I inherited some 900mhz Comtelco Yagi stacked antenna kits. They are two 900mhz yagi’s designed to stack on top of each other.
http://www.comtelcoantennas.com/PDF%20Datasheets/2Y33810.pdf
Has anyone ever used anything like this? They say 15dBd gain which is 17.15dBi gain. I’m going to try them out tomorrow but that is pretty incredible if the work…
I’ve used stacked yagi’s before in different applications and they perform rather well so if you got them for free, more power to you. I wouldn’t personally buy them because a parabolic offers more gain with the same directional properties unless I was really cramped for space. Yagi beamwidth is too narrow to use for any type of a broadcast situation, making them only useful for ptp, in which case, a dish will offer more gain for the same price except the cost of the extra space at low frequencies. Yagi’s really shine at low frequencies where a dish would have to be the size of a house to have similar performance, I.E. 1GHz and lower. Let us know how those turn out.
The best yagi configuration I ever saw used a grid backplane with four Scala yagi’s spaced within the square grid. It was tuned for about 670MHz and was delivering about 22 dBi of gain at that frequency. Those particular Comtelco’s I’ve never had any experience with but we have used some Maxrad yagi’s in a stacked configuration and in non-wifi applications I’ve been around some massive Maxrad, Andrew and Scala dual and quad yagi configurations. I don’t know how wild I am about the SWR on those and as with all yagi antenna, the front to back is ugly but you can’t win 'em all.
anytime you use two antennas stacked in phase properly you gain only 3db above a single antenna. If 3 db makes that much difference you should condsider shanging something else to improve the link.
Done incorrectly it will cause you more problems than it would have ever solved.
Scott
For every 2db increase in gain you effectively double your range.
In my case a -87 signal went to a -77 signal.
I think you meant to say every 3db you double your range. But in any case, you double your power not your range necessarily with each 3db. I’ve never had a backhaul where 3db was a make or break, and certainly not had the luxery of of using twice the tower space. Safe margins are like 10db so having 2 more isn’t buying much.
I guess my point was to use a 3db stronger antenna in the first place or use a xr5 with 3db more power (or similar card) or better coax, etc… All of which are better options than stacked antennas which can gain you 2-3 db.
Scott
You need 6db more to double your range. (double the power twice) It’s the inverse square law.
Also, don’t forget that some of the additional gain will be lost to “free space loss” anyway, so you need even a little bit more for a “real” double of range.
23dBm = 200mw
26dBm = 400mw
I believe 3db would be the correct assumption to double your power.
3db more isn’t an assumption - its a fact.