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GlobalSat BT308 Bluetooth GPS Receiver

03rd July 2003

 Review by Mike Barrett



Emtac were the first with a Bluetooth GPS receiver and now they are starting to come in thick and fast. The latest one is the BT308 from GlobalSat. This has a retail price of £292.57 including VAT but street prices may well be cheaper.


The GlobalSat BT308 Bluetooth GPS receiverWhen Darren at PocketGPS saw it he described it as an Emtac on steroids. Well I have been using it for over a month and have got to know it quite well. Does it live up to Darren's description? Read on to find out.


GlobalSat are multinational wireless and GPS specialist manufacturer, based in Taiwan with a presence in USA, Europe and China. Having been in business since 2000 they are now an established manufacturer of GPS equipment.


GlobalSat provided the BT308 Bluetooth GPS receiver for the review, which also used an iPAQ 5450, and iPAQ 3870 and a Toshiba Tecra8000 with a TDK Bluetooth Dongle.




The GlobalSat BT308 Bluetooth GPS receiverWhat do you get?
The GlobalSat comes with just about everything you will ever need. The retail package which I reviewed had the following:

  • BT308 Bluetooth GPS receiver
  • Car Charger
  • International AC power charger
  • External Antenna
  • CD with Manual and software

Having experienced the different configurations with the Emtac/Socket packages I confirmed with the UK distributors that the reviewed package is indeed what end users will receive.



Manufacturers Technical Specifications

Channels 12 parallel channels
Output Messages NMEA 0183 V2.2 protocol and supports command:
Hot Start 8 sec., average
Warm Start 38 sec., average
Cold Start 45 sec., average
Acceleration Limit < 4g
Altitude Limit 18,000m
Re-acquisition 100ms
Velocity Limit 515 meters/sec
Time Accuracy 1us synchronized to GPS time
Position Accuracy 15m 2D RMS without SA {BR} 10m 2D RMS WAAS enabled
Supply Voltage Build-in rechargeable battery and 5V
DC input charging circuit
Operation Time 8hr. After fully charged, in continuous mode
Dimension 84mm*47mm*27mm
Storage Temperature -30¢XC~85¢XC
Operation Temperature -20¢XC~70¢XC
Humidity Up to 95% non-Condensing


What does it look like

Darren described this as an Emtac on steroids, and that is really what it looks like. I would compare it to a souped up car the GTI version with fat tyres (or tires if you are in the States) and flared wheel arches. It looks menacing!!


Well in reality it is almost identical in size to the Emtac except that it is a bit deeper, this additional depth caters for the extra size of the battery.


The side by side comparison shows the indicator lights at the bottom of the unit but you can see that the foot print is about the same. It is not until you see the profile that the size difference becomes apparent. The BT308 GPS receiver is almost a third higher than the Emtac. In fact it looks like it is on a raised platform, this is where the larger battery is located.

Due to the larger battery it also weighs a little more than the Emtac. Interestingly the weight is not something that the manufacturers publish. Using my (extremely inaccurate kitchen scales) I found the BT308 to be 100g where the Emtac was 60g. Still a comfortable weight to carry in a pocket or bag.


The controls and indicators for the GPS receiver are all clustered down at one end. The reason for this will become apparent soon.




The picture to the right shows the controls and indicators of the receiver. Starting on the left there is the power switch, followed by the dc input connector. This uses the same voltage and connector as your iPAQ so the same AC adapter can be used to charge both devices.


I have a DC splitter adapter supplied by PC mobile which allows me to charge both GPS and iPAQ at the same time from the same charger.


On the top of the BT308 are the indicator lights first is the Bluetooth, followed by the Satellite fix, followed by the low battery warning.


This GPS receiver has a slow blue flashing light when no connected and a faster flash when connected. The Satellite Fix indicator is solid green when not fixed and flashing green when fixed. The battery indicator is red when the charge is low and orange when charging, all other times it is off. These indicators can be difficult to see in strong sunlight.

The GlobalSat Bluetooth GPS receiver antenna

The external antenna socket is positioned about two thirds of the way down the receiver on the right hand side. This is a push socket which allows the supplied external aerial to be connected.


The actual internal antenna is located underneath the top section between GlobalSat and the Bluetooth GPS writing. If you move your mouse over the image to the right you will see the antenna superimposed on the receiver.


That just about does it for the bits you can see. But what about the bits you cant? Normally I would not take something like this to bits but due to a mishap I had (see later) I thought I should disconnect the battery. This meant that I would take the GPS to bits and probably never get it back together again.


The next section describes my experiences in the deconstruction of the GPS. I do not recommend you do this at home!!


The insides of the BT308 GPS receiver

Having made the decision to open the GPS I thought that it would be silly not to take some pictures to show you what they are made of.


Essentially the BT308 consists 3 modules: The GPS engine; The power and Control Module and a battery.

These modules can be clearly seen in the picture on the above.

The GPS engine shown to the left and right here is heavily shielded with metal, this stops interference to the sensitive components, and also, unfortunately, prevents us seeing very much.


What can be seen very clearly is the antenna. This is the square terra cotta tile on the right. This is a ceramic patch antenna.


The next module is the power and control module. I assume that this houses the Bluetooth components, but once again this is shielded.


To the left you can see the power switch and the power input socket. Above the power input are the 3 LED indicators. These are channeled to the outside of the case using special lenses.



Finally you can see the inside of the case. This again is shielded, this time with copper foil. There is a break in the shielding to cater for the antenna.


At the top of the left hand of the case you can see the lenses which transmit the indicator lights.


So that is what the unit looks like from both the outside and the inside. What is is like to use.


The GlobalSat BT308 in use

GPS adventures in the Swiss alps.Well this is what it is really all about not what it looks like or what is inside, but how does it work in real life.


I have used the GlobalSat for over four weeks now as my primary GPS receiver. During this time it has been all over Europe, and had a much more stringent test than we normally give equipment. The picture to the right is my iPAQ and the GlobalSat BT308 posing high up in the Swiss Alps.


But coming back down to earth what are the main features of the BT308 and how did they pan out. Primarily they are the GPS receiver of course, the Bluetooth connectivity and the Battery life.


The GPS Receiver

The GPS receiver is based on the SiRF StarII/LP chipset which is one of the most capable GPS engines available today.


When I powered up my receiver having been sent from Taiwan it managed to obtain a factory fix in 50 seconds. Very impressive. Since then I have had longer and shorter TTFF times, and only once had an extended TTFF. This at first concerned me. I reset the receiver and tried again and still no fix. I then got another receiver out and found that that could not get a fix either.


My benchmark for comparison was obviously the Emtac. Over the weeks I ran both receivers in parallel on my test bed and compared the strength of fix, number of satellites fixed, and positional accuracy. These two receivers where pretty much equal in these lab conditions. The GlobalSat is a very sensitive receiver, and seems to hold fixes well under most circumstances.


Out in the field again the performance was impressive. I put it through some pretty nasty environments, where you would expect a GPS to fail, and it did, but it surpassed my expectations. With the two screen shots below I was in some pretty extreme locations (for GPS reception).


The left hand shot, from Fugawi UK, shows a gap in reception for about 500yards, this was taken at the bottom of a steep ravine with heavy Conifer tree coverage. When the fix was there it was accurate.


The right hand shot, using Memory Map Navigator, shows the approach up another tree covered ravine. Here again you can see the loss of signal for about a quarter of a mile, and also the effect of the reflected signals providing an erroneous fix location. In this case the fix stabilised and reported the correct position with a fix on only 2 satellites.

Fugawi UK software   memoryMap Navigator software

Don't get me wrong the above may sound somewhat negative, but in fact it is very positive. This sort of performance is not achieved by well known dedicated handheld devices!!


I have found that no matter which GPS receiver I am using allowing it to get a good strong fix before venturing into marginal signal areas will always give you better reception.


Sitting here writing this review the BT308 GPS is sitting on my windowsill and has a strong seven satellite fix. The other day I was talking to Dave when I noticed that I had a 3D Differential fix using the SBAS signals from the EGNOS system. I was beginning to wonder If I had set the receiver up correctly as I had not seen a differential fix in all my testing up until then.


The Bluetooth Connection

One of the main factors influencing the purchase of a device like this is the fact that it is Bluetooth enabled. When I had my 3870 this was a sheer joy no cables simple reconnection. I have since got an iPAQ 5450 and am sorry to say HP have really taken a step back with this release. Enough whingeing it still works well if slightly irritatingly you are requested to select a Bluetooth device each time you connect.


All official Bluetooth products must go through the Bluetooth Qualification Program. When I started testing the GPS receiver qualification had not been achieved, this has since been accepted on 25 June 2003. The status can be checked on the Bluetooth Qualification List.


Throughout my testing the device communicated with both my PDA and my Laptop well with a couple of exceptions. One a common problem with BT devices is the selection of SiRF mode, the other was a lockup in the BT communications between GPS and PDA/Laptop both of these are known problems and are described in detail below.


One of the tests that I want to perform at some point is to test the range of the BT signal. I have certainly managed to retain a connection at a distance of 10 meters with line of sight. But I was not able to initiate a connection at that distance. This is something which though not critical may affect the way we use the devices. At some stage in the future we will organise some comparative testing of all Bluetooth GPS receivers.


For a couple of applications, in particular the supplied GPSInfo application, I had to make a manual connection to the GPS receiver before running the application. If I did not then the PDA would lock and a soft reset would be required.


These issues may not be the fault of the BT308, they may be related to the implementation of Bluetooth in the iPAQ 5450.


The Battery Life

This is the bit you have all been waiting for isn't it? The BT GPS receiver on steroids. has a large battery but how long does it last?


I was a bit disappointed to see the battery life being quoted as 8 hours continuous use. Especially as the Emtac had a smaller battery and achieved 8 hours in my test environment.


One of the first things that I did was put this to the test now I am obviously not going to sit here watching the GPS to see when it finally runs out of power, so I set up a much more scientific method.


When I started the GPS with a full charged power cell I noted the time. I then connected it to my PDA and ran up OziExplorer CE. I then selected the "Display NMEA Input" option from the menu and off it went recording the GPS input. I left this running all day, checking on it occasionally, it ran for 8 hours, then 9 hours, then 10 hours, then 11 hours...


It was exhausted finally after 11 hours and 28 minutes. Now this was not on trickle power, the was continuous as far as I can tell. I really didn't believe this so I did the same test the next day, and the next and the next. The result was that the battery life averaged a tad over 11 and a half hours throughout 12 tests. I just wish that the PDA battery life was that impressive.


So that is the controlled lab environment. What is it like in the field? Well on all but one occasion the battery outlasted me and my excursions for a day. On the one occasion it failed I had accidentally switched the unit on when putting it into my storage bag. I was out for a long day that day and the battery drained. This may be a design issue as the power switch is on the side where it can easily get caught. It is much more likely a "user" error, as it only happened the once.


The BT308 GPS receiver does not need configuring it will work correctly straight out of the box.


Having said that a GPSInfo utility is supplied with the package. This runs on the PDA and allows you to configure a number of items.

This includes the NMEA VTG data output, the Power Save/ trickle power mode, and WAAS/EGNOS enable.


This configuration is a little confusing as the checkboxes are not active until you connect to the GPS once connected you can check or clear these to enable or disable the function.


At the bottom of the screen there is an Info tab which will display your current satellite information.


NOTE This utility does not allow you to select SiRF or some of the more advanced features of the chipset. See below for more details.


Known Problems

  • When switching from NMEA to SiRF mode using a 3rd party utility it is important that the BAUD rate is set to NMEA 38400 when switching back. If this is not the case then the internal communications link between the Bluetooth module and the GPS Engine will be broken. Beware that this can happen "unintentionally" by using an application such as TomTom and selecting SiRF mode.
    To fix this problem the battery needs to be completely drained and the unit left switched on for 48 hours after.
    This will completely drain all the power from the receiver and reset to factory defaults. This will be fixed in the next release of firmware.
  • I occasionally get problems with the BT interface whereby the receiver just stops outputting data. After this it is difficult to remake the connection. The only reliable way is to power cycle the BT308 and perform a soft reset on the PDA. This is the same with both iPAQ 3870, 5450 and a Portable PC with a TDK BT Dongle. Although this does not happen too often it is a major irritation when it does. When this happens the receiver appears to be working correctly and has a fix.
    GlobalSat are aware of the problem and are working on a fix at the moment.


Where can I get one from?
The UK distributor is Advanced Technology Distribution Ltd Tel: 01243 672800 web www.adtechdistribution.com They are currently supplying NavCity with GlobalSat products and will be entering the high street marketplace soon having agreed to supply Maplin Electronics with the GPS receivers.


For users in other parts of the world contact GlobalSat directly they will be able to tell you who their suppliers are in your region.


This package is ideal for the hikers, fell walkers, outdoor pursuits enthusiast etc who want to be able to have a wireless GPS receiver which has extended battery life.


The biggest plus point here by far is the battery life, which really brings long days activities into easy reach. Coupled with a battery extender and using trickle power save mode this receiver can last longer than you!!


I believe that Bluetooth is the way to go certainly for outdoor GPS applications, the only thing stopping these configurations from being perfect is the implementation of Bluetooth on the PDAs. HP have certainly taken a step back with the iPAQ5450 it will be interesting to see what the new Window Mobile 2003 implementation of Bluetooth is like.


One big plus with this package is that the retail box comes with absolutely everything in it. All the power options and cables you need.


Assuming that the few small problems that I encountered are cleared up then this will be a really first class unit. The ratings below have been made on the assumption that the two known problems are fixed.




Manufacturers Website


UK Distributors


Pocket GPS Contributor

Mike Barrett

Pocket GPS Contributor Website









Overall Rating 95%

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