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Author Topic: RF Connector Types (UHF,N,BNC)  (Read 1722 times)
W8JI
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« Reply #15 on: September 19, 2005, 06:53:19 PM »

Contact resistance is a non-issue with connectors like these.

Gold connectors aren't generally even real gold anyway. They are largely just a con to get money from people who are not technically inclined.

The loss of a nickel plated PL259/SO239 combination is virtually immeasurable without special test gear below 50 MHz, and can ecven be ignored on two meters unless you have a bunch of connectors in line.

I use UHF types for stuff up to 200MHz or so. BNC's for test equipment. N's for upper UHF systems.

I'd never use an N or BNC at high power on HF.  

73 Tom
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X-WB1AUW
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« Reply #16 on: September 19, 2005, 08:23:24 PM »

When it comes to true Hi Fi audio systems, cabling changes the layering of details, as well as the sound.

One must experiment with not only the cabling, but also room acoustics to hear the changes.

It is not for the faint of heart.

10K turntable, 2k cartridge, 2k tone arms, 5k phono amps, 6-10K preamps, 10K amps, 10K speakers, not too many people spend that for audio.  But, unfortunately, at that level, one hears BIG changes when changing AC cords, interconnects, and speaker cables.

Contempt prior to investigation, does a lot of people in.

Bob

PS: changing from a Bugle Boy 12AX7a to a triple mica, black plate, Sylvania 5751, or Siemens 12AX7a make huge changes in sound.  Same for different 6SN7s, 6DJ8s, etc.
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KA0GKT
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« Reply #17 on: September 20, 2005, 12:43:17 AM »

I agree, having the proper load for a magnetic phono cartrige is important sonically, however when it comes to the kind of speaker line runs found in the typical home, gold plated connectors and "Monster Cable"(r) aren't of audible difference from 18-2 zip cord.

The skin depth at 20 HZ is 18.34 INCHES in oxygen free copper.  At 20 KHz, it is .573".

Since FM stereo radio cuts everything off above 14KHz to protect the stereo pilot and the L-R subcarrier, and little is recorded above 20 KHz in Vinyl and Digital recordings, vinyl usually rolled off around 60 HZ, however some direct to disc and digital to disc recordings recorded frequencies down to a few HZ (Like my Telarc recording of the 1812 overature with real 18th century canon shots) and the usual published specifications for high fidelity audio equipment quotes a 20-20,000 Hz response, those figures are valid.

Having an infinite number of strands in stranded cable makes no difference at these frequencies an un insulated bundle of wires act as one when it comes to skin effect, that is why the individual wires in litz wire are insulated from each other.

The difference, other than power handling capability for larger gauges of wire is zip, zilch, nothing, nada.  If you switch to solid silver wire, you gain but a few micro-inches in skin depth advantage at these frequencies.  By going to nickle wire, the skin depth is considerable lower, however the additional resistance comes in and I/R losses increase...not that anyone in a blind-blind test could tell the difference.  There might be an improvement(although still inaudable to anyone but the family dog) if you don't use twisted pair for your speaker runs and run one wire clockwise around the room ane the other counter clockwise around the room to each speaker.  In this way you eliminate much of the stray capacitance found in twisted pair which can ruin the damping in systems with DC coupled amplifiers.

Real world, other than impedance matching on preamplifier inputs, specially high gain inputs like magnetic phono pick-ups and those times when a tape head is directly connected into the stereo pre-amp, there is very little that the expensive audio wires do for you other than lighten your pocketbook.  It's the difference between psycoaccoustics and Physics.

Now, if someone feels more fulfilled because they spend more money on their interconnection wiring on the home stereo, if they sleep better at night knowing that they have the ne-plus-ultra wire between their sansui receiver and their speakers, fine.  Lots of people spend money just to feel good, and the manufacturers deserve to reap the benefits oftheir PR campaign.  I'll just sit in my living room and enjoy the old fashioned warm tones of my RT Bozak 201B speakers driven by my H.H.Scott preamp and Dynaco Stereo 70s.  Yes, the tonality is probably colored by todays standards, but it sounds good to my damaged (through 30 years in Rock & Roll Radioas an engineer) hearing.  Those who buy in to the Psyco end of Psyco Accoustics can spend their money their way...I'll spend mine my way...OBTW, I use 12-2 zip cord between the dynacos' 16-ohm taps and the Bozaks...lower THD at the 16-ohm setting...I'm a little Psyco myself. :-D

73 DE KAØGKT/7

--Steve
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AA4PB
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« Reply #18 on: September 20, 2005, 05:41:31 AM »

one hears BIG changes when changing AC cords
--------------------------------------------
This comes up on the audio news groups from time to time. I read of people spending $100 or more for a 6-foot AC cord to make their systems sound better. I have to ask, with probably several hundred miles of copper and aluminum wire between the generating plant and my audio amp why in the world would the last 6-feet make any significant difference? Only to the guy who sells 50 cents worth of wire for $100.

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WB2WIK
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« Reply #19 on: September 20, 2005, 08:01:33 AM »

>RE: RF Connector Types (UHF,N,BNC)  Reply  
by AA4PB on September 20, 2005  Mail this to a friend!  
one hears BIG changes when changing AC cords
--------------------------------------------
This comes up on the audio news groups from time to time. I read of people spending $100 or more for a 6-foot AC cord to make their systems sound better. I have to ask, with probably several hundred miles of copper and aluminum wire between the generating plant and my audio amp why in the world would the last 6-feet make any significant difference? Only to the guy who sells 50 cents worth of wire for $100.<

::I thought the same thing the first time I saw an advertisement for special AC power cords for audiophiles.  What difference can the last few feet make when the rest of the line is completely uncontrolled?  This is nutty.
 
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W3JJH
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« Reply #20 on: September 20, 2005, 12:22:01 PM »

Back in the early '80s when I was VP of Engineering at JBL, we evaluated various types of cable using double-blind A/B testing.  We were always looking for any real way to improve product performance and quality.  The only wire that could occassionally be indentified by listeners as "superior" was the AWG 18 stranded hookup wire we used inside our inexpensive systems for interconnection between crossover networks and drivers--and the statistical correlation was very poor with that wire.  None other wires could be reliably indentified as sounding different from each other.  Oxygen-free, litz wire, you name it; we tried it.

This is consistent with other results performed by our colleagues at other audio companies and several universities.  I'm unawared of any data in the peer-reviewed literature that demonstates any contrary finding.

These pyschoacoutics test are also consistent with electronic measurement.  If the loop resistance of the wire was sufficiently low  to aviod introducing significant system loss or detuning the low-frequency damping of one of the system drivers, then we could not measure any change in the signal at the loudspeaker end of the wire.  We couldn't find additional distortion, even with a custom spectrum analyzer that could spot signal components 140 dB below the carrier.

Changes in semiconductors or tubes in the system were often readily apparent to all listeners, but these changes always coincided with measureable changes in distortion products because of differences in device nonlinearities.

Similarly, gold-plated connectors are not always a good idea.  One of the worst intermittent noise source I ever had to troubleshoot was caused by a gold-plated connector.  I was repairing a tape recorder that had incredibly noise playback on one channel.  I replaced all the resistors in the signal path.  I replaced the tubes.  I replaced all the caps in the signal path.  Finally, when I was reconnecting the pc board for the umpteenth time, I noticed that one of the pins that I was slipping on to a turret on the board was not the same as the others.  It was gold-plated, and the other pins and the turrets were silvered.  Gold and silver are dissimilar metals, and the resulting intermittent battery (Ag + Au + tarnish + moisture in the air) was being amplified.  The offending pin was on the input lead from the playback head.

Dissimilar metals can also form diodes, and the resulting nonlinearity at the connection can cause distortion in addition to noise.

Meanwhile, I'll stick to UHF connectors below 300 MHz and below 1 kW average power.  Plain UHF connectors.
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X-WB1AUW
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« Reply #21 on: September 20, 2005, 01:52:51 PM »

I was fortunate to befriend a fellow, Mila Nestorovic, who worked for Sylvania, Sylvania radio.  From there he went to a company called McIntosh.  When Mac went solid state, Mila left, he was one of their main designers.  Mila did consulting and eventually made his own tubed amps and speakers.

For a few years, I would fly to Las Vegas to help him during the annual Hi Fi trade show.

As a result of knowing Mila and going to the trades shows, I met a variety of people within the industry.

I got the opportunity to try different products and talk a lot with Mila.  When I encountered something that seemed to improve my system, I�d send it to him.  Many times what we changed didn�t make any common sense, but we both heard the difference.  

It is of no conscience to me if anyone dismiss cabling changing the sound of true Hi Fi systems.  Just as it is of no consequence is people don�t believe that EU can be worked by short path on 80 meters, gray line long path, and at times by aiming due north, north west, and over South America.

Bob
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WB2WIK
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« Reply #22 on: September 20, 2005, 03:44:33 PM »

>RE: RF Connector Types (UHF,N,BNC)  Reply  
by W3JJH on September 20, 2005  Mail this to a friend!  
Back in the early '80s when I was VP of Engineering at JBL, we evaluated various types of cable using double-blind A/B testing. We were always looking for any real way to improve product performance and quality. The only wire that could occassionally be indentified by listeners as "superior" was the AWG 18 stranded hookup wire we used inside our inexpensive systems for interconnection between crossover networks and drivers--and the statistical correlation was very poor with that wire. None other wires could be reliably indentified as sounding different from each other. Oxygen-free, litz wire, you name it; we tried it.<

::Cool stuff.  Did you work with Ron Means, N6TZU?  In the 80's and some of the 90's Ron was President of JBL.  Since they're down the street from me, I've been there a lot, as have most of the hams in the area...73 de Steve WB2WIK/6  
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VE7ALQ
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« Reply #23 on: September 20, 2005, 04:19:21 PM »

Yes, Audiophiles seem to like a number of strange things.  Namely Vacuum Tubes are supposed to be superior to Solid State, to the extent that an 866 mercury vapour rectifier tube is thought to be superior to a silicon diode?!  They also hate capacitors in general and electrolytic capacitors in particular.I never did find out what benefit "oxygen-free copper" conveyed; all that happened when I asked was that I was looked at as an alien from Mars!  One thing I have in common with the Audiophiles is that I like gold (plated) connectors.  In my case, it is for appearance, as well as corrosion-resistance.  I agree that silver connectors might be a better choice outside in the elements where nobody can admire my gold ones(!)
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N0TONE
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« Reply #24 on: September 20, 2005, 04:51:07 PM »

Using a Hewlett-Packard Network Analyzer, I verified that a UHF connector is electrically invisible to about 2 GHZ, despite claims to the contrary.  A new BNC connector and an N connector have identical performance, as they exhibit the same interface dimensions.  Both N and BNC, when installed correctly, are useful to 18 GHz.  Far better than a UHF connector, but only microwave enthusiasts need to care.

The typical UHF connector is more rugged than the typical N connector, therefore my ham station purely uses UHF connectors.

The type N connector makes an "instrumentation grade" repeatable connection, and UHF does not, therefore you won't find UHF connectors in a cal lab.  But again, as hams, why should we care?

UHF is still the standard connector used in AM broadcast stations of 5kW and less.

AM
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W3JJH
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« Reply #25 on: September 20, 2005, 08:53:16 PM »

WB2WIK DE W3JJH:

Ron was VP of JBL Pro Marketing when I was with the company.  Neither one of us had ham tickets back then, although I had a First Phone that was in the process of turning into a General Radio Telephone commercial license.  Back then, Ron lived in Westlake and I lived in TO.

73 DE W3JJH
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W3JJH
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« Reply #26 on: September 20, 2005, 09:26:29 PM »

OK, here's the story behind oxygen-free copper.  Meter rectifiers are sometimes made with copper oxide.  Since you can make a rectifier out of copper oxide, the presence of copper oxide in a wire will make it non-linear.

Yeah, right.

Of course, the copper oxide is bypassed (read, shorted out) by the bulk of copper in the wire and the nonlinearities are typically over 150 dB down, but some golden ears types believe that  they can hear a signal below the threshold of audibility while it is being masked by a signal above the threshold of pain.  Sort of like claiming to hear the wings flapping on a duck 1/4 mile away while the guy standing next to you in the blind is firing his 12 ga.

Yeah, right.

There's all sorts of weird stories that circulate among audiophiles with no real background in music or engineering.  Occasionally, one of them will notice something that's really happening, but the proffered explanation is often nonsense.  For example, the whole tubes vs. transistors thing.  It was rigorously demonstrated by Daugherty and Greiner in the late '60s and confirmed by work by Otala in the '70s that the "transistor" sound is simply transient intermodulation (TIM) distortion caused by inadequate gain-bandwidth product.  Because it is easier to build direct-couple amplifiers with transistors, it's easier to fall into the TIM trap with them.  The ac-coupling in most tube circuits adds low frequency poles that force the designer to pay more attention to feedback loop design and thereby avoid TIM.  But it's possible to build a tube amp with TIM, and it will sound just as bad as a poorly engineered solid state amp.  

BTW, one of the differences that I've noted between the audio portions of most Kenwood and some TenTec ham gear and brand I and brand Y is the use of ICs with higher open-loop bandwidth (and less susceptibity to TIM).

The one thing that the golden ears have managed to get right is the stuff about capacitors.  The dielectric constant of the any real world capacitor is nonlinear with respect to applied potential.  Some ceramic caps are so bad that almost anyone will immediately notice the difference.  Tantalum caps are pretty funky also.  Polycarbonate and Polypropylene produce the least distortion.  In very high quality audio gear it is not uncommon to see electrolytic coupling capacitors dc biased to reduce the percentage variation in potential across the resulting from the audio and bypassed with a polypropylene cap to reduce HF nonlinearities.
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KA0GKT
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« Reply #27 on: September 20, 2005, 10:05:03 PM »

NOTONE writes:
"Using a Hewlett-Packard Network Analyzer, I verified that a UHF connector is electrically invisible to about 2 GHZ, despite claims to the contrary."

Interesting.  I performed the same experiment using an Advantest network analyzer and the UHF connector got really bad above 300 MHz.  Perhaps it was the SO-239 that was the culpret...but then they're kind of useless without each other.

NOTONE writes:
"The typical UHF connector is more rugged than the typical N connector, therefore my ham station purely uses UHF connectors."

Perhaps, however I have broken my share of UHF connectors, had the darned things come unscrewed in situations where vibration is a problem and had SO-239 fingers spread and make poor contact, get hot and smell.

NOTONE writes:
"UHF is still the standard connector used in AM broadcast stations of 5kW and less."

Interesting, the last time I found a UHF connector in an AM broadcast site was nearly 20 years ago...and it wasn't being used any longer.  It was on a sample loop mounted on the side of an AM tower in a 2-tower DA.  The Engineer who was retiring told me he had replaced the old sample loops some 15 years previous with torroid sample transformers.  The transformers had...guess what?  Type "N" connectors.

Some ten years before that, I changed from indirect to direct measurment on a 500 watt 1340 station.  The Potomaic remote ammeter used Type "N" connectors and a D-sub for remote control interface.  This was a relatively old transmitter site and there was only one UHF connector...on the Low Band VHF FM transceiver's antenna connection.

I have been engineer for AM stations from 250-watts to 50 KW.  Other than the sample loops, I remember an old Gates 250-watt sitting, disconnected, in the back room.  811 Modulators and 813 finals, and cold for over 25 years.  The owner wanted it as a back-up transmitter, so I hauled it into place in the transmitter room, installed an RF rocker relay in the old Gates cabinet because ther was more room there and replaced the SO-239 with a 50-Ohm type "N" Female.

Many older AM transmitters had feedthrough insulators for the RF terminals.  The last 4 under 5-KW AM transmitters which I have installed all had EIA flange and bullet RF connections, as have the 10, 25 and 50 KW transmitters (Obviously larger cable and flanges for the higher power levels.)

73 DE KAØGKT/7

--Steve


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WB2WIK
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« Reply #28 on: September 21, 2005, 09:19:04 AM »

>RE: RF Connector Types (UHF,N,BNC)  Reply  
by W3JJH on September 20, 2005  Mail this to a friend!  
WB2WIK DE W3JJH:

Ron was VP of JBL Pro Marketing when I was with the company. Neither one of us had ham tickets back then, although I had a First Phone that was in the process of turning into a General Radio Telephone commercial license. Back then, Ron lived in Westlake and I lived in TO.

73 DE W3JJH<

::Ron went on to become President of JBL, and held that position through the late 80s and early 90s.  I kind of lost track of him, and he relocated to northern CA for a while, but now I see he's "back" in the Santa Rosa Valley (Ventura County, on the hill up above Camarillo) so I ought to look him up again.  Nice guy, we worked a couple of Field Days together.  73 de WB2WIK/6  
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WB2WIK
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« Reply #29 on: September 21, 2005, 09:23:57 AM »

>RE: RF Connector Types (UHF,N,BNC)  Reply  
by W3JJH on September 20, 2005  Mail this to a friend!  
OK, here's the story behind oxygen-free copper. Meter rectifiers are sometimes made with copper oxide. Since you can make a rectifier out of copper oxide, the presence of copper oxide in a wire will make it non-linear.<

::I've heard the term "OFHC" copper for many years.  "Oxygen free, high conductivity" copper.  I often wondered if there's any other kind.  I guess it remains oxygen free if it's immersed in Fluorinert or sealed in dry nitrogen, or sealed in a vacuum.  If it's out here in the world where we breathe, how does it remain "oxygen free?"  Makes no sense.

::An audiophile neighbor of mine was using Monster Cable (really large stuff) for his speakers, claiming the smaller gauge wouldn't handle the peak power, restricted the bandwidth, added distortion, and caused warts.  I believed the warts part, but the rest seemed ridiculous, especially since my 700Wpk system drives six speakers using #18GA stranded copper lamp cord and sounds better than his system to everybody.  But I'm watching out for warts.

WB2WIK/6  
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