My 222 MHz Station
This page describes my 222 MHz SSB/CW digital weak signal modes amateur radio station. In Region 1 this is not an amateur band, but in Region 2 it is. I made the station for DXpeditions to countries in Ragion 2.
It's always fun to learn from different frequencies.
In Region 1 (Europe), 222 MHz is part of the DAB+ Broadcast band. This band is full of OFDM modulated radio signals. Channel 11D runs from 221.297 to 222.832 MHz. Channel 12A runs from 223.169 to 224.704 MHz. Signals are vertikal polarized.
The DAB channel numbers refer to the old analog AM television channels 5 to 12 that were in use before the DAB era. 4 DAB channels fit in 1 old analogue television channel, therefore the letter 12A, 12B, 12C and 12D after the channel number. One DAB channel is a data stream of approximately 2 MB. I used to be an active VHF band 3 Television DXer.
DAB DX is also fun. Here my antenna and receiver.
The antenna is a 12 element DK7ZB design and is 5.3 meters long. The antenna is for portable use, which means that it can be dismantled into pieces with a maximum length of 1 meter.
The free space gain is 16.2 dbi. The -3 dB horizontal beamwidth is 27 degrees. Front-to-Back Ratio better than 30 db, but I have yet to see the latter in practice.
Reflection attenuation in db
Horizontal plane pattern
The heart of the complete transverter is a transverter from the transverter store. The IF is 28 MHz which is converted to 222MHz. I placed a bandpass filter + LO notch behind the original transverter to get a clean signal and to meet my authorization conditions.
A pin diode switch can switch the signal from the filter to a RA30H2127M power module or vice versa the reception of the pre-amp back to the transverter. It is also possible to bridge the built-in pre-amp via a second receiver input.
The pre-amp is an amplifier with a BFT66 transistor. I made this amplifier in the eighties for television DX. I enjoyed using this amplifier again in the transverter.
I let the power module deliver approximately 20 watts of output. An SMA relay is used for the transmit/receive switching.
Indoor top view: top left the 28 MHz attenuator and PTT switch. Below that is the transverter. And underneath that a 222 MHz band filter.
On the right side from top to bottom the pin diode switch, pre-amp and SMA relay. On the back right there is a cooling block with the power amplifier and LPF filter on it
Power module with LPF
The back with connections
A linear amplifier is also made with a MRF9180 transistor. This works on 27v. The signal from the transverter is attenuated by more than 10 dB so that the output power is around 120 watts. The amplifier also contains a good pre-amp and coaxial relay. The power amplifier is a 120 - 180 MHz amplifier kit that you can buy on Ali. I converted this to 222MHz by redesigning just the LPF. The rest of the amp is unchanged except that I switch the bias on and off with the sequencer. The max Output is around 150 watts. The harmonic rejection is better than I expected and turns out to be better than 62 db.
From left to right first the top. The blue print is the power and swr meter on the front panel.
Then in the middle the pre-amp with band filter for reception. I made this pre-amp in 2006 for the Navspasur experiments. This pre-amp has a measured NF of 0.3 db. Then at the top right of the PCB a coaxial relay on the output connector.
Then start the bottom half on the left. The sequencer relay circuit. Then the actual transmit amplifier with low-pass filter. Then an input attenuator of 10 db.
HOME | Go Back