From:	Helen Cussen [helen@tridentsensors.com]
Sent:	Thursday, June 06, 2013 4:43 AM
To:	Gene Massion
Subject:	Re: Questions about your deep sea GPS/Iridium antenna
Attachments:	DEEPSEA ANTENNA DATA.pdf; ATT00103.htm; 
QA_I_Bluevsmall.jpg; ATT00106.htm

Dear Gene,

Please find the technical specification for the antenna attached.

To answer your questions:
1) It looks like this antenna has 2 separate antenna feeds.  Does this mean there 
is no switching circuitry and we can basically just connect one feed to our GPS 
receiver and one to our Iridium modem and operate both without worrying about 
any switching circuitry?
Yes, there are two feeds one for the Iridium modem and the other for the GPS receiver.  Note 
we can offer a single element antenna if required.
 

2) Our application is battery powered and I think the 2 antenna feeds without switching circuity 
has less loss than other vendors GPS/Iridium solutions that have only 1 feed.  Is that correct?
In our own battery powered solutions we use the two antenna approach for most applications. 
 We do supply some systems with a single switched antenna but this is usually when the 
customer specifies that the antenna needs to be remote from the electronics so we have to use a 
DGO coax cable and connector.  The dual element antenna allows for the use of an active GPS 
element which improves TTFF thus reducing the time that the GPS receiver needs to be 
powered hence saving power.  

 

3) I assume that we won't be able to receive GPS signals when the Iridium modem is 
transmitting.  Is that correct?
In our systems we tend to switch the GPS off when the Iridium is transmitting but this is mostly 
for power saving reasons.  The GPS can be left on during transmissions but you should take 
care that the GPS receiver is protected from damage caused by the Iridium signals.  It depends 
upon the GPS receiver that you are using as to whether it is susceptible to interference from the 
Iridium transmissions - the UBLOX 5 chips certainly are and these should be protected with 
saw filters! 
 

4) Do you have beam patterns for the antennas?  Are they helical antennas?
Yes they are helical - see the attached for the beam patterns.
 

5) Can you tell me a little more about how the antennas are physically arranged in the housing? 
 Is it 2 separate antennas that are stacked on top of each other or ????
Yes the Iridium element is mounted above the GPS element.
 

6) How much gain does the preamp provide on the GPS antenna?  Can you provide the power 
consumption and voltage specs?
See the attached
 

7) Do you have any experience regarding performance vs. height off the water that would help 
me decide how long a "stem" to mount the antenna on?
The antennas will work well so long as they are clear of the water line.  You may need a spar if 
it is likely that the antenna will experience considerable wash over.  18" is usually sufficient. 
 Are you planning to use the SBD or the circuit switched service?  The SBD is less likely to 
experience problems close to the waterline as the transmissions are short so wash over is less of 
a problem.  For the circuit switched service any wash over will interrupt the transmission.
 

8) Can you provide a quote for price and delivery?

The price is £650 excluding carriage, delivery 4-6 weeks from receipt of order.

Please let me know if you have any more questions.

Kind regards,

Helen