Don't assume that Portuguese is just like Spanish. Though they are very closely related languages, and a knowledge of Spanish will certainly help you in pronouncing Portuguese, the two languages don't actually sound that much alike. Portuguese shares some idiosyncracies with French, and to anyone unfamiliar with the vocabulary of Romance languages, it's equally likely to sound like Russian.
There are a few differences in the way Portuguese is pronounced by Europeans as opposed to Brazilians, but European pronunciation is generally accepted, even for Brazilian names.
The most distinguishing feature of Portuguese spelling is the use of tildes on vowels (ã), which indicates nasalization. This accounts for the fact that some Portuguese words (e.g. São Paulo) sound like they contain the letter n when they really don't. The tilde occurs most commonly in diphthongs (e.g. ãe, ão, õe), and is sometimes omitted, though it's usually not hard to recognize these diphthongs and infer that the sounds should be nasalized.
Portuguese also uses the acute, grave and circumflex accents (é, è and ê): the grave accent does not indicate stress but the other two do (see below). As for consonants, we have the familiar cedilla (ç), which plays the same role as in French.
Various accent marks may sometimes appear over vowels, which sometimes change their sounds slightly, but the differences are insignificant for radio purposes.
|e (stressed)||ay, as in "say"|
|e (final)||eh, but very short, almost silent (similar to French)|
|o (unstressed)||oo as in "root", but very short, e.g. Sergio = sehr-zhoo|
|u||oo, as in "root"|
Most Portuguese diphthongs follow the same very logical pattern that is followed by Spanish and Italian. The following list includes only the more exotic examples, which tend to involve nasalized vowels, a peculiar feature that Portuguese shares with French. Nasalization is indicated by a tilde over a vowel (or the first letter of a diphthong): this means the sound should be pronounced as though it were followed by an n. In most cases this n is not fully articulated, as in French. As mentioned above, one sometimes sees these diphthongs printed without the tilde, but they're still easy to recognize and should be pronounced the same.
|ae||iy, more or less, e.g. Guiomar Novaes = ghee-yoh-mar noh-viysh|
|ãe||iyn, somewhat like the vowel in the word "pine"|
|ão||own, somewhat like the first half of the word "ounce", e.g. São Paulo = sown pow-lo|
|õe||oyn, somewhat like the vowel in the word "coin"|
For any other vowel combinations you may encounter, it is safe to follow the rules of Spanish or Italian.
The two biggest problems here are s and x. It can be difficult to tell sometimes how to pronounce these two letters in any given situation; the indications below provide hints, but not fixed rules.
|ç||s, as in French|
|ch||sh, as in French, e.g. Chôros = shoh-roosh|
|g [+a,o,u]||g, hard as in "go"|
|g [+e,i]||zh, like the s in "measure" (see also j)|
|gu [+e,i]||g, hard as in "go", e.g. Guiomar Novaes = ghee-oo-mar noh-viysh|
|j||zh, like the s in "measure", as in French|
|lh||ly, e.g. melhor = mehl-yohr (analogous to Spanish ll)|
|ll||l, just like English, NOT like Spanish!|
|-m (final)||silent, but it nasalizes the preceding vowel, e.g. merim = meh-reen|
|nh||ny, e.g. Cunha = koon-yuh (analogous to Spanish ñ)|
|qu [+a,o,ei]||kw, e.g. Costa Sequeira = kohsh-tuh seh-kway-ruh|
|-s (final)||sh (at end of word, before a pause), e.g. Heitor Villa Lobos = hay-tor vee-lah loh-boosh|
|s [+cons]||sh or zh, depending on whether the following consonant is voiced, e.g. sp = shp, sb = zhb|
|-s-||z (in between vowels), e.g. casa = kah-zuh|
|s||s (everywhere else), e.g. senhor = sayn-yohr|
|x-||sh (at beginning of a syllable), e.g. Texeira = teh-shay-ruh|
|x [+cons]||ks, like English|
|-x||s (at end of word)|
|z||z, like English|
|-z (final)||s, or sometimes sh|
The rules for stress are similar to those of Spanish, but not quite as reliable.