[time-nuts] Acitve GPS antenna biasing

SAIDJACK at aol.com SAIDJACK at aol.com
Fri Oct 9 03:32:59 UTC 2009

Hi Bruce,
these are very nice indeed.
I used these conical inductors in our 2004 FireFox broad-band  synthesizer 
prototype (working from DC to 1.64GHz), they are quite  amazing.

* you need a microscope and a VERY stable hand to solder them down, and  
cut-off the unused wire. I damaged quite a few before I figured out how to  
solder them. And once soldered, they need to be physically protected because  
they are so extremely fragile
* if I remember correctly they won't sell to everyone due to military  
applications (their main use)
* their current handling capacity is limited
* And they are very expensive.
I ended up designing the FireFox with a series connected bias-t using a  
120nH inductor in series to a 150 Ohm power resistor in series to a 2.2uH/270  
Ohm resistor combination.
That works very well up to over 1.6GHz, and costs pennies  compared to $$.
In a message dated 10/8/2009 19:33:06 Pacific Daylight Time,  
bruce.griffiths at xtra.co.nz writes:

For  broadband use a powdered iron filled conical choke such  as:


May be more useful,  provided it is oriented correctly with respect to
the microstrip  transmission  line.


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