Very nice presentation and simplification of the resistive taps Stuart. Two points: on the chart dBm is written with just the B capitalized. And at 8:54 the proper terminology is: 50 dBm take away 40 dBm is 10 dB. (Because dB is a power comparison and dBm are absolute power values). Keep instructing and 73 Peter
i'm going to build your 40dBm attenuator project, but I have a doubt. In the calculation, I even carried out one by one, it didn't work, but later on, you explained that the impedance you were using was not 50 ohms but 25 ohms, so the calculation worked, as you were counting on the input Z of the power analyzer. spectrum..my question is: I want to connect it to my Rigol scope, whose Z= 1mega ohms. Using the n formula with r1= 2460 and r2 =50 ohms, the attenuation is 34 dBM. It's OK? I can use it to see the modulation and the RF power.??
Hello Antonio, What a great question! Here is the thing, If you do not have a 50ohm load on the end of the connection to the test device then your SWR will be way off. That could damage your radio so we need that 50ohms there! The solution is to have an inline 50ohm terminator at the input connection to the scope. Since your scope is high impedance it should not change the overall impedance value seen by the radio. I built my own terminators for my Rigol scope to hook it up to my HF rig. I used this box: www.amazon.com/gp/product/B010DHQLEI/ mounting 2 BNC panel mounts (one male one female) and used 2 100ohm 1W resistors in parallel to place the 50ohms next to the Rigol. You can buy a Chinese 1W device here: www.amazon.com/gp/product/B08V1MX6HD/ if you wanted to save the build time. I wanted the extra watt of protection so I built one. Hope that answers your question! Stu AG6AG
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This video great. It is exactly what I was looking for building a tap for my tinySA.
Great video Stuart. This gives lots of ideas....
Glad to hear it!
Very nice presentation and simplification of the resistive taps Stuart. Two points: on the chart dBm is written with just the B capitalized. And at 8:54 the proper terminology is: 50 dBm take away 40 dBm is 10 dB. (Because dB is a power comparison and dBm are absolute power values). Keep instructing and 73 Peter
Thanks VE6KK, I always seem to screw those up...
Stu
AG6AG
thanks!
No problem!
i'm going to build your 40dBm attenuator project, but I have a doubt. In the calculation, I even carried out one by one, it didn't work, but later on, you explained that the impedance you were using was not 50 ohms but 25 ohms, so the calculation worked, as you were counting on the input Z of the power analyzer. spectrum..my question is: I want to connect it to my Rigol scope, whose Z= 1mega ohms. Using the n formula with r1= 2460 and r2 =50 ohms, the attenuation is 34 dBM. It's OK? I can use it to see the modulation and the RF power.??
Hello Antonio,
What a great question! Here is the thing, If you do not have a 50ohm load on the end of the connection to the test device then your SWR will be way off. That could damage your radio so we need that 50ohms there!
The solution is to have an inline 50ohm terminator at the input connection to the scope. Since your scope is high impedance it should not change the overall impedance value seen by the radio.
I built my own terminators for my Rigol scope to hook it up to my HF rig. I used this box:
www.amazon.com/gp/product/B010DHQLEI/
mounting 2 BNC panel mounts (one male one female) and used 2 100ohm 1W resistors in parallel to place the 50ohms next to the Rigol. You can buy a Chinese 1W device here:
www.amazon.com/gp/product/B08V1MX6HD/
if you wanted to save the build time. I wanted the extra watt of protection so I built one.
Hope that answers your question!
Stu
AG6AG