A Review: The Kenwood
TH-D7A dual-band data HT
By Alan Crosswell, N2YGK
I recently gave myself the opportunity to buy the new Kenwood TH-D7A
HT: I killed my old HT
trying to repair it. I had heard about the TH-D7 from the APRS special interest group Internet
mailing list (You can subscribe by following the links at http://www.tapr.org). Besides being a
modern dual-band (2m/70cm) HT with the usual features, it also contains a 1200/9600 baud packet
TNC, including special support for APRS, DX PacketCluster, SSTV, and Kenwood Sky
Command remote base control. MSRP is $499. Current street prices are around $439-469.
The Usual and Some Unusual HT Features
As with comparable voice-only VHF/UHF HT's the TH-D7 has 200 memories,
selectable bands on
the two VFOs: V/U, V/V, U/U, automatic repeater offset selection, and wide-band receive features,
including AM airband. Memories can be used for either band -- they are not split into a group for
each band like on some rigs. Alphanumeric, mixed-case names of eight characteon some rigs. Alphanumeric, mixed-case names of eight characters can be assigned
to each memory.
One unusual feature, or at least new to me, is the well-designed menu
system. This is a pleasant
surprise from a manufacturer with a reputation for hard-to-remember multi-key combinations for
programming (owners of the TH-79 and TM-733 will know what I mean). All functions can be
performed one-handed, mostly with your thumb, while holding the radio in the palm and have
keypad shortcuts as well as menus that are scrolled through using a 4-way arrow key: up, down, left
(also used as Escape or back), and right (also used as Enter or confirm). All menus have text
prompts that guide you through the choices. There are only two functions that require holding a key
down more than briefly: power on/off and keypad lock. Of course, many functions do require
multiple key presses, but the most common are on single keys.
Another strange feature is that the one knob on top of the radio controls
tuning (can be used
interchangeably with the up/down arrows) and volume for both bands; Squelch level is a function
key combination (F key followed by hitting the monitor button and then scrolling up or down using
the arrows or tuning knob). Also, there is only one volume knob for both bands: use the BAL key
to adjust the balance between the two.
In a return to HT basics after a couple years of 1/2 watt HTs being the
norm, the standard supplied
9.6V NiCD battery pack develops 5 watts out. Low power settings of 2 and 1/2 watt are also
available. The anntena uses the now-common SMA threaded connector
rather than a BNC, so you can't just use your BNC after-market duck. Screwing the antenna on is
somewhat stressful if you're afraid of cross-threading it like me. The supplied antenna is pretty good,
but as usual, an 18-inch extended duck from Comet or Diamond works better. And, you'll want to
get an SMA-to-BNC adapter so you can connect to a magmount or other antenna. These adapters
are not so hard to find once you realize that Yaesu sells one for their newer HTs that use the same
As I'll get to below, the TH-D7 has serial ports for RS-232 communications.
Using free Windows
software available on the Kenwood web site (http://www.kenwood.net) you can program all the
memories and other options and save your configuration in a file. The user interface for this software
is quite nice, and the configuration files are plain text that can easily be hand-edited if you pref not to
use the gooey interface:-) The same web site has a PDF version of the user manual so you can use
the free Adobe Acrobat Reader to have ) The same web site has a PDF version of the user manual so you can use
the free Adobe Acrobat Reader to have a backup copy of the printed manual.
Here's where the TH-D7 gets very different from other HTs. The TH-D7
has a built-in dual-speed
packet Terminal Node Controller (TNC) very much like a Paccomm, MFJ, Kantronics or other
TAPR TNC-2 clone that includes a GPS connection.
The TNC has two modes: one that is like a TAPR APRS Mic Encoder and more.
The other that is
like a conventional TNC-2. In the Mic Encoder mode, you don't need anything else besides the
radio to participate as a full two-way APRS user -- you can send and receive position reports and
short text messages: Text is entered using the keypad in a somewhat tortuous manner: To get the
lowercase "c" simply press the ABC/2 key six times (ABCabc)!. However, those familiar with the
Mic Encoder know that it has seven canned status messages (Off duty, Enroute, In Service,
Committed, Special, PRIORITY, EMERGENCY) that are selectable from a menu so it works quite
well for public service.
Your position (latitude and longitude) is entered either manually, via
the menu system, or by attaching
a GPS receiver to the GPS jack on the side of the HT. Once you've entered your position, received
APRS reports are displayed along with a compass direction and distance from you. This is where
a compass direction and distance from you. This is where
the TH-D7 is more than a Mic-Encoder: The Mic-E only transmits APRS reports on the end of
your voice transmissions. The TH-D7 does this and can also receive reports and messages and
respond to them. Typically, in this two-way mode you would operate on 144.39 but without the
typical computer, TNC, radio and rats nest of interconnecting cables. Some APRS TH-D7 users
are sending each other two-way text via the APRS RF-to-Internet (and back) gateways.
Furthermore, if your GPS supports waypoint display, the TH-D7 uploads received APRS position
reports to your GPS so the callsigns of other APRS users can be mapped for you. To avoid clutter,
a distance filter is available that ignore reports containing a position outside a given radius.
While in the APRS mode, the TH-D7 will also decode and display DX Packet
Again, this is just the HT alone -- with no computer attached.
If that weren't enough, the TH-D7 has a computer serial port on the side.
Plug in your computer and
you get a TNC-2 clone that operates at 1200 and 9600 baud. The TNC-2 implementation is fairly
complete and even includes
an undocumented KISS mode. At this point documentation of the full feature set and limitations of
the TNC is not available so there's been a lot of guess work. For instance,ilable so there's been a lot of guess work. For instance, since the serial port
requires software flow control, it is unclear how this interacts with KISS which usually uses
hardware flow control. Also, the AX.25 window size is one packet. "Real" TNCs usually allow 3-7
outstanding packets. And, digipeating is not available. The worst feature of this TNC is it does not
remember any settings other than MYCALL. So your computer will have to reconfigure the TNC
each time you use it and, you can't configure the TNC once and then connect a dumb peripheral like
a printer and have it just work.
1200 and 9600 baud do work though! I've used it to connect to Rich's
BBS (BBSQJA) and to a
9600 baud user node on Long Island. I'm sure there will be more to come on this aspect of the
There were a few software bugs discovered in the first lot of TH-D7's
sold. Among other things,
they fail to work with other than Garmin and Eagle Explorer GPS -- actually, any GPS that sends
positions with other than three decimal places of precision. Kenwood has announced that a
firmware upgrade program is in the works and will be available shortly as a warranty-covered repair.
SSTV and Sky Command
The TH-D7A also has special features to support the VC-H1 Slow-Scan TV
camera that Kenwood
came out with a few months ago. Y TV camera that Kenwood
came out with a few months ago. You'll probably want to talk to Anthony, N2NWZ, about the
SSTV features of the TH-D7 since he's got one along with the VC-H1!
Finally, Sky Command, is a remote base feature for some Kenwood rigs.
If you can afford a pair of
TH-D7's and a base rig that supports Sky Command, please adopt me!
The TH-D7 on the Internet. Check out Dave Van Horn's unofficial Kenwood
TH-D7 page at
http://www.cedar.net/users/dvanhorn/kenwood.html and the
"APRS HT" special interest group at Tucson Amateur Packet Radio: http://www.tapr.org..