Replacing an AM broadcast antenna...

[memories1490]

Hi - our tower got cut in half from Hurricane Dennis (WECM AM 1490 - Milton / Pensacola, FL). I'm fairly new to broadcasting -- so was wondering if anyone had any advice for me on getting a new one installed and or perhaps a temporary antenna?

I'm not sure on who to contact for my area (we're about 15 miles east of Pensacola). We had a 190' unipole antenna -- just replaced supposedly in 1995. Kind of surprised it got taken down. Any recommendations on incorporating new technology into the antenna for enhanced signal or lightning protection?

Thanks,

Michael Pfost
[email protected]

 

[CW]

> Hi - our tower got cut in half from Hurricane Dennis (WECM
> AM 1490 - Milton / Pensacola, FL). I'm fairly new to
> broadcasting -- so was wondering if anyone had any advice
> for me on getting a new one installed and or perhaps a
> temporary antenna?
>
> I'm not sure on who to contact for my area (we're about 15
> miles east of Pensacola). We had a 190' unipole antenna --
> just replaced supposedly in 1995. Kind of surprised it got
> taken down. Any recommendations on incorporating new
> technology into the antenna for enhanced signal or lightning
> protection?
>
> Thanks,
>
> Michael Pfost
> [email protected]

Your unipole would easily be outdone by a series fed radiator....I have seen that too many times and would not use a folded monopole on AM. With AM, any antenna is liable to lightning....a good set of Johnny Balls and something like a Polyphaser in line with the transmission line will be your best bet...

As to best radiator, a 205 degree vertical would be best but you would have to lower your power output ....this would give you the best coverage with less power usage...Why was the unipole put in? Do you have other antennas on the AM tower?

As for a quick replacement, put up some Rohn 45 or 55G...it will get you back on the air.

 

[Les]

> Hi - our tower got cut in half from Hurricane Dennis (WECM
> AM 1490 - Milton / Pensacola, FL). I'm fairly new to
> broadcasting -- so was wondering if anyone had any advice
> for me on getting a new one installed and or perhaps a
> temporary antenna?

Being on 1490 the job is less difficult than it would be
if you were well down the dial. That's where the good news
ends.

I've seen some workable stuff done with erecting a couple
of phone poles and stretching a long wire also with some
wild balloon stuff but never any good lasting results with
the latter.

First thing: DO NOT disturb the wreckage until you've gotten
instructions from your insurance company (you ARE insured???).
To do so might prevent a settlement or delay it incredibly.

190' suggests it was a FOLDED unipole which could complicate
things further. When the insurance questions are answered,
you might want to look at the fiberglass AM antennas made
by a Canadian outfit...Val(something, maybe Valtec? Valpro? Try
a websearch). They might offer, at 1490, about the same
efficiency as your former tower and might well be much quicker
to obtain and have installed. Dunno about relative cost.

I have tended a folded unipole for decades and come to loathe
it with all my heart and soul. It does survive lightning well,
having a grounded base and it's simple to side-mount lots of
revenue producing auxilliaries. Groundwave is pretty nice
but it all pales by comparison to the additional maintenance
and the cost of that maintenance.

Biggest potential problem, though, is gonna be local government.
You need a lawyer who knows about land-use, zoning, etc. in
your area. Quickly before some NIMBY group decides this is a
great time to remove a source of electromagnetic pollution or
"bird killer".

> I'm not sure on who to contact for my area (we're about 15
> miles east of Pensacola). We had a 190' unipole antenna --
> just replaced supposedly in 1995. Kind of surprised it got
> taken down. Any recommendations on incorporating new
> technology into the antenna for enhanced signal or lightning
> protection?

If, for any reason, you want to stay with the design you had,
consider trying to locate whoever installed the tower or
added the folded unipole (if that's what it was) to it.

I'd expect many more replies almost immediately....

 

[Powell]

> Your unipole would easily be outdone by a series fed
> radiator....I have seen that too many times and would not
> use a folded monopole on AM. With AM, any antenna is liable
> to lightning....a good set of Johnny Balls and something
> like a Polyphaser in line with the transmission line will be
> your best bet...
>
> As to best radiator, a 205 degree vertical would be best but
> you would have to lower your power output ....this would
> give you the best coverage with less power usage...Why was
> the unipole put in? Do you have other antennas on the AM
> tower?
>
> As for a quick replacement, put up some Rohn 45 or 55G...it
> will get you back on the air.


Agreed. A dipole cut to the frequency CAN work as a temporary antenna, but a lot of solid state transmitters do not care for this. The older tube type ones will load into a stump. You'll also have to get a STA for the temporary antenna.

Now for the big question. WHY did the antenna come down? During hurricane Hugo only antennas that needed work fell The two giant 2000 foot TV complexes stayed up, though they were in the brunt of the winds. Towers DO require normal maintenence, and if ignored you end up paying to the piper.



Powell
<P ID="signature">______________
NNNN</P>

 

[oldiesstation]

> > Your unipole would easily be outdone by a series fed
> > radiator....I have seen that too many times and would not
> > use a folded monopole on AM. With AM, any antenna is
> liable
> > to lightning....a good set of Johnny Balls and something
> > like a Polyphaser in line with the transmission line will
> be
> > your best bet...
> >
> > As to best radiator, a 205 degree vertical would be best
> but
> > you would have to lower your power output ....this would
> > give you the best coverage with less power usage...Why was
>
> > the unipole put in? Do you have other antennas on the AM
> > tower?
> >
> > As for a quick replacement, put up some Rohn 45 or
> 55G...it
> > will get you back on the air.
>
>
> Agreed. A dipole cut to the frequency CAN work as a
> temporary antenna, but a lot of solid state transmitters do
> not care for this. The older tube type ones will load into a
> stump. You'll also have to get a STA for the temporary
> antenna.
>
> Now for the big question. WHY did the antenna come down?
> During hurricane Hugo only antennas that needed work fell
> The two giant 2000 foot TV complexes stayed up, though they
> were in the brunt of the winds. Towers DO require normal
> maintenence, and if ignored you end up paying to the piper.
> contact some of the engineers in your market that may work for clear channel or cumulus.they should be able to help you.the unipole is a great antenna ,has more bandwidth and higher efficiency than series fed and greater lightning protection.high winds can bring any antenna down, but it does pay to check on the guys and make sure the tension is correct..good luck.
>
>
>
> Powell
>

 

[stevewave]

> > > Your unipole would easily be outdone by a series fed
> > > radiator....I have seen that too many times and would
> not
> > > use a folded monopole on AM. With AM, any antenna is
> > liable
> > > to lightning....a good set of Johnny Balls and something
>
> > > like a Polyphaser in line with the transmission line
> will
> > be
> > > your best bet...
> > >
> > > As to best radiator, a 205 degree vertical would be best
>
> > but
> > > you would have to lower your power output ....this would
>
> > > give you the best coverage with less power usage...Why
> was
> >
> > > the unipole put in? Do you have other antennas on the AM
>
> > > tower?
> > >
> > > As for a quick replacement, put up some Rohn 45 or
> > 55G...it
> > > will get you back on the air.
> >
> >
> > Agreed. A dipole cut to the frequency CAN work as a
> > temporary antenna, but a lot of solid state transmitters
> do
> > not care for this. The older tube type ones will load into
> a
> > stump. You'll also have to get a STA for the temporary
> > antenna.
> >
> > Now for the big question. WHY did the antenna come down?
> > During hurricane Hugo only antennas that needed work fell
> > The two giant 2000 foot TV complexes stayed up, though
> they
> > were in the brunt of the winds. Towers DO require normal
> > maintenence, and if ignored you end up paying to the
> piper.
> > contact some of the engineers in your market that may work
> for clear channel or cumulus.they should be able to help
> you.the unipole is a great antenna ,has more bandwidth and
> higher efficiency than series fed and greater lightning
> protection.high winds can bring any antenna down, but it
> does pay to check on the guys and make sure the tension is
> correct..good luck.
> >
> >
> >
> > Powell
> >
>



I would get a long wire up between two pole or some trees ASAP. That would get you back on the air...

You will need a antenna at least as tall as what you had. You are in an area with some of the worst ground conductivity anywhere. Probably a .5 OR LESS!!!
Don't give up any tower height.

Another thought would be to diplex with somebody close by if possible. That would probably require a complete engineering application etc etc. The local chaneels are so tight that way not be the best idea.

Good luck

Steve

 

[Les]

In FL you're safe....

No ice to go along with the wind.

Here's what happens when you combine ice and wind:

<a target="_blank" href=http://www.knom.org/static/474/unipolebreak.jpg>http://www.knom.org/static/474/unipolebreak.jpg</a>

Wanna guess what it costs to have one of these fixed each
winter?

 

[DonPerkins]

You should contact Bill Sitzman at IBC Communications ASAP (607)273-2970. He knows all about this issue. I have a client that's running on a TSA with a T-Wire antenna he designed. Bill's the expert on AM Engineering design and knows people at the FCC who can help.

 

[dbdigital]

> things further. When the insurance questions are answered,
> you might want to look at the fiberglass AM antennas made
> by a Canadian outfit...Val(something, maybe Valtec? Valpro?
> Try
> a websearch). They might offer, at 1490, about the same
> efficiency as your former tower and might well be much
> quicker
> to obtain and have installed. Dunno about relative cost.
>

The antenna mfr. in question is Valcom. They make fiberglass, free-standing antennas. http://www.valcom-guelph.com/Guelph/products/AM/default.htm

It seemed to me the 75' version costs about 15K. Their antennas use a special "grid" style ground radial system. The wind load is about 150 mph and, if I remember correctly, has a 5 kw max power rating.

You might also want to look at the LBA TGR-50 which is a portable MW antenna.
LBA technology rents these just for emergencies such as yours.

db

 

[CW]

> contact some of the engineers in your market that may work
> for clear channel or cumulus.they should be able to help
> you.the unipole is a great antenna ,has more bandwidth and
> higher efficiency than series fed and greater lightning
> protection.high winds can bring any antenna down, but it
> does pay to check on the guys and make sure the tension is
> correct..good luck.

You must be a salesman of these monopoles....but your facts are WRONG!!!
Folded monopoles are NOT wider in bandwidth NOR do they have higher radiation efficiency....I have seen stations that run a series fed go to a grounded folded monopole and their range sucked after that......it is a well known FACT that radiation from a grounded monopole is less than a 1.4wave series fed...