L-Band Antenna - nolle.engineering

Specifications

All parts 3D printed from PETG material, UV resistent and water proof.

	LHCP Variant	RHCP Variant
Radiating Element	3 turn left handed helix, 3.5mm copper wire	7 turn right handed helix, 3.5mm copper wire
Reception configuration	Consumer type satellite dish	Direct reception
Mounting Option	Mounts in standard 40mm LNB clamp (for offset dishes) Universal mounting via 3 M4 bolts (for prime focus dishes)	Universal mounting via 3 M4 bolts
Dimensions	Length: 186mm, Diameter: 180mm	Length: 374mm, Diameter: 180mm
Connector	N-type	N-type
Applications	Reception of geostationary satellite services, e.g. Inmarsat, Iridium, digital telephony / data, digital weather pictures	Reception of geostationary and LEO satellites when mounted to el/az-rotor
Availability	nolle.engineering (webshop)	nolle.engineering (webshop)

RF Performance

LHCP, 3 windings

RHCP, 7 windings

Concept Renderings

RHCP 7-turn variant. Helix wire is internally supported for stability. Radome can be removed (3D printed thread).

LHCP 3-turn variant. The reflector can be cut out to make space for the LNB arm depending on the antenna forward position.

RHCP Prototype

Individual solution for mast mounting (utilizing 40mm mounting option)

LHCP Prototype

Early protoype. Reflector not cut out here, helix gain satisfactory. RF components such as LNA and SDR stick are aligned inside 40mm pipe.

Use Case

Architecture

See below an example on how to setup your L-Band receiver station. Signal is filter, amplified and digitized by software defined radio then provided to software receiver running on your local PC.

Filtering is optional, it might be necessary depending on your local RF environment (Wifi, LTE presense).

Components

Left: 3-turn LHCP on 1.5m prime focus dish (click to enlarge) vs. Right: 7-turn RHCP (direct reception)

Decoder Software

A list of popular INMARSAT and others deconding software packages:

https://tekmanoid.com/egc
https://github.com/jontio/JAERO/releases

Web SDR Demo

23.10.2022: I am operating a live web SDR with the LHCP version on a 80cm offset dish. It is located at JN58UA and currently pointed towards Alphasat tuned to 1541.1 MHz with 2MHz bandwidth.

Click on the image to test the receiver. It is fully interactive:

Components	Description	Source (incl. 3rd party and affiliate links)
L-Band Antenna	LHCP or RHCP as per your preferences	nolle.engineering (coming soon)
N-Type to SMA adapter	Adapter from antenna to filter / LNA (N male to SMA male)
Bandpass Filter	Blocking any interference from Wifi, LTE etc. improving signal strength	GPIO LABS 1525 to 1559 MHz Bandpass Filter
LNA (bias tee)	Low Noise Amplifier (LNA) and Saw Filter Module 1542MHz centre frequency Powered via SMA output, requires SDR with bias-T.
LNA	Low Noise Amplifier (LNA) and Saw Filter Module 1542MHz centre frequency Powered via micro USB 5V
SDR (bias tee)	Software Defined Radio, including bias-T required to power LNA
SMA Interconnects	SMA male to SMA male connecting between components
SDR#	SDR Software	https://airspy.com/download/