Even more notes on the FT847 modification!
based on information received from Graham Taylor G8HVY
The factory-modified UK version of the FT-847 is version C-2 (printed on the outer carton); any other designation is an indication that the set did not leave the factory with the UK 70MHz mods.
G7CNF's article includes a diagram of the 54—76 MHz filter unit:
However, the UK model service manual shows the following different values:
C3076 120 pF
C3082 8 pF
C3091 270 pF
C3097 8 pF
C3118 120 pF
There are also two additional capacitors C3071 & C3119, both 0.1 uF
L3021 0.33 uH
L3024 0.56 uH
L3026 0.15 uH
L3029 0.56 uH
L3032 0.33 uH
It would appear that G7CNF might have been supplied with a set that was not a UK Factory modified set.
I remember seeing sets at one well-known dealer a year or so ago that were C-3 versions! The boxes had been re-marked in felt tip pen "C-2" - draw your own conclusions!!!
So buyers beware: not all is what it appears!!!
Additional information received from Keith Naylor G4FUF
Nige's results are consistent with a non-UK modified 847, AFAIK.
Only s/n 8xxxxx onwards are genuine manfacturer-modified for 4m in the UK.
The 45MHz feedthrough (and multiples thereof) are from the 1st. L.O. frequency from the last mixer.
Check what diodes are fitted in the filter selection matrix on the RF board: the 54-76MHz filter is either not enabled or (on very early models) not even fitted!!. You need to check the voltage at TP3012 (HF-H-TX) is ~<0.4V.
Having said that, even a modified 847 has some spurii on 4m (typically <-55) and these can fall close to the emergency service output channels around 70.65MHz. If you live very close to one (like I do, on same hill!) then I suggest using a good BPF.
It may not be wise to wideband this radio, as you may eventually make the mistake of transmitting on the emergency services' frequencies, as did a couple of G stations during recent sporadic-E openings to CT.....