Jost for fun I plugged the following values in:
Power:0.0000002
Ant Gain: 0.0
Transmission Line Loss: 0.0
Transmitter Antenna Height above Ground: 1 m
Receiver Antenna Height above ground: 1 m
Frequency 98.1 mHz
Signal covers about 13 homes or about 300 feet from the transmitter.
But the green zone there (43.5 dBuV/m, or 150 uV/m) looks like it extends over a lot more area than would be expected for a transmit system meeting FCC 15.239.
No problem to me, but maybe it could be to an operator wanting to comply with FCC 15.239.
Rich said: But the green zone there (43.5 dBuV/m, or 150 uV/m) looks like it extends over a lot more area than would be expected for a transmit system meeting FCC 15.239.
I said: Agreed. I was a bit surprised as well. I looked at the data that I plugged in and that's what it ran. Except for an interference complaint, I don't see the FCC driving slowly thru this neighborhood. 🙂
Maybe check on the applied power needed to produce 250 uV/m 3 meters from that transmit antenna.
I don't see the FCC driving slowly thru this neighborhood. 🙂
I hear that Ralph Barlow might be availlable.
I hear that Ralph Barlow might be availlable.
He actually drives by my town to get home and to work every day.
using 0.000000012 for power. It looks the same. This may support claims of ranger greater than 200 feet? Back in the day when I did part 15 compliance testing I could hear Class A digital devices sometimes over 300 feet away.
using 0.000000012 for power. It looks the same.
Don't know what L-R software you are using, but the difference in the transmitter power given in the OP and in Reply 6 is about 24.4 dB.
Other things equal, that will produce a 24.4 dB difference in received fields. If they look the same to you for those two powers - something unknown is going on with those analyses.
From what I understand it only takes between 11-18 nano Watts to equal a field strength of 250 uV/m @ 3 meters. Although Brian from Whole House FM Transmitter said their output to the final stage was just less than 100 mW. Again that part is questionable depending on their rubber duck antenna that they are using due to the cheap ness of some of these transmitters. Even the coupler which connects the antenna to the RF stage has to be considered too. Its my experience these transmitters less that $200 they don't put any more into them than they have to. But getting back to the strength and range I'd try a figure of 15 nW into the simulator and see what you get. The C. Crane has been reported as high as 18 nW out but as Carl has said the coupler is very poor so by the time the power gets out to the antenna you may only see 1-2 nW. The Sainsonic AX-05B at least has a very good solid TNC connector which is even more secure than a BNC. Its close to a PL-259 but it has the plastic or whatever inside like a BNC but instead of spring push and turn you align the antenna straight up and screw it in for a nice secure fit. At low power the SainSonic is -48dbm at High power that is questionable. I know that -48dbm is far more legal that the other so I'd go with that input for the simulation. Maybe if I had put the transmitter 30 feet in the air at that level I may have reached 3-4 houses down I doubt 13 maybe in a high sensitive car Radio. Now on high it does reacy about that distance. Really about the end of the road here. So try the figures and different height and see what you get. It just may mean we have to mount our FM transmitters outside like some of you do with AM. Maybe just use Bluetooth as an audio link and solar batteries for the power. But how to you turn the transmitter off during the temperature inversions? You'd have to rig some sort of remote power. The SainSonic will resume transmission when the power is restored. One way I found to make it not go to the bottom frequency when power is restored is this: Hold down power and plug in the unit. You'll see a L or H. If you want low power just press the down arrow. Out of the box it should be at low power (Mine Was). Now press power and you'll see the highest frequency adjust that to the frequency you want to transmit on. Press power and you'll see the low frequency. Adjust that to the frequency you want to transmit on and press power. The transmitter will turn off. Now power it back on and it will be LOCKED on only your transmit frequency. This is good to do if you have kids around as they can't change the frequency. Now you can put it into a water proof case and rig it for audio. A remote power on and off and you hafe a transmitter you can turn off at 6PM to check for an inversion. This is very important to follow this rule. After 6PM to 8PM once per hour and after 8PM once every ½ hour.
Below is the plot I get using another L-R program.
Details:
- Tx antenna radiation center = 1.5 m AGL
- Rx antenna radiation center = 2 m AGL
- Antenna Power = 1 mW (pgm wouldn't accept powers in the nW range)
- Earth Conductivity = 5 mS/m, d.c. 15
- Vertical polarization
Color Code
Dark red = > 70 dbµV/m
Light red = 60 to 70 dbµV/m
Grey = 45 to 60 dbµV/m
A field of 45 dbµV/m = 178 µV/m, approx.
From this it can be seen that a "Part 15 FM" transmitter even with ~ 1 mW of output power to a simple antenna can produce fields that are far in excess of FCC §15.239.
