Hi,
I don't remember anymore. I just picked one somewhere in that range. I
got a inductor SMD set. The main point is that the time-constant of L*R
needs to be low enough not to cause any real harm to 1,57542 GHz, which
makes the value relatively flexible. Sure, I did not consider the stub
of the T-connector, but it seemed to work.
So, 68 nH could very well be it.
Cheers,
Magnus
On 06/21/2017 08:12 PM, David C. Partridge wrote:
Hi Magnus - what sort of inductor value did you use? 68nH or so?
Dave
-----Original Message-----
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus
Danielson
Sent: 17 June 2017 15:12
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] GPS splitter
Hi,
At one time I had to design a DC-load since the GPSDO did not experience enough antenna
current due to a different antenna being used. So, a BNC-T was quickly converted with a
SMD inductor and resistor to add 150 Ohm of more load, and that helped the telecom
operator to get their GPS out of "no GPS antenna" warning and actually accept
the GPS satellites it was already detecting fine.
Cheers,
Magnus
On 06/17/2017 02:40 PM, Bob kb8tq wrote:
Hi
The DC block requirement depends a lot on the design of the GPSDO’s
you are using. With some GPSDO’s a 50 ohm load on the eighth port of a
splitter will do a pretty good job of “antenna detect” signaling. In
the more general case of “I didn’t design this beast” dc blocks and dc shunts
to ground is the best approach.
This fairly quickly gets you headed in the direction of the HP /
Symmetricom splitters.
Bob
On Jun 16, 2017, at 11:54 PM, Clay Autery <caut...@montac.com> wrote:
This brings up some interesting questions:
If sharing an active GPS antenna, do you have to DC block all but one
receiver port to prevent multiple receivers trying to supply current
to the antenna?
On say a 26dB antenna (ignoring line loss, power divider insertion
loss, et al), what is the effective gain to each receiver? (Sorry,
having a senior moment)
Should ALL unused ports have 50 ohm +/- 0j terminators on them? I
assume so... Thus, it would be "better" to always use the divider
with the minimum required ports?
I am assuming since this is a receive only situation, it will follow
approximately the same rules of physics that dealing with satellite
antenna installations.
I would LIKE to share one PC-TEL 26dB GPS antenna mounted at the top
of my 38 foot horiz.loop mast right at the shack entrance, using
LMR-400-DB from antenna to Narda 2-way and thence to my current
hacked Nortel GPSDO and my soon to be complete RPi 2/3 w/ Adafruit
Ultimate GPS Hat NTP Server. On that mast, the antenna would have a
near 360 degree view of the sky completely unobstructed.
(Eventually, I expect both of those units to be replaced with commercial units).
I'm assuming that I DC block whichever unit is capable of providing
the LEAST current at 5VDC... I suspect the Nortel unit can supply
more current than the RPi, but that's not a guarantee... And I guess
I could block/turn off DC delivery on BOTH units and add a voltage
adjustable, current limiting DC injection unit into the line.
Thanks.
73,
______________________
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389
On 6/16/2017 7:26 PM, Tim Lister wrote:
On Fri, Jun 16, 2017 at 4:40 PM, Gregory Beat <w...@icloud.com> wrote:
I have reached the point that I need a 4-port splitter for my GPS antenna
(outdoor 5 volt). Any recommendations of models (HP/Symmertricom/Microsemi) to
acquire OR to avoid??
As we recommended to me when I asked a similar question, the Narda
4372A-4 was a brand I had not heard of before and didn't come up in
'gps splitter' searches. I got one on ebay for $24 plus a bit extra
for DC blocks on the n-1 other ports and it seems to work well and
it was handy to have an SMA-based solution as most of the gps
receivers and the antenna pucks seem to use SMA. This meant I only
needed 1 N to SMA converter cable for an external antenna (which has
yet to be externalized...). I found it smaller in real life than it
looks in a lot of the pictures, about the size of a modern
smartphone but about double or more the thickness (the connectors are on the
ends).
greg
---
Cheers,
Tim
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