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Old 09-05-2014, 10:59 AM
fisherman50 fisherman50 is offline
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I am in the process of a wiring a tower. For UHF/VHF I am using LMR 400 and for HF using 213U coax. As you know, both are pretty stiff and somewhat hard to manage.

My question is... is it reasonable to use a shorter and more flexible type coax jumper to wire the area around the antenna/rotor. If yes, can you suggest a type coax and connector, if different from PL-259.

Thanks
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Old 09-05-2014, 11:57 AM
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RG58U is popular, though you'll take a hit in power from the extra connectors. LMR400 can be bent on a 4 inch radius repeatedly, and a 1 inch radius if you only do it once (http://www.ame-hft.de/pdf/lmr400.pdf.) I haven't played with 213u, but since it's basically a higher loss version of LMR400 I'd imagine it would be similar. To keep things simple you may almost want to just use LMR400 for the whole thing, unless you're dealing with 400' of tower.
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Old 09-05-2014, 04:04 PM
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On my LMR-400 runs I typically use RG-214 or 213 from the rotor loop up. You can use LMR-400 Ultraflex, but I have spools of RG-214, so that is my choice

T!
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Old 09-06-2014, 11:46 AM
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Just use LMR 400 Ultra Flex and call it a day.
It has all the great qualities of standard stuff LMR400 but it is the flex style.

Times microwave is the best.



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Old 09-06-2014, 06:06 PM
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Be careful using tight bends in hot climates or where the summers are hotter than 85~90 degrees. What happens in a tight bend that's exposed to scalding hot sunlight is that your center conductor will gradually migrate outward. It's unlikely it would ever become shorted, but what happens is you wind up having a major impedance "lump" (mismatch) through the bend. This is another reason NOT to use superflex except for applications like making a short SWR meter jumper.

Similarly, when fastening your coax to the leg of the tower or mast, use black electrical tape, not ty-wraps. Neither ty-wraps nor staples should ever be used with coaxial cable of any type. Never-ever. Ty-wraps are only OK as long as they are not cinched down tight.

Show me a 100' length of any RGxx (including TV coax) that's been cinched-down to a tower leg for a year or longer using ty-wraps and I can show you a TDR scope sweep on which we can see small impedance bumps where every ty-wrap is located. Use Ty-wraps (and staples) on anything but coax.
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Old 09-08-2014, 07:11 PM
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Thanks everyone for the helpful comments.
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Old 09-12-2014, 06:34 PM
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Sorry, forgot to mention that for HF operation RG58 is fine for use on frequencies below 30 Mhz with transmitter power not exceeding 250 watts. Yes, there is still some loss, but below 30 Mhz it is minimal and below 15 Mhz it is mostly negligible. I would not hesitate to use it on 160, 80, 60, 40, 30, 20 or even 17 meters. On 10 meters I would prefer RG213, but RG58 would still be fine.

Even on 146 Mhz you can get by with short runs (i.e., 25 feet or less) of RG58. (i.e., typical mobile installations)
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Old 09-13-2014, 08:25 PM
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I use lmr-400 flex in the shack. It works great indoors.
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Old 09-21-2014, 08:11 PM
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For short (3 ft to 6 ft) jumpers, I use RG-8X, which is only slightly larger than RG-58, and had much lower loss. My longest antenna coax run is about thirty feet, and for HF, and that short distance, there is very little loss difference between RG-8X and RG-213.
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Old 09-21-2014, 09:27 PM
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Type N connectors are often used with a tower. Perhaps the Type N connector handles more watts, perhaps is more weatherproof, perhaps easier to fit to the larger diameter coax, or, all of the above.

I do QRP.
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Old 09-22-2014, 11:03 AM
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Quote:
Originally Posted by ConnieD View Post
Type N connectors are often used with a tower. Perhaps the Type N connector handles more watts, perhaps is more weatherproof, perhaps easier to fit to the larger diameter coax, or, all of the above.
If you are going to the expense and effort of putting up a tower, then why not get every little advantage you can.

Type N connectors can handle higher peak powers than UHF connectors, however the smaller diameter center pin means they can (repeat can, not will) heat up and break down quicker with high average power. Realistically either UHF or N type will handle legal limit HF SSB operation, but the advantage of one over the other is more likely to be seen in legal limit HF CW operation. If you really want high power operation with fewest issues neither N type nor UHF are the way to go, there are several better options on the market, SC, 7/16 DIN, etc.

Type N connectors, when properly assembled and installed, are more weather resistant than UHF connectors. However, who puts up a tower and coax without a bit of Coax Seal or similar stuff? Once you use a sealing tape like that the native weather proofing of the connector is almost a moot point.

Fitment depends on the cable. As you said, N types can be found in the correct form factor and fitted to larger cable more easily. But if you are talking LMR-400 class cable the UHF connector is typically easier to apply for the average installer. Don’t get me wrong, N types are not hard to install at all, and once you learn to do it they go on as fast and easy as UHF, but to the new or inexperienced installer UHF is typically easier.

So selection of UHF or N is up to the user with no or little in the way of advantages for either…at 2 meters and below. Above that frequency the N type picks up several performance advantages.

The main issue with the UHF connector is…it isn’t. The thing we call a “UHF” connector today was not designed for what we would now call UHF applications. The original design spec was for an upper frequency limit of 300 MHz, and that is indeed UHF, but it is the very bottom edge of the UHF band. There is argument that it was originally developed for radar applications, I have not been able to confirm that but it was used extensively in both the IF path and video sections of early radars, all the way up into the 1960’s. I saw them used in everything from the SCR-584 (operational 1943) to the Nike-Herc (used until the 1980’s) radars. Typically the final IF of radar is less than 150 MHz, with 70, 60, 35, and 30 MHz being very common. The important thing here is that even if it was made for radar, it was probably (almost certainly) not made for the RF path of any radar.

UHF connectors can start to have very significant insertion loss and SWR issues above 150 MHz when compared to N type. Some people will say this issue starts above 50 MHz.

Bottom line, for home / base applications I use UHF connectors 6 meters and down in frequency, and N type above 6 meters. For FM mobile use I might push UHF connectors up to 70cm if forced to. A lot of mobiles come with a UHF connector on them for 70cm, and the small advantage of N type just is not worth changing the connector out (if that is the only connector in the system). For weak signal 70cm work I always opt for N type.

T!
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Old 09-22-2014, 11:49 AM
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I stayed with the pl259/so259 on lmr400, for jumpers I use lmr400 flex. Yes overkill to the max on HF, but adequate for UHF.

As was previously stated, N type is probably going to be better for your shorter wave length loss worries.

Fyi I'm only running 100 watts all mode 160-6, and 50watts 2m & 70cm.
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Old 09-24-2014, 09:12 PM
MontanaMEL MontanaMEL is offline
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FWIW:
I agree with the PL259 up to 6m, FOR RUNS OVER 50ft long...or, with QRO power levels.
And, the Type-N for all above, until you are in wave guide land...Ghz.

However, for high power EME 2m OR for any use at 70cm (440 band), I would really look at LMR-600 or hardline. Those losses can really mount up quick and you have all that money invested in that tower/antenna array to start... don't screw around...

The UF version of BOTH LMR-400 & 600 uses a stranded center conductor - hence the flex use without work hardening. RG-213 is stranded as well.
I have found the most bang for your buck on these LMR type coax is from AIR802_dot_com ... They can put ANY end on them you want...good workmanship too.

For true QRO/1.5KW at the driven element(s) on EME duty...Hard line is the only way to go, with 7/16 DIN connections...ask W7GJ ... or see his web page, why.

AND...the comment on using tie's...dead on.... Use Super 88 tape and cut it off, no tearing allowed. Remember to figure those coax runs in your wind ratings WITH ICE loads when you spec the tower size itself... 1/2" of ice will crumple most R25G when wind is added.. YMMV... 73
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Old 02-11-2020, 12:06 PM
Okey3000 Okey3000 is offline
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As most readers suggested….. settle for an LMR 400 Ultra Flex. Here is a link to a top manufacturer’s LMR 400 Ultra-flex page https://www.awcwire.com/productspec....nications-coax
Cheers
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Old 02-11-2020, 12:08 PM
Okey3000 Okey3000 is offline
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Quote:
Originally Posted by fisherman50 View Post
I am in the process of a wiring a tower. For UHF/VHF I am using LMR 400 and for HF using 213U coax. As you know, both are pretty stiff and somewhat hard to manage.

My question is... is it reasonable to use a shorter and more flexible type coax jumper to wire the area around the antenna/rotor. If yes, can you suggest a type coax and connector, if different from PL-259.

Thanks
As most readers suggested….. settle for an LMR 400 Ultra Flex. Here is a link to a top manufacturer’s LMR 400 Ultra-flex page https://www.awcwire.com/productspec....nications-coax
Cheers
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Old 02-11-2020, 03:16 PM
Okey3000 Okey3000 is offline
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Quote:
Originally Posted by fisherman50 View Post
I am in the process of a wiring a tower. For UHF/VHF I am using LMR 400 and for HF using 213U coax. As you know, both are pretty stiff and somewhat hard to manage.

My question is... is it reasonable to use a shorter and more flexible type coax jumper to wire the area around the antenna/rotor. If yes, can you suggest a type coax and connector, if different from PL-259.

Thanks
As most readers suggested, settle for an LMR 400 Ultra Flex. Here is link to a top manufacturer’s LMR 400 Ultra flex page https://www.awcwire.com/productspec....nications-coax
Cheers
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Old 02-11-2020, 03:23 PM
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Quote:
Originally Posted by Cap'n Preshoot View Post

Similarly, when fastening your coax to the leg of the tower or mast, use black electrical tape, not ty-wraps. Neither ty-wraps nor staples should ever be used with coaxial cable of any type. Never-ever. Ty-wraps are only OK as long as they are not cinched down tight.

Show me a 100' length of any RGxx (including TV coax) that's been cinched-down to a tower leg for a year or longer using ty-wraps and I can show you a TDR scope sweep on which we can see small impedance bumps where every ty-wrap is located. Use Ty-wraps (and staples) on anything but coax.

Fascinating! Thanks for sharing. How long will black electrical tape last before needing to be replaced?
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Old 02-14-2020, 02:24 AM
country_boy country_boy is offline
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Quote:
Originally Posted by AlgoRhythms View Post
Fascinating! Thanks for sharing. How long will black electrical tape last before needing to be replaced?
Scotch 88 or scotch 33 will last for 15 + years in the south east. The outermost layer will fail in all respects except shielding the layer underneath from UV. The Layers underneath will still insulate or seal or hold. Scotch 88 is the standard for the telecom industry- it’s slightly thicker than 33.

I wouldn’t be scared of cable ties, just watch the tension, and use a wide tie. A few guys wrap the cables with rubber ( black gasket rubber), or a few laps of 33 both to cushion the tie, and increase friction. But it doesn’t seem to be a problem skipping this step. And remember LMR series isn’t as crush resistant as RG8/214/213.

We have LMR on a while bunch of fold over poles, and check them yearly with a site master.
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