How bad does it have to be before its a scrapper set?

[boater sam]

Use one of the redundant shortwave bands?
Can these be adapted easily to go up to 108 MHz?
Sam.

I doubt it. EF80 struggles to do 101MHz. It might do better with Rod Pentodes. Almost any other valve ever used for VHF is better than the EF80. ECC85, ECF82. USA used nuvistors at the  end. They used up to 108 in 1945, not sure what valves. Philips seems to have persisted with EF80s for UK market when they already obsolete for VHF.

I'd fit an AM/FM switch. Don't forget the VHF head needs an IF amp with more stages and an FM detector of some kind.
Schaub-Lorenz (ITT) had some battery valve sets that saved a DF97 and used cheaper DF96 IF amps. It used the DK96 as a fixed frequency changer with 10.7MHz IF in and 6.5MHz IF out. The DK96 and DF96 then had 6.5MHz double tuned IFTs in series with the AM IFTs (460KHz?). Then a pair of germanium diodes as discriminator, as all battery valve FM sets had used since 1953. The DC90 as a self oscillating mixer enabled VHF on battery sets in 1953. The aerial circuit needed carefully aligned to avoid LO radiation. I think the 1st valve on most mains VHF head is more to limit LO radiation (harmonic would affect band III TV), especially the EF80, which is a buffer, not really any gain.
I've checked and a DF97 works in a DF90 socket, and vice versa, no noticeable shift in tuning. It's triodised.
The Vidor Vanguard is unusual apart from being one of only two UK VHF valve portables (The Sky Monarch II, or AM/FM, is battery, but a table model for people with no mains) and the first in the UK 1957 (four years after most of Europe). Unlike all the continental AM/FM valve sets it has no DK96 or DK92 etc. The Triodised DF97 which is VHF self oscillating mixer (like most AM transistor LO/mixer), is also the MW & LW local oscillator. The 1st 10.7MHz IF is then a Pentode mixer for AM. So it's all DF97s apart from the DAF96 and DL96. Also unusually no telescopic rod. The "piping" hiding the seam on the cloth cover is the VHF loop.
It works far better than the Sky Emperor and nearly as well as the Philips Annette on VHF, with advantage of no aerial rods. The aerials on the Sky Emperor are horrid.

Very interesting, thanks Mike. Vidor Vanguard is new to me, didn't realise it is a bit of an unusual set.
Any advantage in using the EF184 instead of EF80? I see Mullard quoted the performance of both at 40 MHz but if EF80 is good for 100 MHz will the EF184 exceed this? I thing the possible gain is better too.
Sam.