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Video and telemetry equipment

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:) Hi, I just come over this Forum when hunting for some devices on Internet.

I have been fascinated to remote video and telemetry systems for RC planes

Since I first saw one system I work last summer. I thought for awhile that I were

The only one working with an idea to send RS232 data-steams through the

audio channel on a video transmitter. But then I came stumbling into this

Forum and reading about experience on the tema. I have tried some cheap

equipment in the start, but this has been thrown away quickly. I have now

a video x-mitter for 900Mhz and I went for the Airtel 6 system for telemetry

device. I have found a descent-size GPS receiver board from Evermoore

that is mounted into the Airtel6 box where the battery is suppose to be. Since

I will be using a high-capacity battery for all equipment together, I had no

use for the battery in The Airtel 6 unit. I have trying to get FSK to work

with the system, but the speed was limited to 1200 baud, so I was thinking

of PSK instead. I so fare haven’t seen anything that can take care of 4800

baud, what’s the minimum speed that will be accepted for 1 sec. Update

on the Telemetry side.

Are there others here that have experience with the Airtel 6 system ?

I just get it together before Christmas, and the testing I have done is

pure table testing. I’m not finished with my aeroplane that will carry

the stuff yet. Hopefully I can get it together for the summer season ?

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I have trying to get FSK to work

with the system, but the speed was limited to 1200 baud

I have run into similar limitation for my telemetry project. 1200 baud is the rate normally used for APRS with radio modems. To bypass this limit I've built my own modem using ATMega128 processor. Currently I've tested the modem to work at 4800 bps (using AFSK modulation) but theoretically it should do go all the way to 9600 bps. So, it's possible to go faster than 1200 with little bit of work, but may I ask why do you need 4800 bps rates?

Regards,

Val.

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:) (Uups !by the way, I saw that this topic should have been posted under another tema, better off next time !)

The project I came up with was also AFSK, and I used some bits of electronics to support on the transmitter end. On the receiver end I use a program that’s call MMTTY, and are a shareware program made for RTTY/ Ham use. But here is the biggest achievement to have a good decoding unit at the receiver end. Have you got any experience with other software that’s available for PC use, and that can be used also on frequencies over 5Khz ?

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I use BayCom's soundcard driver (from http://www.baycom.org/) to receive at 4800 bds. The benefit of the driver is that it is configurable for any baud rates mark/space frequencies. I also use AGWPE driver for 1200 bds and it is supposed to support 9600 bds but I haven't tested it yet.

Regards,

Val.

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:) Hi there, and tnx 4 reply. It’s interesting that other are dealing with the same experience that I got. I need 4800baud first of all to get the GPS data-flow within 1 sec. With 1200 baud, I loose too much data within a 4 – 5 seconds period. And there is a lot happened in the air within 5 seconds! I thought AGWPE was a kind of gateway program for Internet / radio support, but I haven’t tried it myself. I red someplace here a solution on a chip from CML,

CMX 469. Have anybody got some luck with this one, or is there other circuit around that’s small enough to bring into a telemetry-box? I really want to integrate the system as much as possible, than there will be a chance of taking it into the air!

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Why not use TinyTrack? It sends most of relevant GPS data with one second updates. TinyTrack transmitts on 1200 bds and it's possible to use AGWPE with it. The reason it can do 1200 bds from 4800 bds data stream is because it throws away lots of unnecessary NMEA sentences that are coming from GPS receiver and only keeps "good" ones with lat/long, bearing and ground speed data.

Regards,

Val.

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Why not use TinyTrack? It sends most of relevant GPS data with one second updates. TinyTrack transmitts on 1200 bds and it's possible to use AGWPE with it. The reason it can do 1200 bds from 4800 bds data stream is because it throws away lots of unnecessary NMEA sentences that are coming from GPS receiver and only keeps "good" ones with lat/long, bearing and ground speed data.

Regards,

Val.

:) I had a conversation with the maker of TinyTrack, and to my acknowledge this unit was made for GPS data-stream. What I want is a transfer of the whole data-stream that available from Airtel 6 including the GPS sentence. The format from the Airtel6 is unique, and it’s sending with 4800 baud. I have tried it down to 1200, but as I said this is too low for getting the resolution good enough for aeroplane. I have to find something that’s in depended of that data-format either its GPS or telemetry, and can easily be changed for its use.

You can have a look at my homepage under “telemetry” were you find my trying with a simple “Schmitt-trigger circuit” as FSK modulator, and transfer from the Airtel with 1200 baud. I also have a picture of a nice small GPS receiver I squeezed into the same box.

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