Time Warner truck
 

Today I saw a Time Warner Cable minivan trolling through the neighborhood.

It appeared to have a four antenna DF array on the roof with vertical
lengths of about 2-3 feet.

What's up with that?

Time Warner truck
 

On Tue, 27 Aug 2013 08:41:02 -0700, "Wayne"
wrote:

Today I saw a Time Warner Cable minivan trolling through the neighborhood.

It appeared to have a four antenna DF array on the roof with vertical
lengths of about 2-3 feet.

What's up with that?

It's a doppler direction finder array, used to locate cable leaks and
ingres (leakage into the cable). Something like these perahaps:
http://kn2c.us/radio-df-ddf2020t/
http://www.wavetracker.com
http://www.google.com/patents/US6801162



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Time Warner truck
 

"Jeff Liebermann" wrote in message
...

On Tue, 27 Aug 2013 08:41:02 -0700, "Wayne"
wrote:

Today I saw a Time Warner Cable minivan trolling through the neighborhood.

It appeared to have a four antenna DF array on the roof with vertical
lengths of about 2-3 feet.

What's up with that?

# It's a doppler direction finder array, used to locate cable leaks and
# ingres (leakage into the cable). Something like these perahaps:
# http://kn2c.us/radio-df-ddf2020t/
# http://www.wavetracker.com
# http://www.google.com/patents/US6801162

Ah yes, mystery solved. The antenna array looked exactly like a
"Wavetracker".

Thanks

Wayne W5GIE
Redlands, CA

Time Warner truck
 

"Jeff Liebermann" wrote in message
...
On Tue, 27 Aug 2013 08:41:02 -0700, "Wayne"
wrote:

Today I saw a Time Warner Cable minivan trolling through the neighborhood.

It appeared to have a four antenna DF array on the roof with vertical
lengths of about 2-3 feet.

What's up with that?

It's a doppler direction finder array, used to locate cable leaks and
ingres (leakage into the cable). Something like these perahaps:

I didn't see the Cox survey van on my street but their tech paid me a visit.
I didn't appreciate the extent of it but my interior cabling was leaking.
The tech came to the door and said he had to do some testing on the pole
that would knock out all our services for a few minutes. Was that OK? (Yes)

He reported that my house was the source of leakage that had earlier been
detected by their vehicle. (Oops) He asked if we had any broadcast ingress.
(Yes) Could he fix things inside the house? (Heck yes) He spent over an
hour reterminating some of my old stuff and running a few new pieces for me.
That got the leakage within limits and it made the ingress go away. (Yay)

"Sal"

Time Warner truck
 

Sal salmonella@food wrote:

"Jeff Liebermann" wrote in message
...
On Tue, 27 Aug 2013 08:41:02 -0700, "Wayne"
wrote:

Today I saw a Time Warner Cable minivan trolling through the neighborhood.

It appeared to have a four antenna DF array on the roof with vertical
lengths of about 2-3 feet.

What's up with that?

It's a doppler direction finder array, used to locate cable leaks and
ingres (leakage into the cable). Something like these perahaps:

I didn't see the Cox survey van on my street but their tech paid me a visit.
I didn't appreciate the extent of it but my interior cabling was leaking.
The tech came to the door and said he had to do some testing on the pole
that would knock out all our services for a few minutes. Was that OK? (Yes)

He reported that my house was the source of leakage that had earlier been
detected by their vehicle. (Oops) He asked if we had any broadcast ingress.
(Yes) Could he fix things inside the house? (Heck yes) He spent over an
hour reterminating some of my old stuff and running a few new pieces for me.
That got the leakage within limits and it made the ingress go away. (Yay)

"Sal"

And all that in the house of (supposedly) a radio amateur?

Over here the house cabling is the responsibility of the inhabitant.
The cabling company delivers signal to a demarcation point, in new houses
usually in the electricity metering cabinet, in older houses that were
later retrofitted with cable it is often on the outside wall of the living
room. Anything connected there you have to supply and maintain yourself.

The inhouse cabling and especially the connectors have been very
substandard at the time the cable network was deployed, which wasn't a
problem because there were few channels and they were positioned carefully
not to overlap with terrestrial transmission in the area. But when the
DVB-T network was deployed, new channels were used (there was parallal
Analog and DVB-T transmission for a while) and the cable networks were
fully allocated. So you often got a DVB-T transmitter on the same
channel as an analog cable channel, and those DVB-T transmitters are
in the cities instead of the usually more remote sites where the Analog
transmitters were.

Big trouble ensued, and everyone (who cares about picture quality)
was forced to buy new cabling and at least new connectors, that were
actually providing shielding.

This was a big boon for radio amateurs, because it reduced the amount
of all interference, not only from DVB-T to viewers but also from
radio amateurs to viewers and from the cable network to radio amateurs.
(on the cable network, channels are in use that overlap with the 2m
and 70cm amateur bands)

Time Warner truck
 

On Tue, 27 Aug 2013 23:24:20 -0700, "Sal" salmonella@food
poisoning.org wrote:

He spent over an
hour reterminating some of my old stuff and running a few new pieces for me.
That got the leakage within limits and it made the ingress go away. (Yay)

I've had to deal with cable leakage problems generating interference
to commercial services. Cable CH18 also covers the 2m band.

"Interference Report Card"
http://www.cablefax.com/tech/operations/bestpractices/14955.html
http://www.cablefax.com/tech/sections/columns/broadband/42840.html

Most of the time, it's the ring type crimp F connectors like this:
http://www.showmecables.com/images/catalog/product/F-Type-Connector-With-1-4-Inch-Crimp-Ring-RG59-4.jpg
that caused problems. Occasionally, some really bad RG-59/u with
maybe 50% coverage on the shield. Other times, it various cable
amplifiers, splitters, and devices, usually with unterminated ends or
ports. Lots of ways to do it wrong.

So, what did the Cox guy find? I'm nosey.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Time Warner truck
 

On 8/28/2013 11:42 AM, Jeff Liebermann wrote:
On Tue, 27 Aug 2013 23:24:20 -0700, "Sal" salmonella@food
poisoning.org wrote:

He spent over an
hour reterminating some of my old stuff and running a few new pieces for me.
That got the leakage within limits and it made the ingress go away. (Yay)

I've had to deal with cable leakage problems generating interference
to commercial services. Cable CH18 also covers the 2m band.

"Interference Report Card"
http://www.cablefax.com/tech/operations/bestpractices/14955.html
http://www.cablefax.com/tech/sections/columns/broadband/42840.html

Most of the time, it's the ring type crimp F connectors like this:
http://www.showmecables.com/images/catalog/product/F-Type-Connector-With-1-4-Inch-Crimp-Ring-RG59-4.jpg
that caused problems.

What type/style F connector would you recommend?

John KD5YI

Time Warner truck
 

"Jeff Liebermann" wrote in message
...

snip

So, what did the Cox guy find? I'm nosey.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

It was almost all leakage from ring-crimp connectors. (Your comments
contained your own answer :-) He replaced them with compression connectors,
probably the Snap-n-Seal from Belden.

I had a couple of pieces of RG-59 that he changed in favor of a better cable
from a spool he brought. Most of my runs were Belden 9275, which he said
was fine -- if terminated properly.

"Sal"

Time Warner truck
 

"Rob" wrote in message
...
He reported that my house was the source of leakage that had earlier
been
detected by their vehicle. (Oops) He asked if we had any broadcast
ingress.
(Yes) Could he fix things inside the house? (Heck yes) He spent over
an
hour reterminating some of my old stuff and running a few new pieces for
me.
That got the leakage within limits and it made the ingress go away. (Yay)

"Sal"

And all that in the house of (supposedly) a radio amateur?

Oh, it's even worse than that -- way worse. :-(

Yes, I'm a licensed amateur, Extra Class, even. In February, 2007, I passed
the Extra Exam on my first try without ever cracking a book. I'm a retired
engineer and I knew much of the technical stuff. I could afford some misses
on rules and still pass. I had studied for General because I wanted at
least General. I figured Extra could come later. As it worked out, "later"
was only about half an hour.

But it's even worse than that -- way worse. :-(

A major chunk of my working life was spent dealing with EMI detection and
correction. I was certified as an EMI Engineer by the National Association
of Radio and Telecommunications Engineers. I'd had to find and solve a
whole lot of "tough dogs" in my working life. I just hadn't bothered at
home. I always seemed to have something else to do.

Okay, now that I've humbled myself, you may proceed to bash me. Bashers are
requested to summarize their experience and involvement. Humor is allowed.

"Sal"
KD6VKW (KILO-DELTA-SIX-VICIOUS-KILLER-WEASEL)
B.S., Chapman University, 1989, Electronics
Volunteer Examiner
Emergency Services Volunteer (RACES)
Past President of South Bay Amateur Radio Society, SOBARS
Past Field Day Chairman of SOBARS
Past Treasurer of SOBARS
SOBARS repeater repairman
SOBARS weekly HF net control operator
Recovering Sailor, USN 21 yrs.
Elmer of many
Enemy of none
Newsgroup fun-lover
All-around good-guy

Time Warner truck
 

Sal salmonella@food wrote:

"Rob" wrote in message
...
He reported that my house was the source of leakage that had earlier
been
detected by their vehicle. (Oops) He asked if we had any broadcast
ingress.
(Yes) Could he fix things inside the house? (Heck yes) He spent over
an
hour reterminating some of my old stuff and running a few new pieces for
me.
That got the leakage within limits and it made the ingress go away. (Yay)

"Sal"

And all that in the house of (supposedly) a radio amateur?

Oh, it's even worse than that -- way worse. :-(

I often heard that IT is worst within IT companies :-)

Time Warner truck
 

On 8/28/2013 1:25 PM, Sal wrote:
"Jeff Liebermann" wrote in message
...

snip

So, what did the Cox guy find? I'm nosey.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

It was almost all leakage from ring-crimp connectors. (Your comments
contained your own answer :-) He replaced them with compression connectors,
probably the Snap-n-Seal from Belden.

I had a couple of pieces of RG-59 that he changed in favor of a better cable
from a spool he brought. Most of my runs were Belden 9275, which he said
was fine -- if terminated properly.

"Sal"


I had the same situation, my house was singing and the tech heard it
from a major road close to my house. The company was doing an upgrade
and were out correcting all the problems before the change.
The tech replaced 7 ring type connectors in my hot Fl, attic and one
inside where my router was connected.
The repairs eliminated an interference pattern on two channels.
The upgrade increased my internet speed.
I have since bought compression type connectors and a tool to install
them.
Mikek

Time Warner truck
 

On Wed, 28 Aug 2013 11:48:04 -0500, John S
wrote:

On 8/28/2013 11:42 AM, Jeff Liebermann wrote:
Most of the time, it's the ring type crimp F connectors like this:
http://www.showmecables.com/images/catalog/product/F-Type-Connector-With-1-4-Inch-Crimp-Ring-RG59-4.jpg
that caused problems.

What type/style F connector would you recommend?
John KD5YI

I steal mine directly from Comcast. I use whatever is available.

The problem is that many manufacturers have put considerable time and
effort into making their connectors as incompatible as possible with
their competitors connectors and tools. Fortunately, there several
good universal compression tools. This is what I settled on mostly
because it seems to fit all the various mutations and will also do BNC
and phono compression connectors:
http://www.ebay.com/itm/221178706506
It's the cheapest, of course. I have much better tools that I also
use, but the above tool works with most everything.

You'll also need a wire stripper.
http://www.ebay.com/itm/310711345790
Buy at least 2 of these, as they tend to wear out (or become borrowed)
rather rapidly.

For connectors, it appears that Comcast likes Thomas and Betts
Smash-N-Seal connectors.
http://www.ebay.com/itm/161090412893
Note that the connectors for RG-59 and RG-6/u are quite different.
There are also different types for double shielded and quad shielded
RG-6/u. Watch the video and you'll see the problem:
http://www.youtube.com/watch?v=HW3L61ydvzM
The SNS1P6U connector is a good choice, because it sorta fits all the
common types of RG-6/u. The compression tool shown in the video is
quite good, has a built in stripper, but will only do F connectors,
not BNC or phono. Plan on ruining a few connectors before you learn
how to use the tool. There are videos on YouTube for how to work with
compression connectors.

Drivel: All of my 50 ohm antennas on my roof are connected to their
respective radios with 75 ohm RG-6/u coax, F connectors, and various
adapters. Also some RG-6/u with BNC compression connectors. No
problems and very little additional mismatch loss.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Time Warner truck
 

"Jeff Liebermann" wrote in message
...
You'll also need a wire stripper.
http://www.ebay.com/itm/310711345790
Buy at least 2 of these, as they tend to wear out (or become borrowed)
rather rapidly.


I have several of them. Each one set for the several types of coax I use.
The price is from about $ 3 shipped from China to $ 15 for the ones already
in the US. I did find one problem with some of them, The brass bushings
on the bottom of the blades are not a very good fit in some of them and will
back out as you try to adjust them. Pull them out and put a drop of glue on
them and put them back in and the adjustments will hold.

Time Warner truck
 

"Rob" wrote in message
...
Sal salmonella@food wrote:

"Rob" wrote in message
...
He reported that my house was the source of leakage that had earlier
been
detected by their vehicle. (Oops) He asked if we had any broadcast
ingress.
(Yes) Could he fix things inside the house? (Heck yes) He spent over
an
hour reterminating some of my old stuff and running a few new pieces
for
me.
That got the leakage within limits and it made the ingress go away.
(Yay)

"Sal"

And all that in the house of (supposedly) a radio amateur?

Oh, it's even worse than that -- way worse. :-(

I often heard that IT is worst within IT companies :-)

"The shoemaker's son goes barefoot" -- A proverb that appears in many
languages.

Time Warner truck
 

"amdx" wrote in message
...

On 8/28/2013 1:25 PM, Sal wrote:
"Jeff Liebermann" wrote in message
...

snip

So, what did the Cox guy find? I'm nosey.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

It was almost all leakage from ring-crimp connectors. (Your comments
contained your own answer :-) He replaced them with compression
connectors,
probably the Snap-n-Seal from Belden.

I had a couple of pieces of RG-59 that he changed in favor of a better
cable
from a spool he brought. Most of my runs were Belden 9275, which he said
was fine -- if terminated properly.

"Sal"


I had the same situation, my house was singing and the tech heard it
from a major road close to my house. The company was doing an upgrade
and were out correcting all the problems before the change.
The tech replaced 7 ring type connectors in my hot Fl, attic and one
inside where my router was connected.
The repairs eliminated an interference pattern on two channels.
The upgrade increased my internet speed.
I have since bought compression type connectors and a tool to install
them.
Mikek

I have probably a hundred or so ring-crimp connectors for RG-59, RG-6 and
even some big ones for RG-11. I also have a half dozen crimpers, some found
as bargains andsome bought retail. (The quest for the perfect crimp tool is
a cruel journey.) I know I need to transition myself to better TV
connectors; I just hate to consign my existing stock to scrap. ... but
that's what it is, I guess.

What brand of crimper and connector(s)? Are you happy with them? [I had
typed just "Are you happy?" and realized it looked very Zen.]

I already had to do it for DC power. From a mishmash of mostly banana plugs
& jacks, plus some RCA plugs, I went to Anderson Powerpole connectors and
every time I pull out something I haven't used in a while, I grab the
Powerpole kit, too. I bought 50 connector pairs, 50 feet of Black/Red
12-gauge and a crimper at HRO. I like it. If the wires are small, I'll
solder lightly first, then crimp.

"Sal"

Time Warner truck
 

On 8/28/2013 10:15 PM, Jeff Liebermann wrote:
On Wed, 28 Aug 2013 11:48:04 -0500, John S
wrote:

On 8/28/2013 11:42 AM, Jeff Liebermann wrote:
Most of the time, it's the ring type crimp F connectors like this:
http://www.showmecables.com/images/catalog/product/F-Type-Connector-With-1-4-Inch-Crimp-Ring-RG59-4.jpg
that caused problems.

What type/style F connector would you recommend?
John KD5YI

I steal mine directly from Comcast. I use whatever is available.

The problem is that many manufacturers have put considerable time and
effort into making their connectors as incompatible as possible with
their competitors connectors and tools. Fortunately, there several
good universal compression tools. This is what I settled on mostly
because it seems to fit all the various mutations and will also do BNC
and phono compression connectors:
http://www.ebay.com/itm/221178706506
It's the cheapest, of course. I have much better tools that I also
use, but the above tool works with most everything.

You'll also need a wire stripper.
http://www.ebay.com/itm/310711345790
Buy at least 2 of these, as they tend to wear out (or become borrowed)
rather rapidly.

For connectors, it appears that Comcast likes Thomas and Betts
Smash-N-Seal connectors.
http://www.ebay.com/itm/161090412893
Note that the connectors for RG-59 and RG-6/u are quite different.
There are also different types for double shielded and quad shielded
RG-6/u. Watch the video and you'll see the problem:
http://www.youtube.com/watch?v=HW3L61ydvzM
The SNS1P6U connector is a good choice, because it sorta fits all the
common types of RG-6/u. The compression tool shown in the video is
quite good, has a built in stripper, but will only do F connectors,
not BNC or phono. Plan on ruining a few connectors before you learn
how to use the tool. There are videos on YouTube for how to work with
compression connectors.

Drivel: All of my 50 ohm antennas on my roof are connected to their
respective radios with 75 ohm RG-6/u coax, F connectors, and various
adapters. Also some RG-6/u with BNC compression connectors. No
problems and very little additional mismatch loss.



Thanks, Jeff. Valuable hints and advice.

Time Warner truck
 

Sal wrote:

What brand of crimper and connector(s)? Are you happy with them? [I had
typed just "Are you happy?" and realized it looked very Zen.]

Almost any compression connector or tool will do. You can get them cheaply
at DIY stores if you look.

If you want a better tool and connectors you can get them on eBay (buy
from vendors, not random auctions).

Basically there are 3 kinds:

RG-59, RG-6 (not Quad Shield) and RG-6 QS.

You can also get universal ones, e.g. a universal RG-59 which fits all
variants or a universal RG-6 one, which fits all RG6 variants including
including QS.

Tools are needed depending upon the connectors. Almost all of them use
a tool which holds the connector end and compresses the body from the cable
end. There are small lever ones which look like pliers and the compression
is done in a handle (works fine).

There are also ones that look like pliers and the connector fits in the top.
I use them for BNC connectors.

There also is a kind where the tool hold the connector near the cable end
and pushes it all into a block. I got it for RG-6 BNC and RCA connectors,
but prefer the other kind.

If you mix and match make sure the connectors fit the tool and vice versa.

Avoid the really cheap ones where the front compress into the back,
I got some with a kit and never was able to get them to work. Looking on
eBay now, they seem to be gone.

Geoff


--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379

Time Warner truck
 

On 8/28/2013 11:58 PM, Sal wrote:
"amdx" wrote in message
...

On 8/28/2013 1:25 PM, Sal wrote:
"Jeff Liebermann" wrote in message
...

snip

So, what did the Cox guy find? I'm nosey.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

It was almost all leakage from ring-crimp connectors. (Your comments
contained your own answer :-) He replaced them with compression
connectors,
probably the Snap-n-Seal from Belden.

I had a couple of pieces of RG-59 that he changed in favor of a better
cable
from a spool he brought. Most of my runs were Belden 9275, which he said
was fine -- if terminated properly.

"Sal"


I had the same situation, my house was singing and the tech heard it
from a major road close to my house. The company was doing an upgrade
and were out correcting all the problems before the change.
The tech replaced 7 ring type connectors in my hot Fl, attic and one
inside where my router was connected.
The repairs eliminated an interference pattern on two channels.
The upgrade increased my internet speed.
I have since bought compression type connectors and a tool to install
them.
Mikek

I have probably a hundred or so ring-crimp connectors for RG-59, RG-6 and
even some big ones for RG-11. I also have a half dozen crimpers, some found
as bargains andsome bought retail. (The quest for the perfect crimp tool is
a cruel journey.) I know I need to transition myself to better TV
connectors; I just hate to consign my existing stock to scrap. ... but
that's what it is, I guess.

What brand of crimper and connector(s)? Are you happy with them? [I had
typed just "Are you happy?" and realized it looked very Zen.]

I already had to do it for DC power. From a mishmash of mostly banana plugs
& jacks, plus some RCA plugs, I went to Anderson Powerpole connectors and
every time I pull out something I haven't used in a while, I grab the
Powerpole kit, too. I bought 50 connector pairs, 50 feet of Black/Red
12-gauge and a crimper at HRO. I like it. If the wires are small, I'll
solder lightly first, then crimp.

"Sal"

I bought my compression tool and connectors at Lowes. Installation
was fine, I have no clue about the shielding quality, just assume it's
better than the ring connectors.
Mikek

Time Warner truck
 

"amdx" wrote in message
...
On 8/28/2013 11:58 PM, Sal wrote:
"amdx" wrote in message
...

On 8/28/2013 1:25 PM, Sal wrote:
"Jeff Liebermann" wrote in message
...

snip

So, what did the Cox guy find? I'm nosey.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

It was almost all leakage from ring-crimp connectors. (Your comments
contained your own answer :-) He replaced them with compression
connectors,
probably the Snap-n-Seal from Belden.

I had a couple of pieces of RG-59 that he changed in favor of a better
cable
from a spool he brought. Most of my runs were Belden 9275, which he
said
was fine -- if terminated properly.

"Sal"


I had the same situation, my house was singing and the tech heard it
from a major road close to my house. The company was doing an upgrade
and were out correcting all the problems before the change.
The tech replaced 7 ring type connectors in my hot Fl, attic and one
inside where my router was connected.
The repairs eliminated an interference pattern on two channels.
The upgrade increased my internet speed.
I have since bought compression type connectors and a tool to install
them.
Mikek

I have probably a hundred or so ring-crimp connectors for RG-59, RG-6 and
even some big ones for RG-11. I also have a half dozen crimpers, some
found
as bargains andsome bought retail. (The quest for the perfect crimp tool
is
a cruel journey.) I know I need to transition myself to better TV
connectors; I just hate to consign my existing stock to scrap. ... but
that's what it is, I guess.

What brand of crimper and connector(s)? Are you happy with them? [I had
typed just "Are you happy?" and realized it looked very Zen.]

I already had to do it for DC power. From a mishmash of mostly banana
plugs
& jacks, plus some RCA plugs, I went to Anderson Powerpole connectors and
every time I pull out something I haven't used in a while, I grab the
Powerpole kit, too. I bought 50 connector pairs, 50 feet of Black/Red
12-gauge and a crimper at HRO. I like it. If the wires are small, I'll
solder lightly first, then crimp.

"Sal"

I bought my compression tool and connectors at Lowes. Installation was
fine, I have no clue about the shielding quality, just assume it's
better than the ring connectors.
Mikek


I have a Lowes. Thanks!

"Sal"

Time Warner truck
 

"Jeff Liebermann" wrote in message
...

snip

Drivel: All of my 50 ohm antennas on my roof are connected to their
respective radios with 75 ohm RG-6/u coax, F connectors, and various
adapters. Also some RG-6/u with BNC compression connectors. No
problems and very little additional mismatch loss.

Yes. My Field Day antenna two years ago was a 20m dipole at 30 feet, which
I first simulated with EZNEC. It was close to 75 ohms at the feedpoint,
typical of such a dipole, so I used RG-6 -- about 60 feet. The unadjusted
VSWR at the transmitter was near the expected 1.5:1. The TS-570 internal
tuner handled it instantly. (I was going to say "handled it in a flash," but
that's a bad, bad metaphor.)

RG-6 has a surprisingly low loss. See this:

http://vk1od.net/transmissionline/RG6/Fig01.gif

and note the lengths are in meters.

This page is interesting, too.

http://www.arrg.us/pages/Loss-Calc.htm

Use Belden 8215 for RG-6.

"Sal"

Time Warner truck
 

"Jeff Liebermann" wrote in message
...

Drivel: All of my 50 ohm antennas on my roof are connected to their
respective radios with 75 ohm RG-6/u coax, F connectors, and various
adapters. Also some RG-6/u with BNC compression connectors. No
problems and very little additional mismatch loss.


Often simple dipoles are closer to 70 ohms than 50. Not enough to make any
differance in most ham instalations.

I saw on youtube where you could take the rg-6 and after you strip it back ,
wrap about 6 turns of duck tape around it just where the outer jacket stops.
You only need a strip about 1/2 or 1/4 of an inch wide. Then you can fold
the braid back and use crimp connectors designed for rg-8 size. That helps
solve the aluminum jacket problem with the PL259s.

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On Thu, 29 Aug 2013 17:13:39 -0400, "Ralph Mowery"
wrote:


"Jeff Liebermann" wrote in message
.. .

Drivel: All of my 50 ohm antennas on my roof are connected to their
respective radios with 75 ohm RG-6/u coax, F connectors, and various
adapters. Also some RG-6/u with BNC compression connectors. No
problems and very little additional mismatch loss.


Often simple dipoles are closer to 70 ohms than 50. Not enough to make any
differance in most ham instalations.

Actually, the mismatched RG-6/u can be better than the properly
matched RG-58c/u. For a given diameter, 75 ohm coax has less loss
than 50 ohm coax. 50 ohms has the advantage of being able to handle
more power, but at the expense of some additional loss.
http://www.microwaves101.com/encyclopedia/why50ohms.cfm

However, what was referring to was mismatch loss.
Voltage_reflection off of a 75 ohm input:
Vr = (50-75)/(50+75) = 0.2
Voltage transmission into 75 ohm input:
T = 1 - (0.2^2) = 0.96
Converting to decibels, the loss will be:
Mismatch_Loss = 20 Log 0.96 = -0.35 dB
mismatch loss. Note that the mismatch loss is independent of the
length of coax cable.

If you compare various common cables with RG-6/u, the benefits of the
better RG-6/u coax are obvious. 0.35dB of mismatch loss isn't going
to make much difference when there's 2 to 5 dB/100m difference in
attenuation.
http://vk1od.net/calc/tl/tllc.php
RG-8x = -12.6 dB/100m at 150 MHz.
LMR-240 = -9.89 dB/100m at 150 MHz.
RG-6/u = -7.78 dB/100m at 150 Mhz.

I saw on youtube where you could take the rg-6 and after you strip it back ,
wrap about 6 turns of duck tape around it just where the outer jacket stops.
You only need a strip about 1/2 or 1/4 of an inch wide. Then you can fold
the braid back and use crimp connectors designed for rg-8 size. That helps
solve the aluminum jacket problem with the PL259s.

Retch. There's no way to tightly crimp a few layers of tape.
Compressing the tape will cause it to cold flow at the glue junctions,
eventually causing the tape to slither out of the connector. Add a
little hot weather and the connector falls apart as the duct tape wrap
unravels. I know because I've done tricks like that eventually
failed. However, several layers of shrink tube might work because
shrink tube doesn't slide.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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"Jeff Liebermann" wrote in message
...
However, what was referring to was mismatch loss.
Voltage_reflection off of a 75 ohm input:
Vr = (50-75)/(50+75) = 0.2
Voltage transmission into 75 ohm input:
T = 1 - (0.2^2) = 0.96
Converting to decibels, the loss will be:
Mismatch_Loss = 20 Log 0.96 = -0.35 dB

mismatch loss. Note that the mismatch loss is independent of the
length of coax cable.

I agree with what you have been saying.

I may not be reading the part above the way you wrote it, but think I am.

I am thinking that that .35 db loss due to the mismatch is in adition to
the loss per unit length. That is if you have 100 feet of coax with a loss
of say 3 db when matched, you will have a loss of 3.35 per 100 feet, and if
you go to 200 feet you will have a loss of 6.70 db and not 6.35.

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On Fri, 30 Aug 2013 11:03:22 -0400, "Ralph Mowery"
wrote:


"Jeff Liebermann" wrote in message
.. .
However, what was referring to was mismatch loss.
Voltage_reflection off of a 75 ohm input:
Vr = (50-75)/(50+75) = 0.2
Voltage transmission into 75 ohm input:
T = 1 - (0.2^2) = 0.96
Converting to decibels, the loss will be:
Mismatch_Loss = 20 Log 0.96 = -0.35 dB

mismatch loss. Note that the mismatch loss is independent of the
length of coax cable.

I am thinking that that .35 db loss due to the mismatch is in adition to
the loss per unit length. That is if you have 100 feet of coax with a loss
of say 3 db when matched, you will have a loss of 3.35 per 100 feet, and if
you go to 200 feet you will have a loss of 6.70 db and not 6.35.

http://en.wikipedia.org/wiki/Mismatch_loss

I've always assumed that it was independent of length because the
mismatch loss can only occur at two points (source and load) and is
not a "bulk" phenomenon. Note that this is a 75 ohm system, not a 50
ohm system, where both the 50 ohm source and load are mismatched to
the 75 ohm transmission media. That makes things a bit easier to
visualize. My

Note that the 0.35 dB loss is not converted to heat or dissipated. The
antenna (or coax) does not get warmer because of mismatch loss. All
that happens is that some of the power gets reflected around and does
not get radiated out the antenna.

Sanity check:
http://vk1od.net/calc/tl/tllc.php
Plug in:
Belden 1530A (RG-6/u)
100 meters
150 MHz
Zload = 50
which results in:
Line Loss (matched) 7.924 dB
Line Loss 8.097 dB
VSWR(50)in 1.59
Mismatch loss = 8.097 - 7.924 = 0.1730 dB

Now, changing on the 100 meters to 500 meters should produce 5 times
the mismatch loss if your method is correct. It doesn't:
Line Loss (matched) 39.622 dB
Line Loss 39.799 dB
VSWR(50)in 1.50
Mismatch loss = 39.799 - 39.622 = 0.01770 dB
which is almost identical to the 100 meter caculation.

Note that this is for the load end of the coax only. A mismatch at
the source would produce an additional 0.1730 dB loss or:
2 * 0.1730 = 0.3460 dB
total mismatch loss, which corresponds nicely to my original 0.35 dB
loss calculation.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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On 8/31/2013 4:41 AM, Jeff wrote:


Note that the 0.35 dB loss is not converted to heat or dissipated. The
antenna (or coax) does not get warmer because of mismatch loss. All
that happens is that some of the power gets reflected around and does
not get radiated out the antenna.

So the reflected wave is somehow mysteriously exempt from the loss/m of
the coax then!!

Jeff

He buys his coax from "The Lossless Coax Store".

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On 8/31/2013 5:41 AM, Jeff wrote:


Note that the 0.35 dB loss is not converted to heat or dissipated. The
antenna (or coax) does not get warmer because of mismatch loss. All
that happens is that some of the power gets reflected around and does
not get radiated out the antenna.

So the reflected wave is somehow mysteriously exempt from the loss/m of
the coax then!!

Jeff

He is correct. That 0.35 db loss exists even if you have zero feet of
coax. It is a "point loss", unrelated to coax length.

The loss in the coax is separate.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.

==================

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On Friday, August 30, 2013 11:26:03 AM UTC-5, Jeff Liebermann wrote:
The antenna (or coax) does not get warmer because of mismatch loss.

Sounds like a confusing play on words to me.:)

IF (the greater the mismatch loss) THEN (the higher the SWR) is TRUE
AND
IF (the higher the SWR) THEN (the greater the heat loss in the transmission line) is TRUE
THEN (the greater the mismatch loss, the greater the heat loss in the transmission line). LOGIC 101
--
73, Cecil, w5dxp.com

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On Sat, 31 Aug 2013 10:41:24 +0100, Jeff wrote:

Note that the 0.35 dB loss is not converted to heat or dissipated. The
antenna (or coax) does not get warmer because of mismatch loss. All
that happens is that some of the power gets reflected around and does
not get radiated out the antenna.

So the reflected wave is somehow mysteriously exempt from the loss/m of
the coax then!!

Jeff

Coax attenuation is part of a separate loss calculation that does not
involve matching. Mismatch loss is in addition to the coax losses.
Actually, that's not quite right. Mismatch loss is not a real loss,
where RF is converted to heat. It's simply the amount of additional
power that could have been delivered to the load had the system been
properly matched.

Let's try the boundary conditions and see what breaks. The coax
attenuation (in both directions) changes the measured VSWR and
therefore the mismatch loss. For example, if you had a ridiculously
long length of coax, with plenty of attenuation, the reflected RF at
the source is sufficiently attenuated so that the VSWR looks very
close to 1:1. Therefore, there's no mismatch, and therefore no
mismatch loss.[1]

At the other extreme, very short lengths of coax cable, have almost no
effect on the end point VSWR's. For this example, we have a 50 ohm
source, 75 ohm coax, and 50 ohm load. Reduce the 75 ohm coax cable to
near zero length, and there's no coax attenuation. Since the source
and load are matched, there's no mismatch, and therefore no mismatch
loss.

So, by your interpretation, there's no mismatch loss at the boundary
conditions (short coax and very long coax), while there's allegedly
mismatch loss for coax cable lengths in between? I don't think so.
More likely that the mismatch loss is unchanged, no matter how long or
short the cable.


[1] In the distant past, I wired 10base2 ethernet (cheapernet) at
several customers using existing 75 ohm CATV coax cables. 50 ohm
transceivers, 75 ohm coax, and 50 ohm resistive terminators. No
problems (other than crappy crimps). I also played with two 1000ft
rolls of RG-6/u and RG-58a/u. The 75 ohm RG-6/u was better because of
much lower losses (6dB versus 14dB at 10 Mhz).



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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On Sat, 31 Aug 2013 15:44:50 +0100, Jeff wrote:

On 31/08/2013 15:15, Jerry Stuckle wrote:
On 8/31/2013 5:41 AM, Jeff wrote:


Note that the 0.35 dB loss is not converted to heat or dissipated. The
antenna (or coax) does not get warmer because of mismatch loss. All
that happens is that some of the power gets reflected around and does
not get radiated out the antenna.

So the reflected wave is somehow mysteriously exempt from the loss/m of
the coax then!!

Jeff

He is correct. That 0.35 db loss exists even if you have zero feet of
coax. It is a "point loss", unrelated to coax length.

The loss in the coax is separate.

The loss may be 'separate' but that coax does *get warmer* as the
reflected power also experiences loss in the cable, so he is not correct.
Jeff

Ok, let's try a different approach. Assumptions:
1. Only resistive losses generate heat. Reactive loads and
transmission lines do not generate any heat.
2. Below about 1GHz, the dominant loss mechanism in coax cable
is I^2*R heating losses in the copper conductors.
3. The coax is assumed to be non-radiating.
4. Coax looks resistive because the distributed capacitance
and inductive reactances cancel, leaving only the I^2*R losses.

Therefore, if I replace a length of 50 ohm coax, with a physically
similar length of 75 ohm coax, the I^2*R losses do not change. What
does change are the standing waves along the coax, which will cause
mismatch losses. However, the basic coax loss, as controlled by the
I^2*R losses, remains unchanged. Therefore, since the mismatch losses
are all inspired by changes in reactance, there is no additional
heating losses produced by the mismatch losses, since reactive loads
and transmission lines do not generate any heat.

Anyway, please note my use of the forms at:
http://vk1od.net/calc/tl/tllc.php
to calculate the mismatch loss for various cable lengths. I
previously demonstrated that the mismatch loss is constant, no matter
how long or short the transmission line. I'm fairly sure the
calculations are correct. I'm not so certain of my explanation.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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On Saturday, August 31, 2013 11:15:50 AM UTC-5, Jeff Liebermann wrote:
Mismatch loss is not a real loss ... It's simply the amount of
additional power that could have been delivered to the load had
the system been properly matched.

Not quite correct yet. Consider the following system:

100w source---1/2WL 291.5 ohm twinlead---50 ohm load

The mismatch loss at the load is 3dB but the source is already delivering its maximum available power so there is ZERO additional power available.

(Forward Power) minus (Maximum Source Power) is NOT available for delivery to the load no matter what the mismatch loss happens to be.
--
73, Cecil, w5dxp.com

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On Saturday, August 31, 2013 11:37:20 AM UTC-5, Jeff Liebermann wrote:
Therefore, if I replace a length of 50 ohm coax, with a physically
similar length of 75 ohm coax, the I^2*R losses do not change.

What you may be missing is that the RMS value of the current is higher when reflections are present than when they are not present. Therefore, the I^2*R losses in the transmission line are higher when reflections are present. Part of the reflected energy from the load (used to calculate mismatch loss) is dissipated as heat in the I^2*R of the copper transmission line as illustrated by the following example.

Consider 200 ft. of RG-58 used on 440 MHz driving a 291.5 ohm load. The mismatch loss at the load is 3dB but the loss in the coax is 29.4 dB and the impedance looking into the coax at the source is 50.12-j0.19 ohms, almost a perfect match. Would you still argue that none of the power involved in the mismatch loss is dissipated in the coax?
--
73, Cecil, w5dxp.com

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"W5DXP" wrote in message
...

On Saturday, August 31, 2013 11:37:20 AM UTC-5, Jeff Liebermann wrote:
Therefore, if I replace a length of 50 ohm coax, with a physically
similar length of 75 ohm coax, the I^2*R losses do not change.

# What you may be missing is that the RMS value of the current is higher
when reflections are present than when
# they are not present. Therefore, the I^2*R losses in the transmission line
are higher when reflections are
#present. Part of the reflected energy from the load (used to calculate
mismatch loss) is dissipated
# as heat in the I^2*R of the copper transmission line as illustrated by
the following example.

# Consider 200 ft. of RG-58 used on 440 MHz driving a 291.5 ohm load. The
mismatch loss at the load
# is 3dB but the loss in the coax is 29.4 dB and the impedance looking into
the coax at the
# source is 50.12-j0.19 ohms, almost a perfect match. Would you still argue
that none of the power
# involved in the mismatch loss is dissipated in the coax?
--
# 73, Cecil, w5dxp.com

This chart has been around a long time and indicates what is going on.
See figure 1 at:

http://www.arrl.org/files/file/Techn...f/q1106037.pdf

As a practical example, my elevated vertical (on a metal patio cover) is fed
with about 20 feet of RG-8. Matching is via a tuner right at the rig, and
the vertical element connects to the coax with no other matching.

RG-8 has a loss of about 0.55 db per 100 feet.

Assume that my 20 foot feedline has a full 0.55 dB of loss when matched. On
bands where the VSWR is 20:1,
according to the chart, the system will have additional loss of less than 3
dB.

And it works fine.

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On Sunday, September 1, 2013 12:40:51 PM UTC-5, Wayne wrote:
... the system will have additional loss of less than 3 dB.
And it works fine.

So the question is: Is any part of the reflected power in the
mismatch loss calculation included in that 3 dB of additional
loss? The answer is 'yes' and whether it works fine or not is
irrelevant to the argument.
--
73, Cecil, w5dxp.com

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On 8/31/2013 10:40 AM, W5DXP wrote:
On Friday, August 30, 2013 11:26:03 AM UTC-5, Jeff Liebermann wrote:
The antenna (or coax) does not get warmer because of mismatch loss.

Sounds like a confusing play on words to me.:)

IF (the greater the mismatch loss) THEN (the higher the SWR) is TRUE
AND
IF (the higher the SWR) THEN (the greater the heat loss in the transmission line) is TRUE
THEN (the greater the mismatch loss, the greater the heat loss in the transmission line). LOGIC 101
--
73, Cecil, w5dxp.com


Actually, Jeff is correct in his original statement, "Actually, the
mismatched RG-6/u can be better than the properly matched RG-58c/u."

It can be shown that the losses are higher with properly matched
RG-58c/u than with the mismatched RG-6/u. (Real-word circumstances, not
loss-less line approximation.)

John KD5YI

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"W5DXP" wrote in message
...

On Sunday, September 1, 2013 12:40:51 PM UTC-5, Wayne wrote:
... the system will have additional loss of less than 3 dB.
And it works fine.

So the question is: Is any part of the reflected power in the
mismatch loss calculation included in that 3 dB of additional
loss? The answer is 'yes' and whether it works fine or not is
irrelevant to the argument.
--
73, Cecil, w5dxp.com

Indeed. If there is loss going one direction on a line, reflected power
going the other way suffers loss also.

The part about "works fine" was thrown in, not for you, but for those who
might be horrified by a high vswr.

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On Sunday, September 1, 2013 6:09:09 PM UTC-5, Wayne wrote:
The part about "works fine" was thrown in, not for you, but for those who
might be horrified by a high vswr.

Sorry, I misunderstood what you were trying to say.
--
73, Cecil, w5dxp.com

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"W5DXP" wrote in message
...

On Sunday, September 1, 2013 6:09:09 PM UTC-5, Wayne wrote:
The part about "works fine" was thrown in, not for you, but for those who
might be horrified by a high vswr.

Sorry, I misunderstood what you were trying to say.

My fault for delaying my response. I should have looked back for the
particular "read" post, instead of replying to the one "unread" at the
moment.

I was trying to add into the thread the figure 1 referenced. I look at it
as showing that at high VSWRs, reflected power takes more trips back and
forth through the line loss until the reflection becomes insignificant.