Heil Parametric Receive Audio System (PRAS)

Discussion in 'Microphones, Speakers & Audio Processing' started by KC8VWM, Aug 8, 2018.

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  1. KC8VWM

    KC8VWM Ham Member QRZ Page

    Radio manufacturers have not really put much effort or attention to the audio output section of most amateur radio transceivers. They often stuff cheap speakers inside them and there's really no options to tailor the audio output to our liking from any of the transceiver menus.

    We are often left to come up with our own ways to cobble together aftermarket products, construct our own external speakers and find other ways in an effort to do something that hopefully sounds better. Most outboard audio equipment we might try to adapt is often intended to be used for music reproduction and really doesn't work all that great for radio communication.

    I think we have needed a product specifically engineered for use with our amateur radio equipment like this for a long time.

    Game changer?


    Last edited: Aug 8, 2018
    YF8RQN, K0UO and PD0JBV like this.
  2. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    I got to see Bob Heil demonstrate his magic box at Dayton this year. Very cool....and long overdue.
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    I watched Bob's video clip. Selectivity is bestest applied BEFORE the receiver AGC detector. OTOH, the box is purty with a meter, and has various patch jacks. :)
    AF7XT and K0OKS like this.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'm sure it works fine, but just using good headphones (I never use a speaker or speakers for ham stuff, except mobile or whatever's in a hand-held for VHF) I've never found a super weak CW/SSB/AM signal I can't copy.

    I can't copy digital mode signals with them, though. They all sound like a warbly tone, and some are so weak you don't hear anything at all.:p
    WA7PRC likes this.
  5. WA7PRC

    WA7PRC Ham Member QRZ Page

    ^ ^ ^ THIS ^ ^ ^
    As a Novice, I developed the 'filter between my ears', and found headphones (Trimm cans, actually) helped. They had a nice SHARP resonance.

    I really like my SS rigs' IF filters. Even my olde Kenwood TS-120S had IF Shift that could remove QRM. My not as olde Kenwood TS-850S has Slope Tuning that allows me to move the upper and/or lower slopes to remove trash. All this happens BEFORE interference can cause AGC action. :)
  6. N1FMV

    N1FMV Ham Member QRZ Page

    I assume this is mono only (not stereo) so it wouldn't work with the stereo audio output of my Flex 6k series?
  7. KE0ZU

    KE0ZU Ham Member QRZ Page

    Bob showed it to me at Joplin, and it works as advertised. It can make many virtually unreadable signals, pretty easy copy, I was impressed. The concept is pretty simple, but it works very well.
  8. KE0ZU

    KE0ZU Ham Member QRZ Page

    Sure it would, buy two of em.
    K0SDG and N1FMV like this.
  9. WA7PRC

    WA7PRC Ham Member QRZ Page

    Active AF filters aren't new. They allow ALL signals inside the IF passband to act on the AGC detector to reduce gain. Best is to have selectivity BEFORE the AGC loop or, disable AGC and manually "ride" the gain.
    YF8RQN and K0OKS like this.
  10. KE0ZU

    KE0ZU Ham Member QRZ Page

    Of course they're not, however, this device has a tunable and level adjustable filter whose output is then added back into the base band, to provide a more balanced/complete/intelligible audio spectrum at the speaker or phones. It works well.

    We're not talking about AGC, or RF selectivity. What you've got going to the speaker, is all there is, readable or not. We're talking about the available audio spectrum coming out the back end of the radio, nothing more.

    If you're a NON-TECH guy, or not wanting to dig into your latest whiz-bang-do-all multi-Kilo buck radio, this device can go a long way toward making those virtually UN-readable received signals, readable.

    Again this has nothing to do with selectivity per se, but rather the content of the filtered spectrum, and its balance.

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