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

jmfranke jmfranke at cox.net
Wed Jan 27 17:58:37 UTC 2010


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" <lists at cq.nu>
Sent: Wednesday, January 27, 2010 12:34 PM
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts at 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-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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>>
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>
>
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