Yaesu FT-817

8/22/05

Warning first: If you use the finals on this radio beware! This radio has a defect that can cause the finals to blow. This could also take out a transverter if you don't use the proper precautions.
Details: The finals can go into oscillation. Solution:  By Bob Curry, KC3VO

Some neat sources for information:
Yahoo Groups on this rig.
Blown-Finals-817 Yahoo group.

My Mods:  (Do at your own risk. No guarentees !)

MOD #1 bring the transmitters driver output out to the rear panel
  1. I did a very simple mod to take the Driver output from the transmitt section to a SMA connector on the back of the rig. 
  2. First I dig a hole into the back of the rig the size of a sma connector. I did the to the right of the power connector.
  3.  
  4. Then inside the top of the rig I take the grey wire with the red plastic tape on it. Unplug it and tape it.  This wire feed driver power to the PA section.
  5. See the inside of the radio (top left of this photo)
  6.  
  7. Then make up a short new wire attached to a sma connector.

  9. Then plug in the new wire where you just removed the wire with the red tape. Stick the sma connector out the back.
  10. When you are done you will have a driver output that is adjustable. (use normal menus for the out put power selection)

MOD #2 Antenna selection for input. Not really a mod, but everyone trips on this problem at least once.
  1. You do not really need to worry about the power out but you will need to set item #7 Antenna on the F (1sec) menu. This lets you select the front BNC connector or the rear UHF connector for its INPUT. The output has already been modified to go to the SMA connector. The POWER Amplifier should be disabled but I was lasy and left it alone with no drive power.
MOD #3 set up power output to the sma connector. Less than +1dbm out MAX
  1. You can have an adjustable power out of the IF into the transverters with the flick of the power button. It has 4 levels 1 thru 4. I can set each one to a different setting. You can have as much as 2dbm out but they recommend less. Probably an idea to find the 1db comp point and stay below that? Use the hidden menu (hold buttons: A+B+C+Power on, exit and save = F key) to access items 40,41,42,43. . Be sure to write down the contents of these 4 locations before you change them. A number near one hundred produces something close to 0dbm but this depends on your radio. You can set each of the power levels to something useful. I only use 2, High and low. Low puts out -3dbm (half power) for use when I have a local contact. Low power mode saves wear on the TWT I use for 2 and 3ghz.
MOD #4 Receive PreAmp adjustment (take over adjustment)
  1. Did you know you can adjust the pre-amp? It is set to 79(in my radio). If you turn the number down the take over drops, if you increase the number the take over increases. This is handy depending on the take over noise of your transverters. They use it to protect the front end from overload damage. weak signal operators will like this. Not sure what this really does but other ft-817 owners have mentioned it so I will.
MOD #5 AGC for linear meter readings.
  1. Another useful function is to turn off the AGC in the menu(see the manual). This allows you to see the real sense of the FT-817 with out the automatic gain making it non-linear.