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108FB027 Profile
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Freebander

Registered: 03-2009
Location: just west of Edinburgh
Posts: 120
Karma: 2 (+2/-0)
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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
16/Mar/2009, 10:25 pm Link to this post Send Email to 108FB027   Send PM to 108FB027
 
Hot Fusion Profile
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Management

Registered: 03-2008
Location: South West England
Posts: 1389
Karma: 7 (+7/-0)
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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. emoticon

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Andy - 26 FB107
16/Mar/2009, 11:04 pm Link to this post Send Email to Hot Fusion   Send PM to Hot Fusion
 
topbuzzuk Profile
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Big Cheese

Registered: 11-2007
Location: Wiltshire, UK
Posts: 2655
Karma: 12 (+12/-0)
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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?

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26FB118
16/Mar/2009, 11:32 pm Link to this post Send Email to topbuzzuk   Send PM to topbuzzuk Yahoo
 
108FB027 Profile
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Freebander

Registered: 03-2009
Location: just west of Edinburgh
Posts: 120
Karma: 2 (+2/-0)
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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
17/Mar/2009, 6:06 pm Link to this post Send Email to 108FB027   Send PM to 108FB027
 
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Management

Registered: 03-2008
Location: South West England
Posts: 1389
Karma: 7 (+7/-0)
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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.

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Andy - 26 FB107
17/Mar/2009, 9:30 pm Link to this post Send Email to Hot Fusion   Send PM to Hot Fusion
 


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