any Harris MW1A folks here??

[Imlivinontheair]

Does anyone out here have any suggestions for processing for an MW1A that will sound good and perform well?

Does anyone have a good unit for sale?

Feel free to post or PM me.

Thanks!

 

[frankberry]

The MW1A should be able to handle just about any modern processing. The transmitter had very high IPM, making unsuitable for AM stereo but it's AM performance was quite good.

 

[RadioMan203]

The MW1A should be able to handle just about any modern processing. The transmitter had very high IPM, making unsuitable for AM stereo but it's AM performance was quite good.

I had an MW1 (not the "A" version) at one station I engineered and it was running Kahn AM Stereo when I arrived. It sounded quite good, first running an MOR format and later when the station switched to oldies. I don't know how the box would have handled C-QUAM but it did a respectable job otherwise.

 

[frankberry]

The Kahn system was an independent sideband stereo system. IPM was not a problem. C-QUAM used a touch of frequency modulation for the L-R audio. The transmitter's Incidental Phase Modulation performance was very important.
All in all, the MW1A modulated very well. It would easily do 125% positive modulation.

 

[RadioMan203]

@frankberry: Thanks for the clarification. I've never dealt with the Motorola in a working environment nor was I aware that CQUAM had anything that resembled phase modulation.

The MW1 did perform quite well and probably would have done much more than 125% positive if pushed. In contrast, the RCA BTA-1R I had as a backup would chug along without any problem but it didn't modulate anywhere near as well as the Harris box.

 

[BobRadil]

I worked for a station doing C-QUAM with an MW-1A. It worked and sounded nice except the out of band stuff was a little above the 73 db. limit. I switched it mono before doing the NRSC bandwidth measurements. It helped. I never put it back on. No one noticed. Tweeking the IPM also helped.

Another "issue" with the MW-1As is the feedback loop. The RF is sampled and rectified and the audio and DC componant is negatively fed back to an early stage to improve linearity. Problem is it's sampled at a later point in the output network. Sideband asymmetry caused by a narrow load is rotated a bit as a result, causing distortion in the diode detected sample. This then causes predistortion, and its resulting splatter, to be in the output signal generated by the transmitter. A better sample point would be at the point between the 2 RF transistors on all the PA modules and the result resistively combined and fed to the early stage.
I guess I'm around 35 years too late with this suggestion!

 

[Unregistered]

MW-1 Guy

A little late to the party here but, for some reason I was never able to keep the PA modules in an MW-1or MW-1A running for more than 6 months when using the Inovonics 222 limiter/filter in front of it without loosing audio pass transistors and/or the TIP-47 TO-220 devices. In contrast, any modern NRSC filtered Orban product that I've used in front of an MW-1 or MW-1A never exhibited the problem and the transmitter would run for years without any failures other than what could be attributed to a power surge or lightning strike. Never did make a determination as to why that particular processor had this problem consistantly with numerous MW-1's and other processors did not. Oh Well! That was 20 years ago in another life when I was a contractor. I also had good luck with the last production run CRL gear, the PMC 450 and 900.

IPM is an issue with these transmitters, as is the symmetry of the PA module waveform. You'll want to have your RF devices properly matched for beta and verify the PA output with a scope for both symmetry and rise times of the Class D squarewave. Anything else will result in poor PA efficiency and increased IMD in the audio. The MW-1 and MW-1A is still a favorite transmitter of mine and I would have no problem running one up against any other 1 KW AM box out there. My 2 cents worth.