[time-nuts] HP58504A antenna

Adrian rfnuts at arcor.de
Tue Jul 22 07:48:47 EDT 2008

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.


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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