Can I use my old coax and mounts from my 26 mhz days on a new uhf rig?
--
Cheers
Southern Kiwi

Word of wisdom from high in the mountains....you know...like a Guru...but
not as old....or mystic......or wise....or high...

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

"Dave VanHorn" wrote in message
...

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

I am wanting to use it on a 476 MHz set putting out 5 watts only

I am wanting to use it on a 476 MHz set putting out 5 watts only

Well, not knowing exactly what you have, I'd say look on the side of the
coax, and find the loss figures online. If it's low cost stuff that was
"ok" for 30 MHz, it's likely lossy as hell at half a GHz.

I use LMR-400 for that sort of thing, which is not lossless, but it's pretty
darned good.

The connectors themselves won't be horrible, but I wouldn't put PL-259's and
similar on LMR-400. That would be a waste of good cable. You really want N
connectors up here.

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
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.






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"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

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.
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?

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.

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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