On Mon, Oct 12, 2009 at 8:06 PM, Dan Zubey <[email protected]> wrote: > Way off topic, but what antennas are you guys using for this? Vertical > monopoles have a null in the downwards direction. I'm sure it's been > thought out throughly, just curious.
We ran a little inverted V on 2 meters on our balloon based 300 mW tracker. We had no issues with nulls. On the next flight with and HD camera on board, we used a vertical antenna. When the payload was up at about 100,000 or better, people started complaining about loosing packets when we were parked directly under the payload. I fixed the problem on my vehicle very quickly... I moved the magmount antenna I was using from the roof to the side of the vehicle. The null on my RX antenna went horizontal, and that was enough to overcome the effect of the free space losses. Remember you're playing with VHF, and a perfect line of site propagation. It really doesn't take a whole lot of gain to make this work. Putting both antennas directly one over the other, and with nearly 30 km of spacing, we managed to get to where we could not decode the packets from a 300 mW transmitter. From 10,000 feet, you're going to get lots of signal. Of course, if they put stock rubber dummy loads on the radio, and then have them packed in a pouch strapped tight to their legs, you'll see some pretty poor performance as what little signal that gets radiated by the antenna gets absorbed by the flesh nearby. You'll still hear it though. James VE6SRV
