Re: LightAPRS Tracker

J68HZ
 

I bought one of these things… programmed it (listened for it on my 2 meter radio), and tried using it at Dayton.  I even used a 4’ car top mount antenna with it and it has never once registered on APRS running all over the USA for a week.  I have an arrow antenna and will try the thing this afternoon but so far not impressed with this $100 item.

 

 

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From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mustafa Tan
Sent: Saturday, May 25, 2019 7:12 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] LightAPRS Tracker

 

Hi Leigh,

 

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?

 

On startup, GPS needs at least 2-3 minutes to fix 4 satellites. Since GPS antenna is passive, it can not fix very quick. After first gps fix and first beacon, default code sleeps GPS module (and also RF module)  until next beacon but gps backup pin is still powered so it wakes up quick.

 

2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?

 

You can modify LibAPRS preamble and tail parameters as follows: (we use default values)

 

  // You can define preamble and tail like this:

  // APRS_setPreamble(350);

  // APRS_setTail(50);

 

but not volume level via software 

 

3. Is there a schematic?  For example, see next question.

 

Unfortunately not :(

 

4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?

 

We did not use LED to save power. But we are using TX Led port (MigthyCore Atmega1284 Port 1 -> LibAPRS PB1 port ) to configure PTT duration of DRA818V.

 

5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

 

  RfON; -> Wake up RF (DRA818V) module

  delay(2000); -> DRA818V needs at least 2 seconds to wake up 

  RfPttON; -> PTT on

  delay(1000); -> DRA818V need at least 1 second to gain max power

 

Also you can modify these parameters above but we found out these values after many tests.

 

I hope my answers help, please do not hesitate to ask any other questions if you need.

 

TA2MUN

 

On Sat, May 25, 2019 at 2:13 AM Leigh L Klotz, Jr. <leigh@...> wrote:

This looks great!  Thanks Mustafa and Hans!  I received mine and used Arduino IDE to program it and am getting mixed results, so I'm looking for debugging guidance. 

I will take a look at the audio spectrum on the receive side soon, to see if all looks OK, but in the meantime I have a few questions:

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?
2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?
3. Is there a schematic?  For example, see next question.
4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?
5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

73 es MNY TNX,
Leigh/WA5ZNU


 

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