[Note: downconverter not included!]
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Introduction
Some years ago (1992) when experimenting with S-band antennas I threw together a simple 2 turn helix dish feed in a couple of hours, well aware that this solution could be improved upon. It had always been my intention to 'productionise' a version of this for use with the AO-40 and other amateur radio satellites. [2019 - for example the Es-hail-2 QO-100 geostationary satellite].
Experiments with an alternative feed based on the 'patch' principle showed it to be a better option both electrically and mechanically. Freddy de Guchteneire ON6UG used his formidable microwave antenna design skills to develop the feed electrically; then it was refined jointly with James Miller G3RUH who undertook production, manufacture and distribution. Together we offer you this ready-to-use design.
Description
This feed is a patch antenna for 2.4 GHz intended for use with a parabolic reflector dish. It is supplied fully assembled and tested.
[Note: downconverter not included!]
When installed in an f/d 0.35 60cm dish for example, the ideal beam pattern of this feed results in a G/T typically 1-2 dB better than with the small helix often used for this application, and the axial ratio is almost perfect. The recommended f/d ratio for a dish using this feed is 0.3 to 0.5, the smaller values giving lowest noise reception (highest G/T), but the higher values a little more gain. SWR is better than 1.2:1 across 2.3 - 2.4 GHz. Any size dish may be used!
To realise the performance offered by today's lowest noise converters, you need a feed and dish system that together contribute less noise than the converter. This feed achieves that.
Feed polar plot:
The feed has LHCP (left hand circular polarisation) so that when installed in a dish the resulting polarisation is RHCP, as used by Amsat spacecraft. The feed may be used for transmission (150W) or reception.
An N-male connector is used for direct coupling to typical S-band converters. The alternative N-female connector version can be supplied at no extra charge.
Mounting is via legs (not supplied) to three M5 (3/16") holes in the feed. The feed is weather-proofed to keep out direct rain, and is ventilated to prevent internal moisture build-up. All component parts are non-rusting.
The input is DC grounded; static charge cannot build up to damage converters.
Remember, the feed is an antenna in its own right, and can be used independently where a wide-beamed low gain system is needed.
The patch has been tested as a transmit antenna up to 150W - the limit of the PA used. [ Anyone successfully exceeding this, please let me know ].
Typical dish installation:
Summary
Frequency 2250-2450 MHz Gain 8.5 dBic -3dB beamwidth 85° -10 dB beamwidth 125° SWR < 1.2:1 Axial ratio 1.05:1 Feed polarisation LHCP [Option: RHCP] Suitable dish f/d 0.3 to 0.5 Power handling 150 watt Connector N-male [Option: N-female] Impedance 50 ohm Overall diameter 120 mm Depth 17 mm excl. connector Weight 130 gram
Feedback from users.
Photos of users' systems.
Stock, as of date below, is:
LHCP no stock.
RHCP no stock.
Production of this item has ended.
Some statistics
Qty. 607 patch antennas were manufactured.
The first was shipped on 2001-Aug-06 and the last on 2026-Oct-23.
Of these qty. 20 were RHCP; all others LHCP.
Qty. 61 were shipped with an N-female connector; qty. 546 with the 'default' N-male.
Qty. 292 were shipped with a 60cm diameter dish.
84% were delivered to radio amateurs in 32 countries, the remainder to space industry, universities and radio astronomers world wide.
Thank you everybody for your fantastic support of this project!
Last updated: 2026 Oct 23