Have achieved around 120db with 3 cascaded 2N3904 CB amps.
Something like a BFQ18 broadband transistor with its built in emitter
ballasting may be a better choice.
They work well in a pushpull CB Norton transformer feedback amp to boost
the +7dBm output of an OCXO to +19dBm.
Unfortunately
Hi
I found that I was past the network analyzers 120 db floor with two stages at
10 MHz.
Actually the reactive termination thing is a bit of a maybe yes / maybe no
sort of thing. It seems to help with some setups and not with others. What does
work just about always is to terminate the mixer
Dave
Thank you for your offer. I think I have the documentation solved. Brian,
who helped in the past has offered to help and has some of the previous work
to build on.
As to PIC programming I will ask Juerg to get with you off list.
Bert
In a message dated 11/19/2012 8:47:25 P.M. Eastern
ewkeh...@aol.com wrote:
The D/M is being revisited because of the counter performance. 1 E-13 is
easily attainable but the Czech IREE published a paper and claim 2 E-15.
Do you mean the paper optimization of dual-mixer time-difference
multiplier ?
The ZCD developed in this is a bit of a
Yes Bruce I have the paper. I am not suggesting to copy it verbatim but if
there is a way to reach reasonable priced 1 E-14 members of the list should
pipe in. I am willing to do an other board. the rest of the systems well
on its way. Einally after three years.
Bert Kehren
In a message
Since mixer noise is one of the limiting factors using a mixer with low
flicker noise will help.
NIST found that a custom mixer using diode connected (collector base
short) 2N222As had a significantly lower flicker phase noise than either
the ZRPD1 or the 10534A.
They used off the shelf 1:5
Typical Minicircuits SMT RF amps have a phase noise at best 20dB worse
(@10Hz offset) than the mixer/phase detector.
Their reverse isolation is quite low (40dB)
The principle reason that the Czech DMTD has such low internal noise is
due to the absence of any isolation amplifiers.
They use the
Hi
Those isolation numbers are *highly* dependent on very good matching at all
ports. That's rarely the case unless you have a bunch of pads running around
the system.
Bob
On Nov 20, 2012, at 5:49 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote:
Typical Minicircuits SMT RF amps have a
The details about matching (if any) used in the Czech DMTD would be
informative.
To avoid degrading the performance of the DMTD system below that imposed
by the mixers any isolation amps used will need a flicker phase noise
floor below that of the mixers.
Even an opamp based isolation
Hi
Given that common practice is to mis-match the IF port on the mixers, it's
probably not realistic to depend on exact match for isolation. Simple / cheap
common base buffers likely are a better approach. Lots of isolation and not
much flicker noise.
Bob
On Nov 20, 2012, at 9:01 PM, Bruce
Hi
A few more parts and likely not quite as much isolation. None of that means it
won't do a good job though.
Bob
On Nov 20, 2012, at 11:20 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz
wrote:
The attached circuit is somewhat more efficient and a little quieter.
With a little elaboration
Reverse isolation at 10MHz is around 43dB.
This can be improved significantly by using a Sziklai pair instead of a
single transistor in each amplifier.
However one could also do this in a CB amp.
Since phase detectors require LO and RF input levels of around 10dBm
either deign should
Hi
A pair of common base amps will get you to what ever your layout will permit. A
single common base at 10 MHz should get you to at least 60 db with a little
care. If you run a reasonable transistor you can run levels that will fry a 10
or a 13 dbm mixer. Again, all the discrete circuits work
Allow me to put all this in perspective. Three years ago having just
joined time-nuts I started to be interested in Dual Mixers. Having CS and Rb
my
main interest was and still is low noise signal generators and I have all
the HP equipment for those measurements. Did my first Shera Rb
Hi Bert,
What kind or sort of documentation is needed?
schematics?
PC layout?
software / firmware documentation?
I've been programming PICs intermittently for 10+ years. Some of my
projects use 2 or 4 line LCD displays. I have given other
microcontrollers a short test spin.
I've also done
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