Posted: 2/26/2012 1:17:48 PM EDT
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When I put my tower up, it may end up being quite a ways from the house. Like maybe 150'. That, + the 40' tower height, I'm near 200' run of coax. On top I'll have a Tennadyne LPDA, M2 2M7 2m yagi, and a Diamond X510HD. I may also have a 80m or 160m loop hanging off the side. If so, it'll be def w/ Coax up to an SGC coupler, then ladder line. So, there'll be 4 runs of coax close to 200' long (ouch). I'm a little less worried about loss in the HF lines, but for 2m/440 there could be quite a bit. What coax do you recommend for: running up the tower? From house to tower base? Would this recommendation be different if I went nuts and bought an 80' 45G (bringing the total run to 230'+)?  I'm assuming the base of the tower is where the ICE protectors go. I'll also have to run a ground wire back to the house to bond it all together (?), but not sure if that should go inside the conduit, or outside w/ intermittent ground rods along thew way? If anyone has pictures of how this is properly done, I'd love to see them. Thanks, -Slice |
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Take a look at at some coax comparison charts so you can compare the loss of various cables at different frequencies. Like you said, the VHF/UHF will have the most loss and you're at the distance where LMR-400 would be a minimum and some would suggest going to LMR-600 or hardline, etc.
I'm planning a tower myself and it will have approx 140' total run from the house to the top, and plan to use L-Com CA-400, their in-house Chinese-made LMR-400. http://www.l-com.com/item.aspx?id=21109 There is a datasheet that shows the loss on their website. For 100' - 0.7 dB at 30 MHz, 1.5 dB at 150 MHz, 2.7 dB at 450 MHz. So for a 200' run you're looking at 1.4 dB max on HF, 3.0 dB on 2 meters, and 5.4 dB on 70cm. Turns your 10.3 dBd gain 2M7 into a 7.3 dBd antenna. The LMR-600 will have almost half the loss at twice the price, plus more expensive sonnectors, etc. It's a cost performance trade-off like most things are. I'll have to settle for the loss on 70cm myself because I can't afford better coax right now and I'll be buying a bulk roll of 400 anyways. I'll use coax grounding kits at the top of the tower and use a flexible coax from there around the rotor to the antennas. Surge supression box at the tower base bonded to the tower ground system, which is bonded to my existing ground system. I plan to run the best bonding conductor I can afford outside of the conduit. Not sure about ground rods on the way, I wondered that myself. ETA: Isn't a burried bare copper conductor kinda like a really long ground rod anyways? 
ETA: How it is properly done - caution, large PDF. http://www.radioandtrunking.com/downloads/motorola/R56_2005_manual.pdf |
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Times Microwave has a nice coax loss calculator: http://www.timesmicrowave.com/cgi-bin/calculate.pl I did some math, and I think I'll run all LMR-400 for HF, and in the conduit have LMR-600 for VHF. There's virtually no UHF around here, so I'm not going to go crazy on something specifically for it. I've never done 2m SSB, but that's what the M2 is for. I'm a little worried about the loss on it over this kind of run, but I guess it is what it is since I already bought the antenna. If there's a higher gain VHF vertical out there, I couldn't find it. I suppose I could put an in-line pre-amp on the tower or at the base to try to compensate for this –– has anybody done that? |
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Coax power capacity and attenuation charts at Universal Radio:
http://www.universal-radio.com/catalog/cable/coaxperf.html#atten |
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Coax power capacity and attenuation charts at Universal Radio: http://www.universal-radio.com/catalog/cable/coaxperf.html#atten Thanks for that link AFM 
Back when I got started a few years ago I had no idea about what kind of coax to get for 2m/70cm. I told the nice man at HRO that I wanted the best coax I could afford, and he ended up selling me a big roll of Belden 9913. Looks like I did okay according to the chart. While I knew 9913 was pretty decent, I didn't know how it compared to other coax. Good luck Slice! Looking forward to pics and progress reports of your new tower project. At the last hamfest I attended I remember seeing hardline for around a buck a foot in quantity. Saw some standard LMR-400 on Craigslist here a while back, so you might want to keep an eye there as well. Edited for spellin' and grammah... Posted Via AR15.Com Mobile |
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You maybe able to find some short rolls of 75 ohm cable TV hardline. You will need a matching balun at each end. This is called poor mans hardline. +1. I got spool of RG-11 and a spool of LMR-400-75 for 10 cents/foot. Sure...they're both 75 ohm...but with a tuner, at that price, it's hard to beat. |
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Do you plan on running multiple HF rigs simultaneously? If not, how about a coax switch out on the tower. This would eliminate multiple coax runs from the shack and provide a transition point to a more flexible cable.
This could be done for VHF/UHF with some good surplus coax relays. |
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Quoted: Do you plan on running multiple HF rigs simultaneously? If not, how about a coax switch out on the tower. This would eliminate multiple coax runs from the shack and provide a transition point to a more flexible cable. This could be done for VHF/UHF with some good surplus coax relays. That's a good idea! I'll look into those. Have a recommendation for a (non-MFJ) model? |
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Do you plan on running multiple HF rigs simultaneously? If not, how about a coax switch out on the tower. This would eliminate multiple coax runs from the shack and provide a transition point to a more flexible cable. This could be done for VHF/UHF with some good surplus coax relays. That's a good idea! I'll look into those. Have a recommendation for a (non-MFJ) model? I was thinking the same thing. DXE - DX Engineering, but it costs more than MFJ... http://www.dxengineering.com/Products.asp?ID=85&SecID=33&DeptID=17 |
| Look at the andrew extremeflex http://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=342_345_967&products_id=1765 yes it is 1.99 a foot. Or look at catv hardline. Depending on how your match is on your antenna you will need little to no matching network. I can explain how to work with the catv stuff if you want to know. And the dx engineering coax switches work great. |
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Do you plan on running multiple HF rigs simultaneously? If not, how about a coax switch out on the tower. This would eliminate multiple coax runs from the shack and provide a transition point to a more flexible cable. This could be done for VHF/UHF with some good surplus coax relays. That's a good idea! I'll look into those. Have a recommendation for a (non-MFJ) model? As mentioned, the DXE units are better, but more $$. I suppose the DXE unit would be the way to go and allow you up to 8 antennas with only one feeder from the shack. Compare the DXE unit and 8 runs of good coax....DXE unit wins. ETA- I'm in the same boat at the BOL. I have a 54ft freestander laying in the yard and have been contemplating what I should do for coax feeders. I have a roll of RG213, but would really like to run hardline or Heliax out to the tower, then transition to the 213. My project is a few years off though, so I have time to look for the elusive $1.00 a ft. Heliax. |
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For cheap tips, make friends with the local cable TV tech and cell tower installers. I have scored some dirt cheap or even free hardline like this. Or antennas. 
Antennas laying next to my tower. 
I asked the crew if they were replacing the hardline and they said, "nope, but we'll let you know when we do." |
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You maybe able to find some short rolls of 75 ohm cable TV hardline. You will need a matching balun at each end. This is called poor mans hardline. I just tossed over 2k feet of .875. Most in 300+ foot chunks.  
I would have come picked it up. I would have helped...
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You maybe able to find some short rolls of 75 ohm cable TV hardline. You will need a matching balun at each end. This is called poor mans hardline. I just tossed over 2k feet of .875. Most in 300+ foot chunks.
I would have come picked it up. I would have helped...
I just got out of the field as a catv lineman. Went into the headend. I should still be able to get some. Usually .625 or .875 not too much of the .700 anymore. The .875 is interesting to work with. Very Very stiff and can kink too easily. I would scrap about 1k every two weeks or so. |