Tower and 7/8" hardline instalation, dual band operation on single antenna

[Logan005]

I recently acquired a 50' tilt over and telescoping tower. I plan to install it at my new house. the Radio room will be in my Garage with 60' of 2" conduit run to the base of the tower. I currently use LMR400 for my 30' run to my repeater duplexor, with this new set up i plan to acquire some 7/8" hardline or better. my tower will have several antennas on 2 bands topped with a workman UVS200 dual band antenna, I wish to use both bands on the UVS200, UHF for the GMRS repeater and the VHF for a HAM repeater. I assume i would need an additional pre-selector or cavity notch filter? I am sure this can be done, just how much cost and how to do? I will run 2 more LMR400 or LMR600 cables thru the conduit and up the tower for experimental antennas.
Is a 110' foot run of LMR400 to long for a 50 watt repeater? LMR600? would be nice if it were 110' straight up, but unfortunately that is not the case. I would locate the tower closer to the garage but that is also not possible.
When i was a kid i was given several hundred feet of 7/8" hardline by the local cable operator, will some operators still give it away or do they recycle it all now? also this tower has a huge dirt spade for the bottom, I expected much more foundation, should I install it the same way or set a concrete pad? I may also have a small environmental cabinet at the base of the tower, to possibly contain a small Motorola 25watt repeater, if the run to the garage is too long. and or other equipment that is necessary to be closer to the antenna. Please help direct me on this new endeavor, I appreciate any and all input. Thank in advance, Logan....

 

[W2PMX]

I assume i would need an additional pre-selector or cavity notch filter?

You can do it with a diplexer or other arrangement of cavities, but it won't be cheap. Another antenna would be a lot cheaper (they're only about $60), and work better.

Is a 110' foot run of LMR400 to long for a 50 watt repeater? LMR600?

LMR-400 loss at 150MHz is 1.7 db, at 450MHz it's 3db. LMR-600 at 150MHz is 1.1db, at 450MHz it's 1.9db. I wouldn't want to use any configuration like that.

should I install it the same way or set a concrete pad?

That depends on the winds where you are, but I wouldn't use less than a 4'X4'X4' (keyholed - bottom larger than the top) concrete pier, with the mounting plate bolted down by threaded rods that run to a plate at the bottom of the pier.

 

[Logan005]

You can do it with a diplexer or other arrangement of cavities, but it won't be cheap. Another antenna would be a lot cheaper (they're only about $60), and work better.
ok, was trying to keep the antennas down to one vertical and a yagi, how to mount 2 verticals on top of the same tower?

LMR-400 loss at 150MHz is 1.7 db, at 450MHz it's 3db. LMR-600 at 150MHz is 1.1db, at 450MHz it's 1.9db. I wouldn't want to use any configuration like that.
so I should only go the hardline route? ir is the run just too long to begin with?

That depends on the winds where you are, but I wouldn't use less than a 4'X4'X4' (keyholed - bottom larger than the top) concrete pier, with the mounting plate bolted down by threaded rods that run to a plate at the bottom of the pier.

This tower stood for over 20 years in my same neighborhood, just stabbed into the ground.

 

[mmckenna]

You'll be able to get the 7/8th's inch coax in the 2 inch conduit, but nothing else. I have an installation at work that uses 2 inch conduit and 7/8s and there isn't room left over for anything.

 

[Logan005]

You can do it with a diplexer or other arrangement of cavities, but it won't be cheap. Another antenna would be a lot cheaper (they're only about $60), and work better.

LMR-400 loss at 150MHz is 1.7 db, at 450MHz it's 3db. LMR-600 at 150MHz is 1.1db, at 450MHz it's 1.9db. I wouldn't want to use any configuration like that.
.

ok, I go with 3" PVC conduit and separate antennas, as far as cable runs, what would you recommend?

 

[Logan005]

also I found some 7/8" hardline at Habitat for humanity thrift store, but it is outside and laying behind stuff, has no price on it and I assume it is damaged by water intrusion.

 

[cabletech]

Hardline cable from the cable company is not numbered like normal radio cable.

If you get 625 cable, then it really is .635 across, next size, is 750 and is .760 across, next size is 850 and is .889 across.

All these cables take a specific connector that if you can get them run about $40 to $60 each and you will also need a special adaptor to fit on the main connector.

And all these cables are 75 ohm, but you will have not problem with power or swr.

I have two dual band repeaters using this type cable and they have been up for over 8 yrs. running 100watts.

 

[mmckenna]

ok, I go with 3" PVC conduit and separate antennas, as far as cable runs, what would you recommend?

For repeater use, steer clear of the LMR cables. You really want to stick with Heliax type cables (hard line) for everything but your jumpers. 1/2 inch LDF4-50 would be the minimum for a 200 foot run. As you go up in size (7/8" LDF5, 1 5/8" LDF6 etc) you will get slightly better performance, but it's going to cost you more. If I was doing this project for a public safety or commercial system, and wasn't footing the bill myself, I'd probably not use anything less than the 7/8", especially for UHF. You won't get two runs of 7/8" in a 3" conduit. I'd recommend using 2 separate runs of 3". The extra space in the conduit will make pulling the cable in a lot easier. If you ever expect to install additional cables, run the conduit now. Pipe is cheap, trenching isn't, so make the most of the hole in the ground while it's open. I'd install at least one additional run for future expansion.

While Andrews Heliax is the big name, there are other manufacturers of similar cables. Shop around and find the best price:
Andrews Heliax
CommScope,
Etc......

Also, since it sounds like you are trying to do this right from the start, I wouldn't invest all that money in hard line, conduit, trenching, tower work, etc and then put up a $60 amateur grade antenna. Installing on a tower is expensive and dangerous work. Invest in good antennas and feed line and it will pay off in the long run. If you can afford it, install commercial grade antennas. The trouble it will save you down the road will be well worth it. Most ham grade stuff is pretty crappy when you compare it to a high quality commercial antenna.

 

[Logan005]

The 1/2 inch LDF4-50 is affordable, what is the degrade in performance compared to the 7/8"? at 1/2" it seems like it would be easy to make several runs in a 2 1/2 inch conduit. would you recommend moving the tower closer to the radio room? I can locate my GMRS repeater in an environmental case at the base of the tower. but i plan to get an Icom FR6000 for my personal HAM repeater and i want that in a proper communications rack in my Garage 60' from the base of the tower.. I am also considering making the tower non tilting, but still telescoping. should I consider getting a better tower, if not now, in the near future? and yes mmckenna's Avatar mmckenna I plan to put quality antennas up, not looking to climb the tower more than a few times per decade. so your knowledge and expertise is greatly appreciated. Thank You!

 

[dksac2]

Get an OPEK UVS-300 antenna. It's the same antenna as the Workman, only one model better, you can find them on E Pay for $116.00 shipped. I have one and it's a great duel band antenna. It has 8.3 dbi and 11.7 dbi gain (2M & 70CM). I talk through repeaters over 50 miles away with a clean signal.
I had a Diamond 300 up and the OPEK talks much further. I even dropped it and broke a bunch of parts. OPEK sent me new parts free of charge, they would not even let me pay for shipping.

The higher gain maight make up for the loss in your coax. You could always use 450 Ohm ladder line and a 4 to 1 balun on each end. You will lose a max of 1DB, even with runs several hundred feet long, you just have to keep the ladder line away from any metal.

If you have a lot of wind at the top of the tower, you may have to use several folded dipole antennas. They are expensive and 3 will get you about 6 db gain, but the weather, ice and wind will never hurt them, they will last as long as you do. The OPEK antenna I have has stood 65MPH winds with zero problems, but it does bend with that much wind.

John

 

[Logan005]

Thanks for the recommendation, however as I have learned when using with a UHF repeater, the VHF portion will be wasted. unless you spend thousands on cavity's and have them tuned in place. so I was thinking a single band antenna would be more efficient. The gain sounds great. but someone correct me if I am wrong, gain over a band specific antenna? I like Yagi's add a rotor and you can adjust where your area of DX attention is. I would love a folded dipole antenna but they are way out there. but certainly a consideration, especially if I had a taller tower. lol I was not aware you could feed UHF over 450 ohm ladder line. only 1db over several hundred feet? seriously? Tell me more. Thank you, dksac2, anybody else?

 

[mmckenna]

Ideally you want your feed lines as absolutely short as possible. The newer LTE cellular equipment puts the radio up at the antenna, and just feeds the radio with fiber. This gives almost zero loss between the radio and antenna. While that wouldn't be easily do-able with your set up, you really want to keep the feed lines as short as you can. That could be accomplished by moving the tower closer to your radio room, or, in your case, installing the repeaters in a environmentally controlled box at the tower base.

1/2 inch coax would probably be suitable for a hobbyist. 7/8th's is going to get expensive and while you'll save a bit of loss, you are going to get into a area of diminishing returns. Keeping your feed lines short will be the most beneficial thing you can do.

While you could experiment with ladder line, it's not as easy as it sounds. Ladder line needs to be kept away from any conductive surface, so you'd need standoffs going up the tower, into your shack, etc. Rain, snow and ice can create issues with ladder line also. While coax is more expensive, it is a lot easier to work with.

And not to detract from anyone else's comments, but if you want to put up a good installation and not have to be fussing with the antennas frequently, spend the money on a better antenna. While I'm sure Workman and Opek make OK stuff, they are new to the market, they are amateur quality antennas, and I wouldn't invest that much money into your repeaters and top it off with a cheap antenna. While it may work fine for a few years, they likely won't last as long as a commercial grade antenna. As I said earlier, tower climbing is dangerous work and you don't want to be replacing antennas more often.

 

[kayn1n32008]

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As far as antennas go, look at companies like DB Products (heavy duty line), Sinclair Radio Labs and Bluewave. Yes they are fairly expensive but if you are going to spend the money on 7/8' hardline, look at buying an antenna that will likely outlast the equipment you are installing.

While all three are designed for extreme mountian top exposure, IMO, Sinclair and Bluewave are a cut above DB. Both Bluewave and Sinclair make antennas that have all cabling that is fully contained inside the mast and elements, rather than having the phasing harnesses zip tied to the antenna mast.

Stay away from ham grade fibreglass antennas, they generate noise, and WILL fail in moderate ice/snow/wind loading. I have seen Diamond/Comet ham grade antennas on mountain tops, mounted beside Stationmasters, that are broken just above the groundplane. Do not cheap out on one of the most important parts of your repeater system.

My company learned the hard way the difference between using 165' of LMR-400 with a crap fibreglass stick versus 165' of hardline and a Bluewave 6DBd 4bay.

We are now replacing the LMR-400 and fibreglass sticks with 1/2" heliax and Bluewave 4-bay exposed dipole arrays at two of the 4 permanent RTK reference stations we operate at two major SAGD projects in northern Alberta. Our origional 2 reference stations at the one project(2 per project) use LMR-400 with 3Dbd fibreglass sticks, we get +/-5km radius of coverage over flat terrain using 30w at 440MHz. Using 1/2" heliax, and a 6Dbd Bluewave @30w (all feed lines are about the same length, we are getting +/-20km radius of coverage, and to the north of one project, where the terrain slopes away we are seeing 60km+. All other factors are similar. Feedline length, transmit power, terrain and antenna elevation. RTK rovers are Trimble R8/R6/5800 with OEM Datalink antennas.

 

[W2PMX]

LDF4-50 has 1.43db loss/100 ft. at 440 MHz and 0.815db loss/100 ft. at 150MHz. I'd still want to keep it as short as possible, both for minimum loss and to keep the price down. If you can mount the radio cabinet(s) just below the antennas, that would be about ideal. Running power, control and audio cables up the tower won't hurt the range, and the price of those cables is minimal compared to heliax.

 

[dksac2]

Get the catalog from DX Engineering, they have all of the 450 ohm line, baluns and can answer your questions. The baluns may be 9 to 1, can't remember, but the guys at DX can answer your questions.

Also, you are limited to 20 feet high on a GMRS antenna or 20' above a building the antenna is mounted to, you cannot put it on top of a 50' tower.

For a high gain UHF antenna, check out L-Com. They have a 9db antenna not more than 3 or 4 feet tall in heavy PVC, it won't break or get hurt by wind or weather. It costs $100.00

John

 

[n5ims]

The 1/2 inch LDF4-50 is affordable, what is the degrade in performance compared to the 7/8"? at 1/2" it seems like it would be easy to make several runs in a 2 1/2 inch conduit.

Size isn't everything in coax. The loss over 200' at 460 MHz for LMR-600 would be about 3.5 dB while the same length and frequency the loss for LDF4-50 would be about 2.9 dB. The smaller cable actually would give you about 0.6 dB lower loss! It will also not have the passive intermod distortion that's an issue with the LMR series of coax when used in duplex (aka repeater) operation. The shield used in the LMR series of coax is an aluminum foil shield covered by a braid of tined copper wire. The two different metals cause the signals going out to mix with those coming in and cause the distortion. There is a special "Low-PID" version of the LMR cables available, but the cost is higher and it isn't very easy to find.

When sizing your conduit, don't forget to factor in the minimum bend radius for the coax you select. If the conduit has bends that use a 3" radius and the coax requires a 6" radius, you may need larger conduit to allow for the necessary bend radius. Using a larger conduit also allows any moisture to flow more easily so it has less of a chance to ruin your coax as well. With little extra room, the surface tension of the moisture will cause it to "stick" on the coax, normally at the worst possible location.

 

[mmckenna]

Here are some pretty handy calculators that will let you select different types of coax so you can do a proper cost/benefit analysis of your feed line:
Welcome to Times Microwave | Coaxial Cable - Attenuation & Power Handling Calculator
or
Coax Calculator if you want to compare some of the cheaper cables, just for kicks.

Listen to the advice above, most of it is right on. Don't skimp on your antenna or feed line, it will make or break your system.
The advice about cable bend radius is important also. The bigger you go in conduit, the bigger the bend radius of the sweeps are. This translates into easier pulling and happier coax. And, as I said earlier, if you are going to open a trench, lay in more conduit than you need. Pipe is cheap, trenching isn't. Figure on a spare run just for coax. Then figure in a separate run of 3/4 or 1" for 110vac power (having a plug near your tower is handy. While you are at it, think about tossing one in for irrigation control and one for water. When I put sprinklers in my back yard, I laid in a 3/4 inch for the irrigation control circuit, then tossed in a 2" for later use. The extra conduit only cost me about $30 extra, but knowing I don't have to dig another 60 foot trench if I want to add something is like money in the bank. Figure that once you have that tower up you'll want to add more antennas down the road. You will, trust me. Scanner, dipole, yagi, FM/TV, etc might come down the road later and being able to pull in a cable in an empty conduit will save you a lot of work.

 

[mmckenna]

Also, you are limited to 20 feet high on a GMRS antenna or 20' above a building the antenna is mounted to, you cannot put it on top of a 50' tower.

Actually, this rule only applies to a "small base station". It doesn't apply to repeaters or a regular base station. This part of the rules is confusing and poorly written. I'd hope, eventually, the FCC will fix the mess that is the GMRS rules.

 

[Logan005]

WoW, almost too much to digest, but is just what I needed to know and more.

Yes I am aware of the 20' restriction on small base stations, But my station is and will be anything but a small base station.

My Motorola repeater is very small and could be mounted in a small environmental enclosure about 30' up the tower.

I do not need 110v at my tower as I have 48volt DC mains from my solar setup. since conduit is cheap i plan to make two 2.5" runs.

I am gonna do a lot of sweet talking to get my partner to allow the tower closer to the front of the house. I chose the spot out back because the tower would be mostly concealed in the canopy of a 35 to 40' tree.

Is there any way to install a linear amplifier near the top of the tower? This way I could adjust my power output from my repeater taking into account the length of cable and and do final amplification from the point of transmission? may also pre amplify the in coming signal?no?

 

[mmckenna]

Is there any way to install a linear amplifier near the top of the tower? This way I could adjust my power output from my repeater taking into account the length of cable and and do final amplification from the point of transmission? may also pre amplify the in coming signal?no?

Yes. Tower top amplifiers are used on the commercial side in some installations. I have a tower top amp on the receive antenna for my 800MHz system to boost incoming signals and it works well.
Tower top amplifiers for the transmit side are available. For a single antenna, they will amplify the outgoing transmission and preamp the receive. For GMRS, you need to read the rules regarding maximum transmitter output. ERP isn't an issue, however. Ham you won't have an issue. These amps are not cheap. The one I purchased for the receive side of my 800MHz system was just above $5000, not including installation.