RHF wrote:
snip
So The Question Becomes : Will You Contribute and Post that
One Message a Day or Be One of those to Reply and Comment
- - - Will You ? ? ? - - - It Begins With You - - - Be Their ! ! !
snip
---------------------
I am trying to work up my nerve for a certain on topic flame war over
"power dividers", signal spliters, "passive multiset couplers" or as us
engineers like to call them, "hybrids" and thier possible use in a
"normal"
SW environment.

It is rather counter intuitive.

I am still trying to find a valid, acceptable "on line" refference for
typical
natural HF noise floor. Step one was to get everyone to agree that a
good
hybrid only introduces 3+dB of loss. That was way too much fun.

Terry

In article . com,
wrote:

RHF wrote: snip
So The Question Becomes : Will You Contribute and Post that One
Message a Day or Be One of those to Reply and Comment - - - Will
You ? ? ? - - - It Begins With You - - - Be Their ! ! !
snip --------------------- I am trying to work up my nerve for a
certain on topic flame war over "power dividers", signal spliters,
"passive multiset couplers" or as us engineers like to call them,
"hybrids" and thier possible use in a "normal" SW environment.

It is rather counter intuitive.

I am still trying to find a valid, acceptable "on line" refference
for typical natural HF noise floor. Step one was to get everyone to
agree that a good hybrid only introduces 3+dB of loss. That was way
too much fun.

I think that was me arguing with you on the news group. I just was not
paying attention to the power loss due to the fact that I used the
resistive type in small signal work and just did not pay attention to
that aspect (power lost) of dividers.

The magnetically coupled units were a little over 3dB and the resistive
were a little over 6 dB due to the resistor losses best case(s). The
3dB point being half the power because the source is divided in two.
The resistors used in the "resistive" units burn half the power (again)
in order to cause the impedance thru the splitter to look like 50 ohms
on all ports with the proper source and loads attached otherwise there
would be large reflections. The magnetic coupled units just transfer
the load impedance thru the unit so as long as the source and load
impedances match up that is all that is required. Well, the path
through the windings also is supposed to be the same impedance for
higher frequencies at least.

What is counter intuitive to you about either kind of
splitter/combiner?

On the news group we should take care to reference typical natural HF
noise floor and receiver sensitivity in dBm so the addition of
components like splitters can make sense in an antenna system way.

--
Telamon
Ventura, California

Devil Finder .Com = http://www.devilfinder.com/

SEARCH : First Commercially available Shortwave Radio
http://www.devilfinder.com/find.php?...twave +Radio+
.. . . and what is in the middle of Page One of the Search Results :

Welcome to Rec.Radio.Shortwave (AM/FM DXing)
http://www.faqs.org/faqs/radio/monitoring/am-fm-dxing/
However, most recent radios, even those designed for
quality shortwave reception, ... Ferrite loops, however,
are available commercially from at least two ...

Welcome to rec.radio.shortwave (AM/FM DXing)
http://www.faqs.org/faqs/radio/monitoring/am-fm-dxing/

it's a small world after all ~ RHF

Cuhulin - Sorry forgot the word "KIT" - my bad ~ RHF

SEARCH : First Commercially available Shortwave Radio Kit
http://www.devilfinder.com/find.php?...ve +Radio+kit

THE KNIGHT KIT PAGE
http://www.geocities.com/CapeCanaver...ham/knight.htm

Terry [R2000SW] - You have writtten a lot to think about ~ RHF

RHF wrote:
Terry [R2000SW] - You have writtten a lot to think about ~ RHF
.
.
. .

I should repost this so it is clear what the topic is.
Only trouble is I suspect there will then be two threads on the same
topic. It is going to get confusing and heated enough.

Terry .

In article . com,
wrote:

Telamon wrote:

What is counter intuitive to you about either kind of
splitter/combiner?

On the news group we should take care to reference typical natural
HF noise floor and receiver sensitivity in dBm so the addition of
components like splitters can make sense in an antenna system way.

-- Telamon Ventura, California
------------------------------------------------ I had inteneded to
be able to post on line reffences to every dB figure I use, but I had
to go open my big mouth first.
-----------------------------------------------

The common wisdom is that 4dB, I am calling it 4 becuase it is
slighltly over 3dB, of additonal loss will impact reception of weak
signals. In most listening locations the limit to recption is the
local noise floor. Even for a modest receiver like the R2000, the
receivers noise floor is significantly below the atmospheric noise
floor. I have a 1970 copy of ""Reference Data for Radio Engineers",
but I am trying to find a on link refference that everyone could see.
My "Refference Data" says the winter noise floor in my location
should be around -111dB with a 3KHZ BW at 10MHz. Sherwood Engineering
rates the R2000 as having a -130dBm noise floor in SSB, nominal 3KHZ
BW. I have checked 5 R2000s and they all at least meet this
minimium spcification. Most are slighlty better.

So disregarding any local QRM, we have: A system noise floor of
-111dBm. A receiver with a noise floor -130dBm. We have a margin
19dBm.

It is my contention, based on several years of tests, in a
laboratory, and "real world" tests overthe last 6 months, that
adding an additional 4dBm of attenuation will have "no" effect on
reception.

Repeated tests with a remote RF source, a micropower ISM/HiFER
"beacon", with the beacon RF output reduced to where the audio is
barely just intelligible show that an additonal 4dB of loss has not
effect.

A friend's daughter is a speech pathologist/therapist. She recorded a
20 pairs of words to test for "Percentage Articulation Loss of
Consonants" (AKA %AlCons). Words like copy and coffee.

I edited these into sets with each word being first in one set, and
second in another. Each group consisted of 4 words with a modulated
CW group ID at the end. The procedure consisted of reducing the RF
level of the beacon to the minimim level that I could get 90%
accuracy. Then adding the 4dB pad to see if it effected the
accuracy.

"Common sense" argues that any additional loss whould have an effect
on reception. My test results proved to me that that is just not
true.

If one has a locaton where the noise floor approaches, or is lower
then, the receiver noise floor, then and only then will addtional
loss effect reception.


I worked out a formula but ASCII is very poor for sub/super-script.

A wordy version could be: As long as the additional loss in dB is
less then the margin of RecNF-AntNF, then reception will be
uneffected.

This set of experiments also showed that the local noise floor is the
single most imoportant factor in SW/HF recption.

For instance, if the expected noise floor is -111dB, and the receiver
NF is 130dBm, but the real noise floor is -100dBm, then nothing below
-100dBm will be detected. Fairly obvious but not often realised.

My HiFer "beacon"/"remote RF source" consists of a Rio PMP300, a SSB
exciter and buffer feeding an electronic attenuator that is
controlled by a DTMF from a 2Mtr HT. The voice samples are 256K MP3
files normalised at 60% with the MCW at 95%. The unit is located
about 1.5 miles from me feeding a modified CB ground plane. I manualy
adjusted the RF output level for the lowest signal that my wife could
understand. This way I could add known amounts of attenuation via my
HT DTMF. It is true that such a close RF signal had no multipath to
complicate the issue, but I think my effort demonstrates why a few dB
of additional loss have minimal effect on HF reception.

It is also worth noting that adding more antenna wire did not effect
the detection of the weakest signal because more wire gave more
signal, but also gave an matching increase in noise. A test loop
antenna did allow the output level to be reduced another ~10 dB while
keepng the same level of intelligibility. A small active dipole
achieved the same ~10dB improvement. I would love to test a Welbrook
loop. At best my simple loop was a marginal antenna. Such a remote RF
surce also allowed me see that a PCR1000 really benefited from a
MW/BCB reject filter.

Let the flames roar.

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

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

Well,you gotta hit it in the middle if ya wanna get a little.

Here is another one I thunked up out of the top of my head bone.
www.devilfinder.com
List all of Shortwave Radio Frequencies
cuhulin

I own a half acre of land in Putnam County,Florida,sort of "out in the
sticks". That area is growing in population though.It was about 5,000
population when I bought my half acre,I wouldn't be supprised if it is
about 7,000 or 8,000 population nowdays.Everybody wants to get away from
the rat race of the big cities.
cuhulin