Hello all,
Well, I've finished it off, it now has a circuit pretty much like the one above.
I gave up on the idea of getting the feedback from the 75R RF output as it was really difficult to sort out a dominant pole and keep the audio bandwidth as wide as I wanted.
The LC filter to keep the RF away from the cathode needed to be realtively low (about 100kHz) to keep the circuit working well. This made for a large phase shift and caused instability with any large level of NFB. With the NFB as it is now I can pile on more or less as much as I like, the preamp I've got the setup connected to can produce about 5V pp!
Also having the NFB go to the point it does has the added benefit of lowering the output imepedance of the cathode follower.
It now sounds great and I've just put my back out pulling up carpets to plumb the coax round the house from my computer room to my bedroom and basement workshop.
I'd welcome any more ideas on how best to make aerials before I do some experimenting next week? At the moment I've got a few feet of wire hanging out of the coax sockets but it could do with a bit of stepping up to give the signal a fighting chance against all the switch mode PSUs and ADSL from the phone lines round the house!
I've put a video up on youtube but it hasn't come out very well
http://www.youtube.com/watch?v=EgH2w1tuhBo
Thanks for everyone's help, especially MichaelR and Kallee20
Now to try tweaking the IF on one of my 50's sets to give a wider bandwidth...
now, then bed!
Cheers
Dom