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Old March 27th 12, 12:12 AM posted to rec.radio.amateur.moderated
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In writes:

On Mon, 26 Mar 2012 01:45:59 EDT, (Alan)
wrote:


In article Channel Jumper writes:

DrTeeth;788676 Wrote:


But I've
not considered BNC, at least for HF work.

Though it may be an impure thought, but don't HF commercial rigs all
have SO 259s? Are adapters available?
--

Cheers



Yes - but the adapters are quite lossy.



Actually, I have not found significant loss in any of these adapters
I have used. If they had much loss, they would get warm (or hot) when
transmitting, and none I have used do.

Alan


I agree with Alan. The adapters are not lossy.
I use them frequently to connect the outputs of my handhelds (BNC,
SMA) to mag-mount antennas (UHF connector). They work fine. Good
output signal and good reception. No heat generated.


Dick Grady, AC7EL


To respond to me privately, email to:
My Call at My Call dot org



Reading around on the subject, it seems that there are different kinds
of losses in connectors and transmission lines, and not all of them will
cause heating at the junction or interval where the loss occurs. Some
knowledgeable amateurs have noted that we sometimes confuse transmission
losses and insertion losses. Transmission loss, either Ohmic resistance
or dielectric, will be dissipative, and directly heat the transmission
line where the losses occur. Insertion loss, such as from impedance
mismatch, results in power being reflected. Even impedance-matched
connector conversions (50 Ohm to 50 Ohm) may still result in some
impedance mismatch due to practical limits on their physical design,
including their actual non-constant impedance that can vary with
frequency, and the quality of their connections, particularly after
long-term exposure to the elements. This is where the imaginary part of
complex impedance, also known as reactance, comes in.

Now, that reflected power has to go somewhere, and will either be
reflected back to the airwaves on reception, or back into the
transmitter on transmission. But just measuring heat generated at the
connector may not account for all losses, because the actual
dissipation may occur elsewhere. You may not have noticed much or any
signal loss due to operating well within usable link budgets, nor
noticed much extra heat generation in the body of the HT, but insertion
loss from connectors can contribute a small, measurable amount of
reduction in signal strength. Probably not something to worry about for
an HT talking to a repeater. Perhaps something to worry about for
Earth-Moon-Earth at UHF, or mountain-topping at microwave frequencies,
or other weak-signal work much above HF.


Some links I found on the subject:


1. Pretty Lousy? (PL) 259 Connectors

"The underlying assumption with the above statement is connector
loss has everything to do with resistive 'heating' losses, has
nothing to do with reflective losses, and all loss will reveal
itself as heat energy."

http://www.hamradio.me/connectors/pr...-the-test.html


2. The UHF type connector under network analysis

"Manufactures of UHF plugs and receptors all state that this type
connector are of non-constant impedance and are suitable for use
up to 200 or 300 MHz, depending on production quality. They also
state that the UHF connector can be used up to 500 MHz with a
cautionary note of reduced performance."

http://www.qsl.net/vk3jeg/pl259tst.html


3. Insertion Loss vs. Transmission Loss

"Insertion Loss and Transmission Loss are often confused by hams."

http://vk1od.net/transmissionline/concept/iltl.htm


4. N-type vs. SO-239 NO FIGHTING PLEASE! :-)

"There's no question that Type N connectors will outperform UHF
connectors at VHF and UHF. But unless you're prepared to open up
the radio and replace the SO-239 with a Type N, don't sweat the
single connection. Just use a UHF-Type N adapter on the back of
the rig and go with Type N connectors everywhere else."

http://www.eham.net/ehamforum/smf/in...c=68629.0;wap2


5. Insertion loss for RF connector adaptors

"1/4 to 1/2 db per connector is the loss I've always heard."

http://www.amsat.org/amsat/archive/a.../msg00214.html


- --
73, Paul W. Schleck, K3FU

http://www.novia.net/~pschleck/
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Old March 27th 12, 05:35 PM posted to rec.radio.amateur.moderated
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In article Paul W. Schleck " writes:


Reading around on the subject, it seems that there are different kinds
of losses in connectors and transmission lines, and not all of them will
cause heating at the junction or interval where the loss occurs. Some
knowledgeable amateurs have noted that we sometimes confuse transmission
losses and insertion losses. Transmission loss, either Ohmic resistance
or dielectric, will be dissipative, and directly heat the transmission
line where the losses occur. Insertion loss, such as from impedance
mismatch, results in power being reflected. Even impedance-matched
connector conversions (50 Ohm to 50 Ohm) may still result in some
impedance mismatch due to practical limits on their physical design,
including their actual non-constant impedance that can vary with
frequency, and the quality of their connections, particularly after
long-term exposure to the elements. This is where the imaginary part of
complex impedance, also known as reactance, comes in.



The question being addressed was the losses of an adapter when connecting
a cable to an HF rig built with a UHF connector.

The adapters are very short sections of transmission line. The Smith
chart works here, too. Even with a substantial impedance mismatch through
the connector, the segment is very short with respect to a wavelength, and
will not provide a significant input impedance mismatch, if the output side
of the connector is connected to a 50 ohm load.



5. Insertion loss for RF connector adaptors

"1/4 to 1/2 db per connector is the loss I've always heard."

http://www.amsat.org/amsat/archive/a.../msg00214.html



I suggest measurement is a better way to determine the truth. These
claims are easy to test --- measurements I made some years ago didn't
support such claims. In fact, if you are getting such substantial losses,
it is probably time to investigate other possible causes.

Alan

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Old March 28th 12, 03:26 AM posted to rec.radio.amateur.moderated
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In (Alan) writes:

In article Paul W. Schleck " writes:



Reading around on the subject, it seems that there are different kinds
of losses in connectors and transmission lines, and not all of them will
cause heating at the junction or interval where the loss occurs. Some
knowledgeable amateurs have noted that we sometimes confuse transmission
losses and insertion losses. Transmission loss, either Ohmic resistance
or dielectric, will be dissipative, and directly heat the transmission
line where the losses occur. Insertion loss, such as from impedance
mismatch, results in power being reflected. Even impedance-matched
connector conversions (50 Ohm to 50 Ohm) may still result in some
impedance mismatch due to practical limits on their physical design,
including their actual non-constant impedance that can vary with
frequency, and the quality of their connections, particularly after
long-term exposure to the elements. This is where the imaginary part of
complex impedance, also known as reactance, comes in.



The question being addressed was the losses of an adapter when connecting
a cable to an HF rig built with a UHF connector.


The adapters are very short sections of transmission line. The Smith
chart works here, too. Even with a substantial impedance mismatch through
the connector, the segment is very short with respect to a wavelength, and
will not provide a significant input impedance mismatch, if the output side
of the connector is connected to a 50 ohm load.




5. Insertion loss for RF connector adaptors

"1/4 to 1/2 db per connector is the loss I've always heard."

http://www.amsat.org/amsat/archive/a.../msg00214.html


I suggest measurement is a better way to determine the truth. These
claims are easy to test --- measurements I made some years ago didn't
support such claims. In fact, if you are getting such substantial losses,
it is probably time to investigate other possible causes.


Alan


Thanks, Alan, for your followup.

I certainly don't mind being corrected, or clarified, on the subject. I
just knew enough (to be dangerous?) on the topic to know that losses can
be both direct Ohmic or dielectric dissipation losses, or reflection
losses from impedance mismatches. So a cool connector or transmission
line is necessary, but not sufficient, evidence that little or no power
is being lost. Digging further into some of the links I gave shows some
efforts by others to actually try to measure all power losses from
source to load using vector analyzers and calorimeters. If you've made
similar measurements yourself, I'd certainly defer to your empirical
data.

- --
73, Paul W. Schleck, K3FU

http://www.novia.net/~pschleck/
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Old March 29th 12, 09:31 PM
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Posts: 389
Default

Maybe my answer was not clear enough - anytime you make or break a connection between the coax and the shield and a connector - some loss occurs.

When you start stacking one adapter on top of another adapter and when you use a more lossy coax - the losses multiplies.

As a example - lets say you spent $6000.00 to put up a 100' tower, a SteppIR DB antenna and a cheap Ham IV rotor and then you skimped on the coax and used some cheap Radio Shack RG 8 - open braid wire

Lets say the beam antenna produced 12 db of gain on 20 meters and the coax threw away 3 Db in 100'. Lets also assume you used a good Amphenol PL connector and one connector on each end, had one half of one Db of loss.

You just threw away 4 Db of signal.
Knowing that 3 Db / actually 2.85 is equal to a loss of 1/2 the signal - its like substituting the SteppIR DB antenna for a cheaper model.

Now - we are not just throwing away receive power, we are also throwing away transmit power / and i'm not even going to get into the costs associated with that.

To take it one step further, lets say we put up a 440 MHz repeater and we use the same Radio Shack RG 8 coax and the same PL connector @100'...

What was only 3 Db of loss at 14 MHz is now 16 Db of loss at 440 MHz.
So we go to a better grade of coax / probably hard line, and we use $150.00 connectors on each end.

We still need to concern ourselves with loss.

If we throw away even 1/2 of 1 Db with every connector and we have one connector at the top of the tower, another connector at the ground plate, another connector at the bottom of the tower, another connector on the wire going to the transmitter building, another connector at the transmitter building - before the coax enters the building, another on the other side of the ground, another at the duplexer, another at the transmitter - it isn't very long before all those connectors adds up.

When you get into Microwave frequencies it gets even worse.

Look at the cost of a 1000 watt amplifier for 14 MHz and compare that cost to a 100 watt amplifier at 2.4 GHz and then tell me which is cheaper...


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