[Premium-Rx] Racal 17XX speaker

Tue Aug 10 15:36:14 EDT 2010

None of my receivers were offered with internal speakers. The 600 Ohm audio is line level and meant to be passed to other equipment. I tried two solutions. 

The WJ S-9903E has reasonable fidelity for communications work and it is an amplified speaker with a 5W final. Up to 7 receivers can be connected to the selectable inputs. 

The final solution was a combination of 15 band graphic EQ's and amplified speakers. I chose the Behringer Ultragraph Pro for the EQ. It has RF shielding on every port. The amplified speaker is a Fostex RM-1 with dual 15W finals. 

The advantage of having adjustable input levels and bandwidths is significant. The audio can be configured for many types of listening. This is especially useful when you have radios that cover a very wide range of frequencies and modulation types.

Another consideration might be to replace the EQ with an audio processor (DSP). High quality audio is worth the added expense especially if you spend a lot of time listening.

  ----- Original Message ----- 
  From: Thomas Adams 
  To: Steve Pappin ; Michael O'Beirne ; Enrique Fernandez García 
  Cc: PREMIUM-RX 
  Sent: Tuesday, August 10, 2010 10:28 AM
  Subject: Re: [Premium-Rx] Racal 17XX speaker

  Greetings!

  That front panel speaker is a bit of a paradox.

  When I got my first 1772, the speaker in it sounded quite GOOD... it still
  does.

  On the second and third radios, it sounds like somebody shoved the RCA
  pooch head first into the horn! 

  As has already been mentioned, that tiny speaker is meant as a means of
  checking receiver operation locally, not for extended operation... but I've
  been keeping an eye open for a very long time now for replacement speakers
  that will fit the space and mountings on the panel. So far, no success.

  I'm of the opinion that the two bad sounding speakers have warped cones,
  and the voice coils are dragging in the magnet gap.

  In any case, I'm sort of partial to rack mounted speakers over the operating
  position. For the 2 radios set up for diversity I therefore have a rack panel 
  made up that has two good quality 6" speakers mounted on it. That leaves
  nothing to be desired for audio quality.

  For the "solo" radio, another rack panel holds an 8" Radio Shack Hi Fi 
  driver. That's backed up by a plywood enclosure, forming an infinite baffle
  speaker. When I made it, I considered adding a reflex port and a tweeter, 
  but I decided against it; I was tired of sawing and fileing big rack panel 
  holes!

  Comparing it to the audio response of it to the legendary (and overpriced!) 
  Hallicrafters R-42 Reproducer (an 8" Jensen driver mounted in a steel bass 
  reflex enclosure) I can't hear much difference.

  The RA-1772 is capable of quite good audio reproduction on AM broadcast
  signals, especially if the IF filters include the 8 or 13 KHz. I personally find
  the 6 KHz to be a bit narrow.

  Distortion seems quite low, at least to my ears.

  The response is SO good in fact that it can be a hindrance in applications 
  that require less response, like SSB; with a good speaker, too much garbage
  comes through, even with the IF cranked narrow.

  On my fancy "solo" speaker, I found it helpful to add a trick from the Hallicrafters
  R-42 and R-44 speakers. 

  I stepped up the audio impedance to 500 ohms, and added the roll-off network
  they used; a couple of .5 MFD capacitors (one in series and one in parallel with the
  500 ohm audio line) , switched in and out of the circuit with a DPDT toggle switch 
  marked COMMUNICATIONS and HIGH FIDELITY. After all of this, another 500 / 8 ohm 
  transformer lowers the impedance again to match the speaker's voice coil.

  With this setup, or with any decent receiver top speaker, the RA-1772 is an excellent
  AM BCB DXing receiver.

  Mr. T., W9LBB

  At 16:31 09-08-10, Steve Pappin wrote:

    BTW, the manuals can be found here:
    http://www.radiopics.com/Racal/Racal_RA%201772.htm

    ----- Original Message ----- 
    From: "Michael O'Beirne" <michaelob666 at ntlworld.com>
    To: "Enrique Fernandez García" <enriqueeeeee2001 at yahoo.es>
    Cc: "PREMIUM-RX" <premium-rx at mailman.qth.net>
    Sent: Monday, August 09, 2010 1:04 PM
    Subject: Re: [Premium-Rx] Racal 17XX speaker

    Dear Enrique

    Forget the panel speaker.  The small 2 inch panel speaker is not designed
    for hifi!!!!  It's just there to tell you whether or not there is a signal.

    A professional would be listening via nice comfy headphones, and the output
    to his comms system would almost certainly be sourced from the excellent
    quality audio from the 600 ohm line output.

    What you need to do is to connect a QUALITY speaker to the 8 ohm output.  I
    use a nice British-made Linn hifi speaker that's physically a lot bigger
    then the panel of the 1772.

    A decent station such as BBC Radio 4 LW is not hifi because of the Optimod
    modulation system used ( a sort of compressed AM) but even so the bass
    response of the 1772 via the big speaker reminds me of the lovely old
    "steam" valve radio of my late dad.

    Some modern DSP receivers apply far too much bass cut to the audio, even on
    AM.  They are good for "communications" quality SSB and the like but sound
    pretty thin and miserable on a decent AM station.

    ----- Original Message ----- 
    From: "Enrique Fernandez García" <enriqueeeeee2001 at yahoo.es>
    To: <premium-rx at mailman.qth.net>
    Sent: Monday, August 09, 2010 5:31 PM
    Subject: [Premium-Rx] Racal 17XX speaker

    I forgot, concerning to the panel mounted speaker, it sounds terrible in my
    1772, I have tried different things such as put some ball papers between the
    cone and the metal with not good results.

    Anybody has the same problemm with the speaker? Any solution?

    I have already got a Minimus 7 external speaker connected but I do not why I
    like to listen the internal much better.

    Regards

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