Odd behavior from MSF5000 RSS

[John G]

I recently got a 900 MHz MSF5K and after having to remove the TTRC, got it up and running. I noticed the receiver seemed off frequency. So, I fed both the signal generator I am using as a temporary reference and the 8920 from my Z3801 GPS to make sure everything agreed. I programmed it for 927.0325/902.0325 MHz. When I key the transmitter, I read 927.0300 MHz. This station has old 3.25 firmware and I thought that might be the issue. I loaded the saved codeplug and noticed that the frequency was shifted there too. I corrected it, went back to the screen where you save, saved it again and went back to the change/view screen without re reading or exiting RSS. The frequency had shifted without writing it to the repeater. I put in a legit, not out of band frequency, 935.0125, and it stayed. I am using 5.21 RSS. Any ideas?

[John G]

I didn't find the cause or a fix but I did find a work around. Don't try to program 927.0325/902.0325 MHz. I tried other frequencies and they are OK. I will just choose a different frequency for the repeater.

[MSS-Dave]

AH!! I see the problem. Not a divisible frequency by 12.5 Khz. Valid would be 902.0375 / 927.0375. Your commercial freq of 935.0125 IS a correct frequency.

Dave

[John G]

You are right, of course. For some reason, I had it stuck in my old man head that .0325 was a legit frequency. DOH!
There are other issues with this thing. I am not an old hand with these and every problem seems huge at first. For instance, in the manual, it says to set MUX bit #1 to "on". That is supposed to make it transmit. When I do that, nothing happens. Also, the receive level cannot be adjusted high enough. I have it at 99 and it still isn't high enough. And, the "flutter fighter" adjustment seems to do nothing when the conditions are set up per the manual. It is looking like this will be my first and last MSF. The RF parts are excellent but there are just too many adjustments and things to fiddle with that don't seem to work right. Is there any way to turn off transmit PL during ID? I couldn't find it, but lately, I can't seem to find my behind with both hands.

[kcbooboo]

Usually there's an address associated with a particular MUX Bit. The bits can be set with a digital metering panel or through the programming software on one of the service screens. You can also just press the front-panel XMIT switch, but that will disable transmit PL/DPL.

The TX deviation on the 900 MHz stations is +/- 2.5 kHz. Set that level first by feeding audio through a 10uF capacitor to one of the test points on the SSCB at a level that causes definite limiting. After that, set the receiver audio level in repeat mode.

Motorola's "standard" is to disable PL/DPL during the CW ID. If you set your hang time and CW ID delay accordingly, the CW ID will come out when the repeater is not in use without PL/DPL. If someone keys up during the CW ID, then PL/DPL will be generated along with the CW ID. That's the way it is. The same goes for the non-adjustability of the CW ID; there is no pot to set the level; you get what you get unless you start playing with resistor values.

I ran through six of these stations and they all worked fine and the adjustments did what they were supposed to. There are plenty of articles that you can read about other people's experiences with 900 MHz MSF5000 stations, as well as alignment and hints and tips.

Bob M.

[John G]

Thanks Bob. You certainly have more experience with these than I do. If it were a Micor, or MASTR 2, that would be different. I was trying to set that MUX bit through software. It would indicate when a bit was active, but it wouldn't transmit when I set the correct bit. Tried it several times. I followed the book when setting the maximum deviation and tried to when setting receive level but it would never indicate what the book said. I ended up sending DTMF from a HT and setting the receive level so that the repeated level matched what the HT sent. Mine definitely sends PL during ID. I wish it didn't. I don't think it sends reverse burst either. I get a squelch crash when it unkeys. The PL level is higher than I would like. Around 4 to 5 hundred Hz. I did find the resistor to fix that though. I am waiting until last to do that in case some of the other adjustments affect it again. Next is defeating hearclear, which to my ear should be called hearunclear. There seems to be more than one way to skin that cat and I am going to study it a while. The receiver is quite sensitive. And, I didn't tune it according to the book either.

[kcbooboo]

What alignment instructions are you following? Are they available on-line? I'd like to see what you're doing that doesn't seem to work for you. I didn't need very much test equipment to align the ones I had: a good RF signal generator, a deviation meter, a digital multi-meter, a digital metering panel, a tuning probe, a laptop/RIB/cables, a screwdriver, and a 5mm allen key.

I've never encountered an MSF that didn't send reverse-burst on PL. They all send the quiescent CW ID without PL but if the transmitter is keyed up then you'll get it with PL. Can't do anything about that unless you get into the firmware.

HearClear is automatically enabled on the 896 MHz band but there are workarounds.

If your PL is that loud, it sounds like your maximum deviation could also exceed 2.5 kHz.

Bob M.

[John G]

Bob, I am going by 68P81092E90-0. I used page 1-31 for max deviation, and tried to use 1-38 for receiver level adjustment. That was when I couldn't get the reading high enough. And, on pages 1-39 and 1-40, I couldn't tell that the "flutter fighter" adjustment did anything, so I left it at 53 where it already was. I also tried to do the modulation compensation adjustment that begins on 1-25 but never got that 10 Hz waveform. For the VCOs, I just centered the tuning, not having a metering panel. For the receive, I used 1-8, 1-9 but for the preselector, I just tuned for best sensitivity which ended up being .15 uV for 12 dB SINAD. My equipment is: HP 8920A, Agilent E4430B used as a temporary reference, both referenced to GPS by way of a Z3801 receiver. I also used a Fluke 114 DVOM. I looked for a reverse burst on the service monitor scope but never saw it. The HTs I am using to test with emit a squelch noise burst when the repeater unkeys. I am using an EFJ and a Kenwood so their PL decoders might not be responding to the MSF's reverse burst though the Kenwood silences quite well when listening to my Tait repeater. I want to try a Motorola but I seem to have misplaced both the programming cable and software for the MTX950. In performing talk through tests with the two HTs, I could barely hear myself when transmitting on the Kenwood, but the EFJ has way too much mike gain and tended to feedback. From what I did hear, the audio didn't sound too good. I tried telling the MSF it was an 800 MHZ station to defeat hearclear but couldn't tell much difference in the audio quality. I re checked the deviation and it is just a tad high at 2.6 KHz. That's what I run the Tait at and have never had any problems with it.

[kcbooboo]

I've got that manual here. I want to point out that the MUXBus bit you mentioned earlier is labeled A1/D1, which means Address 01, Data bit 1. This will all make sense if you have a digital metering panel or you go to the MUXBus screen in RSS when attached to the station. This bit is shown on the DMP and screen as "LOC PTT". You need to feed in a sufficient audio tone as noted in the alignment steps, 1 kHz at 1 Vrms to TP8 through a 10uF capacitor. This will cause the TX audio stages to go into limiting and you should then get plenty of deviation, which you would then adjust using either the front panel switches or the Station Alignment screen in RSS.

Regarding the mod comp, if you modified the Mode 0 / Channel 0 parameters, then things may not work properly. Also, you have to key the station via the MUXBus A1/D1 LOC PTT.

Motorola reverse-burst is 120 degrees. Some other mfgrs use 180 degrees and they aren't always compatible. I'm using 100.0 Hz PL on 900 MHz and with Motorola GTX, MaxTrac, and Spectra radios, the reverse-burst works perfectly.

The flutter-fighter adjustment isn't something you'll necessarily notice.

As far as HearClear goes, voice audio may sound different if the user radio has it enabled but the repeater does not, or vice versa. Also, if two users are communicating and one has HearClear and one does not, you may hear a difference that way. The repeater could operate without it and the user radios might not notice, but when the signals get weak and noisy, it could make a difference.

You really need the right equipment to set up the station properly.

Bob M.

[John G]

I don't have a DMP. I was using RSS to set the bit. If the station ID'ed, the bit would show active. When I set it active with the RSS, it showed active but never transmitted. I did the max. deviation adjustment like the book and you both said. I didn't have any issues with that. I didn't use channel "0" because there is only one channel programmed and that is the only one that will be used. And, setting that MUX bit didn't cause it to transmit so that is probably why I didn't get my 10 Hz waveform. Other than not having a DMP, which I doubt I will ever have, I believe I have most everything I need. Actually, in a lot of ways, our lab is better equipped than most two way shops.

[kcbooboo]

If the PTT Qualifier in the mode/channel screens doesn't have "L" for LOCAL PTT, the station probably can't be keyed via that MUXBus bit, something Motorola managed to leave out in all the documentation. That's the field that lets you enter DLMRW for data, local, mrti, repeater, wireline.

Mode/Channel 0 is normally setup by RSS with tuning/alignment values, and you have to manually select that mode/channel to do the mod comp adjustment.

Bob M.