GM4ULS ham radio station

a QRM-free zone!

Modifications to the Yaesu FT-847

Posted by gm4uls on October 2, 2012

For some time now there has been a published modification for the FT-847, enabling it to be used on the top end of 40m and on the 5MHz near-vertical-incidence-skywave spot frequencies. The latter seems to be an interesting prospect, and as the experiment still has three years to run I have been toying with the idea of getting on board. The modification seems to be fairly simple, although not for someone like me who has a shaky hand and only one good eye – good grief don’t let me anywhere near a printed circuit board with a soldering iron! I have the following text saved somewhere:

There is a set of six solder pads inside the radio that appear to give each radio it’s “country identity” and to perhaps do other things. People have found that by changing the configuration of these solder pads, one can open up the transmit range of the radio. One caution: when the transmit range is opened to the full RX range of the radio, it is possible to transmit in the 36 MHz range which some say can destroy the RF power transistors.

All such instructions come with large warnings not to transmit outside of one’s licensed frequencies, and a warning that the efficiency of the rig will fall away outside the legal bands (that might be more of a problem on 5MHz than anywhere else). Also the modification procedure will dump all your memories and your repeater shift – the soldered pads ‘tell’ the rig what country the rig was marketed for and the shift is set automatically. Much of the advice given directs you to the web pages of G1IVG, who seems to have the procedure well covered.

However, something I notice is that the instructions for the mod that are doing the rounds have minor differences in detail. Here’s one which, it’s said, extends your HF bands to 500KHz per band, though that doesn’t give 5MHz. I notice that Yaesu, who seem to have published it, say ‘This document may not be modified in any way’…

… Tell that to the bloke with the black marker!


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