LASD East L.A. Frequency Interference

[crenshaw870]

I have a RadioShack Pro-41 analog scanner that I bought not too long ago, as a hand me down off craigslist.

I use it mainly to monitor a few LASD frequencies, as well as the Inglewood PD.

Whenever I am locked into the LASD East L.A. Dispatch Frequency of 483.2125, it is not uncommon for my scanner to also pick up a different feed.

Aside from the usual LASD Dispatchers broadcasting crime reports, and the "one-way" tone alerts when field deputies are using the frequency, I sometimes clearly hear Spanish being spoken.

I am fluent in Spanish and I have come to the following conclusion:

In Los Angeles, there is an underground Taxi Service that is run by mainly Mexican families. Their business can be seen advertised on many telephone poles, as well as the metal covers that surround the last surviving pay-phones in different parts of the city.

I am almost 99.9% sure it is them, possibly using the same frequency or one very close to it.

I hear the taxi drivers, as well as their dispatchers, communicating about a call coming in from someone who needs a ride from Point A to Point B. All of these locations are in the Los Angeles city area, primarily in the Echo Park/MacArthur Park area. At times, the dispatcher will play Mexican music for the whole channel to hear, followed by jokes and such being shouted over the channel.

I thought this interference was due to my specific location (in the Mid-City district of Los Angeles) but when I took my scanner over to my friends house in Hollywood, the same thing happened.

Anyone else in the LA area experiencing this ?

Is it just me, or is this something the LASD hasn't caught on to regarding their frequency?

P.S. My scanner only allows 6 digits to be entered for a frequency, therefore I only input the 483.212 of the 483.2125 frequency. I have also rounded up to 483.213 to see if this helps, but the same thing happens.

 

[DPD1]

It's a neighboring freq or you're getting an image of it. That last part you mention is probably the problem... The older radio can't properly reject the other freq and it's blending. You most likely would not hear them on a newer radio. That said though... I noticed Spanish coming through numerous 400 freqs the other day. If it's the same guys and their transmitter is splattering across that much spectrum, it won't be long before they're found out. If you search through 400, you'll probably find them on their actual freq they're using.

 

[LBH]

It should be an image of 461.5125. That is a conventional repeater with Spanish speaking users.

The PRO-41 is a double conversion scanner, whereas all new ones use triple conversion to help eliminate such issues. Without getting very technical, double conversion scanners can tune a slightly degraded version of a signal at twice the intermediate frequency (IF). Looking at the PRO-41 support section on the Radio Shack website, PRO-41 10 Channel Programmable Scanner 200-0301 Specifications, I see the IF frequencies are 10.85 MHz and 450 kHz. We're only concerned with the 10.85 MHz.

10.85 multiplied by 2 is 21.7. A strong image can be received 21.7 MHz higher than the actual signal. So if you are hearing something strange on 483.2125, try subtracting 21.7 MHz from that signal. In this case, you end up with 461.5125. This works in the other sections of the band, but is really only noticed due to the heavy use of the 460 MHz range and TV channel 16 for two-way radio (482-488 MHz).