A few weeks ago I posted a basic review of the TIDRADIO TD-H8 VHF/UHF handheld radio. Today I was able to measure the radio on my TinySA Ultra Spec Analyzer to see how clean this little radio is, especially since it has been approved for GMRS use.
Here is the first plot transmitting on 146.52 Mhz, set on the far left.
The 2nd harmonic is about -48db, 3rd harmonic is not much better at about -52db. Surprisingly, the 4th, 5th, and 6th harmonic are prominent.
Here is measurement transmitting on 444.500Mhz:
The harmonics when transmitting on 440Mhz are worse than 146Mhz. As you can see, the 4th harmonic is still only about -63db and I was really surprised to see the 5th harmonic is only -70db
The manufacturer informed me that they were working on FCC Part 97 certification, but they may not get it with this type of performance. Remember, radios transmitting less than 25 watts at these frequencies must be -40db from the fundamental and no more than 25 microwatts. It appears that the harmonics are all within the gain specs, but don't meet the microwatts requirement. For example, the second harmonic on a 2 meters transmission is over 158 microwatts.
Here is the first plot transmitting on 146.52 Mhz, set on the far left.
The 2nd harmonic is about -48db, 3rd harmonic is not much better at about -52db. Surprisingly, the 4th, 5th, and 6th harmonic are prominent.
Here is measurement transmitting on 444.500Mhz:
The harmonics when transmitting on 440Mhz are worse than 146Mhz. As you can see, the 4th harmonic is still only about -63db and I was really surprised to see the 5th harmonic is only -70db
The manufacturer informed me that they were working on FCC Part 97 certification, but they may not get it with this type of performance. Remember, radios transmitting less than 25 watts at these frequencies must be -40db from the fundamental and no more than 25 microwatts. It appears that the harmonics are all within the gain specs, but don't meet the microwatts requirement. For example, the second harmonic on a 2 meters transmission is over 158 microwatts.
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