Re: [IRCA] KPOJ 620 & KFXX 1080 = 1700

[Bruce Portzer <bportzer@xxxxxxxxxxx>]

Pete Taylor wrote:
> Another example was a very potent KIRO signal on 830 created by its  
> proximity to KTTH-770. It was clean audio and sounded like any other  
> station as it mixed with CKKY, occasionally with KNCO and rarely with  
> WCCO. A couple of months ago, KIRO signed off in order to clean it  
> up, allowing me to log KSPN and KFIA. Bruce Portzer told the list  
> about the KIRO signoff but we never got an explanation of exactly  
> what they did from either Bruce or the engineer whose name he cited.  
> My guess would be that they installed some sort of suppression  
> componentry on 1480. Also, there was a low-level pulsing sound on 710  
> during some of the off time which seemed to be coming from KIRO. I  
> recorded it and sent a CD of it to the same engineer. It would have  
> been interesting to find out how much power was being used. KIRO is  
> six miles from here so picking up a dummy load signal is not  
> impossible when using a Kiwa loop. The point is that KIRO was  
> sensitive about this problem and fixed it on their own.
Pete

I actually did post to this group on March 10 some follow-up info from 
John Price.  Checking back, here's what I said:
"KIRO had gone off that night to install a filter to deal with one of 
the mixing products that KIRO was creating with one of the other 50 kw 
transmitters on Vashon Island.  They also tweaked the common point on 
the antenna system.  He mentioned that the ticking sound some of us 
heard happened when they did a sweep test (which involves sending low 
powered r.f. pulses into the antenna and measuring how much comes back)."

I don't know what specific mixing combo they were trying to fix, but 
1480 (770+710) is a good guess, since it's co-channel with low-powered 
local KNTB.  I remember a couple of years ago while driving north on 
I-5, the 1480 KIRO/KTTH mix overwhelmed KNTB before I reached downtown 
Tacoma.

I'm not sure how much power the sweep tester would've put out, but I 
would guess it's well under a watt (one of the broadcast engineers in 
this group might know), and most of the power would have been radiated 
by the antenna system,

Have you noticed any difference in the KIRO mixing products since then?

Bruce. 
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