The noise figure hit may be nowhere as bad as 5dB because it depends on the
noise figure and gain of the antenna preamplifier, not just the noise
figure.
John WA4WDL
--------------------------------------------------
From: "Bob Camp" <li...@cq.nu>
Sent: Wednesday, January 27, 2010 12:34 PM
To: "'Discussion of precise time and frequency measurement'"
<time-nuts@febo.com>
Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information
Hi
I'm sitting here looking at the spec sheet for the splitter:
A normal four way splitter should have a loss of a bit over 6 db.
The reason that's bad is that it may degrade the noise figure at your
otherwise perfect receiver (and sub 1 db noise figure antenna) by 6 db.
(it
may also do absolutely nothing bad at all)
The splitter has a rated noise figure of 7 db max / 5 db typical.
It has a gain that may be a loss of 3 db or a gain of 3 db.
Worst case, it's got a -3db gain and a 7 db noise figure. It may degrade
the
noise figure at the receiver by 10 db. Best case it's got 3 db of gain and
a
5 db noise figure. That's still a noise figure hit of 5 db.
All of that is pretty easy to blow holes in as far as a real / normally
operating system is concerned. I *think* it's pretty close in the limit
case
though.
If it is close, then the part (yes I bought one to) might improve things
by
1 db. It also might degrade things by 4 db under the worst case conditions
where it likely matters.
Am I missing something here? Obviously it does more than split. It may
have
better isolation than a conventional splitter. It also has the cute little
DC loads in it.
Seems like a little bit more RF gain might have been a good idea.
Bob
-----Original Message-----
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of b...@lysator.liu.se
Sent: Wednesday, January 27, 2010 9:41 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information
Hi,
Another option is to remove the DC-block cap on port 1. Then let your
primary GPS power the splitter and upstream antenna.
http://www.to-way.com/tf/hp58516a.pdf
--
Björn
Hi
I found a SMC-BNC adapter of the correct orientation in the bottom of my
junk box. Somehow I doubt I'll ever use it for anything else. BNC cables
and jacks are something I can find easily.
The top of the unit is held on with screws so getting inside it should
not
be very hard. You could swap the SMC out to something that's more common
for power distribution. Maybe an APC-7 ...
My guess is they used the SMC because it's unusual. That way you don't
get
a cable with 30 VDC on it hooked where it shouldn't go. If you did run a
30 volt supply the dc could do some damage. Of course 30 volts on that
unit connected to a "normal" antenna would do some damage as well.
Bob
On Jan 27, 2010, at 1:14 AM, saidj...@aol.com wrote:
I recommend un-screwing that SMC since it is almost impossible to find
the
mate, and feeding two wires from a 5V supply into the unit through the
hole, and soldering the wires to the PCB. Works well for me.
bye,
Said
In a message dated 1/26/2010 18:36:18 Pacific Standard Time,
bruce.griffi...@xtra.co.nz writes:
I'm using an HP 58516A GPS distribution amplifier to share my GPS
antenna between my receivers.
What is the proper part number or connector "name" for the power
supply connector ?
Thanks for your help !
Claude
According to the datasheet option 05 uses an SMC connector for the
power.
Bruce
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