Total posts : 45366
As far as the C. Crane goes I’ve heard that the FM2 model did sound considerably better than the FM1 did and the hum was taken care of by better filtering. C. Crane did pay attention to the interference to aircraft concerns too as from I gather the transmitter’s top end is 107.5 Mhz not 107.9. This makes good sense because some of these transmitters do have spurs on the count of the BH1415 chip from Japan which has the PLL synthesizer and the limiter for the audio built in. It really was not meant to be amplified beyond its standard RF which is considerably lower than -48dbm (the amount it takes to be legal into a rubber duck). What seems to be happening with some of the transmitters is that too much voltage is applied to the chip or worse yet a wide band amplifier is put into the circuit which is causing the spurs (11 Mhz) above and below the fundamental intentional frequency. This is an issue with that design as it would make more sense to come up with a better design if you want full 250 uV/m at 3 meters. So when the “do not try this at home crowd” decides to “Hey lets turn up the power!” that poor chip is being overworked and probably generating all sorts of junk due to attempting to make an already overworked chip do what it was not designed for. Thus you have garbage in garbage out. Some of the transmitters that got a bad rap (Sainsonic AX-05B and others) is because the user is unknowingly abusing the circuit. That is why even if it ever did become legal to apply anywhere near 500mW-1W a different design would have to be employed to be sure the TX is clean. It is never good to run any TX at max power 24/7 especially as many good Hams told me you’ll ruin the TX really fast if you do this. If it were legal to have a 1 Watt transmitter and dial it down to -48dbm (or legal field strength) you would be better off. This would take into account for VSWR (antenna miss match) and would also not push the transmitter quite so hard. I’d also like to see a transmitter that would go from 0-Legal power for the times when you don’t need the extra range which too would save on the transmitter and interference to the spectrum. Yes I posted this on Hobby Broadcaster as well. Lets see the response over their as well. I’m sure Bill can’t argue this point.