Lostgallifreyan wrote:
Michael Coslo wrote in
:

Lostgallifreyan wrote:
No. It's called 'go see for yourself and tell me based on YOUR
judgement if it's worth revisiting'. If all I wanted was a pat on the
head I wouldn't even have provided a link. Either that info has
technical merit, or it doesn't in which case perhaps you should berate
THEM and not me!
Of course it has no technical merit, it is just words! Some of them are
pretty ambiguous too, like that "video Frequencies" bit. Are the video
frequencies they refer to The frequencies that television signals are
broadcast or are tehy the frequencies that a video signal uses. THere is
a difference.

There's more. From that paragraph above, your not asking us to do your
research for you, are you?

- 73 de Mike N3LI -


It's not that bad. I've seen far worse. And no, I'm not asking you or anyone
else to do anything. When I'm not checking here and replying I'm reading
other stuff. I'll doing more of that because it doesn't argue so much.

It's much better to see numbers than what some website is telling you.
There are a lot of really smart people in here, and yes, if you do
something that isn't right, you're going to hear about it.

I thiink you'll find that these sites that don't argure with you are
happy when you buy something from them. But it's your call.

- 73 de Mike N3LI -

Lostgallifreyan wrote:
Michael Coslo wrote in
:

Richard Clark wrote:

We have your dozen or more suppositions filtered through anonymous and
linked-to sources of indifferent quality that each in their own right
have issues with a spectrum of cable types

I read that as "suppositories" instead of suppositions, Richard. Perhaps
both may be right? 8^)


Careful. Don't worry about mine, worry about the one you might seem to be
licking.


I've always thought those little wax bottles with the flavored water in
them were kind of distasteful for the same reason.

- 73 de Mike N3LI -

Michael Coslo wrote in
:

Lostgallifreyan wrote:
Jeff wrote in
:

Apparently no-one knows the impedance of a Sangean ATS-909 radio, I've
asked several people, at least one of whom specialises in modifying
that radio.

Perhaps there is a reason. It isn't terribly important at all.


Which is why I think no-one stated it too. One person here said it wasn't
stated perhaps because no-one I suggested was adept was actually adept enough
to do it. These are the contradictions I keep seeing. They tend to gravitate
around a poster's ideas as pecived by a reader, rather than by science. I
think you're right in this case, so I'm not arguing.

Looks like 1K is best guess based on schematic. Loss won't bother me so
much as SNR. Several people advised that a 15 foot vertical whip is
likely to overload the input so loss is not my main concern.

Not to be overly precise, but the whip won't overload your radio, strong
signals might. Those little radios are pretty sensitive.


Yes. Which is why I'm looking at getting signals from outside rather than
inside. I don't mind losses so much.

So what are you trying to do here, aside from get an external signal
into a radio? If you want to have an audiophile grade antenna system,
you need to go out and get some good hardline coax*. You can also make
some measurements to determine the exact input impedance of your radio,
then construct a balun to match it to the rest of the system. If
measurement isn't your thing, you can probably get by with a 9:1 balun,
as a back of the envelope calculation.


Going to try that. Winding enamelled wire onto a few bought ferrite torroids
isn't exactly hard work. There will be one at the antenna end too.

Then if you can put them in, you need around 120 radials that you use
for the ground on your antenna. You can either elevate them, lay them on
the ground, or shallow bury them. If you have a wife the third option is
probably what you want to do.

There are other little tweaks, such as silver contacts, a good quality
tuner, and probably some I haven't thought about yet. Some still hold
out for low oxygen copper.

Do all that, and you can still do pretty close to the results with a
long wire hanging out of your window.


Radials, yes, where I have room for them. I don't have any need for 'OFC'
wire, in anything. Or silver, come to that.. Maybe if I met a warewolf? Or is
it vampires? Silver was supposed to be good against one or the other..

Now if you get a communications grade radio, some of my less tongue in
cheek suggestions might help more. But make no mistake, you are deep
into the world of diminishing returns.


Apart from a few bits of ferrite and a coax, and a whip to get upwards reach
in a space where sidewards reach can't do much good, I'm not after much. I'm
pretty sure it will beat hanging the wire out the window of a house full of
modems and computers and other RFI generators.

note 1.

Coolest hardline I ever saw was at a TV station. It was about a foot in
diameter on the jacket, and I didn't see the center conductor, but my
best guess is that it was around 2 inches in diameter.


Curious. If they were that worried about resistive losses, they'll be high on
the buyer list for room temperature superconductors if they think they'll
help.

note 2.

I'm not trying to be rude, but you've been getting some good info in
here, you're just not taking it. Reminds me of some of the students
coming out of college these days with a nice fresh bachelor's degree.
They don't accept input, and think they should be promoted for showing
up on time.


I'm not complaining about the info. Already said I came here because I
thought the SNR was better. But there's also enough contradiction in advice
I've seen to suggest a considerable mismatch. So taking all of it is not only
unwise, but perhaps impossible.

Michael Coslo wrote in
:

Lostgallifreyan wrote:
Michael Coslo wrote in
:

Richard Clark wrote:

We have your dozen or more suppositions filtered through anonymous and
linked-to sources of indifferent quality that each in their own right
have issues with a spectrum of cable types

I read that as "suppositories" instead of suppositions, Richard. Perhaps
both may be right? 8^)


Careful. Don't worry about mine, worry about the one you might seem to be
licking.


I've always thought those little wax bottles with the flavored water in
them were kind of distasteful for the same reason.


Ok, now I'm really lost, but never mind.. Wax bottles? Flavoured water? Don't
make me regret I asked.

Michael Coslo wrote in
:

It's much better to see numbers than what some website is telling you.
There are a lot of really smart people in here, and yes, if you do
something that isn't right, you're going to hear about it.


Even experts can see either too much or too little of context. Give them
either, they'll want the other.

I thiink you'll find that these sites that don't argure with you are
happy when you buy something from them. But it's your call.


Well, there is that, but the info is free, I'm not actually buying from them,
and a lot of the really technical stuff is in places I couldn't see unless I
paid for access. I figure that I just sound out what I can, and make my own
call, like you said.

Lostgallifreyan wrote:
Michael Coslo wrote in
:

Lostgallifreyan wrote:
Michael Coslo wrote in
:

Richard Clark wrote:

We have your dozen or more suppositions filtered through anonymous and
linked-to sources of indifferent quality that each in their own right
have issues with a spectrum of cable types
I read that as "suppositories" instead of suppositions, Richard. Perhaps
both may be right? 8^)

Careful. Don't worry about mine, worry about the one you might seem to be
licking.

I've always thought those little wax bottles with the flavored water in
them were kind of distasteful for the same reason.


Ok, now I'm really lost, but never mind.. Wax bottles? Flavoured water? Don't
make me regret I asked.

They're about 2 and a half inches long, made of wax and look a little
like the nasty things we're joking about. Kids bite the top off, and
drink th esmall amount of flavored water in them.

- Mike -

Michael Coslo wrote in
:

Lostgallifreyan wrote:
Michael Coslo wrote in
:

Lostgallifreyan wrote:
Michael Coslo wrote in
:

Richard Clark wrote:

We have your dozen or more suppositions filtered through anonymous
and linked-to sources of indifferent quality that each in their own
right have issues with a spectrum of cable types
I read that as "suppositories" instead of suppositions, Richard.
Perhaps both may be right? 8^)

Careful. Don't worry about mine, worry about the one you might seem
to be licking.

I've always thought those little wax bottles with the flavored water
in them were kind of distasteful for the same reason.


Ok, now I'm really lost, but never mind.. Wax bottles? Flavoured water?
Don't make me regret I asked.

They're about 2 and a half inches long, made of wax and look a little
like the nasty things we're joking about. Kids bite the top off, and
drink th esmall amount of flavored water in them.


I think I've seen something like them, though in some kind of clear pliable
plastic. Usually flat and flaccid by the time I see them in the streets.
Definitely unsavoury... I mean, they don't look exactly like a used condom,
but the older I get, the more I wonder about some of the stuff that kids find
fun to eat.

Because I want to reduce the noise from stuff in the bulding compared to
whatever hits the whip antenna. Sure, attenuation might reduce SNR in a noisy
resistance (or subsequent gain stage) but NOT due to due to simple shrinkage
of scale (R = Ratio...), but that's why I want to get the SNR higher to start
with. It's the separation of internal noise signals from external wanted
signals that matters, same as for anyone using coax. Surely it's not suddenly
wrong because I'm doing it? If so, this isn't about science anymore.



Well firstly, adding an attenuator WILL degrade the Noise Figure of your
receiver.

Now whether this will have any significance depends on the original NF
of the receiver, and the level of External noise (atmospheric and man made).

It we take your 'ideal' set-up where you have eliminated the pick-up in
the building; you SNR will depend on the NF of the rx and the levels of
signal and received noise at the antenna.

So if we have to put an attenuator in line to make the rx happy so it
does not overload, then we will have degraded the rx's NF by the value
of the attenuator. So say a 10db attenuator will have degraded you NF by
10dB. It will also have degraded the level of input signal by 10dB, so
you have a double wammy.

Now the effect on your SNR will depend on which band you are listening
on ant the level of atmospheric noise compared to the NF of the rx. At
lower frequencies the effect will be less because the atmospheric noise
is greater and will swamp the rx NF to some degree. As you go up in
ferquency the NF will start to become dominant.


If we take the case of leaky coax and pick-up in the building, sure the
picked up noise will degrade the SNR, but the leakage is likely to be
very small in absolute level and adding any attenuation will take it
below the noise floor anyway. The differences in leakage between the
types of coax under discussion will be insignificant compared to the
attenuation values you will have to add to make the rx happy. That is
why I questioned the choice or rx, having to add attenuation negates the
need to have the ultimate in screening unless the pick-up is a very
high level (in which case you are stumped anyway).

Also if your building is that noisy then there will be significant noise
pick-up directly into the antenna which you can do nothing about. There
is a significant possibility that this will be much greater than any
direct leakage into the cable making such pick-up insignificant.

Perhaps you should tell us why you think there will be this pick-up and
what you think the source is in the building. That will help you get a
sensible answer.

One final point, you say "It's the separation of internal noise signals
from external wanted signals that matters, same as for anyone using
coax." I suspect that is about the last thing that most people think
about when choosing coax, they normally think about the impedance first,
then the transmission loss, size and cost. I doubt if the "the
separation of internal noise signals from external wanted signals"
crosses their minds at all!!

Jeff

On Thu, 04 Feb 2010 09:20:10 +0000, Jeff
wrote:

One final point, you say "It's the separation of internal noise signals
from external wanted signals that matters, same as for anyone using
coax." I suspect that is about the last thing that most people think
about when choosing coax, they normally think about the impedance first,
then the transmission loss, size and cost. I doubt if the "the
separation of internal noise signals from external wanted signals"
crosses their minds at all!!

Hi Jeff,

You will undoubtedly have two camps there. As for those expecting
"the separation of internal noise signals from external wanted signals"
then they will be dissappointed or live happily with illusion; and the
others will, as you say, will select their transmission line (not
solely a coax) on the basis of those qualities they can expect it to
deliver.

The reason why I opened this up to include parallel line is that too
much superstitious quality has been attached to a shield. This has
been tangentially supported by measure of the cable transfer impedance
with the hope of using that to predict shielding efficiency. The
ordinary reader is left with the impression that by focusing on a
shield that the state of shielding is defined at the alter of the
coax. It is not.

"Cable transfer impedance" is measured in a highly defined manner with
an example of a very good graphic found at:
http://www.emcconsultinginc.com/docs/beldenTiAndSe.pdf

Replace the well grounded coax with a parallel line with its balanced
load and balanced source, and the transfer impedance for that system
will reveal shielding efficiencies easily equal to, or better than,
coaxial cables. That efficiency will vary by the degree to the
proximity of the parallel line to the ground plane, and its geometry.
This geometry is manageable with parallel lines, the coax has to live
with what it has.

Now, this counter argument is based upon the premise of the near
sighted quest for some goal that is achieved by the coaxial line alone
- in other words, a folly. However, what this counter argument does
is penetrate the balloon of complacency surrounding the investment of
superstitious qualities in successive layers of shielding. Without
care, those extra layers can inject MORE noise into the system than
that which exists in the environment. I have already written and
supplied reference to that unfortunate side effect to no obvious
comment about this paradox.

73's
Richard Clark, KB7QHC