3d printed "helical Cone reflector antenna"

[pe2bz]

Hi all,
On the Facebook group APT I noticed a message from Antonio Pereira and Sławek Klimek-Wojsa about a 3d printable mesh reflector for Helical antenna’s. In this case the design appears to be made to receive HRPT signals around 1700 MHz and results are showing nice Meteor images being received with this antenna , an Nooelec GOES preamp and RTL device directly connected to the antenna, usually hand tracking .

Printer was ready and willing to take, PLA was still around. so I decided to give it a go.
The source for the files is from Thingiverse:
1.7 Ghz HRPT Helicone Antenna by t0nito - Thingiverse which contains a PDF with the instructions too.

Keep in mind that my PrusaSlicer does not automatically corrects bad orientation on the bed nor does it enable support automatically, and my ingorance to read / follow the red warnings after slicing cost me come PLA and some hours of reprinting.

The instructions start with making a round reflector and mounting the Helical before starting to fix the mesh, however I wanted to be able to replace the Helical by any frequency, becasue I want to be able to test 1545, 1700 and 2250 MHz ranges. So I decided to start fixing the mesh without the reflector and after mounting 7 out of 8 from the straight mesh holders I noticed I’d better had mounted the base ring (which is intended to hold those holders…) first. So a short disassembly, after which assembly was a bit easier.
The mesh was not to difficult to handle, though when cutting with scissors a lot of sharp points remain. Drawing a circle on the mesh is also a thing, because most of the ink from the permanent marker goes through the holes of the mesh.

I “fixed” the edges of the refelctor / mesh with some flexible tape to prevent the mesh from hurting my feelings.

At the end I noticed that the suggested reflector plate matched the dereksgc printed helical holders, so I could have started with the suggested reflector and helical and simply only replace the helical when I want to experiment with other frequencies.

At this moment the antenna is pointing towards the sky, 1545 RHCP,1545 lna and RTL SDR, to compare it with the 1545 setup outside on the roof, with mechanical bandpass filter , 1545 LNA and RLF SDR .

First results look promising. The waterfall for the cone reflector shows clearly stronger signals, both from geo satellites and from SAR transmitters from weathersats.

I will add some images of the parts / assembly in a reply to this message. Currently printing the holder to have a bit more stable mount

[pe2bz]

Base and straight parts:

to get the idea:

amazon box of requirements

You might get the idea now:

I was still missing the base plate function:

But then I finally saw the light:

A bit more proud of the outcome:

My wonderfull test site:

[pe2bz]

Some 1545 MHz results:
This is helical outside, and mechanical bandpass and preamp inside, on reflector.

and this is the cone reflector under the top roof window, 1545 nooelen lna and rtl sdr

I just left the setup as it is for now and moved the cable to the S-band test setup, now running from 1680 to 2360 MHz on the 1545 helical

[pe2bz]

Meteor M2-3 overhead pass on 1545 RHCP helical

https://network.satnogs.org/observations/8946170/

[t0nito]

Well done, it would have been nice if you shared the pictures with the group though

[pe2bz]

You mean like the Facebook group ? I did, I added it to the original message about the antenna .

But let me make a Google doc from this too and share that on FB ok ?

[pe2bz]

2250 RHCP now mounted and pointing upwards.

Station starting obs from around 09:00 UTC now

Somehow the holder does not work for me if I want to be able to replace the antenna connector

[t0nito]

I meant the finished antenna I haven’t seen it there, but it’s fine I’m joking

[t0nito]

When I made the antenna it wasn’t meant for swappable helixes as the cone was specifically made for 1.7 GHz.

[pe2bz]

I allways go for the unexpected

I ordered the +GOES preamp but I might never use it for the weathersatellites, I just watch your images

[herman]

Nice light weight reflector, but a big frying pan or wok will be so much easier!

[pe2bz]

For now, I don’t agree. wok and pan , in all my experiments, tend to invert the signal, so, needing LHCP for RHCP signals. Somehow, this cone reflector works different. There is no inverting of the signals.

Till now, I am running with 1700 MHz RHCP feed, this reflector gives the best results so far even for 1545 and 2200 MHz signals

[t0nito]

The measurements aren’t random like a frying pan or wok. The cone is 134mm base 440mm top, 88mm height with a 29.7º angle. Optimized for 1.7 GHz.

[herman]

It is a little more subtle than that. If you beam a signal into a reflector as with a TV dish, then the signal is inverted and you need a left hand helix for a right hand signal.

However, if you connect a ground plane to a helix, then it doesn’t invert and you need a right hand helix for a right hand signal.

In this case, your reflector works as a ground plane, so the signal stays right side up.

Cheers,

Herman

[pe2bz]

So, after 72 hours of observations on both 1700 and 2250 MHz with the 1700 RHCP helical in the helicone antenna (both tested with their matching bandpass/ preamp combination) I am still impressed / satisfied with the results.

For the S-band 2250 observations, most signals are stronger when overhead the helicone antenna AND have a longer durations as compared to the 2250 RHCP helical with flat reflector and same bandpass / preamp. In the time observing S-band I succesfully identified 3 satellites with weak signal which till now appear to have been invisible in my strf recordings.

Now going to try to re-design the stl files for a 2250 MHz version , on which I am not sure how to start so this might take some time.

Currently my station 1433 is back to 2250 RHCP , filter and preamp on the roof, and the helicone is connected to different SDR’s to try and run some inmarsat reception. Might exchange the 1700 RHCP for the 1540 RHCP this weekend.

It’s still fun

[pe2bz]

2250 RHCP close to finishing. All dimensions reduced to 75 percent which nicely matched the math for 2250 MHz. A bit of a challenge to assemble, but getting there…

[pe2bz]

Now up, unfiltered, with preamp on station 3442. Started scheduling.

[pe2bz]

https://network.satnogs.org/observations/9049440/

There is reception. However I might need to add another mechanical bandpass filter

[pe2bz]

Totally not sat topic, but without preamp, pointing 30 deg elevated toward Hellasat (39 degrees East) I receive the beacons from Rotterdam, 16 km away, on 3400 and 5760 MHz, for which 5760 MHz is a first for me

[t0nito]

That’s great, I’m actually designing an S band from scratch, but reducing the antenna to 75% was a smart move