1kW Dummy Load project
- BriansBrain
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1kW Dummy Load project
My new 1kW Dummy Load project
8 x 100Ω - 250W RF resistors - Aliexpress.
188x120x37mm Aluminium Box - ebay.
Heatsink 300x190x50mm - DutchShop.
Copper Strip 120x75x3mm - DutchShop.
Total parts inc post = €155
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Re: 1kW Dummy Load project
This is the Plan of mounting the resistors on the Copper Plate
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Re: 1kW Dummy Load project
Dear Brian,
I don't want to discourage you, but this only works well at low frequencies, you will measure 50 ohms neatly, but you will see that the SWR is not good as the frequency increases.
Look inside the Alpha power HF dummy load to the internal construction and compensation.
I don't want to discourage you, but this only works well at low frequencies, you will measure 50 ohms neatly, but you will see that the SWR is not good as the frequency increases.
Look inside the Alpha power HF dummy load to the internal construction and compensation.
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Re: 1kW Dummy Load project
Dear Brian,
I don't want to discourage you, but this only works well at low frequencies, you will measure 50 ohms neatly, but you will see that the SWR is not good as the frequency increases.
Look inside the Alpha 2100 HF dummy load to the internal construction and compensation (Teflon coax C en Coils).
I don't want to discourage you, but this only works well at low frequencies, you will measure 50 ohms neatly, but you will see that the SWR is not good as the frequency increases.
Look inside the Alpha 2100 HF dummy load to the internal construction and compensation (Teflon coax C en Coils).
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Re: 1kW Dummy Load project
We always used to mount the resistors in a radial pattern around the input socket. The SWR of those loads was never much worse than about 1.15 : 1
"Why is my rig humming?"
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- BriansBrain
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Re: 1kW Dummy Load project
I know that the SWR is not gonna be perfect
Finished putting it together today, gonna test it tomorrow
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Re: 1kW Dummy Load project
Is the copper strip mounted directly to the heatsink or stood off it, cant really tell.
If you ain't had an rf burn then your not running enough power.
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Re: 1kW Dummy Load project
nice work but i do not like it.. why end of coax is not grounded and closer to meddle point od loads.. . need to be wavelength coax velocity.BriansBrain wrote: ↑Tue Apr 25, 2023 6:11 pm
I know that the SWR is not gonna be perfect
Finished putting it together today, gonna test it tomorrow
1kW Dummy Load Finished.JPG
use panel mount soldering coax directly on connector ...
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Re: 1kW Dummy Load project
It's directly on the heatsink, if you look caefully you can see the cutout
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Re: 1kW Dummy Load project
Thanks
OK understand that one
Will that help ?
I am using RG402 ?
Thanks
I will have to get some of them
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Re: 1kW Dummy Load project
OK..... I have just found the spec of RG402
Velocity of Propagation 69.5%
So... https://k7mem.com/Ant_Freq_Wavelength.html
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Re: 1kW Dummy Load project
OK....... for starters I have now grounded the end of RG402
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Re: 1kW Dummy Load project
OK.... you guys are correct...... as usual
I have learn't a lot on about RF this forum
I measured it on the spectrum analyzer and the load does change at higher frequencies
This is the proof on the BIRD
Forward = 100W Reflected = 3.5W
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Re: 1kW Dummy Load project
I bet if you shrunk everything down you could get it a lot better than that. Put the resistors right next to each other so you can solder straight between the pins and get rid of the wires in between. Also see if you can solder the pins at the end of each chain straight down to the copper instead of wiring to a solder tag. You might need a torch or at least a really big iron to get the copper hot enough.
Every piece of wire in there is an inductor which is where your problems coming from.
You might find it runs a bit hotter with the resistors close together but honestly doubt itll make much difference with that big copper block to spread the heat.
3.5w reflected is 1.5:1 SWR which isn't far off. I wouldn't expect to get much better than 1.1:1 maybe 1.2:1 for such a big load.
Every piece of wire in there is an inductor which is where your problems coming from.
You might find it runs a bit hotter with the resistors close together but honestly doubt itll make much difference with that big copper block to spread the heat.
3.5w reflected is 1.5:1 SWR which isn't far off. I wouldn't expect to get much better than 1.1:1 maybe 1.2:1 for such a big load.
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Re: 1kW Dummy Load project
Thanks for the suggestionsjvok wrote: ↑Wed Apr 26, 2023 6:39 pm I bet if you shrunk everything down you could get it a lot better than that. Put the resistors right next to each other so you can solder straight between the pins and get rid of the wires in between. Also see if you can solder the pins at the end of each chain straight down to the copper instead of wiring to a solder tag. You might need a torch or at least a really big iron to get the copper hot enough.
I understand that now
Well considering the cost.......... and that I made it........ it's not that bad then
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Onlineyellowbeard
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Re: 1kW Dummy Load project
You should have told them you were building a George Foreman grill powered by Elenos...
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Re: 1kW Dummy Load project
1kw dummy load
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Re: 1kW Dummy Load project
Good oneyellowbeard wrote: ↑Wed Apr 26, 2023 7:10 pm You should have told them you were building a George Foreman grill powered by Elenos...
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Re: 1kW Dummy Load project
If you have a (nano) Vector Network Analyzer, you can immediately see all changes, only measuring resistance with a universal meter or Bird Wattmeter (reflected power) will not help you any further.
Unfortunately, I can inform you in advance that this method of construction will never work properly, no matter how you are going to place the resistors / internal coaxial cable(ground)and wire.
The Alpha 2100 HF dummy load construction and compensation (Teflon coax C and Coils) goes up to about 60 MHz with these types of resistors and that is not for nothing.
Take a look at the inside of a Bird dummyload on the internet.
They use a funnel there to get things straight down to a few GHZ. (good VSWR over a wide range).
Marcel
Unfortunately, I can inform you in advance that this method of construction will never work properly, no matter how you are going to place the resistors / internal coaxial cable(ground)and wire.
The Alpha 2100 HF dummy load construction and compensation (Teflon coax C and Coils) goes up to about 60 MHz with these types of resistors and that is not for nothing.
Take a look at the inside of a Bird dummyload on the internet.
They use a funnel there to get things straight down to a few GHZ. (good VSWR over a wide range).
Marcel
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Re: 1kW Dummy Load project
I knew I was not gonna have a perfect dummy with this design from the start
All I needed was something I could test repaired the ETG1000 at 500W without melting or blowing up
And I succeeded for a very low price
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