FM: height vs. power

[LeighNash]

Last week, we moved our FM tower to a higher spot to increase our coverage.

While we wait for the FCC to review our final paperwork, we are running at 50% of our licensed power.

QUESTION: When we go to full power, what kind of ground can we expect to gain distance-wise? (I've always thought height was what made or broke your signal's ability to travel, and that power was only associated with ability to saturate your coverage area.)

 

[tpt]

If you go to FCC.gov, then to search (up at the top) then to FM query (left hand side) you get a search screen.

Enter your call letters and request FM query (towards the bottom--scroll)

Up will come several listings on your station. One for the present license, one for the construction permit. Below each will be a link for the "service contour map"

This will show you the difference in coverage for the "service area," Especially in hilly terrain, this is not your prime coverage, but is useful for comparison purposes.

As a practical matter, you'll find the added height is helpful in areas that were shadowed with the old antenna.

 

[LeighNash]

> If you go to FCC.gov, then to search (up at the top) then to
> FM query (left hand side) you get a search screen.
>
> Enter your call letters and request FM query (towards the
> bottom--scroll)
>
> Up will come several listings on your station. One for the
> present license, one for the construction permit. Below
> each will be a link for the "service contour map"
>
> This will show you the difference in coverage for the
> "service area," Especially in hilly terrain, this is not
> your prime coverage, but is useful for comparison purposes.
>
> As a practical matter, you'll find the added height is
> helpful in areas that were shadowed with the old antenna.

Thanks, I've done that already as well as checking out radio-locator.com. What each map says, and what the reality appears to be at half power, make me wonder how much improvement to expect when we get the FCC's nod to go to full power.

 

[oldiesstation]

> > If you go to FCC.gov, then to search (up at the top) then
> to
> > FM query (left hand side) you get a search screen.
> >
> > Enter your call letters and request FM query (towards the
> > bottom--scroll)
> >
> > Up will come several listings on your station. One for
> the
> > present license, one for the construction permit. Below
> > each will be a link for the "service contour map"
> >
> > This will show you the difference in coverage for the
> > "service area," Especially in hilly terrain, this is not
> > your prime coverage, but is useful for comparison
> purposes.
> >
> > As a practical matter, you'll find the added height is
> > helpful in areas that were shadowed with the old antenna.
>
> Thanks, I've done that already as well as checking out
> radio-locator.com. What each map says, and what the reality
> appears to be at half power, make me wonder how much
> improvement to expect when we get the FCC's nod to go to
> full power.
> with a good antenna like perhaps ERI you should notice a good improvement ..i will take height over power on full service fm anyday..

 

[the_guy]

> Last week, we moved our FM tower to a higher spot to
> increase our coverage.
>
> While we wait for the FCC to review our final paperwork, we
> are running at 50% of our licensed power.
>
> QUESTION: When we go to full power, what kind of ground can
> we expect to gain distance-wise? (I've always thought
> height was what made or broke your signal's ability to
> travel, and that power was only associated with ability to
> saturate your coverage area.)

Leigh, your question can't be answered, partly because you didn't provide enough clear information.

Assuming that you meant you are on the same leg or same face of the same tower, and only moved your antenna higher, you can immediately expect the following improvement:

Your electric bill will go down.

In theory, your coverage will be exactly the same, at least as far as your coverage map goes. It will be SLIGHTLY better out there for the last cow in the field, but not that you'll notice.

Now the possible exception to this is if your antenna was just way too low to begin with. I've seen them that were 328' HAAT and low to the ground, 100' or so. These really noticeably improved when raised to 200' AGL and the power reduced.

And as the other guy said, if you were sort of behind a hill and grazing it a little, this might help you there. But otherwise, don't plan on much.

And if you moved to a different tower...or a different face or leg.... anything could happen!

 

[LeighNash]

> Leigh, your question can't be answered, partly because you
> didn't provide enough clear information.
>
> Assuming that you meant you are on the same leg or same face
> of the same tower, and only moved your antenna higher, you
> can immediately expect the following improvement:
>
> Your electric bill will go down.
>
> In theory, your coverage will be exactly the same, at least
> as far as your coverage map goes. It will be SLIGHTLY better
> out there for the last cow in the field, but not that you'll
> notice.
>
> Now the possible exception to this is if your antenna was
> just way too low to begin with. I've seen them that were
> 328' HAAT and low to the ground, 100' or so. These really
> noticeably improved when raised to 200' AGL and the power
> reduced.

Thanks for your knowledge! What we did was move ourselves from a low lying area south of the metro northeast to the highest point inside the metro. We're at 1/2 power waiting on the FCC, and I noticed that to the southwest we lost ground. I am curious as to whether we'll make up that ground when we go up to full power, or whether that's a lost cause.
> And as the other guy said, if you were sort of behind a hill
> and grazing it a little, this might help you there. But
> otherwise, don't plan on much.
>
> And if you moved to a different tower...or a different face
> or leg.... anything could happen!
>

 

[k9ez]

> > > If you go to FCC.gov, then to search (up at the top)
> then
> > to
> > > FM query (left hand side) you get a search screen.
> > >
> > > Enter your call letters and request FM query (towards
> the
> > > bottom--scroll)
> > >
> > > Up will come several listings on your station. One for
> > the
> > > present license, one for the construction permit. Below
>
> > > each will be a link for the "service contour map"
> > >
> > > This will show you the difference in coverage for the
> > > "service area," Especially in hilly terrain, this is
> not
> > > your prime coverage, but is useful for comparison
> > purposes.
> > >
> > > As a practical matter, you'll find the added height is
> > > helpful in areas that were shadowed with the old
> antenna.
> >
> > Thanks, I've done that already as well as checking out
> > radio-locator.com. What each map says, and what the
> reality
> > appears to be at half power, make me wonder how much
> > improvement to expect when we get the FCC's nod to go to
> > full power.
> > with a good antenna like perhaps ERI you should notice a
> good improvement ..i will take height over power on full
> service fm anyday..
>


Depends on your market. If you are full of buildings that you need to penetrate, lower antenna with higher output would be a benefit.

 

[THEInsultant]

> > > > If you go to FCC.gov, then to search (up at the top)
> > then
> > > to
> > > > FM query (left hand side) you get a search screen.
> > > >
> > > > Enter your call letters and request FM query (towards
> > the
> > > > bottom--scroll)
> > > >
> > > > Up will come several listings on your station. One
> for
> > > the
> > > > present license, one for the construction permit.
> Below
> >
> > > > each will be a link for the "service contour map"
> > > >
> > > > This will show you the difference in coverage for the
> > > > "service area," Especially in hilly terrain, this is
> > not
> > > > your prime coverage, but is useful for comparison
> > > purposes.
> > > >
> > > > As a practical matter, you'll find the added height is
>
> > > > helpful in areas that were shadowed with the old
> > antenna.
> > >
> > > Thanks, I've done that already as well as checking out
> > > radio-locator.com. What each map says, and what the
> > reality
> > > appears to be at half power, make me wonder how much
> > > improvement to expect when we get the FCC's nod to go to
>
> > > full power.
> > > with a good antenna like perhaps ERI you should notice a
>
> > good improvement ..i will take height over power on full
> > service fm anyday..
> >
>
>
> Depends on your market. If you are full of buildings that
> you need to penetrate, lower antenna with higher output
> would be a benefit.
>

Exactly! Height will generally gain range, but if there's no power you'll be just a car-radio station. Also, keep this in mind. If you are a lower-powered station trying the rimshot game, consider less bays at higher altitude and TPO. (if practical, even a 1 bay!) Tower placement is paramount, so pay to have a study and range-test done. There's only one good antenna in my opinion: The ERI rototiller. There's knock-offs out there now, but why gamble? Buy one with the proper tower placement via a study and you won't be dissapointed.


<P ID="signature">______________
--- THE Insultant ---</P>

 

[kilowatt]

Station in Indy was at 800 feet with a single bay antenna and had horrible multipath. 3 miles out not listenable on 38th street. Power 800 watts.

Gambled to move to a lower height (300 feet) and use a half wave spaced antenna. Multipath gone. Power 3500 watts.

RENT LESS - SIGNAL BETTER

Great improvement within the Metro and didn't loose Muncie. Signal still weak there though.

The mention of 50% power indicates the station is utilizing a directional antenna during Program Test Authority. Wait up to 90 days for full power...possibly longer. Depends on how busy someone is.

Depending on the situation the DA might be a bad move. With a non DA you can legally place the antenna against the tower using a tuned resonant section to add bounce in a certain direction.

As Jack Mullaney has said: Is it good engineering practice? Possibly not but also not illegal because it happens in the real world without studies by accident also. See station with 3 bay against a water tower.

Gain on a 3kw station can be seen as much as 9kw depending on how much bounce you create.

If you went from 3kw to 6kw you might actually see a worse signal at the same location reception wise. On one station a 3 mile North (adding DA and 6kw tpo) move yielded less signal North when compared to the 3kw non DA signal South.

This is because the manufacturers DA pattern was really what they said it would be. Trust their map because they did the measurements.

As much as you might think 3kw would add double power is still only 3db. Bad news...maybe the original isntallation ahd bounce in a specific direction and the gain from the DA is less than the bounce from the original antenna.

On a panel antenna install maps indicated what coverage would be and they were right. Staff didn't get the signal they wanted in location x but kept saying : We're only at half power.

Staff didn't understand RF. Everyone was unhappy that full power didn't make a difference.

Unlike the half full Half empty theory RF addition is less important than line of sight. If there is no signal now at 50% on the DA don't expect a great improvement.

Make plans now based on your current signal.

Hope it all works out well.

> > > > > If you go to FCC.gov, then to search (up at the top)
>
> > > then
> > > > to
> > > > > FM query (left hand side) you get a search screen.
> > > > >
> > > > > Enter your call letters and request FM query
> (towards
> > > the
> > > > > bottom--scroll)
> > > > >
> > > > > Up will come several listings on your station. One
> > for
> > > > the
> > > > > present license, one for the construction permit.
> > Below
> > >
> > > > > each will be a link for the "service contour map"
> > > > >
> > > > > This will show you the difference in coverage for
> the
> > > > > "service area," Especially in hilly terrain, this
> is
> > > not
> > > > > your prime coverage, but is useful for comparison
> > > > purposes.
> > > > >
> > > > > As a practical matter, you'll find the added height
> is
> >
> > > > > helpful in areas that were shadowed with the old
> > > antenna.
> > > >
> > > > Thanks, I've done that already as well as checking out
>
> > > > radio-locator.com. What each map says, and what the
> > > reality
> > > > appears to be at half power, make me wonder how much
> > > > improvement to expect when we get the FCC's nod to go
> to
> >
> > > > full power.
> > > > with a good antenna like perhaps ERI you should notice
> a
> >
> > > good improvement ..i will take height over power on full
>
> > > service fm anyday..
> > >
> >
> >
> > Depends on your market. If you are full of buildings that
>
> > you need to penetrate, lower antenna with higher output
> > would be a benefit.
> >
>
> Exactly! Height will generally gain range, but if there's
> no power you'll be just a car-radio station. Also, keep
> this in mind. If you are a lower-powered station trying the
> rimshot game, consider less bays at higher altitude and TPO.
> (if practical, even a 1 bay!) Tower placement is paramount,
> so pay to have a study and range-test done. There's only one
> good antenna in my opinion: The ERI rototiller. There's
> knock-offs out there now, but why gamble? Buy one with the
> proper tower placement via a study and you won't be
> dissapointed.
>

 

[TXengineer]

> There's only one
> good antenna in my opinion: The ERI rototiller. There's
> knock-offs out there now, but why gamble? Buy one with the
> proper tower placement via a study and you won't be
> dissapointed.
>

The other manufacturers aren't "knocking off" ERI, they are using their own design for FM radiation.

If their antennas had the same "rototiller" design with slight variations, that would make a knock off.

However if you look at a ERI next to a Jampro, Dielectric, Armstrong or Shively, you will see the real difference each has. And each antenna has it's goods and bads, including ERI.

But FM Antennas are like cars... Chevy guys will never buy a ford, nor will a dodge guy buy a chevy. ERI guys wont buy a Jampro, or a Shively guy will never buy an ERI...

 

[the_guy]

> > Now the possible exception to this is if your antenna was
> > just way too low to begin with. I've seen them that were
> > 328' HAAT and low to the ground, 100' or so. These really
> > noticeably improved when raised to 200' AGL and the power
> > reduced.
>
> Thanks for your knowledge! What we did was move ourselves
> from a low lying area south of the metro northeast to the
> highest point inside the metro. We're at 1/2 power waiting
> on the FCC, and I noticed that to the southwest we lost
> ground. I am curious as to whether we'll make up that
> ground when we go up to full power, or whether that's a lost
> cause.


Then it's a whole new ballgame. You probably gained a lot in some areas, and as you said, you lost some in others.

Your signal is pretty much now what it's going to be. What you'll find when you turn the power up is that it will fill in a few of the holes that you may notice now. It may not seem like it goes much farther, but what's there will just seem better..more dense.

Enjoy your new signal.

 

[the_guy]

> >
> > Depends on your market. If you are full of buildings that
>
> > you need to penetrate, lower antenna with higher output
> > would be a benefit.
> >
>
> Exactly! Height will generally gain range, but if there's
> no power you'll be just a car-radio station.


That's an old PD's tale. Radios don't care how much power your transmitter puts out. Radios care about the signal strength they receive.

If you cover the sidewalk outside a building with 1.5 millivolts of signal, and that building attenuates it by 20 Db, you'll have 150 microvolts for your receiver inside. That same building will attenuate by the same amount no matter what you do with antenna height and output power.

In any reasonable configuration, higher antenna/lower power catches up to lower antenna/higher power at a point so close to the tower that it doesn't really matter. They are pretty well identical long before the 3.16 mV contour.

 

[CW]

> Last week, we moved our FM tower to a higher spot to
> increase our coverage.
>
> While we wait for the FCC to review our final paperwork, we
> are running at 50% of our licensed power.
>
> QUESTION: When we go to full power, what kind of ground can
> we expect to gain distance-wise? (I've always thought
> height was what made or broke your signal's ability to
> travel, and that power was only associated with ability to
> saturate your coverage area.)
>
NONE if the FCC catches you..you CANNOT move unless you have a CP in hand..if you moved your xmtr to a new tower or height, you are illegal under Part 73 and can be fined, removed from the air, etc...
What gives you the idea you can run from a new site at half power without the legal paperwork??? What if the FCC DENIES your request or kicks your paperwork back? YOUR LICENSE is what is currently issued..until you have a CP in hand, you LEGALLY cannot be on a different tower or at a new height..PERIOD!

 

[LeighNash]

> NONE if the FCC catches you..you CANNOT move unless you have
> a CP in hand..if you moved your xmtr to a new tower or
> height, you are illegal under Part 73 and can be fined,
> removed from the air, etc...
> What gives you the idea you can run from a new site at half
> power without the legal paperwork??? What if the FCC DENIES
> your request or kicks your paperwork back? YOUR LICENSE is
> what is currently issued..until you have a CP in hand, you
> LEGALLY cannot be on a different tower or at a new
> height..PERIOD!

Friend,

We HAVE the CP . We are operating under Program Test Authority. I was simply curious as to what, if any, improvement we will see once the license is granted and we go to our full legal power.