXO has an output of 2v P-P sinewave into 50R and I need TTL
level 50:50 M:S at 10Mhz.

Thanks, Mike W

Gary Schafer ) writes:
Check your counter specs. Some will take 1, 5 or 10 mhz time base
without doing anything.

73
Gary K4FMX

That's a good point. Given that they will all divide the timebase down
to a very low frequency, even if there's nothing specific one could likely tap
higher up on the divider chain.

Michael VE2BVW

On Fri, 27 Aug 2004 07:32:37 GMT, (Mike W)
wrote:

GM Folks,
My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

The 5Mhz TCXO has an output of 2v P-P sinewave into 50R and I need TTL
level 50:50 M:S at 10Mhz.

Thanks, Mike W

On Fri, 27 Aug 2004 07:32:37 GMT, (Mike W)
wrote:

GM Folks,
My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

If you are just going to drive the gate of the frequency counter, the
gate is typically 1 s, 100 ms, 10 ms etc. so the 5/10 MHz reference
frequency is divided down a few times anyway, so why do you need the
50:50 mark:space ratio ?

The frequency divider chain will change on either on the leading or
trailing edge of the clock (but not on both), so the gate time will be
1.000000 s regardless of the mark/space ratio, provided that the clock
mark/space ratio remains constant.

Paul OH3LWR

On Fri, 27 Aug 2004 07:32:37 GMT (Mike W)
wrote:

GM Folks,
My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

What is the TCXO and what is wrong with it? It may be simple to just
fix it.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

Feed the 5 MHz to both inputs of a high level DBM. The output will be sum
and difference, kill the DC component with a 0.1 uF coupling cap and you
probably can use the 10 MHz result. If not, a little low pass filter to get
rid of the higher frequency responses will make it useable.

W4ZCB

A few turns on a teeny ferrite ring 1:2 transformer, centre-tapped
secondary, and a couple of diodes will double the frequency without any
power loss.

Thankyou everyone for your responses.

I eventually dived into the counters divider chain and found there was
a div2 just where I needed it, so I'm back to "nearly on frequency".
All I have to do now is verify the accuracy of the 5Mhz TCXO :-)

atb Mike W

On Fri, 27 Aug 2004 07:32:37 GMT, (Mike W) wrote:

GM Folks,
My 10Mhz TCXO that I use for a frequency counter timebase has gone
toes up and I only have a 5Mhz one available to replace it. Can anyone
offer ideas to double the 5 Mhz TCXO keeping the M:S ratio accurate
enough for use with the frequency counter ?.

The 5Mhz TCXO has an output of 2v P-P sinewave into 50R and I need TTL
level 50:50 M:S at 10Mhz.

Like several other posters, I'd be very surprised to see a counter that required
50:50 M/S ratio. Jitter in that would be extremely critical. All counters I've
seen use edge-triggering off the same edge for all timing/gating.