DAs and retention of fully-spaced assignment points

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iowegian3
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DAs and retention of fully-spaced assignment points

Post by iowegian3 » Thu Apr 24, 2014 8:48 pm

Once a station has elected DA operation, should the theoretical fully-spaced assignment point be protected going forward? I contend that it's spectrally inefficient. To specify a DA operation, a station must be able to prove a fully-spaced assignment point exists, but it shouldn't be protected indefinitely.

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Deep Thought
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Re: DAs and retention of fully-spaced assignment points

Post by Deep Thought » Thu Apr 24, 2014 10:04 pm

What is your point? Squeezing in more and more sub-optimal stations is not in the public interest. The LPFM people are finding out the hard way right now. All those waivers and stations at minimum spacing (within the interference contours of the full power stations they forgot were there) are eating them alive.
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Re: DAs and retention of fully-spaced assignment points

Post by TPT » Fri Apr 25, 2014 3:29 pm

Fm contours are based on the 50/50 (or 50/10) chart to determine coverage and interfering contours.

The charts are based on a receiving antenna 30 feet above ground, and the curves reflect signal levels at ....(drum roll please :P )

50% of the locations 50% of the time (10% on the 50/10 chart).

So, if you had a field strength meter with a dipole up on a 30' mast at a point on what is supposed to be your 60 dbu contour...you could get out your lawn chair and have an entertaining day watching the meter drift up and down, and maybe, some of the time, actually read 1 mv/m.

For that matter, sitting at the same 60 dbu contour point, you could tune in your first adjacent neighbor and watch their signal strength drift all over the place, too.

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Re: DAs and retention of fully-spaced assignment points

Post by iowegian3 » Fri Apr 25, 2014 7:23 pm

Deep Thought wrote:What is your point? Squeezing in more and more sub-optimal stations is not in the public interest.
Are you perhaps suggesting we return to the three original classes, 3 kW/300' A, 100 kW/2000' C and 50 kW/500' B? We all know that genie isn't going back in the bottle.

To restate and further illustrate my point, let's take for example a 100 kW C1, KAKA, that is short spaced by 22 km to a co-channel 50 kW B, WAAH. Azimuth from KAKA to WAAH is 45 degrees, KAKA's 34 dBu (50,10) protects the WAAH 54 dBu (50,50) accordingly.

On the opposite azimuth from KAKA at 225 degrees sits 1st adjacent class A KSOL. The distance from the fully-spaced KAKA assignment point to KSOL is 133 km, the min. A-C1 1st adjacent spacing. KSOL only covers half of its home county. The other half of the county is in the direction of KAKA.

If KSOL didn't have to protect the KAKA assignment point, KSOL could go C3, since it's 155 km between KSOL and KAKA's xmtr site. Let's take as a given that KSOL's allocation window is only big enough for an A. If KSOL only had to protect the KAKA C1 xmtr site, the KSOL window becomes a C3 opening. KSOL only needs an extra 20 km towards the NE to cover the rest of its home county, so a 9 km xmtr move towards the NE plus an 11 km gain between the class A and C3 protected contours. KSOL then would provide whole-county coverage. (Its county is one of those ignored "exurban" counties, yeah,that's it.)

But for every "deserving" situation like KSOL, there would probably be two more scenarios where a station would be squeezed in even closer to cover an already over-radioed metro market. Thus is the danger of this proposal. (Again, the DA station would initially have to prove a fully-spaced assignment point exists, but once the DA receives a license to cover, then only the actual facilities would be protected.)

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Re: DAs and retention of fully-spaced assignment points

Post by BroadcastDoc » Fri Apr 25, 2014 9:33 pm

You hit the nail on the head with this:

"But for every "deserving" situation like KSOL, there would probably be two more scenarios where a station would be squeezed in even closer to cover an already over-radioed metro market."

I'd even contend that KSOL being "deserving" is subjective.

With LPFM's and translators and everything else, the last thing we need to relax yet another rule.
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Deep Thought
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Re: DAs and retention of fully-spaced assignment points

Post by Deep Thought » Sat Apr 26, 2014 8:15 am

iowegian3 wrote:
Deep Thought wrote:What is your point? Squeezing in more and more sub-optimal stations is not in the public interest.
Are you perhaps suggesting we return to the three original classes, 3 kW/300' A, 100 kW/2000' C and 50 kW/500' B? We all know that genie isn't going back in the bottle.
I didn't say anything of the sort, but thanks for trying to put words in my mouth. :roll:

As for your example, your KSOL is licensed as a class-A to serve it's community of license and surrounding area, not a 'county'. They knew that going in. Sounds like this is more one of a bad business plan than bad engineering policy.

I did a lot of "80-90" applications 30 years ago and back then there was technical justification for "splitting" the classes, allowing class-As (probably like your KSOL) on non-class-A channels, etc. Then came 73.215. Then came IBOC. Now we have LPFMs and translators shoved into second adjacents. You really think that dumping more crap into the band is going to make it better?
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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Re: DAs and retention of fully-spaced assignment points

Post by iowegian3 » Sat Apr 26, 2014 10:26 am

Deep Thought wrote:
iowegian3 wrote:
Deep Thought wrote:What is your point? Squeezing in more and more sub-optimal stations is not in the public interest.
***My point was well stated: "Once a station has elected DA operation, should the theoretical fully-spaced assignment point be protected going forward? I contend that it's spectrally inefficient. To specify a DA operation, a station must be able to prove a fully-spaced assignment point exists, but it shouldn't be protected indefinitely." At what point should we promote a level of spectrum inefficiency to prevent co- and adjacent channel interference? At what point is such spectrum inefficiency denying service to underserved areas? That's a balancing act that's been performed ever since the FCC promulgated the original mileage separation rules in 1962. I would agree, squeezing in more sub-optimal stations isn't in the public interest. (as though the Commission was ever seriously concerned about "the public interest"..most of the time it's been more like 'PICON be gone' :( )

Are you perhaps suggesting we return to the three original classes, 3 kW/300' A, 100 kW/2000' C and 50 kW/500' B? We all know that genie isn't going back in the bottle.
I didn't say anything of the sort, but thanks for trying to put words in my mouth. :roll:
**You're welcome.

As for your example, your KSOL is licensed as a class-A to serve it's community of license and surrounding area, not a 'county'. They knew that going in. Sounds like this is more one of a bad business plan than bad engineering policy.
Did I say current engineering policy was bad? My point was that DA stations create spectrum inefficiency in the azimuths around 180 degrees away from a station the DA operation is protecting.

It could be argued that some inefficiency is desired. What if the DA loses its tower lease and needs to back up a few miles towards its theoretical full-spaced assignment point? If a co- or adjacent is squeezed in too close to the DA in question, that wiggle room for the DA is lost. If the fully-spaced assignment point is only a few miles from the actual DA, that should be protected. But ten miles between the two I would argue is too much.

Right now public policy appears to be favoring LPFMs and AM-on-FM translators. If the Commission were to do away with permanent protection of fully-spaced assignment points, perhaps those interests should be first before the expansion of full-power stations. And when it comes to the full-power stations, one would hope that consideration would be made to the number of existing services in the area of expansion.

I could talk more about those deserving AMs that need FM translators, especially out in the ex-urbs, but that's another topic...

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