7/26/08

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Muadeeb
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Re: 7/26/08

Post by Muadeeb » Sat Aug 02, 2008 9:04 am

K9EZ wrote:
1230 (known as a graveyard channel) can be crappy 10+ miles out.. sometimes less at night. Is it one of your stations? Dave might have a point in regards to one station being slightly off frequency. I would look to see who else in on 1230 close to you and chat to see if they have had their frequency measured lately.
I had one on 1230 (1K ND) that stared fading badly at 15 mi, and another on 1400 (1K ND) at went 18. On a good day, I've heard the 1400 at 35 mi. Both stations had exceptional ground systems, and pushed 120 modulation
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Deep Thought
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Re: 7/26/08

Post by Deep Thought » Sat Aug 02, 2008 1:46 pm

It's all about ground conductivity. Only 10 miles at 1 KW on 1230 during the day is an aberration though, and speaks of a very broken antenna.

Nighttime is a crapshoot, and 10 miles is doing good. These channels were designed to serve small communities and they do that very nicely even at night.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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Shane
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Re: 7/26/08

Post by Shane » Sat Aug 02, 2008 2:57 pm

Hey Marc,

Is the hum heard on your air monitor at the studio? I'd suspect the interference is being propagated by the AC power delivery system. There may be something failing on a pole near you or something being re-radiated. Don't know if your studio and transmitter are co-located but i'm supposing not. Anyway, driving around when the interference is being noted and determining if it's only in a given area could be telling. In any case, it might not be anything you are transmitting. Sometimes it's hard to tell on AM as the receiver detectors detect everything.

I had an area in Omaha where KFAB (50kw) was getting buried by some kind of power-line-type hum right near several houses. One of those had complained to me about reception problems which was what led me to check. Never did find what the problem was, though.

Anybody charging a cell phone near the air monitor receiver? I have a somewhat elderly Kyocera cell phone which, when charging, just destroys the AM radios in the house. And the interference, while sounding more hashy than hummy, does have a hum element to it.

BTW, agreed that 10-15 mi by day on 1230 seems poor. There's a 1240 in Lincoln (ground conductivity is high: 30) that goes over 100 miles in the daytime. Granted, too, that it's using a 5/8 wave stick. I'm curious about the height of the 1230 stick that starts to fade at 15. It wouldn't get as far, I think, if it's some goofball or shorter than 1/4λ length.

~~Mike
Mike Shane, CBRE
---Omaha---

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BroadcastDoc
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Re: 7/26/08

Post by BroadcastDoc » Sat Aug 02, 2008 3:59 pm

Something I see more and more of (and I'm sure Deep Thought does as well) especially in urban areas is that the combination of deteriorating antenna systems and the rising RF noise floor is slowing eating away AM coverage. There are quite a few AM's that used to have unbelievable coverage that are just so-so now.

There is not one thing that solves the issue. It's more of a "death by 1000 cuts" sort of thing. That's why if you have an AM, you owe it to yourself to properly maintain the things you can control!
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
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