[time-nuts] HP58504A antenna

Mike Feher mfeher at eozinc.com
Mon Jul 21 13:54:10 EDT 2008

Jose -

If it is similar to the HP two way GPS power splitter, then the MMIC is a
voltage regulator used to deliver 3 volts to the amplifier transistor. In my
splitter the MMIC died, so, not having another, I cut it out and soldered in
a wire from the 5 volt input to the 3 volt output and then the splitter
worked fine again. The 30 ma may be OK, as the antenna has to let the
receiver know that it is OK, and it does that by exceeding a current
threshold on the 5 volts delivered by the receiver. I doubt if the
transistor draws nearly as much. Check the output lead on the active device
to see if you have 3 volts on it. From your picture it appears it is the tab
that goes to the output filter. 73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jose Manuel
Sent: Monday, July 21, 2008 1:34 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] HP58504A antenna

Hello all,

I´d like to repair a HP58504A antenna that don´t deliver any output signal.
The current is about 30 mA ( I think too high), and the transistor (unknown
type) and the MMIC (uPC2749TB), seems to be with correct voltage.

Does anyone have any experience or data about this antenna?

I took an inside photo: http://www.ea1px.es/HP58504A.jpg     Can the
transistor be identified by the color code?

Thanks in advance, José, EA1PX
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