4M

I have been active on 4M since 2010 after having spent a long time looking for an unmodified FT847 that was in good condition and local so that I could view before parting with any cash! Eventually I found what I was looking for and was up and running on 4M with a UK ‘C2’ model that had been made to work on the band albeit with a rather inefficient TX and almost deaf RX…

Today the FT847 is much improved following the installation of G4FUF’s superb internal LNA and PA1O’s PA modification plus the cutting of the “ALC limiting” wire.

Below are a few photos taken when the lids were off:

This shows the CPU jumpers, one of the first things I did was to put the set back to the original “C2” factory supplied band coverage. This did mean that 40M coverage stopped at 7.100Mhz. Not a problem…  🙂

The next step was to locate the original BPF board, check out all the connections and carefully remove it.

Here’s the completed G4FUF board. It took a few hours to assemble following the excellent step by step instructions supplied with the kit.

This shows the new pre-amp fitted and all the connections in place.

Once the performance of 4M receiver side was improved the next step was to look at the transmit output power. As mentioned previously I opted to do the PA1O modification followed by the “ALC mod”.

The PA1O mod requires the removal of the PA board. This was fairly easy to do, the key thing was to make a careful note of all the connections and fixings (including screw lengths!)

Here the PA board has been removed and is shown before the modification.

Once the PA board was replaced the ALC limiting wire was located and disconnected and the FT-847 was checked for performance on all bands.

Following the modifications the rig now produces up to 65W output on 4M and the current drawn is much closer to what one would expect.

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