Batboard

Ok, So it is a weird header, let me clairify.

A UHF range 2 quantro was moved up to range 3 by way of a new exciter and reciever modules. Box was re-initialized to reflect the new modules.

The unit was also reprogrammed from 25 kc to 12.5, we think that we caught all the little settings in the software.

The pre selecter was tuned as per the service manual and the radio now has .11 sensitivity.

The box is running mixed mode and sounds great in the P25 realm, However.

The analog side of the radio sounds horrible. The voice quality is ok, however it sounds like there is white noise under everyones transmissions, unless you are completely full quiting into the unit. It sorta sounds like you are constantly on the fringe of the repater, when you are not even close.

We have checked the obvious, 10 db station master, brandy new Decibel 6 can duplexer (OK on monitor), 1 1/4 hardline sweeped (OK) less than 1 watt relefected.

So, We beleieve that maybe we are missing something on the set up or programming of this unit. Any one else have this experience?

Also, The software made mention when changing from 25 to 12.5 that is was recommended that a internal or external UHSO be installed for optimum performance? Why? Could this be a problem?

Thanks, Rob

methinks that your rx module is on the frtitz - either by software setup or by inherent problems....

of course, the only way to tell for sure is to replace the rx module.....




doug

I sure hope not, we waited three months to get it from moto (backorder). It was or is a new module.

What....Don't you believe brand new modules can be shipped even if they're Defective? You've got to understand there isn't a full-time /\/\ employee checking these modules anymore...as they're ALL outsourced contractors as of January 1, 2006. And contractors don't give a rats ass if the product works or not, just make the Production numbers. On top of this issue, your modules are a Parts Order not a complete station.

I'm concerned about your Receiver Sensitivity of .11uV at what reference....20 dB Quieting or 12 dB SINAD? That low of a level almost sounds too hot and since you haven't mentioned whether this Repeater is on a VHF or UHF band, I'm not going to second guess you.

Have you checked the Desense level into a good known 50 Ohm load and then the Station Master Antenna? Come to think of it, "Are you using an Out-Of-Band High Power RF Anplifier on this repeater station?" If so, "How does the RF Spectrum appear on the initial Key-Up and while it's transmitting signal?"

Dan

Speaking of the P.A., I've seen the external Quantro amps generate noise due to the substrates burning up. A good test would be to bypass the amp and run on exciter power. See if you still have noise.

If not, then you should check for desense using an iso-tee. Put the iso-tee in series with the rx. Generate a signal to give you 12 dB SINAD with the repeater not keyed. Then key the transmitter and see if the SINAD level changes. Measure how much more signal you need to provide to get back to 12 dB SINAD and that is the amount of desense you have.

Another thought, since this was band changed, are you using a circulator?

I've see typically around .23 to .27 uV for 12 dB SINAD on UHF R3 stations. Spec is .35 uV I believe.

Guys, Thank you for the replies...


Here is some other info.. The repeater was a UHF range 2 and was no converted to a range 3.

The external power amplifier is a range 2, but as you know is the same from an MSF5000. You can take a 450-470 msf and tune it up to the 480 without a problem, so I would assume no problem there.

The RX module was tuned as per the directions in the service manual, which resulted in .11 sensitivity. This was done while generating a signal and reading dip/peak with another monitor in the spectrum analyzer.

I thought .11 was to hot, and our local guy says that he doesn't see them tuned that hot, and that .25-.3 is where it should be, otherwise there could be problems. He said he tunes it via a speaker from the SCM using the 12 db sinad (i think that is what he stated).


The circulator from the R2 unit was kept in. When tested on the monitor for our freq it posed no issues. It worked well with only about 1 db of loss.

I've had power supply fans induce white noise on the outoing audio carrier, so you may want to access disable the station until the PS heat sink cools down and the fans turn off, then key it up locally and see if the noise is present with the fans off vs. with the fans kick back on.