[TenTec] what is "quiet"?

[n4lq@iglou.com]

In my unprofessional opinion.....Every time we run that little signal 
through a non-active component such as a transformer, diode, coil, 
capacitor or filter of any type, we loose some of it. Then we must boost 
if back up with amplifiers. We worry about images so we use a high 
frequency IF. Doing this adds more noise. To get the 14mhz signal to the 
IF frequency we must add a mixer/oscillator....more noise. 
Then we say...whoops..The IF frequency is too high for good selectivity! 
So we must reduce it and install a filter. Slap another few mosey, 
unproductive stages in there...another mixer, another few transformers 
and some crystal filters....Oh..Crank up the gain boys, we're starting to 
loose our patient! But wait...We need passband tuning..Slap in another 
pair of mixers and oscillator and more transformers and BOOST HER UP 
AGAIN! By the time we're done, our poor, wimpy little signal is almost 
buried in all that racket. 

So why do we have all this extra baggage? 

A lot of it started when AGC became a standard fixture in our cw 
receivers. With it, we need enough gain to produce a bias voltage and 
make our S-meters flop around.

Then came the general coverage receiver craze. Suddenly, the receiver 
must cover 100khz to 30mhz....Not a bad feature in itself but various 
compromises are needed now.

Finally, along came the quest for super selectivity and passband tuning 
the results of which we are all familiar.

The QRP boys believe that most of the gain and selectivity should be done 
at the audio level. Hum and microphonics are design problems that have 
been overcome in recent years. A tight front end, one conversion stage, a 
moderate gain IF with a few crystals in "ladder" arrangement, BFO/Mixer 
and high gain audio amp blended with DSP would sure make a wonderful 
sounding cw radio wouldn't it? :*)
LQ
-----Original Message-----
From: "George, W5YR" <w5yr@att.net>
To: n4lq@iglou.com
Date: Tue, 02 Apr 2002 11:35:03 -0600
Subject: Re: [TenTec] what is "quiet"?

> But, an isotropic antenna picks up all signals from all directions . .
> .  
> <:}
> 
> Do these comparisons account for the differences in overall gain -
> antenna
> terminals to speaker output - among the different types? I suppose so
> if
> the d-c receivers can achieve a 10 dB S+N/N ratio with a 0.1 uvolt
> signal
> at the antenna terminals and 2 watts of well-distorted (!) audio at the
> speaker . . .
> 
> Curious . . .
> 
> What I have read so far accounts for the output noise level in the
> absence
> of an antenna connection only in terms of faults or deficiencies in the
> multi-conversion receivers. Is this true? 
> 
> What *advantages* does multi-conversion architecture convey that are
> missing in the simpler radios? Like all engineering, receiver design is
> a
> trade-off. So, I think that we have to balance the gains in performance
> with the potential losses - more noise? - when we compare.
> 
> 73/72/oo, George W5YR - the Yellow Rose of Texas         
> Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
> Amateur Radio W5YR, in the 56th year and it just keeps getting better!
> QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
> Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437
> 
> All outgoing email virus-checked by Norton Anti-Virus 2002
> 
> 
> n4lq@iglou.com wrote:
> 
> > Listening to a direct conversion receiver is like having your brain
> > directly connected to an isotropic antenna.
> 
>