Spurious emissions

[KD7MW]

I've measured all my VHF/UHF radios with a TinySA. There was a learning curve, because if you feed the TinySA more than -30dBm, it can generate internal spurs, which can make things look worse than they really are. If we assume 40 dB below carrier level is compliant, my "Big Three" Japanese radios are all compliant. So is my Radioditty GD-77.

My TYT MD-9600 radio (hardware version 1) is fine on 70cm. But it is not compliant on 2m. So if I use it on 2m, I connect it to my antenna through a DCI bandpass filter.

For background, the ARRL handheld radio tests in January 2020 QST say that we need 53 dB of suppression for a 5 watt radio, to comply with the 25 microwatt absolute limit for a >25w radio at 144 MHz. That drops to 49 dB at 2 watts and 46 dB at 1 watt. This is more stringent than -40dBc. Then again, their test equipment is better and more expensive than most of us have. ARRL testing at hamfests between 2017-2019 showed all Big Three radios tested (plus Alincos) were compliant, but many Baofeng and Wouxin radios were not.

Dual band or wide-range radios have a much harder time suppressing all harmonics than single band radios. Especially at the 3rd harmonic of 2m, which is in or near the 70cm band. Considering what Colin has mentioned above about leakage around switched filters, that's not surprising.

[SA0BUX]

RT3S seems ok,

RT3S 5W 144MHz -70db ext. attn.

RT3S_5W_144MHz.png (5.59 KiB) Viewed 1730 times

RT3S 5W 432MHz -70db ext. attn.

RT3S_5W_432MHz.png (6 KiB) Viewed 1730 times

[SA0BUX]

But Baofeng DM-1701 seems to have similar problems on VHF as MD-9600

Baofeng DM-1701 5W 144MHz -70db ext. attn.

DM1701_5W_144MHz.png (7.82 KiB) Viewed 1729 times

Baofeng DM-1701 5W 432MHz -70db ext. attn.

DM1701_5W_432MHz.png (6.72 KiB) Viewed 1729 times