[time-nuts] HP58504A antenna

J. L. Trantham jltran at worldnet.att.net
Tue Jul 22 08:16:51 EDT 2008


I have been reading this thread with interest since I enjoy resurrecting
'dead' instruments.  Two questions though:

1. Since I have been out of the loop for many years, what is an 'MMIC'?

2. The picture suggests some corrosion or oxidation near the coax cable
connection.  Has this been cleaned to eliminate any chance of 'shorting' the
signal to ground?

Thanks,

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Adrian
Sent: Tuesday, July 22, 2008 6:49 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP58504A antenna

Hi José,

before trying to fix the antenna, please check if it's still working.

Connect it through a bias Tee (for feeding 5 V into the antenna cable,
and for decoupling DC from the analyzer) to a spectrum analyzer and use
a signal generator with a short wire inserted into the output jack. Set
both instruments to1575.42 MHz. Put the antenna near the signal
generator (1 meter distance would be fine). You should get enough signal
in the air to see if the antenna is working or not.

If there is no signal, please check the source and drain voltage at the
input FET (left side of your picture), Source is the left terminal,
drain the upper one.
Also check voltages at the output MMIC (6 pin device). Check input
(lower left) and output (upper right) as well as the supply pin (lower
right), plus the actual voltage that is coming in from the output coax
cable, and report back.

Adrian

Jose Manuel schrieb:

> 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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