Newsgroups: rec.radio.amateur.misc From: aviator@athena.mit.edu (Joakim Karlsson) Subject: Kenwood TH-78A Initial Impressions *LONG* Date: Mon, 11 May 1992 19:56:41 GMT What follows is a relatively long write-up reflecting my initial impressions of the Kenwood TH-78A. To summarize: Hot radio, but no info yet on mods, out-of-band TX/RX, or cross-band repeat. Kenwood has some information from Japan, but it hasn't been made public yet. Please do not distribute further. Please do not distribxute on packet. ...Joakim --- CUT HERE --- Here are my initial impressions of Kenwood's new dual band handheld, the TH-78A. I purchased it at HRO in Salem, NH. If memory serves, their price is $529.95, but I paid $509.95, based on matching a quote from Austin Amateur Radio Supply. I also bought ANLI's replacement telescoping dual band HT antenna, and ordered the SC-35 soft case, which arrived from HRO's Virginia store a few days later. Just a few days ago, I bought the ME-1 memory expansion unit from the Salem store, more about it later. The TH-78A is a dual band handheld, with the capability of cross- band duplex operation and dual in-band receive (i.e. receive two VHF or two UHF stations). In the U.S. version, tone encode/ decode as well as DTMF encode/decode are built in. Nominal output power is 2 W with 7.2 V DC input; increasing to 5 W with 13.8 V. Two intermediate power levels are available: Low (0.5 W) and Economy Low (20 mW on VHF, 10 mW on UHF). The standard TX limits are 144-148 Mhz on VHF and 438-450 MHz on UHF. RX limits are 118-174 on VHF (118-136 is AM) and 438-450 MHz on UHF. At the time of writing, no information is available on out-of-band TX or RX, cross-band repeating, or other mods. As far as I can tell, the infamous Kenwood green wire is absent from the TH-78A. Prior to this radio, I owned a Kenwood TH-27A 2m handheld. I bought it almost exactly one year ago, and added a whole bunch of accessories over time, almost all of which are compatible with the TH-78A. So, I now have the following TH-78A accessories: SMC-33 remote control speaker mike, HMC-2 headset with VOX and PTT, BC-15 desktop charger, BT-8 battery case, PG-3F filtered cigarette lighter adapter, PG-2W DC cable, and BH-6 swivel mount (on order). Additional accessories available include: SMC-31 and SMC-32 speaker mikes, TSU-7 CTCSS unit (standard with US version), BC-14 wall charger (I think this is the same one that comes delivered with the radio), PG-3H cigarette lighter adapter (what's the difference between it and the PG-3F?), SC-36 soft case (for new nicads, see below), and WR-2 water resistant bag. The TH-78A has the same nicad form factor as the TH-27A/47A, and the new TH-28A/48A radios. The standard battery is the PB-13, a 7.2 V 700 mAh nicad which slips inside the radio, with no protrusions. Also available are the PB-14 (12 V 300 mAh), and two new ones: PB-17 (12 V 700 mAh) and PB-18 (7.2 V 1100 mAh). I don't believe the PB-14/17/18 will fit the SC-35 soft case. I think the SC-36 soft case is intended for the PB-18. I can only guess that the PB-14 and PB-17 could be used with the SC-36 provided some sort of foam block was used to fill the gap. I've only owned the PB-13 standard battery, and have never felt a need for a 5W battery pack or a higher capacity 7.2 V pack. I use the BT-8 AA battery holder for back-up situations. The TH-78A replaces the TH-77A dual band HT, which used a different battery form factor. While the TH-77A may be available in limited quantities at reduced prices, I believe it is being discontinued. The same applies for the TH-27A/47A. Incidentally, since it seems that Kenwood is going to stick with this new battery form factor for a while, I have reason to believe we will see third party replacements soon. This is based on a brief telephone discussion with someone who runs a battery business. The TH-78A comes shipped with the radio, a rubber-duckie dual band antenna, a belt clip, a hand strap, a rubber cap (covers the DC in, mike, and phone jacks when not used), a wall charger (I know of some TH-27A owners who use the wall charger to power the radio at the economy low power setting), a battery pack (PB-13), a manual (including schematics), and a warranty card. The warranty covers one year. First impressions: It's very compact and heavy on features. Size wise, it's only about half an inch higher than the TH-27A. With the standard rubber duckies attached, the TH-78A is actually shorter than the TH-27A. The other dimensions are roughly the same. With a 7.2 V 700 mAh pack, this must be the smallest dual band handheld available. The overall size is very comfortable, as is the shape of the radio. Aesthetically, it's also very pleasing - it doesn't have the toy feeling the Icom 2PAT does. However, operators with larger hands and fingers than mine may complain, especially about the front key pad. Also, I would recommend that prospective buyers wait until the mod info has been made public. The top of the radio has a standard BNC connector, with a small gap for fitting the rubber cap; DC in/mike/phone jacks (compatible with other Kenwood handhelds, something Icom could learn from), and two rotary encoders. The rotary encoders have an outer (lower) dial for squelch (one for each band), and an inner (upper) dial for either volume or tuning (see below). The volume/tuning dial has discrete settings, which I think is a nice touch. On the TH-27A I often bumped the volume setting down to zero, accidentally missing transmissions. There are also two LEDs, one for each band, located next to the rotary encoders. The LEDs are two-color ones, a green light indicates open squelch (equivalent to the "Busy" indicator on other Kenwood handhelds), a red light indicates TX. I'm still undecided about this arrangement, but at least the LEDs are more visible than the single LED was on the TH-27A. The front panel has the power button way on top, two large circular buttons (MESSAGE and BAND) below it, a speaker (pretty good audio: high volume settings yield little distortion, but some noise), a large LCD display divided into two segments by a horizontal line on the glass cover, a 16 button keyboard, a sliding cover which "protects" the keyboard, and a microphone (just below the keyboard - a pretty good location). I have mixed feelings about the sliding cover; it's on pretty securely, although I had no problems removing it (it's useless with the soft case). The radio looks sharp with all the keys hidden, but I doubt that it has much value except maybe for avoiding hitting any keys accidentally. I find that the sliding panel slightly hinders using the bottom row of the keyboard. In fact, because the keyboard is slightly recessed, the bottom row is a little bit more difficult to use than other rows even with the keyboard cover removed. I also find the power button slightly difficult to activate, although its location and size is a definite improvement (the TH-27A was difficult to power on and off in the dark). I guess one advantage is that once the radio is on, it will be difficult to turn off accidentally. The left side panel has buttons/keys for PTT, LAMP, MONI, E.CHG (encoder change, see below), MHz, VFO, MR, and CALL. The PTT, LAMP, and MONI keys have a very satisfying feel with a nice "click" - a definite improvement over the TH-27A. The CALL button is too small for my taste. The right side panel only contains an attachment loop for the hand strap. The back panel has attachment points for the belt clip (or optional swivel mount) and a sliding release for the battery pack. I find that the battery packs are easy to insert and remove, unlike the Icom 2PAT. I've never had any mechanical problems with the battery packs on my Kenwood HTs. The bottom of the battery pack has connectors for charging with the BC-15. The soft case must be removed prior to charging the radio or removing the battery pack. The soft case is OK, the fit isn't ideal, but it serves its purpose very well - my TH-27A went through a year of hard work in nearly mint condition. It also provides a convenient way for attaching the SMC-33 speaker mike clip to the radio. The LCD display is much larger than that of the TH-27A and represents an overall improvement. It seems much easier to read. The top segment of the display shows both frequencies side-by- side, whereas the lower segement is used for information such as memory channel, volume setting, and alphanumeric messages. Alphanumeric messages are displayed using line segment combinations (HP-41 style). Various status flags are displayed in both segments of the display. Light is provided by what appears to be four green LEDs, one in each corner of the display, a definite improvement over the TH-27A. The front 16 button keyboard is also lit, but not the other keys. To the best of my knowledge, to date only Yaesu has provided lit keyboard on HTs. Both the display and the keyboard lights are activated by pressing the lamp key. The two lights cannot be controlled separately. The lights stay on for 5s after the activation of any key. Alternatively, one can press the F key followed by the lamp key, in which case the light stays on until the same sequence is repeated. The user manual is mediocre. While most features are explained adequately, it appears that only the bare minimum of information is presented. Furthermore, the manual suffers from the standard Japanese manual problems. As a former student of Japanese language and culture, this is of some interest to me. The following three problems seem to be systematic: (1) Misspellings and typos (e.g. "lamp kay"). (2) Poorly constructed or confusing sentences (e.g. "when you press and hold the E.CHG. key, each control temporary control of the volume or tuning control passes to the VHF band"). (3) Patronizing statements (e.g. "Please study these controls carefully. By the time you reach the end of this manual, you will have had to use each of them many times"). But, I digress... The user interface has much in common with the TH-27A, but not as much as I'd like to see. As usual, most keys can perform about four functions. Pressing the key alone provides the primary function. Pressing the F key first, and then the key, performs the secondary function. The primary and secondary functions are labeled on the keyboard. Color coding is used to separate some functions (primary in white, secondary in blue, DTMF pad in red). Other, unlabeled functions, are obtained in several ways: Pressing the F key for appr. 1 second, then a key; pressing the M key, then a key; pressing the M key for appr. 1 second, then a key; and pressing a key during power up. These auxiliary functions, while not labeled, are normally used infrequently and, in Kenwood's defense, an attempt has been made to provide some sort of connection to the key label. Scanning is initiated by pressing either the VFO, MR, or CALL key for one second. So, while the user interface isn't great, it's adequate and occasionally reflects some design intelligence. In order to remain compact and avoid three rotary controls, Kenwood has introduced a sort of user settable rotary encoder. The outer dials always control squelch. The inner dials however, can be configured in several ways: (1) Left dial controls volume of main band and right dial controls tuning of main band. (2) Left dial controls volume of sub band and right dial controls tuning of sub band. (3) Left dial controls volume of VHF band and right dial controls volume of UHF band. (4) Left dial controls tuning of VHF band and right dial controls tuning of UHF band. Without going in to great detail, the desired configuration is selected by the E.CHG key. You select a default configuration, and can then temporarily select other configurations using the BAND key or the E.CHG key. It's a little bit confusing at first, and the E.CHG key is a tad difficult to activate, but it works. I prefer configuration (1). However, while there is an indicator showing which is the main band, there is no way of knowing what the current encoder configuration is short of turning the two dials. When you change the volume, a volume indicator is temporarily shown on the display (a "V" followed by a number indicating the volume level). Volume levels range from 0 (mute) to 20. Unlike the TH-27A, the beeps and audible tones generated by the radio appear to go through the same amplification path that receive audio does. This has two side effects: The mere pressing of any key generates a bit of white noise as the speaker is activated, and the volume of the beeps vary with the volume setting. I like the second feature: On the TH-27A the beeps were so loud that it was almost painful when using certain earphones. The audio feedback provided by the TH-78A is nearly identical to that provided by the TH-27A. The beeps can be turned off entirely, if desired. Like other Kenwood handhelds, the TH-78A operates in three basic modes: VFO mode (permits direct keyboard frequency entry), MR mode (memory recall, using programmed memories), and CALL mode (call channel only). There's a key for each mode (this differs from the TH-27A). The VHF band and the UHF band can be in different modes; however, there is only one call channel. In the VHF VFO mode, the transition between AM (118-136 MHz) and FM (136-174 Mhz) is seamless. I don't know if it's possible to turn on AM detect manually outside the 118-136 MHz segment. >From a performance perspective, I can't report much. Receive audio is satisfactory, although there seems to be a little bit more white noise (but less distortion). Transmit audio reports range from good to muffled or slightly distorted (with the SMC-33, but mine's been banged around a little bit). When using the dual in-band receive feature, image rejection or sensitivity can be reduced (there is a warning to this effect in the manual). In fact, I've found a birdie which exists with 146.61 in the VHF band and 148.15 in the UHF band. If I reverse the frequencies however, the birdie disappears. The radio uses two 1st IFs (45.05 MHz and 58.525 MHz) and a 2nd IF (455 kHz). Maybe someone who understands the theory involved, can do the math for me and explain the birdie. I've reproduced this problem on two brand new TH-78As. It is not as prominent with the standard rubber duckie antenna attached, however. Btw, I've seen a report that the rubber duckie antenna is narrow-banded. I also get interference (squealing/whistling noise blocking out the received signal) on 146.61 when using my Larsen mag mounted 5/8 wavelength antenna. This problem is not reproducible with other antennas. It only occurs when 146.61 is used on the VHF (left) band. I'm open to ideas as to what may be causing this. Two suggestions are poor RF ground or a short in the coax (I've tried to test for the latter, with negative results). It will be interesting too see whether switching to a dual band whip solves this problem. In any case, I'm not too concerned, since I'm planning to buy a mobile radio, and I've ony been able to reproduce this problem under very specific circumstances. In terms of intermod or rejecting unwanted signals the TH-78A appears slightly less capable than the TH-27A was, but this is to be expected from a dual bander. Except for certain well known problem areas (e.g. Route 128 near Burlington and Waltham, MA), this is usually not a problem. The TH-78A has a default of 40 channels and one call channel. Each memory can hold RX frequency, direction of offset (or TX frequency for odd splits), tone frequency, tone encode on/off, tone decode (CTCSS) on/off, DTMF encode/decode (DTSS) code, DTSS on/off, and reverse status (i.e. RX/TX frequencies reversed). Every channel can contain an odd split. A nice feature is that no differentiation is made between VHF or UHF memories; you can mix and match at will. Normally, the radio memories are assigned numbers, starting at 0. In the standard configuration you get channels 0-39. With the optional ME-1 EEPROM expansion unit, 250 memories are available (0-249). You can choose between 1-digit (0-9), 2-digit (0-99), or 3-digit recall (0-249) mode. If, let's say, you select 2-digit recall mode and have the ME-1 installed, channels 100-124 would not be available through keyboard entry, only by using the rotary encoder. The radio can be put in a memory channel character display mode, where a 6 character alphanumeric label is assigned to each channel. Channels are still selected by their memory number, however. I have the ME-1 and really like this mode, as it helps me keep track of what I've stored. The entry of letters using the 16 button keyboard is pretty well thought out, and becomes natural fairly easily. The keyboard is labeled just like a touchtone phone key pad, with the addition of "Q", "Z", and "Space" (not labeled) assigned to the 1 key. The trade-off with using this mode is that it halves your memory capacity. This is a non-issue with the ME-1: having 125 channels is providing to be more than adequate. :) The TH-78A will do time operated scan or carrier operated scan (the TH-27A had a third mode, seek scan). The mode can be set independently on each band, but switching modes requires pressing the 8 or 9 key while powering up - not very convenient. The following scan options are available: Memory scan, band scan, programmable band scan, MHz scan, VFO/Memory scan, CALL/VFO scan, CALL/Memory scan, and VFO/Memory/CALL scan. The scan rate appears to be about the same as the TH-27A. A nice feature is that you can scan on one band, while receiving on the other (this also works for dual in-band receive). However, when using the HMC-2 headset a slight clicking noise is heard during the scan. Memory channels can easily be locked out from scanning. An alert function is available, where Channel 1 is monitored every 5 seconds. If any activity is detected, a beep heard. On the TH-27A you had the option between a beep alarm or automatically changing to Channel 1 when activity was detected. I never used this feature much on the TH-27A, because an annoying burst of white noise was heard every five seconds when checking the channel. This problem has seems to have been eliminated from the TH-78A, however. When transmitting, pressing any key on the front key pad sends the corresponding DTMF tone. A feature can be activated which causes the transceiver to remain keyed for 2 seconds after pressing each number. This allows you to release the PTT key after pressing the first number. This seems like a nice feature, but on the repeater I use locally this somehow confounds the controller, and it doesn't recognize the DTMF sequence. Ten autodial memories are provided (15 digits each from the set 0-9, A-D, *, and #). In receive mode, the DTMF memories can be used to operate the TH-78A as an expensive telephone dialer. I'm not going to describe the details of CTCSS and DTSS, it's pretty standard. Squelch settings can be set independently for each band. DTMF paging is also supported, allowing you to page an individual station or a group code. Eight paging memories are provided. I find this to be primarily a gadget feature; I wonder if there is anyone out there who actually has a practical need for this? A new feature, with extreme gadget value, is the ability to send and receive 6 character alphanumeric messages in the DTSS or paging modes. I believe that each letter of the alphabet is defined by a DTMF triplet: a #, followed by a digit 0-9, followed by a letter A-C. Each combination of a digit and a letter corresponds to a position in the alphabet. Ten memories are provided for sending or receiving these messages. The only worthwhile aspect of this feature is that message memory 0 is a power on message, which is shown briefly after powering up the TH-78A. The default message is "TH78A", but it's kind of neat to have it come up with your callsign, name, or favorite 6 letter greeting (how about making the default message "BUY ME"?). A tone alert system lets the radio stay quiet until a signal is received, at which point one of two user selectable alarms is sounded (I like the telephone type ring). I could see that this could be useful in combination with CTCSS and DTSS. Tone alert is independently selectable for each band. The mixing of the audio between the main and sub bands is user settable. This only affects operation with an external speaker or headset. Main and sub band audio can either be mixed or separated, and they can be placed either on the internal speaker or external speaker. All combinations of sub/main band and internal/external audio are possible. Nice touch. However, even when no internal audio is selected, a very low level of audio (almost noise) is emitted from the internal speaker when a signal is received. This seems strange, but it actually turns out to be pretty neat when working packet, since audible feedback is provided for incoming packets. The capability of splitting the main and sub band audio provides the capability of monitoring a voice channel while working packet - very nice. When using VHF and UHF simultaneously, full duplex is available, for telephone style conversations. It is possible to mute the internal audio; an attempt to avoid feedback. However, this feature is best used with a headset. This feature is not available when using dual in-band receive. Dual in-band receive (simultaneous reception of two signals in the same band) is activated simply by pressing the f2 key. You have the option of monitoring 2 VHF frequencies or 2 UHF frequencies. You can still transmit on the main band, but the sub band is muted entirely during transmit. As mentioned earlier, certain combinations of frequencies (I've found one) will cause birdies. In addition to an internal clock, various timer functions are included. When the clock function is activated, the time is displayed in lieu of the sub band frequency, but sub band reception continues. When operated in single band mode, the time can be displayed next to the frequency. Like the TH-27A, a switch-on timer and switch-off timer is provided, which can be used as a reminder for nets and skeds. The switch-on timer can be configured to sound a 10 second alarm in addition to turning on the radio. Other keys/features include MONI (opens squelch to monitor frequency on the main band), LOCK (disables all keys except LAMP, MONI, E.CHG, LOCK, and PTT), muting volume for using earphone (however, this also mutes the speaker volume; not a very useful feature), ABC (automatic band change, switches PTT control to sub band when a signal is received), optional single band operation, MHz (tunes in 1 MHz steps), channelized frequency display (shows channel number instead of frequency), battery saver mode (with user selectable sleep times), and APO (automatic power off: alarm sounds after 59 minutes of inactivity, 1 minute later power is switched off). Installing the ME-1 required opening the radio. Four screws need to be removed. Opening and separating the two radio halves was a tad more trickier than the TH-27A, but not overly difficult. The same applied for closing everything back up. Beware of the two tiny o-ring rubber seals placed over the two LEDs on the top panel. These have a tendency to fall off when opening the radio. Installing the ME-1 was straightforward, although quite a bit of force had to be used in order to insert it fully into the socket (no metal conductors should be visible when fully inserted). The internals of this radio are amazing, even for a non-techie like me. Nearly all components are surface mounted. In summary, I'm very pleased with this radio so far. I'm still waiting for the CAP TX mod, however. What sold me on this radio was the ability to monitor two VHF frequencies simultaneously. For CAP operations, this is particularly handy. I can now monitor a CAP voice frequency and 121.5 (ELT/emergency frequency) simultaneously. Or, I can get the airport ATIS while using another VHF frequency. Or, monitor a voice channel during packet operations. Or, a National Weather Service station. The possibilities are endless. Also, I probably wouldn't have bought this radio if it had not been compatible with the TH-27A series of accessories. I believe this radio will be very competitive with the Icom W2A. In my opinion, this is the first Kenwood dual band handheld to be taken seriously. -- Joakim Karlsson | aviator@athena.mit.edu Flying Fanatic in Training | Air: ASEL CAP: Freedom 226 Mobile FCC: N1JHW "Oh, I have slipped the surly bonds of earth And danced the skies on laughter-sillvered wings"