Thread: Digital Radio
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Old 11-18-2013, 02:40 PM
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DaveInDenver DaveInDenver is online now
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Join Date: Jun 2006
Location: Larimer County
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At least one of those points is wrong. The FTM-400 does support the same type of cross band repeating as any other Yaesu radio, for one. Not sure what to say about the others, they are generally the same (for good or worse) as the FTM-350 was. Banks in memory are one thing I really wish the FTM-350 had for sure.

Digital is, well, digital. Is it necessary for amateur radio? No probably not, no more so than in public service and business radios. There is plenty of debate on the merits in all services, not just ham. Firefighters generally hate digital radios. Being able to use voice and data simultaneously is one of the main reasons. You can do that with APRS but it takes two channels, either two radios or a true dual bander that can TX on both channels semi-intelligently (e.g. do APRS TX on the secondary channel while you use the PTT on the mic on the main channel).

D-STAR and Yaesu's digital send along GPS and call sign data with each voice TX, so you can see a location each time other hams talk. APRS is a set beacon rate, so you might go minutes between position updates, depending on set beacon rate and packet collisions in the network. For trail work at slow speed this isn't bad but in a tactical situation (like race support or emcomm), knowing exact locations for everyone helps directors know who is close or not to an incident. The Yaesu system also has a group thing where all the members of your group show up in a list with updated positions periodically even if they are not transmitting. The radios essentially query each other to keep the table up to date.

When in range digital voice is like the step up from AM to FM in analog. There is zero hiss or background noise but remains within the same existing channel bandwidth. In full digital voice the Yaesu system uses 12.5KHz of bandwidth, which will sound quite high fidelity (although with no GPS data, just your call sign in the header). In simultaneous voice & data each stream gets 6.25KHz of bandwidth to remain within a standard VHF channel. Most commercial radios have gone to 6.25KHz channels for voice only, which you may have heard referred to as narrow bandwidth. The FCC requires it of them, we hams are allowed to set whatever we want. But since repeater pairs are usually completely assigned, freeing up some spectrum by narrowing channels would be handy on 2m.

The reason I have not pulled the trigger is that the FTM-400 display is N-I-C-E. Touch screen, deep color. It'll be sweet to operate. Yaesu kind of dropped the ball on a handful of technical features, so the TM-D710 still has some advantages. I'm stuck with indecision. If it was a question of the FTM-350 vs. TM-D710, I'd be getting the Kenwood at this point. But I can not emphasize how cool that interface is on the new FTM-400. It makes everything else look like 1980s CBs.

The TM-D710 goes a step further than Yaesu and provides a true, full TNC so you can do true packet and voice at the same time (with a computer plugged into the radio). The FTM-350 and FTM-400 can only receive APRS data on the serial port so any outgoing APRS data is generated in the radio (messages, beacons). You can disable the internal APRS & GPS and use an external TNC on the port, but that is the same case with any FM mobile, so the built-in stuff is of no use and expensive.

Price floats around $700 for a FTM-400. But this includes GPS built-in to the controller. A TM-D710 sits at around $550 but the closest configuration includes a Greenlight Labs GPS-710 that mounts on the control head, which is another $125. So the cost ends up $20 to $40 lower. The FTM-400 is a bit cheaper than the FTM-350 + FGPS-1 was before it. The radio itself was about $650 back when they were offering it and the GPS module was about $75 as I recall.
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