[time-nuts] HP 58516A GPS distribution amplifier information

[Bob Camp]

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-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of bg at 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, SAIDJACK at 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.griffiths at 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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