Raspberry Pi type B + DVB-T Dongle to feed FR24

[peterhr]

The (long) elements that actually do the work go vertical - the loops are just there as a 1/2 wave signal delay and can be curled up (that's the way I read it anyway).

Home depot do a kit with 1/4" copper pipe for connecting up water coolers (pity we cant get it here) that might be a good material to use fo antennas - you'd need a bending tool to stop it forming kinks ($11.25). If I remember correctly to soften copper heat it slowly to red hot the quench it quickly in a cold water bath. Apparently 1/4" pipe can be bent to a 3/4" radius if the tooling allows.

[speedbird1960]

The (long) elements that actually do the work go vertical - the loops are just there as a 1/2 wave signal delay and can be curled up (that's the way I read it anyway).

Home depot do a kit with 1/4" copper pipe for connecting up water coolers (pity we cant get it here) that might be a good material to use fo antennas - you'd need a bending tool to stop it forming kinks ($11.25). If I remember correctly to soften copper heat it slowly to red hot the quench it quickly in a cold water bath. Apparently 1/4" pipe can be bent to a 3/4" radius if the tooling allows.

A little Plumbers Tip, fill the copper pipe with sand before bending as it reduces the chances of kinking it.

[andyk1]

A little Plumbers Tip, fill the copper pipe with sand before bending as it reduces the chances of kinking it.

How about solid rods... say 1/8" or 3 mm thick I think. soldered to coax? Or even semi-rigid copper wiring you see ham operators making antenna's out of?

[andyk1]

The (long) elements that actually do the work go vertical - the loops are just there as a 1/2 wave signal delay and can be curled up (that's the way I read it anyway).

Home depot do a kit with 1/4" copper pipe for connecting up water coolers (pity we cant get it here) that might be a good material to use fo antennas - you'd need a bending tool to stop it forming kinks ($11.25). If I remember correctly to soften copper heat it slowly to red hot the quench it quickly in a cold water bath. Apparently 1/4" pipe can be bent to a 3/4" radius if the tooling allows.

I thought of that but the bends seem more than I think I could handle. Does it matter how far the bends are apart ya think? Maybe ABCD... or speedbird1960 would know.

[peterhr]

... yes - or the antenna performance would be poor - but the kit has maybe 5 times as much pipe as you need.

Perhaps 3/16 copper wire would be better

[andyk1]

I've been reading lately adding a saw filter to the dongle. I saw pic's of the 1090mhz saw filter but can't find any pictures, diagrams or directions where they go on the dongles with one installed. Any clue? ANYBODY? Cost approx. $10 us dollars for the saw filter.

http://www.ebay.com/itm/B1602-SAW-filters-Epcos-1090MHz-ADS-B-AirNav-SBS-/110619017914

[speedbird1960]

I've been reading lately adding a saw filter to the dongle. I saw pic's of the 1090mhz saw filter but can't find any pictures, diagrams or directions where they go on the dongles with one installed. Any clue? ANYBODY? Cost approx. $10 us dollars for the saw filter.

http://www.ebay.com/itm/B1602-SAW-fi...-/110619017914

I have checked the PDF file from the EBAY page and the Datasheet is dated 2003.

I have checked the manufacturers Website and that product has been discontinued: http://www.epcos.com/web/generator/W...?M_QUERY=B1602

This is their current stock list: http://www.epcos.com/web/generator/W...locale=en.html

[andyk1]

... yes - or the antenna performance would be poor - but the kit has maybe 5 times as much pipe as you need.

Perhaps 3/16 copper wire would be better

I've been reading a lot about that. Seems the 3/16 copper pipe is the best bet. Can even be flattened out if needed with no ill effects. The problem I have been reading about is that setting the swr or vswr on the ground will not be the same once it is 15 meters in the air. Just about need a high rise bucket to set it and that's somewhat out of the question for people like us.

Starting to get more complicated the better I try and make this work better.

Built a new collinear antenna. 8 segment, no 50 or 75 ohm resister at the top needed using 75 ohm RG6 Good quality (Didn't have access to or willing to wait for RG8 in the mail) cable with a television rated amplifier (outdoor mounted antenna not cable or satellite) mounted just below the antenna by type F connector and feed 12 volts (My power injector power supply says 15 volts 1 amp ) just before the sdr dongle and an FM filter mounted just after the power injector I now get out to almost 400 km in some directions. 25 to 50km better than my last build. Segments where all cut to exactly 116 mm with a 1" (26mm) over lap on both ends. Put together very carefully and only used 2 turns of electrical tape between segments all mounted inside a 3/4" (6-7 mm) fiberglass tube about 4 1/2 feet (135 cm approximate) the extra length was used to mount onto the mast. It seems the fiber glass tubing verse PVC made a difference. The freq drop out is still there using SDRShape.exe but now it is 1089.969.133mhz instead of 1089.930.000mhz using electrical grade PVC.

I am now almost certain an FM Trap filter helps if inserted after the 12 volt power injection and not before it.

Anyway just thought I'd share. Only getting out 37 km average better as I said but every click matter I suppose.

If your building this yourself and have to hoist a 15 meter antenna it would be wise to take your time and built the antenna slowly and accurately.

Will tackle another antenna when I get time using 3/8" copper pipe outside of any weather protection i.e. PVC or fiber glass tube. The franklin seems nice but a bit tricky for my experience level building antenna's. J-pole antenna didn't work at all for me but more than likely it was me instead of the antenna.

I'd post a screen grab of adsbSCOPE to show the difference now but having trouble uploading it here. File may be to big. 2.1 mb

Made a mistake "3/4" (6-7 mm)" meant to say 16-17 mm

[Jayant]

Built a new collinear antenna. 8 segment, no 50 or 75 ohm resister at the top needed using 75 ohm RG6 Good quality (Didn't have access to or willing to wait for RG8 in the mail) cable with a television rated amplifier (outdoor mounted antenna not cable or satellite) mounted just below the antenna by type F connector and feed 12 volts (My power injector power supply says 15 volts 1 amp ) just before the sdr dongle and an FM filter mounted just after the power injector I now get out to almost 400 km in some directions. 25 to 50km better than my last build. Segments where all cut to exactly 116 mm with a 1" (26mm) over lap on both ends. Put together very carefully and only used 2 turns of electrical tape between segments all mounted inside a 3/4" (6-7 mm) fiberglass tube about 4 1/2 feet (135 cm approximate) the extra length was used to mount onto the mast. It seems the fiber glass tubing verse PVC made a difference. The freq drop out is still there using SDRShape.exe but now it is 1089.969.133mhz instead of 1089.930.000mhz using electrical grade PVC.

Hi Andy,

I'm curious about the 116 mm element length. That would suggest a velocity factor of .84 or so. I assume you're using foam dielectric cable. I'm not even sure of the velocity factor of the cable we get locally in in India, considering it is mostly Chinese made cable. From what I can gather, it varies between .66 for PE dielectric to around .82 for foam. That would change the element length from 91 mm (PE cable) to around 112 for foam cable. I'm not sure how much a difference in actual length would make in terms of performance. You've obviously hit the right length, I'm just curious how you figured out the 116 mm lenght and if you've experimented with other element lengths, a few mm here or there. Also, did you leave a 1/4 wave bit on top of the first element?

Just got hold of some RG-6 cable, so was setting out to build a co-ax collinear for myself.

[peterhr]

I guessed that mine was .84 - I have no way of measuring it, The end was just open ended ... now resister or 1/4 wave whip.

The next one I'm going to have a go at is the franklin made out of 3/16" copper tube (car brake pipe) - with no velocity factor involved.

[andyk1]

Hi Andy,

I'm curious about the 116 mm element length. That would suggest a velocity factor of .84 or so. I assume you're using foam dielectric cable. I'm not even sure of the velocity factor of the cable we get locally in in India, considering it is mostly Chinese made cable. From what I can gather, it varies between .66 for PE dielectric to around .82 for foam. That would change the element length from 91 mm (PE cable) to around 112 for foam cable. I'm not sure how much a difference in actual length would make in terms of performance. You've obviously hit the right length, I'm just curious how you figured out the 116 mm lenght and if you've experimented with other element lengths, a few mm here or there. Also, did you leave a 1/4 wave bit on top of the first element?

Just got hold of some RG-6 cable, so was setting out to build a co-ax collinear for myself.

I don't know what my cables velocity factor is and guessed that good quality cable is rated around .85 so that is what I used. I used the formula from one of the antenna sites and came up with the 116mm. For the top element I just cut another 116 mm length + 1" in cut the plastic wrap and shielding off leaving the center wire and insulation intact. Stripped the copper wire bare with a good knife (Which I forgot to mention earlier) Inserted that into the shielding on the top element and soldered down the side just a tad for a 1/4 wave length. I was assuming at the 116 mm lengths where 1/4 wave each. No 50 or 75 ohm resister needed as I read if your cable is already 75 ohm it's not needed. With an amplifier added you can't use a matching resister as it will short it out. Whatever the case. With a mast head amplifier, power injection just above the dongle and am FM trap I have amazing reception and distance coverage. Better than the F- feeders. This screen capture was just now and I have had up to 16,990 frames per min yesterday.

Adsbscope4.jpg

[andyk1]

I guessed that mine was .84 - I have no way of measuring it, The end was just open ended ... now resister or 1/4 wave whip.

The next one I'm going to have a go at is the franklin made out of 3/16" copper tube (car brake pipe) - with no velocity factor involved.

Yes mine was only a guess also...(.85) velocity factor) It is the cable local cable company's use to lay new installations. Thicker than cheap china made store brought. very good looking, feel and not cheap made triple shielded.

Also scraped coating off center hard wire till it was shiny copper to remove the protective coating.

[andyk1]

Am also considering adding another 10 feet (3.3 meters) to my antenna height just to see if maybe I can get another few feet distance... Am at 45 feet high now so we'll see. I also read that adding height to an antenna doesn't improve it very much so I guess I'll test this and verify if that is true. At 55 feet It will be the tallest object for over 125 miles. My elevation is 1285 feet ASL (sea level) Amarillo, Texas (250 miles to my west) is at 8000+ ASL but at 35000 feet AGL, I should easily see them.

[andyk1]

One of my sdr dongles (I have 4 of them) errr had, failed last night during a very heavy thunder, rain storm (Midwest US... Figures). I am not sure why but I didn't have my static ground connected at the time. My guess is static in the air took out the tuner as it still is seen as a USB device just doesn't receive any radio signals. The Local F-feeder also went down in my area and am guessing he had the same problem. I noticed that the new F-feeder located in Dallas Texas was feeding aircraft for nearly 400 miles after the storm. He took over all feeds as everyone else went down. I thought that was amazing range and the antenna's FR is supplying must really be very, very good antenna's.

[andyk1]

I guessed that mine was .84 - I have no way of measuring it, The end was just open ended ... now resister or 1/4 wave whip.

The next one I'm going to have a go at is the franklin made out of 3/16" copper tube (car brake pipe) - with no velocity factor involved.

peterhr!!! can you please email mail when you get time. I should be getting my beaglebone black on Monday.... err tomorrow maybe. I'd like to try it also next to the Rpi just for the heck of it.


andykere(removethis)(at)Hotmail.com

Also. what do you think about the 3/8" copper pipe being flattened out to make it easier to bend and get the bends closer togather?

Wonder if you can use SDRSharp.exe (SDR#) to tune the right (1090mhz) frequency... SWR?

It's been a long time since I messed with HAM radio's (10-11 and 12 meter) and I can't remember. cutting just a bit off the end raises the freq right? Anybody answer if you know the right answer please.
no guesses... PLEASE