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humptybump

Well Known Member
To all those building panels, here's a "practice project" for you.

To prevent damage to the radio while powering you panel on the bench, it's a good practice to connect dummy RF loads to the antenna connectors.

I decided I'd build mine. The resistors, BNC connectors and brass plate all came from Amazon.com. The oil (fills the can) is off the shelf from any auto parts or Walmart type of place. The quart paint cabs came from my local paint supplier.

This RF load is 50 ohms and can handle 120 watts (more for short transmissions).


 
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Have you checked the SWR of that at 1 GHz? Those are pretty long leads.

If those are metal film resistors, you will have other issues as well.

Paige
 
PaigeHoffart said:
Have you checked the SWR of that at 1 GHz? Those are pretty long leads.

If those are metal film resistors, you will have other issues as well.

Paige
Click to expand...

Great project but +1 on checking the VSWR at 1Ghz before connecting your transponder to it. Little things (like wire sizes, lengths and resistor material) become critical as the transmitted frequency goes above about 400Mhz. Not saying it won't work, but better safe than frying a $$$$.$$ transponder.

:cool:
 
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Glen,
I would be happy to log the VSWR data on your dummy load, my test equipment will go up to 3300 MHZ.
If you are interested, send it out and I will turn it around quickly.
 
Don, thanks for the offer. I have a local contact. We'll run tests at the range of common frequencies and report back.
 
An easy way to make a 1GHz dummy load is just a 100' roll of RG-58, the cable attenuation will take care of 99% of the power dissipation. It won't work as well at lower frequencies, but if you feed your dummy load with a long length of RG-58, you would probably see less than a 1.2 SWR from HF through 2+GHz (the cable loss takes care of the higher frequencies, and the resistors handle the lower frequencies)

Paige
 
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The only 100' coax I have is LMR-400 ... I don't think its bad enough to wor as a "loss disapation" feed :cool:
 
LMR-400 is nice stuff .. about 3.9dB/100' at 900 MHz; RG-58 on the other hand is about 45 dB/100' at 900 MHz ... more than 10x worse!
 
Sam, LOL!

usually I'm the one googling every third word :)

I'm not sure what is says that I understood everything in Bill's reply :eek:
 
RF guys talk that way because they have been exposed to to much radiation. us digital guys keep it simple.... on and off.....:D


bob burns
RV-4 N82RB
 
n82rb said:
RF guys talk that way because they have been exposed to to much radiation. us digital guys keep it simple.... on and off.....:D


bob burns
RV-4 N82RB
Click to expand...

There are 10 kinds of people in the world. those that can count binary and those that can not
 
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