Anyone else heard QRM on 146.490?

Discussion in 'Ham Radio Discussions' started by VA7KBH, Aug 26, 2002.

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  1. VA7KBH

    VA7KBH Ham Member QRZ Page

    Hello all,

    I posted this here because I know that most people on QRZ hang out around here.

    In the past couple of weeks, I've heard a lot of QRM on 146.490 that goes down to about 146.470.

    These guys take up 20KHz of bandwidth, and it even sounds like it's a repeater system in the middle of the simplex raster.

    I've listened for callsigns, they're hard to decipher, a lot of static, but about 146.480 i heard what sounded like, and only sounded like, "wp2s repeater system"

    **I may have misheard that! If I have, my apologies to whomever WP2S really is**

    I looked up that call, and it didn't look right. I didn't think there was any real propogation on 2M besides ducting, and VI seems to far.

    Is there anyone in WA or nearby states that have heard this? It's really weird and 146.490 is the main emergency channel up here.

    Thanks for your help

    VA7KBH
     
  2. N7CPC

    N7CPC Ham Member QRZ Page

    I'm in the north Sound area and work southern BC quite often. Nothing on 146.49 at present. Any particular time of day?

    73 de Craig...........N7CPC
     
  3. VA7KBH

    VA7KBH Ham Member QRZ Page

    Mostly between 10[​IMG]0am and 2[​IMG]0pm -

    as I said, this freq is the Lower Mainland's inter-municipal emergency frequency, so hopefully it won't always happen.

    Thanks for the help.

    VA7KBH
     
  4. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Is it intermod or possibly a "spur" from some wireless intercom. Since it peaks between 10:00 AM and 2:00 PM, it sounds like it may be from some fast food restaurant since that is their peak time for drive-through.

    Glen, K9STH
     
  5. VA7KBH

    VA7KBH Ham Member QRZ Page

    It's definetly not intermod or anything because I can hear call signs - I am fairly certain I heard "WP2S Repeater System Link ON" and "KC9" something. It's kinda weird, and I'd be interested in finding out what's going on - might be nice to have a QSO

    VA7KBH
     
  6. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    It still can be intermod. Quite often, especially when only one of the mixing signals has voice modulation (the other signals being digital), you can copy the modulation without any problems at all. Do you hear it on more than one rig? Do you hear it only at your fixed location or can you hear it while mobile? It is quite possible that the amateur repeater is in the 440 MHz range and the mixing signal(s) are on the commercial "high band" (150.8 - 174 MHz). Possibly the amateur repeater is in the 222 MHz range. They all can produce intermod on 2 meters with the "right" mixing signals.

    The fact that it is relatively unstable points very much towards intermod. Quite often, the source is the final amplifier of a transmitter, usually solid-state. Of course, virtually all of the commercial and amateur transmitters on VHF and UHF are now solid-state. There are other sources including your own receiver "front end" of the mixing that produces the interferring signal.

    Do you happen to have a scanner that is in use at the time that you are hearing this? Scanners are often a source of intermod. Does a neighbor just happen to have a new scanner? Of course, virtually any corrosion can cause intermod, especially that in an antenna system, down spout, etc.

    If you are hearing the signal on your mobile, I would try driving around and seeing if it gets stronger or weaker in any particular direction. By using a 3 or 4 element hand-held yagi you might "zero in" on the offending signal. If you can get two, or three, "bearings" from locations a fair distance apart, you can "triangulate" and find the site of the radiation.

    Do any other amateurs in your area hear this? If so, then they can take a bearing and you can take a bearing and triangulate the source. If no one else seems to hear the interference, then you need to look close to home for the source. Finding the source of intermod can be "fun" (and "fun" is not meant to be a pleasurable experience).

    Glen, K9STH
     
  7. VA7KBH

    VA7KBH Ham Member QRZ Page

    Thanks for the suggestions:

    In response to your questions, I have heard the QRM from many local points in my city. I use a Yaesu VX7 but I have friends who use a ICOM W32A and IC-H16 and they have heard it as well...

    Triangulation could be fun!! (Still think it's an amateur radio system though cause I heard callsigns)

    73
    VA7KBH
     
  8. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    If it is intermod, one, or more, of the signals could most definitely be amateur. It is possible that a spur is coming out of an amateur transmitter. Is there a 440 MHz repeater that comes out around 439.750 MHz that could be putting out at 1/3 of the desired carrier frequency?

    There are definitely other possibilities, but intermod should be near the top of the list.

    Glen, K9STH
     
  9. VA7KBH

    VA7KBH Ham Member QRZ Page

    I'm not sure if there is a repeater system nearby like that.... They are american call signs, because I've heard prefixes of WP2 and KC9... those don't seem like callsigns that should be in range..... however the QRM didn't come back today so I'm happy for a while.

    Thanks for all your suggestions - as a basic licensee I don't know all of these things.... but I did get a 92% on the written!

    VA7KBH
     
  10. VA7KBH

    VA7KBH Ham Member QRZ Page

    Hey all!

    I finally deciphered a callsign! Turns out to be some EchoLink node that is SUPPOSED to be at 443.550 but is not there when I listen to my dual VFO!!

    Interesting eh?

    Thanks for all the help

    VA7KBH
     
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