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 run high power, an external LPF is advisable.

Sprious Emission
The mean power of the any spurious emission from a station transmitter must be at least 43 dB below the mean power of the fundamental emission on a transmitting frequency below 30MHz or, at least 60 dB on a transmitting frequency between 30-225 MHz as per the Part 97 requirements. Whether you run barefoot 100 W or legal limit 1500 W, the same 43 dB for HF or 60 dB for the 6m band rule applies.

Suppose you are running 100 W barefoot on HF with 43 dB attenuation for spurious emission, your spurious emission power is 0.005W or 5mW.  You want to run a kilowatt power amplifier. You get 1000W on the fundamental frequency along with spurious emission of 0.05W or 50mW. It is sort of QRP on harmonic frequencies! Simply put, when you run power amplifier, your spurious emission is also boosted by the same formula. When you run legal limit 1500 W, your spurious emission power is 0.075W or 75mW.

Solution 
Improve your spurious emission by adding an external LPF. Use the 120 dB attenuation external LPF by Sagami Engineering. Your spurious emission power is down to 1.5 × 10-10 W (0.00000000015) or 150 pW (picowatt) at 1500W operation level. Even if an internal LPF in the transmitter is failing, you will get a PPM level cleaner signal. It is 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.

Sagami Engineering Manufacturing 
Satoru Matsushima JA1EUI, a founder of Sagami Engineering has designed uncompromised high quality LPF’s, CMF’s and coaxial antenna switches for the amateur radio community. Satoru was an engineer at Anritsu in Japan. He was involved with radios and measuring instruments designs there. Anritsu’s flagship measuring instruments are famous and that what he uses for his design works and quality assurances.  

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) The LPF and CMF should be installed in order shown in the diagram. The CMF's and LPF's are bi-directional. Either side can be connected to TRX/AMP or ANT.


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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