[Premium-Rx] HF SQUELCH

[John USA]

Hi Guys,

Take a look at http://www.nhrc.net/nhrc-squelch/Squelch-Manual.pdf, which is the manual for a noise-riding-squelch circuit boards, intended for repeaters.  I tried the idea that was mentioned a few emails ago, wherein I applied this self-cintained squelch to my SSB/CW rx (at the time using WJ8940B and a trick with a HP 8568B spectrum analyzer (overall failure, but the squelch worked).

My results were fine in most cases, outstanding in other cases, and one or two isolated instances did no work at all.  This squelch system is sold ready to go, plug in your audio in & out and plug in your RF source.  This works based on noise level, not RF level...read up on it.  I expect my recollection here may be foggy on a few details, but it did work.  I think one issue is that an FM repeater has an expected level of empty channel noise...you need to get an SSB channel sample to this subsystem, that has approx the expected noise on an empty channel.

I no longer use this system...in fact, I may have a couple of boards available as-is...I know that's a dreaded ebay term, but I really don't have the facilities to test the boards at the moment...most everything is in deep storage.

regards

John Collins
_______________________________________
  ----- Original Message ----- 
  From: Larry Gadallah 
  To: premium-rx at ml.skirrow.org 
  Sent: Wednesday, March 29, 2006 1:56 PM
  Subject: [Premium-Rx] Re: HF SQUELCH





  On 3/29/06, premium-rx-request at ml.skirrow.org < premium-rx-request at ml.skirrow.org> wrote:

    ------------------------------

    Message: 5
    Date: Wed, 29 Mar 2006 09:55:19 -0600
    From: "k0dan" <k0dan at comcast.net>
    Subject: HF SQUELCH (WAS Re: [Premium-Rx] Simple clean audio amp)
    To: < premium-rx at ml.skirrow.org>, <Ka9p at aol.com>,        "Tim Shoppa"
            < shoppa at trailing-edge.com>
    Message-ID: <00b401c6534b$baef10c0$6601a8c0 at k0dan>
    Content-Type: text/plain;       charset="iso-8859-1"

    Hi Tim...

    Back in the early 80's the was a circuit (QST??? 73???) for a 2-channel SSB 
    "smart squelch". Sorry, I don't have the name/author/date anymore, but I did
    build one in those days which I used with some success with a Drake R7 and
    51S1, and it was sold when those radios were sold. Perhaps searching the 
    ARRL site might turn it up.

    The problem, however, with any squelch I've ever used on HF, is that they
    all get fooled by static crashes, heterodynes, splatter, etc. They DO work
    better than riding the RF and audio gain, but they do false, and if you're 
    listening to (or recording) a bunch of utility channels, it can get pretty
    annoying. This is especially so when a broadband lightning strike opens up
    ALL your receivers simultaneously, or when a "sweeper" signal sets them off 
    one by one!

    Good luck and 73

    Dan
    (K0DAN)


  I spent a fair bit of time looking for options for such a "smart" squelch or to be more accurate, a syllabic rate squelch.  The idea is that syllables in speech contain energy in certain ranges of the audio spectrum, and if you measure the energy in these ranges, there is a characteristic rate at which the energy appears and disappears, hence the name "syllabic rate". 

  There were indeed a couple of circuits published in 73 and QST in the 70's and 80's, as well as this one (http://www.ah6le.net/hf_squelch.html) from someone in the Echolink/IRLP domain, and they all probably work fine. If you search the patent databases, you will find literally dozens of patents related to this concept. What I found in the way of off-the-shelf solutions was limited to an expensive unit intended for marine use from an outfit called Naval ( http://www.naval.com/vos.htm), and the Ten-Tec kit mentioned earlier.

  What I really wanted to know was how to implement this in DSP, so that it could done using a PC and a soundcard. I found lots of theory, but not much practical. 

  Cheers,
  -- 
  Larry Gadallah, VE6VQ/W7
  lgadallah AT gmail DOT com 


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