On Sat, 14 Aug 2004 01:43:02 -0500, "Dave VanHorn"
wrote in :


"Frank Gilliland" wrote in message
.. .
On Fri, 13 Aug 2004 15:29:17 -0500, "Dave VanHorn"
wrote in :


"Southern Kiwi" wrote in message
...
Can I use my old coax and mounts from my 26 mhz days on a new uhf rig?

Probably, but how much of your signal do you want to waste, heating up the
coax?
With some types, it wouldn't be a surprise to see 3/4 of your power lost
between the rig and the antenna.. Andrews LMR-400 is good, as is all
large
hardline.


If the line is short, the type won't make much difference unless it's
RG-174 (really thin stuff). E.g, for a length of 18' @ 500 MHz I got
the following loss figures:

1/2" HL -- 0.3 dB
RG-17 -- 0.3
9913 -- 0.5
RG-8 -- 0.9

I've seen quite a spread for RG-8, and that's just from reputable
manufacturers, not including "no name" cable.
Try the calculator he http://www.ocarc.ca/coax.htm 100' of 8237 at 4.5dB
loss (over half your signal gone, in both directions btw, or 9913, which is
not bad stuff, at 2.85dB, nearly half your signal gone.. Or 9258 at (gag)
8.28dB loss, and Tandy at 8.03dB! LMR-400 at 2.69


Maybe you missed the part where I said "If the line is short...."


RG-58 -- 1.5
RG-174 -- 4.9


N connectors are much better than the old "UHF" connectors (so
named when 30 MHz was "Ultra-high frequency")

I don't know where you get your information but it's wrong. UHF
connectors work fine for UHF. And to the best of my knowledge, the
current limits of the UHF spectrum (300 MHz to 3 GHz) were defined
long before the connectors ever existed.

By "uhf" I'm assuming he means PL-259/SO239 sorts of connectors, which are
lossy at UHF.
"works" is a pretty sloppy definition. Lots of junk "works".
Works well, is a different story.

Here's one fairly authorative source:
http://www.qsl.net/vk3jeg/pl259tst.html
The charts are somewhat slow to load, but worth it.


I read the page, but it doesn't jibe with my experience. The best
example I can provide comes from servicing several dozen television
translaters over the years, ranging in frequency from 50 MHz to over
800 MHz, and most of which used the PL-259/SO-239 connectors. In fact,
I have several in the shop right now that I rescued after they were
replaced due to the recent FCC-forced conversion. But in all those
years I have never seen connector losses that come close to what he
has described (1.0 dB @ 432 MHz). Maybe tomorrow evening I'll fire up
the Adler and measure the actual losses of the connectors, but I
highly doubt it will even be measurable.


Insertion loss of about 1dB, compared to "almost immesurable" for an N
connector.

So let's take my reccomendation, LMR-400 with Ns, 100' at 3dB loss vs
middle of the road RG-8 (not the worst junk) and PL-259s at 6.5dB. So with
1W up the pipe, I get about half a watt to the antenna, you suggest that
1/4 W is ok?


I made no such suggestion, and you are assuming that the OP is using
100' when all he said was "my old coax". Again, I said, "If the line
is short...."


Here's VK3JEG's summary:
I would like to finish with these few points. The first being that the so
named UHF connector from the past is not really suitable for use above 300
MHz at all. Perhaps the exception to this would be when a cheap and rugged
system is required where loss and good signal to noise ratio is of little
concern. Unfortunately it appears that both Amateur and CB Radio UHF type
equipment fall into this category as many manufactures still supply SO-239
UHF receptors as standard equipment. (DVH: I know MANY hams that would take
exception to that!) The second point is that from our results we can see
that utilisation of the UHF connector at 146 MHz for FM type transceivers is
not such a problem. A cheap rugged connector is probably an advantage as
many FM units are used for mobile applications. However, for 144 MHz SSB
type work where low loss and good signal to noise ratio is very desirable,
again I would not recommend the use of UHF type connectors. The UHF
connector still has a place in many applications where a robust economical
RF connector is required but for serious applications its use should be
limited to below 100 Mhz. As we have shown the N type is far superior in
performance, it should also be noted the BNC type connector is similar in
performance to that of the N type but has the disadvantage of being less
rugged. In the end, one should always check with the manufactures
specifications.


I never suggested that the N-type connector -wasn't- better. I will
agree that they are better. But I said that the UHF connectors work
fine, and for the OP's intended use they will probably work just as
well as an N-type connector. This discussion reminds me of some OC
audiophiles that think their 10-watt triode amps sound better with
gold-plated capacitor screws and #2 oxygen-free speaker wires. Nobody
is saying that such components aren't better, but at some point you
need to heed the law of diminishing returns.







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"Frank Gilliland" wrote in message
...

I never suggested that the N-type connector -wasn't- better. I will
agree that they are better. But I said that the UHF connectors work
fine, and for the OP's intended use they will probably work just as
well as an N-type connector. This discussion reminds me of some OC
audiophiles that think their 10-watt triode amps sound better with
gold-plated capacitor screws and #2 oxygen-free speaker wires. Nobody
is saying that such components aren't better, but at some point you
need to heed the law of diminishing returns.

Frank I agree with your comments about "losses" in the UHF style of
connectors. The problem is the impedance bump they cause. And this varies
depending on the dielectric used. If nothing else they should use Teflon
dielectric. If you look at some of the really "cheap" ones they use some
kind of penolic that really increases the impedance bump. Also if you look
at the high quality V/UHF antenna mounts and SWR-Power Meters, that use the
female UHF connector, you will notice the center pin is held in place by
several vanes between the ID of the outer shell to the OD of the center pin.
This is NOT a cost saving measure. If you calculate the impedance of that
connector assuming the dielectric is mostly air it works out to between 40
to 50 ohms minimizing the impedance bump. When you go to a manufacture's
site to get the data sheet for a high quality V/UHF connector they state
they are not "constant impedance".


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft

"Leland C. Scott" wrote:

Ewe got mail.

On Sat, 14 Aug 2004 20:54:21 -0400, "Leland C. Scott"
wrote in :


"Frank Gilliland" wrote in message
.. .

I never suggested that the N-type connector -wasn't- better. I will
agree that they are better. But I said that the UHF connectors work
fine, and for the OP's intended use they will probably work just as
well as an N-type connector. This discussion reminds me of some OC
audiophiles that think their 10-watt triode amps sound better with
gold-plated capacitor screws and #2 oxygen-free speaker wires. Nobody
is saying that such components aren't better, but at some point you
need to heed the law of diminishing returns.

Frank I agree with your comments about "losses" in the UHF style of
connectors. The problem is the impedance bump......


Leland,

Measure it. If you actually find this impedance "bump", maybe you can
explain why impedance is so significant for these connectors while
impedance will "unnecessarily complicate things" for mag-mounts. Are
you saying that impedance is important for connectors but not for
antenna grounds? Why not fall back to your "pure capacitance" excuse
where UHF connectors are concerned?

Make up your mind, Leland. What's important -- impedance or 'pure
capacitance'?






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"Frank Gilliland" wrote in message
...
Measure it. If you actually find this impedance "bump", maybe you can
explain why impedance is so significant for these connectors

You checked your E-mail? You have the detailed answer there in the attached
zip file.

while
impedance will "unnecessarily complicate things" for mag-mounts.

You have "unnecessarily complicate things" because you don't understand the
difference.

Are
you saying that impedance is important for connectors but not for
antenna grounds?

See the file I sent to you.

Why not fall back to your "pure capacitance" excuse
where UHF connectors are concerned?

Why don't you explain it. Funny why "N" connectors and other "constant
impedance" connectors are used at UHF almost exclusively.

Make up your mind, Leland. What's important -- impedance or 'pure
capacitance'?

Its very clear to me Frank. What is also clear is you don't.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft

On Sun, 15 Aug 2004 16:26:51 -0400, "Leland C. Scott"
wrote in :


"Frank Gilliland" wrote in message
.. .
Measure it. If you actually find this impedance "bump", maybe you can
explain why impedance is so significant for these connectors

You checked your E-mail? You have the detailed answer there in the attached
zip file.


Mailbox is empty. Did you remove the "nospam"?


while
impedance will "unnecessarily complicate things" for mag-mounts.

You have "unnecessarily complicate things" because you don't understand the
difference.


Now that's an interesting answer..... the difference between impedance
and capacitance is that I don't understand the difference?


Are
you saying that impedance is important for connectors but not for
antenna grounds?

See the file I sent to you.


Checked again. Still empty.


Why not fall back to your "pure capacitance" excuse
where UHF connectors are concerned?

Why don't you explain it.


Alrighty.....

Any capacitor is basically a network of capacitance, inductance and
resistance. The circuit can't see the "pure capacitance" without
seeing the inductance and resistance, hence the necessity of measuring
a capacitor as an impedance since impedance = resistance + reactance.
And because frequency is directly related to reactance, impedance
changes in relation to frequency. The other issue to consider is the
dielectric of the capacitance, which will affect the frequency
linearity (Z/f curve) of the device. For all practical purposes, only
vacuum and air capacitors are linear in this respect -- all others are
not. This means that as the frequency changes, so will the resistance
and/or 'pure' capacitance, or both. And this is why you -must- measure
impedance at the operating frequency.

As far as connectors are concerned, both N-type and UHF-type
connectors are low-impedance coaxial designs, so unless the wavelength
is a few cm or higher there will be little or no reflection due to
impedance mismatch (assuming there -is- an impedance mismatch). With
that out of the way, the insulation is the other cause of concern. It
is effectively the dielectric of the capacitance between the center
conductor and the shield. So in this respect, the quality of the
connector depends on the quality of the insulation. Cheap insulation
will have poor high-frequency characteristics, while.... well, you get
the idea. So if there is power loss it will be due to poor insulation
properties (cheap materials, contamination, etc.). And -that- is why
the N-type connectors are preferred for UHF and up since it is (or
rather, it's -supposed- to be) a sealed connector, thereby preventing
humidity and other crud from contaminating the dielectric (or
corroding the contacts) and therefore causing power loss.

There you have it. It's ironic that while impedance is the primary
factor in both these issues, you have misunderstood both from totally
opposite ends of the spectrum. But hey, nobody's perfect.


Funny why "N" connectors and other "constant
impedance" connectors are used at UHF almost exclusively.

Make up your mind, Leland. What's important -- impedance or 'pure
capacitance'?

Its very clear to me Frank. What is also clear is you don't.


Checked again. Mailbox is still empty.





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"Frank Gilliland" wrote in message
...
Mailbox is empty. Did you remove the "nospam"?

I did. In fact I just sent it again just now. It does have a file attached
so if your E-mail program filters out mail with attachments you will have to
turn it off.


while
impedance will "unnecessarily complicate things" for mag-mounts.

You have "unnecessarily complicate things" because you don't understand
the
difference.


Now that's an interesting answer..... the difference between impedance
and capacitance is that I don't understand the difference?

You haven't impressed me with knowing the difference. I was addressing a
capacitance measurement only, exclusively and separate from any other
electrical property. You can't seem to figure out that your impedance
measurement combines capacitance, inductance, and resistance all together.

If I took a 1000pf vacuum capacitor and connected it in series with a 1000
ohm resistor, placed it in a black box you can't open, and brought out two
leads for you to connect to your Z-bridge then asked you to make your
measurement you would tell me I have a crappy capacitor. Then if I wanted to
give you somthing to think about I can stick a small inductor in series with
the capacitor and resistor to give some strange impedance variations with
frequency. Now try to figure out what's in the box from your Z-bridge
measurement. That's the problem you have with your measurements where the
black box is the mag-mount. Making a capacitance measurenet, or some simple
calculations, would be like peeking inside the black box and saying, Oh now
I see what is going on.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft

On Sun, 15 Aug 2004 18:25:15 -0400, "Leland C. Scott"
wrote in :


"Frank Gilliland" wrote in message
.. .
Mailbox is empty. Did you remove the "nospam"?

I did. In fact I just sent it again just now. It does have a file attached
so if your E-mail program filters out mail with attachments you will have to
turn it off.


I got the file with the pics. Nice work, and I'm glad to see your
acceptance of the fact that solid dielectrics (even teflon) have
dielectric constants that aren't constant with frequency. However,
your description of a UHF-type connector isn't particularly accurate.
If you had ever taken one apart you would have noticed that only a
small part of the conductor (maybe a mm or two) is actually contacting
the insulator. The rest is surrounded by an air gap, making most of
the coupled connection a section of coax using an insulator with a
dielectric constant of 1.

Regardless, I suggested that you -measure- this apparent loss, not
calculate it (.....gee, seems I've said that before.....). Since you
don't care to measure things, I did. The Adler I mentioned earlier is
a 100-watt translator tuned for TV channel 77. I measured the output
to my wattmeter through one 12' length of RG-11 and again through two
6' lengths of RG-11, the difference being that the latter adds a male
and female UHF-type connector to the line. The wattmeter showed no
visible difference. So I did the same test directly to the dummy load
and measured with an RF voltmeter at the dummy load. The difference
was a loss of 0.4 volts, which is slightly less than 1 watt, or about
0.05 dB. Yes, I use teflon connectors and I keep them clean. And no,
the coax wasn't overheated during soldering (it's all about the
technique!).

Feel free to repeat my tests, both for the UHF-type connectors and for
the mag-mounts. Just don't feed me any more calculations cause they
don't mean squat when the facts show something different.


while
impedance will "unnecessarily complicate things" for mag-mounts.

You have "unnecessarily complicate things" because you don't understand
the
difference.


Now that's an interesting answer..... the difference between impedance
and capacitance is that I don't understand the difference?

You haven't impressed me with knowing the difference.


It was intended to educate, not to impress.


I was addressing a
capacitance measurement only, exclusively and separate from any other
electrical property. You can't seem to figure out that your impedance
measurement combines capacitance, inductance, and resistance all together.


Yes it does! That's the point! Capacitance, "exclusively and separate
from any other electrical property", is academic and has no practical
value!


If I took a 1000pf vacuum capacitor and connected it in series with a 1000
ohm resistor, placed it in a black box you can't open, and brought out two
leads for you to connect to your Z-bridge then asked you to make your
measurement you would tell me I have a crappy capacitor.


Not at all. You can tell if the reactance is linear simply by changing
the frequency feeding your impedance bridge. If it's linear then the
capacitor is fine and you simply have 1k ohms of series resistance. If
it's not linear then you might have a problem (depending on the
intended application of this 'black box').


Then if I wanted to
give you somthing to think about I can stick a small inductor in series with
the capacitor and resistor to give some strange impedance variations with
frequency. Now try to figure out what's in the box from your Z-bridge
measurement.


Just swing the signal generator up from zero until you dip, just like
you would with a GDO. That's your resistance. If it peaks instead of
dipping then your reactances are in parallel and you must measure
resistance at DC. Then detune to measure reactances.

And at this point I need to make a point: What I just described is a
quick summary of the basic operation of a simple impedance bridge. The
impedance bridge is one of the most fundamental yet most useful tools
in radio. Now you claim to have a degree -and- you are a ham. For you
to even suggest that one can't determine the properties of an unknown
impedance network using an impedance bridge tells me that you have
never used one, or at least not more than once or twice. If you -do-
have a degree then either it isn't in electronics, you missed a lot of
labs, or the school was criminally negligent in it's course of study.
Either way, here's a few links to get you going:

http://www.tpub.com/content/neets/14...s/14193_89.htm
ftp://bama.sbc.edu/downloads/heath/am1/
ftp://bama.sbc.edu/downloads/knight/z-brdg/

And here's a fascinating page on the dielectric properties of organic
tissue that also includes instructions for an impedance bridge. Note
the problems with electrode polarization at low frequencies when
measuring lossy dielectrics (iow, maybe you should take a second look
at your low-frequency DMM method of measuring a capacitor having a
dielectric of epoxy or paint):

http://safeemf.iroe.fi.cnr.it/docs/H...K/chp4-2-1.htm


That's the problem you have with your measurements where the
black box is the mag-mount. Making a capacitance measurenet, or some simple
calculations, would be like peeking inside the black box and saying, Oh now
I see what is going on.


Here's another "black box" scenario: Using the capacitance tester on
your DMM, measure the "pure" capacitance between two high impedance
windings of a power or audio transformer. I can tell you right now
that your measurement will be wrong, and you can't tell what's in the
"box" unless you change the frequency. Same deal for the mag-mount.






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"Leland C. Scott" wrote:
You checked your E-mail?

Have you checked yours, coward?

14 mile road!

--
Madness takes its toll. Please have exact change ready.

On Sun, 15 Aug 2004 16:26:51 -0400, "Leland C. Scott"
wrote in :


"Frank Gilliland" wrote in message
.. .
Measure it. If you actually find this impedance "bump", maybe you can
explain why impedance is so significant for these connectors

You checked your E-mail? You have the detailed answer there in the attached
zip file.


I finally got the file but the images are sourced for a local
directory. If you want to send an html that will pull pics from a
remote website, the full url must be used in the call or the website
must be sourced in the header.





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