Some contest sponsors have been sympathetic to this issue and have adapted their contest rules by defining non-contest windows. A non-contest window is a portion of the band in which stations may not solicit contest contacts. However, these can have unexpected, negative side-effects. One such side-effect is that some windows completely prevent some stations from participating since the window may be their only available frequency band. Contesters contend that several HF Amateur radio bands (30 meters, 17 meters, and 12 meters) are completely contest-free by a kind of "gentleman's agreement", and more suitable for those who wish to avoid contest activity completely. Non-contesters counter that these bands are smaller and far less popular than the bands contesters use and that propagation conditions make contacts difficult. Also, 30 meters is a CW/digital-only band which leaves nothing below 17 meters for voice contacts.