On the TinySA's. "This one is a little bit more expensive..." Yeah, a little bit! 😂 Good video. I've been thinking about picking up one of these units.
Keep in mind that while the Tiny SAs are very good and well worth buying, they are not really a lab quality instrument. They're great for comparative and illustrative purposes but aren't always reliable for absolute measurements. I see quite a bit of variation between the Tiny SA and my Siglent instrument.
Interesting video. I have the TinySA Ultra and just love it. But, for you....jumper cables ! WOW, way too much of a load on those SMA connectors. The TinySA comes with cables, you should use them. Barry, KU3X
What if you just hooked a rubber duck to the tiny SA and a dummy load to the radio and use them in the same room? Would it still overpower the tiny SA?
Hayden, Thanks for the video. One thing I've always struggled with is dB's, I just can't get my head around them! Am I just thick or something? I've never really found a decent explanation as to how dB relates to power gain or loss in a real-world situation, the mathematics just make my eyes glaze over.
Good meaty stuff. :bow: Now at first blush I would have assumed you had a nice shielded connection between the radio and the TinySA yet you still picked up the transmission from another radio in the shack (it did seem to be rather weak). Any idea how that signal snuck in? Just goes to show you - testing can be hard!
-16.02 dBm is 25uw (microwatts) and is mentioned in the fcc regulations about reducing between 25uw and 10uw. So that needs to be equated within the maths for determining attenuation. Cheers
Good video. I think you could make the wrong assumption regarding cheap Chinese radios. The FCC(or other gov entities) have requirements on spurious transmissions, but these tests should be performed with the stock radio which includes the stock antenna. Antennas are like band pass filters and if they are any good will transmit the band signal but not necessary out of band spurious harmonics. I say your testing is wrong. Use the SA antenna, recalibrate the attenuation to normalize the main frequency signal to 37dBm(5W) and then test radios. If the radio does not transmit spurious harmonics via the antenna then it's legal. I may turn out that cheap radios with muhltiband antennas fail and if so then they are illegal. I would say that even a really, really bad radio could transmit legally into a dummy load. It just won't be ant fun.
@@johnsonstechworld You will not regret getting a decent nanoVNA, there is so much you can do with it. Just be aware of the cheap copies and you'll be fine.
I use a nanovna to test the attenuator's actual attenuation. Since they won't be exactly 20 or 40db. It would be a good experiment to go to a high up location and attempt to pickup actual 2nd harmonics transmissions of hams using a popular repeater. Using an sdr receiver and an antenna tuned to 288Mhz-296Mhz. From my qth I've not seen anything, but its milliwatts line of sight and I'm not at a high elevation.
The attenuation won’t be completely flat over its entire range, although my amphenol attenuators are only +/- 0.5dB within spec over the entire DC-3 GHz range.
Awesome, super helpful! Exactly what I needed as I wanted to test all my HT's. The calculations also helped as I didn't know how to figure all that out, too.👍🤠
Great content and very helpful for someone interested in the hobby. I realize this is a very basic question and more related to test and measurement practice than this measurement in particular, but would it be possible to precisely measure the calibration of the attenuator chain first / why would that be more difficult than it’s worth etc. Perhaps it’s neccessary to just have much higher end test equipment to get that accuracy etc?
I do have a HP service monitor that I've measured those attenuators in the video. They are within +/- 0.5dB of accuracy... even better for the big one with the heatsink... I think I measured it on 146 MHz at 20.13dB. But yes - good point, you can get some cheap attenuators that might be rubbish and not the correct spec.
Hayden, I noticed the 50w attenuator has Type N connectors. How much would using UHF connectors affect the measurements, especially on the 2nd and 3rd harmonics? Or even if the fundamental was 70cm?
Interesting question - I wouldn’t use PL-259/SO239 connectors at UHF frequencies in this kind of testing - due to the inconsistent impedance above 100 MHz.. which they are commonly rated for - even though “up to 300 MHz” is also quoted. At 2m I wouldn’t expected to see any major issues…
@HamRadioDX Thanks for the reminder to use N type connectors for UHF frequencies. That (along with the need for the proper attenuation) should get a bit more air time from some other Hamtubers.
These Walkie talkies are low powered signals under 5 watts, so if the IMD is not too good the the damage caused by the transmitter will be minimal. These walkie talkies are intended for the amateur radio market and as long as those signals stay within the amateur radio bands you be ok , you want be hunted down. LOL Serious problem only occur when you running high powered amps and transceivers with crappy IMD specs. The minimal specs by the FCC for manufactured transceivers, transmitters, and amplifiers is -50 db below the fundamental frequency. If this was really enforced 95% of all the Chinese, and a lot of Icom , kenwood, yaesu equipment would not be imported. Now commercial equipment the FCC is tight on customs cause this is where the money is.
