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National Transmitter & Amplifier Model R-175 R.F. Choke New in Box

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MPN:
R-175
Condition:
New
Shipping:
$8.00 (Fixed Shipping Cost)
  • Vintage National R-175 Transmitter R.F. Choke – 800mA high-voltage multi-layer RF plate choke for ham radio amps. Genuine USA-made, tested & ready for 80-10m transmitters. Fast shipping!
  • Vintage National R-175 Transmitter R.F. Choke – 800mA high-voltage multi-layer RF plate choke for ham radio amps. Genuine USA-made, tested & ready for 80-10m transmitters. Fast shipping!
$39.99
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Description

National Transmitter & Amplifier Model R-175 R.F. Choke New in Box

National R-175 (and closely related R-175A) RF chokes are vintage/high-voltage transmitter plate chokes (typically ~145–163 µH, 800 mA rating, multi-layer design for parallel/series feed in ham radio amps up to ~3000–4000 V). They are relatively scarce.
 
 
Electrical Specifications (from National catalogs)
  • Inductance: Approximately 225 µH (original spec). Modern measured/ listed examples vary slightly due to manufacturing tolerances, aging, or minor modifications: commonly 145–169 µH (e.g., 146.1 µH, 148 µH, 150 µH, 163 µH).

  • DC Current Rating: 800 mA (continuous).
  • DC Resistance: 6 ohms (typical).
  • Distributed Capacitance: 0.6 pF (very low, helps maintain high reactance on higher bands).
  • Voltage Rating: Suitable for plate supplies up to 3000 volts modulated or 4000 volts unmodulated. Voltage breakdown to base: 12,500 volts.
  • Frequency Coverage: Designed for multi-band use with high reactance across 10, 20, 40, and 80 meter bands (and suitable for parallel-feed or series-feed in transmitters). It performs well for AM, CW, FM, SSB modes in ham radio amplifiers.
  • Design: Multi-layer (pie-wound or progressive) construction on a ceramic/steatite form for low distributed capacity and high impedance across HF bands. Not a simple solenoid.

Physical Measurements & Dimensions
  • Size (Body): 2-9/16" diameter × 6-1/8" long (approximately 65 mm × 156 mm). This is the coil winding section.
  • Mounting: Many units include a built-in mounting platform or base with standoff/insulator for chassis mounting. Some have mounting feet or provisions for vertical/horizontal installation.
  • Overall Appearance: Tall, cylindrical multi-layer choke with heavy enamel wire windings, often with ceramic insulators at ends. Leads are typically heavy wire or lugs suitable for high-voltage/high-current connections.
  • Weight: Not precisely documented, but expect ~1–2 lbs (heavy due to large wire gauge and core/form).
These dimensions make it a substantial component, typical for high-power vintage transmitter plate chokes (e.g., for 813, 4-125A, or similar tubes).
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