Maybe Timinbovey was using Fords so that's why he got the range he tested!
How's the FM on those same radios?
Mark
There is a lot of talk about signal range on FM.
I read through the comments, but fail to see any mention of a neighbor with an outdoor VHF/FM television antenna with in line signal amplifier pointed at your house.
I would like to see some discussions regarding that possibilty.
Also, I wanted to add, that some FM transmitters can broadcast in mono, that type of signal should carry a bit futher than 200 feet, not much of course, but a little bit further.
By the way, very educational topic guys, I'm learning a few new things here reading the comments.
Bruce.
Running mono about doubles usable range.
FM reception is great on the Carolla with the factory radio, though it is slightly directional. The Delco ETR in the 82 pickup has good FM reception and decent selectivity but isn't as good as the Carolla. AM on the Delco is actually pretty good and is pretty wideband but I have an engine noise problem that is ruining it at the moment. The sound quality of the Delco is simply amazing even on Cassette, I don't even have to use the DNR switch!
I'm not correcting Mr. Bruce here, because he probably already knows this... but a lot of people don't. There's this misconception that a mono FM signal will get out better than a stereo signal. That's not true at all. But... and I think this is what Mr. Bruce was talking about... a signal received in mono will generally be quieter and cleaner on the fringes. There will be less noise and far less multipath.
However, you can broadcast in stereo, and if the listener's receiver is mono, it makes virtually no difference if your transmitter is shooting out a signal in mono or in stereo. (Technobabble alert: if you don't reduce your total modulation to allow for your stereo L-R 19 kHz pilot, then your S/N ratio on the L+R portion will be identical to the "ears" of a mono receiver whether you broadcast in stereo or mono.)
marosborne Said:
But... and I think this is what Mr. Bruce was talking about... a signal received in mono will generally be quieter and cleaner on the fringes. There will be less noise and far less multipath.
MrBruce Said:
marosborne You are correct, that is what I meant.
A weak signal in stereo has a hiss in it, when the stereo light comes on, if you have the ability to turn off the stereo transmission (At the transmitter) and go mono, the hiss goes away at that same distance.
Bruce.
Clip from Reply 12 above:
... And of course nowadays all the car radios seem to be rated in dBf rather than uV just to frustrate us.
The term "dBf" refers to the r-f power present across the input terminals of a receiver, relative to a power level of one femtowatt.
The reference to power, rather than voltage, removes the variable associated with the input resistance across which the incoming r-f voltage is present.
Below is a clip from an Excel spreadsheet showing a typical? set of values.
| 20 | dBfW | equals | -100 | dBmW | |||||
| uV/m = 10^[(dBm - G + 20*logF + L +75)/20] | |||||||||
| where | |||||||||
| -100 | dBm = signal level at receiver input in dB with respect to 1 mW, or | 0.00000274 | V across 75 ohms, or | ||||||
| 0 | G = receiving antenna gain in dBd | 2.7 | uV across 75 ohms | ||||||
| 0 | L = line loss in decibels | ||||||||
| 99.9 | F = frequency in MHz | ||||||||
| 5.62 | uV/m field required | ||||||||
Transmitting in mono forces all recievers to recieve in mono and thus reduces the percieved noise. Switching a reciever to mono mode produces the same result but don't assume listeners have this abilty or know how to use it.