[time-nuts] 4046 variations (was EPE GPS....)

[Francesco Ledda]

The only portion of the device with possibly significant variability is the
VCO. If the design does not take care of the VCO variability, for the
capture range of the PLL; things may not work.

If the device had a Phase-Frequency detector, instead of a phase detector,
the capture range would not be a problem. Phase detectors are OK, when an
acquisition aid is available or when the PLL closed loop BW is much larger
than the max phase rate a start up.

I am surprised to hear that such kind of sloppy design was allowed to be
released. When I worked at Rockwell-Collins, such thing would have been a
big No-No!

Regards,

Francesco

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Javier Herrero
Sent: Sunday, September 27, 2009 9:23 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 4046 variations (was EPE GPS....)


Margina design? ;) Better said, very poor design.

Does not sound very good that same part, same lot code, sometimes work
here but not there, sometimes does not work at all... Extending it a
bit... sometimes will work at a given temperature, sometimes will not at
a given other.

Regards,

Javier

Robert Atkinson escribió:
> The old King Radio (then Bendix-King now part of Honeywell) Silver crown
aircraft radios used 4046's in some of the synthesisers. The one in the VHF
com had a different King part number to that in the ADF (MF direction
finder). While trouble shooting we tried an ADF chip in a VHF (didn't have
the VHF part in stock). It sort of worked but was slow to lock-up at the
ends of the frequency range. Ordered some of the correct parts, both ADF and
VHF. They all had the same manufacturer's part number and date code but
different King numbers overstamped. Appaently the selected then at the
factory for low noise (ADF) or wide pull-in (VHF).
>
> Robert G8RPI.
>
> --- On Sun, 27/9/09, Joe McElvenney <ximac at btinternet.com> wrote:
>
>> From: Joe McElvenney <ximac at btinternet.com>
>> Subject: [time-nuts] Egg on Face (was EPE - GPS Frequency Reference
Project)
>> To: "Time Nuts Digest" <time-nuts at febo.com>
>> Date: Sunday, 27 September, 2009, 11:00 AM
>> Hi,
>>
>>> There's a subtle difference between 3rd phase detectors
>> in the 74HC4046A
>>> (Philips/NXP, ON, TI) and the 74HC4046 (Fairchild, NS)
>>> The 3rd Phase detector in the 74HC4046A works as the
>> designer intended
>>> in the GPSDO circuit, the 3rd phase detector in the
>> 74HC4046 does not.
>>
>>> The 74HC4046 uses an RS flipflop for the 3rd phase
>> detector and requires
>>> narrow pulses on the R and S inputs.
>>> The 74HC4046A uses extra internal gates to ensure that
>> only narrow
>>> pulses are seen by the RS flipflop in the 3rd phase
>> detector.
>>
>>> Bruce
>> You are perfectly correct. I hadn't noticed that there was
>> a 74HC4046A
>> fitted to the board in the article but just a plain
>> 74HC4046 shown in
>> the parts list. However, it is something to watch out for
>> as this will
>> be a popular project among those, like myself, who do not
>> need to slice
>> time quite so finely.
>>
>>
>> Cheers - Joe G3LLV
>>
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>
>
>
>
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--
------------------------------------------------------------------------
Javier Herrero                            EMAIL: jherrero at hvsistemas.com
HV Sistemas S.L.                          PHONE:         +34 949 336 806
Los Charcones, 17A                        FAX:           +34 949 336 792
19170 El Casar - Guadalajara - Spain      WEB: http://www.hvsistemas.com


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