Measuring signal strength


#1

Hi,
I was wondering if there is a way of measuring the signal strength at the antenna while using FlightFeeder. I want to do so to see if moving the antenna around has any real effect of the reliability and quantity of data captured


#2

The transponder signal is not from a fixed location and constantly transmitting like a TV or radio signal. Instead we receive very short pulse for each message that vary in intensity because the planes are moving. Also each plane is transmitting at a different power (from 50W to 250W at the antenna) so there is not an easy way to correlate the signal strength between planes.

There is marginal use for the actual signal strength number. In most cases you either see the signal or you don’t. If you are trying adjust the antenna you can try to watch your direct data feed on the 8080 page. Planes are usually suppose to send out a message every second or so. If the “seen” since number is either 0 or 1 then you most likely are seeing every ADSB message from that plane. If the seen since number is higher then a couple seconds you are missing messages from that plane. You can usually notice when you lost a plane when the number keeps climbing until it reaches about 40 seconds and then removed the the active plane list entirely. This test usually works best when you can see a lot of planes.

You can also setup the antenna in one position and then later try the antenna in another position the next day. You can then compare the coverage on your ADSB stats page on FlightAware. This way will average out the variation you have during the day.

One thing to remember is that the human body is conductive and holding the antenna can alter the reception of the antenna. You can easily see how your hand changes the reception of the antenna by holding different parts.