Co-location of Aux/Backup systems

[mikl73]

What is the point of co-locating your Aux or Backup tx at the same site as your main?

I understand it is cheaper probably but why when a different geographical location would offer much more redundancy

I have always wondered why even bother.

Yes times are different and stations now are in professional office parks and stip malls where a 100ft pole outside would never be permitted.

 

[nmoore6676]

I think it depends on why you want a backup. Since most transmitters are at unattended remote sites and sometimes accessed with difficulty a backup, at least on site, makes sense if and when the main fails. If you are most concerned about staying on during a disaster like a hurricane, flood, tornado or earthquake then an auxiliary at a different site is more important. Obviously in areas of high real estate values, a separate site is probably not practical unless co-siting is available.

After 9-11 a few of the FM's and all of the TV's in New York understood the value of having alternate sites as well.

 

[Countrykev]

Lots of reasons. Two of them I can think off the top of my head.

1. Money. Can't afford rent or cost of two different sites.

2. Aux contour. Some signals are wedged so tight that they can't have an effective backup site anywhere else.

 

[BobOnTheJob]

Lots of reasons. Two of them I can think off the top of my head.

1. Money. Can't afford rent or cost of two different sites.

2. Aux contour. Some signals are wedged so tight that they can't have an effective backup site anywhere else.

Let me add a third...tower crews. When a tower is painted or other tower work is being performed (such as troubleshooting the main antenna), having an aux a couple hundred feet below the main often allows more or less full power operation to continue. This allows the crews to work during the day, when their rates are lower and it's safer for them to be there. Of course, an on site aux offers little protection against tower failure or lack of available power, but from past experience, at least in the big town, you can not have too many antennas, feedlines & transmitters at your disposal...regardless of where they are.

 

[CW]

Lots of reasons. Two of them I can think off the top of my head.

1. Money. Can't afford rent or cost of two different sites.

2. Aux contour. Some signals are wedged so tight that they can't have an effective backup site anywhere else.

Let me add a third...tower crews. When a tower is painted or other tower work is being performed (such as troubleshooting the main antenna), having an aux a couple hundred feet below the main often allows more or less full power operation to continue. This allows the crews to work during the day, when their rates are lower and it's safer for them to be there. Of course, an on site aux offers little protection against tower failure or lack of available power, but from past experience, at least in the big town, you can not have too many antennas, feedlines & transmitters at your disposal...regardless of where they are.

Still not a good idea ....ever seen a rigging line arc when in the RF field of a master antenna?? With say a 2000ft tower, having an aux antenna 200-300 ft down means NO loose cables running through the RF field of the aux antenna..so you get limited in tower work if it gets to be major...(IE: tower crew using gin pole, etc)...Personally, I would take a different site IF possible.....but #1, MONEY is the main reason....Aux contour can be overcome by placing the AUX where it covers a large chunk of the main (I had one aux site that covered as well, if not better, as the main! but then that was also due to the antenna difference...ERI on the aux, Shively on the main.....cough cough; was not my choice...rest of the gear was identical)

 

[LightGuy48]

Still not a good idea ....ever seen a rigging line arc when in the RF field of a master antenna?? With say a 2000ft tower, having an aux antenna 200-300 ft down means NO loose cables running through the RF field of the aux antenna..so you get limited in tower work if it gets to be major...(IE: tower crew using gin pole, etc)...Personally, I would take a different site IF possible.....but #1, MONEY is the main reason....Aux contour can be overcome by placing the AUX where it covers a large chunk of the main (I had one aux site that covered as well, if not better, as the main! but then that was also due to the antenna difference...ERI on the aux, Shively on the main.....cough cough; was not my choice...rest of the gear was identical)

I've seen it done, we had a 9 level panel antenna, the load line was secured through PVC conduit in the area around the panel antenna and the backup antenna. This was done at a master facility with numerous TV stations and four FM's.

Although you still run some risk due to mother nature. We were an unfortunate victim when the tower iced up during a major ice storm, the load line iced up enough to sag into one of the bays doing significant damage to the bay, it had to be replaced and the load line was a loss too. Had it not been for mother nature we would have had no incidents.

Anyway, as I recall a couple of TV antennas and associated transmission line were installed during the entire process while swapping between the main & aux antennas as the crews moved around the tower.

One other benefit to having the main and aux at the same site, if your main tx goes down and you have a coaxial switch or patch bay you can route your aux tx into the main antenna. You might not get the same ERP depending on the TPO of the aux but in many cases you get better coverage than using the aux tx/aux ant depending on the design of the site due to the additional height.

 

[Robert Bass]

Space and cost issues aside, sometimes it's just better to locate everything in the same space, when the risk of problems isn't that high. Our engineers rigged up such a system, that uses the same antenna. I understand someday the aux transmitter will get a separate antenna, that will be located lower on the tower. In theory, that should allow for seamless changeover. Right now to switch the transmitters, you have to obviously turn one of them off before you can turn the other one on. Then there's a delay the automatic switch creates when changing the coax line from one transmitter to another.

Another benefit is that you can control both transmitters with the same remote control system.

R

 

[gettinbyagain]

Robert:
You can use the same remote control system regardless, if you are using the Burk ARC16 or similar. That is what the "B" side of things are for...

 

[Robert Bass]

Robert:
You can use the same remote control system regardless, if you are using the Burk ARC16 or similar. That is what the "B" side of things are for...

What I meant was, you can tie it all together with the same site selection, which is how our engineers designed the system. This way you can make the transmitter change via dialup control, without changing sites. Everything is on the "A" site.

R

 

[CW]

Robert:
You can use the same remote control system regardless, if you are using the Burk ARC16 or similar. That is what the "B" side of things are for...

What I meant was, you can tie it all together with the same site selection, which is how our engineers designed the system. This way you can make the transmitter change via dialup control, without changing sites. Everything is on the "A" site.

R

Some stations have redundant standby transmitters as well as second sites...KLUV, KVIL and KEGL are all dual 816R5 transmitters....with a coax switch.....KHKS and KZPS are the same but have Harris HT35s instead.....so they can swap xmtrs at the Cowboy tower or go to their aux sites on other towers...(which they had to when KHKS tried to sign on at the new site and a 9inch elbow burned through in the combiner room...It was reported you could hear KVIL in the flame; it being the last filter in line before the split of the feeds to the antenna lines)..The poor Continentals were going crazy before the breakers got thrown.....as they switched back and forth (oops, forgot the diode to put the switch controllers in manual once it switched)

 

[Robert Bass]

Some stations have redundant standby transmitters as well as second sites...KLUV, KVIL and KEGL are all dual 816R5 transmitters....with a coax switch.....KHKS and KZPS are the same but have Harris HT35s instead.....so they can swap xmtrs at the Cowboy tower or go to their aux sites on other towers...(which they had to when KHKS tried to sign on at the new site and a 9inch elbow burned through in the combiner room...It was reported you could hear KVIL in the flame; it being the last filter in line before the split of the feeds to the antenna lines)..The poor Continentals were going crazy before the breakers got thrown.....as they switched back and forth (oops, forgot the diode to put the switch controllers in manual once it switched)

Yikes!

R