GTX 900 Portables and mobile TX drops out
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GTX 900 Portables and mobile TX drops out
I have 5 GTX portables and one GTX mobile in which the TX drops out after about 5 seconds on our local 900 ham repeater, which is on 927.525 RX / 902.525 TX. They also drop out on talkaround frequencies as well. (927.5, 927.6 simplex) I have searched around the board here, and havent found anything about this issue. Units were programmed with GTX RSS ver 4, and I properly hex edited the .mdf file. Any ideas?
WB4UMR
Re: GTX 900 Portables and mobile TX drops out
Are the radios VCOs adjusted correctly?
Most GTX portables and mobiles take OOB programming easily, and once realigned for amateur use, rarely fail when in service.
Check the VCO modulation level in service, as well as deviation level once you get the drop out fixed, or understood.
Check power output levels, and do NOT run the portables at max, the chassis is not large enough to remove he excess heat adequately.
You have options with the mobiles though, with the addition of a small fan.
Make sure the PA isn't cutting off due to battery issues, but since both mobiles and poratbles are suffering the same issue, it has the ring of levels being misaligned.
Run the radios into a service monitor and note the levels on TX with NO voice input, then check max deviation in TX. The service menu should assist here, as well as a test set to input audio levels when you run the RSS and use the software transmit F6 option.
Does the RX audio cut off as well, if PL/DPL is used, but not responding/opening the receiver to allow the RX audio to pass?
Is this happening on both RX and TX, or just one or the other?
900 uses 12.5 K narrowband channel spacing and 2.5 K deviation. If adjusted for any other levels, this might be where your trouble lies, as the modulation acceptance bandwidth will not allow wideband operation on any narrowband system, or radio, the audio will cut off as the modulation index is above the receiver's abiliy to detect it properly. Check THIS first, and make the appropriate changes, and test again.
Most GTX portables and mobiles take OOB programming easily, and once realigned for amateur use, rarely fail when in service.
Check the VCO modulation level in service, as well as deviation level once you get the drop out fixed, or understood.
Check power output levels, and do NOT run the portables at max, the chassis is not large enough to remove he excess heat adequately.
You have options with the mobiles though, with the addition of a small fan.
Make sure the PA isn't cutting off due to battery issues, but since both mobiles and poratbles are suffering the same issue, it has the ring of levels being misaligned.
Run the radios into a service monitor and note the levels on TX with NO voice input, then check max deviation in TX. The service menu should assist here, as well as a test set to input audio levels when you run the RSS and use the software transmit F6 option.
Does the RX audio cut off as well, if PL/DPL is used, but not responding/opening the receiver to allow the RX audio to pass?
Is this happening on both RX and TX, or just one or the other?
900 uses 12.5 K narrowband channel spacing and 2.5 K deviation. If adjusted for any other levels, this might be where your trouble lies, as the modulation acceptance bandwidth will not allow wideband operation on any narrowband system, or radio, the audio will cut off as the modulation index is above the receiver's abiliy to detect it properly. Check THIS first, and make the appropriate changes, and test again.
Re: GTX 900 Portables and mobile TX drops out
Problem was found to be related to the time out timer setting. The TX was dropping out if the TOT was set to 255. I set the TOT to 120 and it works fine.
WB4UMR