[ARC5] Way OT -- SX-28

[Richard Knoppow]

    See my previous post. One important reason is that the 
"communications" receivers were also sold as general purpose 
broadcast receivers. Some, like the SX-28 and Super Pro had IF 
that could be set at a wide band and deliver fairly high fidelity 
sound from both MF and short wave broadcast stations. The better 
quality amplifier also allowed the receiver to be used with a 
phonograph attachment so it would serve as a family entertainment 
center. Remember, these receivers were VERY expensive so any 
feature that could help justify the cost was important.
    I will also repeat the point that eliminating distortion in 
the audio amp makes a noticable difference in the effect of noise 
and QRM.
     The idea of an external amp of course is a good one. If the 
receiver has a connection for the diode load picking the audio 
off of it will make a surprising difference in most receivers. 
But: also turn off the AVC since it tends to feed back the low 
frequency modulation causing serious IM.

On 8/6/2021 1:22 PM, Hubert Miller wrote:
>> I have never understood the need for "big audio" in a communications receiver.  Who needs it unless for distribution to remote speakers.  A Zenith Transoceanic portable will fill the shack with more volume than you can use with only 730 mW output from its 3V4 audio amp.  Mike, W6MAB
> Ditto that. I have a National NBS-1 ( NC-183+ ) and I don't see the need for powerful PP output on a communications type receiver.
> I notice the two Eddystone recs I have use single ended. I think a 'line out' connection would suffice if one wants better audio.
> I would rather see a smaller single output tube with lower heat radiated inside the radio, or maybe smaller tubes, like some dual triode, for the
> audio output if one is concerned about tone.  As for CW, what comes to mind is noise and fading on the signal anyway, so I myself would not
> appreciate higher quality reproduction for this mode.
>
> The previous post with comments about features of PP audio is entirely valid. I just don't see the need. On the other hand, maybe the tube
> Transoceanics could have used a smaller PP audio output, but maybe in this case, the size and quality of the speaker would make that a not
> worthwhile step up? A German WWII troop morale receiver just came to mind, the WR-1, a battery set with a PP audio output. However the
> audio power is a whole lot less than 2 6V6. Their output tube is some kind of, if I recall, 1.5 volt dualtriode loktal.
> -Hue Miller
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL