[time-nuts] Active antennas for a Thunderbolt...

Tom Knox actast at hotmail.com
Mon Jul 30 18:53:15 UTC 2012


Hi;
Is your coax 50 or 75 ohm? Is it microwave rated? and have you tried changing coax length? None of these should be a major factor but could make a difference.
Best Wishes;
Thomas Knox



> From: shalimr9 at gmail.com
> Date: Mon, 30 Jul 2012 13:46:40 -0500
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] Active antennas for a Thunderbolt...
> 
> Chuck, 
> 
> I have one of the original red box TB.  It came with the Trimble Bullet antenna that is specified in the TB datasheet. 
> 
> The antenna works but gives extremely poor results.  The TB works much better with the Symmetricom antenna that is sometimes available on eBay. 
> 
> The Bullet antenna is usable with other GPS receivers,  so I know it is not bad.  Its just a poor match for the TB. 
> 
> Didier KO4BB
> 
> 
> Chuck Harris <cfharris at erols.com> wrote:
> 
> >Ok, I'm getting a little puzzled.  I have a TB that came from one of
> >the early groups sold by John Ackermann and TVB as part of the TAPR
> >buy.
> >It works nicely, but like all TB's, it is deaf as a post, and needs a
> >high gain antenna.... When I first got the TB, I tried it with a
> >Motorola
> >hockey puck antenna, with about 17db gain, and if it is outside in the
> >clear, it works nicely... but LH shows the satellites signals are all
> >down in the mud.
> >
> >...So...
> >
> >I bought the active antenna that the TB data sheet said belonged with
> >the TB, a 24045-10 bullet antenna, and *NO* satellites are visible..
> >the antenna is dead.
> >
> >I'm no stranger to getting cheated on things I buy, so I chalked it up
> >to bad luck, and put my Motorola hockey puck antenna back on my TB.
> >
> >...Then....
> >
> >A couple of days ago another active antenna became available, a
> >Micro Pulse 1934NW/C 50db antenna from a DATUM INC GPSDO.  I checked
> >its data sheet, and it powers off of +5V @ 38ma, so I bought it,
> >hooked it up to my TB, and again *NO* satellites are visible... the
> >antenna is dead.
> >
> >I put a "T" in the line, and the voltage heading up to the antenna is
> >around +4.5V... The spec sheet says it will work down to +3V.
> >
> >Am I doing something wrong here?  Or am I just unlucky?
> >
> >-Chuck Harris
> >
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> 
> -- 
> Sent from my Motorola Droid Razr phone with K-9 Mail. Please excuse my brevity.
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