The MIZUHO and NISHI MUSEN Reflector
and unofficial English language Mizuho enthusiasts site
On your left is one of Mizuho's recent products, the KX-QRP antenna coupler. Introduced in 2001 and discontinued in 2002, the KX-QRP is a very small antenna tuner designed to match the Yaesu FT-817 in size. Of course, it will work with any QRP rig, including Mizuho's own. On the rear panel there are inputs for both coax-fed and wire antennas. The coupler utilizes a Pi-C matching network. This beautifully constructed little tuner is rated for only 5W of power handling capacity, though reflector members report putting 10W through this tuner without any arcing over or other problems.
Specifications:
Frequency Range: 3-30 MHz
Maximum through power: 5W
Input impedance: 50-600 ohms
Dimensions: 162x55x130mm
Weight: 800g
The KX-9S Sky Coupler essentially replaced the KX-QRP in 2002 and is a current product. It is essentially a KX-QRP with six meter (50-54 MHz) coverage added. for a slightly higher price. Functionality and construction are otherwise identical to the KX-QRP, and the above manual should still be valid.
Here is another somewhat older Mizuho antenna coupler, the KX-2 Sky Coupler. This tuner is intended for shortwave and broadcast listening only, but it will safely handle up to about 10W of power without arcing over, so it is suitable for QRP use. An optional Z-2 loop antenna for broadcast listening was available. There appear to be several versions of the KX-2. Some have just terminal screws for input and output and gaping holes where an SO-239 connector might be added. This is the configuration shown in the Japanese manual. At least some had SO-239 connectors factory installed similar to the later KX-3 model. In addition, some have rack mount handles as shown in the picture while others do not. Once again, construction is first class.
Specifications:
Frequency Range: 0.5-30 MHz
Maximum through power: 10W
Input impedance: 50-600 ohms
Dimensions: 220x66x154mm
The KX-3 Sky Coupler replaced the KX-2. As you can see, the two units are very similar and the specs are identical. However, the KX-3 had coax inputs and outputs as well as wire inputs and outputs. The rack mount handles are gone. In addition, a matching preselector, model SX-3, was introduced to replace the venerable SX-1 and SX-59 models. The KX-3 also matches the AP-1D Audio Processor in style and appearance.
Specifications:
Frequency Range: 0.5-30 MHz
Maximum through power: 10W
Input impedance: 50-600 ohms
Dimensions: 220x66x154mm
The KX-3HF was a variation on the KX-3 design made specifically for the QRP ham radio market.
This is what Mizuho antenna couplers looked like back in the 1970s. This is the KX-1.
Specifications:
Frequency Range: 0.5-30 MHz
Maximum through power: 10W
Input impedance: 50-600 ohms
Dimensions: 150x67x146mm
Information on other antenna couplers, photos and specifications will be posted here shortly.