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What's the minimum distance from the simplex calling frequencies do I need to be?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KC0BUS, Sep 10, 2018.

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  1. W6KCS

    W6KCS Ham Member QRZ Page

    OP: As said earlier, 20 KHz is the minimum to prevent interference in all but strong-signal cases. The bandwidth of your signal is about 16 KHz wide, so that's 8 KHz above and below.

    But pick 30 KHz on 2m because that will put you on 146.55 or 146.49, which are agreed-on channels, at least in Northern CA and I assume most of the rest of the country. Maybe not L.A.
    On 440, check with your local repeater frequency coordinator, because different areas do "funny" things on different channels and you wouldn't want to end up on a repeater or link channel. The typical 440 channel spacing is 25 KHz.
     
    Last edited: Sep 11, 2018
  2. WA4ILH

    WA4ILH Subscriber QRZ Page

    I'm curious why you are asking this question in the first place. If you are interfering with another station which is very close to your QTH, why not just operate more than one "channel" above or below 146.52? The problem could be the receiver which is receiving interference. There are 2 meter simplex channels in the 147 MHz range. 147.420 MHz is a simplex frequency and should be far enough away to not interfer with even a less than perfect receiver.
    Tom WA4ILH
     
  3. WA9SVD

    WA9SVD Ham Member QRZ Page


    Just don't operate 2M simplex outside of the "mandated" 15 kHz steps, or TASMA will be on you like a dog on a bone. THEY mandate the "channels" on 2 M simplex in Southern California.:mad:
     
  4. KM3F

    KM3F Ham Member QRZ Page

    To k7jem.
    If two repeaters are on the same pair with different PL tones and one is keyed up, the user of the other repeater could be heard accessing the second repeater providing the propagation it there to support the distances..
    Look these up.
    146.655 Waymart, Pa.
    146.655 Easton, Pa.
    If I am on the Easton machine, I can be heard on the Waymart machine 70 miles away.
    This is due to my elevation.
    Both these repeater locations are shielded by their locations but not from my location from my transmitted signal.
    The Pl tone does not make a difference to the other machine if both are keyed up at the same time.
    There is a solution to it by lowering power because the Easton machine is only 1/2 mile away.
    I access both machines for nets.
    If the local machine is keyed up by some one, others get confused pretty quick hearing me on the local repeater through it's input they keyed up while I am on the other distant repeater's input on a different PL.
    Under these conditions PL tones don't matter.
    Each could hear the other's Transmissions if propagation is good enough at the time.
    Happens often with other repeaters on same pairs during nets when propagation supports it.
     
  5. K7JEM

    K7JEM Ham Member QRZ Page

    The normal way a repeater is configured is so that the audio squelch will follow the PL tone. IOW, when the proper PL tone goes away, the audio goes away, after a few milliseconds. If it was configured this way, using an improper PL tone would not allow any audio to pass. It sounds as if this machine is running its audio under carrier squelch, but using the PL decode to key up the repeater, but not switch the audio. That could account for what is happening, but it is not a normal PL receiver condition.
     
    W6KCS likes this.
  6. W6KCS

    W6KCS Ham Member QRZ Page

    It almost sounds like they use their PL decoders like burst decoders, where PL is only needed at the beginning.
     
    K7JEM likes this.
  7. W2WDX

    W2WDX Ham Member QRZ Page

    You Cali guys and your obsession with repeater operation ... the OP @KC0BUS question was clearly about point-to-point simplex ... in Missouri no less.

    A 15kHz spacing should be acceptable for your region on 2m simplex, however 20kHz for 2m & 70cm should prevent any problems at all interfering with anybody. Of course, if they are nearby and you are very strong, and the receiver isn't good you could potentially cause overload or IM issues. However, with 20kHz spacing the receiver would really have to be very poor and very close for this to happen.

    Have you had a problem with someone recently that prompted this question?
     
    Last edited: Sep 13, 2018
  8. WA9SVD

    WA9SVD Ham Member QRZ Page


    Tell that to TASMA. who have commandeered 2M simplex and channelized it, and have commandeered the 70 cm segment as well. Going against THEIR dictates can gwt you an FCC violation notice, whether the actual interference occurs or not. THEY make the "pre-emptive" strikes.
     
  9. K8JD

    K8JD Ham Member QRZ Page

    How Much Separation ?
    Adjacent channel may be too close,
    I had a neighbor a half mile away who liked to chat on 146.500 , for some reason, so he wiped me out on 146.520 . I tried to filter him out with some Huge VHF tuned cavities (looked like ten gallon jugs) but they were close but slightly too broad to help.
    I think 15 kHz is too close 30 kHz maybe OK.
     

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