190 replies to this topic

[jparisse]

Thomas... You are like the Shaolin Priest from the old Kung Fu movies! Totally wise but cryptic to your followers!

I have two sentences setup: GGA and RMC each at 1Hz so the data seems continuous to this human processor. I understand about the pauses but don't understand how one can program the GPS unit to produce them... Should I just lengthen the pause time between the sentences I am currently using (say 2 or 3Hz)? Is it that easy?

Thanks for teaching me so much. Someday I hope to snatch the pebble from your hand...

Jeff

Mark... That is VERY cool and about time (ask 'em to make a 1000mW).

Edited by jparisse, 29 May 2007 - 11:33 AM.

[Mark Harris]

This website has pretty much everything you can send a GPS:
http://www.gpsinform...g/dale/nmea.htm

[qnzkrew]

im starting to put my plane back together. i have a dzl modem. i have few questions. what is the voltage do i use to power the dzl modem. and for the gps input. i have a geko 201 that i am feeding my osd with. which two wires do i need to feed the dzl modem out of the gps. i have red black white and brown coming out of the gps. thanks

[jparisse]

DZL TX takes 5v which you can get from your RC RX. The GPS connects to the lower of two connector (connectors to the left) with just GND and TX lines (black and yellow).

Jeff

[ThomasScherrer]

Jeff, if will not work if you dont have tiny delays in the datastream,
it is impossible to see using a terminal,
but easy to see if the data is sampled with your PC audio input,
just record 2 sec, zoom in and scrool back and forward,
you will then see the delays between the pakages,
at least 2-3 chars needed, more is even better.

I dont know your GPS type but most of the GPS modules we normally use can be configured to send some pakages at slower rates, leaving spaces for re-sync,
the phase modulation the DZL model encode and decode MUST have those spaces,
if no spaces it actually works in the lab, but on the plane you will get short drop outs or other noise glitches, this will in some cases be counted as a data pulse, and then all following datapulses could be inverted, that is why you need a clean space to resync, if this space come every sec, you will get a fast re sync and your overall good data will be much better.

[tazdevil3000]

hi , my DLZ working fine on table with airwave module ,need to test with 900 mhz TX from long range video cause of using a spektrum radio ....


thank for the kit

Edited by tazdevil3000, 14 June 2007 - 01:31 AM.

[Hartwig]

Thomas, which configuration do you recommend for the EM406/411?
RMC, VTG, GGA, all once per second? Is that ok, or should I leave more space?

[ThomasScherrer]

Hartwig, I recomment you fint out what messages you need,
and only turn on them,
and then you measure the data and delays using the sound card methode,
I know I only need VTG and GGA for my project,
but other things like PDA with tomtom and so might need more or less messages,

Edited by ThomasScherrer, 15 June 2007 - 12:10 AM.

[Flankerubt]

Hi there


The system look very nice, I will like to order one as well

[FredericG]

Today I tested a modem in combination with my Lawmate system. I understood that the modem I received worked well on a an Airwave video system but for me it did not work at all.

I did some tests with a function generator and this is what I found:
- The cutoff frequency is about 20kHz
- The input started to saturate from 600mV (p-p) for a sinus.
- For a square-ware the signal looked best below 400mV (p-p)
- Even after filtering the signal a bit, above 300mV some interference in the video-channel started to show (I used a uniform blue screen; probably very sensitive). So I decided to use a signal of 300mV (p-p)

I decided to use a voltage-divider to lower the 5V signal to 300mV. After that a resistor of 1K, combined with the capacitive input of the TX, cleaned-up the sharp edges.

I have very little experience with this. Does this all look sensible and a good approach?

Thanks,
Frederic

Attached Thumbnails

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Edited by FredericG, 16 December 2007 - 10:36 AM.

[FredericG]

Here is a picture of the signal fed to the TX (on top, 100mV/div) and what comes out of the RX (1V/div).

Attached Thumbnails

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Edited by FredericG, 16 December 2007 - 10:42 AM.

[Mr.RC-Cam]

Your output waveform looks very faithful to the original. So, you are on the right track. If your audio drive continues to cause video interference, then try filtering the input waveform so that it is more sinusoidal (soften the square edges -- they are evil).

[FredericG]

Thanks for the feedback and the advise!

Something I forgot to ask. I am surprised the audio signal is amplified by 10...
From a capture of Thomas, I recall that the amplitude of the signal supplied to the TX was the same as the audio signal coming out of the RX.

Is this not surprising? Could it be that my system is designed to connect a microphone? (Don't know what comes out of a microphone)

Thanks,
Frederic

[Mr.RC-Cam]

From a capture of Thomas, I recall that the amplitude of the signal supplied to the TX was the same as the audio signal coming out of the RX.

ThomasS used Airwave A/V modules and they require a preamp when a typical microphone is used. So, that made his modem integration a bit easier.

Could it be that my system is designed to connect a microphone?

Some A/V Tx's have an internal preamp so that cheap electret condenser microphones can be directly connected. Those will need attenuation when a modem is connected.

[Jan]

Gentlemen,

It was with great interest I read through this thread, but why did it suddenly stop?
Did anyone come to a conclusion? Was is possible to transmit the NMEA signal and was the received signal good enough to use?
If a product came out of this, I would really like to buy a couple

Jan

[W3FJW-Ron]

Some A/V Tx's have an internal preamp so that cheap electret condenser microphones can be directly connected. Those will need attenuation when a modem is connected.

Might consider an inline capacitor as well to keep the electret cartridge voltage from feeding into the output of the modem unless there's a voltage block built into the modem..

Edited by W3FJW-Ron, 10 March 2008 - 07:13 AM.

[Hartwig]

Gentlemen,

It was with great interest I read through this thread, but why did it suddenly stop?
Did anyone come to a conclusion? Was is possible to transmit the NMEA signal and was the received signal good enough to use?
If a product came out of this, I would really like to buy a couple

Jan

Hello Jan,
I tried this and it works fine. The only thing is that you have to limit the NMEA output of your GPS receiver to the sentences which you definitely need, and at a reasonable rate. The circuit needs some "recovery pause", as Thomas mentioned before. I limited it to RMC and GGA, both at 1Hz which seems to be fine.

Jeff (jparisse) offered the kit a while ago. Maybe he still does. You might like to send him a pm and ask.

Cheers,
Hartwig

[Jan]

Hi Hartwig,

An update of 1 Hz would be more than good enough and the most important thing to transfer to the ground is the position of the RPV.
I have been offered a couple of sets from one of the members in this forum already at almost no cost :-) , but thanks anyway.

Regards
Jan

Hello Jan,
I tried this and it works fine. The only thing is that you have to limit the NMEA output of your GPS receiver to the sentences which you definitely need, and at a reasonable rate. The circuit needs some "recovery pause", as Thomas mentioned before. I limited it to RMC and GGA, both at 1Hz which seems to be fine.

Jeff (jparisse) offered the kit a while ago. Maybe he still does. You might like to send him a pm and ask.

Cheers,
Hartwig

[saabguyspg]

I too read this discussion front to back getting more excited for a final product... but alas... there is none... or is there? I would be more than willing to pay for one of these kits but i use the lawmate tx on 900mz is this going to be a real difficult thing to fix if I can convince someone to sell me one???

Thanks for all your hard work guys and I hope to hear from someone. PM is preferred.

Steve

[Dimitris76]

I too read this discussion front to back getting more excited for a final product... but alas... there is none... or is there? I would be more than willing to pay for one of these kits but i use the lawmate tx on 900mz is this going to be a real difficult thing to fix if I can convince someone to sell me one???

Thanks for all your hard work guys and I hope to hear from someone. PM is preferred.

Steve

Steve,

you can order Airwave and Lawmate TX versions of this modem and the RX side (which includes a RS232 port) here:

http://alai.h3m.com/...fc89f8cc84db486

Cheers
Dimitris