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In the USA, is there a way to find locations of VHF transmitters that are used for air traffic communication, and the frequencies they transmit/receive on? There are some places (Northern Bay Area, CA) where I fly where I have good signal/communication with a Terminal Radar facility, but have trouble contacting area approach in the same area - especially when low (<2000ft AGL). The area is hilly.

I'm interesting in seeing range and altitude support for a given frequency (in a given area).

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    $\begingroup$ I'm not sure how you are going to get that information. VHF is line-of-sight and is affected by terrain. It doesn't really depend on the frequency, but the terrain between you and the transmitter and if the transmitter is shadowed by terrain. $\endgroup$
    – Ron Beyer
    Commented Apr 28, 2016 at 17:10
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    $\begingroup$ I commute from KRDD to KCCR almost every week. The RCO are located on a sectional (so you know the locations). On Monday mornings it is not unusual for Oakland to ask people how well they hear various outlets. I don't remember promises about radio coverage except for MEA/MCA on IFR sectionals. Sorry. $\endgroup$
    – guycole
    Commented Apr 28, 2016 at 17:34
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    $\begingroup$ Looks like FAA used to publish this info but they discontinued it (security reasons?). This doesn't have frequencies, just locations. $\endgroup$
    – TomMcW
    Commented Apr 28, 2016 at 18:04
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    $\begingroup$ This is a useful site (radioreference.com/apps/db/?rpt=6&aid=2236), and the locations of these match up with the RCO locations on the sectional . Seems Mt Tamalpais RCAG is the one that applies to my area. The list seems a little out of date, however, as the location of "Priest - RCAG" doesn't have anything on the sectional, or in Google Maps. $\endgroup$
    – CJBS
    Commented Apr 28, 2016 at 19:31
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    $\begingroup$ @RonBeyer: (just an addition) "VHF is line-of-sight", that's true overall indeed. However on short distances like in the case here, diffraction and reflection can play an important role and make links possible using broken lines and multiple paths. Else in a city nobody would receive FM radio or aerial TV. On the other hand, the volume that must be kept clear is the innermost volume of the Fresnel zone, because energy propagation is not only along a line. Bottom line... it's a complex calculation! $\endgroup$
    – mins
    Commented Apr 30, 2016 at 15:29

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This is a useful site for the Oakland (ZOA) Air Route Traffic Control Center (ARTCC), and the locations of these match up with the RCO locations on the sectional. It seems Mt Tamalpais RCAG is the one that applies to my area. The list seems a little out of date, however, as the location of "Priest - RCAG" doesn't have anything on the sectional, or in Google Maps.

Further, there is an FAA site depicting RCOs and frequencies for Alaska.

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Upper VHF is essentially line of sight it is affected and reflected by both to Terrain and by building structures it will Imperfectly penetrate concrete and steel structures. It doesn't have much over the horizon capability.

UHF has better building Penetration, but no over the horizon capabilities.

Range for both is affected by three things 1)Antenna Type/height of the source and its 2)Power and 3)receiver location and orientation.

Under specific Atmospheric conditions, typically a temperature inversion, Tropospheric ducting can occur where RF is reflected further than its normal transmission range and achieve significant over the horizon capabilities. Conceivably this can disrupt local operations.

Essentially the higher you go in Frequency the more line of sight the signal is. Also more power is needed to maintain an equivalent range or the more sensitive a receiver needs to be.

Also sheets of metal will affect all frequency ranges somewhat. This is why the antenna needs to be outside the aircraft or vehicle.

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    $\begingroup$ Whilst this is useful background information on VHF transmissions (+1), the question is with regard to where transmitter locations are. As mentioned in the question, in a given location there are some facilities that I can communicate with easily, while others require being quite high to avoid signal obstruction from hills. Hence wanting a map of frequency/facility transmitter locations. $\endgroup$
    – CJBS
    Commented Feb 24, 2017 at 16:59
  • $\begingroup$ @cjbs if I didn't already see it in the below answer the location to the radio beacons are actually marked on your sectional map where they are. The actual transmitters for The Voice Communications are going to be located someplace on the airport property and that would be where you would determine your line of sight from. You would want to look for a few masts with vertical antennas. Separated by 30-40 feet. $\endgroup$
    – Rowan Hawkins
    Commented Feb 24, 2017 at 17:07
  • $\begingroup$ @cjbs because the frequency ranges are close enough you could probably use any applications for amateur radio 2m(144mhz) propagation mapping for the 120mhz air band. The one thing I've learned from all of my other RF experience however is that any mapping application is of limited use and probably wouldn't tell you anything you haven't figured out by flying around in the area. $\endgroup$
    – Rowan Hawkins
    Commented Feb 24, 2017 at 17:16
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    $\begingroup$ @Rowan_Hawkins - this might be true of airports, but that's not my problem. My problem is mostly with approach control. That's certainly not on the sectional - the dark magenta box I'm seeing says "CTC NORCAL APP WITHIN 20 NM ON 127.0 298.95"; no transmitter info included ... skyvector.com/… $\endgroup$
    – CJBS
    Commented Feb 24, 2017 at 22:14

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