My HF Mobile History Sometime ago I started out using a Kenwood TR-9000 2M SSB radio when I started operating mobile, this set up was fine and I worked some great DX from Epsom Downs and various other locations. However, after changing vehicles and passing my Morse I wanted to try other bands like 6M and possibly HF. Looking at what the market had to offer at the time, there was only one radio that would provide 6 Meters and 2 Meters SSB and offer HF, it was of course, the ICOM IC-706 Mk1.
Now at first I wasn’t really interested with HF mobile since there was plenty to do on “six and two” but that changed when I saw HF in action on Epsom Downs, Surrey each Sunday afternoon. It was fascinating to watch DX and UK stations being worked on various small types of mobile antennas rather than huge dipoles and beams. After purchasing the radio and deciding to try HF, I then had to decide how to set up the radio and which antenna to use.
The current vehicle is a Mazda 6 (has been Escort & 2 Mondeos) and the installation has been designed so it’s easily removed without too much “damage”. The 706 stays in the car and isn’t used elsewhere.
THE TRANSCEIVER
It’s an ICOM IC-7000; it has the separation cable and external ICOM speaker mounted in the dash. The radio is located in the boot mounted on chipboard with a plastic “basket” over the top to protect it. The head unit is mounted in a customized PDA mount which attaches to the glove box. All the cables running into the radio (head unit, data, voltage meter) have two or three RFI rings fitted and the speration cable also has a Ferrite Clip on choke, all are secured with cable ties. All the cables are fitted to the board using cable clamps, I used to have the 12V EMC unit fixed to the board but now use the standard basic cable which features large gold plated fuses. I used to suffer RF feedback on 10M hence the number of chokes used on the external cabling. Also connected is a home brew PC Interface which permits programming and full control of the radio via laptop, this comes in handy since the radio is quite tricky to program. I also use a digital voltage meter connected to the same plug as the radio so I can monitor the voltage on the radio "side" of the connector. If it drops then the radio drops its output, on the old 706 I would still get full power but the radio's modulation would start to "FM". However, in March 07 upgraded the cable going from the battery to the plug using heavy 40AMP Shark cable from Maplin. I got my IC-7000 from Radioworld in March 2008.
THE POWER SOURCE
Powering the 706/7000 is a significant challenge, not so much in that it requires up to 25Amps with 1Amp on RX, but because its very voltage sensitive. If the voltage drops below 12.5v, the radio will drop the output power. The power source comes from a 75amp hour caravan battery; this sits in an old cool box with the lid removed. A pair of battery clamps are fitted with a 40Amp fuse bolted directly to the + clamp. This in turn is mated to some very heavy-duty cable. Next, there are a pair of Anderson Powerpole connectors, they are rated to 75Amps and can take HUGE diameter cable! Remember the voltage drop and the high current, most connectors will not be able to take the large cable size or maintain a good voltage. The connectors are genderless and are modular; you can double up on the connectors on each cable i.e. 2 for positive and 2 for negative but I didn’t bother.
There are other power source solutions on the market such as sealed lead acid gel batteries used in portable “power station” units. They offer an automatic charger with connections for cigar plugs and switchable output voltages. These, in my experience, simply won’t do the job at all. I tried on of these and it wouldn’t even handle 20w of SBB on 2 Meters. Also, forget the car battery unless you want a rolling start or you don’t mind starting the car every few minutes.
I remove the battery each week and use a heavy-duty automatic charger; the battery is not sealed so care must be taking to avoid spillage of acid and inhaling fumes. This may all sound extreme but it’s simply the only way of powering the radio for any reasonable length of time without calling on the RAC!!
I have only exhausted the battery on one occasion after several days of activity on holiday, I almost always leave the power on max since its quite a struggle to make contacts on bands like 40M with so many base stations running hundreds of watts.
Best DX would be Kuwait and Malaysia on 15M with other good contacts to the States on “10FM” and using AM on 10M which is quite a novelty (around 29.000Mhz). I have also had good contacts late at night on 40M into Sweden, Germany and France however it is quite challenging to complete with the QRN!!
THE ANTENNA SYSTEM
There are a wide range of monobanders, multibanders and even antennas with motors built in to adjust the length. Currently I use the following: 80M is a Pro-Am whip, 80M-40M-20M15M-10M-6M-2M-70CMS are all covered by my Comet CA-UHV which gives me multiband access without swapped bits of antenna quite as much. The bandwidth is a bit less then the Pro-Ams but it can be used mobile much more easily since its totally flexible. I have used CB antennas on 10M including my trusty OSCAR with a good amount of success however the best 10M I have owned has to be my centre-loaded Diamond the only problem being its HUGE! I tried a 40M Pro-Am which ended up going back to the Emporium since it would not tune up, it was the second one I had since the first had build quality problems.
I decided to avoid the OutBackers since they are far too pricey, I looked at the BugCatcher but it’s not really all that discrete! The Comet, in contrast, is much more flexible in terms of the bands which can be configured with optional elements to give access to 20M and 17M.
2M Amp
I run a 2M, 110W amp which is a Tokyo mounted in the boot. I tend to run it all the time for 2M whether its FM or SSB. You can see in the Gallery the photos of the Fuses I had to get for it. We had to make up a bracket for it to mount on to stop it sliding around.
GROUNDING
I used the outer braid of RG213 coax to ground the hatch by both hinges, the mount, and the radio (using one of the bracket screws). The straps are soldered and drilled at each end and secured to the bodywork with a single screw.
HANDS FREE MIC
Old setup:I use a neck mic supplied by W&S, the toggle switch box is mounted on Velcro on the side of the centre console near the front of the drivers seat. It also contains up and down channel switches on the box and includes an adjustment inside the box for Audio Gain.
Current Setup since Jan 2008: I use the Talksafe Bluetooth system, with a Motorola BT headset I can go handsfree/cablefree and even operate the radio from the house! I power the unit from the radio itself using the conenctor on the 7000 designed for Icom's longwire tuner. I can still use the fist mic and even plug the dash speaker into the front panel whilst still having the Talksafe connected. However care must be taken not to use the fist mic whilst the headset is connected to the Talksafe!
CONCLUSION
There are many different routes to take when establishing an HF Mobile station, it really depends on the individual needs and how serious you are. Some people I talk to swear by using mag-mounts, however I have never had any success with them, some like to use the car battery and don’t mind pushing the car to start! There are some QRP transceivers around which are not so power hungry and many more portable antenna solutions.
With so many barriers like QRM from devices around the home, planning restrictions and domestic QRM(!) its little wonder why HF Mobile is becoming more popular.
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This is the replacement for the 706, it does'nt show the battery voltage and the SWR meter still only works on HF and 6M, but hey, I can watch the TV on it!(???) When the price drops under £800 then I'll consider one. For the time being, the 706 is doing a fine job, with nobody on 70cms I am happy doing 2M and 40M. STOP PRESS!!!! I have now purchased one, as I said, I waited until the price dropped, and it did!! 