Author Topic: Trimble Resolution T thinks antenna port is shorted  (Read 732 times)

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Offline tkamiya

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Trimble Resolution T thinks antenna port is shorted
« on: March 03, 2019, 09:25:29 pm »
This is odd.....

I finally got Trimble Resolution T to work.  Power supply is 3.3V (spec).  My antenna system is shared with rest of the lab and it goes like this.

GPS antenna -> 4 port sharing device -> GPSTM x 2 & Trimble.

One of the GPSTM is supplying power to sharing amp and the GPS antenna (5V)

Trimble is fed via DC isolator.  It has an ability to supply 5V but I don't need it, so I just isolated it DC wise from rest of the system. 

Lady Heather says "Antenna Short".  It can't be...  It has a DC isolator in it.  So I'm thinking it's some kind of mis-detection.  My antenna system won't be changing so I'll need to somehow fool it to think it IS supplying power (3.3V) I think.

Has anyone experienced this?
 

Offline Gyro

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #1 on: March 03, 2019, 09:37:01 pm »
Maybe it's seeing 0V DC on the antenna input and assuming it's shorted, sensing is probably fairly primitive.

Try putting 3V3 on the antenna supply pin (pin 1), that might make it go away.
Chris

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Offline tkamiya

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #2 on: March 03, 2019, 09:59:25 pm »
This is TOO FUNNY. 

I just did that and the message now reads "Antenna OPEN".  With that queue, I removed the DC isolator.  Now it says "Antenna OK". 

It's just overly helpful, I guess.  It would be nice if I can disable this entirely.

But thanks for the idea.  It will get me going.
 

Offline Gyro

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #3 on: March 03, 2019, 10:08:08 pm »
Haha, it's being entirely too helpful.

Maybe tacking a resistor to the PCB just before the antenna supply gets to the input RF isolation inductor?
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Offline tkamiya

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #4 on: March 03, 2019, 10:50:25 pm »
I think the solution might be to put a register across antenna input to simulate typical current drain by active antennas.

Do you know this one?

Everything else seem to be working fine.  But the graph is funny.  There is a definite saw tooth pattern and red line is appearing at the top.  Typically, the red line means GPS has lost lock.  In these cases, I get very difficult to see 1 dot high red line across.  This one is like 10 dot high and looks like upside down freshly cut grass.  Saw tooth is obvious.

If I put my mouse pointer on the red grass and slide, the time stamp changes from red to blue to red and alternates.
 

Offline Gyro

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #5 on: March 03, 2019, 10:55:54 pm »
I looked on a photo and couldn't see the inductor I mentioned, so tacking an smd resistor across the bottom of the SMB connector will probably fine - you sound to have a decent antenna system. 1k would give you 3.5mA which should be about right.

Sorry, I'm afraid I'm not a Lady Heather expert.
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Offline tkamiya

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #6 on: March 03, 2019, 11:23:08 pm »
Someone....

Is this the red tick mark manual talks about?  (indicating incoming data is not every second)??
 

Offline tkamiya

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #7 on: March 03, 2019, 11:46:13 pm »
Yup, time update is happening every 3 seconds....  Tried another unit, same thing.  Tried cold boot, same thing.  hum....

Looking at the output with putty, something is coming out every second, although I cannot read the content (TSIP is a binary format)
Trimble's software does report time update every second.
« Last Edit: March 04, 2019, 01:50:51 am by tkamiya »
 

Offline tkamiya

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #8 on: March 04, 2019, 03:08:16 am »
Updated LadyHeather to latest.  Posted reply to Beta thread. 
 

Offline texaspyro

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #9 on: March 04, 2019, 03:20:00 am »
The original model Res-T has a firmware bug.  If certain message requests are sent, it takes the device 3 seconds to respond.   Try starting Heather with the /rxr or /rxr=1 or /rt=1 command line options.  This will tell Heather that the device is the old model and not to issue requests that can hose up the receiver.
 

Offline dekagon

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #10 on: March 05, 2019, 07:30:50 pm »
Hello texaspyro,

is there a switch on LH which switched off the antenna testing functions of the receiver?
In my case I am using a Trueposition GPSDO after a DC blocking GPS distribution amplifier
which has its own DC source for the bias-t for the gps antenna...

Attached two pics of LH. As you can see, the receiver tracks satelites...
But from start the antenna status shows alarm as shown on the second pic...
The gps status is no gps which comes surely direct from the Trueposition output data...

Thank you in advance

Chris
« Last Edit: March 05, 2019, 08:17:43 pm by dekagon »
---
 

Offline texaspyro

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #11 on: March 06, 2019, 06:06:44 am »
The antenna monitor on most devices  just issues a warning and does not affect the operation of the device.   However, what causes the warning (like a shorted antenna feed) could prevent the device from working.

You might want to try a self-survey (SS keyboard command).  Your device may think it is still in West Bumfuk...  but I think you may also have some antenna issues.
« Last Edit: March 06, 2019, 06:09:16 am by texaspyro »
 

Offline tkamiya

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Re: Trimble Resolution T thinks antenna port is shorted
« Reply #12 on: March 06, 2019, 07:01:34 am »
How you can prevent these error depends on what kind of distribution amplifier (splitters) you are using.  I use Spectracom 4 port device.  It can actively manage these issues most of the time.

I had a splitter with 2 out of 4 port already in use and power was supplied to antenna by both.  With one of my receiver was added to it, it reported a short.  Added a DC block and it changed nothing.  Added power so that this one also supplies power, it reported open.  Removed DC block then errors went away.

Another idea was to put register across the antenna port, so it fakes an antenna consuming power.  I never tried this myself.
 


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