[time-nuts] Component level 1:2 splitter

[Ulrich Bangert]

Randy,

a splitter for two GPS receivers is a bit different from a normal power
splitter in that both receivers should "see" 50 Ohms impedance @ RF but
abt. some hundred Ohms @ dc. That is because each receiver will try to
measure the (active) antenna's dc current to find out whether the
attached antenna is working or not. They will react to either a to low
or a too high dc impedance with an "short circuit" or an "open loop"
condition that may inhibit them from work. 

If you supply your mail address I can send you a photograph of a diy
passive splitter for two GPS receivers that works pretty well despite
the fact that it looks not really like rf equipment. It is easy to make
from parts out of the junk box. 

Best regards
Ulrich Bangert, DF6JB 

> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von randy warner
> Gesendet: Montag, 10. Marz 2008 22:03
> An: 'Discussion of precise time and frequency measurement'
> Betreff: [time-nuts] Component level 1:2 splitter
> 
> 
> Guys,
> 
> I need to come up with a 0db little splitter to route 1 
> antenna into 2 GPS receivers. To keep the isolation up I want 
> to use an active splitter instead of a passive one. I suppose 
> I could use a passive splitter followed by two LNA's (one to 
> each receiver), but I would then have to add a lot of 
> attenuation to knock the signal back down. I suppose it would 
> work, but the noise factor sure wouldn't be optimum.
> 
> Does anyone out there know of a single/dual IC solution to 
> this? Everything I have found LNA wise is in the 10-30 dB 
> range. Note that this will be a board mounted circuit and I 
> don't have to worry about connectors, etc. I'm hoping to find 
> a little solution that I can cover with one of Laird's 
> standard shield cans.
> 
> Thanks,
> 
> Randy Warner
> 
> 
> 
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