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8/3/2022

Visible changes include a mass-delete capability and most importantly, most old URLs will no longer work however the new ones should be very stable over time.

1/3/2022

Credible people say that LMS may be missing directional antenna patterns for some stations in Canada and Mexico.
FM allotments are again protected by LPFMs. CDBS is supposedly still the authoritative source for allotments.

5/30/2021

LMS antenna patterns sometimes are rotated incorrectly. Consult the covered construction permit form to determine what's correct, in CDBS if that's where the original lives.
When CDBS station data was moved into LMS, the FCC converted NAD-27 coordinates into NAD-83 coordinates and rounded to the nearest tenth of a second whereas RFree rounded to the nearest 100th of a second. RFree is using the LMS NAD-83 coordinates, so if you have an old station search which matched the FCC data at one time, now it could appear that the FCC station moved up to 5 feet or so.
AM station data is still coming from CDBS, affecting the AM proximity check for 47 CFR 1.30000 compliance under View→Overview. LMS initially didn't provide sufficient AM data, but does now however RFree hasn't caught up. Luckily AM towers don't change fast.
RFree is tracking FM translators from both LMS and CDBS, however LMS did not initially supply data about FM translators' method of signal delivery or upstream station, impairing 73.827 compliance checking. LMS /may/ be providing sufficient information now -- investigation and possible upgrade pending.
RFree is now using NAD-83 coordinates instead of the old NAD-27 coordinates for most purposes -- most particularly for station-to-station distance calculations. This changes the station-to-station distance and in the worst case could artificially produce a short spacing! This is more likely in the West third of the continental US and probably Pacific US islands. NAD-27 coordinates may still be entered at Change-Location-→Latitude-Longitude.
RFree is still using the old FCC 30-second terrain (HAAT) data when it can. There are indications that the LMS LPFM construction-permit application uses GLOBE when you ask it to "Calculate ERP", but the old LPFM form-processing code used FCC-30, and may still do so. Investigation is required to determine which to use in order to best reproduce FCC results.
The helpful fascimile of the CDBS Form 318 is still useful if you're filing an engineering STA in CDBS, but otherwise beware that it (naturally) shows NAD-27 coordinates, and don't copy those into LMS!. Coordinates in both NAD-27 and NAD-83 are visible on the View-→Overview page, and also in both deg-min-sec and fractional degrees, for helpful cut/paste into differently-capable softwares.

You must be logged into forms.PrometheusRadio.org to use RFree. If you are not yet logged in, you will be directed there when you click the login button below.

Please read the following notes before using RFree.

This software is for planning purposes only. The Prometheus Radio Project does not guarantee the accuracy of the information presented in RFree. This information is based on interpretations about the FCC's rules for Low Power FM radio, which are subject to change. Additionally, some known rules are not yet implemented, and there may be errors in the implementation of known rules. Do not use data from RFree when filing an FCC application without confirming your results elsewhere.
The Prometheus Radio Project will not sell, rent, exchange, or otherwise disclose personal data without your permission, but cannot guarantee the privacy and security of any data entered in RFree. Prometheus may disclose bulk data, such as the total number of users, the number of available channels uncovered, or the number of searches performed in a particular zip code.

Recent Changes

2.0pre2 - Feb 2018
- Upper-left summary, for modifications, shows the original and relative distance and channel changes
- Delete/Copy buttons now in Change-Location menu
- Height page can change ERP down to 50%
- Height page dynamically calculates PZ, ERP as antenna height or elevation changes
- Channel Details page format and brevity by default
- Channel Details page allows some dynamic sorting and selection
- Station pair page improved and a bit more mobile friendly
- Lazy evaluation increases speed a little
- GUI changes inside and out
...many undocumented revisions...
1.9pre4 - Dec 2015
- Saved LPFM searches are matched by Station/Applicant Search.
- Saved LPFM searches are present in channel details pages.
- Odd formatting on google maps is fixed.
- LPFM searches copied from CDBS LPFMs now show the minor-modification (6.4km) area on maps where they can be moved.
- The above minor-modification circles on the map are accurate according to the (required) FCC FM distance formula and inaccurate according to all other formulae used by geographic software and the FCC.
1.9pre3 - Oct 2015
- Personal searches are included with More...->Station/Applicant Search and "Details for Frequency"
- Longley-Rice-based clear-signal distances are now shown in addition to those based on the FCC Contour method.
- Interference and service contours are now correct to within 1 meter of the distance as measured by the FCC FM distance formula
  The normal method for calculating a coordinate at a specific azimuth and distance from another coordinate is based on some variation of of a great-circle formula, including the algorithm used by the FCC (see the FCC SPRONG web page. The distance between these two coordinates will not agree with the distance produced by the formula required by the FCC for FM distance measurements, which sometimes produces erroneous results for interference compliance and for maps showing areas to locate based on drawing spacing circles (these latter have not yet been corrected fully).
  
  Correction requires a combination of iterative coordinate correction, and careful consideration of when to convert between NAD83 and NAD27 coordinates.
- NAD coordinate conversion is now done with custom software rather than the PROJ.4 cartographic software. ?>
1.8 - March 2015
- "What-if" frequencies available (expand bottom of frequencies available page)
- Increased precision (shown) of HAAT and PZ
- When viewing CDBS LPFMs, can check if FCC calculated HAAT wrong (see review->overview)
1.7 - After the first FCC MX Tentative Selectee Public Notice
- Many functions available without logging in
- Menu re-structuring and station search page as default
- Can now parse coordinates like 30-30-30 N 30-30-30 S
- Update to new USGS elevation service
- Daily CDBS updates
- Improvements in login/logout processing
1.6 - Immediately after LPFM application window
- Station/applicant listings show application status
- "Late-filed" translator changes now affect channel availability
- More FM allocations are protected
- Estimate which translators and LPFMs might be able to infringe on a particular location/frequency with new menu [Frequency...->Competitors]
- View MX maps and locate LPFM applicants for study and major/minor modification evaluation via menu [more...->LPFM Station Search]
- Using FCC Fortran field strength calculator instead of FCC's C-language one due to inaccuracies in the latter
- On "Availability Map" pages, can disable the spacing circles corresponding with MXed LPFM apps and ungranted singleton apps.
- Check if registration needed for antenna tower with menu [Review...->TOWAIR]
- Find out more about stations via both FCC CDBS Application Search as before, and also by Station Search. When likely, the "318" link also gives rapid access to a local copy of the applicant's "318" form (new LPFM apps only)