Building a simple NOAA APT Antenna out of an Umbrella
In order to optimally receive NOAA weather satellite images a special satellite antenna tuned for 137 MHz should to be built. Generally either a QFH or turnstile antenna is recommended as these receive signals coming from the sky very well. If you are interested in receiving weather satellite images from NOAA satellites with an RTL-SDR dongle then we have a tutorial available here.
While QFH and turnstile antennas are not difficult or expensive to build, they still do require a small amount of electrical and construction skills. Over on YouTube user Wanderlinse shows us a possible alternative NOAA antenna that is simply made out of an old umbrella (the video is narrated in German, but it is easy to understand from the visuals). He uses a short BNC cable with crocodile clips, and connects one clip to the spines of the umbrella, and the other to the central metal shaft. For some reason this seems to create a good antenna that receives NOAA APT signals very well. To prevent wind issues he also cuts out some holes in the umbrella fabric.
Wanderlinse also shows that he can receive other signals with this umbrella antenna too, such as long wave, medium wave, shortwave, aircraft radio and ham radio.
This is just yet another proof that pretty much any metallic contraption can be used as an antenna on some frequency. The umbrella”s dimensions seem to lean themselves to FM and 137 MHz usage BUT that doesn’t make this a good antenna specifically for WX sats or anything else – any piece of wire in the proper length will yield very similar results on the roof top, more so with a ground plane. So I’d say this is bogus news from a hobby experimenter with very understanding neighbors and little understanding of antennas.
OMG he needs 5 minutes to open the umbrella and to explain what to connect where and fail at it. :/
I’ve seen other comparison videos from this guy when trying to find info about the LA-400 magloop. Some random SWL without deeper knowledge of anything. The way……………………he talks………………..is………………..really……………….annoying, he needs ages to get to the point (if he has one that is, which is rare).
Read this before talking like you think you are an expert, because you are not.
http://www.qsl.net/k4mg/Antenna%20Design%20the%20Easy%20Way.htm
Final update on this:
I was not able to get much luck with either a 68 degree or 53 degree NOAA 19 pass. I was able to see the signal in the waterfall and heard the “bing-bong-bing-bong” noise but there was too much noise to get a useful image.
I tried re-wiring so that it would be more like the example, but that did not make an impact.
This may be dependent on using a slightly longer umbrella, being in an RF-quiet neighborhood, or having a clear view of the horizon, which unfortunately, I do not have.
I am going to try building a lindenblad here in the next few days and will compare. To be sure, My plan is to swing the antenna about five feet away from the balcony railing using PVC as a horizontal mast… just by itself that should improve signal quality.
I think this is some kind of early april fools joke. I just wasted 30 minutes of my valuable remaining lifetime to prepare an umbrella and put it out to test the concept and to not miss out on something potentially awesome. As expected, it was considerably worse than the little homebrew groundplane contraption I use (with great results) for FM and also 137MHz NOAA sat reception, actually worse than some random piece of wire I stuck into a luster terminal. Like I said above, you can put pretty much anything on a roof and receive something with it, that doesn’t mean it’s good though. The video just tells us that the other antenna he compares it with is even crappier than that. The only thing the video proves is that any random jerk can post videos with any crap content and be sure that it will reverbate through the content-hungry blogosphere forever.
I also made a short video listening to a semi-local (about 20 miles away) 2-meter propagation beacon. I made an effort to catch the 4 am pass of NOAA 19 but I goofed my setup with rtl_tcp and listened to my other dongle, which I have connected to the second IF on my Icom 703 (so yeah, no APT signal on 137Mhz). I have fixed my setup and have set WXtoImg to record the next pass at 7 am. But I must be off to sleep now as I have work in 5 hours.
https://www.youtube.com/watch?v=xdN58WQFGXo
I did a little basic testing with an old umbrella I had and my Baofeng HT.
I don’t know the make/model but I believe I bought this at Walgreens, CVS or Wal-Mart a few years ago. It is one of the collapsible models that people get and put in their handbags, purses, backpacks etc. The center shaft is approximately 19 or 20 inches long (not sure how far the metal extends into the handle, which is a couple of inches long, but there is approx. 19 inches from the top to the handle). The spines are also approx. 19 inches long. This is just about the right length for a quarter-wave antenna on the amateur 2-meter band (using the traditional 234/f rule of thumb, 146 Mhz = 19.2 inches). As such, it is probably also a decent receive antenna on the 137 Mhz APT band.
As far as testing goes:
First, I measured to verify that the spines and the shaft are electrically isolated, using a multimeter in continuity test mode. They are. This makes sense, given that the spines attach to plastic hubs that slide up and down the main umbrella shaft.
Second, I then scrounged up an SO-239 female chassis connector and attached about four inches of 14 gauge speaker wire to both the center and to one of the screw-holes for ground. I then attached alligator clips to each wire. I used nylon wire ties to carefully mount this in the umbrella spines, without the connector itself touching any of the spines (which could cause a short depending on how I connect the clips).
Third, I connected a 10-foot length of RG-8X from Radio Shack (with the PL-239/UHF male connectors). I used a UHF-to-SMA adapter on the transceiver end, as well as a female-to-female SMA adapter to work with the Baofeng (which has an SMA male connector for RF out).
I was able to listen to local NOAA weather radio station; I heard some APRS traffic on 144.39 MHz, and I was able to hit a few repeaters in the area on both 2 meters and 70 cm. I didn’t hear anyone else up this late, though, so I didn’t get any signal reports.
By means of rough comparison (based on the signal quality of the “roger beeps” from the repeaters), I think this quick-and-dirty umbrella antenna was slightly better than the stock rubber-ducky that ships with the Baofeng UV5R (which is notoriously bad). I’d obviously have to do more testing to confirm and/or quantify that.
I also didn’t do any real tuning. Results might get better if you used a specific kind of umbrella or carefully tuned it. Furthermore, I was inside, which can cause all kinds of interesting problems. Although I am in a third-floor apartment this would probably get better results if I were outdoors or on the roof.
I played around with several different tap locations for both the center and shield/ground wires. I found the best outcome is when I put the shield clip on the spine (near the center) and when I attached the center clip to the shaft, at the very top of the umbrella. YMMV.
My best guess is that this is acting, essentially, as an inverted monopole. You might get better reception if you bend the spines up (you know, what happens when an umbrella gets “blown out” during a heavy wind). That definitely should change the feed-point impedance.
All-in-all this seems to be at least a decent “emergency” antenna design for hams. And it is very plausible to me that Wanderlinse is getting good results (notwithstanding the proof he’s already shown us).
I also found a few images on the Internet of people using umbrellas as antennas (apparently non-ironically). There is also a type of antenna that is used at HF and lower called an “umbrella antenna”. It is not made up of real umbrellas, but it does sort of look like a giant umbrella, with many wires sprawling out from a central tower. I don’t think many hams use these any more because they appear to take up a lot of real estate. But there is a Wikipedia article on it: https://en.wikipedia.org/wiki/Umbrella_antenna
I put together a few pictures of my experimental setup and shared them on imgur, at the links below:
http://imgur.com/GQYrat7
http://imgur.com/enbc0xc
http://imgur.com/UQmpBAC
I’m with AD5NL, he inadvertently made a discone. This actually gives me a little hope, because I intended to mount a proper discone on my roof, and feed my scanner and SDR dongles with it. If he’s getting quality signals this way, then a quality discone will get good enough results as well.
It seems to me that if the spines and the central boom are electrically isolated from one another, then you have essentially got a vertical antenna with radials on top.
Also seems possible that this might be acting like a discone antenna.
Would need to study it a bit more.
Also curious to see if this works for some antenna sizes but not others. Tempted to go over to WalMart and buy some different sized umbrellas to test… I’ll put that on my ever-growing list of weekend projects. 🙂