Antenna and mast height adjustments, Range Doubled.

[Logan5]

Well the past week as been interesting, It started when I realized that with my feed line lengths I could gain another 6 to 7 feet of antenna height with some adjustments. Since I was running a program on my computer to clone my old hard drive to a new SSD that took 2 whole days, I decided to get on the roof and raise it up. The first time I did this I pushed too hard and pulled the LMR400 out of the N connector. I tested it here locally and it seemed to work fine, but as soon as I got just a few blocks from base I could no longer key it up. then I could not even key it up locally. so I shut it down and decide to redo it from scratch, during the redo I found I had pulled the coax out and was shocked . I was sure I had destroyed the repeater. I went to HOmeDePot and got a 10' conduit of 1" dia. and raised my antenna to the Maximum height. After powering up I had a very clean and clear connection with another user who uses a 7.1 db yagi from several miles away. since I had to pick up a friend at the airport in an hour I figured this would be the best time to test. in previous installations I have never penetrated downtown to the south. as I crossed the river, I was still getting a clear signal and well over halfway to the airport still no problem breaking the squelch. I arrived at the cell phone waiting area removed the truck BNC connector and added my MJF antenna and had a very clear conversation with the previous user on his yagi. seems I did not damage the repeater and I at least doubled my range, maybe better. I have my LMR400 running thru 10' of conduit, I have been told that running coax thru long spans of metal conduit can cause strange things to happen, anyone know more about this? my antenna is easily 33' to the ground plane. it's amazing that 6 feet makes that much difference. 

 

 

[PastorGary]

To the best of my knowledge, the reasons for NOT running long lengths of feedline inside mast or conduit are more mechanical than electrical.  You can not easilly support the weight of the feedline while it is INSIDE a mast pipe. It is best to run it along the outside of the mast. Wrap three layers of high quality electrical tape around the outside of the feedline at 3 foot intervals and THEN use a UV-proof plastic wire tie around the tape and mast to secure the feedline. You can also use a little more tape to cover the wire tie around the mast and feedline for additional secure anti-slip protection. 

 

Where the feedline would enter and exit a mast pipe, there are sharp edges that if not addressed, can cut into the feedline allowing water in or in a worst case scenario, short the shield to the center conductor. A feedline on a sharp angle coming out of or into a mast can compromise the integrity of the feedline outer layer in a matter of weeks.

 

Finally, if you use a feedline with marginal internal (cheap) shielding, and run the feedline inside a mast, that mast will act as shielding itself as well and will un-balance the feedline regarding SWR inside verses outside the mast.  This will not be an issue with Andrew Hardline, Belden RG213 or LMR400 but it is still best not to run the line inside a pipe.

 

 

[Logan5]

Thank you Pastor Gary, I only run Times Micro and Andrew LMR400 with plans to go to LDF 50a minimum when I install the tower. my actual conduit run is about 8 feet and is only for the next month. I did not think of the wire hanging under it's own weight on this install, although I have considered it wile planning my future tower. I wish I was better at making my own cables. I have found I am much better off having them made. This all makes me think a "Mast/tower mounted environmental enclosure" as expensive as it is, as a much better option. some have room for 2 repeaters and even a space for backup battery's. With as short of cable runs as possible the expense would surely be worth it. I would still want a run straight to the garage for experimental antennas and my base station, not sure I can afford 7/8" not sure I will be happy if I only do the 1/2 LDF

[JohnE]

how long of a run are you talking w/tower?

typical line loss for 1/2" hard line is 1.5 dB /100' ,7/8" is 0.8/100'. unless you going over 100' I would stick to 1/2"

http://www.tessco.com/products/displayProductInfo.do?sku=429150&eventPage=1

http://www.tessco.com/products/displayProductInfo.do?sku=471168&eventPage=2

[Logan5]

Yes JohnE, I like the LDF-4 50a and is much less expensive than 7/8", I am actually looking at a tower mounted environmental enclosure. the tower is 48, foot fully erect, if the enclosure is mounted on the tower at eye level, I would only have 45 feet of 1/2" or LMR 400/600? not sure LMR 600 is worth it.. Another member here on the forum offered to let me use his tower, I would put the Motorola FTL675 there, but it's still in the shop. I like the 1/2 also but concerned about what happens when I retract the tower for maintenance, since it doesn't flex well, I will have to be very careful.  

[JohnE]

given a choice between 600 or 1/2" take the 1/2".

have you ever worked w/1/2"? its not as bad as you think but as w/any cable when retracting a tower you have to be careful w/it.

[Logan5]

No sir, I have only worked with 7/8" my tower won't be going up for a few months, I have considered buying 60' of 1/2"  N type terminated to experiment with in the mean time. there are a few good deals on e-bay still need to check with local HAM shop to see what he has, but e-bay is usually half his prices. I still buy a lot of stuff from him, especially if I need it the same day or if I'm already there for something else. I was thinking of a n type barrel lightning arrestor around the tilt over pivot point, when I retract, I disconnect and screw on a dust cap. this way the cable can continue down the tower to the ground, where I would temporarily  guide it into a track or maybe a piece of PVC pipe, very lite bend and should never kink. I am glad to have this time to fully think this whole tower thing out. once erect I hope years go by before I have to retract it again. I will also have several telescoping mast along side the garage for experimental use, shortest feed thru garage wall. I am still waiting on UPS to bring my 10.2 db yagi today. got to go.