My Comet M-24J 144/440 antenna doesn't seems to receive signals as well as it should. I seem to receive more transmissions on HT radios than the mag mount and micro mobile radio. I only have a Rig Expert AA-35 and I am looking to purchase a piece of equipment to test antennas in the 6 meter and up range. Can the Comet mag mount antenna be tested to check if it is performing correctly?
6
-
1$\begingroup$ One reviewer of this antenna at eham.net/reviews/… had the same experience as you did. $\endgroup$– Mike WatersCommented Mar 8 at 15:07
-
1$\begingroup$ Great information! The eHam site is new to me. I love it! Thanks!! $\endgroup$– Radio RailsCommented Mar 8 at 21:43
-
1$\begingroup$ You DO have the mag mount on a large metal mass —such as the center of a car roof— don't you? $\endgroup$– Mike WatersCommented Mar 8 at 23:37
-
3$\begingroup$ You did not mention what mag mount base you're using, but I would suspect the base before the antenna. How much surface area does it cover? Mag mounts use the surface area as capacitor plates to couple to the vehicle roof and form the ground plane. If you want something to test antennas or anything RF get yourself a NANO VNA. You will never use the Rig Expert or anything else again. A VNAa would tell you what is going on. Ensure your mag mount Is large enough to provide the capacitance needed for low impedance connection of 1 to 3 ohms at the lowest frequency of interest. $\endgroup$– user23405Commented Mar 9 at 1:22
-
1$\begingroup$ @MikeWaters I've used a 2 14" pizza pans that were stacked. (good quality thickness) I have tried my car's roof, but I remember the pans performance most. $\endgroup$– Radio RailsCommented Mar 9 at 12:05
|
Show 1 more comment
1 Answer
$\begingroup$
$\endgroup$
The simplest way to test an antenna is with an SWR meter. This will at least let you know the RF energy is, or is not, being wasted due an impedance mismatch or resonance problem (although an SWR meter won't tell you which problem you have, if you do have either of those problems). Everything else is just simply implementing good practices, such as mounting an antenna, unobstructed and as centrally as possible on a vehicle if you want relatively omni-directional results. Beyond that, if you are that curious to know what the antena is, 1/4 wave, 1/2 wave, 5/8 over 5/8 wave collinear, or whatever, you need to model it in an antenna modeling program. Modeling can be tedious because you first have to learn about antennas, and you then have to learn how to use the software. Also, I wouldn't judge an antenna's performance based on an HT, which are notoriously less selective than a regular mobile rig.