yes. Good thing is the minimum spacing for a diversity array is very small at 1.5GHz
I have not seen that design before. It should be interesting to see what you build.
-C
Ok, Itās 2:00 A.M. and im still up messing with antennaeā¦
Here is your paper Helix antenna X 2 in a phased array. Just finished putting on string supports to combat the sag.
Here were the readings on the kit patch antenna from earlier today. (which btw still kicks ass!) The values hadnāt changed enough from earlier today to warrant taking another screenshot.
Here are the results of the phased helix array. RSSI is cooking!!
I have not put this array on the analyzer yet to determine where I can improve it. This was just a down and dirty āGet out there and do itā type of project. One thing to talk about it but there is nothing like getting out there and doing it.
Nothing but cardboard, foil, tape, wire and string. Oh and a little math.
Wasnt a scientific test. I held the tilt of the box with my finger and did not spend too much time aiming. its 6 degrees out there. With a little aiming and stabilization I believe this thing will break the -107 RSSI barrier.
Next up will be a 4 paper helix phased array. Something to mention, if you go bigger than this dual array you are going to want a much thicker box for the reflector or put in some ribs or a piece of plywood.
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Ki4its and the RF Ubertech Crew ,
Really enjoying this discussion and rapid prototyping ! That dual helical phased array did indeed double your signal as predicted ( Almost 4dB At <10 cents per dB )which also demonstrates the REPEATABILITY of the paper helix. Thousands of miles of lonely outer space spanned with an antenna made mostly of ''paper products". Impressive!
RadioRay ā¦- .-
I think your reflector may be a bit undersized for 1.5GHz.
But it is hard to tell scale from your photo.
How are you handling the phasing? Longer coax to one helix?
-C
LOLā¦
Nope. Wavelength times 0.94 is the formula used. The reflector is actually over-sized in the X and Y.
Most times when folks hear āphased arrayā the assumption is made that it is a steerable array or better known as electronically scanned array.
The term phased array is also used for unsteered array antennas. Where the phase of the feed power is fixed.
In this case the array is being fed in the electrical center.
Marvelous! This is promising. So, the āoptimumā minimum reflector following the calculators is 119mm-120mm. My design is 117mm. Nevertheless, it works. I tried to stay away from fractions of cm or inches to simplify construction.
Now, that said, this array will absolutely work, as you demonstrated. For a more refined prototype, we should look at optimum spacing between helices
I have a suggestion as to fixing the āsagā.
I did use double sided tape in the middle of the reflector on the bare cardboard, specifically where the flange would be after applying the foil. This is the simplest way to accomplish some rigidity.
The other method is to simply make another bare cardboard plate, same size as the reflector, with holes to accommodate the helix ābarrelsā, but small enough to capture the flange petals between it and the reflector plate. The holes can be round (difficult) or square (easy). Slide it over the barrels and secure. This could be done with individual smaller plates for each ābarrelā as well. Main thing is the foil needs to be firmly secured to the cardboard backing at any point where it is to support the barrel flange, so it canāt pull away.
Hereās some more math with illustrations 
http://piserjournal.org/wp-content/uploads/2014/05/V12-381-385.pdf
Roger that on the spacing between helices. For the quick down and dirty last minute build last night I used 207mm
center to center of each helix. so, given the non con-formal roundness of my tubes 
the spacing between is about 133mm . I built it in about 2 hours and didnt have the energy to do any post-build analysis. This can definitely be optimized for sure.
As for the sag, yes I should have reinforced the foil to cardboard layer where each helix was going to be placed. im thinking along the lines of flange plates as you mentioned.
you have to keep in mind that it is not a tuned āreflectorā but is actually just a counterpoise, so it is no where near as critical
Are those toilet paper rolls?
ā¦The LNA IC is dirt cheap, but the proven is not price. It is getting the LNA to the end user.
Tell this to meā¦ I live in Cuba Island and that means no Pypal or a like and anything that has a USB port and a SMA connector is treated like a Wifi dongle/AP and hence held/taken by customs.
My RTL-SDR passed in a pocket of a friendās kid traveling aboard, with some luck the kid was not searchedā¦
73 Pavel CO7WT.
Canāt find the link to the paper helix design, can anyone sent it to my at pavelmc in the domain of google free email service (gmail.com, thatās to avoid spam)
Thanks in advance.
Sent
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Got it! thanks
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Ok, here is the aluminum foil, cardboard and expanded polypropylene patch antenna:
Initially, in the same exact spot, it runs about 1dB RSSI under the Outernet patch.
This is not optimized for the exact dielectric constant for polypropylene and cardboard. Pretty good though, considering.
The foam sheet is ~6mm, and the cardboard backing for the driven element is ~1.5mm, so spacing is right at 7-8mm
I made some parasitic elements for it and they dd not work as expected, so that is shelved for now. There are important considerations when adding parasitics that I have not had time to fully explore as of yet.
As it stands, the cardboard nā foil patch works fine by itself, no exotic materials needed other than the SMA pigtail. (we need to work on thatā¦)
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Would you mind taking a picture of the stack up/side view? Shouldnāt the foam have a dielectric constant that is basically the same as air?
@k5ted
Fantastic job!!! It is great to see folks applying their knowledge and time on this. I appreciate your designs and look forward to seeing what else comes out of your shop!
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The parasitic thing is a buggerā¦ I didnāt find any sort of good reference to use for element dimension and spacing, so I guessed -5% size at the same 7mm spacing. Didnāt work. Tried another at -10% size and 7mm and same result. Nada.
WIthout the parasitics itās good.
You might be interested in this site:
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