[time-nuts] GPS Antenna Feed Line Decision

Clay Autery cautery at montac.com
Sun Sep 3 13:32:31 EDT 2017

Actually haven't settled on an exact solution yet, Gilles.  The power
supply will likely become part of the observations/experiment that
prompted me to use the external supply in the first place.

- All of the devices WANT to supply the antenna.  2 are nominal 5VDC, 1
supplies nominal 3.3VDC...  so I was going to have to use DC blocking
anyway.  The HP amp provides a load resistor (to fool the devices
hopefully) and DC blocking on all ports.  Thus, I get to choose how I
provide the DC power to the PCTEL antenna.

- I saw in some aviation references where pilots claimed that they
achieved "better performance" by running their antennas at higher
voltages.  (Overclocking the antenna amp?  Who knows.)  But it piqued my
interest, especially since the PCTEL antenna I have will "run" from
below 5VDC through 12 VDC and has an even higher survival voltage.

Thus was born the secondary goal of finding out if there is anything to
these reports.  IF I can control the voltage supplied on a (preferably
constant) variable basis to the antenna, I can construct an experiment
to evaluate IF there are performance increase/degradation and in what
ways....  over a wide range of voltages.  IF it pans out on MY antenna,
I will likely have to expand it to additional antennas.

BUT, in answer to your direct question:  Right now I do not know.  I do
know a FEW things.

1) It certainly will not be a switching PS.
2) While I would love to use a super-expensive "lab-grade" supply, I
would actually like to engineer a solution that I can integrate into the
shack/lab on a permanent basis for use in normal ops and future projects.
3) I'm leaning in the same direction that I am for powering everything
in my house that actually wants DC current....  some combination of
linear power supplies and batteries.
4) A lot of this is simply an excuse to engage in an academic exercise
in order to learn/play.  <smile>

Bottom Line: I'll read/research/design and build until I come up with a
supply that meets my needs.  Just off the top of my head, a linear
supply that charges a battery or batteries that provide the top voltage
or voltages in multiple ranges which are then regulated/filtered to
provide dead flat DC at the desired levels.
I am not an engineer or an expert of any kind.  I'll have to go learn
all this.  <grin>


Clay Autery, KY5G

On 9/3/2017 1:55 AM, Clemgill wrote:
> Hi Clay,
> Intersting subject.
> What design for ultra stable/clean power supply are you using please ?
> Thx,
> Gilles.
>> On Sep 2, 2017, at 22:47, Clay Autery <cautery at montac.com> wrote:
>> PCTEL GPS-TMG-HR-26NCM Antenna. 
>> http://www.neobits.com/pctel_maxrad_gps_tmg_hr_26ncm_high_rejection_gps_p2769137.htm
>> Can't say what the gain tolerances are, but it appears to be a pretty
>> decent quality part.
>> The distribution amp is an HP 58516A GPS L1 Distribution Amp with the
>> external power supply tap which will be fed with an ultras stable/clean
>> adjustable linear power supply.  As I understand it, this is a unity
>> gain amp, so there should be little to no insertion loss or distro losses.
>> The distribution amp will be mounted near the devices such that amp to
>> device jumpers will all be < 1 meter/3.28 feet.  Likely a lot less.  ALL
>> Times N-connectors until reaching a connector TM doesn't make.
>> ______________________
>> Clay Autery, KY5G

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