Dave Platt wrote:
That same diode-like effect also seems to be capable of causing the
cable to generate a nontrivial amount of broadband noise, when
energized by a sufficiently strong transmitter signal.

Yeah, I've seen some of that. I spent several days finding the
culprit on a UHF repeater where the over the air rx sensitivity varied
substantially and erratically. Watching the IF noise level, showed it
going up and down with the sensitivity changes. In frustration, I
grabbed a broomstick and beat on the accessible coax cables. I
eventually found a length of 9913 coax that was apparently involved. I
replaced it, and the noise problem disappeared. Inspecting the coax
carefully, the outer jacket was slightly corroded and white dust was
visible.

In simplex
applications this seems not to matter, but in repeater applications it
tends to cause enough of an increase in the noise floor at the
receiver to appreciably de-sensitize the receiver.

Yep, but the mechanism isn't obvious. All transmitters belch some
level of synthesizer or oscillator noise. The notch type duplexer
does a great job of getting rid of the noise in the receiver bandpass
produced by the transmitter. However, when there's a diode present,
the very low level tx synthesizer spurs, or other signals picked up at
the antenna, mix with the tx synthesizer noise, and land on the
receiver frequency. It's intermod, but instead of dealing with a
collection of individual frequencies, it deals with broadband noise.
The same mechanism is a problem in broadband mux, broadcast, and
cellular systems.

The system I work on, was originally build with LMR-type feedlines
within the cabinet, and didn't "hear" particularly well. When the
chief hardware guru threw out all of those (well-constructed)
pigtails, and replaced them with 1/4" heliax... the problem went away
and has not returned.

Requiring Heliax is a good but expensive solution. Requiring Heliax
on initial installation makes is somewhat less expensive.

Heliax is good. Double-braid shielded cable (with silver-plated
copper braid, not aluminum) seems to be almost as good.

Sorta. I have problems securely attaching connectors to RG-213/u.
Unlike the rigid and semi-rigid cables, crimp type connectors are
problematic. In addition, much of the RG-213/u floating around is NOT
silver plated, but bare copper. That will corrode, and form diodes.

I also don't like the attenuation of RG-213/u. 5.1dB/100ft at 450MHz,
while LMR-400 is 2.7dB/100ft at 450MHz.

On 11 Sep 2011 13:32:15 GMT, dave wrote:
Interesting. I always hear people bragging about LMR. Are we using the
term "Heliax" generically? Is semi-flex no good too, (It's all aluminum
and brass metallically isn't it?)

A picture is worth 1000 words:
Heliax:
http://www.google.com/search?tbm=isch&q=heliax
LMR type coax:
http://www.google.com/search?tbm=isch&q=LMR+coax

I've never heard of semi-flex. Perhaps you mean semi-rigid coax,
which includes aluminum outer jacket coax as used in the CATV
industry? The coax is fine, but where it transitions to a brass or
silver plated connector, there's a problem. In general, it's a bad
idea for reducing PIM (although I use CATV coax because I'm cheap).

Did your guru make a profit on the replacement cables?

Guru's do not stay in business very long unless they're profitable.
Even the glorified poverty style of guru has to eat.

How do you know a
$15 can of Cramolin wouldn't have helped just as much?

Cramolin is now DeOxit and has been reformulated.
http://store.caig.com/s.nl/sc.2/.f
It's a total disaster on RF connectors because it contains oleic acid,
which is great for removing oxides from electrical contacts, but
equally good at rotting off the plating from connectors over long time
periods. The reformulated DeOxit allegedly contains a different
anti-oxidant, which allegedly has the same effect.

Tinned copper braid is OK, no?

Dunno. I never use tinned braid except for some semi-rigid microwave
coax, which is quite stiff. Most often I see tin plated braid. Since
tin is not magnetic, there's no PIM problem.

http://www.corrosionist.com/Corros1.gif

--
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:

Cramolin is now DeOxit and has been reformulated.
http://store.caig.com/s.nl/sc.2/.f
It's a total disaster on RF connectors because it contains oleic acid,
which is great for removing oxides from electrical contacts, but
equally good at rotting off the plating from connectors over long time
periods. The reformulated DeOxit allegedly contains a different
anti-oxidant, which allegedly has the same effect.


Cramolin is still alive and well. It was and still is made in Germany,
DeOxit is made in the US, Caig used to be the US distributor of Cramolin
products, but went their own way, with a different formula.

I'm not sure which one is the one that you call "a total disaster", but
AFIK neither is to be used for anything except cleaning. Caig sells
solutions (pardon the pun) for use on connectors.

I have them because I can only buy DeOxit in small tubes off of eBay and
still get it shipped here, and that was the only way I could get fader lube,
but I have never used them.

Don't go looking it up and show me auctions of just fader lube, after I
ordered the sets, which did not show I up, I commented to the vendor
that I wanted just the fader lube and now they list it.
They also replaced the missing packages.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Making your enemy reliant on software you support is the best revenge.

On Sun, 11 Sep 2011 17:29:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:

Jeff Liebermann wrote:

Cramolin is now DeOxit and has been reformulated.
http://store.caig.com/s.nl/sc.2/.f
It's a total disaster on RF connectors because it contains oleic acid,
which is great for removing oxides from electrical contacts, but
equally good at rotting off the plating from connectors over long time
periods. The reformulated DeOxit allegedly contains a different
anti-oxidant, which allegedly has the same effect.

Cramolin is still alive and well. It was and still is made in Germany,
DeOxit is made in the US, Caig used to be the US distributor of Cramolin
products, but went their own way, with a different formula.

Got it. All I can find it DeOxit in California.
More detail:
http://siber-sonic.com/electronics/caig.html

I'm not sure which one is the one that you call "a total disaster", but
AFIK neither is to be used for anything except cleaning. Caig sells
solutions (pardon the pun) for use on connectors.

Different stuff. Most of it is just grease to keep the connectors
from oxidizing. The total disaster was what I found on a tower where
someone had used Cramolin to clean an assortment of 7/16 DIN and N
connectors. The 7/16 DIN connectors were stainless. They turned
black and had a rough pitted surface. The N-connectors were silver on
brass. The silver was intact, but would flake off in small pieces,
exposing the underlying brass, which rapidly turned dark green.
Everything had to be replaced. I don't recall how long it took to get
to this point but I think it was at least 2-3 years.

If you Google for corrosion characteristics of oleic acid, you'll find
that it attacks steels, but is compatible with copper. Not true. Pure
oleic is compatible, but add some water and the stuff becomes
corrosive.

Oleic acid is a major component (70%?) of peanut oil. You could
probably use peanut oil mixed with some organic solvent in place of
Cramolin. (No, I haven't tried it).

I have them because I can only buy DeOxit in small tubes off of eBay and
still get it shipped here, and that was the only way I could get fader lube,
but I have never used them.

Don't go looking it up and show me auctions of just fader lube, after I
ordered the sets, which did not show I up, I commented to the vendor
that I wanted just the fader lube and now they list it.
They also replaced the missing packages.

I mix many of my own chemicals. Most of the tuner lube type stuff is
fairly simple. Organic solvent, ionic solvent (water soluble), oxide
remover, and some oil:
http://store.caig.com/s.nl/sc.2/category.293/.f

--
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:

Got it. All I can find it DeOxit in California.
More detail:
http://siber-sonic.com/electronics/caig.html

I believe on of the reasons that Caig stopped carrying it was that it is
too corrosive to put on an airplane and they wanted something UPS/FEDEX
would carry.

Different stuff. Most of it is just grease to keep the connectors
from oxidizing. The total disaster was what I found on a tower where
someone had used Cramolin to clean an assortment of 7/16 DIN and N
connectors. The 7/16 DIN connectors were stainless. They turned
black and had a rough pitted surface. The N-connectors were silver on
brass. The silver was intact, but would flake off in small pieces,
exposing the underlying brass, which rapidly turned dark green.
Everything had to be replaced. I don't recall how long it took to get
to this point but I think it was at least 2-3 years.

Ok, good thing I only use it to clean contacts and that's a drop on the end
of a q-tip or toothpick.

I mix many of my own chemicals. Most of the tuner lube type stuff is
fairly simple. Organic solvent, ionic solvent (water soluble), oxide
remover, and some oil:
http://store.caig.com/s.nl/sc.2/category.293/.f

For me those days have passed. Between space limitations, lack of working
area, inability to order those chemicals, etc, I'm going to have to make
do with little tubes sent airmail. Luckily I don't need much and have
all I need for a long time. :-)

Geoff.


--
Geoffrey S. Mendelson N3OWJ/4X1GM
Making your enemy reliant on software you support is the best revenge.

On Sun, 11 Sep 2011 18:39:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:

I believe on of the reasons that Caig stopped carrying it was that it is
too corrosive to put on an airplane and they wanted something UPS/FEDEX
would carry.

Duh... They carry peanut oil, which is 75% oleic acid, but won't
carry Cramolin, which is 5% oleic acid. I just checked the 49 CFR
list at:
http://www.ups.com/content/us/en/resources/ship/hazardous/download/chemical.html
and Oleic acid isn't listed. The MSDS sheet shows slightly flamable,
but otherwise safe. My guess(tm) is the business relationship fell
apart and that the UPS/Fedex story isn't true.

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

In article ,
Jeff Liebermann wrote:

Sorta. I have problems securely attaching connectors to RG-213/u.
Unlike the rigid and semi-rigid cables, crimp type connectors are
problematic. In addition, much of the RG-213/u floating around is NOT
silver plated, but bare copper. That will corrode, and form diodes.

Yeah, you have to make sure you're getting the "good stuff", with
silver-plated copper braid... and then (I think) solder, rather
than crimp.

Interesting. I always hear people bragging about LMR. Are we using the
term "Heliax" generically? Is semi-flex no good too, (It's all aluminum
and brass metallically isn't it?)

A picture is worth 1000 words:
Heliax:
http://www.google.com/search?tbm=isch&q=heliax
LMR type coax:
http://www.google.com/search?tbm=isch&q=LMR+coax

I've never heard of semi-flex. Perhaps you mean semi-rigid coax,
which includes aluminum outer jacket coax as used in the CATV
industry? The coax is fine, but where it transitions to a brass or
silver plated connector, there's a problem. In general, it's a bad
idea for reducing PIM (although I use CATV coax because I'm cheap).

See http://www.isoconnector.com/cableassemblies.html - "semi-rigid"
and "semi-flex" are different constructions.

Cramolin is now DeOxit and has been reformulated.

Well, sorta and sorta not. Cramolin is still made by the original
(German) manufacturer, but isn't easily acquired in the U.S. DeOxIt
is made by Caig, who used to import Cramolin but are now making a
similar product themselves.

It's a total disaster on RF connectors because it contains oleic acid,
which is great for removing oxides from electrical contacts, but
equally good at rotting off the plating from connectors over long time
periods. The reformulated DeOxit allegedly contains a different
anti-oxidant, which allegedly has the same effect.

My recollection is that the instructions which came with Cramolin said
that you should clean the remains of the "red" Cramolin (the oxide
remover) off of the contacts after de-oxidizing.

They made another "blue" product which was intended to provide some
residual anti-re-tarnishing protection... I think it was based on palm
oil.

When I use Cramolin (I still have a bit of the concentrate) or DeOxIt
on contacts, I follow it with a final cleaning using isopropyl or
denatured alcohol (or acetone if I'm feeling really thorough), to
remove the remains of the anti-oxidant.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Dave Platt" wrote in message
...

snip

When I use Cramolin (I still have a bit of the concentrate) or DeOxIt
on contacts, I follow it with a final cleaning using isopropyl or
denatured alcohol (or acetone if I'm feeling really thorough), to
remove the remains of the anti-oxidant.


Isn't there any concern for plastic deterioration from the acetone? When I
read what you wrote, I cringed, having seen acetone's effect on (some)
plastics. Keeping a few four-leaf clovers on the bench?

73,
Sal

When I use Cramolin (I still have a bit of the concentrate) or DeOxIt
on contacts, I follow it with a final cleaning using isopropyl or
denatured alcohol (or acetone if I'm feeling really thorough), to
remove the remains of the anti-oxidant.


Isn't there any concern for plastic deterioration from the acetone? When I
read what you wrote, I cringed, having seen acetone's effect on (some)
plastics. Keeping a few four-leaf clovers on the bench?

It depends on what sort of thing I'm cleaning. You're correct... I
don't use acetone on anything plastic.

Depending on the plastic, either an alcohol, or a light petroleum
solvent (Stoddard solvent, naptha, etc.) is a safer "wash".

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Sun, 11 Sep 2011 10:57:31 -0700, (Dave Platt)
wrote:

See http://www.isoconnector.com/cableassemblies.html - "semi-rigid"
and "semi-flex" are different constructions.

Thanks. I've been calling both types semi-rigid, which is wrong.

They made another "blue" product which was intended to provide some
residual anti-re-tarnishing protection... I think it was based on palm
oil.

No clue on the oil, but my guess would be cheaper mineral oil and some
solvent to wash off any residue from Cramolin red. I've never used
(or seen) Cramolin Blue.

When I use Cramolin (I still have a bit of the concentrate) or DeOxIt
on contacts, I follow it with a final cleaning using isopropyl or
denatured alcohol (or acetone if I'm feeling really thorough), to
remove the remains of the anti-oxidant.

I use 409 cleaner, which has a pH of about 11, or ammonia window
cleaner, both of which should neutralize the acid. Acetone will make
a mess of anything plastic and really is overkill. For open frame
relays, I sometime use electroless silver to replate the contacts. I
also have a diy silver brush plating kit, which I use large contacts.

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

In article ,
Jeff Liebermann wrote:

When I use Cramolin (I still have a bit of the concentrate) or DeOxIt
on contacts, I follow it with a final cleaning using isopropyl or
denatured alcohol (or acetone if I'm feeling really thorough), to
remove the remains of the anti-oxidant.

I use 409 cleaner, which has a pH of about 11, or ammonia window
cleaner, both of which should neutralize the acid. Acetone will make
a mess of anything plastic and really is overkill.

True - it's for metals-only applications.

For open frame
relays, I sometime use electroless silver to replate the contacts.

Is that Cool-Amp (powder), or some form of liquid electroless silver?

I've made up (and use) a homebrew substitute for Cool-Amp - silver
chloride and salt, finely ground, and then rubbed in firmly. Makes a
nice, solderable surface for DIY PC boards.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!