>From: rharel@fab8.intel.com (RICHARD HAREL) Subject: Re: Kenwood MODS database - NEEDED Here is the complete list of mods that are known to date for the Kenwood TH-77A Dual Band hand held: >From the factory, it can receive 138-174MHz and seems to do it quite well with the supplied rubber duck antenna. It also can receive 438-450MHz and, likewise, does this quite well too! One very interesting feature of the TH77A is that it can do *DUAL* UHF receive! To do this it uses the VHF receive section and you have less sensitivity, but I really haven't noticed much signal degradation at all. Kenwood has made this radio compatible with the new ICOM S-Series radios from what I can tell. It has DTSS (Dual Tone Squelch System) which means that your radio will not break squelch until it hears a particular sequence of three DTMF tones (ICOM has this also and they call it Coded Squelch which also use three tones). The TH77A also has a paging function that works *exactly* like the ICOM paging. You program the radio with a personal 3 digit DTMF code and someone pages you by transmitting YOUR 3 digit code, followed by a * character and then their own 3 digit code. The ICOM will start to ring to let you know that you have been paged and display the 3 digit code of the person that has paged you. The TH77A will beep once and open squelch as long as the person that paged you does not drop carrier (I prefer the ICOM method for this part, but there is a work around that I will mention in a bit). One thing the TH77A does at this point is bring up a timer so you know how long its been since you've been paged. Maximum time is 99 hours and 99 minutes. Let's see if your battery can hold out that long! The workaround so the TH77A will ring, rather than just beep and open squelch is to put the radio in the pager mode AND also put it in Tone Alert. When you get paged... the radio will "beep beep (pause) beep beep" five times and start up the timer. Kenwood has provided two different types of BEEPS for you. The second type is to ring like an electronic telephone. This one *REALLY* sounds nice!! For those of you that like autodial memories, there are 10 memories that can store 15 characters each. There are 40 regular frequency memories in this radio and you can make them all UHF if you like (no restriction). NOW! On to the *EXTRA* capabilities (there are other BASIC functions that I didn't mention, those were just the highlights). After making a few modifications to this radio, you can get it to do the regular stuff that the IC24AT will do, such as AM aircraft, expanded UHF (400-512 depending on PLL lock) and 800-950 (again, depending on PLL lock) in addition to cross band repeat. HOW DO YOU DO THIS!? Easy (if you've got a steady hand for removing a chip resistor!). Open it up. There are 3 screws visible on the outside and 4 more underneath the battery pack. Unlike most radios, this one doesn't have a spring for the battery release switch. It gets spring action from the metal plate that you will remove when you take out the four screws. I love it! Anyway, the area you will be working in is on the control board which is fixed to the front section of the radio. In particular, look for the yellow electrolytic capacitor (its yellow in mine) that is at the dead center of the board (there are two IC's, one above this and 1 below this). You will have to remove the electrolytic capacitor (C124) and set it aside for a few minutes. You will be putting it back afterward. The reason for removing this is so that you can remove a chip resistor that is underneath it. To avoid tearing the flex board foil traces, do not bend the leads of the capacitor. There is a green wire that is connected to one side of this capacitor. If you disconnect one side of this green wire, you will get RX from 400-512 (PLL lock depends on the radio, but you can DIAL from 400 to 512). Orient the radio so that the volume controls and BNC are at 12 O'Clock on your table (farthest from you) and the bottom (where the battery connects) is at 6 O'Clock (nearest you). In the area where you removed the capacitor, you will see a blank space where there could have been a chip resistor followed by two chip resistors side-by-side and in the next row below that, you will see 3 more that are side-by-side. There is one to the left of these two rows that is kind of off center. Now, there are three ways to configure this radio at this point: 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 right most 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 SETUP BEFORE YOU BEGIN! -- -- -- || || || / \ / \ / \ -------------------------- | | | \-\ | | | /---------\ | | | | | | | | | | | | | | | | | | \---------/ | | | | -- -- -- | | || || <================== 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, its 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). Many thanks to Pontus Hedman (rph@sq.com) for helping me put this information together! Thanks also goes out to James Dugal (jpd@pc.usl.edu). By the way, Pontus did mention that checking the input frequency was a bit annoying. You have to hit FUNCTION SHIFT to get the radio to REVERSE and listen to the input. I agree! Anyway, hope this information helps you get more from you new toy! Its a *REALLY* nice radio!! Gerald J. Walsh | Internet: gwalsh@kilroy.jpl.nasa.gov Jet Propulsion Laboratory | Phone : (818) 354-3913 RF and Microwave Subsystems Section | Fax : (818) 354-2825 M/S 238-528 | 4800 Oak Grove Drive | Pasadena, CA 91109 | Looks good! One more feature worth mentioning for humour value: If you hold down M and PTT and power up, the HT enters "game mode". You get "0000" on the left of the screen. Press "0" and digits start changing rapidly in hex (consequently all appearing as "8"). By pressing 1,2,3 or F you stop the appropriate column. If they all come up the same, er, well I guess you win... maybe something good happens then. Maybe it enables transmit on, cellphone, air, and 30cm :-). At 1 chance in 65536 I'm not about to try to find out, though... (Somebody with the service manual told me the above) -- Pontus Hedman rph@sq.com {uunet|utzoo}!sq!rph VE3RPH (416) 963-8337 Despite what I said in my previous msg about not wanting to try it, I just did. Much to my amazement, after only one or two minutes, I won! By timing the keypresses very carefully, one can improve the chances from 1 in 4096 significantly, it seems [ignore my "1 in 65536" in my previous mail, obviously I wasn't thinking straight.. obviously there are 16 winning combinations out of 65536] And yes, something Interesting does happen when you get all four numbers the same (at least when you get "2222" like I got). More specifically, the display starts doing something humorous. 3/14/91 -- A few more observations: Many of the TH-77a's with 206* serial numbers have problems with memory loss when they are operating and the pack runs down. This is cured by a resistor change. AES replaced it in my TH77 without charge. I don't know which resistor needs to be changed, however. Also, some of the newer TH77a's seem to have a tone mixing with the audio. PL disable has no effect; speculation points to a dc-dc converter in the LCD display circuitry. Due to the weak audio I generally run the volume near max. And I find that my ears are hurting from the high-pitched noise when the HT squelch closes. This is most irritating! I recently did some sensitivity measurements of the TH77a. Here are the results again: SENSITVITY MEASUREMENTS TH-77A USING AN IFR MOD 1000S SERVICE MONITOR 1000 HZ TONE REFERENCE IS 2 LCD SEGMENTS LIT FREQ. SIGNAL MHZ MICROVOLTS 118 1.6 AM 123 0.5 128 0.5 133 0.7 136 0.8 136 0.3 FM 141 0.3 146 0.4 151 0.4 156 0.4 161 0.5 166 1.0 171 2.0 174 2.5 FREQ. SIGNAL SIGNAL MHZ uV. uV. VHF VFO UHF VFO 400 8.0 NO RX 410 3.0 20.0 420 2.0 5.0 430 0.8 1.0 440 0.5 0.3 450 0.7 0.3 460 1.0 NO RX (birdie?) 470 1.7 3.5 480 3.0 20.0 490 5.0 40.0 500 7.0 50.0 512 NO RX 80.0 800 30.0 810 15.0 820 5.0 830 3.0 840 2.0 850 1.7 860 NO RX 870 3.5 880 4.5 890 5.0 900 6.0 910 8.0 920 11.0 930 15.0 940 15.0 950 15.0 >From PPDDC@UWOCC1.UWO.CA Mon Jul 22 07:57:58 1991 Received: from [129.100.2.12] by eugene.convex.com (5.61/1.28) id AA00793; Mon, 22 Jul 91 07:57:56 -0500 >From: Dave Colvin To: horak@eugene.convex.com Dave: Would recommend TH77 far and away above the 470. I sold my Yaesu to get the Kenwood. The 77 has the following advantages after mods: -rx in aeronautical am band -wide rx & tx in vhf into marine -wide rx & improved tx in uhf (my work repeaters) -800 mhz rx (local fd) -separate volume & squelch for each band -pl decode on sub-band -more memories and all could be vhf or uhf The only thing that I will say about the 470 is that it had better audio and that the antenna was more efficient on the ham bands. ******************************************************************************* DAVE COLVIN University of Western Ontario Systems Development & Services Building, Room 120 Communications Officer London, Ontario N6A 5B9 Physical Plant Department Work (519) 679-2111 PPDDC@UWOCC1.UWO.CA Extension 8873 Amateur Radio Operator VE3ZDC CANWARN Severe Weather Watcher Packet Radio VE3ZDC@VE3GYQ Communications Officer ARES London Air Patrol/CASARA London Red Cross Disaster (Civil Air Search & Rescue Assoc) Planning Committee Home (519) 680-0802 ***************************************************************************** >From: Mysterious Ways To: derry@milton.u.washington.edu Subject: Re: Kenwood TH-77A Mods I have modified my 77 (and many friends) for out of band receive, crossband repeat, and out of band xmit. They are all hardware mods. If just just want normal out of band receive and cross band, open your radio and cut the green jumper. Other mods require you to take out chip resistors.. ___ Andrew J. Doane ___....-----'---`-----....___ 409 E. Chalmers #1307 ========================================= Champaign, IL 61820 ___`---..._______...---'___ ajd@turing.acs.virginia.edu (___) _|_|_|_ (___) Email: ket@uiuc.edu \\____.-'_.---._`-.____// ~~~~`.__`---'__.'~~~~ . "Damn it Jim, I'm a doctor NCC-N9KET . not a ham!" . _____..---========+*+==========---.._____ ______________________ __,-='=====____ =================== _____=====`= (._____________________I__) - _-=_/ `---------=+=--------' / /__...---===='---+---_' '------'---.___ - _ = _.-' TCP/IP: n9ket@wb9uus.ampr.org `--------' Packet: n9ket@n9hsi.il.us.na