I was talking to Paul, GW1PKM the other morning on the way to the station. He was telling me about his super new QTH on a mountainside in Wales and the different antennas he was planning. We talked about 50/70MHz and he mentioned a dual-band design that, actually, I haven't seen advertised for a while. My initial response was a little cautionary as it had a reputation for being someone of a 'rotatable dummy load'.
But surely, having some antenna is better than none at all! Of course! Much better to put an antenna up and make a few contacts as you surely will, than wait for the perfect antenna (which of course, will never come!).
I was reminded of this this morning, trying to work MD6V on 50MHz on my 'compromise' 50/70Mhz vertical. Sure, on this occasion, it didn't work. But 8/10 of the stations I hear I can work with the compromise aerial and at least I'm on the band and generating some activity. It would be great to have a dedicated beam, but that's going to take a bit more organising.
So the message here is: even if you can only get a simple antenna up - do it! At least you'll be on the air.