Telamon wrote:
Very good Terry I don't see any reason for a flames. You post good
information and real world experiences. What you posted above is a good
example of what people reading the news group need to see in order to
make educated decisions about antenna systems.

I just add that the natural noise floor is not flat and Terry's examples
above are at some particular SW frequency. If I see a good natural noise
figure chart link on the web I'll post it here.

Well, I'll just add more comment. What the information above alludes too
and that is as you decrease the bandwidth of your receiver the noise
floor should go down. Narrowing the bandwidth decreases the amount of
spectrum that goes through the receiver and that lowers the total
background noise at the receiver output. You will notice that Terry
references the filter bandwidth in his examples.

--
Telamon
Ventura, California
---------------------------------
The last time I ventered an opinion on splitters dxAce and others took
exception
to my logic. So I decided to do some actual research. I expected
violent disagrement.

At first glance it does seem that adding 3.2dB of attidional
attenuation in the signal
path would have a clear negative effect on the reception of weak
signals. When I first
noticed this by direct experimentation, I was dubious. But after
several tests with
the weakest signal I could receive I decided it wasn't a fluke. After
getting flamed, I
wondered if I was misreading or misunderstanding what was really
happening. So
I decided that while the math showed the logic was correct, I wanted
real world
data. At about this same time I became convinced that the standard
audio chain
in the typical SW was at best "crap". I had doubted the observations at
Kiwa
about capacitors improving intelligibility of weak signals. I found
that by pulling the
audio straight off the detector diode and feeding it to a clean MSOFET
amp,
stations that were un-intelligible "mush" were clearer. I played with
better AM
detectors wanting to avoid the hassle of a synchronous detector, but in
the end
bowed to reality. I built an outboard synch detector, and with each
improvement
I found I could dig out weaker, or at least "mushier", stations. The
remote ISM
beacon started out as a SSB unit, but due to some drift after 3 months
of operation
I converted it to a very linear AM unit. Nothing fancy, I was given a
Rio PMP300 with
a 64Meg memory card. The whole project was based on the remote ISM
test set a
Radio Astronomer friend had used. But I wanted real voices signals, not
"random"
noise.

After all my experiments I came back around to the observation that in
most
cases, the local man made noise floor sets the limit on reception.
Better
detectors allow you to understand slightly weaker signals. But the
improvement,
while very worth while, is at best maybe 6dB. And that 6dB is really
optimistic
under ideal situations. I had a AOR7030+ in my care for a 5 weeks while
our
friend arranged shipping to NZ. The AOR7030+ is a much better receiver
then
my R2000. And I would give a left whatever to own one. But inspite of
the better
selection of IF filters, a quiter RF/IF section and greatly improved
detection and
audio chain, there were very few signals that I could understand on the
AOR
and not on the R2000 with the added InRad 2.1KHz SSB filter.

It has been an odd autum. We have had 3 power outages since the 1st of
Oct
and I have been home to listen through all three of them. The last one
lasted from
8:00PM until 5AM. Needless to say I missed work the next day. It never
ceases
to amaze me how much the low level AC grunge covers, and how many very
weak
signals you can receive when the lights are out.

I really enjoyed the last, long lights out event as I could compare my
R2000s to the
AOR. The AOR is a much better receiver, if you have a low enough local
noise floor.
Under these conditions the superority of the AOR stood out. It wasn't
that I couldn't
dig out most of the signals on the R2000, it was just a LOT harder. I
am not
complaining mind you, it was educational to see what a first class
receiver can do.
It also helped me decide to take a serious look at selling our place
rolling the excess back into TIAA and moving to the sticks.

The main advantage a synchronous detector offers is the reduced ear
fatigue.
With a standard diode detector I found that it felt like my head
clogged up
after listening to weak, nasty stations. The other advantage is the
music we
recover is mush cleaner. My wife plays flute and after listening to
some flute
music on a Peruvean station she admited that was the "cleanest SW I
have
heard. It sounded like the flutest was in the room with us." She had
doubted
the practicality of my summer long experiments. She had enjoyed SW but
thought that distant stations had to sound "bad". But since it was the
hottest
summer we have had, we weren't going outside that much.s she thought it

made more sense for me to play detector then antenna builder. She uses
"my"
gear in the day when I am not at home and I had to give her the 3rd
R2000 I
traded for so she can listen to what she wants when I am at home.

The last R2000 has the AD607 synch detector mounted inside with a
homebrew
5W mosfet AF amp. It sounds pretty darn sweet.

Terry