The Treehouse Blog

It was with some great fanfare that AMPS met its death on February 18th, 2008.  But did it really die?  As far as I can tell, all that happened on that date was that the FCC no longer required cellular providers to make AMPS available, and many did eagerly turn it off.  But, unlike the conversion to digital television, there appears to be no requirement at this point for providers to abandon AMPS if it is still making them money.  That being the case, are there any AMPS providers still out there?  Public filings (available here) concerning AMPS status were made prior to the sunset date and reveal that some companies had a lot of AMPS customers still and had no plans to turn the service off.

Why do I care?  Because I loathe 47 CFR 15.121 and would like to see it abolished.  This is the section of FCC regulations that forbids the manufacture of devices that can receive, or be easily modified to receive, cellular frequencies.  This requirement only covers the Part 22 Cellular Service (824-849, 869-894 MHz) and not the all-digital PCS and AWS bands that cell service has expanded into.  With AMPS, conversations were transmitted using FM, and so could be easily decoded by any FM receiver that could tune to the appropriate frequencies.  With the digital services, more sophisticated handling of the signal (and even decryption) would be required, which apparently made it unnecessary to have the same kind of regulation.  As far as I know, this is the only restriction placed on what frequencies can be tuned by a receiver.  On freedom grounds alone, I have a big problem with that.  If AMPS does finally die – and I hope it does – I hope that 47 CFR 15.121 can die with it.

I did recently get a TM-D710A and have been playing around with it.  I have found one missing feature that would be nice, and a workaround for it.  Suppose you want to add an amateur frequency as a memory channel for listening/scanning purposes only, but don’t want to ever accidentally transmit on that channel.  I think it would make sense to have a flag that could be set on a per-channel basis to inhibit transmission on that channel, but unfortunately there is not.  I have come up with a viable workaround though.  It is possible to configure a memory channel as “split” – with a receive frequency and a separate transmit frequency.  It is required that both frequencies be on the same band… though I’m not sure why – this would be a useful feature as well, so that one does not need to tie up both sides of the radio for half-duplex cross-band applications.  Anyway, it is possible to configure the transmit frequency to be within the same band and still outside of the portion of the band which the radio can transmit on.  This results in a beep and no transmission when PTT is pressed – which would be exactly the desired behavior of a transmit inhibit flag.

I’ve been checking into some mobile amateur radio rigs recently.  I had for awhile been intending to get the Kenwood TM-D710A, but a new contender has recently entered the market, namely the Yaesu FTM-350R.  I don’t presently own either rig, but as there is a lack of direct comparisons between them currently posted online, I wanted to share my research.  If you find any errors, please let me know so I can correct them.  If someone who actually owns or has used both rigs eventually posts a comparison, I’d like to link to it as well.

RF Capabilities

Both rigs provide 50W power on the 2-meter and 70-cm ham bands.  The 350R additionally can transmit 1W on the 1.25-meter band.  The extended receive ranges are also divergent, with notable differences being the lack of 13cm/1.3GHz band (and possibly the 33cm/902MHz band per a footnote) coverage on the 350R .  There are published mods to provide extended transmit capabilities for both units.  Both radios have a cross-band repeater capability.

APRS

APRS is the feature that places these two radios in their own category.

GPS

One aspect of APRS is the use of a GPS for automated position reporting.  In the D710A, an external third-party GPS receiver (such as the GPS-710) needs to be connected to the control head.  For the 350R, Yaesu sells their own FGPS-1 module which installs in the back of the control head.  Documentation indicates it is possible to use the FGPS-2 module, which is the GPS receiver used on the VX-8R, but the required CT-133 cable could not be located from various retailers websites.  It does not seem to be readily possible to use a non-Yaesu GPS receiver.  Personally, I think having a GPS connection available from the radio body would make sense.  My intended control head mounting location is not likely to have the best view of the sky.

Digipeater Functions

The D710A appears to have a robust set of digipeater functions.  This feature would primarily be useful in situations where a temporary digipeater was needed to serve an area not covered by a permanent digipeater.  The 350R appears to not have this feature.

Other APRS Features

The D710A supports QSY information, weather station attachment, and a Kenwood GPS format for tactical display integration with AvMap G5.  Both radios are equipped with the SmartBeaconing feature which bases position update intervals on the speed of travel and direction changes.  The 350R has some navigation enhancements providing direction indication to other stations.

TNC

The built-in TNC on the D710A can be used by a PC or other external device, and supports KISS.  The 350R supports a “modem” mode for both 1200 and 9600, which hopefully means it can be used as a TNC as well, but I’ve not found anything explicitly confirming success with this.

Software / Firmware

These modern radios, like most recent electronics, have some computer-ness to them.  Programming software and firmware updates for the D710A are freely available from Kenwood.  These updates have added new features to existing products at no additional cost.  So far, there is no indication of any software available for the 350R.  [Update 2010-04-24: KC7HP pointed out that software is now available.] The repair for the navigation issue discussed below involved mailing the unit in for repair – for what should be a firmware update.  Given the newness of the product, it is possible that the rolling out of consumer firmware updating is forthcoming, but the situation with the VX-8R upgrade to VX-8DR doesn’t make this prospect seem likely.

Bluetooth

It’s only fair to mention that the 350R has an optional Bluetooth module.  The only Bluetooth capability provided is audio, such as the use of a Bluetooth headset for using the radio.  I’d be much more interested in this if Bluetooth data capability of some sort were provided.

Quirks

The 350R is a really new radio, and that means there is not much information available, and that it has a few bugs and quirks.  Already there are reports that APRS navigation feature leads you in the wrong direction.  There are also reports that the radio will hang, requiring power to be physically removed to reset the unit.

Conclusion

While the 350R does introduce some new capabilities (222 MHz, Bluetooth, integrated GPS, navigation feature), there are still features of the D710 that it seems to lack (digipeating, tactical GPS protocol).  The free firmware/software of the D710 is hard to beat.  Given the quirkiness of the new hardware, and feeling that the features unique to the D710 have more potential use than those unique to the 350R, my inclination would be to get the tried and true D710 if purchasing a unit today.

I am by no means an audiophile, but being able to listen to music from a source other than the radio is still a requirement for longer trips by vehicle.  I’ve been using a cassette adapter in my car, connecting it to whatever the audio source of choice has been:  laptop, Axim, G1 and sometimes even the Pro-95 scanner or HTX-202 radio.  My truck presented an obstacle to this in the form of a CD player.  I had no intention of trying an FM radio transmitter, so a new radio was needed.  So, really, the only requirement for the new radio was an external input.  To make things interesting, I focused my search on hardware supporting A2DP, which led me to the Clarion CZ509.

The install was straight forward and relatively painless.  The hardest part was getting the wiring connector detached from the factory radio.  I used the kit from Crutchfield since I wanted a no-hassle return option, mostly.  The USB connector is a cable emerging from the back of the radio, while the 1/8″ miniplug external input is on the faceplate.  It would have probably been more useful to have both on the back, or swapped.

The basic functions work as expected.  CD audio sounds fine.  AM radio reception seemed to have the same sensitivity as my factory radio, despite comments elsewhere on the web indicating problems with this.

The USB and CD are capable of playing back MP3 audio, of course, as well as the similarly encumbered WMA and AAC formats. Naturally, for ideological reasons, a decent amount of my audio is in Ogg Vorbis and FLAC formats, which this unit can’t play on its own.

Bluetooth audio sounds pretty good paired to my Android G1 running cyanogenmod, though it can be skippy at times which I blame on the G1s underwhelming RAM and CPU.  The G1 running cyanogenmod has the ability to play my Ogg Vorbis and FLAC media.  The menu interface for pairing the phone is incredibly unintuitive on the CZ509 – have the manual and patience handy when attempting.  The radio does have an auto-connect feature which should cause the CZ509 to connect to your Bluetooth device upon powerup, but I have never had this work.  I’m not sure which device is at fault for certain, but I suspect the CZ509 isn’t doing something right.  Fortunately with the help of a shortcut on the G1, manual connection is only a few screen presses away.  The Bluetooth playback only has play/pause/forward/back controls and has no song title text.  I’m guessing this means the CZ509 only supports AVRCP 1.0.  I’m not currently using the phone audio capability of the CZ509 – I’m not sure where the microphone would go.  Sometimes the G1 will not produce any audio despite an established connection which is readily solved with shutting down Bluetooth on the G1 and starting it back up.  I’ve not had this happen in the middle of a connection.  It would also really be nice if the headset volume controls and Bluetooth volume controls were stored separately in the G1 as I need it full-scale for A2DP and near the bottom for wired headphones.

I’m overall pleased with the purchase.  I certainly could have gotten a more featureful or less expensive radio had it not been for the A2DP experimentation goal, but this radio should serve my needs.

Several years ago, the PA state government began deploying a proprietary trunked communications system… and encouraged County governments to use it. Since it’s proprietary, the governments are locked into the price structure of a single vendor (brilliant! bravo!) and radio enthusiasts like me won’t be able to use our scanners to listen in (at least, not anytime soon). I’m a big fan of government transparency and openness… and this is moving in totally the wrong direction. All isn’t immediately lost however. Even if fire and ambulance dispatch is handled with OpenSky staring on June 1st, 2006 as this article says, it sounds as if paging will still be simulcast on traditional FM frequencies so that voice pagers, sirens, and scanners can function without an upgrade. It seems that radio geeks aren’t the only ones concerned… just listen to those fighting fires.

And while I’m ranting… Since this system is IP based, how long will it take before a laptop in a state cop’s car contracts a virus because he installed an unauthorized Wifi card, and cripples communications state-wide? Consultants won’t go hungry cleaning it up, that’s for sure.