I'll extend the webpage (in the next few days) to include more
variations of the circuit as well as the associated LTSpice schematic files.
However at some stage a breadboard is necessary to validate the
simulations, in particular the effect of transformer parasitics.
I have done some simulations that include the effect of imperfect
coupling and transformer capacitances, accurate models for the
transformers would help.
However at 5MHz or 10MHz the likely transformer parasitics won't have
much effect.
Bruce
Ed Palmer wrote:
That would help. Perhaps they should be added to the web page. I'm
sure that I'm not the only one who would be interested.
Ed
Bruce Griffiths wrote:
Ed
If it helps I can send you some LTSpice schematics so that you can
simulate the circuit for yourself.
The breadboards behave as predicted by the simulations at 10MHz.
John Miles has done some preliminary phase noise measurements on his
version.
The transformers are wound on binocular ferrite cores.
I used some 14mm (long) cores intended for 40MHz to 220MHz (I had
some) operation in my breadboard which works well at 5MHz and 10Mhz.
Bruce
Ed Palmer wrote:
Thanks Bruce. This is the kind of info I was looking for. I'll
have to study your schematics. The purpose of much of it isn't
immediately obvious. :-)
Ed
Bruce Griffiths wrote:
Ed Palmer wrote:
I have a late-model 105B Oscillator that's equipped with a
10811-60109 oscillator. It seems a shame to have that nice 10 MHz
source without having access to it. I was thinking of adding a
buffer amp and bringing out the 10 MHz signal. It shouldn't be
too hard, but before I reinvent the wheel, has anyone done this
and do you have any suggestions or advice?
Thanks,
Ed
Ed
Amplifiers like those shown:
http://www.ko4bb.com/~bruce/OCXOBufferAmplifiers.html
<http://www.ko4bb.com/%7Ebruce/OCXOBufferAmplifiers.html>
work well.
The gain is determined by the transformer turns ratio and the
emitter series resistor value is chosen to set the output impedance
to 50 ohms.
RF amplifier transistors other than the 2N3904 can be used, my
breadboard version uses an 2N5943.
Reverse isolation is about 40dB at 10MHz. If you need more
isolation just cascade 2 or 3 such amplifiers.
However some attentiaon to the supply decoupling is required to
ensure that coupling via the supply doesn't degrade the reverse
isolation.
In your case a nominal gain of 3dB or so should suffice.
If you need it +27dBm output is possible with an appropriate RF
transistor.
Bruce
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