Icom IC-7300 "Push Button" TUNE Mod
Having tried tried various "Timed" mods to enable a 10 watt carrier for external AMU/ATU tune up purposes I have ended up using this simple arrangement which uses a push button. The problem with the timed variety is that the time you select for your circuit is never just right, it is either too long or too short so with this arrangement you only need to press the new "TUNE" button for as long as is required to do the job. When the button is pressed a 10 watt carrier is transmitted whatever mode is selected, it should be noted that on SSB the carrier is "zero beat" so no qrm is caused to the stations using the frequency you are listening to.
All you need is a Molex 4 pin plug which you can get from e bay etc, a diode and a 47k resistor. Any suitable momentary push switch can be used.
Something to bear in mind is that the rig's SWR readout is only any where near accurate when running full power (100Watt's on HF) and at 10Watt's provides a very low and totally inaccurate reading so a separate SWR meter is needed to provide an accurate reading at this "TUNE" power level. It should be noted that the rig's swr meter is disabled in the "TUNE" position.
Below is the simple circuit and a picture of the button that I am using.
I found this push switch on e bay from China, very cheap..................