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Mobile Antenna Testing



We recently purchased several Midland MXT400's and wanted to see how well they performed with different antennas and I thought that perhaps some members might find our test interesting. We used four antennas:


1- 2 meter/440 dual band ham antenna that was reasonably matched for GMRS

2- Modest 6 inch quarter wave mag mount antenna that comes with MXT115 radios

3- Midland MXTA10 12" 5/8 wave "3 dB" gain antenna with MXTA12 NMO mag mount

4- Midland MXTA11 27.5" "6 dB" gain antenna with MXTA12 NMO mag mount


The MXT400 has a 6 segment LCD for relative received signal strength which gives at least some idea of the difference in how well you are receiving, in addition to how well it sounds by ear. The base station has a GP-9 2 meter/440 dual band antenna at 40 feet which puts it at close to 1300 feet ASL. The mobile is a Chevrolet Malibu and both rigs were run at Mid level power of about 20 watts. Because we live in the Driftless Area of Western Wisconsin, not far from the Mississippi River, the terrain has been unglaciated therefore has many "coulees" or narrow valleys caused by erosion. Our farm is located on the ridge top and by going only a mile, one can drop down hundreds of feet to lower elevations. Based on actual experience it can be difficult to even access our local 2 meter ham repeater (over 1400 feet ASL) at just 5 miles away when in a coulee at 865 ASL.


I went down to the dam of a nearby lake at 900 ASL, about 2 miles out from the farm, but was just barely able to make contact with my wife at the home QTH using Antenna 1 with the antenna on the rear trunk deck with the first LCD segment flickering. This first bar has the imprint of busy. I actually expected no contact, so was pleased that we could at least make contact.


Switching to Antenna 2, but now located on the center of the roof, the signals were much stronger and gave us a solid 2 bars at both locations. Considering the lossy and tiny coax, this surprised me since I expected the performance to be worse than Antenna 1.


Antenna 3 was located on the rear deck and on both radios, showed 3 bars. Moving it to the roof seemed to make no difference.


Antenna 4 was located on the rear deck only and showed 4 bars. This is the antenna I plan to use on the Malibu with plenty of garage clearance.


I later set up Antenna 3 on my wife's SUV, but centered on the roof using one of our MXT115 radios which is quite compact and fits nicely in the dash "alcove" which just happens to have an auxiliary jack for powering the radio. 


Has anyone tested the microvolts of signal needed to light up the various segments on the MXT400 radio? I have an old URM-25D but I haven't done it for over a decade when testing an older Kenwood TS440SAT rig. But it would be interesting to see how many dB's between bars to get at least a rough idea of the antenna gain. 



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