I have a Signalplus 1090MHz ADS-B Antenna-Omni Fiberglass Antenna 12dbi antenna (which is not dual band) that has single coax (S-MR240) that is 25’ that goes to an Antenna Adapter Splitter Cable SMA Female to Dual SMA Male with the output going to a Pro Stick (978) and the other to a Pro Stick Plus (1090). This has worked well.
But to improve reception I am adding a FlightAware ADS-B Antenna - Dual Band 1090MHz/978MHz, Omnidirectional, 6dBi for use on 978 and LMR400 coax to the Pro Stick. And removing the S-MR240 coax and replace also with a LMR240 line from the 1090 antenna to the Pro Stick Plus. So basically, one antenna, coax and dongle for each.
The question is what type of separation do I need for two receive only antennas? Both will be placed on a DX Engineering Complete Fiberglass Tubing and Cam Lock Clamp Kits DXE-TFK25-HD. This places the top antenna above my roof line. So can the antennas be side by side or do I need one above the other?
I have checked the site of original manufacturer Signalplus. It has a huge collection of antennas for Cellular & WiFi bands, but only following two antennas for 1090 MHz
Thanks for the comment on stacking. I will do that with the 1090 at the top and 978 below it.
For the comment on the Signalplus I also checked their site. The one I have I bought via Amazon. I will say with it on 25’ of S-MR240 direct to the Pro Stick Plus I say the highest connection of data ever. When I split the coax I saw the drop so this is what separate antennas and coax.
Thanks
For a pair of ‘receive only’ antennas, it really isn’t a problem. Sure, if they are only mm apart, they will de-tune each other, but a wave-length separation is more than enough.
Remembering the plastic raydome of each antenna is RF transparent and the active (metal) part of the antenna is only a mm or two thick, shadowing isn’t a problem either.
I have at least 5 receiving / transmitting antennas within 5cm x 10cm space of my cell phone. No problems at all.
(voice receive, voice transmitt, data, bluetooth, wifi, 6G, LTE, and may be many more). Of course these are optimally designed by expert engineers to cope with this space limitation.
Did you start with a FlightAware ADS-B antenna before getting the Signalplus? If so, how much improvement did you notice? I bought the Signalplus and will replace my FlightAware antenna one of these days. Thanks.
I started with a different antenna but with the SignalPlus I saw a significant difference with same height and same coax so all of the improvement on 8/29 was the antenna. After that I made changes which degraded the signal. Will share after I change out what I want which should bring 1090 back up.
Increasing antenna gain follows law of diminishing return.
By replacing a Spider (2.2 dBi gain) by a wire collinear like Flightaware antenna (5.5 dBi gain), gives a big jump in performance. However as an antenna of 5.5 dBi is replaced by a 9 dBi antenna, there is definitely some improvement, but not as much as when a 2.2 dBi is replaced by a 5.5 dBi. Similarly improvement is still lesser when 9 dBi is replaced by 12 dBi. The law of diminishing return is very prominent above 6 dBi. I feel that is why Flightaware and Adsbexchange are selling 6 dBi antennas as this is a good compromise between cost & performance.
Fair statement. I am using the FlightAware Dual Band antenna which is 6dBi for the 978 feed. I may even get a wild hair and swap once I have separate LMR400 coax runs to see what 12dBi does vs 6dBi for 1090. Pic is of 25’ DX Engineering Fiberglass tubing I will have 1090 at top (as seen now) and 978 below it.
Thanks. I’m hoping to see improvement, too. I want to put the SignalPlus on the roof, but I’m 73 and my daughters are terrified of me rolling off! My son in law offered to help, but he’s very busy with work and leaving soon on a business trip. I have a small bamboo forest on my property and some of them are very large. I cut down a sturdy one today that ended up being 26 feet tall after I trimmed it. I may use that temporarily until I can mount the antenna on the roof. The base is about four inches in diameter and the tip is about one and three quarter inches in diameter.
What you say is right because ADS-B is highly LOS, so once you are seeing every aircraft, doubling the gain won’t find any more.
There are also other considerations too - on an end-fed antenna, adding 3dB requires the antenna length to double. This increases wind loading, so the mounting must be more robust, but also you quickly find it’s too expensive to ship.
Definitely can confirm this as well. I went to great lengths trying to get the most out of my main site using a 9dBi antenna over the more typical 5dBi antennas, along with an LNA and a bunch of filtering, and it only netted me some marginal improvements for picking up distant planes out to 250 nmi. The wind loading issue with such a long antenna I had to solve with some creative 3D printing whereas the 5dBi antennas are fine with the mounting hardware they provide.
I have another site using just the FlightAware-provided equipment and it consistently gets an extra 50 nmi of range compared to my main site. Granted, that site can look out over the ocean and the additional range only occurs at a certain direction, but the main point I’m agreeing on still stands: once the antenna can “see” ADS-B signals, increasing the gain isn’t a panacea for picking up more aircraft.
But back to the OP: hopefully there’ll be some positive results with all the changes being done.
I like the sounds of your bamboo pole creation. That may work so well that it will keep you off the roof all together. I use a thick wall aluminum military surplus sectional mast pole arrangement that is ground based and it keeps me off the roof.
