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TEC Line Radio Questions Answered

by Al Tatum, Technical Representative

We are often asked certain questions repeatedly about the TEC Line Radios. Here we present the most common questions and our explanations for your reference.

1. Why did S-TEC create the Sensitivity Mod for the TCR451 DME?
After the acquisition of the Microline products from Collins in 1990, we had to make application for a new TSO. Since the original design was completed, the TSO for DME's had changed and, as of the application date,a design modification for compliance was required, primarily in the area of sensitivity. Specifications of the modification are found in SIL 1-93 for the TEC Line TCR451.

2. What does Service Bulletin 17 for the VHF 251 accomplish?
(Also known as SB-11 for the VHF251E, SB-10 for the VHF251S, and SB-6 for the VHF250) SB-17 installs a modification which addresses the background of noise common in the VCO section of the Collins transceivers. This should eliminate reports of garbled, broken and unreadable transmissions between 121 MHz and 127 MHz.

3. What does SB-1 for the new VHF251A do for you?
When a VHF251A is sold as a substitute for a VHF 251, VHF251S, VHF251E, VHF250 or VHF250S, which is not up to the latest standards, several problems can manifest themselves.
1) At the end of a transmission, the release of the microphone key can cause a previously stored channel to be displayed.
2) When a 251A and a 251 share an intercom through an audio panel, the headphone outputs can be attenuated.
3) Audio distortion causing high line current can open a circuit breaker after 1 to 2 hours of continuous operation.

The modification accomplished by SB-1 for the VHF251A corrects these problems.

Please call for further clarification of these or other questions about TEC Line radios.

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