220MHZ Band Antennas
VHF and UHF antennas are easy to find, but 220MHz band antennas for data radio modem are more difficult to find. This Tech Blog article provides links and ideas for sourcing 220MHz mobile antennas and 220MHz base station antennas.
1. Overview
Raveon produces data radio modems at 200 MHz for Machine-to-machine (M2M) and SCADA applications. Commercial off-the-shelf (COTS) antennas for this band can tuned to 220MHz. This note details the process for the tuning of VHF 220 MHz antenna. Raveon’s DART base stations and M8/TK8/TK9 series data radio modem products are available in this band.
2. COTS Antennas
There are many different choices for 220MHz band antennas . This article identifies a few antennas suitable for use with 220 MHz radio modems.
New-Tronics Antenna Corporation
RX-220, 3.4 dB, 5/8 wave magnet-mount mobile antenna:
(http://www.new-tronics.com/main/html/mobile_uhf___vhf.html)
MX-270, 2.4dB VHF/ 4 dB UHF magnet-mount VHF – must be cut down to resonate at 220MHz.
(http://www.new-tronics.com/main/html/mobile_mx_series_uhf___vhf.html)
Comet
HT-224, 1.3dBi 1/4 wave
(http://www.cometantenna.com/products.php?CatID=1&famID=1&childID=2)
This antenna may be available at their distributor, Ham Radio Outlet.
Trimming an Antenna
The test equipment for tuning includes a spectrum analyzer, such as HP 8591E with tracking generator and a directional coupler, such as Narda 3000-10 and suitable connectors/adaptors. The antenna length can be adjusted by trimming the length of the rod of the antennas. Loosen the lock-screw on the base of the antenna, remove the antenna rod, and trim it so that the antenna resonates on the desired frequency. Trim a little, re-install, re-measure resonant frequency, and repeat.
The lowest standing wave ratio point displayed on the spectrum analyzer will be the frequency the antenna is tuned to.
For 220MHz, the lengths of the antennas shown above are 706 mm for the RX-220 and 524 mm for the MX-270. The HT-224 from Comet has fixed length which is not adjustable.
