What kind of scope do I need for an 11 meter radio? I was looking at a 100 mhz oscilloscope. Would that be enough to check rf power or would the 10x rule come into affect? What kind of probes? Thanks for any help...
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Oscilloscope for cb radio?
- Thread starter 805 california
- Start date
One does not necessarily use a scope to measure RF power as much as testing and checking wave form/shape in order to maintain its symmetry. Yes, an analog 100mhz scope will do just fine . . .
100MHz is more than enough for CB. Like Robb said above you do not normally measure POWER with a 'scope as it simply measures voltage and you then need to apply some math to determine the power out into a known load resistance. Also what is the x10 rule? Never heard of it and been using 'scopes for about 35 years on and off.
To align your transmitter it says to hook up to scope and adjust for best forward swing on scope and I'm wondering if that would over load a 100 mhz scope? I found this on cbtricks. "oscilloscope is basically a voltmeter that can also give you information on the shape and quality of a signal (aka waveform). It's probably the best all-around tool for measuring the quality and amplitude (power) of a CB transmitter's output signal. To use a scope for that purpose use a 10X probe so you don't load down the circuit". I'm looking to buy a tektronic 465. Thanks for the help.
I think what they were trying to say is to get the best forward swing that has an undistorted waveform.
When testing for best forward swing, one would need to use an accurate wattmeter, a decent quality dummy load, and RF pickup box to distribute signals for test gear, a 1000hz audio feed to the mic, and a scope to be sure that the waveform shows no negative or positive peak distortion - which can only be seen on a scope . . .
When testing for best forward swing, one would need to use an accurate wattmeter, a decent quality dummy load, and RF pickup box to distribute signals for test gear, a 1000hz audio feed to the mic, and a scope to be sure that the waveform shows no negative or positive peak distortion - which can only be seen on a scope . . .
So do you think i would over load a 100 mhz scope with a little am modulation? And could I use say a 300 probe with a 100 mhz scope?
I use a 30mhz scope to monitor modulation and do receiver alignments on CB radios. It does everything I need and I can see when a junk amplifier is oscilating. Found it on epay for under $50 shipped. Super glued a broken knob and and it was good enough for me.
I use a bnc connector to mount an RF pickup inside amplifiers, watt meters or whatever I have inline. It makes for one less jumper but you can build a pickup in a small project box.
Some guys wrap a dozen wraps of small gauge wire around their coax for a pick up. It does work but the waveform on the scope didn't look as clean for me.
As for the RX alignment all I use is an 8 ohm ceramic resistor and a bnc connector. For the simple tasks I do I haven't needed to buy any probes.
I use a bnc connector to mount an RF pickup inside amplifiers, watt meters or whatever I have inline. It makes for one less jumper but you can build a pickup in a small project box.
Some guys wrap a dozen wraps of small gauge wire around their coax for a pick up. It does work but the waveform on the scope didn't look as clean for me.
As for the RX alignment all I use is an 8 ohm ceramic resistor and a bnc connector. For the simple tasks I do I haven't needed to buy any probes.
Can't really go wrong with a Tektronix 465, got one sitting on my bench.
Also have a Gould 20 MHz scope used as a monitor for my 80m AM transmitter and a 50 MHz Kikusui 5650 that I am still trying to decide what to do with.I was just confused by what this x10 rule was you mentioned but now I see it was simply referring to the use of a x10 probe. Regardless of what CB Tricks says a scope is not ideal for measuring power out, in fact it is rather poor at doing that since you need to convert peak-to-peak voltage to RMS voltage and then use that result to calculate actual power after having determined the exact impedance of the RF load. Stick to a meter for power measurements. A scope is however, great for adjusting circuits for the proper output levels since a proper alignment will specify what RF voltage should be see on the scope as well as seeing how pure that waveform is. Also the bandwidth of a scope (100 MHz in this case) simply refers to the maximum frequency it can be used at before the accuracy begins to drop off and has nothing to do with how much RF voltage can be applied to it before overloading the input circuits. When measuring anything with a high level you should always measure a sample of that signal rather than simply tapping onto the high level signal itself. A x10 probe is useful for this however a sample is the best way to go
Can't really go wrong with a Tektronix 465, got one sitting on my bench.
Thank you and everybody for their input. It's all starting to make sense now. I'm just trying to learn as i go with my new past time activity being radios. Worldwidedx has been an excellent resource. Thanks!Can't really go wrong with a Tektronix 465, got one sitting on my bench.
Don't confuse frequency with power/voltage. 100 MHz is the bandwidth; CBs operate around 27 MHz.
So I bought a tektronix 465b what else do I need to hook up the cb radio to see the signal? And how do I hook up a cb radio to a scope. Thanks
The best place to start is the manual. You DID get the manual with it didn't you?
I got the 200+ plus page service manual online. I'm just wondering what kind of bnc connectors I need. I just got the scope nothing else. I just need to be pointed in the right direction. I'm starting to think you need a degree to fully understand how a scope works.