Are these spurious emissions from my HT?

[jonnycat5000]

I bought a CCR (Quansheng UV-K5(8)) last year and am finally getting around to using it. Entered in the local Simplex frequency and when I keyed the mic this is what I saw from my RTL-SDR in GQRX. Thinking I might have gotten a dud, I recently purchased a UV-K1, with a very similar result. Note: none of spikes were there before I keyed up, and the waterfall was quiet.

Is this normal for these cheap radios, did I end up with two duds, or is this some type of issue with the SDR dongle (I've never come across such a picture when receiving with the SDR before)?

 

[AK9R]

The spurious emissions that CCRs are (in)famous for appear at multiples of the fundamental (carrier) frequency. If transmitting on 146.5 MHz, you'll see spikes at 293, 440, 586, etc.

 

[EAFrizzle]

Looks like the SDR might be overloaded. Have you tried it with the antenna disconnected or some attenuators?

 

[K4EET]

I bought a CCR (Quansheng UV-K5(8)) last year and am finally getting around to using it. Entered in the local Simplex frequency and when I keyed the mic this is what I saw from my RTL-SDR in GQRX. Thinking I might have gotten a dud, I recently purchased a UV-K1, with a very similar result. Note: none of spikes were there before I keyed up, and the waterfall was quiet.

Is this normal for these cheap radios, did I end up with two duds, or is this some type of issue with the SDR dongle (I've never come across such a picture when receiving with the SDR before)?

View attachment 202003

What you are seeing there is probably a result of overloading the RTL-SDR. As @AK9R mentioned above where harmonics fall, look at YOUR transmit frequency that you are using for the harmonics. You will also need a LOT of attenuation between the two antennas. It would be best to directly connect the equipment under test with the correct attenuator(s) to get a signal around -95 dBm. If you cannot do a proper test setup, at least use a dummy load for the HT. For the harmonics that you see then, and there will be harmonics, make sure they are less than what is permitted under Part 97 of the rules.

<edit> The -95 dBm level may be too low for this measurement now that I think about it. The harmonics should be over 30 dB below the fundamental signal. You probably would need a -45 dBm signal to see the harmonics.

 

[kayn1n32008]

The spurious emissions that CCRs are (in)famous for appear at multiples of the fundamental (carrier) frequency. If transmitting on 146.5 MHz, you'll see spikes at 293, 440, 586, etc.

No, Not just harmonics, they outputted garbage all over the spectrum.

 

[jonnycat5000]

The spurious emissions that CCRs are (in)famous for appear at multiples of the fundamental (carrier) frequency. If transmitting on 146.5 MHz, you'll see spikes at 293, 440, 586, etc.

Thanks for that, I have seen those on the spectrum analyzers but I wasn't sure if mine were the same.

Looks like the SDR might be overloaded. Have you tried it with the antenna disconnected or some attenuators?

You mean the SDR antenna or the HT antenna? Assuming you mean an attenuator on the HT?

 

[jonnycat5000]

What you are seeing there is probably a result of overloading the RTL-SDR. As @AK9R mentioned above where harmonics fall, look at YOUR transmit frequency that you are using for the harmonics. You will also need a LOT of attenuation between the two antennas. It would be best to directly connect the equipment under test with the correct attenuator(s) to get a signal around -95 dBm. If you cannot do a proper test setup, at least use a dummy load for the HT. For the harmonics that you see then, and there will be harmonics, make sure they are less than what is permitted under Part 97 of the rules.

Thanks, I don't have a signal analyzer, I'm just trying to figure out if I am really putting this much noise into the air.

 

[techman210]

In lab work we notch down the primary frequency over 40db so we can accurately measure the power of any spurs and harmonics. Otherwise as others have pointed out- you can overload the spectrum analyzer and cause internal mixes that give you false data.

 

[jonnycat5000]

In lab work we notch down the primary frequency over 40db so we can accurately measure the power of any spurs and harmonics. Otherwise as others have pointed out- you can overload the spectrum analyzer and cause internal mixes that give you false data.

Thanks, I should have mentioned in my original post that I'm not connecting the radio to the SDR; the radio has the stock short antenna and the SDR has a 1/4λ ground plane up in the attic. The waterfall image was obtained at full power of the HT (~5W) and about 30 feet linear distance from the antenna.

 

[EAFrizzle]

Thanks, I should have mentioned in my original post that I'm not connecting the radio to the SDR; the radio has the stock short antenna and the SDR has a 1/4λ ground plane up in the attic. The waterfall image was obtained at full power of the HT (~5W) and about 30 feet linear distance from the antenna.

The SDR is overloaded. Put a dummy load on the HT or remove the antenna on the SDR. A set of attenuators is a great addition to any radio setup, and will help on the receiver.

Most new HTs are very tolerant of transmitting into large mismatches, so turning the Tx power to low and just removing the antenna can help.

I keep a couple of sets of these Nooelec attenuators around for my NanoVNA, TinySA, and LNAs going to the SDRs. When I use the TinySA and an HT, I put -6 to -10 dB on each with no antennas. Not the best method, but I don't have to worry about toasting the TinySA.

 

[jonnycat5000]

The SDR is overloaded. Put a dummy load on the HT or remove the antenna on the SDR. A set of attenuators is a great addition to any radio setup, and will help on the receiver.

Most new HTs are very tolerant of transmitting into large mismatches, so turning the Tx power to low and just removing the antenna can help.

I keep a couple of sets of these Nooelec attenuators around for my NanoVNA, TinySA, and LNAs going to the SDRs. When I use the TinySA and an HT, I put -6 to -10 dB on each with no antennas. Not the best method, but I don't have to worry about toasting the TinySA.

Thank you, I adapted a 50Ω BNC terminator on the radio and the waterfall only showed the transmission frequency, with none of the spike present. I also tuned the second radio to the frequency of the largest spike, and received no signal at the spike frequency when transmitting the other radio at full power.

Thanks everyone for all of the help, I'm marking this one as solved.