[Scan-DC] Antenna pattern for DCA @ 119.1 MHz?

[Albert LaFrance]

Some years ago I came across a little FAA radio facility of some kind, with
two short towers, tucked away in a South Arlington residential neighborhood
near DCA:
<https://goo.gl/maps/VF2SP>

Albert

> -----Original Message-----
> From: Scan-DC [mailto:scan-dc-bounces at mailman.qth.net] On Behalf Of
> djoneses
> Sent: Monday, December 08, 2014 10:36 AM
> To: 'Andrew Clegg'; 'Scan-DC at mailman.qth.net'
> Subject: Re: [Scan-DC] Antenna pattern for DCA @ 119.1 MHz?
> 
> Andy:
> 
> Although I do not know the exact answer to your question, my thought has
> all been that the 119.1 tower frequency transmitter is not located at DCA.
> And since the controllers have the ability to select transmitter sites,
they may
> choose a different transmitter site based on traffic direction.
> Additionally there probably is some antenna uptilt. -- could be very minor
> only a few degrees -- but combined with the antenna location, this results
in
> a weak signal
> 
> On the other hand, the helo transmitter site may be local to DCA and the
> antenna may have a truer horizontal pattern since it only needs to serve
> aircraft at relatively low altitudes (compared to approaching fixed wing
> aircraft) and in the local area.
> 
> I often wondered if the 119.1 tower transmitter is not located at the FAA
Falls
> Church site.  Maybe a little foxhunting is in order.
> 
> David
> 
> -----Original Message-----
> From: Scan-DC [mailto:scan-dc-bounces at mailman.qth.net] On Behalf Of
> Andrew Clegg
> Sent: Monday, December 08, 2014 9:57 AM
> To: Scan-DC at mailman.qth.net
> Subject: [Scan-DC] Antenna pattern for DCA @ 119.1 MHz?
> 
> I've noticed that the 119.1 MHz tower frequency from DCA is surprisingly
> weak. I can barely hear the tower 4 miles away from a rooftop up 220 ft.
> Even in the parking lot at Gravelly Point, the signal isn't exactly
gangbusters.
> The planes come in fine at both. On the other hand, the 134.35 MHz
> simulcast frequency that the tower uses to communicate with helicopters
> comes in loud and clear 4 miles away, and the 257.6 MHz simulcast channel
in
> the milair band comes in reasonably well too.
> Does someone on the list know if by chance the 119.1 MHz DCA antenna has
> a significant electrical uptilt that keeps the pattern along the horizon
very
> low? That would seem odd, because even ~10 miles away, where the tower
> first starts communicating with inbound planes, the planes are at a
relatively
> low elevation as seen from the airport. But I can't seem to figure out why
> 119.1 is so weak. Maybe the 119.1 antenna on the southeast side of the
> tower and blocked to the west (where I am) and the north (where Gravelly
> Point is)?
> That would seem odd too.
> Any ideas? This has puzzled me for several years.
> 73,Andy
> 
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