Products & Product Reviews

CW Transmissions Getting Lost in Translation? Why It Might be Time For a Variable Sequencer Unit

The folks at DX Engineering are Hams like you.

When they experience a problem in the shack or take note of an annoying glitch during an important contest, they don’t get angry—they get busy finding a solution. Why? Because if they’re experiencing trouble, it’s likely you are as well. From that philosophy arises some of the most practical, innovative Amateur Radio gear on the market.

One of those products is the DX Engineering Time Variable Sequencer (DXE-TVSU-1B). In creating this device, engineers targeted two problems that plague Amateur Radio operators:

  • Leading-edge chopping or truncating of Morse characters—a huge problem when working a pileup or transmitting during a contest. Anyone whose CW “M” was copied as a “W” or their “K” was interpreted as a “U” understands how frustrating this can be.
  • Damage to sensitive receive equipment caused by improper switch timing, or “hot switching”

To solve these issues, the microprocessor-based Time Variable Sequencer was developed to provide 0-30 milliseconds of delay, programmable in two millisecond increments, to as many as five outputs tied to CW keying or push-to-talk (PTT) lines.

Damage to linear amplifiers and other equipment caused by improper switch timing can be avoided by controlling the receive-to-transmit (and back) timing. For example, the fast relays used in the DX Engineering AVA series of receiving amplifiers, used for the active antennas, require two milliseconds of switching time. Some radios provide adequate time at the linear amplifier keying port, but many do not. The TVSU-1B turns off the receiving antennas before allowing the transmitter to come on, and only turns the receiving antenna back on after the transmitting signal is gone.

For accurate CW transmissions, the TVSU-1B delays the CW signal to the transmitter, allowing even the slowest relays to fully transfer before the radio transmits. The sequencer eliminates truncating of leading elements by slowing external relays.

Other benefits of the device include:

  • The ability to detune a transmitting antenna regardless of the speed of the relay being used (a slow relay can damage the transmitter or adversely affect signal quality);
  • Protective timing to transmitters by switching off power or providing an auxiliary timed delay to the equipment

The RoHS-compliant sequencers can also be used to control external devices, such as preamps, active antennas, or external relays that need to have power removed during transmit. Separate power-in and power-out jacks on the front panel are used to control external power. Two 2.1mm power plugs and two 3.5mm stereo plugs are provided.

Additional TVSU-1B features include:

  • Control timing of PTT turn-on, hang delay of PTT, amplifier hang delay, external antenna relay hang delay, and turn-on delay of auxiliary output
  • Dip switch settable delays of 0-30ms in 2ms increments
  • Side tone generator that follows input of keyer or hand key, not transmitter
  • Side tone pitch can be programmed from 300 to 1,000 Hz in 50 Hz steps
  • Front panel headphone jack with adjustable volume
  • Supports CW full break-in
  • Can control external power to DX Engineering active receive antennas, permitting operation in closer proximity to transmit antennas

For many more details on the DX Engineering Time Variable Sequencer, check out the owner’s manual here.

What do Hams think?

5 Stars: “I’ve used the sequencer to delay rig and amp PTT just long enough to power down the preamps on my many receive antenna pre-amps. It hasn’t let me down since I bought it three years ago. I highly recommend it!”

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