Page 1 of 1
Dummy load
Posted: Thu Sep 08, 2022 6:43 pm
by toshiba1
Have one of these laying around, not used it before so just wanted to check if its a goer or not? Its says 0 / 500 mhz 50 watt... Dry dummy load? is that something other than a dummy load or am i being a bit dumb? Hypothetically keeping it under 50 watts is good for cbs but for fm transmitters? Does the same principle apply?
https://www.nevadaradio.co.uk/product/zetagi-dl50/
Re: Dummy load
Posted: Thu Sep 08, 2022 11:09 pm
by yellowbeard
It's a dummy load, some types are filled with oil is what the "dry" bit means.
Re: Dummy load
Posted: Fri Sep 09, 2022 12:25 am
by sinus trouble
I wouldnt put 50watt into that for more than a few seconds!
You could force cool it using a fan? That may allow continuous use?
Or you could salvage the "dummy" resistor and submerge it in mineral oil which would serve a similar purpose!
I posted my DIY Dummy on here somewhere? I will try to find the link?
Re: Dummy load
Posted: Fri Sep 09, 2022 12:29 am
by sinus trouble
Re: Dummy load
Posted: Fri Sep 09, 2022 1:52 am
by Albert H
That Zetagi "dummy load" is made for dummies - it might withstand 50 Watts for a second or two, but would probably suffer irreparable damage! It's rated like the Zetagi "50 Watt" CB burners. I've seldom seem one - with 4 Watts of drive - put out more than about 15 Watts!
Re: Dummy load
Posted: Fri Sep 09, 2022 2:04 pm
by toshiba1
yellowbeard wrote: ↑Thu Sep 08, 2022 11:09 pm
It's a dummy load, some types are filled with oil is what the "dry" bit means.
gotcha
Re: Dummy load
Posted: Fri Sep 09, 2022 2:09 pm
by toshiba1
sinus trouble wrote: ↑Fri Sep 09, 2022 12:25 am
I wouldnt put 50watt into that for more than a few seconds!
You could force cool it using a fan? That may allow continuous use?
Or you could salvage the "dummy" resistor and submerge it in mineral oil which would serve a similar purpose!
I posted my DIY Dummy on here somewhere? I will try to find the link?
To be honest Sinus it would be no more than a couple of watts but even then how long could i use it for, the 50 was hypothetical. I did see your dummy tin, but its having the time to build, the parts on hand and could i?
Re: Dummy load
Posted: Fri Sep 09, 2022 2:12 pm
by toshiba1
Albert H wrote: ↑Fri Sep 09, 2022 1:52 am
That Zetagi "dummy load" is made for dummies - it might withstand 50 Watts for a second or two, but would probably suffer irreparable damage! It's rated like the Zetagi "50 Watt" CB burners. I've seldom seem one - with 4 Watts of drive - put out more than about 15 Watts!
And it cost me about £25 quid, so its garbage then lol Whats the point of the rating?
Re: Dummy load
Posted: Fri Sep 09, 2022 2:43 pm
by toshiba1
Actually i could manage that... couple of questions though.
20 x 1k ohm ?
2 Zener? value? Diodes
Value of the ceramic cap?
Is that a piece of tiny metal wire held in by wax next to so239? is it for some sort of sensor to stick a probe on to see how hot it is?
Re: Dummy load
Posted: Fri Sep 09, 2022 5:43 pm
by toshiba1
Ignore the sensor bit, just saw more of that thread. Cheers for the help.
Re: Dummy load
Posted: Sat Sep 10, 2022 12:13 am
by sinus trouble
toshiba1 wrote: ↑Fri Sep 09, 2022 2:12 pm
And it cost me about £25 quid, so its garbage then lol Whats the point of the rating?
No! Its not a waste of money! It is more than adequate for tuning and testing small Exciters Etc...
The problem with these Dummy loads is the Manufactures vague maximum ratings!
Often there are times when you need the Dummy to dissipate full output of a PA for an extended duration!
The actual long term dissipation of this product in reality is more like 50% less of the rated max power!
Re: Dummy load
Posted: Sat Sep 10, 2022 5:35 pm
by toshiba1
sinus trouble wrote: ↑Sat Sep 10, 2022 12:13 am
toshiba1 wrote: ↑Fri Sep 09, 2022 2:12 pm
And it cost me about £25 quid, so its garbage then lol Whats the point of the rating?
No! Its not a waste of money! It is more than adequate for tuning and testing small Exciters Etc...
The problem with these Dummy loads is the Manufactures vague maximum ratings!
Often there are times when you need the Dummy to dissipate full output of a PA for an extended duration!
The actual long term dissipation of this product in reality is more like 50% less of the rated max power!
Cheers Sinus, at least its good for what i need then. Appreciated.
Re: Dummy load
Posted: Sun Sep 11, 2022 12:17 am
by sinus trouble
No problem!
If you do need a larger dummy? There are so many ways to build them on a budget!
My Dummy is just an example! For a 60 watt load using 3 watt resistors!
1000 ohm divided by 20 equals 50 ohm! You could double the power by!
2000 ohm divided by 40 equals 50 ohm! Which would give you 120 watt of power!!
It all depends on your engineering skills and creativity!
Re: Dummy load
Posted: Wed Sep 14, 2022 3:26 pm
by SundayGroover
Albert H wrote: ↑Fri Sep 09, 2022 1:52 am
That Zetagi "dummy load" is made for dummies - it might withstand 50 Watts for a second or two, but would probably suffer irreparable damage! It's rated like the Zetagi "50 Watt" CB burners. I've seldom seem one - with 4 Watts of drive - put out more than about 15 Watts!
Hence why Zetagi power meters read so generously - makes their own linear amps look better!