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Re: Attenuators

Bruce Hawkins
 

Mini circuits isn't random amazon or eBay bought attenuators.??

In my past employment, engineers were blowing up attentiors and input to spectrum analyzers etc.? This is my experience.

While I hear your points. I should have anticipated possible criticisms...

I still stand. I don't recommend applying the unit under test (a transmitters), output power, to attenuators rated for the same power level. Regardless to the manufacturer of the attenuators. Although, professional brands, will more likely tolerate that better.

Best regards, Bruce Hawkins - AC6DN.? Sent from my Android phone.? And from: ac6dn@...

On Jun 15, 2024 3:46 AM, G8HUL <g8hul@...> wrote:

That is certainly not the way most manufacturers, including Mini Circuits, specify their attenuators. A 100W attenuator will be spec'd at 100W CW max input power , usually at 25 degrees C with a de-rating as the temp goes up. There will also be a peak pulse rating, with sometimes? a de-rating curve for power with time.

73
Jeff G8HUL


-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of W0LEV
Sent: 14 June 2024 22:12
To: [email protected]
Cc: Wiggle Pig <wigglepig@...>
Subject: Re: [tinysa] Attenuators

This has been pointed out previously by another ham.? If one starts with 100-watts from the transmitter in CW, RTTY, or the digital modes, what is dissipated in a 3 dB attenuator?? NOT the full 100-watts.? The 3-dB attenuator "eats" 50-watts and PASSES along 50-watts at its output.? Therefore, it dissipates 50-watts.? If properly spec'ed, that should be for "key down" conditions for a very long time.? Another 3 dB attenuator would "eat" 25-watts and pass along 25-watts.? It should dissipate 25-watts for a very long time.?


Take the statement from the previous post:? (QUOTE):? If the radios output is 100w.? Then absolute minimum wattage is 100 Watts.


This statement is just not true.? If you needed to dissipate ALL of your 100-watt power, that would require a dummy load, and NOT an attenuator.? And, then, yes, it would need to be a 100-watt DUMMY LOAD with NOTHING out the "other end" as there is no "other end" with a dummy load.



Dave - W?LEV


On Fri, Jun 14, 2024 at 6:05?PM Bruce Hawkins via groups.io <http://groups.io>? <ac6dn@... <mailto:[email protected]> > wrote:


I suggest the opposite...

If the radios output is 100w.? Then absolute minimum wattage is 100 Watts.? That's ok if you don't transmit longer than few seconds.? Otherwise I'd choose, at least, twice the expected output (200w). 3x is the better, if the transmission time is many minutes.

Another thing.? The rated power of 100w, 3db load, bought on ebay or Amazon, is likely not 100w - But 100w for one or two seconds, before it blows.

Best regards, Bruce Hawkins - AC6DN.? Sent from my Android phone.? And from: ac6dn@... <mailto:ac6dn@...>

On Jun 14, 2024 3:39 AM, Wiggle Pig <wigglepig@... <mailto:wigglepig@...> > wrote:


It should be rated to handle the *dissipation* in that unit. So if you put 10 W total into a 3 dB attenuator then it needs to be rated for 5 W dissipation.








--

Dave - W?LEV






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