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How far can you push your micro power fm?

 
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How far can you push your micro power fm?
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dude23
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Joined: 01 Sep 2010
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Post How far can you push your micro power fm? Reply with quote
Hello all!, I love playing with the FM broadcast band. Esp when i'm located in a isolated but well populated area. It opens the doors to some "testing" that could not be done anywhere else!

Anyhow for a while, I was all into big power. For a while I had a 500 watt amp and would go from town to town and run a test from the hotel by straping a simple 1.4 wave dipole from the railing or something. Anyhow for the power, I could cover most of these cities with 20 some feet of hight from the hotel. Before that I used to try 1 or so watt transmitters from hotels where ever I would end up. But this in a city environment did not get me much more then .5 of a km in all directions. Thats like in areas where the population is in the big thousands with 100s of feet of buidlings!

So back to my home town. Its about 10 thousand in population and only a couple local stations and the rest of the band is dead quiet. I saw this 100mw usb fm transmitter dongle on ebay. I though that this could be a fun toy to mess around with. Its nice as it has its built in compressor and limiter controls via software. But it dont come close to any optimod! But lucky you can disable that and run your own software compressors.. What is nice is that the transmitter dectects as a sound card of its own but it does not show up as 24 bits. If it did then we could use various software mpx encoders /proccessors with this transmitter!

I always looked and hoped for pcs electronics for the day they would come up with a usb dongle version of their pci max transmitters but these china guys beet them to it

Anyways with all the build in proccessing turned off. This transmiiter sounds great with decent software like Sonos4. At home I have a wideband circular antenna. The downside is it has -3dbd gain as its a wideband dessign. I like that since you can pick any frequency no tune. Out where I live our winters are -40 or more soo even if my tower is only 30 feet... Its a cold climb!!

Anyways at home with this transmitter at 100mw with my -3dbd circular wideband antenna this gives me an ERP of about 50mw..... With this much power at 30 feet. I am covering my whole town! I get about 2.5 km seek and 3.5 good outdoor static free car coverage. Because im located in the center of our town. I not only cover the town but 1 km or so in every direction out of town before it breaks away 100%.

One time with a shitty chinese transmitter. These are rated at 1mw! yes thats right! With a tower of 100 some feet on a real FM broadcast antenna. We could hear the signal at over 8 km away. Of course there was more noise then signal but still.. We are talling about 1mw here or 0.001 watt of power!

Sometimes you can go up from 1 watt to 500 watts and only notice 2 or so kms of extra range while other times you could gain much more. I guess its all about local conditions and the situation. I find it fun to see how little power is needed to get out as far as some stations that run 50 watts but very bad like much more coax then they ned. Bad rated cables for swr and not well tuned antennas and most "pro" stations seem to be setup all half aaaaa So they only get a few miles when they could potentialy get much more.
Thu Feb 14, 2013 10:37 pm View user's profile Send private message
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