[LinuxPPS] Refclock for Rodolpho

[Hal V. Engel]

On Monday 05 January 2009 16:01:28 Remco dB wrote:
> Hal,
>
> Send me one of your UT+'s and the MCX - BNC pigtail (although is not really
> necessary, I have enough teflon coax and female BNC-cable chassis
> connectors). I have a case, RS232-iface (is very simple) and will acquire
> an antenna, and ship it to Rodolfo as a tested (and thus working) setup.
>
> I just made a system for somebody else this way.
>
> Remco

Remco,

I can do that but I am in the process of ordering some more pig tails since I 
need some more anyway.   I used the last one I had on the unit my stepson has.  
Send me shipping info off list - wait I just looked up your call sign so I 
think I have your address assuming the on-line license data is correct, and I 
will package this up and get it out to you as soon as I have the pigtails 
unless you want me to not bother with the pig tail.

For those who might be interested I have been connecting the TTL PPS line 
directly to the serial connector through a 100 ohm resister (IE. no level 
conversion).  This has worked on both computers I have tried it on.   I also 
connect the PPS signal to a hex inverter and run it through two inverter 
stages to an LED so that the LED does not put any load on the GPS PPS line.  
The flashing LED is nice since it makes it easy to tell if the unit is 
functioning.  I also use a USB cable as my "power supply" since the USB power 
spec is an exact match for the 5 volt Oncores other than being able to supply 
more power than needed (IE. 4.75 v to 5.25 v and 500 mA).  Since I can get a 3 
meter USB cable for <$2.00 locally this is a cheap and easy to use power 
supply.  It also uses the same ground as the computer which means that there 
is no possibility of creating a ground loop between the GPS and the computer.

Someone here asked earlier about getting a schematic for the thermostat that 
you built for you computers quartz oscillator.   I think you missed it since 
you did not respond.  I noticed that you now have a posting about this on your 
web site and that this includes a schematic as well as a photo of the 
installed device.  So for the person that asked have a look here 
http://remco.org/ .

I have a few questions about the thermostat.  

1. I see in the photo that the temp sense diodes are basically measuring the 
temperature of the air near the oscillator since they are not in direct 
contact with with the case of the crystal.  It seems that this would reduce 
the effectiveness of the thermostat since the temperature sensor is so loosely 
coupled to the item that you want to control the temperature of.   How much 
impact do you think this has on the performance of the device (IE. how well it 
controls the temperature of the crystal)?

2. The heating transistor seems way too big for this application since it is 
much larger than the device being heated.  Would it be possible to use a 
smaller transistor?

3. Do you have any data on power consumption? 

Hal

>
> On Monday 05 January 2009 23:32:15 Hal V. Engel wrote:
> > As most of you know Rodolpho does not have a reference clock to use for
> > testing.  In November I acquired some additional Oncore UT+ modules (ebay
> > for $15 each plus shipping which totaled about $18 each) and I sent an
> > email to Rodolpho offering to build him a reference clock from one of
> > these units. However I could not supply him with an antenna or serial
> > cable for the unit. With all of the components involved (Oncore, TTL to
> > RS232 converter, wire, ply wood for the box, connectors ...) it costs me
> > about $40 to build one of these not including my labor.
> >
> > He replied that he was interested but did not have an antenna although he
> > did have a serial cable.  Because he did not have an antenna he could not
> > accept the unit at that time.  The unit I was working on for Rodolpho is
> > now connected to my step son's computer and is working nicely.
> >
> > I have more modules and a supply of most of the components and materials
> > needed to build another unit.  And I will be putting together another
> > refclock over the next week or so.  Again if Rodolpho wants this unit it
> > is his but if not it will be a spare unit for me.  However he still needs
> > an antenna to be able to use it.  If anyone here has an antenna that will
> > work that they would like to donate to Rodolpho please let it be known
> > since I would like to get Rodolpho a working reference clock at some
> > point.
> >
> > The Oncore needs an amplified antenna with an MCX connector but I can
> > also put an MCX to BNC pigtail on the refclock's rear panel if that is
> > what someone has.  Actually using the BNC connector would be preferred
> > since this would also create a build in strain relief since the connector
> > would be anchored to the rear panel.   The gain at the receiver connector
> > needs to be between 10db and 33db according to the Oncore manual.  Almost
> > any amplified antenna with the right connector should work even one of
> > those patch antennas if it can be placed near a south facing window or,
> > better still, outside with a clear view of the south sky.
> >
> > Hal
> >
> > _______________________________________________
> > LinuxPPS mailing list
> > LinuxPPS at ml.enneenne.com
> > http://ml.enneenne.com/cgi-bin/mailman/listinfo/linuxpps
> > Wiki: http://wiki.enneenne.com/index.php/LinuxPPS_support
>
> _______________________________________________
> LinuxPPS mailing list
> LinuxPPS at ml.enneenne.com
> http://ml.enneenne.com/cgi-bin/mailman/listinfo/linuxpps
> Wiki: http://wiki.enneenne.com/index.php/LinuxPPS_support