Yaesu FT-847 VHF/UHF transceiver.
Transceiver for 2m and 70 cm
Antennas for 70 cm, 23 cm, and 2 m.
70 cm yagi
23 cm transmit converter.
23 cm transmit converterMy 23 cm transmitter is the MKU 13 OTX up-converter from Kuhne Electronic.The power level at 1268 MHz is about 1 W.
The MKU 13 OTX is keyed by applying 12 V DC to the 144 MHz port via the coax cable. Keying can also be done manually (PTT man. is grounded). When MKU 13 OTX is keyed, the terminal +TX out goes high and activates the PA.
You can find the circuit diagram here.
23 cm PA module.
|23 cm PA with 20 W output|
The active element in my 23 cm PA is Mitsubishi RA18H1213G, which is a power-module for 1240 - 1300 MHz.
The PA is a kit purchased from PE1RKI Bert Modderman.
The construction is described in details here.
Cabinet for 23 cm TX modules.
|Cabinet for 23 cm modules|
The cabinet contains the transmit converter, the PA, and the low-pass filter. There is also a DC distribution board.
The cabinet is a diecast aluminium box from Hammond (item 1550J). The surface of the box is about 1000 cm2 which is sufficient for keeping the PA temperature low. The weatherproved box is mounted in the antenna mast.
Mode L/v configuration.
|Mode L/v configuration|
The block diagram shows the L-band and VHF configuration, which is used for the satellite AO-92. Uplink is 1267.350 MHz FM, and downlink is 145.880 MHz FM.
The uplink antenna employs circular polarization (RHCP) to secure a constant signal at the satellite. The downlink antenna has horizontal polarization.
Click the picture to enlarge.
ANT: When transmitting, the bias-T injects +12 V into the coax-cable via this port. The DC voltage makes MKU13 OTX transmit. No DC voltage is applied to ANT when receiving. The port transfers RF from transceiver to antenna, both when receiving and transmitting.
TRX: This port does not carry any DC voltage, only RF. The transceiver's antenna socket is connected here.
12 V: A relay (not in the photo) sends +12 V to this port during transmit. No voltage is applied when receiving.
The relay's circuit diagram is here (opens in a new tab).
The LCD display shows the current rotor position to the left and the new position to the right.
The tracking software (PstRotator) runs on my PC and generates position data for the satellite. Position data is transferred to the ERC-3D rotor controller. Relays inside the ERC-3D activate the rotators as necessary.
I bought the rotator on Ebay. It was in good working order, but I had to replace the 500 ohm potentiometer inside the housing.
The Yaesu control box serves as a power supply for the rotator.
I've added a 5V DC PSU inside the control box. The potentiometer inside the rotator is fed with this voltage. The voltage on the potentiometer's wiper is measured by the ERC-3D controller. The wiper voltage is proportional to the position of the antenna. 0.07 V corresponds to 0 degrees, and 4.60 V corresponds to 360 degrees.
Written by OZ1BXM Lars Petersen. Latest revision 23-Mar-2018.