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Some use solid copper, some don't. Cost? Surely pure copper would have less loss and provide a long-life contact?
I may need to re-cable my house and its current 4 outlets. And I want the cable to last. Last lot installed in 1998 or 1999. Cold frosty winters, and sometimes snow.
Why? DTV has arrived and analogue ended and I cannot get one company's channels. FM is still fine, and all the other TV stations come through fine on their HDTV or SDTV channels. Luckily everything comes from one big tower on a big hill.
I think the existing cable may be a bit damp? All the cable outside is RG6 quad shield and is quite flexible and has drip loops.
Most of the network under the house is RG11 which does have a copper clad steel centre conductor. I was given a reel of it.
There are three antennas on the mast, an old VHF phased-array used for VHF TV (vertical), a big old Tandy/Antennacraft wide-band VHF Yagi now used for FM (horizontal), and a 24 element Yagi for UHF band IV. The on-mast combiner is a 4-input FUBA unit, from Germany.
Three of the wall plates have FM and TV coax sockets. One has a single socket, and it's unused, but has a 'shorting plug?' in it. Is it worth going to F-connectors on the wall plates?
I also use the mast for the ropes to hold a tuned random-wire AM antenna, a good neighbour's chimney is where it ends. The down lead for that is one side of some UV-stable twisted 300 ohm ribbon with the free side grounded to a ground-rod hammered in. It feeds the wide-audio-bandwidth mono AM stage in 'the tuna'.
There's a 4-way splitter under the house, too.
TIA
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Follow Ups:
I hope you mean a 75 ohm load, and not a true shorting plug.
If it is a shorting plug, this could be the problem, as it would black out certain frequencies due to the shorted stub line length.
Double-check kit and make sure it is a loading plug, not a shorting plug.
Jon Risch
Thanks John, I just unplugged it and the problems didn't resolve with it out. The back is a sealed white plastic casting.
I asked for such plugs at a DIY bits shop, I did mean for it to maintain the load the antenna system saw, as I'd been told that was important. This was way back so memory of my specific request then is not good.
IF it's a shorting plug, Wouldn't the problem have existed whenever I plugged it in?
Both single outlets are in the lounge/dining room (L-shaped) where the main audio only system is, the 2nd and was going to be rarely used to run a TV for special simulcasts on TV AND FM stereo. Hence the plug.
I AM going to check all the connections up on the mast first, before I pay for half a drum of new cable. And before I crawl around the tight crawl-space under the house. Spiders, builder's waste etc. * more below.
Should I put a load across the unused input in the FUBA combiner on the mast, too? I think they said no.
If you remember my post about TVI from my old rebuilt 'tunah' see the click URL below, you might be amused by the advice of a highly objectivist electronics mag here.
After receiving my detailed post, they suggested that my best solution was to run separate coax from the FM antenna down and around the house to separate outlets.?!?!
Apart from the sheer pleasure of clambering around under the house, they had ignored the likely problem of re-radiation to the TV antennas on the mast. I wrote back pointing that out, and that I'd been quite detailed about the array and the one mast, even about the crawl space being a great place to work. And, being objectivists they of course published my letter? Nope.
[One winter I might just get into my anti-fibre protective suit and put a big long-sided VHF (Band 1.5 long) rhombic up under the tiled roof, and put the band IV UHF TV antenna in there too. End of wet-coax and just two into to one for the combiner! One less antenna and less connection losses. Would require four longish safety planks though - as there's R6.0 worth of fibreglass up there, and it's rather hard to distingush ceiling boards from roof beams! Crunch, Tear, ..... Thudddd]
TIA, too.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Just measure the DC resistance from the center to ground, it should be the same as the coax impedance, I.e. 75 ohms for TV. The termination is just a resistor.
Rick
Copperweld is used for strength, cost and group delay. In my wayward youth I used to use it for 80m dipoles through the oak trees. Copper stretches, sags and breaks when the first small limb falls on it.
Most RF current is on the outer surface anyway and a core with perm forces that to happen at lower frequencies. I've mulled over using it for speaker cables, off-hand it seems like a terrible idea but I wonder if that's really the case? Anyway it works great for RF.
Rick
for home use.
This can't be good for RF, or any kind of long-term signal transmission performance, of any kind at AF or RF I'd think.
And, I doubt it's better than solid or braided copper on ANY kind of signal. Read the post that John Risch points too. Having read it it doesn't look very good for copper over steel now, does it?
Especially if it's easy to scrape the copper off. Steel is a shit-house conductor of signals. Yes?
Stronger? Is that really so important in cable that's going to be put in place and bent just once to do so?
It surely didn't become the way to go when copper prices rose sharply, did it, so when was the copper plated steel conductor introduced?
Anyone know?
In real/indexed terms in the late-mid 1970s say 1973. And again in the early 2000s.
Bullshit baffles lots of brains again, eh?!
:~)!
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
copper clad is just fine, same reason they use silver plate, rather than pure silver. Skin effect at RF frequencies and all that, you know.
For audio use there was a company which used that very same antenna wire for interconnects. I can't remember the name, but the antenna wire they used had a copper plated conduit type outer shield and a copper clad aluminum core,]. I believe the outer insulation was aluminum based also, but I can't really say.
The wire being relatively inexpensive didn't sound too bad, although that particularly company sold their IC's for something like $250 a pair. I'd seen clones on the market for about a hundred a pair. Sound was big, lush and warm almost perfect for the Audio Alchemy and Theta DACs so prevalent at the time.
Stu
Finally remembered the cable name: JPS
Stu
Yea, that sounds right Stu. I remember reading some of their ads in the past.
One of the problems with playing with cables is a hobbiest's inability to source small quantities of wire, let alone having it specially made. Even magnet wire is now insanely expensive. We had a struggling local electronics distributor go out of business but I didn't get the word in time and they had, at least at one time a pretty good selection. Sigh..
Regards, Rick
There was a company in the midwest: Fair Radio sales, IIRC, that had tons of this RF wire available, as well as tranformers and inductors and a host of surplus stuff. You could buy short lengths for very cheap.
However, If you are interested I do have some clones, available.....
Stu
Clones with the Al. Cores? I took a quick look at Fair Radio's web site but didn't see much in cables. Good nostalgia though, last thing I got from them was a tuning unit for an old transmitter for parts in the ninth grade.
I've been so pleased with just using open transmission lines made with magnet wire for interconnects cables that I'll probably continue. But I have considered trying 75ohm video cables and drivers, it seems like that would be pretty good for audio and easy at the receiving end at least.
Regards, Rick
See:
The skinny on RG-6 coaxial cables:
http://www.AudioAsylum.com/audio/cables/messages/25155.html
and
Easy coaxial based speaker cables (Belden 8213):
http://www.AudioAsylum.com/audio/cables/messages/7637.html
these talk about avoiding the coax with the steel cored wire.
It's worse with speaker cables than with IC's, but still noticeable as a false brightness, which can even border on harshness with some systems.
Jon Risch
Good article Jon, and I even agree which is why I've never tried them. But sometimes things audio work out differently than I think they will... However I have no problem continuing to give them a pass.
While not a TV fancier myself, I used to work in the same lab with both video and TV RF guys and I doubt if they would agree with you that "the levels of distortion that become visible are orders of magnitude higher than the levels of distortion that can be heard". The phrase most commonly heard, usually expressed in agony was 'group delay'. And even the RF guys fought it because even though the BW was far less than the baseband video they had to design incredibly tricky, high-Q filters to keep out of the adjacent channels. I was an ignorant, unbiased, uncaring guy working on avionics and so was felt to be a good 'man in the street' test case. The thing that really struck me was just how good clean NTSC video looked compared to the picture on my home TV and while I could see the problems they didn't seem very important. Not too surprisingly the video group leader was an audiophile...
Rick
FWIW, I did a stint as a video design engineer some years back. I was responsible for the design of an HDTV distribution amp, back when HDTV first was happening, and I also did a few other designs, among them, a video SCH phase meter module that fit into a rack mount mother chassis, etc.
So I do know what I am talking about, I myself SAW what the difference was between 8 bits and 10 bits of resolution (very little and only with training and having it pointed out to me) on a near-perfect NTSC signal generated from a live television camera (we're talking way past cable or DVD resolution of an NTSC signal) using a hand-built studio grade TV monitor. Past 10 bits, there wasn't ANYTHING visible as any sort of difference, even to trained and experienced eyes.
Did a similar experiment with HDTV signals several years ago when I visited an old friend from that industry, and while you would think that HDTV would respond to an even higher bit depth, in fact, it was not even certain if there was a noticeable difference between 8 and 10 bits. The resolution of an HDTV signal is in the bandwidth, not the bit depth, and the bit depth is what provides the dynamic range and literally "how far down you can see" capability.
Like many consumer items (such as how many Mega Pixels a digital camera has), having video units with 10 and 12 and even higher bit depth ADC's and DACs is mostly marketing BS. It looks better in the specs sheets, but doesn't provide a thing you can see. Similar to what goes on in audio, many of the 12 bit video ADC/DAC chips really only have 10 clean bits of resolution, and this is plenty.
So I stand by my statement, it was not made casually, but is based on real world experience and actual visual testing.
Jon Risch
"The resolution of an HDTV signal is in the bandwidth, not the bit depth"
That makes sense, my understanding is that the toughest distortion problems in video are usually temporal, but distortion none the less. Temporal that is while still a signal that is, they end up mapping to spatial problems when rendered.
I think audio suffers a similar fate but one harder to sift out with our senses and mind. They let us know something's wrong but not just what.
Guess that makes for an interesting hobby...
Regards, Rick
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