Great video. I'm thinking about making one myself. I don't have any bus bar around. Could I use a 2, 8 gauge copper wires instead ? I figure this would work. What are your thoughts.
Andrew, Using two wires might create unwanted paths, or loops, for energy to flow. Example: If you set up a radio station having a transmitter, power supply, tuner etc., they ALL get grounded to the SAME point. If you ground them separately/any where you can, "Ground Loops "get created which can cause signals/energy to interfere with each other. I am NO electrical engineer, just relaying my gut feeling about using two separate wires for a buss bar. Or, solder two or three pieces of #8 wire lengthwise, shape the assembly with a hammer, and there you have your solid copper buss bar!
@@TonyButchT Thank you for letting me pick your brain. I like the idea of hammering the #8 gauge wire in to a bus bar. Again thanks for sharing, take care
Nice work but when you can, put your dummy load on an inductance /capacitance meter and see if it doesn't measure about 10-20 microhenrys. Those resistors *each* have an inductive component. It's not ragingly critical unless you go above 50 mHz or are using it when measuring lower power.
OK I'm a bit confused. According to the colors of the bands, those aren't 500 ohm resistors, they are 10 ohm. Am I not seeing the colors right or what?? At 0:24 in the closeup, it sure looks like brown, black, black, brown (reading from the right side) and green is 5 but I see no green on any of those. What am I missing???
The video is a bit confusing! Original plan called for 500ohm 2watt resistors (as you see written on the notebook page) however, I used 1,000ohm 1 watt resistors. The brown band furthest away from the others denotes tolerance, 1% in this case. Beginning at the opposite end there is brown (1) black(0) black(0) = 100, then another brown which is the multiplier, in this case being ten to the first power which is ten. Therefore, you have 100 x 10 which equals 1,000. Twenty 1,000 ohm resistors in parallel yields 50 ohms.
Tony, sorry to be so late in getting back to you. Your composition resistors are fine and the dummy load will work great at HF and probably reasonably well at two meters. (Close enough for government work!) The inductance is caused by the leads (unavoidable) and negligible. Do not despair over drilling the holes. RF will not be a factor and your instincts were good for heat dissipation! I have a Swan commercial 300-watt dummy load that has grillwork for a case. Besides, you will probably want to hear your output in an adjacent receiver. Excellent workmanship! de Bill, k6whp dit dit
KD2HYA for I.D. Thanks for the additional information Bill. I consider it "Elmering", which is a good thing! I learn more every day in this hobby. Example: With regard to your first comment, this led me to research and learn about dummy loads, proper construction and usage. If you did NOT comment: Hey...grab a bunch of resistors...do some easy math...fire up the iron and presto: a dummy load! I checked the one I made against one I purchased and there sure is a difference, especially measuring power. Excellent biography at QRZ! At a yard sale my son picked up a Heathkit HW-8, with it's power supply and manual. Looking forward to setting it up! 73 Tony KD2HYA
When you wrap wire around a core, you create inductance. Wire Wound resistors do this, and the created inductance is not desirable to add to RF signals. What I constructed works well for general purpose, its not "laboratory grade"
Nice job, great information, look for more of your videos
You shouldn't use metal film resistors but instead carbon resistors.
Great video. I'm thinking about making one myself. I don't have any bus bar around. Could I use a 2, 8 gauge copper wires instead ? I figure this would work. What are your thoughts.
Andrew, Using two wires might create unwanted paths, or loops, for energy to flow. Example: If you set up a radio station having a transmitter, power supply, tuner etc., they ALL get grounded to the SAME point. If you ground them separately/any where you can, "Ground Loops "get created which can cause signals/energy to interfere with each other. I am NO electrical engineer, just relaying my gut feeling about using two separate wires for a buss bar. Or, solder two or three pieces of #8 wire lengthwise, shape the assembly with a hammer, and there you have your solid copper buss bar!
@@TonyButchT Thank you for letting me pick your brain. I like the idea of hammering the #8 gauge wire in to a bus bar. Again thanks for sharing, take care
@@TonyButchT little update. I ended up having some 1/2 copper pipe from past a plumbing job. I flattened in my vice. Now I have 2 copper bus bars.
@@andrewgeorgelang Way to go Andrew! Good Thinking!
Nice work but when you can, put your dummy load on an inductance /capacitance meter and see if it doesn't measure about 10-20 microhenrys. Those resistors *each* have an inductive component. It's not ragingly critical unless you go above 50 mHz or are using it when measuring lower power.
Nice! I understood it. Big thumbs up and thank you.
Thank You!
OK I'm a bit confused. According to the colors of the bands, those aren't 500 ohm resistors, they are 10 ohm. Am I not seeing the colors right or what?? At 0:24 in the closeup, it sure looks like brown, black, black, brown (reading from the right side) and green is 5 but I see no green on any of those. What am I missing???
The video is a bit confusing! Original plan called for 500ohm 2watt resistors (as you see written on the notebook page) however, I used 1,000ohm 1 watt resistors. The brown band furthest away from the others denotes tolerance, 1% in this case. Beginning at the opposite end there is brown (1) black(0) black(0) = 100, then another brown which is the multiplier, in this case being ten to the first power which is ten. Therefore, you have 100 x 10 which equals 1,000. Twenty 1,000 ohm resistors in parallel yields 50 ohms.
LOL OK, thanks for clearing that up! It was confusing for sure.
Youre welcome! I'am hobbiest, not a pro...we all learn as we go!
He doubled the power by doubling the number of resistors. Instead of 10 500 ohm, he used 20 1000 ohm.
Measured 13 microhenry's! I do use this on low power 2M HT's. Should carbon resistors have been used? Thank you for this information!
Tony, sorry to be so late in getting back to you. Your composition resistors are fine and the dummy load will work great at HF and probably reasonably well at two meters. (Close enough for government work!) The inductance is caused by the leads (unavoidable) and negligible.
Do not despair over drilling the holes. RF will not be a factor and your instincts were good for heat dissipation! I have a Swan commercial 300-watt dummy load that has grillwork for a case.
Besides, you will probably want to hear your output in an adjacent receiver.
Excellent workmanship!
de Bill, k6whp
dit dit
KD2HYA for I.D.
Thanks for the additional information Bill. I consider it "Elmering", which is a good thing! I learn more every day in this hobby. Example: With regard to your first comment, this led me to research and learn about dummy loads, proper construction and usage. If you did NOT comment: Hey...grab a bunch of resistors...do some easy math...fire up the iron and presto: a dummy load! I checked the one I made against one I purchased and there sure is a difference, especially measuring power. Excellent biography at QRZ! At a yard sale my son picked up a Heathkit HW-8, with it's power supply and manual. Looking forward to setting it up! 73 Tony KD2HYA
pLEASE TELL US if you have measured this box with SWR meter with diffrent bands, i wonder how much close to 1:1 would be such construction ?
im looking for 5 watt 1k ohm resistors too make this a 100 watt dummy load... but cant find them in USA except wire wound
Old vid but very informative thanks
Why can’t you use wire wound resistors?
When you wrap wire around a core, you create inductance. Wire Wound resistors do this, and the created inductance is not desirable to add to RF signals. What I constructed works well for general purpose, its not "laboratory grade"
@@TonyButchT thanks, now I understand.
If my radio is 50 watts then I need at least a 50 watt dummy load ….right???
thanks @James Babcock
why not just use one single flanged resistor?
Yep...you can! Remember to use a resistor rated at the wattage under test. Gets costly at lets say 100watts on up. Can't use wirewound.
Thank you sir
You're very welcome Mohamed!
hello tony god morning .please iam need dummy load 25ohm - 120 watt..thaks...