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RG-8 vs. RG-213?
Ok so I'm getting back active with my ham gear and while looking into a new
HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? TIA. :) Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ |
Ok so I'm getting back active with my ham gear and while looking into a new
HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? RG-213 has less loss per 100 ft than RG-8. Nothing too significant though, not at HF freq's at least. Check out: http://www.radio-ware.com/products/t...o/coaxloss.htm =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 73! de Andy KC2SSB - WPYI880 (GMRS) Beachwood, NJ USA! Grid FM29vw http://vhfradiobuff.tripod.com |
"VHFRadioBuff" wrote in message
... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? RG-213 has less loss per 100 ft than RG-8. Nothing too significant though, not at HF freq's at least. Check out: http://www.radio-ware.com/products/t...o/coaxloss.htm =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 73! de Andy KC2SSB - WPYI880 (GMRS) Beachwood, NJ USA! Grid FM29vw http://vhfradiobuff.tripod.com I think you are comparing RG-8X (the mini stuff) to RG-213. RG-8U has lower lose than 213. Sorry, I don't mean to be pedantic, but as a new ham myself, I found the various 8s confusing. 73 Paul AB0SI |
I had noticed the same thing, that RG-213 seemed to have very slightly more
loss per foot than RG-8 did. Somewhere I got a feeling that perhaps RG-213's strength was that it was longer lasting but even that doesn't make sense for several reasons. I've even noticed antenna kits that include RG-213 so maybe its just less expensive and they can make higher profits with RG-213 than they can with RG-8 at the expense of slightly higher loss? Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ " wrote in message news:w20Bb.461703$HS4.3603203@attbi_s01... "VHFRadioBuff" wrote in message ... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? RG-213 has less loss per 100 ft than RG-8. Nothing too significant though, not at HF freq's at least. Check out: http://www.radio-ware.com/products/t...o/coaxloss.htm =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 73! de Andy KC2SSB - WPYI880 (GMRS) Beachwood, NJ USA! Grid FM29vw http://vhfradiobuff.tripod.com I think you are comparing RG-8X (the mini stuff) to RG-213. RG-8U has lower lose than 213. Sorry, I don't mean to be pedantic, but as a new ham myself, I found the various 8s confusing. 73 Paul AB0SI |
RG-213 is also rated for somewhat higher power than RG-8.
Off the subject, but.... Last week I had an interesting QSO with a gentleman who runs nothing but hard line -- and SERIOUS hardline at that. His jumpers are LHR 600 -- he uses lower loss stuff (honest) for his runs. This includes the runs for his 160m and 80m antennas. Now, there is a person who does not like loss. Paul AB0SI "Jerry Bransford" wrote in message news:je0Bb.30145$Bk1.26174@fed1read05... I had noticed the same thing, that RG-213 seemed to have very slightly more loss per foot than RG-8 did. Somewhere I got a feeling that perhaps RG-213's strength was that it was longer lasting but even that doesn't make sense for several reasons. I've even noticed antenna kits that include RG-213 so maybe its just less expensive and they can make higher profits with RG-213 than they can with RG-8 at the expense of slightly higher loss? Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ " wrote in message news:w20Bb.461703$HS4.3603203@attbi_s01... "VHFRadioBuff" wrote in message ... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? RG-213 has less loss per 100 ft than RG-8. Nothing too significant though, not at HF freq's at least. Check out: http://www.radio-ware.com/products/t...o/coaxloss.htm =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 73! de Andy KC2SSB - WPYI880 (GMRS) Beachwood, NJ USA! Grid FM29vw http://vhfradiobuff.tripod.com I think you are comparing RG-8X (the mini stuff) to RG-213. RG-8U has lower lose than 213. Sorry, I don't mean to be pedantic, but as a new ham myself, I found the various 8s confusing. 73 Paul AB0SI |
Hi:
RG-8 used to be a military specification cable but the military dropped it in favor of a new specification called RG-213. They are very similar coaxes in general, but manufactures are free to make any cable they like and call it RG-8 so the quality and consistency can vary widely. Also RG-8 with foam a center insulator, and all the other variations are not nor never were MilSpec.That does not mean that all RG-8 cables are crap, but it could be and it depends on the manufactures idea of what kind of cable they want to sell. On the other hand RG-213 as a current MilSpec cable is a higher grade cable and is more consistent from manufacture to manufacture. My feeling is that if I'm going to go to all the work of installing a antenna, I want to use the best material I can. So I use RG-213. But my favorite coax is Davis RF Bury Flex, http://www.davisrf.com/ . It's a good coax that has low loss and a very tough jacket. I have 500 feet of it in my antenna system and so far I'm very happy. -- John Passaneau W3JXP State College Pa This mail is a natural product. The slight variations in spelling and grammar enhance its individual character and beauty and in no way are to be considered flaws or defects. "Jerry Bransford" wrote in message news:moUAb.29779$Bk1.25134@fed1read05... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? TIA. :) Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ |
THERE'S the answer I was looking for and it all now makes perfect sense.
Thank you very much John. Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ "John Passaneau" wrote in message ... Hi: RG-8 used to be a military specification cable but the military dropped it in favor of a new specification called RG-213. They are very similar coaxes in general, but manufactures are free to make any cable they like and call it RG-8 so the quality and consistency can vary widely. Also RG-8 with foam a center insulator, and all the other variations are not nor never were MilSpec.That does not mean that all RG-8 cables are crap, but it could be and it depends on the manufactures idea of what kind of cable they want to sell. On the other hand RG-213 as a current MilSpec cable is a higher grade cable and is more consistent from manufacture to manufacture. My feeling is that if I'm going to go to all the work of installing a antenna, I want to use the best material I can. So I use RG-213. But my favorite coax is Davis RF Bury Flex, http://www.davisrf.com/ . It's a good coax that has low loss and a very tough jacket. I have 500 feet of it in my antenna system and so far I'm very happy. -- John Passaneau W3JXP State College Pa This mail is a natural product. The slight variations in spelling and grammar enhance its individual character and beauty and in no way are to be considered flaws or defects. "Jerry Bransford" wrote in message news:moUAb.29779$Bk1.25134@fed1read05... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? TIA. :) Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ |
I think you are comparing RG-8X (the mini stuff) to RG-213. RG-8U has lower
lose than 213. According to the webpage that I referenced, the differences are as follows: RG-8X: 0.5dB at 1mhz 1.0 dB at 10mhz RG-213: 0.2dB at 1mhz 0.6db at 10mhz The original poster asked about RG-8. No reference to either X or U. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 73! de Andy KC2SSB - WPYI880 (GMRS) Beachwood, NJ USA! Grid FM29vw http://vhfradiobuff.tripod.com |
On Mon, 8 Dec 2003 07:28:21 -0800, "Jerry Bransford"
wrote: THERE'S the answer I was looking for and it all now makes perfect sense. Thank you very much John. Jerry Not to confuse/clarify matters more, but try the coax chart at http://thewireman.com/coaxp.html They have five kinds of rg-8 and four kinds of 213. The rg-8s all show less loss than the 213s. Guess it all depends on who's manufacturing the stuff. Bob k5qwg |
"VHFRadioBuff" wrote in message ... I think you are comparing RG-8X (the mini stuff) to RG-213. RG-8U has lower lose than 213. According to the webpage that I referenced, the differences are as follows: RG-8X: 0.5dB at 1mhz 1.0 dB at 10mhz RG-213: 0.2dB at 1mhz 0.6db at 10mhz The original poster asked about RG-8. No reference to either X or U. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- I think most would assume he meant for similarly sized cables. |
"Bury Flex" is ideal for jumpers of all kinds and long runs at lower
frequencies. Mac N8TT -- J. Mc Laughlin - Michigan USA Home: "John Passaneau" snip But my favorite coax is Davis RF Bury Flex, http://www.davisrf.com/ . It's a good coax that has low loss and a very tough jacket. I have 500 feet of it in my antenna system and so far I'm very happy. -- John Passaneau W3JXP State College Pa |
Actually, I believe that the RG-designations are no longer used by the
US military at all. Mil-C-17 now??--and I'm not sure any current ones are polyethylene (and not Teflon) dielectric. As John points out, RG numbers have been somewhat corrupted! But in general, "RG-213/U" and "RG-8/U" should both be solid-polyethylene dielectric cables with the same diameter and the same stranded inner conductor and single copper braid outer, and therefore should have the same attenuation per unit length, nominally. There will be minor variations from lot to lot, or larger variations if the coax was made poorly. "Reference Data for Radio Engineers" says of RG-213, "Formerly RG-8A/U." Foam dielectric cables, perhaps called "RG-213-type" or "RG-8-type," have lower loss for a given outer conductor diameter because the inner conductor is larger diameter and therefore has less resistance than with solid dielectric. (Similarly for Belden 9913-type cables.) But they may not be able to handle as much power, because the foam dielectric may be enough better a thermal insulator that the inner conductor still gets as hot or hotter at a given power, and that's the limitation. Also, you should be careful with bends in foam dielectric cables, because they can cause the center conductor to go off-center; that's especially bad if the cable's used at VHF/UHF. There's plenty more about the subject, but hope this helps a bit. Cheers, Tom "John Passaneau" wrote in message ... Hi: RG-8 used to be a military specification cable but the military dropped it in favor of a new specification called RG-213. They are very similar coaxes in general, but manufactures are free to make any cable they like and call it RG-8 so the quality and consistency can vary widely. Also RG-8 with foam a center insulator, and all the other variations are not nor never were MilSpec.That does not mean that all RG-8 cables are crap, but it could be and it depends on the manufactures idea of what kind of cable they want to sell. On the other hand RG-213 as a current MilSpec cable is a higher grade cable and is more consistent from manufacture to manufacture. My feeling is that if I'm going to go to all the work of installing a antenna, I want to use the best material I can. So I use RG-213. But my favorite coax is Davis RF Bury Flex, http://www.davisrf.com/ . It's a good coax that has low loss and a very tough jacket. I have 500 feet of it in my antenna system and so far I'm very happy. -- John Passaneau W3JXP State College Pa This mail is a natural product. The slight variations in spelling and grammar enhance its individual character and beauty and in no way are to be considered flaws or defects. "Jerry Bransford" wrote in message news:moUAb.29779$Bk1.25134@fed1read05... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? TIA. :) Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ |
Lots of great answers to my question, thanks all!
Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ "Tom Bruhns" wrote in message m... Actually, I believe that the RG-designations are no longer used by the US military at all. Mil-C-17 now??--and I'm not sure any current ones are polyethylene (and not Teflon) dielectric. As John points out, RG numbers have been somewhat corrupted! But in general, "RG-213/U" and "RG-8/U" should both be solid-polyethylene dielectric cables with the same diameter and the same stranded inner conductor and single copper braid outer, and therefore should have the same attenuation per unit length, nominally. There will be minor variations from lot to lot, or larger variations if the coax was made poorly. "Reference Data for Radio Engineers" says of RG-213, "Formerly RG-8A/U." Foam dielectric cables, perhaps called "RG-213-type" or "RG-8-type," have lower loss for a given outer conductor diameter because the inner conductor is larger diameter and therefore has less resistance than with solid dielectric. (Similarly for Belden 9913-type cables.) But they may not be able to handle as much power, because the foam dielectric may be enough better a thermal insulator that the inner conductor still gets as hot or hotter at a given power, and that's the limitation. Also, you should be careful with bends in foam dielectric cables, because they can cause the center conductor to go off-center; that's especially bad if the cable's used at VHF/UHF. There's plenty more about the subject, but hope this helps a bit. Cheers, Tom "John Passaneau" wrote in message ... Hi: RG-8 used to be a military specification cable but the military dropped it in favor of a new specification called RG-213. They are very similar coaxes in general, but manufactures are free to make any cable they like and call it RG-8 so the quality and consistency can vary widely. Also RG-8 with foam a center insulator, and all the other variations are not nor never were MilSpec.That does not mean that all RG-8 cables are crap, but it could be and it depends on the manufactures idea of what kind of cable they want to sell. On the other hand RG-213 as a current MilSpec cable is a higher grade cable and is more consistent from manufacture to manufacture. My feeling is that if I'm going to go to all the work of installing a antenna, I want to use the best material I can. So I use RG-213. But my favorite coax is Davis RF Bury Flex, http://www.davisrf.com/ . It's a good coax that has low loss and a very tough jacket. I have 500 feet of it in my antenna system and so far I'm very happy. -- John Passaneau W3JXP State College Pa This mail is a natural product. The slight variations in spelling and grammar enhance its individual character and beauty and in no way are to be considered flaws or defects. "Jerry Bransford" wrote in message news:moUAb.29779$Bk1.25134@fed1read05... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? TIA. :) Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ |
One interesting thing I noticed about RG-213...
It was installed in the KC, EC and RC-135's I worked on in the Air Force in the 80's. The planes were built in 1955 through about 1964 that I worked on. One day we had a transmit problem on our UHF radio (225-399.975 MHz AM). 10 Watts out, 10 Watts reflected. That's bad. We put a TDR on the line and saw an impedance discontinuity about 30 feet downstream from the transmitter. After pulling several floor panels and sending our only (tiny) female Tech Sargeant head-first down the floorboards, we had her disconnect the coax clamps and removed the coax. Cut it open and found the center conductor had migrated through the inner insulation allowing contact with the shield. The defective area was on a horizontal run. Not sure if gravity or vibration over 30 some years was at work or maybe fuel fumes deteriorated the stuff, softening it. I guess I suspected fumes because not long after that, we had a KC-135 blow up at Altus AFB in Oklahoma. Cause was determined to be a loose N-Connector at the antenna and when the radio keyed up there was a spark as the RF jumped the gap and boom. Cinders on the runway. Scott N0EDV "Tom Bruhns" wrote in message m... Actually, I believe that the RG-designations are no longer used by the US military at all. Mil-C-17 now??--and I'm not sure any current ones are polyethylene (and not Teflon) dielectric. As John points out, RG numbers have been somewhat corrupted! But in general, "RG-213/U" and "RG-8/U" should both be solid-polyethylene dielectric cables with the same diameter and the same stranded inner conductor and single copper braid outer, and therefore should have the same attenuation per unit length, nominally. There will be minor variations from lot to lot, or larger variations if the coax was made poorly. "Reference Data for Radio Engineers" says of RG-213, "Formerly RG-8A/U." Foam dielectric cables, perhaps called "RG-213-type" or "RG-8-type," have lower loss for a given outer conductor diameter because the inner conductor is larger diameter and therefore has less resistance than with solid dielectric. (Similarly for Belden 9913-type cables.) But they may not be able to handle as much power, because the foam dielectric may be enough better a thermal insulator that the inner conductor still gets as hot or hotter at a given power, and that's the limitation. Also, you should be careful with bends in foam dielectric cables, because they can cause the center conductor to go off-center; that's especially bad if the cable's used at VHF/UHF. There's plenty more about the subject, but hope this helps a bit. Cheers, Tom "John Passaneau" wrote in message ... Hi: RG-8 used to be a military specification cable but the military dropped it in favor of a new specification called RG-213. They are very similar coaxes in general, but manufactures are free to make any cable they like and call it RG-8 so the quality and consistency can vary widely. Also RG-8 with foam a center insulator, and all the other variations are not nor never were MilSpec.That does not mean that all RG-8 cables are crap, but it could be and it depends on the manufactures idea of what kind of cable they want to sell. On the other hand RG-213 as a current MilSpec cable is a higher grade cable and is more consistent from manufacture to manufacture. My feeling is that if I'm going to go to all the work of installing a antenna, I want to use the best material I can. So I use RG-213. But my favorite coax is Davis RF Bury Flex, http://www.davisrf.com/ . It's a good coax that has low loss and a very tough jacket. I have 500 feet of it in my antenna system and so far I'm very happy. -- John Passaneau W3JXP State College Pa This mail is a natural product. The slight variations in spelling and grammar enhance its individual character and beauty and in no way are to be considered flaws or defects. "Jerry Bransford" wrote in message news:moUAb.29779$Bk1.25134@fed1read05... Ok so I'm getting back active with my ham gear and while looking into a new HF antenna, discovered a new cable type being recommended here and there, RG-213. What is so much better about RG-213 than what I have used so much of over the years, RG-8? TIA. :) Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ |
OK, guys and gals, lets move smartly on into the 21st century. John, get a
current copy of MIL-C-17. Throw away your MIL-C-17E or earlier. Cables nomenclatured simply RG-nnn/U haven't been supported by the DOD system for well over 20 years. Only M17/+++-RGNNN nomenclatured cables are truly MIL-SPEC. See below. Jerry: Here is a very condensed history of coaxial cable nomenclature. Now, in the beginning, coax impedances resulted from standard size wires and tubing. RG-8/U was 52 ohms, which resulted from the dimensions which were quickly attainable in wire manufacturing in the 1930s. RG-8A/U was the same, except the jacket was made from a plastic which did not contaminate the dielectric through migration of the plasticizer. I recently had access to some old Federal Radio and Telephone Labs records which contained quite a discussion on dielectrics and jackets. Plastic technology was pretty primitive back then. So was wire manufacturing, and braid overlaying. In the 1960s all common coaxes were normalized to round number impedances and issued new nomenclature, RG-8/U at 52 ohms becoming RG-213/U at 50.0 ohms. RG-9/U became RG-214/U, and so on ad naseum. RG-11/U was already exactly 75 ohms, so it remained the same (and then moved on to M17/6-RG11). RG-13/U, on the other hand, the double shielded half inch 74 ohm coax became RG-216/U at 75 ohms. The new numbered cables were, for all practical purposes, the same as their predecessors, except for the impedance. 50.000 ohm network analyzers were now safe. Then in the 70s came cable TV and other wideband systems, which encountered performance problems due to unpredictable phase characteristics across the frequency range. This was found to be typically caused by repetitive mechanical disturbances in the cable construction. To fully qualify the cables, swept frequency performance measurements were added to MIL-C-17E, and the nomenclature changed yet again to the present M17/+++. Now, you don't see much of this 'new' M17/+++ stuff in ham use because it is another increment more expensive, and hams typically don't have requirements for wideband, predictable phase characteristics anyway. But, RG-213/U, which we had just gotten used to then became M17/163-00001, the cheaper non-swept direct equivalent, or M17/74-RG213 for the more expensive version swept from 50 MHz to 1 GHz. And cable bearing that nomenclature better meet the specifications of the current MIL-C-17. Now, just to be clear, there is no rule anywhere against anyone with cable manufacturing facilities making coax of any kind and quality (or even rope or water hose for that matter), and labeling it RG-8, or RG-213, or RG-(anything else). So asking about RG-8 (or RG-213) is like asking what the impedance of a wet noodle is. Finally, a quote from the MIL-C-17 page in the Times Fiber RF Transmission Line Handbook pretty well summarizes it, even better than the specification itself. Especially the last sentence: "Cables that are manufactured to MIL-C-17 specification no longer carry the RG designation. Instead, they are marked with an M17 designation. For example, RG-214 has been replaced by M17/75--RG214. In the future, any new cable design will be designated by a M17 number only. "In addition to the M17 number, all cables are marked with the manufacturer's name and government identification number, for example, 'M17/75-RG214, MIL-C-17, Times Fiber Communications, 68999, AA-3409.' Cables that are not marked with all this information are not qualified and there is no guarantee of their performance." -- Crazy George |
I think most would assume he meant for similarly sized cables.
Since I don't know the physical differences between RG-8, RG-8U, RG-8X and RG-213, I wouldn't know that he meant similarly sized cables. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 73! de Andy KC2SSB - WPYI880 (GMRS) Beachwood, NJ USA! Grid FM29vw http://vhfradiobuff.tripod.com |
Wow, you guys are great... thanks for the info Crazy George. I may be an
electronics whiz to my friends and neighbors but I feel like a beginner here. Thanks again! :) Jerry -- Jerry Bransford To email, remove 'me' from my email address KC6TAY, PP-ASEL See the Geezer Jeep at http://members.cox.net/jerrypb/ "Crazy George" wrote in message ... OK, guys and gals, lets move smartly on into the 21st century. John, get a current copy of MIL-C-17. Throw away your MIL-C-17E or earlier. Cables nomenclatured simply RG-nnn/U haven't been supported by the DOD system for well over 20 years. Only M17/+++-RGNNN nomenclatured cables are truly MIL-SPEC. See below. Jerry: Here is a very condensed history of coaxial cable nomenclature. Now, in the beginning, coax impedances resulted from standard size wires and tubing. RG-8/U was 52 ohms, which resulted from the dimensions which were quickly attainable in wire manufacturing in the 1930s. RG-8A/U was the same, except the jacket was made from a plastic which did not contaminate the dielectric through migration of the plasticizer. I recently had access to some old Federal Radio and Telephone Labs records which contained quite a discussion on dielectrics and jackets. Plastic technology was pretty primitive back then. So was wire manufacturing, and braid overlaying. In the 1960s all common coaxes were normalized to round number impedances and issued new nomenclature, RG-8/U at 52 ohms becoming RG-213/U at 50.0 ohms. RG-9/U became RG-214/U, and so on ad naseum. RG-11/U was already exactly 75 ohms, so it remained the same (and then moved on to M17/6-RG11). RG-13/U, on the other hand, the double shielded half inch 74 ohm coax became RG-216/U at 75 ohms. The new numbered cables were, for all practical purposes, the same as their predecessors, except for the impedance. 50.000 ohm network analyzers were now safe. Then in the 70s came cable TV and other wideband systems, which encountered performance problems due to unpredictable phase characteristics across the frequency range. This was found to be typically caused by repetitive mechanical disturbances in the cable construction. To fully qualify the cables, swept frequency performance measurements were added to MIL-C-17E, and the nomenclature changed yet again to the present M17/+++. Now, you don't see much of this 'new' M17/+++ stuff in ham use because it is another increment more expensive, and hams typically don't have requirements for wideband, predictable phase characteristics anyway. But, RG-213/U, which we had just gotten used to then became M17/163-00001, the cheaper non-swept direct equivalent, or M17/74-RG213 for the more expensive version swept from 50 MHz to 1 GHz. And cable bearing that nomenclature better meet the specifications of the current MIL-C-17. Now, just to be clear, there is no rule anywhere against anyone with cable manufacturing facilities making coax of any kind and quality (or even rope or water hose for that matter), and labeling it RG-8, or RG-213, or RG-(anything else). So asking about RG-8 (or RG-213) is like asking what the impedance of a wet noodle is. Finally, a quote from the MIL-C-17 page in the Times Fiber RF Transmission Line Handbook pretty well summarizes it, even better than the specification itself. Especially the last sentence: "Cables that are manufactured to MIL-C-17 specification no longer carry the RG designation. Instead, they are marked with an M17 designation. For example, RG-214 has been replaced by M17/75--RG214. In the future, any new cable design will be designated by a M17 number only. "In addition to the M17 number, all cables are marked with the manufacturer's name and government identification number, for example, 'M17/75-RG214, MIL-C-17, Times Fiber Communications, 68999, AA-3409.' Cables that are not marked with all this information are not qualified and there is no guarantee of their performance." -- Crazy George |
Howdy,
I personally like RG-214 but it's very expensive, at least as far as I'm concerned, I only have a small amount I have gotten at hamfests. 75-Ohm TV hardline is available from your TV cable company as reel ends usually for free. The last I got had 134 feet left on the reel and was insulated and 1/2 inch in diameter. But there is a price problem with connectors. Many hams fabricate their own. TV cable companies don't give connectors away. 73 de Jack, K9CUN |
"VHFRadioBuff" wrote in message ... I think most would assume he meant for similarly sized cables. Since I don't know the physical differences between RG-8, RG-8U, RG-8X and RG-213, I wouldn't know that he meant similarly sized cables. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 73! de Andy KC2SSB - WPYI880 (GMRS) Beachwood, NJ USA! Grid FM29vw http://vhfradiobuff.tripod.com This is what I like about Andy...VHF Radio goof. He knows nothing but that don't stop him from giving his 'advise'. A MAJOR factor for using 213 is it is Mil-spec. And it sure isn't new cable. Dan/W4NTI |
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