L.A. Harbor - what is source of new interference?

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SweetPee

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Joined
Jan 28, 2008
Messages
7
Location
Los Angeles Harbor, California
Hi All,

I am new to scanning, and have a Pro 97 scanner. I was wondering if someone could help me figure out the reasons for the recent interference I'm encountering lately.

I have a list of 48 voice frequencies used by one of the terminals I work for on Terminal Island at Los Angeles Harbor. I got this list by using one of their handheld radios, a Motorola "HT 1250" (all the radios there are Motorola) to activate a channel so my scanner could pick it up, and then writing down the frequency. At the terminal, there is one frequency per channel. I have all 48 frequencies programmed into their respective channels in "Bank 2" in my scanner. Each channel has anywhere from about 4 to 8 or so voice users. I have no idea what kind of radio "system" is being used other than it is "conventional".

http://www.radioreference.com/apps/db/?action=fle&stid=6&en=MARINE TERMINALS

The frequency I am most interested in - 469.087500 - has a "DPL" code also. I have programmed the frequency and it's DPL code into a separate bank as well as in "Bank 2" on my scanner for when I don't feel like hearing everything else. I monitor from either right there at work, or from a distance of about a quarter mile away when I'm not at work. In either case I get heavy interference on this one frequency, the speech being "chopped up" into a rapid, intermittent stream of very legible speech/nothing. Often, if someone from one of the other channels calls my "target" channel, I can hear the caller with no interference, but I either can't hear my target's response at all or it is very choppy. Is this what plain analogue interference sounds like? This interference hasn't occurred until recently, and it only occurs on this one frequency.

Those calling my target channel are often using a fixed mounted "desk" type radio with a microphone, but they are not inside a building, they are "mobile". Those on the "target" channel only have hand held radios, and they move around a lot too but are sometimes inside a building. All the other channels are fine. I've heard that there are "boosters" placed around this terminal to enhance the signals. Apparently the radios have a feature for "MDC 1200" - could this have recently been turned on, causing the choppy reception? Or maybe it's just someone on my "target" channel with a bad radio……?

Is there any one who could help me narrow this down a bit?

Thank you…..
SweetPee

L.A. Harbor,
Pro 97 Scanner,
"Rubber Duckie" Antenna,
Radio Shack Metal Telescoping Antenna #200-006A
 

ecps92

Member
Joined
Jul 8, 2002
Messages
11,470
Location
Taxachusetts
Have you listened to on the Scanner and Searched in the Database for someone licensed/using an adjacent channel ??

ie: Your Frequency is 451.3875, take a listen to 451.3750 and 451.4000, I'll be your interference is an adjacent frequency if it's chopped.

Since you licenses are 2 watts, that is probably it. Let us know what you find out.
Which frequency gets the interference ??

Hi All,

I am new to scanning, and have a Pro 97 scanner. I was wondering if someone could help me figure out the reasons for the recent interference I'm encountering lately.

I have a list of 48 voice frequencies used by one of the terminals I work for on Terminal Island at Los Angeles Harbor. I got this list by using one of their handheld radios, a Motorola "HT 1250" (all the radios there are Motorola) to activate a channel so my scanner could pick it up, and then writing down the frequency. At the terminal, there is one frequency per channel. I have all 48 frequencies programmed into their respective channels in "Bank 2" in my scanner. Each channel has anywhere from about 4 to 8 or so voice users. I have no idea what kind of radio "system" is being used other than it is "conventional".

http://www.radioreference.com/apps/db/?action=fle&stid=6&en=MARINE TERMINALS

The frequency I am most interested in - 469.087500 - has a "DPL" code also. I have programmed the frequency and it's DPL code into a separate bank as well as in "Bank 2" on my scanner for when I don't feel like hearing everything else. I monitor from either right there at work, or from a distance of about a quarter mile away when I'm not at work. In either case I get heavy interference on this one frequency, the speech being "chopped up" into a rapid, intermittent stream of very legible speech/nothing. Often, if someone from one of the other channels calls my "target" channel, I can hear the caller with no interference, but I either can't hear my target's response at all or it is very choppy. Is this what plain analogue interference sounds like? This interference hasn't occurred until recently, and it only occurs on this one frequency.

Those calling my target channel are often using a fixed mounted "desk" type radio with a microphone, but they are not inside a building, they are "mobile". Those on the "target" channel only have hand held radios, and they move around a lot too but are sometimes inside a building. All the other channels are fine. I've heard that there are "boosters" placed around this terminal to enhance the signals. Apparently the radios have a feature for "MDC 1200" - could this have recently been turned on, causing the choppy reception? Or maybe it's just someone on my "target" channel with a bad radio……?

Is there any one who could help me narrow this down a bit?

Thank you…..
SweetPee

L.A. Harbor,
Pro 97 Scanner,
"Rubber Duckie" Antenna,
Radio Shack Metal Telescoping Antenna #200-006A
 

DPD1

Member
Joined
Jul 24, 2005
Messages
1,994
Hard to know without hearing. Maybe you could post a clip somewhere with the squelch both on and off while it's doing it.

Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
 

ecps92

Member
Joined
Jul 8, 2002
Messages
11,470
Location
Taxachusetts
Missed that the first time.

Put your Scanner on 464.0750, 464.1000, 469.0750 and 469.1000 see what you hear.

If you also click on your link, then click on the Call-Sign a nice RR Map Appears
http://www.radioreference.com/apps/db/?cs=KD53766
Once the map is loaded scroll down to the Lat/Lon and click on one of them.

A NEW Feature of RR is a Radius Search,. this will show you all the licenses
within a radius [expand out]

Also looking at that Frequency itself , there are plenty of FAST FOOD licenses. How about the local Mickey D's.

My advise is to drop the DPL on your Scanner and listen that way, there could be plenty of other users
near-by on a different CTCSS or DPL too...

How about making an Audio of it ?

We are all just speculating w/o actually being there.


Are you sure it's not repeated, and you should be listening to 464.0875?
 

SweetPee

Member
Joined
Jan 28, 2008
Messages
7
Location
Los Angeles Harbor, California
Please forgive me for not getting back here until now after I posted a request last Friday asking for advice. Right after I pushed "send", I found my dog in a an emergency situation and rushed her to the vets. It was a long weekend but I can relax now, she is going to make it. My apologies for being rude......

I too suspect there are repeaters at the location of my frequency and not just "boosters". Do "conventional" radio systems use repeaters? I do know the line of sight between myself and where I THINK the transmnission is coming from is not 100% clear - there are some 2 story buildings between us. Sometimes a cargo ship will come and park itself right in the middle of the line of sight and that ends my monitoring session . But otherwis I'd say the line of sight is maybe 75% unobstructed.

I will be worknig on all the suggestions you gave about listening to adjacent frequencies, etc.....this will contribute to getting better acquainted wiht my Pro 97 too....

Thanks for the heads up on the new Radius Search feature - I'm anxious to try it. I know a lot of adjacent terminals are licenced for a lot of the same frequencies as my workplace, because I can watch the DPL number changing when the conversation changes - it is all "industry" conversation, from several different termianls. They bump me off the one I want to listen to.

I will do my best to get a clip to post.....would a small tape recorder be sufficient fore collecting the clip?

I'll put those adjacent frequencies in the scanner tonight for tomorrow and let you know what I hear.

Thank you again for all the tips to try....and again I apologise for not posting back until now.

SweetPee
 
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