Minimum dBu/mV FM signal level for building penetration

What is the accepted minimal FM signal level needed for typical building penetration? Is there a reference or source (e.g., FCC, SBE, NAB) for this level?

The FCC list the 60 dBu contour as "city grade" coverage. This coverage will penetrate most buildings.<P ID="signature">______________
You want to book the remote when?!?!</P>

But the 60 dbu the FCC shows is not necessarily the 60 dbu.

Here in hill country you better be inside the 70 dbu.

> What is the accepted minimal FM signal level needed for
> typical building penetration? Is there a reference or
> source (e.g., FCC, SBE, NAB) for this level?
>

I have never heard of nor seen any such specification. Penetration of
buildings of FM signals is more a matter of building architecture (specifically materials) than anything else, assuming the building is within a specified contour where reception would otherwise be satisfactory.

Some construction materials can be considered invisible to VHF RF, others, depending on exactly what is being considered, in combination with thickness and adjacent distance to more of the same, can attenuate and/or reflect/refract RF energy. In lay terms, steel is unfriendly to all RF (even microwaves) and reinforced concrete almost as unfriendly. However, a typical two story mostly brick and wood small office structure would probably be considered friendly.

I remember in TV ENG at 2 point something GHz, playing the bounce was often essential in getting shots out of downtown up to the tower to relay back to the studio, and even though microwave in nature, rarely being able to penetrate a skyscraper or middle size office tower and have much signal actually going through on a straight line. <P ID="signature">______________
Electricity is really just organized lightning.
~George Carlin</P>

> The FCC list the 60 dBu contour as "city grade" coverage.
> This coverage will penetrate most buildings.

If I am not mistaken, the FCC considers 70 dBu(3.16 MVm) the
"city grade" contour. 60 dBu is considered "primary" contour.
I think you need at least 70 dBu to penetrate the harder to
penetrate buildings. But 60 dBu will get you most buildings.

> But the 60 dbu the FCC shows is not necessarily the 60 dbu.
>
> Here in hill country you better be inside the 70 dbu.
>

Heck in some places down your way, you better be closer then that! Specially if your a class A<P ID="signature">______________
Lenks
Program Director/Music Director
X Music Online
The X
Today's Best Music
http://www.xmusiconline.com/</P>

> > But the 60 dbu the FCC shows is not necessarily the 60
> dbu.
> >
> > Here in hill country you better be inside the 70 dbu.
> >
>
> Heck in some places down your way, you better be closer then
> that! Specially if your a class A
>


In rural areas, with a good quality radio and antenna, what's typical reception like, in 10dBu increments, from 50dBu down to, say, -20dBu?

> > > But the 60 dbu the FCC shows is not necessarily the 60
> > dbu.
> > >
> > > Here in hill country you better be inside the 70 dbu.
> > >
> >
> > Heck in some places down your way, you better be closer
> then
> > that! Specially if your a class A
> >
>
>
> In rural areas, with a good quality radio and antenna,
> what's typical reception like, in 10dBu increments, from
> 50dBu down to, say, -20dBu?
>
40 dBu - Barely get it on a home stereo without outdoor antenna, OK in the car
30 dBu - Can't get it at home without outdoor antenna, barely heard in the car
20 dBu - May be heard with a good outdoor antenna
10 dBu and below - Can't be heard<P ID="signature">______________
17-year-old radio geek
Location: Princeton Junction, NJ
AIM: KewlDude471</P>

> > The FCC list the 60 dBu contour as "city grade" coverage.
>
> > This coverage will penetrate most buildings.
>
> If I am not mistaken, the FCC considers 70 dBu(3.16 MVm) the
>
> "city grade" contour. 60 dBu is considered "primary"
> contour.
> I think you need at least 70 dBu to penetrate the harder to
> penetrate buildings. But 60 dBu will get you most buildings.

Correct...City Grade is 3.16mV or 70dBu....60dBu is 1mV or service contour... (think of this as where you can hear it in stereo 50% of the time on a car radio and the other 50% its in mono

But there is NO definite signal level that guarantees building penetration...
attenuation through walls, etc can be 12 to 20db......or more...construction and location variables makes it impossible to come up with such a figure...
Only way to see is take a field strength meter into the area in question and see what you have...OR put an outside antenna on the roof, run lowloss cable inside then put an amplifier then "leaky" coax (like Radiax) or couplers/splitters for direct connection to a radio..

Sounds about right--depending on the channel--for flat terrain

Remember, for many stations, the 40 dbu contour is only protected against a 60 dbu contour con-channel. Without a directional antenna, guess which one wins?

Do you think given a 60 dbu and 40 dbu overlapping coverage, you can single out the 40 dbu station (from within the 60 dbu of the other)? Just wondering.

> Sounds about right--depending on the channel--for flat
> terrain
>
> Remember, for many stations, the 40 dbu contour is only
> protected against a 60 dbu contour con-channel. Without a
> directional antenna, guess which one wins?
>

> Do you think given a 60 dbu and 40 dbu overlapping coverage,
> you can single out the 40 dbu station (from within the 60
> dbu of the other)? Just wondering.
>
> > Sounds about right--depending on the channel--for flat
> > terrain
> >
> > Remember, for many stations, the 40 dbu contour is only
> > protected against a 60 dbu contour con-channel. Without a
>
> > directional antenna, guess which one wins?
> >
>
Yes, you can select which station you receive. If a station is 60 dBu, there will be some nulls less than 30 dBu. It will be possible for the 40 dBu station to come in.

Now, let me finish the scale

50 dBu - Station starts coming in on walkmen, OK at home without antenna and in the car

60 dBu - Protected coverage area, receivable on most radios

70 dBu - City grade signal, receivable even on bad radios

80 dBu - Strong signal, receivable inside concrete buildings

90 dBu - Receivable on all radios everywhere, less multipath interference in cities, station starts to overload bad radios

100 dBu - Most radios overloaded

110 dBu - All radios overloaded

120 dBu - Blanketing interference on bad radios

130 dBu - Most radios blanketed, may affect TV reception

140 dBu - It's the only station you'll get on any radio

150 dBu - It's the only station you'll get on your toaster (the tower's right next door)

200 dBu - It's the only station you'll get in your head (GET OFF THE TOWER!!!)<P ID="signature">______________
17-year-old radio geek
Location: Princeton Junction, NJ
AIM: KewlDude471</P>

Most consulting engineers I know say an 85-95 dbu signal is necessary to penetrate the concrete and steel used in most city buildings today.
I agree with this figure.