900 MHz Spectra-II RX Audio Levels

[kcbooboo]

Most 900 MHz Spectras have HearClear circuitry in them, either as an option board or built into the command board on the Spectra-II (E-series) radios. This question is primarily for the Spectra-II. HearClear is called "compander" on the Spectras and is only available on 900 MHz. Also, these are narrow-band radios (2.5 kHz deviation/bandwidth).

I programmed two channels on the same frequency: one with HearClear enabled, one without. If I feed an FM signal into the radio with a 400 Hz tone at 1 kHz deviation and set the volume for a comfortable level on the non-HC channel, it sounds fine. If I then switch to the HC channel, I'm blown out of the room. The speaker audio is about 20dB louder. Even at minimum volume it's still too loud to listen to. A regular Spectra (one with the separate option board) is much more evenly balanced, and while the levels aren't exact, I can live with it.

A similar test on MaxTrac and a GTX mobile radios show them to be nicely balanced. It's just the Spectra-II radio that is so out of whack.

Anyone ever heard about this or know a fix for it? A workaround is to NOT use HearClear, but I'd rather use it if the radio has it.

Bob M.

[RADIOMAN2002]

I personally don't like the Hear Clear audio, it makes it sound more like a recovered digital transmission. I don't have an answer on the Spectra II, possibly an tuning adjustment in the software? Also from the info I have read you need it to be set or not set on the repeater and the mobiles, or the audio doesn't sound right. Could be since the radio is not going through a M repeater with it turned on that you are having problems. Also using a constant tone might be screwing up the sampling in the compandoring board. Try both settings on a radio channel with normal radio traffic, that's how I compared mine on a 900 ham repeater and decided to remove it.

[Astro Spectra]

Isn't there an alignment softpot for the hear clear level? I think HC works well in a 12.5 kHz system provided both ends are properely set up.

[kcbooboo]

I didn't check the alignment screens but I don't recall reading about any HearClear level adjustment in either the Basic Service Manual or the RSS manual. I'll run the radio up and take a look.

Bob M.