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

In message , Reg Edwards
writes
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.



What Reg is describing here is undoubtedly the BEST and EASIEST and MOST
PREDICTABLE way to double the frequency of a signal. You can also use it
to obtain x2 and x6 etc, but with reducing efficiency. I have frequently
used it to get signals up to about 1000MHz.

It s exactly the came circuit as for a bi-phase rectifier on a mains
power supply, ie transformer with centre-tapped secondary and two
diodes.
The shape of the output waveform is the same as what you get from the
rectifier circuit, ie a series of half sinewaves (all +ve or -ve,
depending on which way you connect the diodes). This contains an
infinite series of even harmonics and no odds (including the
fundamental).

For the mathematical, the theoretical level of each harmonic can be
predicted from a knowledge of what Mr Fourier says about this shape of
waveform (from the coefficients associated with each frequency). See
below for several examples (just click on the examples at the bottom of
the page).
http://www.efunda.com/math/fourier_s...ier_series.cfm

In theory, there are no losses. But you are splitting a single signal
into a load of even harmonics, so the level of each must be less than
the original signal.

In practice, there ARE losses (in the diodes and the ferrite). From
memory, the x2 is about 8dB down, x4 is about 16dB down, x6 is about
24dB on the original signal. These ratios are essentially independent of
drive level, provided you have sufficient to overcome the knee of the
diodes. If you are after the x4 and x6, you can actually do things which
reduce the loss somewhat, and make the multiplication more efficient.
But I digress...

Finally, a big advantage of this circuit is that the odd harmonics are
well suppressed. They are not zero, but are typically 30 - 40dB less
than the adjacent evens (depending on the balance of the circuit). This
makes any filtering (if the application requires it) SO much easier.

Cheers,
Ian.

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