> the short answer is that usually a receiver described anecdotally as
> "quiet" is a receiver that has inadequate gain.
While the above is technically correct, there is still something
mysteriously quiet about simple receivers that make them more pleasant to
monitor. Take for instance the TenTec T-kit series which is a single
conversion superhet and my Conar 4 tube receiver. I can crank up the volume
on these things during a noisy night on 80m and it seems like I hear nothing
but signals and sounds that are ACTUALLY there. Static sounds like a gentle
crackle wafting through the room and weak cw signals sound clear, clean and
pure. The ears don't strain trying to separate the noise from the signal.
Then I turn on the fancy quad conversion rigs (TenTec or whatever) and 80m
sounds like the roar of a jet plane. The S meter hovers at 20db over 9 and
within minutes I'm ready to give my ears a rest. Sure, I can kick in the
filters, crank in some attenuation, carefully reduce the RF gain and manage
to copy the signal but even then it's a strain.
Now we all know the simple receivers don't have as much gain but then again,
maybe they don't need as much. Maybe they don't have to force those little
signals through several mixers, crystal filters and dsp circuits. Maybe
having no RF amplifier, an IF with moderate gain and getting the big boost
in a high gain audio amplifier is the way to go. Sure, the weak signals are
indeed weak in my speaker but I can still hear them and there's no roar
in-between the dits and dahs. Yes, the same weak signal on my big radio may
read S5 along with the roaring but now I must twiddle, fiddle and strain to
copy the thing. Why just yesterday, I used the QRP rig to call cq on 40cw
and heard a weak signal calling me. He wasn't very loud so I put on my
headphones. The guy was running 250 milliwatts with his Corsair II. I had no
problem hearing him because HE was the only sound in my phones. Switching to
the big rig, he was S5-S6 and the noise was S5. I kicked in the filters,
turned on the NR and fiddled with the RF gain. After one round of that, I
went back to the little rig and gave my ears a rest.
So I guess I'm still a bit mystified by all of this. It seems like modern
radios consist of 2 parts...One part to receive and amplify the signals and
the other part to reduce all the racket it produces in the process.
"And the vision that was planted in my brain
Still remains
Within the sound of silence."
Simon and Garfunkel
|