A Portable Ham Radio Operator’s Interpretation Of A Mobile Installation: Using A Handheld Transceiver With A VHF Linear Amplifier
Truth be told, I was starting to get a little envious of those who had a good 2M mobile radio solution in their vehicles. Despite the nearly 125,000 miles on my cargo van (affectionately called “Limey”), I was not interested in either putting holes in the roof or elsewhere for a permanent antenna mount, and nor did I want to mess with any of the vehicular electrical systems. I had just replaced the battery in the past couple of weeks, and all of the 12 volt power outlets had failed long ago. The electrical system of my Chevy Express has never seemed like my van’s greatest strength and I did not want to mess with it. Furthermore, I needed a mobile radio station that could be easily and fully removed. I live in Boston and park on the streets; leaving anything in the vehicle of any value was simply a stupid invitation for trouble.
So I came up with this set-up:
The first iteration is simply a Yaesu FT-4X running 5 watts to a Tram 1180 2M/70cm dual band antenna on a Browning BR1035 mag mount base (with an NMO connector for the antenna), and a 17′ attached length of RG58 coax with a PL-259 connector. The FT-4X has a “reverse” SMA connector, simply meaning that it is a male SMA plug instead of the more traditional female SMA jack antenna ports. An SO-239 to SMA jack (female) adapter attaches the coax to the transceiver. A Yaesu SSM-17B speaker mic is attached to the radio’s headphone and mic jacks. A Roadpro RPHH2 speaker mic holder perfectly hangs the microphone from the air vent.
The no-drill stand is a cup holder mount by Lido specifically designed for handheld transceivers. The clip of the HT simply slides into a slot on the top of the mount. The cup holder portion is adjustable and tightens for a snug fit. It is quite an ingenious mount. And of course, this is all my equipment and I do not have any professional relationships with these companies, nor do I get a hint of money or products from them. I just talk about the stuff I want to talk about here.
This little set-up was working pretty well. But two things bothered me. One, there was a lot of stray noise (chirping, bleeting, screeching) being picked up by the receiver. And, two, it was only 5 watts.
So my next quest was to obtain a 2M band pass filter which I suspected would help clamp down on the wide open front end of this receiver. I order a SOTABeams 2 meter band pass filter from England. It was rated for up to 2W continuous use on FM and would filter from 144-148. It had female SMA jacks on each side, so at least one end would fit my radio perfectly.
Now, to accomplish power, I needed to get some… I ordered the RM Italy LA-145 85W VHF linear amplifier from DX Engineering. The amplifier is quite simple with an SO-239 at the transceiver side and another SO-239 at the antenna side. There is one switch with a red LED to turn it on and off. And another to choose between FM and SSB. I would most likely only use it for FM. The amp required a 13.8V power supply capable of producing 12A. This means that one of my Bioenno 15ah LiFePO4 batteries could act as the power supply. The maximum input of the amplifier is 4W. And the output of the FT-4X HT exceeds that at 5W. However, by putting the FT-4X on its medium power setting, it nominally outputs 2.5W. I figured this would probably be okay for the band pass filter, and would drive the RM Italy amplifier at around 80W output. Perfect!!!
I reconfigured the connectors using a 12 foot RG8X coax jumper with a PL259 end (connected to the amplifier), and a male BNC to male SMA plug adapter to go from the band pass filter to the coax. I used what I had available to me, so this wasn’t the perfect cable and I may switch it.
The coax was easy to run under the rubber floor mat of the cargo van by using a pvc pipe to feed the cable through.
Here you get an idea of the FT-4X, attached to the band pass filter. The RG8X jumper is taped around the base of the cup holder mount stand. The cable then runs along the console, gently held in place with a couple pieces of electrical tape for the time being. It then runs underneath the rubber mat, back toward the passenger seat where the linear amplifier and battery are placed.
Here is a closer view of the cable running out of the way along the center console.
And yet another, somewhat messy (sorry!) view…
Now this Everbilt 10″ x 6″ wall vent, a $15 purchase at a big box hardware store, proved to be the perfect stand for the RM Italy amplifier.
Cable ties were used to attach the amplifier to the vent.
Another view with the amplifier secured to the vent. Note that I terminated the power cords with power pole connectors. I have a good tutorial on how to do so here.
I purchased a set of Powerwerx fuse holders with 15A fuses to connect between the amplifier and the Bioenno battery. Fifteen amp fuses are recommended by RM Italy for this amplifier. This is the product I bought:
I shoved the fuse holder and amplifier power cord into the vent. This is looking from the bottom side of the vent.
Here is a view of the coaxial connector sider of the amplifier with the power cables tucked into the vent and a small length of power cord sticking out.
And a topside view of the amplifier secured to the vent, and the power cable tucked into the vent. The vent has small protrusions on each part of the backside that dig in to the rubber mat a bit, keeping it in place.
Finally, a look at the amplifier on the vent, now attached to the transceiver coax (which is coming in through a break in the rubber mat where a D-ring is exposed), also attached to the antenna (looped coax cable in the foreground), as well as the 15Ah LiFePO4 battery. This set-up fits neatly under the back of the van’s passenger seat, and elevates the amplifier off of the always rather dirty floor (its a working truck after all!)
Finally in the next two pictures you can see the coax from the antenna running through Limey’s support beams. I have used cable ties to strategically secure the coax where advantageous, The pink overlay showes the coax. The blue overlay shows the mag mount antenna stowed away upside down in the van attached to the ceiling. When I am ready to erect the antenna on the van, I simply peal it off of the ceiling, open the rear passenger cargo door, attach it to the roof, and feed the coax back in through the corner of the door at the point designated by the orange arrow. This area of weather-stripping is fairly wide and does not crush the coaxial cable upon closing.
All in all, it is a reasonably clean installation. I mean, at least for me…
How well is this new mobile installation working? Well, the proof is in the pudding. I am able to talk through repeaters over 40 miles away. The map below shows the location of the Quincy and Paxton repeaters, blue and pink circles respectively, and the furthest points from those repeaters that I was able to have a conversation through them (stars). I have not done a lot of testing yet, so the best distances may be even farther!
All in all, I am extremely pleased with this easily removed radio station. I have been trying to make a point of getting involved in local VHF radio communications. A new obligation on Monday evenings have kept me away from my “net nights” and I have been missing out. Now, I can check in while on the road, and I am delighted! Furthermore, the band pass filter does a wonderful job of cutting down on any extraneous noise or intermodulation products. Through the years, I have grown quite fond of the FT-4X, as it is my trusty hiking companion. It is pretty cool that it is now a souped up mobile radio as well!
Hope to hear you out on the open road!
73s and 88s,
KM1NDY