[VHFcontesting] PAR Moxon as rove antenna

[James Duffey]

I think that the PAR SM-50 Moxon is a good rover antenna and probably the best improvement I have made to my rover; certainly it was the best thing I have done for my 6M roving. I think most other rovers who have one feel the same. It is not a bullet proof-put it up and forget it antenna though, and you will probably end up having to repair it at one point or another.  But it is worth it. Four dBD gain at 75 mph on 6M! The mind boggles.
 
I have put about 7000 miles on my PAR Moxon since I bought it, with many of those miles at interstate speeds of 75 mph (or a bit more) and the antenna 12 feet or so above the pavement.  The antenna holds up well at those speeds with no modifications. Mine has never come apart just from driving at speed, even in high winds or over rutted New Mexico back roads. Having said that, it is less forgiving of colliding with overhead obstacles such as low lying trees, covered gas station pumps, drive through awnings, parking lot ceilings, and motel porticos. In these collisions, the side tubes usually get bent. You can bend them back into shape easily, once. After that they work harden and a second or third attempt to straighten them usually results in a broken side piece. I carry a spare. If you get a PAR, I suggest that you get an extra side piece at the same time; you will probably use it sooner or later. They are simple to repair on the road.
We do live in a part of the country with few trees, so I don’t worry about the Moxon getting snagged in trees too much. We just try to avoid low overhangs. About every third trip I forget. But I do spend a lot more time reading those posted clearance limits with the Moxon on the car than I did before. If I lived in the east, where there are more  trees, I would probably attach one of the side arms to the driven element so it wouldn’t get lost in the trees if I hit one. I think it was K4GUN who woke up one morning after an evening of roving in the dark and found the reflector and side pieces on his Moxon missing, probably residing in a low lying tree along a back road in Delaware.  If you lose the side pieces entirely, the TS-2000 autotuner will still load up the remaining piece of the driven element OK and you have a shortened dipole. Similarly if only a small portion of the side piece breaks off you can put what remains back in, adjust the other side to match and have a Moxon tuned higher in the band with a slightly asymmetrical pattern. Still better than a loop.
 
The Moxon is an excellent performer compared to a loop. It particularly shines during marginal band openings, when the band is just opening  and when it is closing. Compared to a loop, it is much easier to hold a run frequency and to attract the attention of strong stations who may not have their antennas pointed towards you.  At 4 dB gain over a dipole, it is probably 5 or 6 dB gain over a loop, and that makes a big difference, particularly when signals are near the noise level. If you are running a loop and want to make a big improvement to your rover, go to a Moxon. The cost of the PAR SM-50, which was $100 when I bought it, and I think now is close to $120 with the rise in Al prices. That price is about the same, or not much more than a loop, I see HRO is selling the M2 6M loop for $140, but the results from the Moxon are much better than a loop.
 
At 7 ft wide and 31 inches deep, it is a big antenna, but the wire reflector and 5/16 inch side pieces make it fairly light weight. You need to plan for it in the installation. I use 1.25 inch EMT for a mast and that is more than adequate, even with 8 ft antennas for the other bands installed. We drive with it at 10 to 12 feet high and extend it to 15 feet or so when stopped.  When I first got the antenna and put it together in the driveway prior to roving, my first thought was “This is a big antenna”.  About that time Virginia came out of the house looked at the Moxon and said “That is a big antenna. You’re not going to drive with that on the car are you?”  I answered, “No, you are.” After initial test runs at lower speeds, we concluded that cruising at 75 mph with it on the car was not a problem. With the additional wind loading the gas mileage suffers though.
 
If you are into SOTA or portable operation, the Moxon breaks down nicely into a 3 ft long package about 2 inches in diameter and assembles quickly.
 
Dale provides excellent support for the antenna and has shipped me side pieces on short notice. No balun is included so you probably should add one, a string of ferrite beads do nicely, and, in case you are wondering, and everyone does, there is nothing magic in that black box except wires connecting the driven element to the SO-239.
 

James Duffey KK6MC
Cedar Crest NM