I recently got myself set up with a Pi running PiAware. At the moment, I’m receiving through the FlightAware antenna, and feeding it directly into the dongle using the N to MCX adapter/pigtail. Obviously given the short lead, this means that it’s all indoor, and really isn’t picking much up (understandably so). My plan is to move this down to our hangar down at HEF and mount it up on the roof, but that will also mean making it a little more sophisticated.
What I have:
-FlightAware filter (in my possession, not utilized at the moment)
My questions are the following:
-I’m assuming that an amp will be helpful, but I haven’t found an amp for the frequency range that uses either an SMA or an N connector (or the ones I’ve seen don’t list the connector type at all). Any recommendations?
-Is there any benefit to adding power to the antenna? Anything I should consider here or look at?
-Any suggestions to an “optimal layout” between the antenna and the Pi?
I’m somewhat of a radio novice, though I do understand what’s going on, in general. My grandfather was really into amateur radio (W4WWG if I recall correctly) and worked in military communication in some capacity, so I grew up around it, but I unfortunately never picked his brain about it much before Alzheimer’s did.
There are amps available from China on ebay for about $10 (search ‘low noise RF amplifier’ ) but they come as a circuit board with SMA connectors and dangly wires for power. so would need a box and a method of powering the amp.
Thanks Peter. I’ll give it some thought as to how I should lay it all out. If I got an amp from China, would there be any issues from the differences in mains power? I’m in the States, so we are on 120V/60Hz instead of 230V/50Hz.
Be aware - That particular amplifier is fitted with a SAW filter - most are at 435Mhz - I have one on my bench at the moment. The SAW filer would need changing for a 1090Mhz one for ADS B (the reason it is on my bench is that I’ve not gotten around to doing it).
It could be powered up the wire if a coil of maybe 15 turns 6mm diameter was taken from the RFout to the +ve connection point
Just a couple of tips (that you may or may not already be aware of)…
Visibility to the horizon is THE most important (higher is better, above all obstructions is key).
Keeping the number of adapters, couplers, etc. between the dongle and antenna is extremely important
Keeping the length of feed line between the dongle and antenna is very important
If your feed line must be longer than just an MCX-to-N (or SMA) pigtail, use the lowest-loss coax that makes sense, given the length you need and the frequency (1090Mhz, or 1.1GHz on loss charts)
Do all of that, and then carefully measure your performance for a while to establish a “baseline” without an amp. Keep tweaking 1-4 until you cannot improve any further on your setup.
Introduce an amplifier absolutely last. Remember, amps will drastically raise the noise floor. Maximizing your signal-to-noise ratio is the goal.
For a point of reference, note my two stations. #5894 is at my home, with a discone antenna above the roof line. Admirable, but nothing special (I’m in a fairly pronounced valley). Now, my second station (put on the air last week), #15456, is on a mountain top (only two miles from my home, but > 600’ higher with no obstructions). It’s using a dongle, and FA antenna… No amp, no filter, and 65’ of LMR-400 feedline (with a coupler, sadly, only two 32’ segments were available at the time)… Note the performance difference between the two stations.
Higher is better, but most effective upto the point to bring antenna above all obstructions, so that it can “see” the horizon all around. Any further increase in height increases the cost & effort, with little benefit (unless the increase in height is in hunreds of feet).
Since the maximum POSSIBLE range at any location depends on terrain, curvature of earth and antenna height, and aeroplane height, it is important to determine this for your location. Please visit the thread shown below for step-by-step guide to determine your maximum range. Generally the maximum flight altitude for commercial planes is 40,000 feet, I normally use this figure to get my location’s maximum range.