I just placed an order for another Kenwood TM-V71A with Ham Radio Outlet (HRO).
Photo courtesy of Kenwood USA
During a visit to Portland, OR, my wonderful wife Tina KD7WSF asked me if there was anything I "needed" at the Portland branch of Ham Radio Outlet (HRO). I told her that I was torn about buying another Kenwood TM-V71A, despite having several already. On one hand, I didn't have an immediate need for another one. On the other hand, it seems likely to me that the TM-V71A will become another victim of the ongoing chip shortage and will eventually be discontinued as several nice Amateur Radios already have been. If I ever wanted another TM-V71A I should probably buy a new one now instead of taking my chances on the used market.
If you haven't been following the chip shortage, there is an industry-wide chip shortage driven by a powerful combination of factors, including a major chip factory being destroyed by a fire, manufacturers in China buying up as many chips as they can find on the market in fear of being cut off from buying other chips due to US government sanctions, and the huge ramp in demand for all kinds of consumer electronics because of staying at home during the pandemic of 2020-2021. Even automobile manufacturing is being affected, so I doubt a mature radio for a small customer base like Amateur Radio data communications would be prioritized for chips. Thus, if there's a radio that you've been thinking about and you can get it now, you probably should get it now as there's no guarantee that when your lusted-after radio goes out of stock, it will be returned to production when chips are more widely available. If you just can't get certain chips, and that forces a re-design, it generally makes more sense to create a new product.
At least, that's my calculus for this purchase. Unfortunately the Portland HRO didn't have any at their store, so the "walk out with one in my hands" fun wasn't to be. Fortunately other HRO stores have some in stock at the moment. If I was going to get another, the time is now. Tina agreed with my logic, so my newest TM-V71A is on its way to me.
For Amateur Radio Operators in the Pacific Northwest, HRO offers a very nice perk - drop shipping to the Portland HRO store. Instead of having your radio delivered to your home (usually in a state that has sales tax), you can arrange to drop ship your radio to the Portland HRO and pick it up there. Because it was "delivered" in Oregon which has no sales tax, HRO doesn't charge you sales tax. While everyone should pay their fair share in taxes... "... just sayin'..."
Why "stock up" on another TM-V71A? Basically, it's the best, easiest to use radio for "basic" data communications experimentation. (I plan to do a lot of experimentation with data communications this coming summer, including building loaner units for friends to experiment with me.) Mostly because the TM-V71A has the semi-universal 6-Pin MiniDIN "data" connector for easy interfacing with sound card modes. Few other radios these days offer the 6-Pin Mini-DIN.
Other features of the TM-V71A to recommend it for data communications:
- Dual-band radio - 144-148 MHz and 440-450 MHz
- Transmit power up to 50 watts
- With some cleverness, you can use both bands simultaneously for data. Connect one data device to the microphone and speaker and connect another data device to the 6-Pin MiniDIN "data" connector. Of course, any device connected to the microphone and speaker will be "slower speed" such as the traditional 1200 / 2400 / 4800 bps Audio Frequency Shift Keying (AFSK) packet radio modes.
- The operating frequency and mode (duplex, etc.) can be controlled remotely via an RS-232 serial port (special Kenwood 8-pin MiniDIN cable required). Thus you can script a computer to have the TM-V71A change frequencies, connect with a system like a BBS for messages, then change back to its standby frequency.
A few nice to have features that don't directly impact data communications usage:
- Remote-able front panel
- Choice of green or amber backlighting (I strongly prefer green)
- The microphone is a nice size for my large hand.
The TM-V71A isn't perfect...
- It's an dated design, easily a decade old. For example, remote control via RS-232 rather than USB.
- Most of the features are designed for conventional voice operation - see the Kenwood description at the link above.
- The most annoying feature is the fan is noisy - it's an inexpensive fan. There are other fans that are the same form factor that are much quieter, and people that use the TM-V71A in their shack either remote it to a location where the fan noise isn't as noticeable or they change out the fan.
- The reason you know (immediately) that the fan is noisy is that it comes on every time you transmit! It's on a simple timer circuit that's triggered by transmitting and runs for some period (I've never bothered to time it) after the transmit is triggered. It would have made more sense to me to have a circuit that monitored the heat sink temperature and turned on the fan only after there was a significant heat rise on the heat sink. Another simple expedient is to simply operate the radio at low, or perhaps even medium transmit power and clip one of the wires going to the fan. At those power levels, the heat sink without the fan can probably do the job adequately.
6-pin MiniDIN "Data" Connector
Please permit me a micro-rant. I've heard some incredible confusion about the 6-pin MiniDIN "data" connector. It's not a data connector, that is, it's not even compatible with digital signals. You cannot directly connect a computer to it. What it actually is is a standardized connection to "flat audio" inside the radio, that is, transmit and receive audio levels that bypass the voice conditioning circuitry (commonly referred to as pre-emphasis and de-emphasis) on a radio designed for voice use. Bypassing that circuitry allows modems to use the entire audio range that the radio is capable of transmitting and receiving, and thus can operate at faster speeds. If we were to do it all over again, I'd lobby for that connector to be described as a "Flat Audio" connection.
The 6-pin MiniDIN connector is probably the singular feature of the TM-V71A that has probably sold more of them in the past few years, as sound-card based data communications has become more popular on VHF and UHF. That connector is a very easy way to interface to sound card systems for data communications, such as the Northwest Digital Radio (NWDR) DRAWS unit. With a simple 6-pin MiniDIN cable (included with DRAWS) it just works. (Of course, you have to do some configuration on the TM-V71A such as enabling DATA mode, and selecting "9600" mode for data.
My existing TM-V71As work well and I'm happy with them. I often run them at 50 watts to be able to communicate reliably on simplex mode with several stations that are 25+ miles away.
Thanks for reading!
Steve Stroh N8GNJ
Bellingham, Washington, USA
2021-05-17
Portions Copyright © by Steven K. Stroh