[time-nuts] GPS Antenna Voltage-Dropping
warrensjmail-one at yahoo.com
Thu Sep 3 17:45:06 UTC 2009
Ummmmm is right,
One of us is missing something, I wonder which one, I think I know.
He has a good bypass cap across all that, The RF is not going to see the diodes.
Not really a very good idea, we're talking about two silicon diodes in
series with each other and then used as the central conductor of a coax adapter
at nearly 1600MHz.
Aside from the discontinuity caused at the diode junction itself, consider
how fine the wire might be inside that diode and consider the magnitude of
the uncompensated impedance changes caused by this, the high VSWR shouldn't
come as too much of a surprise.
Then consider what two rectifying diode junctions are going to do to your
RF signal regardless of the VSWR.
Burt's suggestion of fitting the diodes inside the antenna stands more
chance of success, assuming they are fitted correctly, but I would still
suggest an external biased T as the most practical answer if one still insists
on using the 3.6v antenna.
With 5v antennas so widely available though there really doesn't seem to be
much good reason for doing this anyway.
In a message dated 03/09/2009 17:04:50 GMT Daylight Time,
warrensjmail-one at yahoo.com writes:
Seems like a good idea, a lot simpler and cleaner than the other
Sounds like a data problem, I'd suspect your VSWR meter or cabling first.
Maybe your VSWR meter does not like diodes especially if it is not running
current thru them.
And if you are running current thru them to approximate the GPS antenna,
whatever you're doing to run the current thru them is making the reading
Did you try just the BNC adapter with just a short inside? And with just
the cap inside? Better cap?
And the finial test does it work OK despite the VSWR reading?
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