13916Re: [GPSL] RDF beacon [1 Attachment]
- Apr 15, 2014I've actually AM-modulated this module with both RTTY and also DominoEX. It is weaker than just the carrier but since it drifts a lot due to antenna motion, temperature and voltage the AM-modulation helps to eliminate having to tune around for it.- Bill WB8ELK
From: Bruce Coates <bruce.coates@...>
To: moody.michael <moody.michael@...>; GPSL <GPSL@yahoogroups.com>
Sent: Tue, Apr 15, 2014 10:50 pm
Subject: Re: [GPSL] RDF beacon [1 Attachment]
We've been flying CW beacons on most of our flights. Mine nothing more than 434 MHz transmitter, available from Sparkfun for $3.95. https://www.sparkfun.com/products/10534 It requires a 5v supply. We used to use a microcontroller to modulate it but now we simply feed the 4800 baud TTL GPS data line straight into it. That gives you a convenient 1 second pulsing signal that's really easy to distinguish from the background noise. With good transmit antenna and a yagi receive antenna, we've been able to RDF a payload at over 100,000 feet. At under 20,000 feet it's strong enough for a Doppler DF receiver. It drifts with temperature so you have to tune a bit throughout the flight.
One note of caution. Bill Brown and possibly others use this same module for some of their trackers so it's easy to jam each other in a multi-balloon launch.
(It snowed again today)
SABREOn 15/04/2014 9:28 PM, moody.michael@... wrote:Hi All,In preparation for GPSL2014, does anyone have plans for a DIY RDF beacon that they would like to share? With the tracking failure on one the payloads I was helping Paul track last year, I want to have RDF backup on our flight this year.On an unrelated note, has anyone ever done any kind of special event station during GPSL? I'm planning on bringing some of my HF gear and giving it a go. Anyone want to join in?Mike (ROBOMO balloon team)KD0MEQ
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