Hmmm - I disagree with the distance figures
Using the ITU-T coverage grade field strengths, the maximum distances under ideal conditions for an LFPM station are:
Urban Grade Stereo = 2.5km
Rural Grade Stereo = 10.0km
Mono signal = 20.0km
These can be calculated using the following:
Max eirp = -3dBW (500mW)
Obstruction loss = 0dB (I did say ideal, after all)
Field strength = 77 + [eirp in dBW] - (20 x Log(distance in km) ) - [obstruction loss in dB]
The ITU coverage grade limits are:
Urban Grade Stereo = 66dBuV/m or better
Rural Grade Stereo = 54dBuV/m or better
Mono signal = 48dBuV/m or better
If you add in some obstruction loss of say 6dB then the distance figures become:
Urban Grade Stereo = 1.25km
Rural Grade Stereo = 5.0km
Mono signal = 10.0km
Pure maths. Nice and simple :-)
And the above doesn't even take into account improvements in receiver and antenna design since the ITU set the coverage grade guidelines.
Diversity receive antennas - as fitted to quite a few vehicles these days - can easily add 6dB improvement in usable sensitivity. Or improve mono performance by another 20km (under ideal conditions).
Likewise, band expanders - also fitted to quite a few vehicles - can destroy 10dB of sensitivity
This equates to knocking back the mono performance from 20km to 6km (under ideal conditions)
If you're only attaining 2km then maybe your eirp is low ?? Do a power measurement at the antenna input.
Or you have a radio with a band expander ?? Throw away that crappy band expander! Get a real radio.
Ot you have a single antenna receive ? Get diversity, it's great.
Or you have some obstruction loss? (trees, buildings, etc) Raise your Tx antenna to avoid this as much as possible.
Enjoy my ramblings, I'm of to get some lunch now
>>> DuffyFamily@... Tuesday, 9 August 2005 8:47:11 p.m. >>>
Ross is absolutely right.
It is 500mw at the aerial.
For my station its pretty easy to figure out, you don't have to work for NASA.
980mw at the tx, 20mtrs of rg58 just about wipes that out and any theoritical gain of a folded dipole brings it up the limit.
It is fairly easy to see who is running more power than they should.
Example if you drive more than a couple of km's from where you live you lose my station.
2 km's is the maximum you can resonably expect to get staying within RSM 29 specs.
Sure mono might double that to around 4 km's but you just can't propogate a 500mw signal further than that. (legally that is)
I use a 1 watt pro3 tx and pro 3 encoser.
The reason 88.1 to 88.5 for the 300mw pro3 tx is simple. When that tx was first built to conform with RSF29 those were the allowable freq.
The advertising is stating the freq that can be used not what it can run at. All NRG tx's are tunable across the entire broadcast fm spectrum.
M.B.D
From: Mark O'NeilTo: LPFM_Radio@...Sent: Tuesday, August 09, 2005 8:05 AMSubject: [LPFM] Query on NRG Pro 3HI All,After surfing to www.nrgkits.co.uk I found the PLLPRO3-1K to be interesting, does this unit do 88 - 108mhz , I ask as The 300mw version for rfs29 says 88.0 - 88.5mhz
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