standards for avoiding interference?

[pianoplayer88key]

What are the FCC's standards on AM for avoiding interference between commercial stations?
Meaning, what contours do they try not to overlap for co-channel, first-adjacent (+/- 10kHz), second-adjacent (+/- 20kHz), +/- 30kHz, +/- 40kHz, +/- 50 kHz (and so on as applicable)? Please be conservative in your answers (i.e. if clears are protected to 0.1mV/m and regionals are protected to 0.15mV/m, say 0.1mV/m)
Also is the protection for TIS's much different? (say, if there's a TIS 10 miles from me on 1610, would I be safe putting a station on there, even if I can detect a signal (however faint) on that TIS with a Select-A-Tenna)?
I just did a check with a select-a-tenna and walkman (the combination of which is fairly sensitive, but not quite as sensitive as Bruce Carter's large loop antennas), and where i am (near 32°46'N, 116°57'W), it APPEARS that 520kHz, 880kHz, 1570kHz, 1610kHz (there's a couple barely audible TIS's though), and 1680kHz MIGHT be usable.
As I understand, 520 and 880 are too long of a wavelength for the 100mW/3m rule to be effective (anyone have experience with using the field strength rule on those frequencies - i.e. does 520 at legal field strength have the same coverage as 1700 with a legal power/antenna combo?). 1570 has a program on a station I like to listen to once a week (I suppose I could go off the air during that time, but I'd rather have it be 24/7 if possible), AND it would step on Radio Disney 1580 from Phoenix (especially since I want at least 10kHz stereo response) at night. 1610 has some TIS's on it across town, but what are the standards for stepping on those? Note that if I go directional (see below), a TIS might be in the direction of the main lobe). 1680 would be stepping co-channel on Radio Disney from Fresno at night.
I wonder which would be the best (for lack of interference AND coverage (assuming I make 5 (I understand that's the FCC's limit) transmitters (but should I radiate them all to the same antenna, or phase them and use separate antennas separated by somewhere between 10 and 50 feet? If I go with a directional signal, I basically want to throw a wide lobe west to northeast, with a little minor lobe going southeast)) frequency to go for?

 

[wkbam1690]

> What are the FCC's standards on AM for avoiding interference
> between commercial stations?
> Meaning, what contours do they try not to overlap for
> co-channel, first-adjacent (+/- 10kHz), second-adjacent (+/-
> 20kHz), +/- 30kHz, +/- 40kHz, +/- 50 kHz (and so on as
> applicable)?

Separation Class Desired signal Undesired signal

Co-ch A 0.1 mv/m 5 uv/m
B, C, D 0.5 mv/m 25 uv/m

1st adj all 0.5 mv/m 0.25 mv/m
all 0.25 mv/m 0.5 mv/m
all 0.5 mv/m 0.5 mv/m *

2nd adj all 5 mv/m 5 mv/m
all 2 mv/m 25 mv/m *
all 25 mv/m 2 mv/m *

3rd adj all 25 mv/m 25 mv/m

* many existing stations still operate under the old rules

from part 73.37

 

[pianoplayer88key]

What do you mean by "desired signal" versus "undesired signal"?

Also, please verify/correct my "clarification(?)" of the classes - A is the 50kW clears, B is the regionals, C is the 1kW graveyard locals, and D are the daytimers? Also, are these groundwave or skywave calculations?

And, are you saying the contours specified below do not overlap each other, or there isn't supposed to be a transmitter placed within that contour?

I'm trying to figure out if a few frequencies I'm looking at for a possible part 15 are "legally" usable.

<pre>
Separation Class Desired signal Undesired signal

Co-ch A 0.1 mv/m 5 uv/m
B, C, D 0.5 mv/m 25 uv/m

1st adj all 0.5 mv/m 0.25 mv/m

all 0.25 mv/m 0.5 mv/m
all 0.5 mv/m 0.5 mv/m *

2nd adj all 5 mv/m 5 mv/m
all 2 mv/m 25 mv/m *
all 25 mv/m 2 mv/m *

3rd adj all 25 mv/m 25 mv/m

* many existing stations still operate under the old rules
from part 73.37
</pre>

(P.S. How do I keep the fixed-width formatting without putting the spaces between the lines? I'm using the PRE tags.)

 

[wkbam1690]

> What do you mean by "desired signal" versus "undesired
> signal"?
>
> Also, please verify/correct my "clarification(?)" of the
> classes - A is the 50kW clears, B is the regionals, C is the
> 1kW graveyard locals, and D are the daytimers? Also, are
> these groundwave or skywave calculations?
>
> And, are you saying the contours specified below do not
> overlap each other, or there isn't supposed to be a
> transmitter placed within that contour?
>
> I'm trying to figure out if a few frequencies I'm looking at
> for a possible part 15 are "legally" usable.
>
Your understanding of the various classes is correct. These numbers pertain to groundwave daytime situations. Nightime overlap is different.

"Undesired" is the FCC's terminology for an interfering signal, and "Desired" is the signal you are trying to receive. For example, at no point on a station's 0.5 mv/m contour can another station place a signal greater than 25 uv/m. In other words, if I am Station A, and you build Station B, there can be no overlap of A's 0.5 contour by B's 25 uv/m (0.025 mv/) contour.

I just used tabs to get the spacing, but maybe it doesn't translate well to other computers.

 

[pianoplayer88key]

> > What do you mean by "desired signal" versus "undesired
> > signal"?
> >
> > Also, please verify/correct my "clarification(?)" of the
> > classes - A is the 50kW clears, B is the regionals, C is
> the
> > 1kW graveyard locals, and D are the daytimers? Also, are
> > these groundwave or skywave calculations?
> >
> > And, are you saying the contours specified below do not
> > overlap each other, or there isn't supposed to be a
> > transmitter placed within that contour?
> >
> > I'm trying to figure out if a few frequencies I'm looking
> at
> > for a possible part 15 are "legally" usable.
> >
> Your understanding of the various classes is correct. These
> numbers pertain to groundwave daytime situations. Nightime
> overlap is different.
>
> "Undesired" is the FCC's terminology for an interfering
> signal, and "Desired" is the signal you are trying to
> receive. For example, at no point on a station's 0.5 mv/m
> contour can another station place a signal greater than 25
> uv/m. In other words, if I am Station A, and you build
> Station B, there can be no overlap of A's 0.5 contour by
> B's 25 uv/m (0.025 mv/) contour.
>
> I just used tabs to get the spacing, but maybe it doesn't
> translate well to other computers.
>

Is there a place (FCC website or otherwise) where I could plug in a frequency and coordinates, and it will tell me what the calculated (or measured, if available or close to it is available) field strength of the strongest signal and what station it is? I don't have a field strength meter, and I don't know how to get an accurate calculation from an older FCC AM database viewer program I have.

A few frequencies I'm considering include 520, 880, 1570, 1610, and 1680 kHz, near 32°46' N, 116°57' W.

Reasons I would rather find other frequencies (although these seem to be the most likely usable ones) include:
520 -- would going by 15.209 at this frequency give me as good of a coverage as following 15.219 at 1700 kHz (which is unavailable)?
880 -- I'd rather have a slightly cleaner "nighttime" frequency.
1570 -- this one's fairly clean (at night, there's a mex 1200 miles east of me, but he's weak), but at certain times of the week, there's a program I like to DX on a 18-watt (ERP toward me) co-channel about 85 miles north of me. (I suppose I could go off the air during that time). Also, I would like to have good reception of Radio Disney 1580 from Phoenix. Using this frequency would make that difficult.
1610 -- Are the standards for TIS interference different? There's a TIS whose carrier I can detect (when using a Select-A-Tenna or better antenna) that's about 12 miles west of me, and I want to throw the majority of my signal in a wide northwest direction.
1680 -- Radio Disney Fresno is on this frequency at night. I suppose I could shut down during the top 30 countdown on Sunday Mornings, though...

 

[Ai4i]

> ...and D are the daytimers?

Class D stations are all stations on the six class D channels:
twelve thirty
twelve forty
thirteen forty
fourteen hundred
fourteen fifty
fourteen ninety<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>