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. W2VW

    W2VW Ham Member QRZ Page

    The best place to move IMO would be 3680 area.
     
    AG5CK and KB4QAA like this.
  2. WZ5Q

    WZ5Q Ham Member QRZ Page

    Shhhhhhhhh..... That's a secret!
     
  3. K4KYV

    K4KYV Subscriber QRZ Page

    Another problem is the lack of front-end selectivity. A couple of winters ago I used my Kenwood R-1000 with my 160m Beverage to monitor European longwave BC stations in the 150-200 kc/s range. The nominal frequency range of the R-1000 goes down only to 200 kc/s, but it will receive, with reduced sensitivity, all the way to 150. However, the images and spurious signals come in as strong as or stronger than the desired signal so that all I hear is a jumbled up mess. I threw together a tuned coupler which I inserted between the antenna and receiver. That cleared up reception. Nearly all the spurious rubbish went away. I was able to pick up a German station circa 160 kc/s, the BBC circa 200 kc/s, and several other stations, entertainment quality at times. Previously, I had never been able to even hear any trace of a carrier from the European LW stations. The R-1000 has no front-end selectivity, except for a series of broad bandpass filters, each covering about an octave in frequency range. I suspect the drop-off in sensitivity is due to operating below the edge of the lowest frequency filter. Few of to-day's receivers and transceivers have a real pre-selector at the front end and depend on solid state electronic gimmickry to reject unwanted signals. That may work OK within the signal-handling capability of the front end, but anything stronger than that causes the "virtual selectivity" of the receiver to go belly-up. On any frequency, with anything less than a nearly ideal receiver, a passive pre-selector can work wonders.
     
    N5DMC and KB4QAA like this.
  4. N2DTS

    N2DTS Ham Member QRZ Page

    Well, I have an sdrplay rsp2 which is about $160.00 and on full size anrenna's it has no problems.
    You have to turn the rf amp off, its got a gain adjustment as well as band pass filters and broadcast (am and fm) filters built in.
    It works just fine to see where you are, where the holes are, how wide signals are, and its got a .5 ppm clock chip in it.
    I have compared it to the Anan 100b and if you keep the gain down on HF, there seems to be no difference.

    Here it is running SDRuno:
    [​IMG]

    SDR radios do not distort or do anything odd below A/D overload, and even when you overdrive the A/D converter they don't do odd stuff.
    You CAN get broadcast birdies on 160 but I see that on the Anan and the icom 7300.

    Here is another program and you can see the holes to fit into:
    [​IMG]
     
  5. AG5CK

    AG5CK Ham Member QRZ Page

    That seems too easy.
     
  6. K9STH

    K9STH Ham Member Staff Member QRZ Page

    VW:

    I do realize that most AM operators do know the limitations of solid-state receivers and how to tell if the apparent problems are being generated in the receiver or by the transmitter. However, I also think that the majority of AM operators are also using tube-type receivers and those receivers are definitely much less likely to have problems with overload.

    The overload problem is why I question those who show SDR displays that display problems with others' transmitters. It has been my experience that when there are "problems", in solid-state receivers, with signals that for 1 problem that is actually traceable to the transmitter over 99 are actually generated in the receiver. If the operator knows the "tricks" to tell if the problem is caused by the receiver or is caused by the transmitter, and employs them when making the observations, then I have considerably more faith in the report(s).

    Of course, there are individual operators who don't care about having a "clean" signal and there are those who just do not realize that their transmitter is causing any problem. But, the vast majority of AM operators are not the "controls fully clockwise" type of operator and do try to keep their transmissions "clean".

    I do not operate using AM all that much. However, when I do operate I have found that the vast majority of signals are "clean" and meet "standards".

    Glen, K9STH
     
  7. W2VW

    W2VW Ham Member QRZ Page

    STH,

    That's all fine.

    The original really poorly designed solid state hamateur gear is now antique.

    Things change very quickly. Hardware varies by area also.

    In 2 land the majority of active low band AM operators use newer gear for receivers. Newer means they do not glow in the dark. I'd have to check my logs but it is over half.

    Last 10 meter season was a real eye opener. Most of the international 10 meter AM people used newer gear.

    The utility of continuously variable bandwidth with limited artifacts, multiple notch filters, selectable sideband AM detection along with whatever they call exalted carrier detection in SDR is very hard to pass up for the active low band operator. People who collect stuff, are casual operators or only SWL may be better off with chrome or Art Deco.

    I'm happy to know you do not hear the all knobs to the right AM guys in 5 land.

    2VW


     
  8. K5UJ

    K5UJ Ham Member QRZ Page

    Trying 3879 is good idea. I worked Don there around a week ago and QRM was minimal as I recall. But ideally, spacing should be 10 kc. But net operators will view an attempt at relocation as an attack on their liberty. There are some ops who never transmit except in a net. It's all mental. Old Farts who get set in their ways. tune up down the band? too much trouble. I bet if a net on 3885 moved to 3680, more than half of check ins would vanish. Like moving hamfest from Hara Arena to Xenia.
     
  9. N2DTS

    N2DTS Ham Member QRZ Page

    Most sdr's can be rated as lab equipment, they are that good, and show what is there, and what is not.
    Most allow attenuation to check that things track.
    The strongest signal I ever pick up is K1KBW who I can hear and see with the antenna disconnected. 60 or 70 over S 9 at times.
    He used to overload the homebrew tube RX till I changed the detector design, he does not overload the sdr's.

    I have three sdr's at the moment, the Anan 200b (quite good), the icom 7300 (no low end audio but good otherwise) and the $160.00 RSP2 which works great if you keep the gain low.
    Turn the gain up and things look the same but the audio chops up.

    Anyway, I cut my antenna's to have a low swr where the AM is, which is 7290, 3880 and 1880.
    Its like 1.2 to 1 and I use no tuna.
    I can move some without issue, depends on the band, but moving all over the band is likely a pain for anyone not using modern auto tune gear.
    I can picture guys moving clips on big balanced tunas, retune the driver stage, the final, the tuna, then back again when the net is over...

    Even though I have various receivers and receiver types, I tend to not scan the band, just jump from the AM windows on each band.
    Maybe, over time, we will be able to spread the window out?
     
  10. WB2GCR

    WB2GCR Ham Member QRZ Page

    The key to the idea Don put forth is simple enough in my opinion...
    ...to establish a "new beach head" one or more stations with "strong signals" would need
    to meet on a predictable basis on some other frequency.

    For example there is/was the "What's For Dinner Net" on 3835.
    Featured "Slab Bacon" originally.

    When the bands first expanded, I suggested pretty much this idea.
    Few were "enthusiastic" at that time, and I did not think I had enough fire in the wire to
    go it alone...
     

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