Let's rethink 3880

Discussion in 'Amplitude Modulation - AM Fans' started by K4KYV, Dec 7, 2017 at 6:28 PM.

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  1. K4KYV

    K4KYV Subscriber QRZ Page

    Typically, in early evening, we have three simultaneous AM QSOs on 3885, 3880 and 3873; sometimes with one or more of these QSOs operating as a "net".

    Five kc/s is too close for two adjacent AM signals.


    There is nothing sacred about those frequencies, and few of the stations crystal controlled. Wouldn't it make more sense to transmit on 3879, rather than insisting on 3880? 3879 falls precisely at the midpoint between the other two AM QSOs, leaving 6 kc/s separation between each signal, and less mutual QRM.
     
  2. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Doesn't much matter when the folks on 3873 are transmitting with 10kc or 20kc wide signals and interfering with both 3880 and 3885kc.

    Wouldn't it make more sense for the few on 3873 to move down to 3869 or 3859kc??? Huh? Eh? Nudge, nudge; wink, wink?
     
    AC0OB likes this.
  3. N2DTS

    N2DTS Ham Member QRZ Page

    An sdr really helps see just how much room and where it is to plunk your signal.
    No reason to use 3885, I was on 3886 last night and could have moved to 3887 without issue as the next signal up was above 3890.
    The guy I was working did not pick up that I was on 3886 even though I told him twice, he was thinking about other things I suppose.
    While everyone was nicely contained within a reasonable bandwidth, one person on 3880 was quite strong and caused a bit of noise on the weak signal I was working on 3885.

    But I see people drift down twards another qso when the band is empty in the other direction.
    I see that happen all the time, people have vfo's that drift, they do not re zero beat, and they have no idea what is around or where they are.

    Over the last few nights I have been on 3873, 3880, 3885, 3886 and 7, and 3890.
    I know many do not want a computer in the shack, but a cheap sdr shows a LOT of useful information.
    Its a good frequency counter(indicator), lets you see what signal is where, lets you see your and others width, and also makes a very good receiver.

    If you are just going to run a valiant and an nc300, pick up a cheap freq counter, you can get one on ebay for under $20.00 I think....
    Here is one for $15.00....

    https://www.ebay.com/itm/Digital-LE...252262&hash=item1ed3c9ec74:g:rUMAAOSwstJZP7jS
     
  4. K4KYV

    K4KYV Subscriber QRZ Page

    But it would at least help to add a little more distance from the QSO on 3885.

    When the band is moderately to heavily congested, I tune the receiver for minimum monkey-chatter from adjacent signals on both sides, and often find the sweet spot to be a kc/s or two away from the usual frequencies. When I call CQ on that frequency, apt as not, someone comes back dead on 3885 or 3880, whichever is closer. I usually remind them that I'm not precisely on one of those frequencies, and ask them to zero-beat my signal where they will be more in the clear. Occasionally, the other operator replies that he doesn't know what I mean by "zero-beating" or else asks how it is done.
     
  5. WA3VJB

    WA3VJB Ham Member QRZ Page

    Don, a couple years ago I tried to win support for a new AM "net" frequency that could have taken some of the load off the corridor where unscheduled AM QSOs and AM roundtables take place. I didn't get anywhere ! To recapitulate:

    The Sunday PM gathering of the Antique Wireless Association has been running close to two hours with dozens of AM stations. It has been my experience that the "show" suffers very little interference, there are never any catcalls from people on incompatible modes, and that the group seems to enjoy a spot on the dial that is not in dispute from twilight well into the evening.

    My idea was to utilize that frequency for evening schedules involving as many of today's AM "nets" as are willing to shift there. I proposed a calendar among these groups, where let's say on a given weeknight, the Gulf Coast Mullet Society might fill in a block of time, 7:30-9pm or whatever, then at some other time or some other night, the Collins Collectors Association might take an hour or two, and then on a vacant slot or block, let's have the Southeastern AM Radio Club's on-the-air meeting, and okay, here's the DX60 Net, the Multi-Elmac Net, the Old Military Radio Collectors Net, the Florida AM Net, and so on.

    I asked those groups and others regularly heard on 3880-3885 for their thoughts, and not a single one embraced the idea or was even willing to to try. One net control in particular seemed to take offense that I had even suggested the idea, since "why should we have to move our operators looking forward to fellowship" to some other frequency?

    Okay.....
     
    AC0OB likes this.
  6. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Ah, I have found the same thing. Good to have your observation confirming.

    I do agree that it would be best to have wider spacing. Unfortunately we are hemmed in on the upper side with SSB on 3890. Your post last week about using the typically sparse freqs around 3670 is worth encouraging. cheers, bill.
     
  7. KB3OUK

    KB3OUK Ham Member QRZ Page

    What about moving way up above all the sideband chatter to the top end of the band? Right now there's no ssb past 3983 in the northeast, at least what i can see on the k3fef websdr. Not sure what it looks like after dark up there though.
     
  8. K9STH

    K9STH Ham Member Staff Member QRZ Page

    I do have one of the relatively inexpensive SDR receivers but do not really use it for operating. Since they are "solid-state", those receivers should be pretty likely to be overloaded by strong signals and produce problems that are generated internally to the receiver and not by the "offending" station. As such, I would be hesitant to say that there are problems with the "other" station's transmissions when those "problems" may be generated within the receiver.

    Glen, K9STH
     
  9. N1BCG

    N1BCG Ham Member QRZ Page

    An easy fix for separate receivers is to add a "T" connector to the antenna connection and put a potentiometer across the open terminals. A 1K value would give sufficient attenuation range to prevent overloading. Use max resistance for normal operating and dial in a lower resistance (shunt) for 40 over signals. Now you can enjoy the benefits of an SDR without the overload.
     
    WB2GCR and (deleted member) like this.
  10. W2VW

    W2VW Ham Member QRZ Page

    Most active AMers know the limitations mentioned. They also know to attenuate in front of the receiving device to see if the displayed signal defect/signal level changes.
     

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