AM notes from the field

Discussion in 'Amplitude Modulation' started by K5UJ, Jul 1, 2020.

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  1. K5UJ

    K5UJ Ham Member QRZ Page

  2. WA3VJB

    WA3VJB Ham Member QRZ Page

    Thanks for posting this, Rob.
    Mike Pappas is W9CN, and has quite an interest in our part of the hobby.

    As a ranking official with Daysequerra, the company that bought Orban a few years ago, he donated a brand-new Optimod 9300 to W1AW for the buildout of AM activities by the ARRL in Newington. The unit has been used for the weeknight, 7290Kc W1AW voice bulletin on AM , as well as with the Index Labs AM transmitter and the Sennheiser 421; and also on the W1AW Gates BC-1T that our TimTron, WA1HLR, modified up to 75 meters AM.

    At home, Mike has a broadcast transmitter configured for our HF bands, at least 160-75-40, and possibly beyond. I have yet to work him, but he was trying to find more time to get on the air with W9CN after the AM-related developments at W1AW.
     
  3. N1BCG

    N1BCG Ham Member QRZ Page

    With any luck the Optimod will be moved to the lab and used with the Gates BC1T. The iCom used for the 7290 bulletins has plenty of filtering and limiting built in.
     
  4. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    "...Take a critical listen to your station. Do the announcers sound “crunchy” with elongated, raspy sibilance? If so, it’s probably beating your Time Spent Listening (TSL) numbers to death. If you turn down the clipping, it will help considerably. Also, consider buying a newer processor. An early 1990s AM processor set to “Chernobyl” to try and get over today’s high noise floor environment isn’t going to cut it. And with all due respect, old analog processors just can’t be competitive any longer in most markets.

    And then there is the PPM enhancer which many have set way too high — I call that setting “max rock crusher.” At that level, those tend to sound like a steel bowl being scraped with a whisk. A bit of a deft touch is in order to not sound like a Mixmaster with a bad bearing..."

    I love his hilarious descriptions of what some stations sound like.

    However, with proper modifications applied to say an analog Inovonics 235 or even an Inovonics 222, one can improve the station's sound considerably.


    Pheel
     
  5. N2DTS

    N2DTS Ham Member QRZ Page

    My TSL numbers are way down but I don't think its my out of date processing....
     
  6. N1BCG

    N1BCG Ham Member QRZ Page

    It's likely your Bert Kaempfert & The 101 Strings based music format. Fire the Program Director and switch to all-talk. Cheap format, particularly when it's off the satellite.
     
  7. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    There you go again picking on my Bert Kaempfert and 101 Strings albums. :D


    Pheel
     
    N1BCG likes this.
  8. K5UJ

    K5UJ Ham Member QRZ Page

    In the article he said something to the effect that broadcast stations still using older analog processors (I take that to mean 9000s and 9100s and contemporary products) should just give up on them and move on. I consider that good news for us. I like my Tri-Maze and Orban compressor ahead of it, and my CRL stuff but I'm always open to trying other affordable boxes.
     
  9. K5UJ

    K5UJ Ham Member QRZ Page

  10. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    A good article as well.

    Having worked on many BC transmitters starting with a gates BC-500GY up to DX-50's, and most everything in between, there is a lot of similarities between the old and the new in terms of transmitter design.


    I think I like the more modern solid state transmitters simply because of their more modular design, and because if one module fails, it keeps on working (at reduced power) until another module replaces the failed module.

    However, I did have a failed 810 modulator stage in a BC-500GY (a couple of overheated passive components, not a tube) and the transmitter still performed albeit with lower modulation and some distortion.

    And speaking of modular design, look at the Ratheon R-1000:

    https://worldradiohistory.com/Archive-Catalogs/Raytheon/Raytheon-RA-1000-1kw-AM.pdf

    It has a walk-in cabinet, one side is the audio/modulator section, the other side is the RF system and each section has a series of pluggable modules.

    What killed the Class B tube modulation system with the vacuum tube RF section was an incremental increase in technology first to the discrete solid state transistor and then to the Integrated Circuit, with a reduction in the power required to obtain, say, the same 1kW of power. And then more efficient modulation systems appeared, such as Pulse Width modulation and Direct Digital Modulation.

    And while the newer solid state transmitters can offer low resultant distortion figures, can the average man of woman really detect that lower distortion on bandwidth limited receivers?

    Pheel



     

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