Ten-Tec Model 245 CW Crystal Filter for the Triton 540 & 544 NEW in Box

Write a Review

MPN:

245

Condition:

New

Shipping:

$8.00 (Fixed Shipping Cost)

Description

Description

Ten-Tec Model 245 CW Crystal Filter for the Triton 540 & 544 NEW in Box

Description

Plug-in PC assembly for Models 540 and 544 consists of four active, low Q op-amps. Center frequency of 750 Hz, bandwidth of 150 Hz. Two selectivity responses available with front panel control. Shape factor of 7.2 @ 6/60 dB.

Specifications

Bandwidth: 150 Hz @ -3 dB, 1.45 kHz @ -60 dB in CW-1 position; 260 Hz @ -3 dB, 2.8 kHz @ -20 dB in CW-2 position
Shape Factor: 7.2 to 1 @ 6/60 dB points
Center Frequency: 750 Hz
Input Impedance: 220 k
Output Impedance: Less than 10 ohms
Insertion Gain: 2.5 dB
Semiconductors: 2 ICs
Powered by Transceiver - +12 VDC @ 2 mA
Size: HWL 5/8" x 23/16" x 33/16"
Weight: 2 oz.

Ten-Tec Model 245 CW Filter (also called CW Audio Filter or Audio CW Filter Board) is a vintage plug-in active audio bandpass filter from the mid-1970s (introduced around 1975), designed as an optional accessory for improved CW (Morse code) reception. It is an RC active filter (using op-amps like the μA747 dual op-amp in early versions, later LM3900 quad Norton in some) that provides a peaked bandpass response centered around 750 Hz (with reduced response on either side for better selectivity against QRM in crowded bands). It mounts internally as a PC board, connecting via a 7-pin socket or designated slots, and is switched via the rig's front-panel CW filter positions (e.g., CW-2 becomes the filtered mode when installed).Unlike the crystal ladder IF filters (e.g., Models 217/218/219/220 at 9 MHz), this is an audio-level filter (post-detection), making it simpler and cheaper but less sharp than IF crystal filters. It was praised in its era for significantly cleaning up CW signals in noisy conditions.Key Details and Specifications

Type: Active RC audio bandpass filter (not crystal/IF).
Bandwidth/Peak: Peaked at ~750 Hz with a narrow effective passband (reduced response outside center; exact curves in manuals show good Q for audio CW use).
Installation: Plug-in PC board (uses existing provisions in compatible rigs; simple drop-in with wiring to filter switch).
Era: Mid-1970s (original price ~$19 USD in 1975 catalogs).
Build: Small printed circuit board with components (resistors, capacitors, op-amps); durable but parts like op-amps are now dated (replacements easy).

Compatible RadiosPrimarily designed for the Triton series transceivers, where it installs internally and enhances the CW filter switch:

Triton I (Model 510)
Triton II (Model 520)
Triton IV (Model 540 analog readout)
Triton IV Digital (Model 544)

It is also used or adaptable in:

Argonaut series (e.g., Model 509/515; often as the core board in the Model 208 plug-in CW filter accessory, which mounts externally but uses the 245 board internally).
Some homebrew or modded setups in other early Ten-Tec gear (e.g., referenced in Argonaut CW filter projects).