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[time-freq] TADD-1 Question

John Ackermann N8UR jra at febo.com
Sat Apr 14 21:05:14 UTC 2007


Hi Matt --

The most important advice first (for the benefit of others who might
read this):  Only build the bandpass filter if you know you need it!
The vast majority of applications don't require it.  The only time it
might be of value is if you have a source that outputs square waves and
have a device (like a receiver) that needs a sinewave input; most test
equipment is quite happy with a non-sine input.

The bandpass filter will result in increased temperature sensitivity,
because any tuned ciruit is a thermometer!  So, don't install it unless
you really have a need for it.

The TADD enclosure is designed as a "universal" box for all the TADD
units.  The TADD-3, which is a digital distribution board designed to
take one PPS signal and provide multiple outputs, has an option to drive
serial ports, so the DB-9 cutouts are for that use.

73,
John
----

Matt Osborn said the following on 04/14/2007 04:55 PM:
> No need to ship the part, John, I have a replacement part here. My
> main concern was to take advantage of the experience of others.
> 
> I discovered the enclosure you've made available today while exploring
> the TAP web site.  I see what appear to be two DB9 holes punched in
> the back panel.  Are there some expansion options available that I
> haven't found yet?
> 
> I don't think I'll need the bandpass filter as my source is an Isotemp
> OCXO 10MHz oscillator disciplined with Brooks Shera's board.  While I
> can build these things, my knowledge level is insufficient to design
> them.  So what do you think of the bandpass filter?
> 
> On Sat, 14 Apr 2007 16:27:31 -0400, John Ackermann N8UR <jra at febo.com>
> wrote:
> 
>> Hi Matt --
>>
>> Sorry about the missing part!  If you'd like, I can send you the 0.33uF
>> tantalum.
>>
>> The data sheet for the 78XX series regulators shows the 0.33 cap on the
>> input, but doesn't specify what type it must be, so I think you're OK
>> using a ceramic or other non-polarized cap.  We ended up using a
>> tantalum cap for the production units because it's what we had in stock. :-)
>>
>> 73,
>> John
>> ----
>>
>> Matt Osborn said the following on 04/14/2007 04:08 PM:
>>> I received my TADD-1 kit this morning and found that capacitor C40
>>> (.33ufd) was missing.  The silkscreen has this as non-polarized, but
>>> the documentation says that it is polarized.
>>>
>>> From the circuit, it doesn't appear to matter what type of capacitor
>>> is used but before I plug something in from my junk box, I thought I'd
>>> better ask why C40 was changed from non-polarized and just what kind
>>> of polarized capacitor would be best.
>>>
>>> Thanks for the help.
>>>
>>> -- kc0ukk at msosborn dot com
>>>
>>> _______________________________________________
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>>>
>>>
>>
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> 
> -- kc0ukk at msosborn dot com
> 
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