108FB027
Freebander
Registered: 03-2009
Location: just west of Edinburgh
Posts: 120
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Re: WANTED dummy load
I built one of these for tuning up the ft101
tube finals.
http://www.qsl.net/k5lxp/projects/SaltLoad/SaltLoad.html
Made mine from an old coffee jar and about half a teaspoon of salt,,swr is 1.1 up to 30 mhz and takes 100 watts plus no problem
Alan
--- Icom 7300
CRT 6900 v7
Various homebrew antenna
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16/Mar/2009, 10:25 pm
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Hot Fusion
Management
Registered: 03-2008
Location: South West England
Posts: 1389
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Re: WANTED dummy load
That's an interesting slant on the old theme.
He mentions that it's not screened, but surely this could be constructed in a metal tin? Suitable tins have a laquer coating on the inside to prevent the metal from corroding, but this shouldn't be an problem at RF as it would act as the dielectric of a capacitor, and the RF would pass straight through.
I'll have to give this a try, even if just to boil up a litre of water!
Good idea though, and means no faffing around with resistors and oil.
--- Andy - 26 FB107
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16/Mar/2009, 11:04 pm
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topbuzzuk
Big Cheese
Registered: 11-2007
Location: Wiltshire, UK
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Re: WANTED dummy load
i just bought a job lot of stuff off of a ham goin qrt and amongst it was a large tin with silver sand and resistors, he said it was quiet high power useable so i doubt i'll be building one now.
But.. how simple is that salt water and a jar idea, i might just try that to se what happens. i didnt read the whole article so just wonder what the power rating is for the jar of water?
--- 26FB118
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16/Mar/2009, 11:32 pm
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108FB027
Freebander
Registered: 03-2009
Location: just west of Edinburgh
Posts: 120
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Re: WANTED dummy load
The one i made with the coffee jar was made with the inner copper cable from rg 213,just stripped the plastic from the copper and soldered it to the so239.
Just remember to put silcon sealent around the so239 to prevent evaperation.
I cant give a figure on max input power,but can get 120 watts from the ft101 while tunning up with the jar just getting slighty warm over maybe 2/3 mins.
Just one thing though,,the total amount of salt i used was maybe less than half a teaspoon,so just add a little salt and give it a stir then check your swr on low power,then add more salt if needed to get the swr correct.
Alan
Last edited by 108FB027, 17/Mar/2009, 6:09 pm
--- Icom 7300
CRT 6900 v7
Various homebrew antenna
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17/Mar/2009, 6:06 pm
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Hot Fusion
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Re: WANTED dummy load
I suppose you could test the resistance using a multimeter, rather than risk the transmitter's output stage.
You'd be looking for a resistance of 50 ohms, plus or minus 5.
--- Andy - 26 FB107
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17/Mar/2009, 9:30 pm
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