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Source For 72 or 75 Ohm Ladder Line ???
Had an E-Mail as to where to buy ladder line -- 72 or 75 ohm for antenna
feeder Understand it is scarce in the USA but may be available in the UK Sources anyone? thanks -- One Watt To steal ideas from one person is plagiarism; to steal from many is research. -- Comedian Steven Wright |
zip cord
"Micro MegaWatt" wrote in message news:uvHWc.131575$sh.83524@fed1read06... Had an E-Mail as to where to buy ladder line -- 72 or 75 ohm for antenna feeder Understand it is scarce in the USA but may be available in the UK Sources anyone? thanks -- One Watt To steal ideas from one person is plagiarism; to steal from many is research. -- Comedian Steven Wright |
"H. Adam Stevens, NQ5H" wrote in message ... zip cord ... Had an E-Mail as to where to buy ladder line -- 72 or 75 ohm for antenna feeder Understand it is scarce in the USA but may be available in the UK Sources anyone? thanks -- One Watt To steal ideas from one person is plagiarism; to steal from many is research. -- Comedian Steven Wright I think if you do the math, any benefit of using balanced 75 Ohm line- especially zip cord with a lossy vinyl dielectric will be lost- especially if not running at low VSWR conditions. My impressiion is that ladder line or balanced line is advantageous when the line is run at a high VSWR. The low matched loss then also means a low loss when run at high VSWR. Dale W4OP |
There's no such things as 72 or 75 ohm ladder line.
Ladder-line wires are spaced much too far apart and have mostly air insulation. They have impedances from 300 ohms and upwards. Expect to find very low impedances only with twin-wires embedded in a thick, circular or elliptical PVC sheath. Loss per unit length is quite high and suitable only for directly feeding, resonant, single-band, 1/2-wave dipoles at the lower frequencies. Zip-cord and twin speaker cables have Zo between 120 and 135 ohms. 16 to 20-gauge, colourless, speaker cables make a fair compromise between impedance, loss, SWR and small size. And exact impedance values are never critical at HF. --- Reg, G4FGQ |
Had an E-Mail as to where to buy ladder line -- 72 or 75 ohm for antenna feeder out of curiosity - why ? --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/29/2004 |
On Tue, 24 Aug 2004 06:36:26 -0700, "Micro MegaWatt"
wrote: Had an E-Mail as to where to buy ladder line -- 72 or 75 ohm for antenna feeder Getting a _balanced_ feeder at such low impedance levels is quite challenging, since a typical twisted pair (e.g.CAT5) would be in the 100-120 ohm range. You _might_ get something in the balanced 50-75 ohm range by getting a quad-pair cable and connecting the diagonally opposite conductors together. Thus, if the original pair had an impedance of 140-150 ohms, the two pars in the quad-pair cable would give 70-75 ohms. Paul OH3LWR |
Beldin 8210, I believe discontinued, was/is 75 ohm twin lead; and, it
was quite popular 30+ years ago. I haven't seen it in years. Last usage was in the 1950s on a 40 meter dipole connecting to a pair of 807s in P-P with a Shielded Faraday link to keep the TVI down. Does this bring back memories among the 'old timers'? W1MCE 50 years. Micro MegaWatt wrote: Had an E-Mail as to where to buy ladder line -- 72 or 75 ohm for antenna feeder Understand it is scarce in the USA but may be available in the UK Sources anyone? thanks -- One Watt To steal ideas from one person is plagiarism; to steal from many is research. -- Comedian Steven Wright |
"Micro MegaWatt" wrote in message news:uvHWc.131575$sh.83524@fed1read06... Had an E-Mail as to where to buy ladder line -- 72 or 75 ohm for antenna feeder Understand it is scarce in the USA but may be available in the UK Sources anyone? thanks -- One Watt It may not be an answer to your question, but, 4 lengths of 75 ohm coax connected in series and parallel would result in 75 ohms, balanced. Two 50 ohm coax cables "paralleled" could provide 100 ohms balanced with the center conductors used as the balanced line. Jerry |
450 ohm is often preferred for multiband antennas. But 72 ohm is available in
the US, can't remember if Davis RF, RadioWorks, or who that carries it. |
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"Jerry Martes" wrote in message news:8ZPWc.2585$9P.466@trnddc04... It may not be an answer to your question, but, 4 lengths of 75 ohm coax connected in series and parallel would result in 75 ohms, balanced. Two 50 ohm coax cables "paralleled" could provide 100 ohms balanced with the center conductors used as the balanced line. Jerry I posted the same answer in his 'found' thread - but I wasn't sure if my memory was in correct operating order. At least your post gives me hope that my memory hasn't completely left me. :-) I've used that scheme to make matching sections a few years back. 75-ohm cable comes in handy a lot of times. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/30/2004 |
Hal Yeah, the idea does work. I am using two 'side by side' RG223s right now to evaluate a dipole antenna I'm playing with. For my purpose, the 70 ohm dipole on the 100 ohm line is a good enough match. Jerry "Hal Rosser" wrote in message ... "Jerry Martes" wrote in message news:8ZPWc.2585$9P.466@trnddc04... It may not be an answer to your question, but, 4 lengths of 75 ohm coax connected in series and parallel would result in 75 ohms, balanced. Two 50 ohm coax cables "paralleled" could provide 100 ohms balanced with the center conductors used as the balanced line. Jerry I posted the same answer in his 'found' thread - but I wasn't sure if my memory was in correct operating order. At least your post gives me hope that my memory hasn't completely left me. :-) I've used that scheme to make matching sections a few years back. 75-ohm cable comes in handy a lot of times. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/30/2004 |
Hal
Yeah, the idea does work. I am using two 'side by side' RG223s right now to evaluate a dipole antenna I'm playing with. For my purpose, the 70 ohm dipole on the 100 ohm line is a good enough match. Jerry and as Roy pointed out in the other thread - the assembly will just facilitate the transmission of a balanced load - not 'cause it' to be balanced - But as you pointed out - using such an assembly aids in impedence matching schemes - and if the line happens to be balanced - it won't tip over . ;-) --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/29/2004 |
"Hal Rosser" wrote in message . .. Hal Yeah, the idea does work. I am using two 'side by side' RG223s right now to evaluate a dipole antenna I'm playing with. For my purpose, the 70 ohm dipole on the 100 ohm line is a good enough match. Jerry and as Roy pointed out in the other thread - the assembly will just facilitate the transmission of a balanced load - not 'cause it' to be balanced - But as you pointed out - using such an assembly aids in impedence matching schemes - and if the line happens to be balanced - it won't tip over . ;-) And -- Use of a balanced line to feed a ballanced antenna allows a balun to be located where it may be of a lesser disturbance when it is not a perfect balun. Jerry |
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