[time-nuts] homebrew counter new board test result

[Li Ang]

Hi Magnus,
    The C channel is the SMA on the back of the PCB. The input of 74LVC2G14
is set to 0.5vcc with 1k resistor and AC coupled with 100nF.
    Today I compared the performance 74LVC2G04, 74LVC2G17, 74LVC2G14.
http://www.qsl.net/b/bi7lnq//freqcntv4.1/test/20150224/  .
    I saw people talking about using 74AC to square the signal, what's the
difference between 74LVC and 74AC? 74AC is not easy to get.

Thanks

Li Ang

2015-02-24 5:36 GMT+08:00 Magnus Danielson <magnus at rubidium.dyndns.org>:

> Dear Li Ang,
>
> Nice to have you back reporting on your progress!
>
> Now, you have some pretty impressive performance going on there. Looks
> like a nice little unit too.
>
> Is the C-channel the SMA on the back of the PCB?
>
> How did you wire up the 74LVC2G14?
>
> While it is tempting to use both channels in it, don't if you want to keep
> cross-talk between channels low.
>
> Cheers,
> Magnus
>
>
> On 02/23/2015 02:10 PM, Li Ang wrote:
>
>> Hi,
>>     I'm back. I have been testing my new borad for days.
>>     Compared to previous version, this board makes the PCB track of
>> signals far from each other and replaces LDO for TDC with LP5907.
>>     CH_A: simple resistor bias and ac couple "front end", CH_B:
>> CH_A+MC100LVELT22 LVPECL , CH_C: CH_A+74LVC2G14 .
>>     At first, the result is worse than previous board. Using CH_B as the
>> REF and DUT source, the stdev of the phase measurement is about 160ps. The
>> old board can reach about 70ps. CH_A and CH_C are way much better than
>> CH_B. That bothers me for days.
>>     Today, I use the 74LVC2G14 to square the signal from MV89A, and do
>> the same test. For all three channel, the stdevs are about 37ps. The spec
>> of TDC_GP22 is 35ps. And now the performance looks a little bit better than
>> the previous board.  It looks like that the jitter of MC100LVELT22 is much
>> bigger at slow slew rate.
>>     It seems that next step is to play with the front end.
>>
>>
>> The raw data is uploaded to http://www.qsl.net/b/bi7lnq/
>> freqcntv4.1/test/20150222/
>> The pic of this version is uploaded to http://www.qsl.net/b/bi7lnq/
>> freqcntv4.1/pic/ ‍
>>
>>
>>
>>
>> Regards
>> Li Ang
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>  _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>