Third, undocumented KFI IFB frequency?

[madscanner]

At my location in the eastern San Gabriel Valley, I am able to clearly receive KFI's IFB audio using a rooftop discone on 166.250 MHz (WPSG400) and 450.725 MHz (KPK405).

But I am also hearing the same audio on 165.335 MHz at a very weak level. Its audio is the same ~30 second undelayed audio the other two frequencies exhibit versus the 640 kHz broadcast. And yet nothing comes back for this frequency when searching the FCC ULS database. Is anyone able to receive the same signal? How strong is it where you live? I don't think it's an intermodulation product in my receiver, although anything is possible.

 

[AM909]

I show that area of VHF is government/NTIA allocated, with 12.5 kHz spacing, so 165.335 shouldn't be a valid freq.

I hear it here on 165.3375 with a service monitor and a radio, a mile or two from the KFI 640 kHz transmitter, at about -100 dBm. The RR databases says it's a Coast Guard freq. Maybe the CG is repeating it for some reason?

 

[KevinC]

At my location in the eastern San Gabriel Valley, I am able to clearly receive KFI's IFB audio using a rooftop discone on 166.250 MHz (WPSG400) and 450.725 MHz (KPK405).

But I am also hearing the same audio on 165.335 MHz at a very weak level. Its audio is the same ~30 second undelayed audio the other two frequencies exhibit versus the 640 kHz broadcast. And yet nothing comes back for this frequency when searching the FCC ULS database. Is anyone able to receive the same signal? How strong is it where you live? I don't think it's an intermodulation product in my receiver, although anything is possible.

Is 166.250 extremely strong? Your 165.335 may be 165.340, which is twice the second IF (455 KHz) lower that most scanners use.

 

[AM909]

I'm pretty sure the signal is there, on 165.3375. [i.e. that it's not an image]

 

[prcguy]

I'm hearing 165.335 very weak about -103dBm on an R8600. The 166.250 is -88dBm on the same radio, same antenna.

 

[mikegilbert]

Could be an old Marti wideband FM STL or RPU transmitter.

 

[AM909]

With a poor antenna, a couple miles from the 640 TX, with a different service monitor, I see 166.2500 at about -75 dBm and 165.3375 at about -85 dBm. Audio on both seems identical to the 450.725 audio, at least for the last few minutes.

There's a morse ID fairly frequently (like every 5 minutes), but it's pretty low dev. If someone hears it strong enough and wants to record it, we could probably filter out the human chat enough to read it. (I can't stand to listen to it long enough) Chances are, though, it might just say what I logged on 166.25 a couple years ago, which was "DE KTLA" for some reason.

 

[madscanner]

Thanks for the responses, everyone. It appears my receiver was set to 5 kHz spacing when scanning that range. 165.3375 is probably correct.

That said, 166.25 is not full quieting for me, but it is close to it. And since 166.25 - 165.3375 / 2 = 456.25 kHz, a 455 kHz-spaced difference frequency intermodulation product of 166.25 certainly looks plausible at this point.

However, with these other reports of hearing it too in spite of 166.25 being weak for others, I'm wondering if that spacing is merely a coincidence after all.

Does anyone have a directional antenna they could compare the peak strengths of 166.25 and 165.3375 with? If they peak when pointed in different directions...

@AM909 - Could you have unwittingly logged "DE KTLA" from 161.685 instead? That's KTLA's IFB. (Back in the good old days, I used to hear Marta Waller on the set, chewing out and lecturing her co-anchors on the proper ways of addressing her.)

 

[AM909]

Thanks for the responses, everyone. It appears my receiver was set to 5 kHz spacing when scanning that range. 165.3375 is probably correct.

That said, 166.25 is not full quieting for me, but it is close to it. And since 166.25 - 165.3375 / 2 = 456.25 kHz, a 455 kHz-spaced difference frequency intermodulation product of 166.25 certainly looks plausible at this point.

The 455 kHz IF image was the first thing I considered, but it would require a single-conversion receiver, which seemed unlikely. I effectively ruled that out by hearing it with three different receiver designs. It would also be 2.5 kHz off-channel from the 165.34 image freq – it's about 150 +/- 50 Hz high of 165.3375.

It's probably 25 kHz nominal bandwidth (highs start getting cut off if I set BW to 12.5 kHz).

@AM909 - Could you have unwittingly logged "DE KTLA" from 161.685 instead? That's KTLA's IFB. (Back in the good old days, I used to hear Marta Waller on the set, chewing out and lecturing her co-anchors on the proper ways of addressing her.)

It's entirely possible that I was suffering a lack of wit. However, I remember thinking it was unusual at the time. I listened for a while and it appears to have multiple IDs that are each on about a 10-minute cycle.

 

[madscanner]

The 455 kHz IF image was the first thing I considered, but it would require a single-conversion receiver, which seemed unlikely.

That was my hunch as well, since the receiver I'm using is a triple conversion model -- a Pro-2006 retired from most things except ham. But it's also pushing 35, and with my memory of the analog circuitry mechanics of single, double, and triple conversion similarly aging, I wasn't feeling confident enough to state flat out it couldn't be my radio developing some age-related senility.

I effectively ruled that out by hearing it with three different receiver designs. It would also be 2.5 kHz off-channel from the 165.34 image freq – it's about 150 +/- 50 Hz high of 165.3375.

Thanks. In that event, considering the frequency's allocation to federal users, the signal is quite a mystery. I can't imagine any reason they would want KFI's undelayed IFB audio in their spectrum. Besides, their radios would be versatile enough to program in 166.25 in RX-only mode if they really needed to hear it.

Could this be an extreme case of the "rusty bolt effect" happening at the transmitter site on account of a non-linear re-radiator right next to 166.25's transmitting antenna?

Still hoping someone with a directional Yagi can chime in.

It's entirely possible that I was suffering a lack of wit. However, I remember thinking it was unusual at the time. I listened for a while and it appears to have multiple IDs that are each on about a 10-minute cycle.

I spent some time digging. The WPSG400 license indicates that 166.25 lives at 250 Mesa Lila Road in Glendale. Google Earth shows that to be the address of the mouth of a very long dirt road leading away from a residential neighborhood into the Verdugo mountains. It eventually swings around and connects up to a radio site east of Verdugo Peak itself, whose written site description in this Glendale city document matches what I see visually in Google Earth. One of the Panoramio images at that location is labeled "Tribune Ktla TV Tlesoft Corporation" (also here).

Just a guess: KTLA has something up there, 166.25 is co-located with it, and you partially decoded "WPSG400 DE KTLA"?

 

[nd5y]

Are there any NOAA weather transmitters in the same area?
See if you can hear them in the 161.48-161.65 range.

PRO-2006s can have images about 0.91 MHz lower than the actual frequency.

 

[prcguy]

Are there any NOAA weather transmitters in the same area?
See if you can hear them in the 161.48-161.65 range.

PRO-2006s can have images about 0.91 MHz lower than the actual frequency.

Its not an image, its real. I'm picking it up on several radios here including a Harris XG-100M.