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Burt, K6OQK, started a topic named: "QUANTAR VHF Audio Interface"?

Since that topic has gotten lengthy and has drifted to related matters of user radios and mic settings, I thought it might be helpful to have a new topic that simply addresses the Quantar itself.

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One thing Burt said that deserves discussion is: "Regarding two-way radio, pre and de-emphasis is always a compromise,?as there really is no common standard and each manufacturer seems to have their own standard.??

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That could be a true statement if Burt had said: "Regarding amateur VHF/UHF transceivers" but to say: "Regarding two-way radio...",? That's just not so.

Real two-way radios intended for commercial and public safety applications comply with a precisely defined TIA standard.

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For example, regarding transmitters it says:

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Audio Frequency Response,? Definition:

The audio frequency response is the degree of closeness to which the frequency deviation of the transmitter follows a prescribed characteristic.

The audio frequency response from 300 Hz to 3000 Hz shall not vary more than +1dB or -3 dB from a true 6 dB per octave pre-emphasis characteristic as referenced to

the 1000 Hz level.?

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a) An additional 6 dB per octave attenuation is allowed from 2500 Hz to 3000 Hz in equipment operating in the 25 MHz to 869 MHz range.

b) An additional 6 dB per octave rolloff is allowed from 2300 Hz to 2700 Hz, and an additional 12 dB per octave is allowed from 2700 Hz to 3000 Hz, in equipment operating in the 896 MHz to 940 MHz range, and all narrowband (12.5 kHz and 15 kHz channelization) equipment.

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Then Dan Woodie stated: "I would suggest that Quantar and other repeaters of similar performance ARE the industry standard."

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True.? The Quantar definitely follows the industry standard.? Attached is an image of a test I ran on a UHF Quantar running release 14

The test was conducted using the TIA Constant Input Test Method from 300 Hz to 3000 Hz.? Instruments used were a Tektronix AM700 audio analyzer and an Aeroflex 2975 as a test receiver.

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The image shows the measured frequency response of the Quantar transmitter from the line one input and also shows the TIA limits.

In order to keep related material in one topic, here's a repost.

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The Quantar Instruction Manual, 68P81095E05-B, shows a number of interface configurations.? Typically, transmit audio is input through wireline #1.

This is an excellent choice.? It is a transformer isolated, balanced input that can be connected to balanced or unbalanced devices.? It comes preset to 600-ohm impedance

but can be changed to other values, including high impedance, with configuration jumpers.? A nominal level of -10 dBm will result in 60% deviation,

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When using wireline #1 as a transmit input, PTT is configured with a wildcard command.?

Use of wirelines and wildcard functions requires that the station be equipped with a wireline interface board.? If you have a Quantar without a wireline board, your only choice for

I/O is the 6809/MRTI interface.

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Also, since low frequency audio is not passed through the wireline input, tone coded squelch [PL/DPL] can either be encoded by the station, or - if it is desired to generate this externally?input through J17-5 which must then be configured for Aux PL Audio.

The manual is somewhat unclear about the use of J17-5 so I did some research, and I prepared the attached document for clarification.

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Finally, there is the Gen TX data +/- input which is intended for simulcast applications.? This input should be used with caution and requires the user to provide all transmit audio processing.

With this comes the risk of unacceptable transmit bandwidth.

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Also make sure that the reference modulation compensation is correctly aligned to enure distortion free low frequency modulation.