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150 200 Watt OEM Final Amplifier Section
with High Performance Low Pass Filter


Schematic Diagrams and
installation instructions


Replacement Final Amplifier and Low Pass Filter Section
for Magnum S Series 175 Watt Amateur Radios (and more)

SX-175 Upgrade your 50 Watt S-3, S-6, or S-9 (and many many more radios) to a 175 Watt Radio
with the SX-175 PowerCabinet!


Included Parts:

  • Aluminum Top Cabinet and Bottom Cabinet/Heatsink

  • 175+ Watt Final Amplifier - Low Pass Filter - Directional Coupler Circuit Board Assembly

  • Heavy-Duty Aluminum Mounting Bracket

  • Heavy-Duty, 12 Gauge, 10 Foot Power Cord Assembly with 30A Inline Fuse
  • Fits many radio types as long as the amplifier fit's without obstruction.



    This is a complicated modification and should not be done by an amateur. You should probably
leave the installation and alignment to a proven technician.   

Comply with part 15 of the FCC Rules. Operation is subject to the condition that this device does not cause harmful interference. Further information can be found at the FCC website or the ARRL website

Transmitting using this radio requires an Amateur Radio License. Licensing information can be obtained by visiting or In Canada, visit or


...SX-175 Final Upgrade (KIT alone)...
Magnum reports the SX175  power cabinets are discontinued.  A replacement model will not be available until early 2016.
Last info rcvd. 6-9-15

See Also:


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The RFX-150 and the SX-175 both contain the same amplifiers inside. The only difference is the size of the heatsink (fins) on each one of them. I don't know why they decided to call one the 175 and the other a 150. Both have the same electronics inside.

Think of the RFX-150 as light duty and the SX- 175 as heavy duty as far as talk time before overheating. If you talk a lot and use SSB a lot, then the SX-175 is best. If you listen a lot and use mostly AM, then the RFX-150 will do fine.


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