Hey all, Been feeding FA for a few weeks, just started feeding this site also. Thought I'd share a pic of my attic collinear antenna. I don't have a ladder long enough to put an antenna near the top of the house, and wouldn't want to climb that high even if I did... Tried a few spider antennas in the attic but this collinear has been the best so far, haven't tried a J-pole and not sure I'll bother since I doubt it would do any better than the collinear. Since it's in the attic my range is only about 150 miles, but I'm able to see aircraft landing at KPHL (5 miles away) down to about 50 feet, and news choppers hovering over Philadelphia. It's 10 segments, 116mm each.
That's very similar to my current arrangement. I packaged the antenna in PVC plumbing for when I eventually mount it outside. Also my RPi, RTL-SDR dongle and RF preamp are in the attic right next to the antenna to keep the RF cabling shorter. Speaking of mounting outside, I recently bought an old 25' antenna tower for $60 off Craigslist. I may move the ADSB antenna there or on a chimney mount.
Since that picture I did remove the connectors and ran the coax right into the segments of the collinear, and removed about 8 feet of extra coax while doing that, didn't improve range but I'm seeing more signals from low flying aircraft. I don't have any outlets in the attic, and it gets crazy hot up there June-September, the Pi would probably do OK but I'm not sure about the flightaware pro plus SDR, that thing gets pretty warm in a normal temperature room. I've thought about ways to mount the Pi/SDR/antenna on a pole in the back yard, problem is always getting power out to it. The previous owners paved a large parking area that covers almost the entire back side of the house, so I can't dig a trench to run a wire out to a box on a pole. And I'm not good up high on a ladder, I don't mind heights except when I'm up on a ladder, so I'm going to be sticking with what I can do in the attic. I have also thought about a second identical antenna at the other end of the attic, I have a normal SDR I can test with to see if a second feed would add much to what I'm seeing now. I do want to run a second coax up there for a scanner antenna, so when I do that I will probably build another collinear to do that test.
The heat worried me last summer but everything continued to run apparently without a problem. For power surely you can tap into one of the circuits that always are routed through there and put in an outlet. Or if there's a pull chain light upgrade the fixture to one with an integrated outlet.
I have tried a few new designs over the last 6 months but always went back to the one I posted, until now... I got some 1/2 inch aluminum tubing for a different antenna design but that one fell slightly short of the coax colinear, so I cut 1/2 wave lengths and designed a spacer to 3D print that would take copper wire and feed it down the center of one section and connect it to the next tube. It works amazing, increased my range about 50 miles, I can also now pick up some aircraft on the ground at KPHL. If this was outside on a pole it would really rock... Picture of it in the attic: CAD image of the spacer: Someone on another forum asked about the spacer so I made a quick diagram of how it works:
It should be small enough to upload here, so I'll try attaching it. I did find that I should have put a bit more space between the angled hole for the wire and the tube it's supposed to be insulated from, after pushing everything together sometimes the edge of the tube would bite into the plastic enough to touch the wire. I ended up using a soldering iron to melt a little bit of plastic down from the center ring to prevent this from happening. It will probably depend on the printer settings if this issue happens or not, I printed these pretty coursely, 0.25mm layers, finer layers would probably put more plastic in the thin area. .stl is not a supported file type so I zipped it.
I'll give it a try. I'm printing at 0.48mm on a 0.6 nozzle! I was printing 0.8mm on a 1.2mm - it was hard to get the case screw holes to print well
With that large a nozzle the oversquish might be too much for the small holes. But it's easy to clean them out with a drill bit. I've got the standard .4mm nozzle on my printer. I do normally print with thinner layers but since it gets hot in the attic I went with PETG, and I haven't had much luck printing that with layers less than .2mm. Just occurred to me I haven't rebuilt my printer in several years now, for a while I was building a new version every year, finally got it working so well I haven't had a reason to mess with it. It's a frankenprinter, cobbled together from parts of several printer kits and a few purpose bought items.
Hi, Some awesome stuff going on here, I wrote in one of the other threads that I was building another antenna and the one I am making is the same as the one MartyS has made, I think it's a half wave, is it? (shows what a numpty I am) Recently I read (also in another thread) about one that abcd4567 had built based on the Franklin design so am going to have a go at that one as well. The other one is finished and just needs to go in a pole and up on the roof but I am very impressed by the Franklin model and will build that one for the roof, use the other in the loft and compare the two. If neither work very well (which I doubt) at least it's cleared up my work area a bit, using the odds and sods (sorry am I allowed to say that?) Speaking of abdc4567's design, if you read this any chance you could post a picture or a rough drawing of the connection point? Cheers Colin
Yes, both the coax and aluminum tube antennas I made are 1/2 wave segments, the aluminum tubes are a bit longer because of less correction (basically signals slow down in different conductors but the frequency stays the same so the wavelength gets shorter). I think I used 0.85x for the braided coax and 0.97x for the aluminum.
Good morning, I've attached a picture of what I have done so far, the Franklin is from my old scanning antenna and the wire is 1.5mm power cable and I also have done two half wave, one with 1.5 antenna cable (centre core) and one from 2.5 from low loss antenna cable. The horizontal 10" bar, well 11" in this case is from the weight of a roller blind (I never throw anything away) this one is going on the roof the other two I will try out in my play room (that's what the Wife calls it) and run some comparisons. The Franklin is on the gable end of a bungalow (so not too high) should it need any repairs or alterations, I will try it at ground level at first and move the wires if necessary. I'll post some pictures of the polar diagram when up and running, at the moment I am uploading with a stock antenna at the very top of the apex in the loft mounted by its magnet on a baking tin (nothing is safe in this house). Thanks for your idea's guys. Cheers for now. Colin
Hi, good morning, I have now upgraded my original Franklin design (now called the "Tumbo design") it being my nickname, I have gone to the larger size wire from a very low loss antenna cable, also not that easy to manage, it being to the top end of the cable range mentioned 10 - 14 (2.59mm) gauge I think, I have also placed 5 mm plastic box section between the 67 mm legs (more for stability than anything, we do get some nasty winds here sometimes) used cable ties and hot glue gun for extra stability and insulating bare wires. So far: Yesterday 05/06/20. 1. At present it is only leaning against a window in my playroom. 2. Connected directly to a Nooelec dongle with a stock antenna cut to 67 mm (I've found that it needs at least 5 - 10 mins. before it has any effect) 0 a/c. 3. Just as a matter of interest I connected through a Nooelec "Ham it up" box, after a while it crept up to 6 a/c. 4. Tried 2. again and nothing. 5. Connected the Tumbo and nothing. 6. Checked all connections and all seemed fine but still 0 a/c. 7. Rebooted the pi which also rebooted the dump1090, nothing but after about an hour 6 a/c including a NATO AWACS. 8. My up-loader pi on a stock (not cut to size) in the loft is bouncing around 20 a/c up to 150 nm. 9. At this moment in time the Tumbo is leaning against the window and I just walked out the room and came back and 5 a/c were showing, now I've sat down it's gone down to 2 a/c. Conclusions: Humans don't conduct radio signals very well, in fact they interfere with them, so far not very impressed with the performance of the new antenna (checked and double checked all connections) at low level I am expecting better things when it is roof mounted. The weekend is not a good time for a/c for me, my scanners are on and nothing, my loft pi is showing 5 a/c at the moment, my experimental pi has just jumped to 3 a/c. Sorry if I'm boring you but I think that not enough people, especially those just starting up, share their experiences as they go along, it would save others asking questions and make it easier for them. So I say thanks to MartyS and abcd4567 and all the others I have not seen yet, keep em coming. Regards. Colin
Hi, I sent the email below to another thread about the Franklin antenna, this one seems to have got split up, so here it is here as well (probably my fault) Take care. Regards "Hi, Firstly I would like to offer my condolences to the Friends and Family of the USAF Air Force Pilot lost today. Not a nice way to start a message but life goes on, people keep telling me anyway, tell that to his Wife and kids. I have a short update on my roof antenna and am now considering it finished and ready to go out on the roof, I have spent the last few days tuning the antenna (that's building a antenna talk for sliding the the cable wires up and down the antenna wire a couple of mm's at a time before soldering them into position). I have had a few problems one being having too many plugins on the Pi and having it's voltage starved, I cured that with a powered USB hub. I was surprised in the effect it had on the signals being received, or not as the case may be. At best with the antenna leaning against my window was about 10 - 15 a/c, I moved it outside onto the front path and the signals shot up to around 30 (the most I received for weeks), outstripping the loft antenna that I use for uploading by almost twice as many. I'm open to any questions (as long as they are not too technical). I would also like to thank MartyS and abcd4567 for their original mails without which this one wouldn't have been made and am now looking forward to it being on the roof. Regards. Colin"
The hot weather this summer was causing some disconnects in my aluminum tube antenna, finally got around to buying some copper tubing so I could solder the sections together instead of friction fit of the aluminum tube design. I drilled holes in the sections of copper tubing and 3D printed new spacers sized for this tubing. Didn't want to melt the spacers trying to solder so I used a torch to put a blob of solder near each hole before putting the spacers in. Then it was a matter of soldering the wire to one side, putting it through to the next section, pulling it tight and soldering that end. I put a 100 ohm resister at the top as a check, it's easy to tell when you have a short between the center wires and a section of tubing but an open segment reads the same as a normal antenna, with the resistor if I get 100 ohms down at the connector for the flightaware pro stick I know all the connections are good. The solder joints are somewhat "cold", so not super strong, some of my blobs of solder on the copper tubing were not big enough to get a good melt without heating the tubing too much, tested each with pliers and did have to redo a few of them that popped off, time will tell if they stay bonded. Not seeing much difference between this and when the aluminum tube version was working well, hopefully this will keep working without having to mess with it anymore.
Hello MartyS, Nice work, looks very professional, copper I think is a much better medium for antennae than ally, I always get the impression that being a lighter metal and some would argue softer you get a lot of movement which would have put a lot of stress on your joints, copper being a stiffer medium would maybe not move so much (I wouldn't want to build an airplane with it though). Do you have any screws through the copper into the spacers? or even a small bolt and nut all the way through? Expansion and contraction has been a problem with any metal for, well, since it was first used I guess. I have a antenna that is actually for an aircraft only about 70mm long, keep meaning to try it, I guess with that one the whole aircraft would be part of the antenna, couldn't figure out why they have fibre washers insulating it from the a/c's body until I got into it as a hobby. My home made job is still plodding along and giving good results, well, as good as our present situation will allow but there was a time a few weeks back the count went up nearly back to normal. I have you and abcd4567 to thank for tempting me into making my own antenna, it's on the roof now and like I say still going strong. I'm looking now to expand on my local a/c, it seems I have a weak spot there, anything for the first 25nm doesn't seem to register, I see them but not on the map, I can hear already, maybe they are not ADS-B equipped, I've already taken that into consideration. Thought of combining two antennae and merging the signal into one for the upload but again that is on the to do list. Just as a last thought have you considered what your gain would be like if your antenna was out in the open on your roof? might be worth considering. I did think of improving it but hey "if it ain't broke don't fix it". Great work Marty and thanks again.
Since there are 2 wires going through the spacers that need to remain insulated from each other, there's no good place to put a fastener. But that does give me an idea for making the aluminum one more reliable, I could drill and tap some holes in the aliminum over the place in the spacer with the copper wire and screw in some tiny machine screws to put pressure and make better contact. Still might have issues, PETG is fairly temperature resistant but I've had 3D printed stuff deform if left in a hot car, especially if there is pressure applied. If I was making it for outdoor use that would be hard to access I'd get plastic rod and use a lathe and drill press to make the spacers. I would love to put this outside but I hate being on a ladder more than about 10 feet off the ground, I would need about 25 feet to reach the peak of my house, and it's got a steep roof so even more uncomfortable if I tried to walk up there from the side. Considering I'm getting 150 mile range with it in the attic I figure it would have tremendous range outside, but that's just not going to happen.
I, see where you are coming from, I'm not so keen on ladders myself but then we live in a Bungalow but I still get the shakes until I've been up there for a little while, the apex is still quite high, it always seems worse up there looking down than it does down on the ground looking up. I am assuming here that at least one end of your home is clear, would it be possible to fix a mast to the gable end of the house? a few tough saddle clamps and bolted on rather than screws and raw plugs (I'm sure that should be rawlplugs but the computer won't let me correct it). You would probably have to purchase a scaffold pole or two and weld them together, you sound like the Engineering type having access to lathe's etc. and you only need to just clear your roof line. Just the ramblings of an old man but you convinced me to make my own antenna and I chose to put it on the roof and am glad I did (listening to my scanner while doing this and just heard that a Hostile a/c has broken into our air space, yesterday a pilot transmitted Mayday, Mayday, Mayday, I think he was diverted to Norwich, which is about an hour from me) getting busy. Back to the antenna just think of the benefits, you may need a mate or two to give you a hand to get the pole up though. Cheers. C
Wow, I've not heard anything that interesting live with my scanner. There was one time a private jet took off and declared an emergency with their landing gear, they flew in a big octagon around Philly International for a while, then did 2 low passes over 2 of the runways so people on the ground could take a look, then they landed and everything was fine. I have thought about various ways to get the antenna outside but they all have issues I don't want to deal with, so in the attic it will stay. Maybe someday I'll build a weather proof setup to put in the back yard on a pole, getting power to it would not be easy. It took a few tries just to put the Raspberry Pi in a closet, wasn't expecting the voltage drop I got using various wire to get power to the thing, ended up needing 14 gauge wire to go 20 feet. But getting the Pi closer to the antenna and removing 20 feet of coax did get me more signal.
