audio recording on IC -help wanted

michael nikolaou wrote:
Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the contact
of the driver relay i placed one RC snubber circut (27NF with 100 R
resisitor in series) to help with some spikes that were influencing the low
voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform to 0
volt after 5 periods of 500 HZ but no overshoot. The relay presents no
arcing. If i remove the snubber and make the experiment the best place to
switch is zero crossing but i also see large SHARP spikes up to 500 Volts
Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael


Hello,


Two comments:


If the load is not purely resistive, there will be a voltage current
shift, aka Eli ICE Man... therefore in this case zero voltage crossing
is not at all zero current crossing and you may be creating more problem
by switching at the worst (or just a bad) time) .

BY looking at the signal that the rc snubber is trying to "tame" , you
adjust RC unitl you get a "critically damped response. you can dampen
more, but at the cost of higher stand by leakage via the RC, as it
becomes a part of the load too!

Good luck, this is an often asked problem, and the ability to visualizes
on scope and make changes and observations, will help you forever. This
is a re-occcuring problem and it is the variations in the load that
cause engineers to have to re-visit the solutions

Best regards

Marco
 
m.a wrote:

Hello,

I am looking for an evaluation board that has an MCU (preferably low
power) and an ADC and UART.

I want that I program MCU in such a way that when it gets a command from
UART, it get 1000 samples from ADC and place on RAM and at the end of
capturing sending them to another system via UART.

speed of transfer to other system via UART is not important ( I have several
minute to do so).

ADC sampling rate should be 100KSPS.



Any help in selecting a suitable evaluation board is very appreciated.



Regards




Look at AVR or Pic Programable chips.
They'll do what you need in a small non complicated package.
You just need to code alittle but not much..


http://webpages.charter.net/jamie_5"
 
On Tue, 29 Apr 2008 18:31:08 +0000, Joerg wrote:

Hello Folks,

Is there any model, research results etc. for RF transformers that
feature extreme turns ratios such 100:1 and more? I am mainly interested
in leakage inductance, bandwidth and such. Bandwidth doesn't have to be
more than an octave, single digit MHz range. It just can't be resonant,
at least not a lot.

I know this is a far stretch but maybe ...
A bandwidth of around an octave implies _some_ resonance.

You'll have a huge juggling job between leakage inductance and primary
inductance.

The more loss you can stand the better chance you'll have of making it
work. I'd feel a strong sense of accomplishment if I got 50% of my input
power coming out of my secondary.

I recall reading in some ARRL publication or another (the one on
transmission line transformers, I think) that to achieve extreme ratios
you can often do better using two stages -- in your case perhaps three?
4:1 * 5:1 * 5:1 = 100:1.

Disclaimer: never done it, I wasn't there, it's not my fault, etc.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
 
Tim Wescott wrote:
On Tue, 29 Apr 2008 18:31:08 +0000, Joerg wrote:

Hello Folks,

Is there any model, research results etc. for RF transformers that
feature extreme turns ratios such 100:1 and more? I am mainly interested
in leakage inductance, bandwidth and such. Bandwidth doesn't have to be
more than an octave, single digit MHz range. It just can't be resonant,
at least not a lot.

I know this is a far stretch but maybe ...

A bandwidth of around an octave implies _some_ resonance.
On extreme ratios you just can't avoid it.


You'll have a huge juggling job between leakage inductance and primary
inductance.
Yes, and you can never have half turns like at some restaurants.


The more loss you can stand the better chance you'll have of making it
work. I'd feel a strong sense of accomplishment if I got 50% of my input
power coming out of my secondary.

I recall reading in some ARRL publication or another (the one on
transmission line transformers, I think) that to achieve extreme ratios
you can often do better using two stages -- in your case perhaps three?
4:1 * 5:1 * 5:1 = 100:1.
Unfortunately that won't work in this case. It's usually only ok if you
have an active stage inbetween.


Disclaimer: never done it, I wasn't there, it's not my fault, etc.
Maybe you could come visit at the hospital if it blows up in my face ;-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
On May 1, 11:57 am, "amdx" <a...@knology.net> wrote:
"Joerg" <notthisjoerg...@removethispacbell.net> wrote in message

news:CV0Sj.981$To6.131@newssvr21.news.prodigy.net...



Tim Wescott wrote:
On Tue, 29 Apr 2008 18:31:08 +0000, Joerg wrote:

Hello Folks,

Is there any model, research results etc. for RF transformers that
feature extreme turns ratios such 100:1 and more? I am mainly interested
in leakage inductance, bandwidth and such. Bandwidth doesn't have to be
more than an octave, single digit MHz range. It just can't be resonant,
at least not a lot.

I know this is a far stretch but maybe ...

A bandwidth of around an octave implies _some_ resonance.

On extreme ratios you just can't avoid it.

You'll have a huge juggling job between leakage inductance and primary
inductance.

Yes, and you can never have half turns like at some restaurants.

Please give some more information about why you can never have half turns.
I remember
overheating a transformer that used a half turn. Never tried half turns
again. But what is the reason the half turn gets hot?
Mike
With a toroid core, it should be obvious why you can have only
integral numbers of turns. In an E-I core, or a pot core with
openings on both sides, you can have a wire exit a different place
than it entered. The loop then closes around one of the outside
"legs" of the core. Note that this is equivalent to a full number of
turns around the center post, and one turn around the outer post, with
the two connected in series. IF the magnetics are balanced, the field
in the outer leg will be half the field in the center leg. But this
happens only if there is no current in the turn around the outer leg.
Note that the "half turn" is not strongly coupled to the rest of the
turns, and as a result adds a lot of leakage inductance. I don't see
why the "half" turn itself should get hot, but if it diverts the
magnetic field into the other leg in such a way that it significantly
increases the core loss in that leg, it could lead to excess power
loss in the transformer.

Cheers,
Tom
 
Tom Bruhns wrote:

With a toroid core, it should be obvious why you can have only
integral numbers of turns. In an E-I core, or a pot core with
openings on both sides, you can have a wire exit a different place
than it entered. The loop then closes around one of the outside
"legs" of the core. Note that this is equivalent to a full number of
turns around the center post, and one turn around the outer post, with
the two connected in series. IF the magnetics are balanced, the field
in the outer leg will be half the field in the center leg. But this
happens only if there is no current in the turn around the outer leg.
Note that the "half turn" is not strongly coupled to the rest of the
turns, and as a result adds a lot of leakage inductance. I don't see
why the "half" turn itself should get hot, but if it diverts the
magnetic field into the other leg in such a way that it significantly
increases the core loss in that leg, it could lead to excess power
loss in the transformer.
Here is a patent on the subject:
http://www.freepatentsonline.com/6348848.html


--
Regards,

John Popelish
 
Tom Bruhns wrote:
On May 1, 12:32 pm, Tom Bruhns <k7...@msn.com> wrote:

On May 1, 11:57 am, "amdx" <a...@knology.net> wrote:




"Joerg" <notthisjoerg...@removethispacbell.net> wrote in message

news:CV0Sj.981$To6.131@newssvr21.news.prodigy.net...

Tim Wescott wrote:

On Tue, 29 Apr 2008 18:31:08 +0000, Joerg wrote:

Hello Folks,

Is there any model, research results etc. for RF transformers that
feature extreme turns ratios such 100:1 and more? I am mainly interested
in leakage inductance, bandwidth and such. Bandwidth doesn't have to be
more than an octave, single digit MHz range. It just can't be resonant,
at least not a lot.

I know this is a far stretch but maybe ...

A bandwidth of around an octave implies _some_ resonance.

On extreme ratios you just can't avoid it.

You'll have a huge juggling job between leakage inductance and primary
inductance.

Yes, and you can never have half turns like at some restaurants.

Please give some more information about why you can never have half turns.
I remember
overheating a transformer that used a half turn. Never tried half turns
again. But what is the reason the half turn gets hot?
Mike

With a toroid core, it should be obvious why you can have only
integral numbers of turns. In an E-I core, or a pot core with
openings on both sides, you can have a wire exit a different place
than it entered. The loop then closes around one of the outside
"legs" of the core. Note that this is equivalent to a full number of
turns around the center post, and one turn around the outer post, with
the two connected in series. IF the magnetics are balanced, the field
in the outer leg will be half the field in the center leg. But this
happens only if there is no current in the turn around the outer leg.
Note that the "half turn" is not strongly coupled to the rest of the
turns, and as a result adds a lot of leakage inductance. I don't see
why the "half" turn itself should get hot, but if it diverts the
magnetic field into the other leg in such a way that it significantly
increases the core loss in that leg, it could lead to excess power
loss in the transformer.

Cheers,
Tom


Which got me to thinking: you can keep the magnetics in the two outer
legs balanced (that is, the rate of change of flux per unit time) if
you put a turn around each and put those two turns in parallel.
However, each will see half the flux that's in the center leg, so will
contribute half a turn's voltage...this could be an interesting way to
get a high step-up ratio with fewer secondary turns: only 50 turns
instead of 100, to get a 1:100. That could be an advantage in keeping
the parasitic capacitance on the secondary at bay, though the
effective capacitance is generally a very weak function of the actual
number of turns--and for modest permeability cores, significantly
lowers the pri:sec coupling as compared with having the windings co-
axial.
there is a pretty picture of exactly that in Keith Billings SMPS book.

in some cases the leakage can be exploited.

I have a humungous iron powder core with 8.5 turns on it. its an
inductor, so I dont care about the leakage.

Cheers
Terry
 
On May 1, 12:32 pm, Tom Bruhns <k7...@msn.com> wrote:
On May 1, 11:57 am, "amdx" <a...@knology.net> wrote:



"Joerg" <notthisjoerg...@removethispacbell.net> wrote in message

news:CV0Sj.981$To6.131@newssvr21.news.prodigy.net...

Tim Wescott wrote:
On Tue, 29 Apr 2008 18:31:08 +0000, Joerg wrote:

Hello Folks,

Is there any model, research results etc. for RF transformers that
feature extreme turns ratios such 100:1 and more? I am mainly interested
in leakage inductance, bandwidth and such. Bandwidth doesn't have to be
more than an octave, single digit MHz range. It just can't be resonant,
at least not a lot.

I know this is a far stretch but maybe ...

A bandwidth of around an octave implies _some_ resonance.

On extreme ratios you just can't avoid it.

You'll have a huge juggling job between leakage inductance and primary
inductance.

Yes, and you can never have half turns like at some restaurants.

Please give some more information about why you can never have half turns.
I remember
overheating a transformer that used a half turn. Never tried half turns
again. But what is the reason the half turn gets hot?
Mike

With a toroid core, it should be obvious why you can have only
integral numbers of turns. In an E-I core, or a pot core with
openings on both sides, you can have a wire exit a different place
than it entered. The loop then closes around one of the outside
"legs" of the core. Note that this is equivalent to a full number of
turns around the center post, and one turn around the outer post, with
the two connected in series. IF the magnetics are balanced, the field
in the outer leg will be half the field in the center leg. But this
happens only if there is no current in the turn around the outer leg.
Note that the "half turn" is not strongly coupled to the rest of the
turns, and as a result adds a lot of leakage inductance. I don't see
why the "half" turn itself should get hot, but if it diverts the
magnetic field into the other leg in such a way that it significantly
increases the core loss in that leg, it could lead to excess power
loss in the transformer.

Cheers,
Tom
Which got me to thinking: you can keep the magnetics in the two outer
legs balanced (that is, the rate of change of flux per unit time) if
you put a turn around each and put those two turns in parallel.
However, each will see half the flux that's in the center leg, so will
contribute half a turn's voltage...this could be an interesting way to
get a high step-up ratio with fewer secondary turns: only 50 turns
instead of 100, to get a 1:100. That could be an advantage in keeping
the parasitic capacitance on the secondary at bay, though the
effective capacitance is generally a very weak function of the actual
number of turns--and for modest permeability cores, significantly
lowers the pri:sec coupling as compared with having the windings co-
axial.
 
On Fri, 30 May 2008 06:11:46 -0400, JW <none@dev.nul> wrote:

Hello all,

We've received a reel of 1,000 SRAM parts from PartMiner that were deemed
counterfeit by the folks at Cypress. Due to availability issues in
March we were forced to buy from this broker, even though they've screwed
us in the past with counterfeit parts and I've pleaded with them not to
buy from them (or any broker) again. The failure rate of the chips at
initial test is about 10%. The chips in question are 256kb async SRAMS
marked:

CY7C199D-10VXI
0544 G 04
637944

After contacting Cypress, their response was:

"Based on the information (top marking) that you provided , our lot
history verification showed that it is "not" a Cypress device. Please be
guided that Cypress guarantees only parts that were bought from Cypress or
authorized distributors. Attached is the official Cypress Broker Letter."
You might like to point out to them that if their availability was better you wouldn't have to look
elsewhere....
 
Taitaisiko olla jo kolmatta viikoa putkeen , kun jatkuvat yöpakkaset
koettelevat ydinaavikoituvaa Suomeamme jo ilman loppua? Joka tapauksessa
jälleen kerran oli kovat pakkasjaksot ja huurakuuraa maat valkoisenaan. Ei
kuulu tiedotusmonopoleissamme paljon lauluja siitä, että minne katosi ne CO2
kuumentamat päivät? Etteikö peräti olisi ydinaavikoituminen syönyt samaa
hyömyä kuin ennätyskuivuus biotooppejamme tärviölle?

Katselin eilen, miten YLE 2 esitteli alueuutisissaan, että ennätysmnäiset
kuivuusjaksot jälleen kerran uhkaavat niin meillä kuin maailmalla hiipuvaa
elintarvikehuoltoamme -50% kastelulisätarpeineen. Jopa niin pahoin, että FAO
julisti ydinaavikoitumisen vesipulan ja ruuan katastrofin maailman
keskeiseksi haasteeksi tälle vuosisadalle! Pari päivää mm. ultrasalatun
sammakko ja matelijaekokatastrofin painikkeeksi.

Vaan mitä tekee maamme laajimmin vedättävä ydinala? Aivan oikein ostattaa
rahalla Ilmatieteenlaitokselta,. Ympäristöministeriöltä ja ties miltä
TKK:lta niin sairaansyvältä peilikuvalliset disinfot, ettei niitä voi edes
vitsinä pitää!Onko tosiaan niin, että ydinaavikoitumisen tappaessa meremme,
ilmastomme, sadantamme ja pian kaikki eläimet ympäriltämme ainoa vastaus
tähän luonnon ydinkritikkiin on vain ja ainoastaan silmitön valehtelu?
Luuleeko ydinalamme, että luonnon "Gaija" lukee näitä disinfomaksettuja
lehtiä ja lopettaa vääjäämättömäsi kumuloituvat ydintuhokasvut? Jos
ydinherramme luulevat NÄIN pääsevänsä pälkähästä ja vastuistaan niin
vesiperä! .. .Öö.. .nin tai tässä ydinaavikoitumisfaktassa toki
ydinaavikoitumispölyperä!((
 
On Fri, 4 Jul 2008 16:16:40 +0200, "François Guillet"
<guillet.francois@wanadoo.fr> wrote:

I'm looking for a mosfet better than 2SK544 which has high gain (27 dB at 100 Mhz),
low noise (NF 1.5 dB at 100 Mhz) and small transfer capacitance (0.035 pF).

Any idea ?
or a site where I could search for it on the basis of these topics ?

thanks

fu2 sec
Look at the NEC phemts... NE3509 is a pretty hot part. It will have
roughly 10 times the Gm of the 2SK thing.

John
 
On 4 jul, 16:16, "François Guillet" <guillet.franc...@wanadoo.fr>
wrote:
I'm looking for a mosfet better than 2SK544 which has high gain (27 dB at 100 Mhz),
low noise (NF 1.5 dB at 100 Mhz) and small transfer capacitance (0.035 pF).

Any idea ?
or a site where I could search for it on the basis of these topics ?

thanks

fu2 sec
Hello François,

I don't know what spec must be better (and the application), but you
may try www.infineon.com, descretes, RF discretes, etc. They have
various MOSFETS and SiGe transistors.

Best Regards,

Wim
PA3DJS
www.tetech.nl
don't forget to remove abc when direct replying
 
Norman Bollmann wrote:

I am new to the board design and stuff so please excuse me for asking
questions that may be selfevident... ;-) What I want to do is to connect an
Intel StrataFlash (or compatible) linear flash memory device (8MB) to an
Intel PXA26x processor.
Is this chip still available? I've heard the PXA was sold to another
company and Intel isn't producing it anymore.

Now I wonder if I should pay attention to the
impedance (some time ago I heard a weird fairy tale saying that everything
on board should be designed to 50 Ohms...?!) on the lines that connect the
devices or just design some connections no matter how and let a matter rest.
I don't know the details, but I know a company, who needed about one year
(2 man years) to design a board with a PXA, Flash and SDRAM. Many tries
were needed to do the routing right, adding buffers, measuring with
expensive logic analyzers and oscilloscopes etc. I hope you are working at
a big company, who has the knowledge and power to design such a board and
to do bug searching at 100 MHz, or faster, buses.

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de
 
"Michael A. Terrell" wrote:

Vermont towns vote to arrest Bush and Cheney | U.S. | ReutersWASHINGTON
(Reuters) - Voters in two Vermont towns on Tuesday approved a measure that
would instruct police to arrest President George W. Bush and Vice ...
www.reuters.com/article/domesticNews/idUSN0454699420080305 - 4 hours
ago - Similar pages

http://www.reuters.com/article/domesticNews/idUSN0454699420080305
I'd love to see Tony Blair on trial for 'waging aggressive war' and/or 'cimes
against humanity'. If it was good enough for the Germans at Nurnberg, it's
certainly good enough for him.

Graham
 
On Sat, 23 Aug 2008 01:35:21 +0100, Eeyore wrote:

"Michael A. Terrell" wrote:

Vermont towns vote to arrest Bush and Cheney | U.S. | ReutersWASHINGTON
(Reuters) - Voters in two Vermont towns on Tuesday approved a measure that
would instruct police to arrest President George W. Bush and Vice ...
www.reuters.com/article/domesticNews/idUSN0454699420080305 - 4 hours
ago - Similar pages

http://www.reuters.com/article/domesticNews/idUSN0454699420080305

I'd love to see Tony Blair on trial for 'waging aggressive war' and/or 'cimes
against humanity'. If it was good enough for the Germans at Nurnberg, it's
certainly good enough for him.

Hmmm... I wonder if we'll be lucky and it'll catch on? >:-

Cheers!
Rich
 
On Fri, 5 Sep 2008 09:22:49 -0600, "Not Really Me"
<scott@validatedQWERTYsoftware.XYZZY.com> put finger to keyboard and
composed:

Can anyone identify this part?
Fool that I might be, I'm trying to repair my Hitachi 36UX01S television. I
followed the troubleshooting charts for no Vertical drive and it tells me
that I should have 28V at the input to the drive chip. It has zero, so it
lists the drive chip, a diode (half wave rect off the transformer), or "E601
open" as the problem. E601 on the schematic is a rectangle with a circle on
each end and the value 1000. I don't recognize the symbol.

The kicker is that I can find it listed from parts suppliers on the net, but
it is $93, which strikes me as insane for a 2 pin part the size of a film
resistor.

Scott
The supply to the vertical output chip is usually taken from a winding
on the flyback transformer. The pulse is rectified by a diode and the
rail is protected by a low value fusible resistor, usually only a few
ohms. I'm guessing that the "DY" in the part number/description refers
to Deflection Yoke, "32V" may refer to the voltage rating (?) or the
size of the CRT in inches (?), and 110 may be the size of CRT in
degrees.

In fact the parts list in the service manual has three occurrences of
E601:

E601 BY00821 DY-32V 110 SVC
E601 AZ00102M PROTECTOR(CRXT491001)

and

E601 BY00821 Deflection Yoke Assy.

So it looks like two items have erroneously been given the same
circuit designation.

You should be looking for a protector device, ie the AZ00102M which
sells for $2.95, not a BY00821 deflection yoke costing $93. A low
value fusible resistor should do the job. I'd use circuits for
similarly sized CRTs (36") as a guide. The "1000" in the circuit
diagram may be a current rating in mA. You can use an ordinary 1A fuse
while troubleshooting to verify that the IC and yoke are OK.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
On Wed, 17 Sep 2008 18:30:33 -0500, krw <krw@att.bizzzzzzzzzz> wrote:

In article <1221678275.25833.1@proxy00.news.clara.net>, a@b.c
says...
Michael A. Terrell wrote:
Peto wrote:
On Wed 17 Sep08 05:04, Michael A. Terrell wrote in
news:OLOdnXQKjK5CHE3VnZ2dnUVZ_umdnZ2d@earthlink.com>:
Tim Perry wrote:
Please post a link to your recomended product.

http://www.gcelectronics.com/order/SubCatPDF/lubricants%2048-49.
pdf> Part No. 10-2610 Tunerlub is what I've used since the '60s.

I'm the OP. Do you smear Tunerlube on the threads or do you dunk the
plug into it (so the threads and centre connector are both covered in
Tunerlube?)


A very thin film, applied with a Q-tip is all that is needed.


Remember all its there to do is fill any airgaps to prevent moist air
getting in and starting corrosion. It takes almost no contact at all to
provide a good RF transmission: its when that contact is via a film of
oxide, that troubles start.

It takes one complete thread to make the RF seal, which was MT's
point about torquing the nut down, somewhere back there.

Tightening doesn't seal out air. The threads simply do not mate that
well. It does guarantee good electrical contact PRIOR to any oxidation
formation, however, which could mean years of good service.

Most cable companies now have/use fitting that incorporate a neoprene
o-ring in the base of the fitting's "cup".
 
In article <1e63d49lgv389o9io3dsu1mb22uvk1uamj@4ax.com>,
GoldIntermetallicEmbrittlement@youdontknowjack.org says...
On Wed, 17 Sep 2008 18:30:33 -0500, krw <krw@att.bizzzzzzzzzz> wrote:

In article <1221678275.25833.1@proxy00.news.clara.net>, a@b.c
says...
Michael A. Terrell wrote:
Peto wrote:
On Wed 17 Sep08 05:04, Michael A. Terrell wrote in
news:OLOdnXQKjK5CHE3VnZ2dnUVZ_umdnZ2d@earthlink.com>:
Tim Perry wrote:
Please post a link to your recomended product.

http://www.gcelectronics.com/order/SubCatPDF/lubricants%2048-49.
pdf> Part No. 10-2610 Tunerlub is what I've used since the '60s.

I'm the OP. Do you smear Tunerlube on the threads or do you dunk the
plug into it (so the threads and centre connector are both covered in
Tunerlube?)


A very thin film, applied with a Q-tip is all that is needed.


Remember all its there to do is fill any airgaps to prevent moist air
getting in and starting corrosion. It takes almost no contact at all to
provide a good RF transmission: its when that contact is via a film of
oxide, that troubles start.

It takes one complete thread to make the RF seal, which was MT's
point about torquing the nut down, somewhere back there.


Tightening doesn't seal out air. The threads simply do not mate that
well. It does guarantee good electrical contact PRIOR to any oxidation
formation, however, which could mean years of good service.
Tighten the nut enough and you will have contact. Cable companies
tighten the piss out of 'em to get a good RF seal.

Most cable companies now have/use fitting that incorporate a neoprene
o-ring in the base of the fitting's "cup".
Likely to keep moisture out.

--
Keith
 
On Thu, 18 Sep 2008 00:19:01 -0400, "Tim Perry"
<timperry@nospammeadelphia.net> wrote:

My outdoor applications mostly involve satellite dishes. I have a couple
adjacent to the NY throughway. One uses RG 11. Installed for 5 years and no
hint of problems. Most problem I have are with the small offset dishes
where the weather dome points down, drain holes get plugged and it fills
with water.
I used to use Scotch 23 self-vulcanizing tape for plug sealing.
Disadvantage - unscrewing the plug would entail cutting it free from
rubber mass.
Otherwise they were seals for life, also UV proof. Great tape to
weatherproof lots of stuff and cabling.

--
- Blarp the Enigmatic
 
On Sat, 20 Sep 2008 09:15:26 +0100, The Natural Philosopher <a@b.c>
wrote:

GoldIntermetallicEmbrittlement wrote:
On Thu, 18 Sep 2008 09:51:40 +0100, The Natural Philosopher <a@b.c
wrote:

The other problem is that such "layers" between a true metal to metal
contact makes for a very noisy electron stream, as well as the losses
presented by the higher resistance.
That's less releavant at RF..unless its wobbling in the breeze.


It is the same thing as "shot noise". electrons banging into things
along their path.

Shot noise is merely the noise inherent in a current because its made up
of discrete units of charge.

Got nothing to do with connectors.

Shot noise is that which is generated by a very simple thing, known as
friction, and it is inherent in ANY medium which electrons pass through,
including conductors.

It just happens to be far more prevalent in bulk mediums, like the old
carbon comp resistance mediums. It has more to do with imperfect crystal
lattices than anything else.
 

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