Products > Test Equipment
Breaking Input Stage of Spectrum Analyser with Radio TX
xrunner:
--- Quote from: CatalinaWOW on November 27, 2023, 04:22:50 pm ---The first attenuator in the string does not dissipate 100W.
--- End quote ---
I stated it has to be rated to accept 100W of power - to withstand 100W of power - to not destroy itself upon accepting an input of 100W. That's what the rating is for.
joeqsmith:
--- Quote from: xrunner on November 27, 2023, 04:57:16 pm ---
--- Quote from: CatalinaWOW on November 27, 2023, 04:22:50 pm ---The first attenuator in the string does not dissipate 100W.
--- End quote ---
I stated it has to be rated to accept 100W of power - to withstand 100W of power - to not destroy itself upon accepting an input of 100W. That's what the rating is for.
--- End quote ---
He's just pointing out for your 100W example that the first 10dB attenuator drops the signal from 50dB to 40dB as you pointed out, meaning it dissipates 90W. This is all it needs to be rated for. That or I missed it.
xrunner:
--- Quote from: joeqsmith on November 28, 2023, 04:34:19 am ---He's just pointing out for your 100W example that the first 10dB attenuator drops the signal from 50dB to 40dB as you pointed out, meaning it dissipates 90W. This is all it needs to be rated for. That or I missed it.
--- End quote ---
You missed it, but I don't understand why or how, or if you are just wanting to spend more time on the forum. Maybe you are teasing me? I know you know all this, perhaps you are testing me? Ah that's it.
Just research what the power rating of an attenuator is. It isn't how much it dissipates when X watts is applied at the INPUT. It's how much power it is rated for at the INPUT - the Max INPUT power. The power rating of an attenuator is the Max INPUT power it can take. How many other ways can I form the same statement?
I mean, there are thousands of documents and tutorials out there, or just look at any manufacturer's data sheet, as I've gone to the trouble of attached below. Look at the power specification. It's for a 10 dB, 100 W part. It can take no more than 100 W INPUT. The same thing would be true for a 100 W, 3 dB att. It's rated for Max input power. That's how all of them are done.
So no, if you start out with 100 W and want to drop the power with an attenuator, the first one in series (or only one) must be rated for 100W, no matter how much the dB att. is. There's really no more to say about it.
joeqsmith:
--- Quote from: xrunner on November 28, 2023, 12:14:12 pm ---Just research what the power rating of an attenuator is. It isn't how much it dissipates when X watts is applied at the INPUT. It's how much power it is rated for at the INPUT - the Max INPUT power. The power rating of an attenuator is the Max INPUT power it can take. How many other ways can I form the same statement?
--- End quote ---
So not a function of the dissipated power but instead the breakdown voltage?
https://birdrf.zendesk.com/hc/en-us/articles/360041312394-Can-you-use-two-25W-attenuators-in-series-for-a-50W-input-signal-
--- Quote ---Bird FAQs Attenuators
Can you use two 25W attenuators in series for a 50W input signal?
Unfortunately no. The first attenuator in the series needs to be rated for the 50W input power. Otherwise the attenuator will be damaged. Depending on the attenuation value of the first, the second attenuator can have a rating of less than 50W.
For example, if you have a 50W signal and need a total reduction of 6 dB, you can use a 50W 3dB attenuator at the input and then a 25W 3dB attenuator after to the 50W attenuator.
--- End quote ---
***
Now I figured you would call me out for calling out your post on using un-terminated attenuators for a load.
xrunner:
--- Quote from: joeqsmith on November 28, 2023, 12:23:44 pm ---
So not a function of the dissipated power but instead the breakdown voltage?
https://birdrf.zendesk.com/hc/en-us/articles/360041312394-Can-you-use-two-25W-attenuators-in-series-for-a-50W-input-signal-
--- End quote ---
Say we have a 100 W signal, and we want to drop it by 10 dB, so we have a 10 W output. OK then 90 W will be dissipated. But think about it. How does the power dissipation work inside the attenuator? Does it just happen at a single point inside, or does it happen in a gradual fashion, taking into account what resistive elements are inside?
It doesn't simply happen at a point, so if 100 W goes into the input connector, what happens? The first element is going to see 100 W. So it must be able to handle 100 W (yes it's a certain voltage of course) at the input.
It doesn't matter whether it's a 1 dB attenuator or a 40 dB attenuator, it has to be rated for 100 W at the input if that is the Max input power. If the Max input power is less, buy a lower rated att.
--- Quote ---Now I figured you would call me out for calling out your post on using un-terminated attenuators for a load.
--- End quote ---
Oh yea I know what's going on. ;D
I've been on this forum for a long time and I know when to move along ... :-DD
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