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Reviews For: Stridsberg MCA104M Active Multicoupler

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Review Summary For : Stridsberg MCA104M Active Multicoupler
Reviews: 1MSRP: $185
Description:
MCA104M is an active multicoupler designed to distribute HF antenna signals to four receivers without loss and with high isolation between ports. It is specifically suited for signal intercept and HF monitoring stations, both fixed or mobile platforms. It can be used in any HF monitoring post using receivers, scanners or spectrum analyzers. MCA104M has a mechanical and electrical design construction that will meet any government, military or commercial specification. This unit is designed to give high performance results in any radio monitoring post using multiple intercept receivers. Rugged die-cast aluminum enclosure with a black powder coat finish is standard, olive drab green (MIl-841OD) is also available on request. If only two (2) outputs are needed the model MCA102M is available.
Product is in production
More Info: http://www.stridsbergeng.com/multicouplers.html
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0015
5B4AIY Rating: 2021-03-23
Excellent HF Multicoupler Time Owned: more than 12 months.
I needed a way to couple the output of my Wellbrook Active Loop antenna to several receivers and transceivers. If you only need to couple to 2 receivers, then a simple splitter can be made with a toroidal core and some bell wire, but there will be at least 3dB (Power) loss. Whilst this is only 1/2 an S-point, it is undesirable. In my case I wished to feed the loop to my JRC NRD-545 communications receiver as well as my Icom IC-7700, and my Yaesu FTDX-101D, so using passive splitters would entail at least a 6dB signal loss, which was unacceptable.

A little research brought up the Stridsberg MCA-104M active HF splitter. This unit is specified for operation from 500kHz to 50MHz. It comprises a 3dB attenuator followed by an input low-pass filter with a -3dB cut-off frequency of 57MHz, this filter feeds a 3-terminal ERA-4SM monolithic microwave integrated circuit (MMIC) amplifier to overcome the coupling losses, and then 3 MAPD-008072 surface mount power splitters. The output from the MMIC being fed to the first splitter, and each output from that splitter fed to another splitter giving 4 outputs. The unit is very robustly constructed and mounted in a die-cast aluminium case with lugs allowing it to be screwed to a wall or other surface. It is powered by a 12VDC supply. The power input has a 1N4002 diode in series to protect against accidental reverse voltages, and it feeds a ZSR800 3-terminal regulator that provides the stabilised 8V required by the MMIC. With 12VDC input to the unit the current consumption was 81mA. There is a power indicating LED. The unit is equipped with BNC sockets for input and output.

A swept-frequency measurement using my Siglent spectrum analyser in its tracking generator mode showed that the frequency response was flat within +/-1dB from 100kHz to 50MHz, and -3dB at 57MHz. The overall input to output gain was approximately +1dB, and cross-port isolation better than -20dB over the entire frequency range.

The maximum output signal is determined by the MMIC, and taking into account the splitter losses, in my case was about +10dBm at the -1dB compression point, representing an input signal of about 0dBm. The noise figure of this MMIC is specified as 4dB, which is entirely adequate for both HF and 6m operation.

Initially the operation was straightforward, couple the BNC lead from the Wellbrook Loop downlink amplifier and bias unit to the input of the splitter, and then take the outputs to the various receivers and transceivers. Everything worked fine until I keyed the IC-7700 to its full 200W O/P in CW. When I went back to receive there were no signals. An examination of the relays used in the Icom for the antenna selection revealed that they are ordinary relays, not specifically designed for RF, and the cross-port isolation between the power amplifier output and the receive-only antenna input was insufficient. I measured 128mW, or +21dBm of RF coming out of this supposedly 'receive-only' port and that had been more than enough to damage the output splitter and the MMIC. I contacted Stridsberg and they supplied, at no charge, a replacement MMIC, but warned me that removal of the splitter could be difficult. When I examined the circuit of the splitter it was obvious that its tiny internal 100 ohm termination resistor had burnt out but soldering an external 100 ohm metal film resistor across the port terminals restored correct operation. The removal and replacement of the MMIC was quite straightforward. The moral of this is that you should very carefully check the supposedly 'receive-only' antenna ports of your intended transceiver to make sure that no unwanted RF is coupled out of them.

Obviously I disconnected the Icom! The measured cross-port isolation figures for my Yaesu FTDX101D using 100W, +50dBm, into a dummy load, varied from -7dBm @ 50MHz to -33dBm @ 1.8MHz from Antenna-1 to Antenna-3, and from +2.4dBm @ 50MHz to -24dBm @ 1.8MHz from Antenna-2 to Antenna-3. In both cases Antenna-3 was set to Receive-Only. The Antenna-3 port was coupled to the 50 ohm input of my Siglent spectrum analyser. The figures are well within the capability of the splitter to tolerate, but nevertheless I would have liked a design where the receive-only port was completely separate from the transmitter. As a further note, these signal levels are comparable to what could be picked up by the receive antenna when operating normally. If you are using a linear amplifier, then you will need to ensure sufficient spacing between the transmit and receive antennas to ensure that you do not accidentally couple an excessive signal into the splitter if you are using a passive antenna. The Wellbrook Loop has input protection diodes and is reasonably well protected, but even so, the loop should be at least 10m and preferably further away, especially if you are using a transmitting antenna with forward gain such as a beam with a linear.

In summary, although expensive, the unit is very well constructed with high quality components, and performs exactly as specified. I am certainly very pleased with my unit, and would definitely purchase it again if it were to be destroyed.

Adrian, 5B4AIY