Hi all, I was trying to find out the nominal length for a ADS-B antenna, I thought it was around 67mm from base to tip and yet I have seen all sorts of sizes supplied with a dongle when purchased and only the other day I saw a freebie kit you could apply for and the antenna was 62cm. I ask because I have a pole UHF/VHF antenna about 6 foot in length (that I am not using any more) and was wondering if this would make a good ADS-B antenna cut to the correct length and mounted on my roof. Thanks. Cheers Colin
There are a lot of factors that go into an antenna including the type, 67mm is correct for the small mag-mount antenna that comes with many kits. There are kilts with other lengths but those are usually not actually tuned to 1090 and hence why it is recommended to cut them. Larger antenna are more then a single wire and can not simply be cut to size as it consists of many components that would all need to be adjusted properly. Short answer, unless you understand antenna engineering very well and have the proper equipment it is unlikely you can cut and adjust your UHF/VHF antenna to work.
Hi K4HLW, Thanks for your comments and no I don't fully understand the the workings of a ADS-B antenna, I was thinking more of discarding the innards and just using the external tube and base coupling, although I have used an August TV antenna with a fitted signal booster and it increased my south eastern distance by just under 80nm's, my westerly direction is quite weak being uphill. I was told it would never work for ADS-B but I sat here and looked at the results for myself, it seemed that it would only work as a internal antenna though, I recently put it on the roof and the signals plummeted so I have gone back to a stock antenna and at present making myself a, well, not sure what it is actually, 1/4 wave 1/2 wave but it is supposed to be specifically for ADS-B, it's 10 lengths of coax by 110mm plus two 30mm long bare centre cores either end, I'll test it on one of my pi's at ground level first before I put it on the roof. That's about it really I'll see how this goes before I descend any deeper into the world of antennae and whether I should purchase one. Thanks again. Colin
I used the 67-69 mm antenna with very good results. Then I bought one of the dual band antennas on this sites store. It makes a huge difference. I’m seeing aircraft out 200 + miles. The only thing with this antenna is I lose aircraft as they fly over the top of me. There is a cone of silence that happens. Once the aircraft exit it I see them again. Either that or my gain is set to high. In either case, it works good enough for me. No one is relying on my data. Here’s a recent shot using the dual band antenna viewing only 1090mhz. Don.
Hello Don, Very nice catchment there. Like you I have been using the cut down stock antenna with very good results, I then moved on to a small TV antenna along with a signal booster, which increased my range to around the 250mls and I have now built my own Franklin type antenna and have a reach of 300mls on a good day and doubled my aircraft quantity, which I am very pleased with but I stand by the TV antenna as this also increased both my range and quantity from just a shelf in one corner of my office but alas it seems the signal booster has given up. I still do use the cut down stock antenna perched on my office window sill and am still getting a really good Southern distance but being on the ground floor all other directions are very poor but it's good for testing, rather than messing around with my uploading Raspberry pi, which is in my loft and the Franklin on the roof. I've attached a picture but it seems very quiet at the moment, even so I have 40 plus, I was getting a hundred or more Tuesday. Looking at the picture it would seem I have your problem of a blank area over head, not really noticed it before but I will have to investigate it now to see if I can cure it. At the moment I am using my discone (for my scanners) antenna pole to mount the Franklin, maybe that is something to do with it, I'd planned on moving it anyway. The increments on the range rings are 25 miles, the polar diagram is courtesy of Open Sky. Nice to hear from you Don, and thanks for the antenna details. Regards. Colin
whoops, Looks like the attachments didn't work. Try again, Seems like my files won't upload, I'll work on it and send one later, maybe the file is too big. Regards. Colin
You are correct in thinking your gain is possible set too high with the stronger antenna and closer aircraft are overpowering the SDR, you may also see other weaker aircraft disappear when one is overhead as it drowns out the other signals. You can use the gain script to adjust it or do it by hand until you are happy with the results. You will find you start to lose range if you lower gain too far and what the prefect setting will be will be as much science as your goals (priority on max range or nearby aircraft). If you use the main website map usually a nearby feeder picks it up in your dead spot and you will be able to track it through.
I will certainly check that out, I put that patch down to, in the past, as the Military Training area that is above me and then never gave it much thought. I'm not far from Lakenheath, Mildenhall, Marham and Wattisham, hence the big training area, your reply could also be the answer to another question (and probably more) in that, especially in the summer, I see quite a few private planes overhead but not on the map, OK, some would say that maybe they are not ADSB equipped and could probably be correct, we shall see. Thanks again Don, your reply is very much appreciated and I shall post here how much and what difference the change has made. Take care. Colin
Hello Don, Getting back to the antenna blind spot I took this shot and and it doesn't seem as bad but definitely a thinning out in the centre ring. If this picture goes ok I'll let you know how I get on, can't see why it won't send it it's only 64kb, it's telling me it's not an image now, I sent a picture a little while ago and it went ok, I'll re-save it as a .jpg and see. Cheers. Colin
