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

"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.

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.

"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"

"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.

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

"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.

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

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

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