Since I know very little about towers and antennas, I was wondering.... does the hardline connect directly to the antenna, or is it connected from the hardline to the antenna via a short piece jumper of coax?
Thank you, and please be nice.
Let's all watch Jonathan ask a stupid question...
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Jonathan KC8RYW
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Let's all watch Jonathan ask a stupid question...
73 DE KC8RYW
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IMHO...
most towers around here use hardline jumpers made from either 1/2 inch hardline or 1/2 inch superflex hardline. (i use 1/2 inch superflex)
reasoning:
tower and antenna flexure can loosen the connection if it's mated directly to the hardline since any motion of the tower will make the hardline move, something has to give.... usually the hardline connector.
my .02
doug
reasoning:
tower and antenna flexure can loosen the connection if it's mated directly to the hardline since any motion of the tower will make the hardline move, something has to give.... usually the hardline connector.
my .02
doug
Re: IMHO...
I agree. This also makes it easer when you ever have to put a wattmeter in there.batdude wrote:
reasoning:
tower and antenna flexure can loosen the connection if it's mated directly to the hardline since any motion of the tower will make the hardline move, something has to give.... usually the hardline connector.
my .02
doug
And since a lot of antennas already have a pigtail coming out of them there is no harm in adding a small jumper to the models that do not have a pigtail. It also makes installation a lot easier when large diameter hardline is used or the antenna is not directly in line with tower.
Nand.
question
The only stupid question is the once you didnt ask!!!! Dont be afraid to ask if you dont know!!
In more clarification for you Jon... (If it doesn't confuse you more!). I took a drive today (In the rain no less!) to a local RF mountain and took a quick survey of how it was done. Of the 70 some odd antennas I counted about 30 were connected directly to the hardline. the rest were connected with a jumper of somesort. So there are some informal numbers for you... btw, the State and County ones were all done with jumpers. Didn't look like different coax, but there was a female/female connector in there right before the coax left the main tower and went out on the arm a bit to the antennas.
-Robert F.
KG6EAQ
KG6EAQ
Not a stupid question, but a serious one. That is a potential problem area for cable/connector trouble. You should see just how much the tower and antennas flex and move in the wind, then add some ice loading too.
Most antennas have either a type N or a 7/8 connector mounted in the bottom and can be directly connected to the feedline without a jumper to reduce connector losses.
Be sure to leave a service / slack loop in the cable to allow for antenna and tower movement. The larger 7/8ths and up feed line, Heliax, cables are just too big to have any flex and a jumper is used to reduce the strain or flex on the antenna connector.
Most antennas have either a type N or a 7/8 connector mounted in the bottom and can be directly connected to the feedline without a jumper to reduce connector losses.
Be sure to leave a service / slack loop in the cable to allow for antenna and tower movement. The larger 7/8ths and up feed line, Heliax, cables are just too big to have any flex and a jumper is used to reduce the strain or flex on the antenna connector.
All the public safety, comercial and cellualr antennas I have worked on have jumpers installed. Like a couple of comment on here, the jumper makes it easy to measure forward and reflected power at the antenna base. Jumpers are normally used to take any strain off the antenna connector by the main feed coax cable.
If the antenna is replaced, even if there is a flex piece at the bottom of it, I have never seen the length of the old antenna cable come out the same as the new one. So your better off just installing a short jumper to be able to make up for any length difference between the old antenna and the new. If you make a single loop, then not only does this give you the variable length, but also makes a choke for the lightning.
I have always seen female connectors used as a standard on the end of the main feed line. This way the tower crew knows what to expect for connectors. Another reason, if you have ever over tightened a connector and sprung the outter collar off of a male fitting, you will know what I am talking about. You can't repair them and expect them to hold. They will pop off again.
It is near impossible to replace a large coax connector on a tower by yourself. If some fool used a male connector on the end of the feed line and you BROKE it, your SOL. You now have to replace the connector. You probably don't have one with you and probably don't have one in the shop.
If you use male connectors on the end of the jumper cables, they can be replaced on the ground and they are also much cheaper. Almost every tower crew I have seen carries spare 1/2 inch male connectors. There is always some 1/2 inch cable on the truck.
With the 7/8 cable and 1 5/8 cable, not every tower crew keeps these as spares on their truck. There are crews that put these on almost every day and then may have one. But they are expensive and take up space. It's easy to loose parts if the box gets busted open.
Jim
If the antenna is replaced, even if there is a flex piece at the bottom of it, I have never seen the length of the old antenna cable come out the same as the new one. So your better off just installing a short jumper to be able to make up for any length difference between the old antenna and the new. If you make a single loop, then not only does this give you the variable length, but also makes a choke for the lightning.
I have always seen female connectors used as a standard on the end of the main feed line. This way the tower crew knows what to expect for connectors. Another reason, if you have ever over tightened a connector and sprung the outter collar off of a male fitting, you will know what I am talking about. You can't repair them and expect them to hold. They will pop off again.
It is near impossible to replace a large coax connector on a tower by yourself. If some fool used a male connector on the end of the feed line and you BROKE it, your SOL. You now have to replace the connector. You probably don't have one with you and probably don't have one in the shop.
If you use male connectors on the end of the jumper cables, they can be replaced on the ground and they are also much cheaper. Almost every tower crew I have seen carries spare 1/2 inch male connectors. There is always some 1/2 inch cable on the truck.
With the 7/8 cable and 1 5/8 cable, not every tower crew keeps these as spares on their truck. There are crews that put these on almost every day and then may have one. But they are expensive and take up space. It's easy to loose parts if the box gets busted open.
Jim