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Coax recomendations
I am putting up a second tower , but it will be about 200feet from the shack
and about 70feet high. What coax is recommended to reduce loss to a minimum,and to feed a multiband beam with a 2kw amplifier. Hard line excepted due to cost. Regards Ross ZL1WN |
Coax recomendations
Hi Ross
300ft of RG213 maybe? Thats about 3.5dB loss at 30MHz assuming a 1.5:1 VSWR. At 14MHz its about 2.4dB loss. LMR400 at about the same diameter as RG213 is just under half the loss. Its also cheaper than RG213 but a bit harder to terminate into connectors. RG6 may also be usable and much cheaper (being TV/CATV coax) as it has only slightly more loss than RG213. Its 75 ohms though if thats an issue. (http://www.ocarc.ca/coax.htm) There will be a much lower loss if you use open wire feeder... You could no doubt use broadband baluns at each end to change back to coax. You could also make your own feeder probably much cheaper than using coax. I seriously dont think the line loss figures in the coax mentioned above are important for HF work. You are of course losing half your power at higher freqs. Cheers Bob W5/VK2YQA Ross Biggar wrote: I am putting up a second tower , but it will be about 200feet from the shack and about 70feet high. What coax is recommended to reduce loss to a minimum,and to feed a multiband beam with a 2kw amplifier. Hard line excepted due to cost. Regards Ross ZL1WN |
Coax recomendations
for which band?
|
Coax recomendations
I would recommend you take a look at Davis RF "BuryFlex" 9914. It is very
nearly the exact same loss per 100ft (within a couple tenths of a db) as LMR400 and/or 9913. It can be directly buried in the soil with no other provisions needed. It has an abrasion resistant non-contaminating jacket that has a warranted 20 year service life. It is also quite affordable at about $.60/ft. It is very flexible and indeed is fine even as rotator loops. I use it on all bands I run from HF thru 6M and 2M. It uses standard UHF or N connectors as well. Loss per 100ft at 400MHZ is 2.9db Check it out here.... 1. http://www.davisrf.com/ham1/coax.htm#buryflex -- Charlie "Ross Biggar" wrote in message ... I am putting up a second tower , but it will be about 200feet from the shack and about 70feet high. What coax is recommended to reduce loss to a minimum,and to feed a multiband beam with a 2kw amplifier. Hard line excepted due to cost. Regards Ross ZL1WN |
Coax recomendations
Yes that is a good question, I forgot to mention.
primary use will be on 20m, Thanks Ross "F8BOE" wrote in message ... for which band? |
Coax recomendations
Ross Biggar wrote:
I am putting up a second tower , but it will be about 200feet from the shack and about 70feet high. What coax is recommended to reduce loss to a minimum,and to feed a multiband beam with a 2kw amplifier. Hard line excepted due to cost. At HF and with low SWR, anything of RG213 size or larger should be OK as regards cable heating... but in reality you are not aiming to reduce the losses "to a minimum". You're actually making a three-way balance between losses, availability and cost. (Re availability and cost: people in the USA should note that Ross is in New Zealand. Coax is heavy, and international shipping costs are horrendous, so Ross has a much narrower range of options than you do.) "Cost" will also include the cost of repairs and replacement - and this can be a big consideration with a long run of cable because it's extremely important to keep the jacket free from any damage where water can get in. Capillary action can suck water into the braid over very long distances from the initial location of the damage, and corrosion of the braid can drastically increase the losses. So even minor physical damage can have big electrical consequences, and can effectively destroy a long section of line. I'm in a similar situation here, with a new tower and LF verticals. The cables will have to run a long distance over rough land covered with thorns and sharp stones... and it's usually wet too. For all those reasons, I am not going to use braided coax, but will try *very very* hard to locate some surplus hardline. The advantage of foam-filled hardline is that it's largely immune to minor damage from the outside. If the plastic jacket is cut or even removed completely, it doesn't matter at all because you still have solid copper to keep the water out. And even if you take a slice off the copper sheath with the mower (BTDT), water will not migrate along the inside because the closed-cell foam is firmly bonded to the inside surface of the sheath. You certainly don't have to buy hardline at new prices - though even there you might be pleasantly surprised (for example there's an outlet in VK-land whose prices are very reasonable). Your options will depend on what's available in ZL, and to find out you may have to tap a few contacts. For example, in the UK there's a lot of surplus hardline is coming out of cellular, broadcast and other VHF/UHF/microwave sites as they are being upgraded to the next generation. A lot fo this goes straight to scrap copper, but some gets diverted into the surplus market. Short lengths appear quite often at radio flea markets ("rallies"), and if you ask, the guys generally have much longer lengths back home at much lower prices. (In the USA they also have aluminium-jacketed cable TV hardline. It doesn't exist in the UK, but if it's relevant in ZL there are people in this newsgroup who know about it.) Crazy as it may sound, the larger sizes of hardline can be cheaper on the surplus market than the more popular "half-inch" size. The larger cables are more difficult to transport and less convenient to handle, so there are fewer buyers and that drives the price down. Even so, 2-3 people can handle the lengths you are considering, and in a fixed installation you only have to lay it once... and then you really could say you've reduced the losses "to a minimum". -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Coax recomendations
Charlie wrote:
I would recommend you take a look at Davis RF "BuryFlex" 9914. It is very nearly the exact same loss per 100ft (within a couple tenths of a db) as LMR400 and/or 9913. It can be directly buried in the soil with no other provisions needed. It has an abrasion resistant non-contaminating jacket that has a warranted 20 year service life. It is also quite affordable at about $.60/ft. It is very flexible and indeed is fine even as rotator loops. I use it on all bands I run from HF thru 6M and 2M. It uses standard UHF or N connectors as well. Loss per 100ft at 400MHZ is 2.9db Check it out here.... 1. http://www.davisrf.com/ham1/coax.htm#buryflex I've got some of that which I purchased new, and did some extensive tests on it with a network analyzer. The loss varies all over the map depending on how you coil, bend, or flex the cable, and I never saw loss anywhere near as low as the spec says. A typical value at 400 MHz was more like 5 - 5.5 dB/100 ft. Glad you're happy with it. Roy Lewallen, W7EL |
Coax recomendations
Sounds like a flawed test setup. Davis bury flex gets rave reviews (except
for yours) all over the net and on-the -air. I have over 450ft of the stuff and it's super. I see no effects from coiling or bending.... Sorry you're having a difficult time... -- Charlie "Roy Lewallen" wrote in message ... Charlie wrote: I would recommend you take a look at Davis RF "BuryFlex" 9914. It is very nearly the exact same loss per 100ft (within a couple tenths of a db) as LMR400 and/or 9913. It can be directly buried in the soil with no other provisions needed. It has an abrasion resistant non-contaminating jacket that has a warranted 20 year service life. It is also quite affordable at about $.60/ft. It is very flexible and indeed is fine even as rotator loops. I use it on all bands I run from HF thru 6M and 2M. It uses standard UHF or N connectors as well. Loss per 100ft at 400MHZ is 2.9db Check it out here.... 1. http://www.davisrf.com/ham1/coax.htm#buryflex I've got some of that which I purchased new, and did some extensive tests on it with a network analyzer. The loss varies all over the map depending on how you coil, bend, or flex the cable, and I never saw loss anywhere near as low as the spec says. A typical value at 400 MHz was more like 5 - 5.5 dB/100 ft. Glad you're happy with it. Roy Lewallen, W7EL |
Coax recomendations
On Sat, 10 Dec 2005 06:27:18 -0600, "Charlie"
wrote: Sounds like a flawed test setup. Hah hah. Very funny. If Roy says it's bad--it's bad. |
Coax recomendations
I don't know what you two have going but his "analysis" flies in the face of
every other review and/or comment I have ever read about Davis 9914. As well as my own experience of low loss and great performance. I have several bends in my runs of 9914 and no adverse swr. Have you looked at all the positive user's reviews at eHam about it? Not a single negative remark.. 1. http://www.eham.net/reviews/detail/4515 One might also want to check this link for another endorsement of Davis BuryFlex 9914 2. http://lists.contesting.com/archives.../msg00010.html The again one could just read what is posted at this link at the eHam Elmer's Forum - all very positive 3. http://www.eham.net/forums/Elmers/38717 I'm not saying Roy is misstating what he saw. I'm saying what he saw misstates the real quality of this coax. 1. Maybe he got a bad piece 2. Maybe he had a loose connector 3. Maybe he didn't calibrate the network analyzer 4. etc etc etc....NO ONE else I can find dislikes this 9914!!! -- Charlie "Wes Stewart" wrote in message ... On Sat, 10 Dec 2005 06:27:18 -0600, "Charlie" wrote: Sounds like a flawed test setup. Hah hah. Very funny. If Roy says it's bad--it's bad. |
Coax recomendations
Wes Stewart wrote:
On Sat, 10 Dec 2005 06:27:18 -0600, "Charlie" wrote: Sounds like a flawed test setup. Hah hah. Very funny. If Roy says it's bad--it's bad. Agreed! |
Coax recomendations
On Sat, 10 Dec 2005 11:59:27 -0600, "Charlie"
wrote: Have you looked at all the positive user's reviews at eHam about it? User reviews are testimonial, not skilled measurement. One might also want to check this link for another endorsement of Davis Endorsements are just that, again, not skilled measurement. The again one could just read what is posted at this link at the eHam Elmer's Forum - all very positive Being positive and being correct are not the same thing. I'm saying what he saw Roy and anyone else is perfectly capable of speaking for him(them)self and telling us what he (they) saw. Interpretation is prone to transcription error, a frequent element of testimonial and endorsement. 1. Maybe he 2. Maybe he 3. Maybe he There are no maybes. Within this group there are experts in every sense of the word that are credentialed and experienced. Among this group are several Metrologists who do or have done these kind of things (determine loss) for a living. 4. etc etc etc....NO ONE else I can find dislikes this 9914!!! Roy is not offering an expression of personal taste, he is merely stating that products often suffer claim inflation, which we can observe to be inflated further by uninformed testimony. He offered one very specific counter-claim in a region of RF that is especially prone to error from the horde of eham testifiers. Their possession of exotic tools does not confer upon them the ability to correctly determine power (and by that extension loss). If you want to challenge a technical statement, you have to go to the statement and examine it by parts. Ask for data. Ask for the references (and I don't mean chapter citations). Look at the computations. Rebutting with testimonials is useless as they only serve vanity. 73's Richard Clark, KB7QHC |
Coax recomendations
The biggest problem needs to be solved - the fact that the shack is too far
from the antenna. Move the darn shack and be done with it! |
Coax recomendations
On Sat, 10 Dec 2005 18:40:43 +1300, "Ross Biggar"
wrote: I am putting up a second tower , but it will be about 200feet from the shack and about 70feet high. What coax is recommended to reduce loss to a minimum,and to feed a multiband beam with a 2kw amplifier. Hard line excepted due to cost. Ross, Interesting to see use of such a long line. We have been reliably informed that nobody uses more than 75' or so! Starting with the question "what is wrong with commonly available RG213", you would expect a loss around 2.4dB in a 100m run (200' + 70' + 30' tails) with an average VSWR of 1.5. Given that the lowest ambient noise level on 20m is around 20dB above typical receiver noise floor, the impact of 2.4dB of loss on receive is insignificant. On transmit, you will lose about 45% of your power in the line, so with your 2KW (output?) amplifier, you will still have 1100W arriving at the antenna. Will that do the job OK? Is ladder line the panacea? Wireman 554 directly connected to a 50 ohm load would have a loss of ~1.7dB and a little extra for baluns brings you close to 2dB, so it is not a whole lot better than RG213. However, if you used a 9:1 balun at each end, you would expect line loss of ~0.6dB and a little extra for baluns brings you close to 0.8dB. Now that seems respectable. Problem is that you live in the land of the long white cloud, and ladder line performance is degraded significantly when wet, so it might not be acceptable in your situation when wet. Lets look at home made open wire line using 2mm copper spaced 150mm for a 600 ohms line. If you used the same 9:1 balun at each end, you would expect line loss of ~0.2dB and a little extra for baluns brings you close to 0.4dB. Now that seems quite good. Anecdotally, such an air spaced line is not affected significantly by weather / water, but that will depend on the quality of the insulators and your rigging methods. Remember that the open wire solutions above need to be tuned feeders or you will need an ATU. I suggest that you will need the ATU for multi band operation, so you should allow another tenth of a dB or so for ATU loss. Someone will probably suggest that LDF6-50 (32mm (1.25") hardline) could achieve 0.3dB loss, but could you afford it, would it be good value? Owen -- |
Coax recomendations
I had a bad experience with Belden 9913 and if Davis 9914 has the same
mechanical properties, be careful. I taped some 9913 to a mast and sometime later discovered it had been squished flat from the tight wrap of electrical tape. I have also seen people ty-rap 9913 and destroy its shape. If Davis 9914 has the center conductor suspended by a thin spiral thing like 9913, I would not be surprised with varying performance when bending it. Here is some coax that looks like better performance than 9913 or Davis 9914 (2.7dB/450MHz/100ft) has the same Polyethylene outer jacket as Davis and is cheaper. Check http://yanta.pair.com/jefatech/specs...LL400Specs.pdf Mike Charlie wrote: I would recommend you take a look at Davis RF "BuryFlex" 9914. It is very nearly the exact same loss per 100ft (within a couple tenths of a db) as LMR400 and/or 9913. It can be directly buried in the soil with no other provisions needed. It has an abrasion resistant non-contaminating jacket that has a warranted 20 year service life. It is also quite affordable at about $.60/ft. It is very flexible and indeed is fine even as rotator loops. I use it on all bands I run from HF thru 6M and 2M. It uses standard UHF or N connectors as well. Loss per 100ft at 400MHZ is 2.9db Check it out here.... 1. http://www.davisrf.com/ham1/coax.htm#buryflex |
Coax recomendations
Owen Duffy wrote:
Interesting to see use of such a long line. We have been reliably informed that nobody uses more than 75' or so! Actually, the assertion was that 75' is about average. And even this special case problem doesn't rise to the level of your 100 meter example. -- 73, Cecil http://www.qsl.net/w5dxp |
Coax recomendations
Mike wrote:
I had a bad experience with Belden 9913 ... Me too. I just can't seem to keep water out of it. -- 73, Cecil http://www.qsl.net/w5dxp |
Coax recomendations
If Davis 9914 has the center conductor suspended by a thin spiral
thing like 9913, Davis BuryFlex 9914 does not have the center conductor suspended by a thin spiral. 1. http://www.davisrf.com/ham1/coax.htm#buryflex It amazes me that no one else (that I can find) has found Davis BuryFlex to be "bad coax". It has been in production well over 10 years. Moreover I am amazed how many of you are non-thinking lambs following along head-to-tail after your shepherd. And also Davis emphasizes in it's data that this coax is flexible enough for rotator loops and yet one guy says it is "bad coax" and so everyone falls to their knees and worships accordingly? And as far as data goes...is this guys data more accurate then the Davis RF company that has been in the wire and cable business with engineering professionals on the payroll since 1980? Sheesh......take off the blinders people.....thousands of miles of Davis 9914 have been installed by government,commercial and amateur stations and just now we find out it's "bad coax" after more than 10 years? Somebody is asleep at the switch....... -- Charlie "Mike" wrote in message . net... I had a bad experience with Belden 9913 and if Davis 9914 has the same mechanical properties, be careful. I taped some 9913 to a mast and sometime later discovered it had been squished flat from the tight wrap of electrical tape. I have also seen people ty-rap 9913 and destroy its shape. If Davis 9914 has the center conductor suspended by a thin spiral thing like 9913, I would not be surprised with varying performance when bending it. Here is some coax that looks like better performance than 9913 or Davis 9914 (2.7dB/450MHz/100ft) has the same Polyethylene outer jacket as Davis and is cheaper. Check http://yanta.pair.com/jefatech/specs...LL400Specs.pdf Mike Charlie wrote: I would recommend you take a look at Davis RF "BuryFlex" 9914. It is very nearly the exact same loss per 100ft (within a couple tenths of a db) as LMR400 and/or 9913. It can be directly buried in the soil with no other provisions needed. It has an abrasion resistant non-contaminating jacket that has a warranted 20 year service life. It is also quite affordable at about $.60/ft. It is very flexible and indeed is fine even as rotator loops. I use it on all bands I run from HF thru 6M and 2M. It uses standard UHF or N connectors as well. Loss per 100ft at 400MHZ is 2.9db Check it out here.... 1. http://www.davisrf.com/ham1/coax.htm#buryflex |
Coax recomendations
Charlie wrote:
Somebody is asleep at the switch....... The great majority of humans who have ever lived found it easier to follow than to think. (Just an observation - I don't know anything about 9914.) -- 73, Cecil http://www.qsl.net/w5dxp |
Coax recomendations
I'd be glad to compare results and methodologies with anyone else who
has measured this coax. It would be particularly interesting and educational if someone else's results are significantly different from mine. Roy Lewallen, W7EL Charlie wrote: If Davis 9914 has the center conductor suspended by a thin spiral thing like 9913, Davis BuryFlex 9914 does not have the center conductor suspended by a thin spiral. 1. http://www.davisrf.com/ham1/coax.htm#buryflex It amazes me that no one else (that I can find) has found Davis BuryFlex to be "bad coax". It has been in production well over 10 years. Moreover I am amazed how many of you are non-thinking lambs following along head-to-tail after your shepherd. And also Davis emphasizes in it's data that this coax is flexible enough for rotator loops and yet one guy says it is "bad coax" and so everyone falls to their knees and worships accordingly? And as far as data goes...is this guys data more accurate then the Davis RF company that has been in the wire and cable business with engineering professionals on the payroll since 1980? Sheesh......take off the blinders people.....thousands of miles of Davis 9914 have been installed by government,commercial and amateur stations and just now we find out it's "bad coax" after more than 10 years? Somebody is asleep at the switch....... |
Coax recomendations
Phil Wheeler wrote:
Wes Stewart wrote: On Sat, 10 Dec 2005 06:27:18 -0600, "Charlie" wrote: Sounds like a flawed test setup. Hah hah. Very funny. If Roy says it's bad--it's bad. Agreed! Please, folks, I didn't say that Davis BuryFlex is bad. I said that careful measurements of the one 100 foot piece I have show it to have much more loss than the specification indicates, and that the loss is variable with flexing and bending. It's possible that the piece I have is somehow defective. Everyone can interpret and act on this or not as they choose. But I certainly won't be installing this brand and type of cable in a critical application without carefully testing it first. Huge numbers of ravingly positive testimonials can be found for CFA antennas, cryogenically treated oxygen-free speaker cable, astrological forcasts, and homeopathic remedies. I'm not interested in testimonials for those or for coax cable either, all for the same reason. But I'd love to see the results of anyone else's measurements. The 100 foot piece I have was purchased several years ago from The Wireman, so I know it's the genuine article. (It's also marked as Davis BuryFlex.) It's been inside and unused since. Roy Lewallen, W7EL |
Coax recomendations
TY Cecil...sadly that is the essence of this thread.....
-- Charlie "Cecil Moore" wrote in message et... Charlie wrote: Somebody is asleep at the switch....... The great majority of humans who have ever lived found it easier to follow than to think. (Just an observation - I don't know anything about 9914.) -- 73, Cecil http://www.qsl.net/w5dxp |
Coax recomendations
I have emailed Davis RF and asked them to send me their test results. Yes
it will be interesting. Roy..doesn't seem a bit odd that NO ONE ELSE in over 10 years of BuryFlex production has cited these same alarming "test results". -- Charlie "Roy Lewallen" wrote in message ... I'd be glad to compare results and methodologies with anyone else who has measured this coax. It would be particularly interesting and educational if someone else's results are significantly different from mine. Roy Lewallen, W7EL Charlie wrote: If Davis 9914 has the center conductor suspended by a thin spiral thing like 9913, Davis BuryFlex 9914 does not have the center conductor suspended by a thin spiral. 1. http://www.davisrf.com/ham1/coax.htm#buryflex It amazes me that no one else (that I can find) has found Davis BuryFlex to be "bad coax". It has been in production well over 10 years. Moreover I am amazed how many of you are non-thinking lambs following along head-to-tail after your shepherd. And also Davis emphasizes in it's data that this coax is flexible enough for rotator loops and yet one guy says it is "bad coax" and so everyone falls to their knees and worships accordingly? And as far as data goes...is this guys data more accurate then the Davis RF company that has been in the wire and cable business with engineering professionals on the payroll since 1980? Sheesh......take off the blinders people.....thousands of miles of Davis 9914 have been installed by government,commercial and amateur stations and just now we find out it's "bad coax" after more than 10 years? Somebody is asleep at the switch....... |
Coax recomendations
Charlie wrote:
I have emailed Davis RF and asked them to send me their test results. Yes it will be interesting. Roy..doesn't seem a bit odd that NO ONE ELSE in over 10 years of BuryFlex production has cited these same alarming "test results". No. My experience is that the vast majority of amateurs don't have the ability and/or confidence and/or interest and/or equipment to make good measurements. And lacking the ability to measure it, very few would be able to discern the difference in loss. If my measurements are typical, commercial and government users (if there indeed are any for this particular cable type) would quietly reject the stuff on incoming inspection and order something else. I do have a high degree of confidence that my measurements are accurate. I took a lot of care in characterizing the cable before using it for making remote antenna impedance measurements in the course of a consulting job. But it's entirely possible that the particular piece of cable I have is defective. That would just point to a quality control problem rather than overzealous specsmanship. In your query of Davis, I hope you asked them if they routinely test production batches for loss, and if so how often and when the last test was run. It's possible that something in their process changed relatively recently. If no other reader of this newsgroup has some of this cable and the ability to test it, I'll see if I can arrange for someone else to make measurements and post results. Roy Lewallen, W7EL |
Coax recomendations
Roy the kind of test results you cited would be extremely evident whether
someone has a network analyzer or just an swr meter. That defense is sorely transparent in my opinion. To suggest that most amateurs would not even have any interest if their bent or coiled 9914 suddenly jumped off the scale for loss and mismatch is ludicrous to say the least. Let me be clear ...I am not disputing what you claim you got as test results. My conclusion is either the 100ft length you had was bad or something skewed your calibrated setup. My career was in microwave r&d and I know that it takes repeatable test results to form a valid, verifiable and publishable data. This is not personal Roy....but it is somewhat stimulating. -- Charlie "Roy Lewallen" wrote in message ... Charlie wrote: I have emailed Davis RF and asked them to send me their test results. Yes it will be interesting. Roy..doesn't seem a bit odd that NO ONE ELSE in over 10 years of BuryFlex production has cited these same alarming "test results". No. My experience is that the vast majority of amateurs don't have the ability and/or confidence and/or interest and/or equipment to make good measurements. And lacking the ability to measure it, very few would be able to discern the difference in loss. If my measurements are typical, commercial and government users (if there indeed are any for this particular cable type) would quietly reject the stuff on incoming inspection and order something else. I do have a high degree of confidence that my measurements are accurate. I took a lot of care in characterizing the cable before using it for making remote antenna impedance measurements in the course of a consulting job. But it's entirely possible that the particular piece of cable I have is defective. That would just point to a quality control problem rather than overzealous specsmanship. In your query of Davis, I hope you asked them if they routinely test production batches for loss, and if so how often and when the last test was run. It's possible that something in their process changed relatively recently. If no other reader of this newsgroup has some of this cable and the ability to test it, I'll see if I can arrange for someone else to make measurements and post results. Roy Lewallen, W7EL |
Coax recomendations
On Sat, 10 Dec 2005 17:15:44 -0800, Roy Lewallen
wrote: If no other reader of this newsgroup has some of this cable and the ability to test it, I'll see if I can arrange for someone else to make measurements and post results. Roy, this seems a case of brand loyalty vs objective measurement and evaluation (albeit on a single sample). You will change your mind based on more measurement data, either strengthening your existing opionion or changing it. Those with brand loyalty already know all they need to know, life is comfortable. You are talking different languages, and the only way there will be agreement is if you capitulate (which would be unprincipled in the absence of evidence). Owen I remember the fierce debates over 9913, there were nearly as many words written about how fabulous it was, as there were words written on how to keep water out of it. -- |
Coax recomendations
"Ross Biggar" wrote in message ... I am putting up a second tower , but it will be about 200feet from the shack and about 70feet high. What coax is recommended to reduce loss to a minimum,and to feed a multiband beam with a 2kw amplifier. Hard line excepted due to cost. Regards Ross ZL1WN I needed conventional low loss coax on the job a few years ago. Boss was paying for it, so I was not pinching pennies. Best I could find was the Times LMR400. As I recall, the center conductor is #9; so, it may not fit some brands of N connectors. Unlike the 9913, this will not soak up water. The loss at 50 MHz is 0.9 db, vs 1.6 db for 213 (100 feet). I know you want 20 meters, but 50 MHz is the lowest frequency I have any numbers for. Tam/WB2TT |
Coax recomendations
Owen it is NOT brand loyalty. It is the publicly published data by RF Davis
(for the past 10+ years) vs. Roy's one-shot test setup some years ago. I'm not out to discredit Roy...I even shook his hand once at a Hamfest. -- Charlie "Owen Duffy" wrote in message ... On Sat, 10 Dec 2005 17:15:44 -0800, Roy Lewallen wrote: If no other reader of this newsgroup has some of this cable and the ability to test it, I'll see if I can arrange for someone else to make measurements and post results. Roy, this seems a case of brand loyalty vs objective measurement and evaluation (albeit on a single sample). You will change your mind based on more measurement data, either strengthening your existing opionion or changing it. Those with brand loyalty already know all they need to know, life is comfortable. You are talking different languages, and the only way there will be agreement is if you capitulate (which would be unprincipled in the absence of evidence). Owen I remember the fierce debates over 9913, there were nearly as many words written about how fabulous it was, as there were words written on how to keep water out of it. -- |
Coax recomendations
On Sat, 10 Dec 2005 19:46:15 -0600, "Charlie"
wrote: Owen it is NOT brand loyalty. It is the publicly published data by RF Davis (for the past 10+ years) vs. Roy's one-shot test setup some years ago. I'm not out to discredit Roy...I even shook his hand once at a Hamfest. We should be a little suspicious of manufacturers claims. Davis' can be expected to support their product. Roy's single poor experience is concerning, indicating either a quality control issue, or more general non-compliance with spec (both are issues for Davis). An independent test of stock cable and possibly Roy's sample would be most interesting. I know I have made measurements and adjustments at times and in searching for possible explanations, the cable quality is on the radar. In one of those cases, a mobile installation could not be trimmed properly, and the Taiwanese RG58 centre conductor was so far off centre, it was nearly touching the braid. We have all cut cables up and found inconsistent braid weave, open braid weave, voids in the dielectric, faulty stranding of inner conductor, off centre centre conductors. It is those kind of issues that downgrade a suppliers reputation, not their ability to select a good cable sample for laboratory measurement. Perhaps if you're a whiz, you should perform some measurements so you can report first hand your experience. We don't see the Davis stuff on this side of the world. The concept seems a good one, PE sheath, braid+foil outer, foam dielectric, stranded inner, but you have to ask yourself why they haven't displaced Heliax and its copies. I suspect the reasons include IM and noise issues associated with the braid+foil, mechanical issues with the foam, and resistance to water. Experience with noise and IM problems with braid+foil coax in fixed installations makes me wonder how it stands up in a rigorous test of flexing for a rotator loop, not anecdotal evidence, but a structured test. Owen -- |
Coax recomendations
On Sat, 10 Dec 2005 20:42:18 -0500, "Tam/WB2TT"
wrote: "Ross Biggar" wrote in message ... I am putting up a second tower , but it will be about 200feet from the shack and about 70feet high. What coax is recommended to reduce loss to a minimum,and to feed a multiband beam with a 2kw amplifier. Hard line excepted due to cost. Regards Ross ZL1WN I needed conventional low loss coax on the job a few years ago. Boss was paying for it, so I was not pinching pennies. Best I could find was the Times LMR400. As I recall, the center conductor is #9; so, it may not fit some brands of N connectors. Unlike the 9913, this will not soak up water. The loss at 50 MHz is 0.9 db, vs 1.6 db for 213 (100 feet). I know you want 20 meters, but 50 MHz is the lowest frequency I have any numbers for. LMR400: 300' at 14.2MHz with VSWR=1.5, loss~=1.5dB Tam/WB2TT -- |
Coax recomendations
Charlie wrote:
Roy the kind of test results you cited would be extremely evident whether someone has a network analyzer or just an swr meter. That defense is sorely transparent in my opinion. To suggest that most amateurs would not even have any interest if their bent or coiled 9914 suddenly jumped off the scale for loss and mismatch is ludicrous to say the least. Would you really notice if your cable loss was about 3 dB higher than specified at 400 MHz and if it varied by a dB or two when the cable is flexed and bent? What measurement equipment do you use which would cause this amount of extra loss to "jump off the scale"? And what causes you to think that increased loss would cause mismatch to "jump off the scale"? Increased loss will improve, not degrade, the impedance match. Let me be clear ...I am not disputing what you claim you got as test results. My conclusion is either the 100ft length you had was bad or something skewed your calibrated setup. What you have as evidence is Davis' spec on the one hand, and my measurement report on the other. You've chosen to believe that Davis' cable all meets its published specifications. I have exactly the same evidence, but know my capabilities and that of my equipment, so I believe my measurements -- but always keeping in mind that it's a single sample. Additional measurements made by someone else on another piece of the cable would increase the knowledge base, although I'm sure there are people who would choose to ignore the evidence no matter how much is presented. My career was in microwave r&d and I know that it takes repeatable test results to form a valid, verifiable and publishable data. That's great! Then you have the background to be able to make decent measurements, and you said you're using some of the cable. Why not just measure the loss in a length of it and report your results? This is not personal Roy....but it is somewhat stimulating. I hope it's caused a few people to think a bit about how they evaluate evidence to determine the truth of a matter. It's something which too many people are woefully unable or unwilling to do. Roy Lewallen, W7EL |
Coax recomendations
"Roy Lewallen" wrote in message ... I've got some of that which I purchased new, and did some extensive tests on it with a network analyzer. The loss varies all over the map depending on how you coil, bend, or flex the cable, and I never saw loss anywhere near as low as the spec says. A typical value at 400 MHz was more like 5 - 5.5 dB/100 ft. Glad you're happy with it. Roy Lewallen, W7EL Roy what kind of coax do you recommend along the same type ? I soon plan on putting up several beams, tribander for the low bands, 6 meter, 2 meter and a 432 antenna. Should be running about 125 feet or so. While I know hardline would be best for the VHF , I don't want to (can't spend the money, easy to install for the rotator) so I want to stay with one of the 9913/lmr400 types. I have had a piece of 9913 up for about 10 years and it seems to be ok, no water I can tell, I still would like to go with a solid foam type instead of the hollow core . Just looking at the specks and advertising can sometimes be deceiving. de KU4PT |
Coax recomendations
Owen with all due respect there is no "question" why 9914 has not replaced
Heliax and that is due to loss factors. BTW 9914 is impervious to water in and of itself..so evidently you have not done much homework on this particular coaxial cable. Davis 9914 is recommended for rotator loops. Your supposed quandary about "9914 replacing Heliax" is contrived in my opinion to murk up the waters of this issue and maybe steer focus away from what obviously, at least to me, is an unfortunate one-time testing experience by Roy. Yes I suppose we should always be "suspicious" of manufacturer's claims but do you exercise that philosophy across the board? How about the tires on your car? How about the prescription medicines you may take and also over the counter meds? How about those fast food burgers? How about your drinking water? Are you as equally "suspicious" of these products or is this philosophy of yours only revealed to others when you want to discredit someone else's data. I think the later and not the former sir. Owen....I give you a salute for being an obvious "spin doctor" for Roy's one time, one sample, one conclusion, years ago test cycle. A job well done on the surface..however the underlying facts remain. Davis BuryFlex has been sold for well over 10 years in the "real world" and these same real people, government agencies, municipalities, and service agencies have used thousands of miles of it with no apparent issues. Cite similar tests to Roy's and I'll reconsider. As for me I'll go with the Davis data, once it arrives, and do a calibration standards trace on their test station. Was Roy's test bench's calibration traceable? It is preposterous you would continually cast aspersions towards a company that has been in the wire and cable business for over 25 years and promote and crusade for a one time shot-in-the-dark independent so-called "test". You do not fool me sir....best regards..... -ps How many times do you think Davis has tested their 9914 in the past 10+ years? More than the one single time Roy has perhaps? -- Charlie "Owen Duffy" wrote in message ... On Sat, 10 Dec 2005 19:46:15 -0600, "Charlie" wrote: Owen it is NOT brand loyalty. It is the publicly published data by RF Davis (for the past 10+ years) vs. Roy's one-shot test setup some years ago. I'm not out to discredit Roy...I even shook his hand once at a Hamfest. We should be a little suspicious of manufacturers claims. Davis' can be expected to support their product. Roy's single poor experience is concerning, indicating either a quality control issue, or more general non-compliance with spec (both are issues for Davis). An independent test of stock cable and possibly Roy's sample would be most interesting. I know I have made measurements and adjustments at times and in searching for possible explanations, the cable quality is on the radar. In one of those cases, a mobile installation could not be trimmed properly, and the Taiwanese RG58 centre conductor was so far off centre, it was nearly touching the braid. We have all cut cables up and found inconsistent braid weave, open braid weave, voids in the dielectric, faulty stranding of inner conductor, off centre centre conductors. It is those kind of issues that downgrade a suppliers reputation, not their ability to select a good cable sample for laboratory measurement. Perhaps if you're a whiz, you should perform some measurements so you can report first hand your experience. We don't see the Davis stuff on this side of the world. The concept seems a good one, PE sheath, braid+foil outer, foam dielectric, stranded inner, but you have to ask yourself why they haven't displaced Heliax and its copies. I suspect the reasons include IM and noise issues associated with the braid+foil, mechanical issues with the foam, and resistance to water. Experience with noise and IM problems with braid+foil coax in fixed installations makes me wonder how it stands up in a rigorous test of flexing for a rotator loop, not anecdotal evidence, but a structured test. Owen -- |
Coax recomendations
To find ALL electrical characteristics and performance of
solid-polyethylene transmission line, use program COAXPAIR, from audio frequencies to UHF. Accuracy is of the same order as physical dimensions can be measured. Use a micrometer to measure inner conductor diameter and diameter over insulant. Or just guess at it. No need to unwind the cable off the drum! In a few seconds, download COAXPAIR from website below and run immediately. ---- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
Coax recomendations
On Sat, 10 Dec 2005 21:50:15 GMT, Owen Duffy wrote:
[good stuff snipped] | |Someone will probably suggest that LDF6-50 (32mm (1.25") hardline) |could achieve 0.3dB loss, but could you afford it, would it be good |value? I wasn't going to go that far, and I realize it's probably not common in ZL but I've bought lengths of LDF5-50 at ham flea markets. The last purchase, claimed to be about 10 meters worth, but by my estimation at least twice that long, and new and unused, cost me $10 U.S. Most of this stuff is leftover or removed from commercial two-way or cell phone use and shows up all of the time. LDF4-50 is even more common. I often buy short pieces that have been cut down, just for the connectors that are still on one end. I find it curious that Andrew cable is seen so often at these events and yet I've -never- even seen a piece of Davis cable, dispite the claims that miles of it are in commercial use. |
Coax recomendations
On Sun, 11 Dec 2005 05:39:27 +0000, Wes Stewart *n7ws*@ yahoo.com
wrote: I wasn't going to go that far, and I realize it's probably not common in ZL but I've bought lengths of LDF5-50 at ham flea markets. The last purchase, claimed to be about 10 meters worth, but by my estimation at least twice that long, and new and unused, cost me $10 U.S. Most of this stuff is leftover or removed from commercial two-way or cell phone use and shows up all of the time. LDF4-50 is even more common. I often buy short pieces that have been cut down, just for the connectors that are still on one end. I find it curious that Andrew cable is seen so often at these events and yet I've -never- even seen a piece of Davis cable, dispite the claims that miles of it are in commercial use. I agree with Ian's comments, the larger sizes are often available here as they are less attractive to hams. But if you buy 3 or 4 lengths of LDF5 or LDF6 and use connectors to join them, you will run into big $ unless the connectors come very cheap. Andrews has some braid+foil / foam coax, and they perform roughly similarly to LMR400, BuryFlex and 9913. To my mind LDF4-50 would be acceptable in this configuration, and the great advantage is that if water gets in somewhere, it doesn't wick right down the cable. I haven't handled BuryFlex, and I saw the claim it is waterproof, but I suspect it is not as waterproof as Heliax type cable where the closed cell foam dielectric is bonded to the inner and outer conductor with an adhesive, and there is no braid to form a natural wick. I am in the throes of replacing feedline on a HF dipole to repair damage by birds. The birds don't seem to eat PE irrigation tube, so I have fitted RG6 with a W2DU style balun inside 13mm PE tube to defeat the birds. The birds have attacked the LDF4-50 on the VHF/UHF antennas, but even if they make a hole in the copper, it doesn't seem to affect cable performance measurably, probably because the water can't travel up and down the cable from the hole. Still, parts of ZL have Keas, and they will eat anything, especially rubber or plastic! So I feel for our ZL friends running coax over 60m of ground. BTW, I added BuryFlex to my online line loss calculator, 9913 and C2FP were already there. I still like the open line option, but it will be real important to use effective baluns to adequately ensure balance. It used to be common commercial practice when HF Radio was used more widely for international telephony / telegraphy. Owen -- |
Coax recomendations
On Sun, 11 Dec 2005 06:06:08 GMT, Owen Duffy wrote:
On Sun, 11 Dec 2005 05:39:27 +0000, Wes Stewart *n7ws*@ yahoo.com wrote: I wasn't going to go that far, and I realize it's probably not common in ZL but I've bought lengths of LDF5-50 at ham flea markets. The last purchase, claimed to be about 10 meters worth, but by my estimation at least twice that long, and new and unused, cost me $10 U.S. Most of this stuff is leftover or removed from commercial two-way or cell phone use and shows up all of the time. LDF4-50 is even more common. I often buy short pieces that have been cut down, just for the connectors that are still on one end. I find it curious that Andrew cable is seen so often at these events and yet I've -never- even seen a piece of Davis cable, dispite the claims that miles of it are in commercial use. I agree with Ian's comments, the larger sizes are often available here as they are less attractive to hams. But if you buy 3 or 4 lengths of LDF5 or LDF6 and use connectors to join them, you will run into big $ unless the connectors come very cheap. I have a ham friend who uses long runs of coax to his several towers. He is a big gun on 80 and 160 meters, so this mainly applies at m-f to h-f. He uses a lot of LDF5-50 that he obtains in shorter pieces. His technique, as he briefly described it to me, is to -not- use connectors but splice the lengths directly. The center conductor on these cables is hollow, so he inserts a short length of brass or copper into the ID and solders it in place. I don't know whether he adds any insulation next or not, but I would envision injecting some low-expansion spray foam later. He then wraps the outer conductor with brass or copper foil and solders this in place. (Here is where I would inject the foam.) This is then wrapped with tape for protection. I would use a double layer of #27 3M tape with an overwrap of plastic electrical tape. To strengthen the joint mechanically, he straps on a length of steel angle using stainless hose clamps. For lines on or in the ground this stays in place. For runs up the tower, after the line is in place, strapping to the tower is sufficient support. |
Coax recomendations
Owen Duffy wrote:
LMR400: 300' at 14.2MHz with VSWR=1.5, loss~=1.5dB Open-wire line: 300' at 14.2MHz with VSWR=1.5, loss~=0.225dB Costs about 16 cents/ft if one rolls one's own. -- 73, Cecil http://www.qsl.net/w5dxp |
Coax recomendations
Wes Stewart wrote:
I agree with Ian's comments, the larger sizes [of hardline] are often available here as they are less attractive to hams. But if you buy 3 or 4 lengths of LDF5 or LDF6 and use connectors to join them, you will run into big $ unless the connectors come very cheap. Generally the same applies to the connectors as to the cable itself - the surplus prices are much lower than the new prices, and larger sizes may even be cheaper. However, I do agree that you don't need connectors in order to make a splice in a static installation. This technique makes a solid splice, with a low SWR even at 432MHz: I have a ham friend who uses long runs of coax to his several towers. He is a big gun on 80 and 160 meters, so this mainly applies at m-f to h-f. He uses a lot of LDF5-50 that he obtains in shorter pieces. His technique, as he briefly described it to me, is to -not- use connectors but splice the lengths directly. The center conductor on these cables is hollow, so he inserts a short length of brass or copper into the ID and solders it in place. And for the smaller sizes with a solid center conductor, splice with a short length of hobby brass tuning over the outside. I don't know whether he adds any insulation next or not, but I would envision injecting some low-expansion spray foam later. The foam is mostly empty space anyway, so even at UHF an inch or so will hardly be missed. He then wraps the outer conductor with brass or copper foil and solders this in place. In some sizes, a slit length of copper water pipe can work too. This is then wrapped with tape for protection. I would use a double layer of #27 3M tape with an overwrap of plastic electrical tape. To strengthen the joint mechanically, he straps on a length of steel angle using stainless hose clamps. Yup, all of the above. It works fine. The overall conclusion is that - both physically and financially - large hardline is nowhere near as 'hard' as most people think. BTW, I do have one genuine Andrew splice for LDF5-50, which I'm hoarding for some undefined future need. It's truly a thing of wonder... especially the insert that connects the two hollow center conductors. One end screws in with a tapered variable-pitch thread, so the other end has to have a tapered variable-pitch *left-hand* thread. Only a CNC programmer with far too much time on his hands could have thought of that. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
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