Tagged: discone

Constructing a 3D Printed Wideband 900 MHz to 11 GHz Antenna

Thanks to Professor John Jackson of JR Magnetics for writing in and sharing his design for a 3D printed wideband antenna designed for 50 Ohm 900 MHz to 11 GHz operation.

John required a wideband antenna that could cover the cellphone bands, WiFi, Bluetooth up to 6 GHz and the new USB band from 5 GHz to 10 GHz all in a single antenna installation. He also needed the impedance to be as flat as possible to reduce signal pulse distortion. First he looked into classic discone and sphere antenna designs, but found that while a sphere had the required bandwidth, it did not have the desired impedance characteristics, and a discone had the desired impedance characteristics, but not the ultra wide bandwidth required.

To get around this John combines the sphere and discone designs together to create a sort of icecream with cone looking shape. This results in the ultra wide bandwidth required, and a relatively flat SWR that stays below 2.

The design is easily reproducible by anyone with a metal 3D printer. The antenna's top hemisphere and cone are printed in brass, whilst the radome and supporting structure are printed in plastic.

We have uploaded John's original document here (pdf warning), and display some of the images below. The full build instructions can be found on his website, and John is also selling the 3D printed parts via Shapeways.

jran900-top
jran900-bottom
jran900-radome
JRAN900-mount
jran900-swr
sphere-cone-ant-geo
jran-proto-bw-175

Constructing a 3D Printed Wideband 900 MHz to 11 GHz Antenna

Thanks to Professor John Jackson of JR Magnetics for writing in and sharing his design for a 3D printed wideband antenna designed for 50 Ohm 900 MHz to 11 GHz operation.

John required a wideband antenna that could cover the cellphone bands, WiFi, Bluetooth up to 6 GHz and the new USB band from 5 GHz to 10 GHz all in a single antenna installation. He also needed the impedance to be as flat as possible to reduce signal pulse distortion. First he looked into classic discone and sphere antenna designs, but found that while a sphere had the required bandwidth, it did not have the desired impedance characteristics, and a discone had the desired impedance characteristics, but not the ultra wide bandwidth required.

To get around this John combines the sphere and discone designs together to create a sort of icecream with cone looking shape. This results in the ultra wide bandwidth required, and a relatively flat SWR that stays below 2.

The design is easily reproducible by anyone with a metal 3D printer. The antenna's top hemisphere and cone are printed in brass, whilst the radome and supporting structure are printed in plastic.

We have uploaded John's original document here (pdf warning), and display some of the images below. The full build instructions can be found on his website, and John is also selling the 3D printed parts via Shapeways.

jran900-top
jran900-bottom
jran900-radome
JRAN900-mount
jran900-swr
sphere-cone-ant-geo
jran-proto-bw-175

A Discone Antenna made from 3D Printed Parts and Aluminum Rods

Over on his blog author ByTechLab has posted about his 'mostly 3D printed' discone antenna. A discone is a type of wideband antenna, so it is commonly used with SDRs like the RTL-SDR that have huge frequency ranges. Building a discone can be difficult, but ByTechLab shows that with a 3D printer it is possible to print the aluminum rod mounts, which significantly reduces construction complexity. His post shows the exact directions, and the stl files are available over on Thingiverse.

Note that back in March we saw another 3D printed discone by mkarliner that used a full cone design with the cone being made out of aluminum tape. Discones based on aluminum rods should however be more weather resistant, and more able to withstand wind loads, so ByTechLab's design is more suitable for permanent outdoor mounting.

ByTechLabs' Mostly 3D Printed Discone Antenna
ByTechLabs' Mostly 3D Printed Discone Antenna

A Discone Antenna Made from 3D Printed Parts and Aluminum Tape

A Discone is a type of antenna that is designed to be resonant over a wide range of frequencies. Most antenna designs only really receive well on a few resonant frequencies, but a Discone is resonant over a much wider frequency range. This makes it a good partner for RTL-SDR and other SDR units as many SDRs tend to have wide tunable frequency ranges. With a wideband antenna like a Discone connected to an RTL-SDR one can scan over the almost entire tunable frequency range without needing to change antennas for each band. The drawbacks to a Discone however is that the antenna gain is not very high, and that it makes the SDR more susceptible to out of band interference. They also tend to be fairly expensive and difficult to build.

However now over on Thingiverse, mkarliner (aka Mike) has a remedy for the difficulty in building a Discone with his 3D printable Discone design. To construct it you simply need the 3D printed parts, some .3mm and 2mm plastic sheets, a 25mm plastic conduit and some aluminium tape. Mike's design works from 400 MHz and up, but the design could be easily enlarged for better performance on the lower frequencies. He writes:

The Discone antenna is remarkable in that it is capable of receiving and transmitting over a wide range of frequencies with good matching. Because of this, it is a good match for SDR receivers such as the popular RTL-SDR sticks.

The only really tricking thing about making a discone is that the disc has to be balanced at the very top of the cone, which is mechanically awkward.

The two parts here allow the cone to be solidly clamped and provide an adequate base for the disk. There also two holes for bring the coax centre and braid out to the disc and cone.
The base part has a socket at the bottom for 25mm (1 inch) plastic conduit for mounting

This antenna illustrated is designed for 400MHz and up, and as such transmits well on the 70cms amateur band, US and UK PMR channels and 23cms. It also receives aircraft ADS-B signals very well. I used .3mm plastic sheet for the cone and 2mm plastic for the disc, and then covered them with aluminium weatherproof tape. Be sure to check for continuity across the tape stripes.

The screenshot is of a calculator by VE3SQB which can be downloaded from http://www.ve3sqb.com/ if you want to make attenna's for other ranges.

A 3D Printed Discone
A 3D Printed Discone

If you're interested in building wideband antenna there is also the planar disk antenna (pdf) which can be built out of pizza pans.

Instructables Post on Building a Discone Antenna

A Discone is a wideband antenna that is a great starting antenna for general RTL-SDR use. Over on instructables.com, user cyfus has created an instructable showing how to build a 55 MHz+ home made discone antenna for his RTL-SDR dongle. His instructions show how to build it out of parts and tools sourced entirely from hardware and electronics stores.

Using this antenna cyfus was able to receive signals from 25 MHz to around 900 MHz.

Home made Discone Antenna
Home made Discone Antenna

YouTube: Unboxing new Antennas for use with the RTL-SDR

On YouTube Eric William has posted a video showing him unboxing two new antennas that he intends to use with his RTL-SDR. He unboxes a new QFH antenna for use with receiving NOAA weather satellite images, and a new Discone antenna for general wideband receiving. If you are interested in buying commercial antennas for use with your RTL-SDR, this video may be useful at giving you some idea of what’s available.

New Antennas for my SDR Setup- Mailbag Monday

Eric also recently posted a video showing an overview of his RTL-SDR setup which is also an interesting watch.

USB Software Defined Radio- PC Software & Cloud Storage

Beginners Antenna Guide

Akos from the SDR for mariners blog has just written another post that is a guide on constructing and buying beginner level antennas for the RTL-SDR. The post shows how to build a simple ground plane antenna out of wire coat hangers, and also discusses monopoles, telescopic antennas, rubber duckys and discone antennas.

Simple Coat Hanger Groundplane
Wire coat hanger ground plane Antenna

Homemade ADS-B Collinear Antenna

Earlier in the week a video comparing a Discone to a Coax Collinear antenna for ADS-B reception was posted. The author of that video has now posted on his blog a tutorial on how he made the coax collinear antenna. Check out the video tutorial below.

Making an inexpensive 1090MHz ADS-B collinear antenna

Discone Vs. Homemade Collinear for ADS-B

YouTube user nerdsville shows a signal reception comparison of his discone antenna and his home made 1090 MHz tuned ADS-B collinear antenna in this video. The collinear antenna shows a dramatic improvement over the discone.

ADS-B is a broadcast system which can be used to track aircraft like a radar. More information about rtl-sdr and ADS-B here.

Demonstrating performance of home made 1090MHz ADS-B collinear