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More pins for the Raduino! An RF gain control for the uBITX!


Don, ND6T
 

I just posted these, and more, on www.ND6T.com
More to come.
Have fun!
-Don, ND6T


VE7WQ <v@...>
 

Thank you Don,

your blog is a treasure trove, you are a fine artist as well.

The last time I saw an illustration like this, was in a 19th century sciense book:

Question: how can I make up a 50 Ohm 10W dummy load, 

for the B40 out of easily available resistors? 

The store don't have 50 Ohm 10W or 2x 100 Ohm 5W resistors here.


73! George

VE7WQ


Wednesday, February 21, 2018, you wrote:

www.ND6T.comhttp://www.ND6T.com

DCvGI> More to come.

DCvGI> Have fun!

DCvGI> -Don, ND6T


Thomas Sharka
 

Use a multiple of 50 with and additive amount of watts. Put them in parallel and you'll have 50 ohms at 10 watts.

Example: 5 times 50 = 250 ohms each, 5 times 2 watts each equals 10 watts.
Example: 20 times 50 = 1000 ohms, 20 times 1/2 watt each equals 10 watts.

Kirchoff's Law is your friend. Also don't use wire wound resistors. They're inductive.
 


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On Wednesday, February 21, 2018 7:23 PM, VE7WQ <v@...> wrote:


Thank you Don,
your blog is a treasure trove, you are a fine artist as well.
The last time I saw an illustration like this, was in a 19th century sciense book:
Question: how can I make up a 50 Ohm 10W dummy load, 
for the B40 out of easily available resistors? 
The store don't have 50 Ohm 10W or 2x 100 Ohm 5W resistors here.

73! George
VE7WQ

Wednesday, February 21, 2018, you wrote:
DCvGI> More to come.
DCvGI> Have fun!
DCvGI> -Don, ND6T



Don, ND6T
 

Yes, what he (Thomas) said! But keep them close, no big runs. Unless you are going to feed full CW into it for a long time, go for less power dissipation.5 watts will do for 10 PEP SSB continuous. Even less needed for shorter times. Best of all, experiment!
And thank you VERY much for the kind words! Best 73, Don


VE7WQ <v@...>
 

Thank you Thomas,


just to be sure, 

using 5 pieces a 250 Ohm 2W composite resistors in parallell,

will make a 50 Ohm 10W dummy load. Right?


73! George

VE7WQ


Wednesday, February 21, 2018, you wrote:

TSvGI> Use a multiple of 50 with and additive amount of watts. Put them in

TSvGI> parallel and you'll have 50 ohms at 10 watts.

TSvGI> Example: 5 times 50 = 250 ohms each, 5 times 2 watts each equals 10

TSvGI> watts.Example: 20 times 50 = 1000 ohms, 20 times 1/2 watt each equals 10 watts.

TSvGI> Kirchoff's Law is your friend. Also don't use wire wound resistors. They're inductive. 



VE7WQ <v@...>
 

Thank you Don,


will watch that, your note is appreciated.


73! George

VE7WQ


Wednesday, February 21, 2018, you wrote:

DCvGI> Yes, what he (Thomas) said! But keep them close, no big runs. Unless you

DCvGI> are going to feed full CW into it for a long time, go for less power

DCvGI> dissipation.5 watts will do for 10 PEP SSB continuous. Even less needed

DCvGI> for shorter times. Best of all, experiment!

DCvGI> And thank you VERY much for the kind words! Best 73, Don


Don, ND6T
 

Yes, the reciprocal of the sum of reciprocals. If you have them, just check with an ohm meter. Good to do that anyway, since they aren't always as marked. -Don


Thomas Sharka
 

Yep, but just for fun try nine 470 ohm resistors and one 1.2 K ohm resistors in parallel. All should be 1 watt or better.
 


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On Wednesday, February 21, 2018 8:31 PM, VE7WQ <v@...> wrote:


Thank you Thomas,

just to be sure, 
using 5 pieces a 250 Ohm 2W composite resistors in parallell,
will make a 50 Ohm 10W dummy load. Right?

73! George
VE7WQ

Wednesday, February 21, 2018, you wrote:
TSvGI> Use a multiple of 50 with and additive amount of watts. Put them in
TSvGI> parallel and you'll have 50 ohms at 10 watts.
TSvGI> Example: 5 times 50 = 250 ohms each, 5 times 2 watts each equals 10
TSvGI> watts.Example: 20 times 50 = 1000 ohms, 20 times 1/2 watt each equals 10 watts.
TSvGI> Kirchoff's Law is your friend. Also don't use wire wound resistors. They're inductive. 




VE7WQ <v@...>
 

Thank you Thomas,


will do, for sure. The local store got those in stock.


73! George

VE7WQ


Wednesday, February 21, 2018, you wrote:

TSvGI> Yep, but just for fun try nine 470 ohm resistors and one 1.2 K ohm

TSvGI> resistors in parallel. All should be 1 watt or better. 




Dexter N Muir
 

All above, plus ease of procurement: 20 x 1000 parallel = 50 ohms, 20 x 1/2 = 10 Watts. Matrix 4x5 for least lead length.


VE7WQ <v@...>
 

Thank you Dexter,


it's getting better and better all the time. 

I'll delay my shopping for a while :)


73! George

VE7WQ


Wednesday, February 21, 2018, you wrote:

DNM> All above, plus ease of procurement: 20 x 1000 parallel = 50 ohms, 20 x

DNM> 1/2 = 10 Watts. Matrix 4x5 for least lead length.


al_91dak@...
 

While we're at it, why not 40x 2k 1/4W?


Thomas Sharka
 

It's workable, (lotsa work though!), but at that stage, the area of the thing becomes antenna-like. I can remember my elmer, (RIP Walt), demonstrating how a shielded air-cooled dummy load could be heard for a block with a portable transceiver. It was very directional, but still...


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On Thursday, February 22, 2018 11:20 AM, "al_91dak@..." <al_91dak@...> wrote:


While we're at it, why not 40x 2k 1/4W?