[Premium-Rx] The "Sound" Of Receiver IF Amplifiers

[Carcia, Frank A. HS]

hi All,
The sound of a receiver in my view is effected by filter skirts and IF
amplifier gain.
I like nothing coming out of the speaker when there is no signal. This is
impossible so 
I find the best thing to do is have 2 receiver configurations. 1 for good
conditions and the
other for bad. 1 for comfort and 1 for speed. Maybe some of the DSP machines
will give both
but I don't own one yet.  Vertical skirts ring when it comes to filters but
are great for
battle mode. A receiver with good gain distribution needs IF post filtering
to reduce noise
in the audio. I found the RA6830 has enough extra gain in the 455 KHz. IF
that I was able to install another filter module ahead of the demodulator. I
only had to increase the audio gain
in the demodulator a bit to pass bite. The ambient noise dropped 8 dB with
the 6 KHz filter
selected. 3 filters cascaded in the 455 IF limits audio response so pick
your poison.  fc

-----Original Message-----
From: Llgpt at aol.com [mailto:Llgpt at aol.com]
Sent: Tuesday, October 07, 2003 8:24 AM
To: rmilne at cfl.rr.com; premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] The "Sound" Of Receiver IF Amplifiers


Bob and group,

I too, have used a Sherwood SE-3 for many years. I run the if output of a
SP-600 into a Kiwa Map Unit and feed the post filter if output of the Map
unit into the sherwood se-3. Superb audio and a product detector to boot.

Les Locklear
Gulfport, Ms.


In a message dated 10/7/2003 4:41:43 AM Eastern Daylight Time, Bob Milne
<rmilne at cfl.rr.com> writes:

>Hi All,
>
>For years I have been intrigued (and mystified) by the very noticeable
>differences in the "sound" of various receivers. Much of this I
>chalked up to differences in the audio sections and tube vs.
>solid-state amplifiers. But that ain't necessarily so.
>
>Having recently acquired a Sherwood SE-3 Synchronous Detector on eBay
>my eyes (and ears) have been opened. Besides performing superbly as a
>synchronous detector, the SE-3 is a marvelous tool for evaluating
>receiver IF sections (since it bypasses the on-board detector and
>amplifier circuits).
>
>Using an HP 8640B and a Mini-Circiuits ZAD-1H mixer to match the SE-3
>to IF's ranging from 5 MHz to 50 kHz, I started comparing various
>receivers. Here's a few quick observations:
>
>To my ears, the Mackay MSR 5050A definitely sounds smoother and less
>harsh than the Racal RA6790/GM. But the SE-3 revealed that the
>occasional bursts of high-frequency distortion the 5050A has on some
>signals (mostly AM) originates in the IF section--and not in the audio
>section as I had suspected.
>
>The Drake R7A sounds superb on the SE-3, as does the Collins 51S-1.
>And because the 51S-1 uses offset 2.75-kHz mechanical filters, you can
>switch from AM to USB to LSB without losing lock on the SE-3. This is
>the first time I've been able to take advantage of the 51S-1
>mechanical filters on AM signals since the non-synthesized VFO just
>isn't stable enough for normal ECSS tuning. And the SE-3 preserves at
>least 90% of the crystal-clear audio the 51S-1 is capable of.
>
>Another thing that surprised me is how well-matched the 51S-1's
>mechanical filters are. Using the SE-3 it's hard to detect any change
>in tonal quality switching between the USB and LSB filters. In
>contrast, the MSR5050A's USB filter definitely has more treble
>emphasis than the LSB filter.
>
>Anyway, what these few quick comparisons have proven to me is that
>many of our Premium Receivers have wonderful features which are hard
>to do without once you've used them; stable and precise VFOs, memory
>channels, keyboard frequency entry, etc. But as for producing the
>best, most-listenable audio, some non-premium receivers have them
>beat.
>
>Any comments or observations from the group?
>
>Regards....
>....Bob
>
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