You're right! My mistake... Using GPG is still hard for me! I won't have access to the right key to fix this for a few more hours, but the signature should be valid just not ascii armored output.
$ gpg --verify gnuradio-3.7.10.1.tar.gz.asc gnuradio-3.7.10.1.tar.gz
gpg: Signature made Fri 19 Aug 2016 12:16:29 AM EDT using DSA key ID BB8ED9B2
gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0 valid: 2 signed: 1 trust: 0-, 0q, 0n, 0m, 0f, 2u
gpg: depth: 1 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 1f, 0u
gpg: next trustdb check due at 2017-08-27