Corner Reflector Antenna test with Gotenna

[Jayborn]

Thought I would post this as it may assist others looking to increase the Gotenna range in a particular direction.

I decided to do a very quick test using a simple Corner Reflector antenna to see if I was able to extend the range of my Gotenna in a particular direction. Note this was as simple test just to see if the idea was worth exploring further. Total time to construct and test approximately 2 hrs.

Corner Reflector antenna was constructed using 16 x 36 Inch Joist Panning Lining from Home Depot $7.88 Cad (basically just a rectangle of sheet metal).

Sheet metal was folded in half to create a V with an approximate angle of 90 degrees and panels that would 16x18

Small sting was tied to Gotenna so that it would hang (top of black on Gotenna) at approx. 20cm from the bottom of the reflector. A piece of wood was used to suspend the Gotenna from the top of the V at approximately 18cm from the fold/vertex. The calcs online should this should have been around 16.6cm for 900mhz however after trying a number of measurements 18cm worked best for me.

For the below testing the Corner Reflector antenna was placed in the back of by SUV aiming out the back with the back hatch open.

Test 1

Reconfirm the max range to my paired 24/7 solar powered node (roof height/ Jayborn-1) using No reflector.

Result: 1.90km/1.18Mi with confirmation

Test 2

Confirm the max range to the same node using the Corner Reflector.

Result:4.93 Km/3.06 Mi with confirmation

Test 3

Confirm the max range to the same node using the Corner Reflector without confirmation

Result: 5.56 Km/3.45 Mi no confirmation

Notes: None of the above test messages flowed through a relay node. At least three test messages were successfully completed at each location. The Corner Reflector is very directional, that said a phone with simple mapping apps will be able to point you in the right direction very quickly.

I have included two pictures, 1) Corner Reflector antenna setup in SUV 2) Map of test.

Please note I am not a Radio/Ham guy therefore some my terminology/testing methods may be inaccurate or not be inline with what is normally expected with a radio/antenna test.

Hope this is of interest to some people. Any questions let me know.

[MikeL]

Excellent work! I love home-brew solutions like this that are simple/quick, cheap, and effective. The old saying is you can get 2 out of 3 and you should be happy with that. Here, I think you’ve managed all three.

[brunota2003]

Did you try from the 2 locations without the reflector, as well? Just to verify that it was indeed the reflector allowing the messages to go through, and not something like a rise in terrain or a better LOS than where you lost signal at 1.18 miles? That is a pretty impressive gain from such a simple solution!

[Jayborn]

Yes, before testing with the reflector at each location I tested the Gotenna without it to confirm I was out of range. I have tested the 24/7 node’s range quite a bit over the past month and realistically the 1.18 Mi range is the best I have obtained. Normally it is right around 1 Mile and in some directions slightly less. This makes sense looking at the map and the fact that there is considerable less housing etc… in that direction.

For the Green test 3.06 Miles i did an initial 3 messages with the reflector which all failed, i then readjusted my direction ( I was off by probably 10-15 degrees) and then the next 3 messages went right through and I received confirmations back.

Agreed the increase in range was quite surprising to me. Obviously its just a quick simple test as I didn’t have time to confirm various directions etc… therefore much more testing is needed to confirm these results weren’t just some sort of fluke.

Depending on my time this week/weekend I may be able to do a bit more testing. I also plan on creating a simple Cantenna to test out and see how that compares to this reflector.

[W6TUX]

@Jayborn

Agreed the increase in range was quite surprising to me. Obviously its just a quick simple test as I didn’t have time to confirm various directions etc… therefore much more testing is needed to confirm these results weren’t just some sort of fluke.

Depending on my time this week/weekend I may be able to do a bit more testing. I also plan on creating a simple Cantenna to test out and see how that compares to this reflector.

I really hope things worked out and you were able to do a bit more testing - have to say I found this post pretty inspiring and have been checking to see what our local Home Depot has available!

[Jayborn]

Glad to hear you found it interesting, I’ll definitely post and update once I have completed more testing. If you are going to try it out yourself the main thing to keep in mind is that each panel (side of V) must be at least one wavelength in size (~34cm or 13.5") both length and widith. Bigger is usually better when in comes to reflectors therefore going over my sheet metal measurements should be fine/better however going under will probably negatively impact the results.

[aspexin]

I have two solar powered mesh units (East and West facing) hanging from the rafters in the attic. After reading this thread I hung up a sheet of aluminum foil (using a length of twine stapled to the aluminum foil and hung over the same beam) behind each mesh unit and spaced about 6.5" back.

Of course, it has been raining here since I did this yesterday so I have not had a chance to go out and do any range testing. Seeing as I’m in an urban area I’m hoping this will help having a simple reflector behind the gotenna mesh units to eek out a little more distance.

[Jayborn]

Cool, let us know if if helps increase the range. Note there is definitely a sweet spot with regards to the fold/vertex to Gotenna distance and the tolerance I found is quite small say 1/2". After a bit of adjusting back and forth mine ended up being right around 7" (18cm) so you may need to adjust your 6.5" up or down a bit, I know I did.

[aspexin]

Yes, that is why I started at 6.5". I will play around with spacing. Would be nice if we could get some actual signal strength readings from the mesh units. That way I could go to the same spots and measure what if any gain was achieved. I’ll be watching your cantenna results.

[W6TUX]

Here is a pretty good link on corner reflectors:
http://www.microwavetools.com/corner_reflector/

(I’m fairly certain for our purposes, 1/2 wavelength from the fold is probably a minimum number, not surprised the OP found it worked best a little over that).

[aspexin]

I worked my way back up to 18cm between mesh and reflector. I get about another 200m distance. Again, this is a semi-dense urban area with lots of foliage. But I can now get to 910m distance from my attic. The best I could do before was 710m. This is also very directional as the units are pointed East and West so North/South does not get any gain from the reflectors as would be expected. I wonder if I built a multi-element yagi to hang behind the gotenna mesh would have any improvement since I’m directional anyhow?

[MikeL]

When I have questions about antennas, I usually turn to Joe Carr’s Receiving Antenna Handbook (HighText Publications, Solana Beach, CA, 1993, ISBN: 1-878707-07-8).

Carr hasn’t got a lot on Yagi’s but I came across across a helpful idea or two after confirming what little I remembered. A Yagi is what is generically called a parasitic beam antenna and what I was trying to recall was where it’s fed. That turns out to be from the driven element or in the middle of the Yagi. Behind it is a reflector and in front of it (in the direction you want to get max reception) is the director.

It suggests you’ll need to experimenter a bit, but offers these formulas as a good starting point for a 3-element antenna.

Driven element: L (in feet) = 475 divided by Freq (in MHz)
Director element: L (in feet) = 456 divided by Freq (in MHz)
Reflector element: L (in feet) = 500 divided by Freq (in MHz)

If needed, additional directors are sized to each be 4% shorter than the next outward from the director closest to the driven element. Additional reflectors are the same, except they are 4% longer at each step further away from the driven element.

These elements can be vertical and that makes the most sense in the case, suspended in the Vee. Ordinarily, the driven element is connected electrically to the device, but it should work even if it’s only coupled inductively. The driven element and the others should be spaced about 0.15 wavelength apart. This should work with transmitting, as well as receiving.

[Jayborn]

Thanks for posting your results @aspexin , well it does appear you were able to increase your (directional) range by slightly over 28%. While this is a fair bit lower than the increase I experienced in my quick test I would think one contributing factor is that most of my test was conducted over fairly open and flat farmland.

One question, was 18cm the max distance you tested or was that the best distance? If it was the max you may want to try 19cm just to make sure. Yes I know, its easy for me to say as I’m not the one climbing up into the attic!

Hadn’t thought about incorporating a yagi into the mix. Will need to think about that a bit more. I was hoping to do further testing this weekend however that’s not going to happen. Right now the plan is next weekend if the weather cooperates. I will attempt to do the next test mainly over water (portion of lake Ontario) to try and reduce the impact changing topography at the various test locations has on the results.

Thanks for the book recommendation @MikeL

[aspexin]

Yes climbing into the attic to make adjustments isn’t exactly something I have a lot of time for. The 18cm is just simply what I last adjusted to when it seemed that the shorter 6.5" had no effect. So it is the maximum distance I’ve tested so far. I can try to see if I can muster another test sometime this weekend but I have so much on my plate (and still 2 ubitx kits to assemble).

And yes, my challenge is being in downtown Indianapolis. I’m at 19th and North New Jersey St and most of my testing involves buildings about 3-4 stories tall plus a canopy of trees on a number of the streets. My stationary relays in the attic are at least 40’ above ground level but even at that height there is still a lot of obstruction when I’m range testing at ground level. And I’ve only been range testing to the West which is my most obstructed direction. I should try to do some East range testing as there is considerably less obstruction in that direction.

[aspexin]

And interestingly today at lunch from one of the local restaurants I was able to communicate with my tablet on my desk for the first time through two mesh units. I have never had a successful delivery from that restaurant before. I’m sure one of the mesh units was in my car. And the other mesh had to have been the West attic mesh. I tried this exact scenario multiple times with no success in the past.

[aspexin]

New range record for me today. I was down by the Sailors and Soldiers memorial park in downtown Indy and successfully got a message to my tablet at home (though it was delivery unconfirmed on my end) but that made a 2.01km message. It was delivered via 1 mesh node which had to be my West side node with the aluminum reflector. This means I’ve more than doubled my range at least toward the West and South. And with all the trees and buildings plus I-65 overpass in between I’m pretty surprised I managed that distance.

Also, to update from my earlier post. I did some range testing to the East which is my least obstructed view (mainly MLK park and 1-2 story homes and I got 1.3km with delivery confirmed on my end. This is about 400 meters further than my previous range testing without the reflector.

[giqcass]

Thanks for sharing. You and I have had some similar thoughts. I posted some similar ideas previously that I haven’t tested yet although I do have a Gotenna attached to a Dish antenna right now. I haven’t gotten around to actual testing. I hadn’t thought about a corner reflector specifically but I had been thinking about a yagi. At the end of the day I think a dish will be easier and more practical to put together.
Non-external antenna connector for Mesh units

[giqcass]

I thought it might be good to point out metal screen can be used to make your design as well. It should produce similar results.

[Jayborn]

Ok here is an update on some further testing I was able to complete yesterday.

For this test I decided to change the location and setup the test to occur mainly over water in order to reduce the impacts of varying topographies. Basically I hung a paired Gotenna in a tree near lake Ontario and then proceeded to move around the lake at greater and greater distances. Multiple messages were tried at each location with the Gotenna on a stand (see photo) with no reflector. Once a distance was reached where these messages failed I then tested the Gotenna with the corner reflector. From then on tests were conducted with and without the reflector.

To be honest i wasn’t really prepared for how well the Gotenna would preform all by itself and as a result I started to run out of pre-identified test locations. I am very impressed by the distance I was able to achieve with just the Gotenna.

In short here are my results:

Maximum distance I achieved with just the Gotenna 18.07 Km
(3 out of 6 messages being confirmed)

Maximum distance I achieved with the Gotenna and corner reflector 23.90 Km
(3 out 3 confirmed, no delays)

Range increase using the reflector 32%

testing notes/observations

Weather started to become and issue starting at test #8. Wind was quite strong at this location which made using the reflector difficult (Gotenna swinging, reflector bending out of 90 degrees etc…). I believe this played a factor in the Reflector failed tests during Test #8 (25.13 Km) since it was only 1.23km farther than Test 6 which had 3 easily confirmed messages.

There were tests #9 and #10 which were at approximately 29km and 43km which again had poor weather conditions ( wind/rain) and all messages failed from these locations

After retrieving the hanging Gotenna and reviewing the queued messages I found it interesting that there were no Received messages that were not confirmed. Every failed message (Delivery Unconfirmed) during the test never made it to the hanging Gotenna. This is different than my other tests where usually I will get a few messages that won’t be confirmed however they will still actually get delivered. This is most likely due to the clear path both to/from over the water.

As far as trying a Cantenna goes, it was a complete fail. I made three different iterations:

7 inch 1 wavelength lenght
7 inch 2 wavelength length
7 inch 2 wavelength length with collector cone

all failed to perform even close to the corner reflector therefore did not bother testing them during this test.

I also wanted to thank @Briann for his 3D printed Gotenna stand, it works great!

In summary the corner reflector does appear to increase the Gotenna range by around 32%. Could be more depending on location/situation (as in my first test). At this point I don’t plan on testing the reflector anymore as I have a fairly good idea on what to expect from it now.

any questions let me know.

Here are some photos.

[giqcass]

Thanks for this great info. How did you set up the cantenna? I really expected that to work. I have to try out my dish setup given your results. The area I want to connect to is only 3 miles and your tests suggest that is very possible.