Finding good portable operating sites historically relied on local knowledge, anecdotal evidence from other amateurs, plenty of experimentation and a good dose of luck. Whilst there's nothing wrong with this approach it does rely on either knowing the local area well, or having contact with someone who does. This isn't always available, for example holiday operation, moving to a new area or simply that all the good peaks have been taken. There must be a better way...

My approach to finding new hilltops to activate involves finding candidate hilltops, assessing whether operation is possible from that location, and then working out whether it's worth the effort of attempting to activate it. These are some of the resources I use to do this.

Find Candidate Sites

Overpass Turbo

Overpass Turbo allows users to run scripts against the Overpass API, part of the OpenStreetMap project. The script below finds ways, nodes and relationships (i.e. any object) with an elevation greater than 300m a.s.l (which works well for the area I'm interested in, depending on your local area you might need to change this). It then searches the area around those objects up to a radius to 100m (you can tune this too, if you need to) to see if there are any highways, but excluding footpaths, bridleways, tracks, service roads, unclassified roads etc. This theoretically returns a list/map of summits which are accessible by car.

[out:json][timeout:800];
(
  way({{bbox}})(if:t["ele"] > 300);
  node({{bbox}})(if:t["ele"] > 300);
  rel({{bbox}})(if:t["ele"] > 300);
)->.summits;

way
  (around.summits:100)
  [highway]
  [highway!~"^(footway|path|bridleway|track|unclassified|cycleway|service)$"]
->.streets;

(
  node.summits(around.streets:100);
  way.summits(around.streets:100);
  rel.summits(around.streets:100);
)->.matchingSummits;

(.matchingSummits; .streets;);
out geom;

UKACMap

UKACMap queries the Google Maps API to try to find the highest point in view. In some ways this is more reliable that the OverPass API approach as the Google Maps elevation data comes from surveys rather than user-entered data, however there are limitations in how many times the Google Maps API can be queried, so the application is not as accurate as it could be.

Assess Accessability

• Is the land privately owned?
• Is it possible to get a vehicle to the site?
• Are there time restrictions (for example a car park that closes at dusk)?
• Is there sufficient space to set up antennas?

The answers to many of these questions can be found using online mapping services including Bing Maps which has Ordnance Survey maps available and Google Maps which has aerial photography and also Google's fantastic Street View service.

Assess Radio Coverage

Of cource there's no point investing time and energy into climbing a peak is it's not going to give you the coverage you need. Radio Mobile Online (and also the offline version) and Splat! are fantastic tools for assessing a site's radio coverage. Their use cannot be described briefly here but there are plenty of tutorials available. One I particularly like for Radio Mobile's offline versions can be found here