[time-nuts] 58517A external SMC power versus PORT1 power (was Re: HP Z3801A on eBay -- And check this out as)

John Ackermann N8UR jra at febo.com
Mon Feb 26 13:45:29 UTC 2007


I started working on my 58517A splitter yesterday.  After looking at the 
board, I don't think installing a simple 0-ohm shunt to the GPS port is 
the right way to enable "thru" power.  If you do that, port 1 will go 
directly to a bunch of bypass capacitors, and I doubt you'll see any 
signal there.  What probably needs to be installed is an RF choke of 
some sort.  That'll let the DC through without shunting the signal to 
ground.

Rather than doing that, I removed the SMC connector (just unsolder the 
center pin from the board and it unscrews easily) and ran a couple of 
wires in through the hole.  I put a 78L05 regulator on a little piece of 
perfboard and ran its output to where the SMC connector used to attach.

Now, I have a DC input that I can safely feed with 13.8 volts, and I 
don't have the risk of losing signal to 8 receivers because the one on 
port 1 died (or had its power pulled).

John
----

Christopher Hoover wrote:
>> Well, I failed to have my Z3801A drive my 58517A over port 1.
>> Appling 5V on the SMC connector on the 58517A solved the 
>> problem. The same Z3801A was feeding the active antenna with
>> no problem just a few minutes before, so it is not an issue on
>> the Z3801A.
> 
> I've got/had both varieties, and some time ago I mapped out the circuits.
> 
> To be clear (for non-smart spliiters):
> 
> If it has the SMC jack, external DC power must be supplied via the SMC jack.
> All of the output ports will sink some current to make receivers happy, but
> they will not power the amplifier.
> 
> If it doesn't have the SMC jack, power must be supplied via PORT 1.  All of
> the other ports will sink current to make receivers happy, but they will not
> power the amplifier.
> 
> It is easy to convert the external DC version to work with DC on PORT 1.  It
> just takes a (1206, IIRC) shunt -- the pads are right there near PORT1.  It
> is a good idea at the same time to pull the current limiting resistor in
> series with SMC jack so as to disable that input.
> 
> -ch
> 
> 
> 
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