(Apologies if this is not suited for this forum... Technically it's broadcast gear but it doesn't really fall into the same class as the types of things discussed there and I figured the restoration crowd that hangs out here would have a bigger benefit)
Just thought I'd share this PSA with the folks here who are interested. I got a hold of two Drake VMM860AGs (
http://www.rldrake.com/product-vmm860ag.php) and am pleased to report that they make serviceable modulators for our vintage sets.
I can't comment versus the commonly used blonder-tongue and drake ones bandersen has mentioned but since prices on those are increasing (and these don't take up nearly as much space!!) they might be a nice alternative.
They're made to be rack-mounted en-masse, but they don't use any special backplane connectors or anything - they have standard input connectors and can be powered with any supply that provides +5 and +12V.
I'm also happy to answer questions about them if you have any; it gave a clear, sharp picture on my Fleetwood TV set when directly connected and worked okay with some old rabbit ears. I don't doubt it would function much better with a proper antenna attached to it.
I don't see many on a certain auction site at the moment... and those are exorbitantly priced. I've asked person I got mine from whether they have more and if I can pass on their contact info to the folks here that would like one for a far more reasonable price.
Will update post with info when I get it.