EM waves don't care if your 175MHz carrier is modulated with analog or digital information. The marketing of 'digital' antennas is just to capitalize on the confusion.
'91 Toyota Pickup
'09 Kawasaki KLR650
'12 Gunnar Rockhound 29
"They say the test of literary power is whether a man can write an inscription. I say, 'Can he name a kitten?'" -- Samuel Butler