[time-nuts] Diodes to drop antenna volts...

Burt I. Weiner biwa at att.net
Thu Sep 3 14:12:28 UTC 2009

I don't know the particular antenna so I'm going by experience in 
similar situations in offering this this thought:  It seems to me 
that you should be able to put the diodes between the antenna's 
internal equivalent to a bias-T and and the D.C. supply line to the 
pre-amp, out of the RF path.

Burt, K6OQK

At 05:00 AM 9/3/2009, time-nuts-request at febo.com wrote
>From: GandalfG8 at aol.com
>Subject: Re: [time-nuts] GPS Antenna Voltage-Dropping
>To: time-nuts at febo.com
>In a message dated 03/09/2009 02:05:20 GMT Daylight Time,
>Brucekareen at aol.com writes:
>I bought  a 3.6-V Trimble Bullet GPS antenna on ePay and wish to use it
>my  T-bolt.  Rather than try to internally modify the T-bolt to provide  a
>3.6-V antenna feed, I decided to try to build an in-line dropping  adapter.
>I seriesed two Si diodes inside a 100 pf tubular  ceramic capacitor and
>installed  the shrink-wrapped assembly inside a  salvaged BNC-M to BNC-F
>assembly.  Unfortunately the  completed assembly exhibits about a 4-to-1
>VSWR when terminated in a  50 ohm load.  Has anyone else tackled this
>The 3.6-V Trimble antenna has less gain than the 5-V  version which  makes
>my planned antenna rcable run on the edge even  without the high  VSWR..

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net

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