Does anyone know if this situation would benefit from doing something
similar to a 'Collins Hard Limiter' i.e. instead of squaring the signal
in one stage, use maybe two or three cascaded stages with increasing
bandwidths? Normally, Collins limiters are used with beat frequencies of
less than 1 KHz, but maybe there's value in doing at typical time-nuts
frequencies.
Any thoughts?
Ed
On 8/20/2013 10:02 PM, Said Jackson wrote:
Hi Ed,
For anything up to about 150MHz try the NC74SZ04 types from National if you can
find them NOS. they stopped making these years ago.. Fairchild is ok too but
not as fast from what I have seen.
Forgot I wrote about it in 2009. Oh boy -age kicking in.
Bye,
Said
Sent From iPhone
On Aug 20, 2013, at 20:17, Ed Palmer <ed_pal...@sasktel.net> wrote:
Hi Said,
Yes, I saw your message from 2009 where you warned about the sine waves. That's
why I was watching for it. Thanks for the warning. I also realized that a DC
Block and a 10 db attenuator makes a very nice TTL or CMOS to Wavecrest converter
for anything except 1 PPS which would need about 15 db. I tried an old circuit
that uses an MC10116 ecl line receiver - it's actually a dead Racal Dana 1992
counter where I'm using the processing on the external reference input to square
up the signal. It gives me a slew rate equivalent to about a 50 MHz sine wave.
It helped a lot, but not enough. I'll try a 74AC04 and a BRS2G Differential Line
Receiver (risetime < 3ns, 400Mbps throughput). Both are in my junkbox.
Ed
On 8/20/2013 8:12 PM, Said Jackson wrote:
Guys,
The dts needs to be driven by square waves, driving them with sine waves gives
jitter values that are displayed significantly too high due to trigger noise.
Holzworth makes a small sine wave to square wave converter that can drive 50
ohms. Use a DC block and an attenuator on the cmos output to avoid damaging the
dts inputs. You can make your own converter using a single fast cmos gate,
resistor, and blocking cap. By using hand-selected gates I was able to achieve
less jitter with that circuit than what the Holzworth box was able to achieve.
Doing that conversion can bring down the measured rms jitter on a very good
10MHz sine wave source from 10ps+ to less than 2ps - basically at or below the
noise floor of the dts.. Once you run at the units' noise floor, you know your
source is quite good..
Bye,
Said
Sent From iPhone
On Aug 20, 2013, at 18:51, Ed Palmer <ed_pal...@sasktel.net> wrote:
Adrian,
I used Timelab to assess the reaction of the DTS-2077 to different sine wave
inputs. The differences in the noise floor are surprising. The attached
picture was made by taking the output of an HP 8647A Synthesized Generator
through a splitter, and then through different lengths of cables to the inputs
of the DTS-2077. The combination of splitter and cable loss meant I couldn't
get +7 dbm @ 1 GHz. If I could have, the 1 GHz line might have been lower than
it was.
Ed
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