[BC] RE: FM Power Amplifiers

[Jeff Welton]

Mike (I'm still recovering from German pancakes!) McCarthy commented:
 
> Also, there may be issues in the LPF. I recall reading in the Nautel FM > series manual about retuning and there were also some minor component > changes in certain stages as well. I can't say anything to that effect on > the V series boxes except the RF jumpers. But the V series are in three > overlapping ranges just like the FM series which it succeeded.
With the FM series transmitters, the low pass filter was tuned to the specific carrier frequency to provide higher turnaround loss and better rejection into channel combiners.  For the older 4 and 7 kW transmitters, there were two bands - changing from 88-98 to 98-108 or vice versa required replacing the LPF.  For the FM3.5, 5, 8 and 10, only one filter configuration was used - it was simply a matter of retuning to the correct frequency.  In addition, all of the PA's and the IPA(s) had to be retuned, cable sets for RF cables were frequency dependant and all of the critical parameters for transmitter protection needed to be reset - a frequency change is a full 8-12 hrs for somebody that has a good idea of what's under the hood.
 
In the V series, for analog configurations, the transmitter is fully broadband - no cables to change, no overlapping ranges (I'm not sure where you saw this Mike, but if you could send me a reference I'd appreciate it!).  Frequency change is simply a matter of dialling the correct frequency into the exciter.  We sell this unit a lot for N+1 applications, where you can have one transmitter backing up as many as six stations, by programming the appropriate frequency and power level for each station into one of the six presets in the transmitter and M50 exciter.  Then connect the transmitter into a separate, broadband antenna - if one of the main transmitters fails, select the appropriate preset and hit the ON button on the backup.
 
There are upsides and downsides to new vs. old configurations.  Not needing to tune power modules when repaired and having N+1 frequency agility is an obvious plus.
 
Also, our website seems to be lacking when it comes to figuring out what's available - we currently have V1, V2, V3.5, V5, V7.5 and V10 in the stable and have combined V10's to provide 20, 30 and 40kW transmitters.  Incidentally, the V1 and V2 are rated by hybrid HD output - they will do 1.4 and 2.8kW of analog power, respectively.
 
At this point, I'm starting to transition from a transmitter configuration discussion to a sales talk, so I'll be happy to provide any more information required offlist!
 
Best,
JeffJeff WeltonTechnical Sales RepresentativeNautelToll-Free: 877-662-8835, ext. 127Cell: 902-489-1635jwelton at nautel.com Making Digital Radio Work
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