This will be my first post on blogger.com. I've posted on various forums in the past, but I think a consolidated location to post various findings would be helpful, at least for me to go back and reference. Additionally, if new data is found, it would be a convenient place to add an addendum.
Spectral Purity of various Ham Radio Transmitters
I thought I'd post some findings related to the spectral output of several models of Amateur Radio equipment. What spawned this was I happened to run across some articles about people using Baofeng UV-5R HTs for portable repeater use (basically putting them in an ammo box). A similar site referenced a related article in QST about the Baofengs dirty transmitters (at least on some of the DUTs).
So this encouraged me to put some transmitters on the bench and test with a Spectrum Analyzer to see which ones have a 'measurable' amount of dirt / harmonics transmitted. Some notes on the test and the attached pictures:
1. I used a 30dB ISO tee to sample the output with an additional 10dB attenuator (total 40dB attenuation) to get well below my safe max input of 20dBm. 50Ohm dummy load was obviously used to terminate the ISO-tee through connection.
2. All HT's were set at the high setting. On the other hand the Yeasu FT-8900R was set at MID2 which is 10watts.
3. I was not intending to do FCC Part §97.307 compliance testing; The intent was just to check for 'grass' (spurious output) and see a side-by-side comparison with the same test setup. The findings seemed to be inline with what others have seen.
4. Spectrum Analyzer was set to full Span.
The following radios were tested at both 140Mhz and at 440Mhz:
- Baofeng UV-5R
- Baofeng UV-82C (Supposed to be Part 90 compliant)
- Baofeng BF-F8HP
- Wouxun KG-UV8D
- Wouxun KG-UV9D
- Yaesu FT-8900R
Here are the screen shots of Spectrum Analyzer for each model.
UV-5R @ 140Mhz
UV-5R @ 440Mhz
Baofeng UV-82C @ 140Mhz
Baofeng UV-82C @ 440Mhz
Baofeng BF-F8HP @ 140Mhz
Baofeng BF-F8HP @ 440Mhz
Wouxun KG-UV8D @ 140Mhz
Wouxun KG-UV8D @ 440Mhz
Wouxun KG-UV9D @ 140Mhz
Wouxun KG-UV9D @ 440Mhz
Yaesu FT-8900R @ 140Mhz
Yaesu FT-8900R @ 440Mhz
Summary:
The Yaesu was clean on both 2m and 70cm band. Any noise was close to the noise floor. Additionally,
both Wouxun's DUTs were clean.
But the Baofeng did produce some spurious
emissions that were 'measurable'. Worse on 2m than 70cm. The UV-82c was the cleanest on 70cm of all the Baofeng models tested.
The output does show which radios have spurious transmissions and which ones do not.
