Baofeng radios not legal for use in US (probably)

[wandrson]

So I was surprised when an associate informed me that by Baofeng HT was not FCC compliant. I told him I didn’t believe him so he sent me the following link

I decided to test the performance of my GT-5 and obtained the following results, which seem to confirm the information in the above video. The first harmonic is 65 dB down, but the second is only 38 dB down.

Here is the relevant section of Part 97.307 Emmission Standards

[quote]
(e) The mean power of any spurious emission from a station
transmitter or external RF power amplifier transmitting on a frequency
between 30-225 MHz must be at least 60 dB below the mean power of the
fundamental. **For a transmitter having a mean power of 25 W or less, the **
mean power of any spurious emission supplied to the antenna transmission
** line must not exceed 25 µW and must be at least 40 dB below the mean **
**power of the fundamental emission, but need not be reduced below the **
power of 10 µW. A transmitter built before April 15, 1977, or first
marketed before January 1, 1978, is exempt from this requirement.[/quote]

So it turns out that those cheap chinese radios may not be worth even the little we pay for them

[zmetzing]

So it turns out that those cheap chinese radios may not be worth even the little we pay for them

Might open them up and see if you can add a low-pass before the diplexer. Shouldn’t be hard, and, as licensed Amateurs, we can build/fix our own equipment.

[edit: Nice testing, Walter! Make sure to limit the input power to the SA with an attenuator, so as to not cause IMD in the SAs own front-end.]

Aside: Enjoy that slave Chinese labor while you can. Just like thermodynamics, the system will eventually equalize, and then corporate America will find some other country to exploit.

[wandrson]

[edit: Nice testing, Walter! Make sure to limit the input power to the SA with an attenuator, so as to not cause IMD in the SAs own front-end.]

Yeh, I built an RF sampler that uses a FT-43-68 toroid with a 10:1 turns ratio to sample the RF.This seems to work fine for the 5W or so I have used it (-20db), but will likely build another for testing 100W transmitters.

I have always loved Chinese slave labor. We would not have the toys we do without it. Want to chat with you about DIY impedance bridges sometime.

The Baofeng works acceptibly on 70cm, so it can be use up there, but as built not for 2M.

[wandrson]

So as a point of comparison I performed the same test with my Kenwood TH-D72

[TBJK]

So for the non-radio savvy people, does this mean it may get bleed over from excessive DB or?

[wandrson]

Yeh, I built an RF sampler that uses a FT-43-68 toroid with a 10:1 turns ratio to sample the RF.

[wandrson]

So for the non-radio savvy people, does this mean it may get bleed over from excessive DB or?

Yeh, that is basically what it means. A transmitter may not have any transmission outside of its primary intended frequency that isn’t at least 1/10000 (-40 dB) of the power or less (for VHF 30-300Mhz). Transmitters tend to produce these unintended signals at multiples of the transmitting frequency.

The -38.52 dB on the second harmonic that I measured for the Baofeng indicates that it is only 1/7110 of the power of the primary (5W) so it is still ~70uW or about seven times the allowed power. Even at the lowest power setting for the Baofeng (1), it would still be 14uW or about 4 uW over the limit.

What this means is that if you will keep using your Chinese HT you should not use anything but the lowest power setting on 2M. Which is fine since that will work to get to most of the repeaters you would be using.

Frankly, I am surprised that the FCC hasn’t banned the import of these radios since they are clearly out of compliance, and that fact is apparently well known and has been for a while.

[tmc4242]

Looks like a good starting point for the mod in question:

http://remco.org/baofeng/1.html

I have not tried it. YMMV.

Todd

[zmetzing]

Looks like that’ll work. Nothing magic about fixing this problem, just sloppy engineering to begin with.

[kbraby]

Doesn’t look like it quite lines up, but wondering if the craptastic antenna that ships with them is so poor at 280Mhz, that the combined system is legal on actual emissions, until you replace it with a better antenna.

[wandrson]

So, I took apart one of my Baofengs, and the mod described above looks like it would be a PIA… So I started thinking about adding an external low pass filter in a small 0.5" diameter 1" long package.

So far I have come up with this

A simple 3 pole butterworth. Not sure if it will be enough, but plan on testing soon…