Who needs low pass filters (LPF)?
Today’s state-of –the-art transceivers and amplifiers can indeed pass the FCC requirements for spurious emissions. Nonetheless, they can still generate enough spurious RF energy to interfere with the TV and broadcasting receptions. Your aim is not only to pass the FCC’s test but your neighbor’s, isn’t it? When you are planning to run high power, LPF is still advisable.

What is LPF anyway?
LPF is the cure for the differential mode interference. Differential mode is the mode used by the desired signal on a transmission line. LPF allows passing through differential mode current below designed cut off frequency but attenuates above it. Thus, it is called Low Pass Filter.


Sagami Engineering offers two serious LPF’s.
One is for the HF transceivers and the other for the popular HF+6m transceivers. Both are rated for 3.0 kw key down and attenuate up to 120dB. They are fabricated from two premium British made aluminum die-casts, specifically designed for EMI/RFI shielding purposes, to avoid interplay between them internally then housed in an aluminum case. [See EX.1] This enables a sharp filter response characteristic and an exceptional attenuation. Spurious emission from the LPF itself has no chance with this unique double shielding structural design.
 

HY3K-HG Filter

Price: $195.95

HY3K-SP6 Filter

Price: $219.95

 

 

Model # HY3K-HG HY3K-SP6
Application HF transceivers & amps HF/6m transceivers & amps
Passband (MHz) DC-30 DC-54
Cutoff Frequency (MHz) 38 (-3 dB) 64 (-3 dB)
Impedance (ohms) 50 50
Power Rating (continuous – kw) 3.0 3.0
Attenuation (dB) 95-120 (75-500 MHz) 95-120 (90-500 MHz)
Ch 2 video carrier Attenuation (dB) 60 N/A-Below cutoff freq
Insertion Loss (dB) <0.2 @29.7 MHz <0.2 @54 MHz
Input SWR <1.3:1 <1.3:1
Connectors SO-239 SO-239
Size 11”L x 3”3/16W x 3”3/16H 11”L x 3”3/16W x 3”3/16H
Weight (lbs) 2.8 2.8

One Year Manufacturer's Warranty

Made in Japan. 

 

 

 

INSTALLATION


1) LPF and CMF should be installed in order shown in the diagram.


2) The distance between transceiver/amplifier and filter should be a minimum. The use of a plug-plug adapter is recommended but a coax cable can be used as long as the cable length is 1’ or less. 1’ is 1/8 wave length or less of 110 MHz and thus eliminates the potential of harmful line radiation.
 

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HY3K-HG

FILTER RESPONSE CHARACTERISTIC

The limit of test measurement setup is 80 dB. Noise floor limited.

HY3K-HG

FILTER RESPONSE CHARACTERISTIC (Simulation data)

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HY3K-SP6

FILTER RESPONSE CHARACTERISTIC

The limit of test measurement setup is 80 dB. Noise floor limited.

HY3K-SP6

FILTER RESPONSE CHARACTERISTIC (Simulation data)

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