BaoFeng HTs and Spurious Emissons

The January edition of QST has some disturbing data about dirty transmitters in BaoFeng HTs.

Amateurs are responsible for their transmitters being clean, but most of us don’t have the test equipment to check that. Also, manufacturers must meet the FCC regulations for every transmitter sold.

The ARRL Lab set up at hamfests and tested the HTs that hams had with them. Over four years, only 5% to 9% of BaoFeng HTs passed the test. Alinco, Icom, Kenwood, and Yaesu had 100% pass rates. Wouxon improved from 83% to 100% over the years.

QST 2020 01 HT Testing

From “Technical Correspondence”, QST, January 2020, pages 60-62. This chart is on page 61. QST is available online to ARRL members. This is a link to the article online.

The FCC rules for spurious emissions are in 47 CFR ยง 97.307 – Emission standards.

What if you already own a BaoFeng, like me?

Run low power. This will reduce the amount of power in the spurious emissions. Reducing the power from 5 W to 0.5 W should reduce the spurious emissions by 10 dB. The spurs still won’t be 40 dB below the carrier, but they will be lower in terms of absolute power. It can’t hurt. It will make your battery last longer, too.

What if you want an inexpensive HT?

Instead of a $50 BaoFeng, save up a bit more for a $75 Yaesu FT-4XR. From my research, this is the only HT under $100 from a major radioo vendor.

The FT-4XR uses the same chipset as the BaoFeng, so it has roughly the same feature set. But it has a clean transmitter and better interference rejection in the receiver. It also has ham-specific firmware, like automatic repeater offsets. That should make it easier to use.

The FT-4XR also uses the same antenna connector as BaoFeng, so aftermarket Nagoya antennas might fit. I would probably try the Nagoya NA-771 for $17, which might fit. I’ve heard recommendations for the Diamond SRJ77CA ($27).

I linked to DX Engineering’s page above, but the FT-4XR is available at similar prices from Ham Radio Outlet, Gigaparts, and other ham stores. Amazon has it at a higher price ($83), oddly.

BaoFeng UV 5R Yaesu FT 4XE

How did this happen?

It appears that the BaoFeng radios were designed for the much more lenient Part 90 emission regulations and do not meet the amateur radio regulations.

An article by AD5GG compares BaoFeng UV-5R emissions to Part 90 (private land mobile) and Part 97 (amateur) regulations. The BaoFeng meets the weaker Part 90 limits, where spurious emissions are not to exceed -20 dBc (dBc is relative to carrier). Part 97 limits spurious emissions to -40 dBc, 100X lower than the Part 90 limit.

Designing for the Part 97 limits requires additional low-pass filtering on the output. The new parts may only be pennies, but it would require a new board design. Maybe new versions of the BaoFeng HTs will be designed to the stricter standards, but I’ll have to see proof of that. The UV-5R is up to the third generation, at least, and still not compliant.

Plastic Pipe Roof Antenna Support

I noticed a clever antenna mount on another ham’s roof, so I built one myself. Putting my VHF/UHF antenna at the highest point of the roof has really improved my ability to copy some of the far-flung participants in our weekly ARES/RACES net.

plastic pipe antenna mount close-up

A cradle built from two-inch ABS DWV (drain, waste, and vent) pipe sits across the ridge of the roof. Legs two feet long go down on each side and a two-foot section is a vertical antenna mast.

My antenna is a Diamond X50NA, same as the X50A, but with a weatherproof Type N connector. I did additional weatherproofing with 3M Temflex 2155 rubber splicing tape and Scotch Super 33+ electrical tape.

I had spotted an antenna mounted like this and contacted the ham at that address. Rolf Klibo, N6NFI, replied with an article he’d written for the SPARK newsletter describing the mount. With that, I was off to the hardware store.

I used two-inch ABS DWV (drain, waste, and vent) pipe in two-foot sections. I cut up two of them to make the four pipe sections that go along the ridge of the roof.

The X50NA mounting hardware fits masts up to 2 3/8 inch, which is why I used two inch pipe. For coax strain relief, I used a conduit hanger that fit. Zip ties attach a loop of coax to the hanger so the full weight of the feed line isn’t pulling on the connector. That can rip the coax right out of the connector, or harder to diagnose, pull just one of the shield or center connector loose.

Antenna mount 3 Antenna mount 4

For a commercial version, I’d look at the Rohn NPPK, a steel frame that fits over the roof peak. It is designed to have a rubber mat underneath and four 18 pound concrete blocks holding it down. I’m sure it is far more secure than my DIY plastic pipe mount.

Using a Mobile Antenna as a Temporary Base Antenna

For our July Fourth Safety Watch this year, I used my dual-band mobile antenna on a ground plane mount on a camera tripod. I’d purchased a Nagoya GPK-01 NMO Ground Plane Kit ($28) to test my NMO mobile antenna, because my mag mount seemed flaky.

As I was drifting off to sleep one night, I thought that the 1/4-20 screw on my camera tripod might fit the holes on the ground plane kit. It did, so now I have a robust, free-standing, dual-band antenna for em-comm use.

IMG 4753

The antenna is a Comet SBB-5NMO with 3 dB of gain on 2 m. Not a flamethrower, but a solid antenna when used with a good ground plane.

The radials unscrew from the mount, so the ground plane kit packs up small.

IMG 4750

Our station was up on a hill, so we had great line of sight to the whole valley. We ran a mobile rig (Yaesu FT-8900R) at 50 W from a battery, so we had a great signal. We could also hear the other stations clearly, so our station was net control.

IMG 4748

The only thing I’ll change next time is to use 1/4-20 wingnuts instead of regular nuts. I might paint them orange, too. I was sure that I would drop a nut in the grass and never find it.

And yes, that is a classic Gitzo Reporter aluminum tripod. If needed, I could extend the center column to get the radials above eye level.