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Overlapping FM antennas on towers
- Thread starter tram
- Start date
K
k9ez
Guest
> Can FM antennas be overlapped on towers? How does this
> affect patterns? Does this create more problems than it is
> worth? (i.e., conserving tower space vs. undesired
> interacting effects?). Has this been done (successfully)
> anywhere?
>
Why not just combine the signals onto one antenna?
> affect patterns? Does this create more problems than it is
> worth? (i.e., conserving tower space vs. undesired
> interacting effects?). Has this been done (successfully)
> anywhere?
>
Why not just combine the signals onto one antenna?
R
RadioDoc
Guest
Re: Overlapping FM antennas on towers *DELETED* *DELETED*
Post deleted by RadioDoc
Post deleted by RadioDoc
Without jumping to an astronomically priced panel antenna, most antennas have a bandwith range of about 6 MHz. So trying to combine 90.5 with 105.3 MHz isn't possible. Plus it takes expensive combiners, even if such a broadband antenna could be used.
> > Can FM antennas be overlapped on towers? How does this
> > affect patterns? Does this create more problems than it
> is
> > worth? (i.e., conserving tower space vs. undesired
> > interacting effects?). Has this been done (successfully)
> > anywhere?
> >
>
>
> Why not just combine the signals onto one antenna?
>
> > Can FM antennas be overlapped on towers? How does this
> > affect patterns? Does this create more problems than it
> is
> > worth? (i.e., conserving tower space vs. undesired
> > interacting effects?). Has this been done (successfully)
> > anywhere?
> >
>
>
> Why not just combine the signals onto one antenna?
>
But lining up antennas end-to-end wastes valuable tower space, which may be non-existent. So what would the cons be in simply putting different antennas at the same level, on alternate faces/legs of a tower?
> > Can FM antennas be overlapped on towers? How does this
> > affect patterns? Does this create more problems than it
> is
> > worth? (i.e., conserving tower space vs. undesired
> > interacting effects?). Has this been done (successfully)
> > anywhere?
> >
>
> You can overlap (interleave) FM antennas, but the common
> practice is to "line them up" top to bottom (one ends,
> another begins). K9EZ brought up the other common
> alternative, which is to use a combiner - that allows two
> signals on the same antenna. There are pros and cons to
> both.
>
> > Can FM antennas be overlapped on towers? How does this
> > affect patterns? Does this create more problems than it
> is
> > worth? (i.e., conserving tower space vs. undesired
> > interacting effects?). Has this been done (successfully)
> > anywhere?
> >
>
> You can overlap (interleave) FM antennas, but the common
> practice is to "line them up" top to bottom (one ends,
> another begins). K9EZ brought up the other common
> alternative, which is to use a combiner - that allows two
> signals on the same antenna. There are pros and cons to
> both.
>
R
RadioDoc
Guest
> Can FM antennas be overlapped on towers? How does this
> affect patterns? Does this create more problems than it is
> worth? (i.e., conserving tower space vs. undesired
> interacting effects?). Has this been done (successfully)
> anywhere?
>
Whoops! I went to re-write my post and deleted it! Anyway:
You can interleave antennas, but it would be unusual. Typically there are two ways to "share" space. If you intend on installing a new antenna, you'd buy a broadbanded antenna and combine the all the signals onto that one antenna.
Now, if there is an existing antenna, you can install another one above or below the existing one.
You see both the "master antenna" and "multi-antenna" designs on towers everywhere!<P ID="signature">______________
</P>
> affect patterns? Does this create more problems than it is
> worth? (i.e., conserving tower space vs. undesired
> interacting effects?). Has this been done (successfully)
> anywhere?
>
Whoops! I went to re-write my post and deleted it! Anyway:
You can interleave antennas, but it would be unusual. Typically there are two ways to "share" space. If you intend on installing a new antenna, you'd buy a broadbanded antenna and combine the all the signals onto that one antenna.
Now, if there is an existing antenna, you can install another one above or below the existing one.
You see both the "master antenna" and "multi-antenna" designs on towers everywhere!<P ID="signature">______________
</P>
R
RadioDoc
Guest
> But lining up antennas end-to-end wastes valuable tower
> space, which may be non-existent. So what would the cons be
> in simply putting different antennas at the same level, on
> alternate faces/legs of a tower?
>
> > > Can FM antennas be overlapped on towers? How does this
> > > affect patterns? Does this create more problems than it
>
> > is
> > > worth? (i.e., conserving tower space vs. undesired
> > > interacting effects?). Has this been done
> (successfully)
> > > anywhere?
> > >
> >
> > You can overlap (interleave) FM antennas, but the common
> > practice is to "line them up" top to bottom (one ends,
> > another begins). K9EZ brought up the other common
> > alternative, which is to use a combiner - that allows two
> > signals on the same antenna. There are pros and cons to
> > both.
> >
>
It would affect the pattern a bit, but with the right design, interaction would be kept to a minimum.
You really aren't conserving tower space, however. You are increasing wind-load which could prevent you from adding more to the tower. Plus, you don't gain any coverage by putting them at the same level.
Again, in this situation, a combiner would be called for.<P ID="signature">______________
</P>
> space, which may be non-existent. So what would the cons be
> in simply putting different antennas at the same level, on
> alternate faces/legs of a tower?
>
> > > Can FM antennas be overlapped on towers? How does this
> > > affect patterns? Does this create more problems than it
>
> > is
> > > worth? (i.e., conserving tower space vs. undesired
> > > interacting effects?). Has this been done
> (successfully)
> > > anywhere?
> > >
> >
> > You can overlap (interleave) FM antennas, but the common
> > practice is to "line them up" top to bottom (one ends,
> > another begins). K9EZ brought up the other common
> > alternative, which is to use a combiner - that allows two
> > signals on the same antenna. There are pros and cons to
> > both.
> >
>
It would affect the pattern a bit, but with the right design, interaction would be kept to a minimum.
You really aren't conserving tower space, however. You are increasing wind-load which could prevent you from adding more to the tower. Plus, you don't gain any coverage by putting them at the same level.
Again, in this situation, a combiner would be called for.<P ID="signature">______________
</P>
R
RadioDoc
Guest
> Without jumping to an astronomically priced panel antenna,
> most antennas have a bandwith range of about 6 MHz. So
> trying to combine 90.5 with 105.3 MHz isn't possible. Plus
> it takes expensive combiners, even if such a broadband
> antenna could be used.
>
Yikes! That's a big spread!!
I have done what you are proposing (one antenna on one leg, one antenna on the other) at the same height...though they are both at an aux site and at a relatively low power level, so performance isn't critical. Where those antennas are at, multi-path due to buildings are a bigger problem.<P ID="signature">______________
</P>
> most antennas have a bandwith range of about 6 MHz. So
> trying to combine 90.5 with 105.3 MHz isn't possible. Plus
> it takes expensive combiners, even if such a broadband
> antenna could be used.
>
Yikes! That's a big spread!!
I have done what you are proposing (one antenna on one leg, one antenna on the other) at the same height...though they are both at an aux site and at a relatively low power level, so performance isn't critical. Where those antennas are at, multi-path due to buildings are a bigger problem.<P ID="signature">______________
</P>
> Can FM antennas be overlapped on towers? How does this
> affect patterns? Does this create more problems than it is
> worth? (i.e., conserving tower space vs. undesired
> interacting effects?). Has this been done (successfully)
> anywhere?
A related question: where do stations planning to use a separate antenna for IBOC plan to put it? Given that it has to be between 70%-100% of the height, will stations with short towers (<= 100m) put the auxiliary immediately below the primary? Is anyone planning to interleave them?
> affect patterns? Does this create more problems than it is
> worth? (i.e., conserving tower space vs. undesired
> interacting effects?). Has this been done (successfully)
> anywhere?
A related question: where do stations planning to use a separate antenna for IBOC plan to put it? Given that it has to be between 70%-100% of the height, will stations with short towers (<= 100m) put the auxiliary immediately below the primary? Is anyone planning to interleave them?
R
RadioDoc
Guest
> > Can FM antennas be overlapped on towers? How does this
> > affect patterns? Does this create more problems than it
> is
> > worth? (i.e., conserving tower space vs. undesired
> > interacting effects?). Has this been done (successfully)
> > anywhere?
>
> A related question: where do stations planning to use a
> separate antenna for IBOC plan to put it? Given that it has
> to be between 70%-100% of the height, will stations with
> short towers (
>
Well, there are two types of IBOC/Analog antennas at the moment...interleaved and dual-input. It seems, however, like a lot of stations are opting for the second antenna. If you have the space, it can make sense for redundancy's sake.<P ID="signature">______________
</P>
> > affect patterns? Does this create more problems than it
> is
> > worth? (i.e., conserving tower space vs. undesired
> > interacting effects?). Has this been done (successfully)
> > anywhere?
>
> A related question: where do stations planning to use a
> separate antenna for IBOC plan to put it? Given that it has
> to be between 70%-100% of the height, will stations with
> short towers (
>
Well, there are two types of IBOC/Analog antennas at the moment...interleaved and dual-input. It seems, however, like a lot of stations are opting for the second antenna. If you have the space, it can make sense for redundancy's sake.<P ID="signature">______________
</P>
> I have done what you are proposing (one antenna on one leg,
> one antenna on the other) at the same height...though they
> are both at an aux site and at a relatively low power level,
> so performance isn't critical. Where those antennas are at,
> multi-path due to buildings are a bigger problem.
For some years, Phoenix' 100 kW, 93.3 MHz KDKB and 104.7 MHz KZZP shared the same levels but different sides of a pole mount on a tower on South Mountain, with no apparent distortion of their Jampro and Shively patterns, or other problems. I haven't been to the site for a while, does anyone know if this arrangement was continued? The FCC database seems inconclusive.
> one antenna on the other) at the same height...though they
> are both at an aux site and at a relatively low power level,
> so performance isn't critical. Where those antennas are at,
> multi-path due to buildings are a bigger problem.
For some years, Phoenix' 100 kW, 93.3 MHz KDKB and 104.7 MHz KZZP shared the same levels but different sides of a pole mount on a tower on South Mountain, with no apparent distortion of their Jampro and Shively patterns, or other problems. I haven't been to the site for a while, does anyone know if this arrangement was continued? The FCC database seems inconclusive.
K
k9ez
Guest
Re: Overlapping FM antennas on towers *DELETED* *DELETED*
> Post deleted by RadioDoc
>
<jab jab> Sheeesh who is in control of this board anyways???? :-D
> Post deleted by RadioDoc
>
<jab jab> Sheeesh who is in control of this board anyways???? :-D
R
RadioDoc
Guest
Re: Overlapping FM antennas on towers *DELETED* *DELETED*
> > Post deleted by RadioDoc
> >
>
> Sheeesh who is in control of this board anyways???? :-D
>
If I told you, I'd have to kill you.
Haven't heard you on .82 the past few days...at least I can see you're still alive!
<P ID="signature">______________
</P>
> > Post deleted by RadioDoc
> >
>
> Sheeesh who is in control of this board anyways???? :-D
>
If I told you, I'd have to kill you.
Haven't heard you on .82 the past few days...at least I can see you're still alive!
<P ID="signature">______________</P>
T
TXengineer
Guest
It's being done in Vegas
On one tower
KMXB and KMZQ are both almost at the same level running at 100kW.
I know there are several others up there. Including one TV antenna in the apateur of the radio antenna.
One of the biggest issues you need to do with this type of setup is install filtering to "trap" out the station next door, so you don't get any power leaking back into the transmitter, which would be bad.
On one tower
KMXB and KMZQ are both almost at the same level running at 100kW.
I know there are several others up there. Including one TV antenna in the apateur of the radio antenna.
One of the biggest issues you need to do with this type of setup is install filtering to "trap" out the station next door, so you don't get any power leaking back into the transmitter, which would be bad.
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