TH-77A miscellany ================= (Part 2) 1 - With one side of the green wire pulled, you will have 136-174 RX, 400-512 RX. If that's all you want, you are done. 2 - By removing the rightmost chip resistor (R129), in addition to keeping one side of the green wire disconnected, you will have 136-174 RX, 400-512 RX, 118-136 AM RX, 800-950 RX. 3 - By removing both of the chip resistors, in addition to putting the green wire BACK where it belongs, you will have 136-174 RX/TX, 400-512 RX/TX, 118-136 AM RX and 800-950 RX. All three of these options include, of course, putting the electrolytic capacitor back in place afterwards. NOTE! ONCE YOU START DOING THIS STUFF, YOUR MEMORIES AND POWER ON SWITCH CONFIGURATIONS WILL ALL BE LOST! MAKE A NOTE OF HOW YOU ARE SET UP BEFORE YOU BEGIIN. -- -- -- || || || / \ / \ / \ -------------------------- | | | \-\ | | | /---------\ | | | | | | | | | | | | | | | | | | \---------/ | | | | -- -- -- | | || || <============ REMOVE THE RIGHT ONE | -- -- -- | FOR AM/800-950 RX. | -- | REMOVE BOTH TO ALSO | || -- -- -- -/ GET EXTENDED TX. | -- || || || / | -- -- -- | | | | /------------\ | | | | | | | | | | | | | | | | | | | | | | \------------/ | | | | | -------------------------- Layout shown with electrolytic capacitor C124 removed. The best way to do this is to heat up both sides of the resistor and push it out of the way with something small. At least this was the best way for me! Once it's out, put the capacitor back in place and close it up. (Put the green wire back also, if you are making the out of band TX mod too!) TO OPERATE THE NEW FEATURES To receive AM aircraft, get the VHF side in the main band and hit the ENT key twice to go to the VFO. Once you are in the VFO, hit the UxU key twice. Once for dual UHF receive and the 2nd time for AM (118-136). To receive 800-950, get the UHF side in the main band and hit the ENT key twice to go to the VFO. Once you are in the VFO, hit the UxU key once. To enable crossband repeat, hold down the SUB BAND UP ARROW key while turning on power. To disable, do the same thing again. Kenwood says that both bands can contain shift information but only one band can include an encode/decode tone. One more thing. The POWER ON + 8 KEY that allows you to select the kind of memory recall will be a bit different. Now, you will have an extra option in the right side of the display. E1 or E2 which may be selected with the VFO control on the top of the radio. E1 mode will allow you to automatically make the radio switch to AM or switch to the 800MHz stuff as you use the VFO knob to move through your memory channels. E2 mode will skip over any memories that are AM or 800-950MHz. In E2, the only way to recall one of the *special* memories is to go to the VFO, hit the UxU key to go to AM or 800MHz and then recall one of these memories. Personally, I have mine in E1 and don't know any reason why anyone would want to be in E2, but its there if you need it! The Kenwood modification sheet says the following about AM sensitivity: While the receiver sensitivity is neither specified nor guaranteed for the AM range, the sensitivity is typically less than 1uV for 10dB signal plus noise to noise ratio between 123-131MHz. The band edges, however, measure between 8-20uV for 1dB S+N/N ratio. SOME PERSONAL OBSERVATIONS My radio seems to have a hole in it in the 800MHz band. I get this beeping sound when I try tuning between 864-875MHz (I believe the TH77A beeps when it can't lock). Also, the sensitivity could be better around 483MHz (local Sheriff). I did notice that using the dual UHF receive and tuning to 483MHz was better than using the straight UHF receive. (Remember, the dual UHF RX uses the VHF section with reduced sensitivity. Well, it's reduced in the amateur portion, but seems to be enhanced out of the band!) At around 506MHz (Los Angeles PD) its VERY weak. I could barely hear anything WITH an outside antenna. Maybe some tweaking inside could improve this (I haven't really looked for the VCO yet). Gerald J. Walsh Cont'd in part 3 (Downloaded from GB7SYP)