There are at least two Canadian Provinces, Ontario and New Brunswick that have recently
enacted laws pertaining to the operation of Amateur Radios while mobile. These laws are similar to "hands-free" laws in several
American states but do not have any exemption for licensed amateur radio operators. One can only guess how soon other provinces
and states will follow this unfortunate policy.
After several emails from Canadian hams, I decided to post this article on my web
site. It was originally written for QST but has been on hold for a while now. Hopefully QST will find a place for it in the
pages of that fine periodical soon.
Right off the bat I want to emphasize that this project is a compilation of the work of more people
than just the author. It contains elements of articles by myself as published in QST in November of 2008 and May of 2009 as
well as elements from an excellent article by Johnny Knight, WB4U in the August 2009 issue of QST. After reading his article
I contacted Johnny and we discussed the idea of combining these elements into a "semi-universal" Bluetooth adapter for amateur
radio. He wished me luck with the project and said it sounded like a good one.
My first step was to order one of the Bluetooth adapters mentioned in his article, the Jabra A-210,
along with a Bluetooth headset of the "earset" variety (A Plantronics M2500). I am a big fan of the "earset" design rather
than the full over-the-head type. They arre much lighter and more comfortable. When the units arrived, I was disappointed
to find the Jabra A-210 was DOA. It would not take a charge at all. I called Jabra in New Hampshire and was informed that
the unit had been out of production for some years. They agreed to cover it under warrantee and so I shipped it off to them
for repair. Apparently these devices have been on dealer shelves for so long that the batteries have long since died, eventhough
they are brand new. I did find several references online to opening up these dead units and wiring up an alternate source
of 3.7 VDC. Your results may vary, but there are still several internet shops that offer the A-210 and of course there is
always E-Bay. The unit came back from Jabra in fine working condition but eventually I modified it to use three regular AAA
cells in a separate battery holder. The A210 as designed will go into standby mode if it does not hear any audio for 60 seconds.
To overcome this a 47K 1/8 watt resistor is soldered to a certain pin on a chip on the A210 circuit board and the other end
of the resistor is soldered to ground. See the pictures below for the details. With thanks and credit for the fix to VE3LC,
The choice of a headset (or earset) is up to you. I chose a Plantronics M2500. Almost any bluetooth
headset should be compatible with the Jabra A-210. Since the A-210 and the earset was intended to replace a wired headset
for a cellular phone, I figured the the same adapter circuit found elsewhere on this web site would suffice to adapt the A-210
to an amateur radio. This proved to be the case. Good audio reports were obtained in testing and continue to be recieved in
The next phase of the project was to establish a solid means of control of the PTT function. I
am not a fan of VOX for mobile or outdoor situations. I prefer the security of a real PTT switch in my hand. Back in November,
2008, QST published my article on a wireless PTT switch. The point then was to allow the PTT to be placed on the steering
wheel of a car without the complicated and snag-prone coil cord such as used in auto racing or flying. This project could
easily use the same idea. Since the keyfob transmitter (the PTT switch) uses a frequency of 310 MHz it does not
conflict with any amateur frequencies.
Since I already had the "wireless PTT switch" installed in my vehicle (as shown on another page
here on the web site), it was an easy change to remove the wired "earset" in the car and substitute the Jabra A-210 which
plugged into the same 2.5mm jack on my mic selector/adapter. Subsequent testing engendered reports of "very good transmitted
audio" and I was able to say the same about the received audio I was listening to with the Plantronics M2500 in my ear.
The one drawback (if there is one) is of course that one must remember to remove the Jabra A-210
and the mating headset (earset) so that they can be charged up between uses. At least the A-210 could be connected to a charging/power
circuit and thus get it's power directly from the vehicle. UPDATE: I have added a circuit to this page that does just that.
This circuit draws very little power from the vehicle battery and could be left on continuously if desired. Mine is on a switched
circuit that also powers the receiver for the Wireless PTT switch. I am sure that it would be similarly possible to build
or adapt a car charger to keep the earset juiced up as well. Maybe there is a future project there. UPDATE: Future Project
Now Completed. I adjusted the output voltage of a second voltage regulator circuit so that it put out 6.0 VDC and adapted
the connector from the headset's charger to the Voltage regulator. It completely charged the headset in about two hours using
the car battery as its source. I doubt the car battery even noticed. NEW UPDATE:I have talked to Plantronics Tech Support
and they assure me that the M2500 headset can be left plugged into a 6 volt source without damage to the battery in the headset.
You will, of course have to unplug the headset from the charging circuit to use it. This means that one could easily wire
up the Jabra A-210 dongle and the Plantronics M-2500 headset with their respective power sources so that they are active all
the time. The drain on the car battery would be minimal and the extra steps of turning the A-210 on and off and removing the
headset from its charger after topping up would be eliminated. Just something to think about.
We should look at the cost benefit situation of all this. The total cost for the Jabra A-210 and
the Plantronics M2500 was in the area of about $75 online. The keyfob transmitter and receiver (a single channel garage door
controller in its previous life) was about $60. The adapter circuit to match the radio to the Bluetooth adapter can be made
for about $15 dollars in parts, $25 if you want to incorporate a mic selector circuit as well (see the mic selector project
elsewhere on this site). The total cost thus is around $150 to $160. It could be much less depending on the size and contents
of your "junque box" and the generosity of your local garage door service facility.
There is at least one commercially available Bluetooth Headset/PTT/adapter available at the present
time. It is designed for use with handi-talkies including the Kenwood amateur radios of that type. It will still take a home-brewed
adapter to make it play with the likes of the typical mobile rig. Cost is in the same ball park as the project detailed above
without the additional cost of the necessary adapter to convert the Kenwood HT plugs to a format suitable for a mobile or
UPDATE: After many tests and several attemps at a fix, I have
terminated the use of Bluetooth in my mobile installation and gone back to the wired cellular headset I was using
before. I have been unable to get rid of a fairly loud whine that is apparently due to the Bluetooth headset being
unable to filter out the noise from the alternator in the vehicle. With the wired headset or the stock hand mic there is no
alternator whine, only with the Bluetooth headset and Bluetooth transceiver is the whine present. I filtered the input from
the mic selector and the power supply to the Bluetooth transceiver (adaptor) and the alternator whine is still there. Regretfully,
I must conclude that the particular combination of a Plantronics headset and the Jabra A-210 Bluetooth adaptor is unfortunately
prone to this problem and since I do not have unlimited funds to try every possible combination of headset with the
Jabra A-210 I have decided to retire the combination and go back to a wired headset in the vehicle. The combination of the
wired headset and adaptor has worked very well in an number of different situations and the details on that system can be
found elsewhere on this web site. The wired headsets (non-Bluetooth) are still available from a number of on-line retailers
at a very reasonable price point and the adaptor to connect them to most ham transceivers is very simple to build and use.
All of the parts necessary are available at any Radio Shack store. I will leave this page of the site up so that others with
more skill and knowledge may succeed where I have not.