EME219 70cm UHF X-POL Switch
The EME219 70cm UHF X-POL switch has been designed to be used with two 435MHz yagi antennas mounted in a X configuration for use with the LEO Satellites. The switch allows the antennas to be switched between Vertical, Horizontal, Right Hand Circular and Left Hand Circular Polarization. Depending on the bandwidth of the antennas used, the switch will work between 430 and 440MHz for both terrestrial horizontal SSB, and vertical FM polarization. For countries that use FM above 440MHz, most Antennas designed for 435MHz would be outside of their operating range.
This product has been fully tested over time and can easily handle the full 75W output power from an IC-9700 into correctly matched Antennas over the 430-440MHz 70cm band. Each Relay only has to handle half the RF power as it is split, but the power rating of the Relays is also dependent on the return loss from the Antennas being low in each polarization mode. It is highly recommended that the return loss is fully tested on the frequencies and different polarization modes that are required of the Antenna system before using full power.
The Antennas required need to have a very clean pattern and be very close to 50ohms. Antenna designs from DG7YBN or G0KSC are ideal. The switch relies upon the signals from each antenna arriving at the X-POL switch the same time, so if one antenna is mounted in front or offset on the same boom, then compensation of one of the antennas feed line lengths will be required to add the required delay to the signal.
The PC board is designed to suit a low cost GME mast head enclosure which provides high protection of the circuitry from weather.
In the construction notes section 6. has been changed to.
Refer to the Kits webpage pictures. Fit one cable as shown on the Kits webpage from the H to F connections on the PC board with a single turn. Fit the other cable from G to E making sure that both cables are neatly secured and in a vertical position on the board. Using the supplied cable ties, secure the cables as shown on the Kits webpage.
The switch has been designed to be easy to construct, but does require experienced skills to fabricate the coaxial cable phasing lines. BUY THIS PRODUCT
Top view of the EME219-70CM Polarization Switch
Bottom View of the EME219-70CM Polarization Switch
Side view of the EME219-70CM showing how the phasing lines are routed
Side view of the EME219-70CM showing how the phasing lines are routed
Side view of the EME219-70CM showing how the phasing lines are routed and soldered to the board before the relays are fitted.
Side view of the EME219-70CM showing how the phasing lines are routed and soldered to the board before the relays are fitted.
The Tests below show the through loss, return loss and the phase of the signals from the TRX to Antenna connectors for Vertical, Horizontal, Right Hand and Left Hand Circular polarization. The phasing lines were optimized using a DG8SAQ VNA with a 50ohm BNC termination on the unused antenna port. The phasing line lengths are slightly different than calculated and include the strip lines and relays that all affect the optimized lengths. The results indicate that the phases between the antenna connectors for the various polarizations are within a couple of degrees. Vertical is -271.85 degrees, LHCP is 1.22 degrees, Horizontal is -91.51 degrees, RHCP is 181.6 degrees.
EME219-70CM TRX to ANT1 ( RL1 Off RL2 Off Vertical )
EME219-70CM TRX to ANT2 ( RL1 Off RL2 Off Vertical )
EME219-70CM TRX to ANT1 ( RL1 On RL2 Off LHCP )
EME219-70CM TRX to ANT2 ( RL1 On RL2 Off LHCP )
EME219-70CM TRX to ANT1 ( RL1 Off RL2 On Horizontal )
EME219-70CM TRX to ANT2 ( RL1 Off RL2 On Horizontal )
EME219-70CM TRX to ANT1 ( RL1 On RL2 On RHCP )
EME219-70CM TRX to ANT2 ( RL1 On RL2 On RHCP )
The GME Masthead enclosure will accept cables up to around 8mm in diameter. Therefore larger cables like RG8/213 cannot be used. Larger cables would also place too much strain on the BNC sockets on the pre-amplifier board. To connect the Antenna feed line to the pre-amplifier, and pre-amplifier output to the main feed line, we recommend the use of CNT®240 ( 240 Type ) cable with crimped BNC connectors. CNT®240 is double shielded and has losses similar to RG213 cable, but has a much smaller 6mm diameter. Use the website search box and search for 240 series cable and connectors.
The EME219 board mounted in a GME Masthead Enclosure
The Enclosure has a locking Tab that holds the board firmly
