Hi all,
Very new to ADSB and have been reading for several weeks now and want to build an antenna to improve the range over my spider antenna on a stick in the living room. I’ve been an advanced ham for over 40 years and have made lots of different antennas over the years but after reading many posts on this forum I see the most used coax for feeders is RG-6, a 75 ohm coax. Not sure about other SDR radios but my RTL-SDR V4 is 50 ohm input, and most commercial and homebrew antenna designs are geared toward 50 ohm match. I’m just wondering why so many use RG-6, is it because it’s cheap, readily available, low loss, easy to terminate, all of the above? I’m not seeing a lot of effort to match to a 50 ohm RX input, but I suppose since we aren’t transmitting there is no need to worry about amp finals. I have everything from RG-174 up to LDF-5.
Now my second question, overall, what is the most common DIY antenna these days? I have made it thru about 24 pages of the epic 189 page antenna thread on the planefinder forum and I am unable to come to a conclusion so far. @Abcd567 did a TON of work back then and really did a great job of showing us the variety of designs but after 24 pages…is there a clear winner? I’ll continue reading the thread but would like to get something up this week. Franklin, coax or other collinear, pop can 1/4W, or ??? Heywhat’sthat doesn’t look too promising for my location, see attached, I used antenna at 20’ above gnd.
I have all the materials to build any of the designs mentioned, after 40 years of hamming and 15 years as broadcast engineer and having 20 acres of storage, there’s not much I need radio wise.
Cheers and thanks everyone.
For ADSB frquency of 1090 MHz, the wavelength is much shorter than those for Amature Radio. As a result tolerances are in mm. A even 1 or 2 mm error in dimensions of a wire collinear or coaxial collinear antenna can result in a poor antenna, even though the design is good. The only antenna which is naturally tuned and substantially intollerent to dimensional errors is 1/4 wavelength ground plane (spider, cantenna etc), but their disadvantage is low gain.
I have tried several designs of DIY antenna, and finally come to conclusion that the best option is to buy a commercial antenna.
In addition to DIY antennas, I am using Flightaware antenna which I purchased about 8 years ago. It is good, but now they dont ship outside USA.
Another very good antenna is Vinnant. I have not used it, but many members in this forum have used it’s different models. I hope they will jump in and give their opinion.
Looks like you have heavy obstacles to the west. Don’t expect too much from a better antenna.
I have tested several (including Jetvision A3 and Vinnant 9 dBi). most deliver the same performance based on the environment. I wouldn’t rate one better than the other
Amateur frequencies in Australia go considerably higher than 1090MHz
My licence tops out at 241 GHz but I admit to not having used that band but I have sat on a mountain top supporting others trying to break the 10GHz distance record.
Spectrum for amateur radio
International and domestic allocation of
spectrum, including allocations for the amateur
service, is set out in the ACMA’s Australian
Radiofrequency Spectrum Plan.
The ACMA supports amateur use in a variety
of bands, across 135 kHz, 472 kHz, 1.8 MHz,
3.5 MHz, 3.8 MHz, 7 MHz, 10 MHz, 14 MHz,
18 MHz, 21 MHz, 24 MHz, 28 MHz, 52 MHz,
144 MHz, 430 MHz, 1240 MHz, 2300 MHz,
2400 MHz, 3. 3 GHz, 3.4 GHz, 5.6 GHz,
10 GHz, 24 GHz, 47 GHz, 76 GHz 122 GHz,
134 GHz and 241 GHz.
Access to these bands can depend on
your licence, location, emission mode and
other factors.
And then there are the Radio Amateur that go above the radio frequencies to the light frequencies at 475 THz [630nm]
More information is available from Radio and Electronics Association of Southern Tasmania Inc..
S.
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Speaking of antenna’s I am (hopefully) putting up a new pole for a AIS aerial. Was wondering if it was worth upgrading to a new 1090 aerial at the same time to replace my FlightAware aerial 5.5db that I have had for about 8 years. I was thinking of the Vinnant 8-P, and know Keith upgraded to it a few years back, and saw an improvement, but he did raise the height at the same time. Anyone else made the jump from the FlightAware one to something else, an improved stats.
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Yep - for all the reasons you list. “most” RTL dongles are sold for TV/DAB reception, so have 75Ω connectors.
For a receiver-only setup, the loss due to missmatch can be easily compensated for.
As you are starting with a V4, you may as well run 50Ω all the way.
Given 1090MHz is very much ‘line of sight’, meaning your location is quite “terrain limited”, so a big antenna and lots of amp gain isn’t going to help you much.
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I have both the FA 5.5 dB and the Vinnant 8 dB antenna. when I changed it (at the same height) I get a better number of positions but a very minimal increase on aircraft count.
This is due to the fact that the maximum number of aircraft is already received, the number of distant signals is improved on the Vinnant 8P in comparison to the FA 5.5 dB antenna.
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Thank you for providing info for GHz bands added to Amateur use.
This addition is fairly recent. For a very long time the Amateur band was limited to HF (30 MHz & less), then 4 meter and 2 meter were added. My statement was about these long standing frequencies.
Not too recent 
The 1927 International Radiotelegraph Conference (Washington) contained Amateur allocations up to 6GHz
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A bit off topic, but I could not resist. You may be disappointed in what the range outline shows, but tilt your head to the right and a maple leaf pattern appears. Kind of matches the Highway 1 icons on your map. Quite appropriate for a site in Canada!
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When I was first licenced, I had the restriction I was not allowed to operate below 30MHz
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Ok, 6 GHz was allocated in 1927, but since when this extended band became popular and is in general use by Amatueur Radio Operators?
The first QSO on 10GHz was between W2RJM and W2JN in 1946.
10GHz has been “in general use” ever since.
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What % of Amature Radio Operators were using 10 GH during last century? You cannot call it “general use” if only a very small % of Amature Radio Operators were using it. Also was such high frequency Tx Rx equipment was available at affordable cost during last century?
6 GHz & 10 GHz may have gained popularity during current century.
Well you are right that most Amateur Radio is at HF or below. Originally (in 1920’s era} any frequency above HF was considered “useless”. So hams were also originally allowed unrestricted use of any frequency above some value – forget what it was.
Of course hams also use relay systems in the 450 MHz (70 cm) a lot these days. And there is AMSAT in the UHF frequency range.
Edit to add: I happen to have a 1959 Radio Amateur’s Handbook from when I was a ham in high school. At that time hams could use anything above 30 GHz unrestricted.
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23cm (1296MHz) I would say started to become quite widely used in the UK from the early 1980s when commercial transverters and kits became more easily available.
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Yes, by the 80’s the big three all had off-the-shelf (applience) radios that were availible to anyone not wanting to roll their own.
ABC, You made a statement that was completly wrong. Accept it and move on. It’s off topic and not adding to the discussion.
I have already clarified as follows:
Even after my above clarification, you guys did not stop and have lingered on with this off-topic issue. I agree to your suggested to focus on OP’s questions.
Hi guys,
Thanks for all the lively discussion, lots to absorb…
I’m mostly surprised at the recommendation of abcd567 to buy commercial antennas after almost 5 years of experimenting with DIY antennas with amazing results. I’m still a DIYer at heart and will never buy something that I can build from materials at hand.
So today I built a quick n dirty cantenna, tuned it, and tomorrow I’m going to mount it to the eve with an old Bell satellite mount and a 4’ piece of 1" PVC. I made up my own coax with 12’ of RG-400 and terminated one end with BNC, the other with SMA, and here are a few pics of the antenna and result on the VNA. I used a BNC chassis mount connector for the base and soldered a piece of the center conductor from the RG-400, it’s steel with copper then silver plating on top, nice stuff. RG-400 is awesome as well, dual braid, all silver plated copper, teflon core insulation and a solid center conductor as described.
As for the ham band discussion, there has never been a 4M band, as far as I know, in North America we have 160, 80, 40, 30, 17, 20, 10, 12, 6, 2, 1.25, 70cm, 33cm, 23cm and above that I don’t know, each country has its own band plan…I don’t know them all but they go WAY up in freq, antennas the size of paper clips. If I’m too old to see the antenna, I shouldn’t be working those frequencies.
Cheers 
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