AM 1550 To Flip From Standards To "Vancouver's Talk Station"

[DToTheJ]

http://www.columbian.com/news/2011/apr/01/am-radio-station-switch-music-talk-format/

Looks like they're located in Portland, but they're going to gear themselves to a different market.

Now all they need is Dodgers games.

 

[semoochie]

Nighttime coverage of Portland is incomplete. Before boosting daytime power to 50KW, this frequency has always pushed its Vancouver/Clark County connection. By the way, it isn't another market. It's on the other side of the river.

 

[DanStrassberg]

Nighttime coverage of Portland is incomplete. Before boosting daytime power to 50KW, this frequency has always pushed its Vancouver/Clark County connection. By the way, it isn't another market. It's on the other side of the river.

Doesn't KPAM share the 1550 site? At its lower frequency, KPAM might well cover Portland at night as well as 1550 does, even though KPAM runs lower power (5 kW) at night than 1550 does (12 kW). So does KPAM (licensed, I believe, to Troutdale, which IIRC, is rather far east of Vancouver WA and Portland) cover Portland at all well at night?

 

[IndigoCoyote]

Dan-

KPAM is now 15kw at night. You are correct- they share the same site NE of Vancouver. KPAM at night in Portland is fine, but it is directional to the SW and you don't have to get too far down I-5 south of the city to start losing the signal. COL is indeed Troutdale, OR. Their engineer told me that the night signal does meet FCC guidelines for coverage in the COL, but not by a ton.

 

[semoochie]

It's still enough to cover the entire metro area, as far as I can tell.

 

[DanStrassberg]

Dan- KPAM is now 15kw at night. You are correct- they share the same site NE of Vancouver. KPAM at night in Portland is fine, but it is directional to the SW and you don't have to get too far down I-5 south of the city to start losing the signal. COL is indeed Troutdale, OR. Their engineer told me that the night signal does meet FCC guidelines for coverage in the COL, but not by a ton.

Thanks. I hadn't realized that KPAM had increased its night power. Must have been part of the 1550 upgrade. With the higher night power, KPAM probably does cover the market adequately at night. Although 1550 now has slightly lower night power than KPAM, the towers are more efficient at 1550 and that could just about erase the difference between KKOV and KPAM, as far as inverse-distance field @ 1km goes. (I checked, and indeed, KKOV's night RMS is slightly higher than KPAM's.) But at 1550, the signal drops off A LOT more rapidly with distance. Also the SF 1550 runs 10 kW and is directionalized to the north (pretty much right at KKOV), whereas KTRB, when it operates at night, protects KPAM. So I can now see how KPAM may cover the Portland/Vancouver WA market adequately at night whereas KKOV may very well not be able to so.

 

[semoochie]

1550 is running a lot more than a quarter wave so that should offset your figures. Still, the natural difference between coverage on 860 and 1550 far exceeds differences caused by the height of the tower. 50KW at 860 may go on for a hundred miles or so, depending on ground conductivity, whereas the same power on 1550 might not even make it out of town! On the other point, 1550 was already on the site when 860 came into existence. 860 put up additional tower(s) for their 5KW nighttime signal. Later on, 1550 put up another tower for the 12KW and a better shot at Portland. Still later, 860 reconfigured their pattern on those towers for 15KW, which now covers the area quite well! I'll try to find the electrical height of the towers.

 

[DanStrassberg]

I'll try to find the electrical height of the towers.

The towers are 81.8 degrees at 860 and 147.6 degrees at 1550. KKOV's daytime RMS inverse-distance field with 50 kW ND is 346 mV/m/kW @ 1 km, which is about what you'd expect with 150-degree towers, but the nighttime RMS is a bit higher: 369 or so mV/m @ 1km. That RMS exceeds the minimum for Class A stations (of which KKOV is not one). Normally, a high value like that requires towers a little taller than 150 degrees--more like 170 degrees, but higher values such as KKOV's are fairly common with certain directional patterns that "squish" the vertical radiation pattern.

KPAM's daytime RMS is ~303 mV/m/kW @ 1 km, which is a little high for an 81.8-degree tower. Can't attribute the high efficiency to the pattern, since the station runs ND days. Maybe the ground system is better than the usual 120 1/4-wavelength radials, although the FCC data indicates that improving the ground system does not usually improve the efficiency shown in the curves, although degrading the ground system (for example, by using shorter radials) DOES reduce the efficiency.