20 meter beacon for long duration balloons

I've been working on a 20 meter BPSK beacon to act as a light weight payload for longer duration balloons. The total payload weight is 12 oz. including beacon, GPS, HF antenna, solar cells and short term energy storage for burst transmissions.

This will only transmit during daylight hours but a battery can be added for night time use.

Total output power is 1 watt PEP. It transmits a BPSK31 string that is the same format as an APRS message except for the check sum format. The initial frequency will be 14.069 MHz, just below the PSK band.

It is capable of using the GPS output to correct the transmit frequency to within +- 10 Hz. Initially I plan to transmit a 25 second beacon every 5 minutes. This will allow 10 different beacons to use the same frequency since each one will be assigned a 30 second nonoverlaping timeslot.

No batteries are needed for daytime use and the expected life is unlimited (except for UV degradation of the solar cells).

The initial prototype should be ready in a month or two. It consistes of three PCBs mounted together.

After I check out the prototype I will order the 3.5" X 3.5" PCB that will incorporate all parts on one PCB. This is a 4 layer PCB and has manufacturing setup costs of $140 and then about $20 per board, so it makes sense to get as many as possible.

I'll be setting up a web site in the future to post my progress.

Anyone interested in participating or making suggestions please drop me a line here or at w3rfa AT arrl.net

Steve, W3RFA

 

The price for the 3.5" x 3.5" HF beacon PCBs are:

Quantity ea. no SM ea. with SM
2 $83.35 $141.46
6 $33.35 $53.13
10 $23.35 $35.46
20 $15.85 $22.21
50 $11.35 $14.25

The microcontroller has a pin pitch of 0.65mm so solder mask would be useful especially if a contract manufacturer is used to install the surface mount parts.

 

I've setup a website with some more info

http://members.myactv.net/~w3rfa/