On Tue, 26 Oct 2004 00:19:28 GMT, asym said
in rec.radio.scanner:

than at lower ones. Even "crappy" RG8 only has a loss of around 5db @
400mhz for a 100ft run. 5db is enough that you'd notice, but it's
about the smallest amount that you *could* notice.

3db is 50%, or one "S" unit - easy enough to notice. Actually, the
receiver capture ratio is the smallest amount you'll notice, so the
better the receiver, the smaller the change it takes to make a big
difference.

(If the capture ratio is, say, 2db, if the signal increases from the
noise level to 2db above the noise level, what you hear changes from
quite noisy to dead full quieting - very noticeable. If the capture
ratio of the receiver is under 1db, it takes less than 1db change to
make the above difference.)

BTW, the advantage of a discone is that it's a good match at just
about all the frequencies we're interested in. It's not much of an
antenna - it's more of a matching device between the end of the cable
and space.

On Tue, 26 Oct 2004 01:41:58 GMT, Al Klein wrote:

On Tue, 26 Oct 2004 00:19:28 GMT, asym said
in rec.radio.scanner:

than at lower ones. Even "crappy" RG8 only has a loss of around 5db @
400mhz for a 100ft run. 5db is enough that you'd notice, but it's
about the smallest amount that you *could* notice.

3db is 50%, or one "S" unit - easy enough to notice. Actually, the
receiver capture ratio is the smallest amount you'll notice, so the
better the receiver, the smaller the change it takes to make a big
difference.




(If the capture ratio is, say, 2db, if the signal increases from the
noise level to 2db above the noise level, what you hear changes from
quite noisy to dead full quieting - very noticeable. If the capture
ratio of the receiver is under 1db, it takes less than 1db change to
make the above difference.)

Yes, that's absolutely true. What I mean is basically, you're going
to be in the near field for a lot of transmission sources that create
a higher noise floor than is anywhere near optimal, most of the time..
so you'll never hear those weak stations. Low loss cable will not
help in this case, because the noise is attenuated as much as the
signal. If the S/N coming in is 3:1, then it will still be 3:1 after
the cable, it doesn't matter if the cable introduces 1dB or 10dB of
loss.

If your reciever sensitivity isn't up to snuff, then a lot of times it
doesn't matter how short or long your cable run is, or if it's high or
low quality.


BTW, the advantage of a discone is that it's a good match at just
about all the frequencies we're interested in. It's not much of an
antenna - it's more of a matching device between the end of the cable
and space.

Isn't that what an antenna is really all about anyway, any kind of
antenna? Some are designed to be directional and give you some amount
of gain, but in the end, they are there to capture waves -- to
interface the cable with space.

Hi,

I'm no expert, but for whatever it's worth, I've tried
a R/S Disconne and also a Scantenna, side by side, in my attic.

The scantenna is better on all bands for my 780 Scanner.

Frankly, not by orders of magnitude better, but discernably "better".

Bob
---------------------
"asym" wrote in message
...
On Tue, 26 Oct 2004 01:41:58 GMT, Al Klein wrote:

On Tue, 26 Oct 2004 00:19:28 GMT, asym said
in rec.radio.scanner:

than at lower ones. Even "crappy" RG8 only has a loss of around 5db @
400mhz for a 100ft run. 5db is enough that you'd notice, but it's
about the smallest amount that you *could* notice.

3db is 50%, or one "S" unit - easy enough to notice. Actually, the
receiver capture ratio is the smallest amount you'll notice, so the
better the receiver, the smaller the change it takes to make a big
difference.




(If the capture ratio is, say, 2db, if the signal increases from the
noise level to 2db above the noise level, what you hear changes from
quite noisy to dead full quieting - very noticeable. If the capture
ratio of the receiver is under 1db, it takes less than 1db change to
make the above difference.)

Yes, that's absolutely true. What I mean is basically, you're going
to be in the near field for a lot of transmission sources that create
a higher noise floor than is anywhere near optimal, most of the time..
so you'll never hear those weak stations. Low loss cable will not
help in this case, because the noise is attenuated as much as the
signal. If the S/N coming in is 3:1, then it will still be 3:1 after
the cable, it doesn't matter if the cable introduces 1dB or 10dB of
loss.

If your reciever sensitivity isn't up to snuff, then a lot of times it
doesn't matter how short or long your cable run is, or if it's high or
low quality.


BTW, the advantage of a discone is that it's a good match at just
about all the frequencies we're interested in. It's not much of an
antenna - it's more of a matching device between the end of the cable
and space.

Isn't that what an antenna is really all about anyway, any kind of
antenna? Some are designed to be directional and give you some amount
of gain, but in the end, they are there to capture waves -- to
interface the cable with space.

On Tue, 26 Oct 2004 04:27:23 GMT, asym said
in rec.radio.scanner:

If your reciever sensitivity isn't up to snuff, then a lot of times it
doesn't matter how short or long your cable run is, or if it's high or
low quality.

All of them enter into it. A 30 element LPV with lossless cable,
feeding a receiver with a terrible noise figure, won't let you hear
very much.

BTW, the advantage of a discone is that it's a good match at just
about all the frequencies we're interested in. It's not much of an
antenna - it's more of a matching device between the end of the cable
and space.

Isn't that what an antenna is really all about anyway, any kind of
antenna?

That's *all* a discone is. Most antennas have some gain, even if it's
just the 3dbi of a dipole or ground plane.

Al Klein schrieb:

3db is 50%, or one "S" unit - easy enough to notice. Actually, the
receiver capture ratio is the smallest amount you'll notice, so the
better the receiver, the smaller the change it takes to make a big
difference.



6 dB is the difference of one S-Unit. That's 25% of the Signal with one
more of S-Units.
For reception only purposes it's insiders knowledge to use _much_
cheaper lowloss tv-cable with 75 ohms runnig to a discone antenna. You
will hardly notice any loss for impedance mismatching as the impedance
curve of consumer grade scanners vary a lot from the 50 ohms.

Volker Tonn wrote:

Al Klein schrieb:

3db is 50%, or one "S" unit - easy enough to notice. Actually, the
receiver capture ratio is the smallest amount you'll notice, so the
better the receiver, the smaller the change it takes to make a big
difference.


6 dB is the difference of one S-Unit. That's 25% of the Signal with one
more of S-Units.
For reception only purposes it's insiders knowledge to use _much_
cheaper lowloss tv-cable with 75 ohms runnig to a discone antenna. You
will hardly notice any loss for impedance mismatching as the impedance
curve of consumer grade scanners vary a lot from the 50 ohms.

Use the very best 50 ohm coax you can afford.

dxAce
Michigan
USA

dx'tard wrote:

Use the very best 50 ohm coax you can afford.

bull****...

Volker Tonn wrote:

dx'tard wrote:

Use the very best 50 ohm coax you can afford.

bull****...

Well, in your previous post you stated that "You will hardly notice any loss..."

That implies that one WILL notice...

It's been my experience that the best thing to do would be to go with the best
50 ohm coax you can afford.

But heck, I've only been doing this darn radio stuff for a few months, so what
the hell do I know?

dxAce
Michigan
USA

dxAce schrieb:


Volker Tonn wrote:


dx'tard wrote:


Use the very best 50 ohm coax you can afford.

bull****...


Well, in your previous post you stated that "You will hardly notice any loss..."

That implies that one WILL notice...

Loser! You should quote correctly -not destroying the content- 'tard.
A 50 ohm AirComm-plus cable costs three times as much as a lowloss 75
ohm TV-cable with the same loss.
And it gives pretty much the same results -if not better- on a broadband
antenna like a discone on consumer grade VHF/UHF-receivers wich do not
have a straight 50-ohm impedance. In most cases it varies between 30 and
150 ohms depending on the frequency you are receiving. So there is a
good chance a 75 ohm cable works even better than a 50 ohm cable with
the same loss. In worst case you will have an impedance mismatch loss of
3dB, but in most cases you will have a 3dB win depending on the scanner
you are using and frequency you are receiving.
There are few scannists who would buy or can afford a 0,70 US$/ft cable
for a 100ft run. So a good (lowloss!) TV-cable is really worth a try.

Volker Tonn wrote:

dxAce schrieb:


Volker Tonn wrote:


dx'tard wrote:


Use the very best 50 ohm coax you can afford.

bull****...


Well, in your previous post you stated that "You will hardly notice any loss..."

That implies that one WILL notice...

Loser! You should quote correctly -not destroying the content- 'tard.
A 50 ohm AirComm-plus cable costs three times as much as a lowloss 75
ohm TV-cable with the same loss.
And it gives pretty much the same results -if not better- on a broadband
antenna like a discone on consumer grade VHF/UHF-receivers wich do not
have a straight 50-ohm impedance. In most cases it varies between 30 and
150 ohms depending on the frequency you are receiving. So there is a
good chance a 75 ohm cable works even better than a 50 ohm cable with
the same loss. In worst case you will have an impedance mismatch loss of
3dB, but in most cases you will have a 3dB win depending on the scanner
you are using and frequency you are receiving.
There are few scannists who would buy or can afford a 0,70 US$/ft cable
for a 100ft run. So a good (lowloss!) TV-cable is really worth a try.

Shove it, NAZI boy!

dxAce
Michigan
USA