class e rigs

Discussion in 'Amplitude Modulation - AM Fans' started by N2DTS, Oct 23, 2017.

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  1. AC0OB

    AC0OB Subscriber QRZ Page

    What? You need to be wide to exact revenge from BillyBob's asian transceiver wiv 4-1000 Linyear feeding into the wife's clothesline?

    I thought you simply needed to be an AMer.

    Phil
     
  2. N2DTS

    N2DTS Ham Member QRZ Page

    I tend to think, on a crowded band, no one is going to be listening in the 16 Kc position on their receiver, all you are going to hear is other AM and ssb qso's.
    So you are on 3873 and 20 Kc wide with lots of audio, to 'keep the ssb away'.
    Anyone listening in the 10 Kc bandwidth will hear the qso on 3880 and some of the qso on 3885, plus the ssb people on 3865 or whatever.
    And the people within the 20 Kc bandwidth of the signal will hear a lot of the 20Kc wide signal and be annoyed.

    Ever see how close you can get to an AM signal on ssb without it bothering the ssb signal?
    I sometimes hear ssb close to an AM signal I am listening to and wonder what the ssb guys are thinking.
    I switch to ssb to see if its jamming and I notice the AM signal does not really bother the ssb signal at all, but when I listen to the AM signal the ssb is bad.
    Even with narrow filters (sdr).
    Going wide is not going to 'keep them away'.

    On the other hand, limiting the bandwidth is not easy, it is on SDR radio's, but not so easy on anything else.
    What can someone do to limit the bandwidth?
    I have been running a D104 which seems to do a nice job of that, but if I run a good microphone, I can pass very wide bandwidths.
    How do I chop it off at 4000 or 5000 Hz?
     
    WB2CAU likes this.
  3. K4KYV

    K4KYV Subscriber QRZ Page

    The reason for that is that the SSB guys are receiving with a product detector. You can do the same thing on AM with a synchronous detector. That makes a lot of the SSB monkey chatter and other interference not actually go away, but it becomes more transparent and you can understand the desired signal right through it and ignore the crud, like engaging someone in a conversation in a crowded room at a noisy party. You mentally focus on the person you are talking to or the desired signal, and disregard the noise.
     
  4. KD2ACO

    KD2ACO Platinum Subscriber Life Member Platinum Subscriber QRZ Page

    I built a 5 pole Chebyshev low pass filter into my mic pre at about 4kHz. I can put a nice upper mid boost in there and the extra filter is nice and steep. It adds to the 3 pole Butterworth LPF in the EQ that's modded to live at about 4kHz. Between the two of those, the top end on my system is nice and crisp and rolls off in a hurry above where I want to have energy.
     
  5. N2DTS

    N2DTS Ham Member QRZ Page

    Got a design for this?
    Any way to build a nice simple (passive?)circuit that would chop stuff above 4500 Hz?

    I have been having fun running the commercial audio stuff with a good microphone and on all rigs it can go out 15 KHz.



     
    KD2ACO likes this.
  6. KD2ACO

    KD2ACO Platinum Subscriber Life Member Platinum Subscriber QRZ Page

    Hi Brett,
    I've got the McGraw-Hill Electronic Filter Design Handbook from decades ago (school) and looked around their selection chart to pick what I wanted and put it down on some perf board.

    Eliptic filter.jpg

    Stole power off the main board... not too original but easier to build in op-amp land than to try and find it made already.

    I imagine that there are Elliptical Filter component calculators online that would help with value selection too.
     
    Last edited: Nov 15, 2017
  7. WA1QIX

    WA1QIX Ham Member QRZ Page

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  8. AC0OB

    AC0OB Subscriber QRZ Page

    All good info.

    Here is a 5kHz Third Order Low Pass Filter schematic below. i included a mic amp just in case.


    Phil
     

    Attached Files:

    KD2ACO likes this.
  9. W2JBL

    W2JBL Ham Member QRZ Page

    Here's the truth and it's gonna hurt some people. Class E is not inherently wide. It's the operators who are at fault. One station in Southern New England is intentionally setting his EQ to maximum bosst of everything above 5000 HZ. He's also running 2500 watts carrier (10KW PEP) He taught a station down in Nascar country to do the same. That station is running 1000 (or more) watts carrier. The reason given is "It's to keep the sidebanders away". Another station near Boston is capable of 7500W carrier at 20 KC bandwidth and is doing so at times but has multiple rigs of different power levels which are all way above the legal limit of 375 watts carrier. They all say they are running "legal limit". This is of course BS. The problem is really only from these three. I know many others running Class E rigs who are less than 10 KC wide and cause no trouble on the bands. There are a lot of folks in the AM community who are upset at having the entire AM window trashed by a few, and unfortunatlely some are threateninng to invite the FCC into the argument. If this happens AM as we know it may be compromised.
     
    AC0OB likes this.
  10. N2DTS

    N2DTS Ham Member QRZ Page

    I did not know you could get that kind of power out of a class E rig.
     
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