SysOnChip CF With Notebook

BX10 · Occasional Visitor Joined: Dec 13, 2004 Posts: 4

Hey all, hope someone is still watching this forum.
I got my SysOnChip CF Plus II working great with my PDA.
The problem is that I can't get it to work with my notebook.
I use a CF->PCMCIA adapter that was shipped with a CF Modem.
Using NMEA 4800 and viewing the incoming sentences with Hyperterm, I notice that although I get sentences like $GPGGA , the parts that should
contain lat lon and other fix information are always empty.
Always means that I had my laptop placed vertically (really!!!) for 1 whole
night and still couldn't get a fix. From exactly the same position using my PDA I had a position fix in no time.
Facts:
1) GPS Works (because it works with my PDA)
2) GPS Works with laptop (because I can see the incoming NMEA data)
3) NMEA Data contain no fix information.

Some voltage problem?
Contacted SysOnChip via e-mail -> No answer (I wonder if these guys can even understand english).

Any help guyz?

Mapwalker · Occasional Visitor Joined: Nov 04, 2004 Posts: 35

I suppose you did set the interface (NMEA 4800 bps) exactly the same on both the GPS and your laptop-software. You did install the Syson PC-driver? I don't expect a voltage problem, the red light on your Syson is on all the time?

BX10 · Occasional Visitor Joined: Dec 13, 2004 Posts: 4

Yup, GPS is on 4800 bps, want-to-be Driver installed, red light always on.
Still no answer from SysOnChip. Not even a "We will reply soon...".

Could be a voltage problem, a design flaw or something inside the gps
that prevents it from running normally.
Anyone else experiencing similar problems?
Has anyone used it with a laptop and with what settings - software - CF2PCMCIA adapter?

sigh...

DavidW · Posted: Wed Dec 15, 2004 9:56 pm Post subject:

Many laptops, particularly cheap ones, put out so much RF noise that a GPS receiver in a PC Card slot won't work.

I tried my Haicom HI-303MMF in an adapter in both a Compal ACL00 (cheap Taiwanese laptop) and a Dell Latitude D600 (a much better machine).

The GPS reception in the Compal was awful; one or two satellites at most. I could replicate the issue by putting the GPS in a Pocket PC and bringing it close to the laptop when it was on. The GPS reception in the Dell is fine - I get the same number of satellites at the same signal strength as I do with the receiver in a Pocket PC.

David

BX10 · Occasional Visitor Joined: Dec 13, 2004 Posts: 4

Elementary my dear Watson!
You are probably right... Of course... RF (and yes my laptop is cheap).
btw : The guys from SysOnChip finally sent a reply suggesting I should purchase the external antenna for better reception.
Anyway, David, your theory must be more than solid. Thanx for the
reply and the bright idea. I will now perform the following 3 tests:
1) Use tin foil to guard the antenna from the laptop emissions
2) Check to see if the GPS works on PDA but near the laptop
3) Use an oscillator to check for RF and the wave impact on the GPS Unit.

I will post again as soon as I got some results.
. .-.. . -- . -. - .- .-. -.-- -- -.-- -.. . .- .-. -.. .- ..- .. -..

DavidW · Posted: Thu Dec 16, 2004 3:02 pm Post subject:

With the screening experiments, you may land up detuning the antenna - but you can only try.

Number 2 should be easy to try - it's probably easier to bring the laptop near the GPS when running rather than the other way round, so your baseline doesn't move by moving the GPS. Be aware that the results may differ depending on whether the laptop is running on battery, running on mains and not charging its battery, or running on mains and charging the battery - also that whether or not add on hardware like wireless LAN cards and Bluetooth is in use may also make a difference.

Number 3 - 1575.42MHz is the frequency of interest, being the GPS L1 frequency. At the moment, there's no civilian GPS on other frequencies. Don't forget the problem of strong harmonics.

There's a dit missing from the antepenultimate (second from the last) character in your Morse.

Overall, I'm extremely impressed with the Dell Latitude - this was the laptop I was responsible for buying, not the Compal (that one came along with a contract).

I'm a full UK Amateur Radio licence holder - hence the RF background knowledge. I was Class A when there used to be a difference, gaining Class A by taking and passing a 12wpm Morse test.

dah-dah-di-di-dit di-di-di-dah-dah dit di-di-dit dah-di-dit di-dah-di-dit (which I'll have to explain if you don't know Amateur prosigns - and yes, the first two characters are numbers)

David

BX10 · Occasional Visitor Joined: Dec 13, 2004 Posts: 4

Results,
1) Using tin foil failed.
2) PDA had good reception even when close to the Notebook.
3) Oscillator readings varied by HDD Access and WiFi !!!

...so I decided to buy an external antenna.
Problem solved! I get 9 to 11 satellites within 30 seconds even in my garage.
External antenna is a must. I've written a program to log NMEA positions in a database to get some statistics. So far the standard deviation is about X:6meters and Y:5meters (UTM-WGS). I'll keep you all informed about the reception of this unit.

-.. .- ..- . - .... .- -. -..- ..-. --- .-. . ..- . .-. -.-- - .... .. -. --. .-.-.- .. .- -- -. --- - .- .-. .- -.. .. --- .- -- .- - . ..- .-. .-.-.- . ..- . -. .. ..-. .. .-- .- ... --..-- .. .-.. .. ..- . .. -. --. .-. . . -.-. . --..-- -... ..- - -.-- --- ..- -.-. .- -. ..- ... . -- -.-- . -- .- .. .-.. .-.-.-

Kala Christougenna (Merry Christmas)

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