Stacking Winegard HD-6065P antennas
 

On Thu, 9 Jan 2014 21:08:11 -0800, "Sal" salmonella@food
poisoning.org wrote:

Another experiment I ran (back around 1975) was to take 100 feet of cable
and measure the loss, then repeat the measurement using a different 100 feet
made from ten different pieces. Yup, the loss was about 3 dB more,
indicative of an average 0.3 dB loss per joint, neatly within the range you
specified.

0.3dB per connector at what frequency?

This is more fun:
http://802.11junk.com/jeffl/antennas/connector-loss/index.html
Just take every connector that you can find, put them in series, and
measure the loss. In this case, it was done at 2.4Ghz and 450MHz. End
to end loss at 2.4GHz was 2dB for about 25 adapters or about 0.08dB
per adapter. At 250MHz, the loss was about 0.2dB or 0.008dB per
adapter.

I've done similar demonstrations using two wattmeters at the local
radio club meeting. The results are typically that the adapter string
has the same loss as an equivalent length of small coax cable. I had
a surplus of BNC T connectors, so a strung about 50 of them in series
and obtained similar results.

Bottom line: Connectors and adapters aren't as evil as the data
sheets and literature suggest.


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

Stacking Winegard HD-6065P antennas
 

On 1/10/2014 11:03 AM, Ralph Mowery wrote:
"Sal" salmonella@food poisoning.org wrote in message
...

Discussion of audio amplifier power in home systems always prompts me to
relate this: I worked for a guy who was formerly a projectionist at Radio
City Music Hall in New York. He told me the sound system used amplifiers
rated at 70 watts per channel. That's a 6,000-seat theater.

He worked there a long time ago, so this not a claim of what they use
today. Use for perspective only, please.

I wonder if that was 'real watts' instead of inflated watts. I have seen
some wall wart computer speakers rated at 50 watts or so. Open them up and
inside the speaker may have 3 watts on the lable.

Same as with the listed gain of antennas for hams and especially the CB.
One antenna of modern times had a gain listed of several times more than it
should. Claimed to be the gain from one of the computer programs. It may
have been,but they were adding in a lot of ground gain and certain take off
angles.

Not sure where they were getting the gain numbers from,but he old CC 11
element 2 meter beams had a number that was way too high if you compaired it
on the air with another antenna.




If it was a long time ago, I suspect it was "real watts". Manufacturers
didn't really start inflating the wattage until the 70's or so.

Nowadays, a "100W" amplifier is probably more like 20 "real" watts.

--
==================
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Jerry, AI0K

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

Stacking Winegard HD-6065P antennas
 

In message , Jeff Liebermann
writes
On Thu, 9 Jan 2014 21:08:11 -0800, "Sal" salmonella@food
poisoning.org wrote:

Another experiment I ran (back around 1975) was to take 100 feet of cable
and measure the loss, then repeat the measurement using a different 100 feet
made from ten different pieces. Yup, the loss was about 3 dB more,
indicative of an average 0.3 dB loss per joint, neatly within the range you
specified.

0.3dB per connector at what frequency?

This is more fun:
http://802.11junk.com/jeffl/antennas/connector-loss/index.html
Just take every connector that you can find, put them in series, and
measure the loss. In this case, it was done at 2.4Ghz and 450MHz. End
to end loss at 2.4GHz was 2dB for about 25 adapters or about 0.08dB
per adapter. At 250MHz, the loss was about 0.2dB or 0.008dB per
adapter.

I've done similar demonstrations using two wattmeters at the local
radio club meeting. The results are typically that the adapter string
has the same loss as an equivalent length of small coax cable. I had
a surplus of BNC T connectors, so a strung about 50 of them in series
and obtained similar results.

Bottom line: Connectors and adapters aren't as evil as the data
sheets and literature suggest.

I've always assumed that the loss measured through connectors and
adapters was mainly
(a) because they have unavoidable length (ie not a lot), and
(b) because the impedance match through them is less than perfect (ie
not a lot).
The ohmic contact resistance may also be a tiny tad higher than the same
length of coax (even less).
--
Ian

Stacking Winegard HD-6065P antennas
 

"Ralph Mowery" wrote in message
m...

"Sal" salmonella@food poisoning.org wrote in message
...

Discussion of audio amplifier power in home systems always prompts me to
relate this: I worked for a guy who was formerly a projectionist at
Radio City Music Hall in New York. He told me the sound system used
amplifiers rated at 70 watts per channel. That's a 6,000-seat theater.

He worked there a long time ago, so this not a claim of what they use
today. Use for perspective only, please.

I wonder if that was 'real watts' instead of inflated watts. I have seen
some wall wart computer speakers rated at 50 watts or so. Open them up
and inside the speaker may have 3 watts on the lable.

Same as with the listed gain of antennas for hams and especially the CB.
One antenna of modern times had a gain listed of several times more than
it should. Claimed to be the gain from one of the computer programs. It
may have been,but they were adding in a lot of ground gain and certain
take off angles.

Not sure where they were getting the gain numbers from,but he old CC 11
element 2 meter beams had a number that was way too high if you compaired
it on the air with another antenna.

Hard to know, Ralph. Some years ago, I was the repairman for my son's high
school music group, a show choir that traveled with a serious suite of
electronics. One evening, I changed a bad tweeter in a big roll-around
speaker system and tested it before I put it in my van. I clipped leads on
the speaker terminals and plugged into the headphone jack on a small
boombox -- powered by four D-cells. When I began to crank it up on the
patio, my lovely wife came roaring out and demanded that I turn it down.
"Do you know what time it is?"

Well, yes, I did know, but that wasn't exactly her point. Clearly, four
D-cells provide more than enough sound power to upset a whole neighborhood
and she felt the need to heighten my concern. ;-)

"Sal"

Stacking Winegard HD-6065P antennas
 

On 1/10/2014 7:01 PM, Ian Jackson wrote:
In message , Jeff Liebermann
writes
On Thu, 9 Jan 2014 21:08:11 -0800, "Sal" salmonella@food
poisoning.org wrote:

Another experiment I ran (back around 1975) was to take 100 feet of
cable
and measure the loss, then repeat the measurement using a different
100 feet
made from ten different pieces. Yup, the loss was about 3 dB more,
indicative of an average 0.3 dB loss per joint, neatly within the
range you
specified.

0.3dB per connector at what frequency?

This is more fun:
http://802.11junk.com/jeffl/antennas/connector-loss/index.html
Just take every connector that you can find, put them in series, and
measure the loss. In this case, it was done at 2.4Ghz and 450MHz. End
to end loss at 2.4GHz was 2dB for about 25 adapters or about 0.08dB
per adapter. At 250MHz, the loss was about 0.2dB or 0.008dB per
adapter.

I've done similar demonstrations using two wattmeters at the local
radio club meeting. The results are typically that the adapter string
has the same loss as an equivalent length of small coax cable. I had
a surplus of BNC T connectors, so a strung about 50 of them in series
and obtained similar results.

Bottom line: Connectors and adapters aren't as evil as the data
sheets and literature suggest.

I've always assumed that the loss measured through connectors and
adapters was mainly
(a) because they have unavoidable length (ie not a lot), and
(b) because the impedance match through them is less than perfect (ie
not a lot).
The ohmic contact resistance may also be a tiny tad higher than the same
length of coax (even less).

The main loss in a connector is due to the impedance bump at the
connector. This can be easily seen on a TDR (Time Domain Reflectometry)
display.

Some connectors are better than others; for instance, the older F
connectors which are crimped down with a ring are the worst. Next is
the connector where the crimp is a hex crimp - it doesn't give a
consistent impedance around the connector.

The best (and the ones we use) compress the entire base of the connector
evenly, creating a smooth crimp. The end of the coax is evenly covered
by the connector.

The other problem is the technician installing the connectors. I've
seen great ones, and not-so-great ones. There are a lot of chances for
going wrong - for instance, it's easy to screw up the braid when trying
to insert a crimp-on connector under the outer jacket and shield. And
soldering connectors (i.e. PL-259 and N) is almost sure to give you a
huge bump (and loss) because it's almost impossible to solder the shield
without melting the inner insulator to some point. It may not short
out, but that doesn't mean you don't have loss there.

--
==================
Remove the "x" from my email address
Jerry, AI0K

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

Stacking Winegard HD-6065P antennas
 

On Sat, 11 Jan 2014 00:01:57 +0000, Ian Jackson
wrote:

In message , Jeff Liebermann
writes
On Thu, 9 Jan 2014 21:08:11 -0800, "Sal" salmonella@food
poisoning.org wrote:

Another experiment I ran (back around 1975) was to take 100 feet of cable
and measure the loss, then repeat the measurement using a different 100 feet
made from ten different pieces. Yup, the loss was about 3 dB more,
indicative of an average 0.3 dB loss per joint, neatly within the range you
specified.

0.3dB per connector at what frequency?

This is more fun:
http://802.11junk.com/jeffl/antennas/connector-loss/index.html
Just take every connector that you can find, put them in series, and
measure the loss. In this case, it was done at 2.4Ghz and 450MHz. End
to end loss at 2.4GHz was 2dB for about 25 adapters or about 0.08dB
per adapter. At 250MHz, the loss was about 0.2dB or 0.008dB per

Oops. That should be 450 Mhz, not 250 MHz.

adapter.

I've done similar demonstrations using two wattmeters at the local
radio club meeting. The results are typically that the adapter string
has the same loss as an equivalent length of small coax cable. I had
a surplus of BNC T connectors, so a strung about 50 of them in series
and obtained similar results.

Bottom line: Connectors and adapters aren't as evil as the data
sheets and literature suggest.

I've always assumed that the loss measured through connectors and
adapters was mainly
(a) because they have unavoidable length (ie not a lot), and
(b) because the impedance match through them is less than perfect (ie
not a lot).

As I misunderstand it, below about 1GHz, most of the loss is ohmic,
which are the surface and contact resistance of the connections and
conductors. Above 1GHz, the dielectric losses begin to become
significant. Extra points of dissimilar metals and bad construction.
Except for the PL-259/SO-239 and phono connectors, most of the
connectors are fairly close to 50 ohms.

The ohmic contact resistance may also be a tiny tad higher than the same
length of coax (even less).

Yep. It's more than a tiny tad higher. For example, at 2.4 GHz,
LMR240 has an attenuation of 12.6 dB/100ft. Each coax adapter is
maybe an inch long, resulting in:
12.6 dB/100ft = 0.126 dB/ft = 0.01 dB/inch
which is 8 times less than the 0.08dB/adapter that the measurements
show. However, there's plenty of room for measurement error here. I
suspect that if quality connectors were used, such as SMA, the numbers
could come out closer to a similar wire gauge coax cable.


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

Stacking Winegard HD-6065P antennas
 

"Jeff Liebermann" wrote in message
...
On Thu, 9 Jan 2014 21:08:11 -0800, "Sal" salmonella@food
poisoning.org wrote:

Another experiment I ran (back around 1975) was to take 100 feet of cable
and measure the loss, then repeat the measurement using a different 100
feet
made from ten different pieces. Yup, the loss was about 3 dB more,
indicative of an average 0.3 dB loss per joint, neatly within the range
you
specified.

0.3dB per connector at what frequency?

This is more fun:
http://802.11junk.com/jeffl/antennas/connector-loss/index.html
Just take every connector that you can find, put them in series, and
measure the loss. In this case, it was done at 2.4Ghz and 450MHz. End
to end loss at 2.4GHz was 2dB for about 25 adapters or about 0.08dB
per adapter. At 250MHz, the loss was about 0.2dB or 0.008dB per
adapter.

I've done similar demonstrations using two wattmeters at the local
radio club meeting. The results are typically that the adapter string
has the same loss as an equivalent length of small coax cable. I had
a surplus of BNC T connectors, so a strung about 50 of them in series
and obtained similar results.

Bottom line: Connectors and adapters aren't as evil as the data
sheets and literature suggest.

I agree.

To answer your question, my test generator output was Channel 3, so my
measurements were done about 61 MHz. I used all F-connectors, too, not
exactly a precision connector.

The reason I did the experiment [on USS Oriskany (CV-34), by the way] was
because my prior duties as an Electronic Warfare Tech exposed me to a
persistent rumor: Connectors cause a 3dB loss. I knew that it was nonsense
but I had never taken the time to conclusively disprove it before I moved to
the TV shop.

Related: I'm in a local group that's experimenting with mesh networking
(http://www.broadband-hamnet.org/). My first antenna connection required a
stack of four adapters, so last week I bought eight different adapters. I
should need only one. My big concern is not signal loss but the possibility
of snapping something plastic with a stupid long stack of connectors on the
back of a router.

"Sal"

Stacking Winegard HD-6065P antennas
 

On Fri, 10 Jan 2014 19:36:59 -0500, Jerry Stuckle
wrote:

The main loss in a connector is due to the impedance bump at the
connector. This can be easily seen on a TDR (Time Domain Reflectometry)
display.

Rubbish. Let's pretend that I mix in a 75 ohm coax connector into a
50 ohm system. Depending on the location of this "impedance bump",
the VSWR is no more than 1.5:1 which is generally considered marginal.
That's 0.18dB of mismatch loss.
http://www.microwaves101.com/encyclopedia/calvswr.cfm
If you're doing satellite or microwave DX work, then 0.18dB might be
important. However, for most other applications, it's a trivial
amount.

You might be amused to know that most of my rooftop antennas are fed
with 75 ohm coax and that my favored antenna designs are also 75 ohm.
There are various reasons, but the main one is that coax cable losses
are less at 75 ohms, than at 50 ohms. 50 ohms can handle more power,
but 75 ohms has less loss.
http://www.belden.com/blog/broadcastav/50-Ohms-The-Forgotten-Impedance.cfm
The only problems I have with 75 ohms is finding the proper connectors
and dealing with the pads needed to make my 50 ohm test equipment look
like 75 ohms. (Actually the real reason is that the 75 ohm stuff is
mostly CATV surplus, which tends to be really cheap).

Mo
http://www.qsl.net/n9zia/wireless/75_ohm_hardline.html

Some connectors are better than others; for instance, the older F
connectors which are crimped down with a ring are the worst. Next is
the connector where the crimp is a hex crimp - it doesn't give a
consistent impedance around the connector.

I rip those out wherever I find them, even if they're on the ends of
commercially crimped cables (usually RG-59/u which is another
nightmare). However, the loss mechanism with the old CATV coax and
associated crappy crimp connectors was radiation, not mismatch loss.
The ground connections would fall apart, turning the coax shield into
an impressive antenna.

The best (and the ones we use) compress the entire base of the connector
evenly, creating a smooth crimp. The end of the coax is evenly covered
by the connector.

I've had problems with some of those push-on connectors. I also don't
want to stock a zillion different connector variations from different
vendors. So, I've standardized on the "red" univeral T&B SNS1P6U
RG-6/u connectors:
www.ebay.com/sch/i.html?_nkw=SNS1P6U

The other problem is the technician installing the connectors. I've
seen great ones, and not-so-great ones. There are a lot of chances for
going wrong - for instance, it's easy to screw up the braid when trying
to insert a crimp-on connector under the outer jacket and shield. And
soldering connectors (i.e. PL-259 and N) is almost sure to give you a
huge bump (and loss) because it's almost impossible to solder the shield
without melting the inner insulator to some point. It may not short
out, but that doesn't mean you don't have loss there.

Actually, it's not the crimp job that kills the connection. It's the
stripping of the coax that causes the most problems. I use various
rotary contrivances that have razor blades to make the cuts at the
correct spacing. Those work well initially, but after about 50
connectors, the blades become dull and useless. Of course, nobody has
spare blades or knows how to adjust them. They either continue to use
a dull razor or steal my new stripper.

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

Stacking Winegard HD-6065P antennas
 

"Jeff Liebermann" wrote in message
...
On Fri, 10 Jan 2014 19:36:59 -0500, Jerry Stuckle
Actually, it's not the crimp job that kills the connection. It's the
stripping of the coax that causes the most problems. I use various
rotary contrivances that have razor blades to make the cuts at the
correct spacing. Those work well initially, but after about 50
connectors, the blades become dull and useless. Of course, nobody has
spare blades or knows how to adjust them. They either continue to use
a dull razor or steal my new stripper.


I don't know the quality of the cutters you use, but I have bought several
from China off ebay for about $ 2 each including shipping. For the very few
connectors I do, they work. At that price, you could order a lot of them
and not worry about the replacement blades. Just like the disposiable
razors. They seem identical to the ones that sell in stores for $ 10 to $
15 .



---
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Stacking Winegard HD-6065P antennas
 

On 1/10/2014 9:06 PM, Jeff Liebermann wrote:
On Fri, 10 Jan 2014 19:36:59 -0500, Jerry Stuckle
wrote:

The main loss in a connector is due to the impedance bump at the
connector. This can be easily seen on a TDR (Time Domain Reflectometry)
display.

Rubbish. Let's pretend that I mix in a 75 ohm coax connector into a
50 ohm system. Depending on the location of this "impedance bump",
the VSWR is no more than 1.5:1 which is generally considered marginal.
That's 0.18dB of mismatch loss.
http://www.microwaves101.com/encyclopedia/calvswr.cfm
If you're doing satellite or microwave DX work, then 0.18dB might be
important. However, for most other applications, it's a trivial
amount.


That's theoretical. Reality is much different. Have you ever worked
with a TDR? It's one of the tools we use regularly (and an expensive
one, also).

You might be amused to know that most of my rooftop antennas are fed
with 75 ohm coax and that my favored antenna designs are also 75 ohm.
There are various reasons, but the main one is that coax cable losses
are less at 75 ohms, than at 50 ohms. 50 ohms can handle more power,
but 75 ohms has less loss.
http://www.belden.com/blog/broadcastav/50-Ohms-The-Forgotten-Impedance.cfm
The only problems I have with 75 ohms is finding the proper connectors
and dealing with the pads needed to make my 50 ohm test equipment look
like 75 ohms. (Actually the real reason is that the 75 ohm stuff is
mostly CATV surplus, which tends to be really cheap).


So? Dipoles aren't 50 ohm antennas. They're typically closer to 75 ohm.

As for handling more power - rubbish. The current in 75 ohm coax is
lower than that in 50 ohm coax, for the same power rating.

Proper connectors are no problem when you can buy from commercial
distributors. But we don't typically sell them individually.

Mo
http://www.qsl.net/n9zia/wireless/75_ohm_hardline.html

Some connectors are better than others; for instance, the older F
connectors which are crimped down with a ring are the worst. Next is
the connector where the crimp is a hex crimp - it doesn't give a
consistent impedance around the connector.

I rip those out wherever I find them, even if they're on the ends of
commercially crimped cables (usually RG-59/u which is another
nightmare). However, the loss mechanism with the old CATV coax and
associated crappy crimp connectors was radiation, not mismatch loss.
The ground connections would fall apart, turning the coax shield into
an impressive antenna.


We use RG-59 where appropriate, like from an outlet to the set top box.
But our in-wall coax runs are all RG-6 quad-shielded.

But we're also doing less and less coax and more and more Category cable
nowadays.

The best (and the ones we use) compress the entire base of the connector
evenly, creating a smooth crimp. The end of the coax is evenly covered
by the connector.

I've had problems with some of those push-on connectors. I also don't
want to stock a zillion different connector variations from different
vendors. So, I've standardized on the "red" univeral T&B SNS1P6U
RG-6/u connectors:
www.ebay.com/sch/i.html?_nkw=SNS1P6U


They're OK for the hobbyist, but I don't know of any professionals who
use them. In fact, checking our main wholesalers, they aren't even
available through them (but other Beldon products are).

The other problem is the technician installing the connectors. I've
seen great ones, and not-so-great ones. There are a lot of chances for
going wrong - for instance, it's easy to screw up the braid when trying
to insert a crimp-on connector under the outer jacket and shield. And
soldering connectors (i.e. PL-259 and N) is almost sure to give you a
huge bump (and loss) because it's almost impossible to solder the shield
without melting the inner insulator to some point. It may not short
out, but that doesn't mean you don't have loss there.

Actually, it's not the crimp job that kills the connection. It's the
stripping of the coax that causes the most problems. I use various
rotary contrivances that have razor blades to make the cuts at the
correct spacing. Those work well initially, but after about 50
connectors, the blades become dull and useless. Of course, nobody has
spare blades or knows how to adjust them. They either continue to use
a dull razor or steal my new stripper.

Oops... dinner... gone.


Stripping is almost never a problem, unless you're a real klutz. Even
if you nick the braid a bit it isn't very critical.

We use the same type of rotary stripper - but just because it's much
faster. One of our techs can install an F connector in a minute or less
with one of them.

I never counted how many connections we get out of a stripper, but it's
got to be in the thousands. We replace some screwdrivers more often
than the strippers :)

--
==================
Remove the "x" from my email address
Jerry, AI0K

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