[time-nuts] Monitoring the Rapco 1804M - how antenna changes affect the unit

David J Taylor david-taylor at blueyonder.co.uk
Sun Oct 30 06:25:57 UTC 2011


Folks,

I've made a small Web page describing what happened when I changed the 
puck antenna on a Rapco 1804M for a more sensitive one.  The Rapco 1804M 
expects a big outside antenna.

  http://www.satsignal.eu/ntp/Rapco-1804M-notes.html

Simply, the better signal provided a more consistent lock.  I was slightly 
surprised by this, as I had assumed that any modern puck antenna would 
probably be similar in signal-to-noise to any other low-cost puck antenna, 
and that the SNR (and hence quality) would be fixed by the puck rather 
than the main receiver.  However, it seems that in this case, the built-in 
Trimble SVeeSix module actually needs a fair whack of signal coming in.  I 
expect most of you already knew that!  I have another puck to try when an 
MCX to N-type adapter arrives from China....

It also demonstrated to me why 12 channels would be better than six, as 
the Trimble RX doesn't seem to learn that my best view is south, and it 
keeps looking for satellites in the "wrong" part of the sky.  It doesn't 
seem to recognise that when there is one channel's satellite with no 
signal, it could use that one channel to go and look for other satellites. 
12 channels would give it a higher chance of 5 good signals.

I've included a download of the programs I have developed to capture and 
analyse the data.

Cheers,
David
-- 
SatSignal software - quality software written to your requirements
Web:  http://www.satsignal.eu
Email:  david-taylor at blueyonder.co.uk 




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