MR100 Youtube Video / Calibration

[andyzot]

Hi, I've been looking up your the Radio Preppers videos on YouTube and found the one showing the calibration of the MR100.
I have the just purchased the SARK100 which is pretty similar but I'm very new to amateur radio and not great with electronics, can I please ask what rating of resistors and in what sequence did you make them suitable loads for calibration?
I have purchased several resistors which I thought would equate to the correct ratings but I'm having lots of problems getting it right, I have a meter which is giving some odd readings.
Thank you in advance.

[gil]

Hello,

You need 50ohm, 150ohm and 274ohm resistors.

I make a 50ohm resistor by putting two 100ohm resistors in parallel. To get 150ohm I add a 100ohm resistor to that bundle, in series. The 274ohm resistor comes in that value.

This way you only have to buy 100ohm resistors and a 274ohm resistor. I bought a bunch of 100ohm 2W resistors and with those left over made myself a dummy load  ;D

I hope this helps...

Gil.

[andyzot]

Thank you Gil, appreciate the quick response, do I have to consider the power rating, I'm struggling to locate a 274 ohm resistor in the UK that's above 250mW.

[gil]

I'm struggling to locate a 274 ohm resistor in the UK that's above 250mW.

You don't need more than that. The MR100 outputs a ridiculously small amount of power because that's all it needs... Any 274ohm resistor will do.

Gil.

[andyzot]

Thank you.

[CroPrepper]

Hi,

I am also pinpointing that MR-100 to buy. It seems to give good bang for the buck. Although I really would not want to calibrate it because I think I'd do more wrong than good. I got basic electronic knowledge but that procedure like Gil showed on YT seems pretty cumbersome and prone to errors. How else to check if it's calibrated correctly? Measuring an SWR with a 2nd calibrated device and then compare the results?
On another video (https://www.youtube.com/watch?v=_qjfaMuWF4EI saw the guy using it with USB power supply. Although on the specs it says it is powered by 12V I don't understand how he can run it with 5V..

[gil]

I really would not want to calibrate it because I think I'd do more wrong than good.

Yep, mine has been acting up since I calibrated it... I have also heard that it really needs 12V to be accurate.

Gil.

[CroPrepper]

I really would not want to calibrate it because I think I'd do more wrong than good.

Yep, mine has been acting up since I calibrated it... I have also heard that it really needs 12V to be accurate.

Gil.

I read in forums that people had difficulties finding a suitable plug for the powersupply socket. Is that true? Unfortunately there is no specification on the plug what to get. I guess that are those flaws for cheap knockoffs ?

[gil]

I read in forums that people had difficulties finding a suitable plug for the powersupply socket. Is that true?

No, same plug as the standard DC plug on all my radios.

Gil.

[CroPrepper]

Thank you for the fast reply  :)