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Author Topic: Testing Transmitter Power  (Read 1326 times)

Mark Hannah

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Testing Transmitter Power
« on: August 25, 2017, 11:55:35 am »

I have been using a TTi PSA6005 for coordination for about a year and want to broaden my usage of the device.  I want to share my "logic" and get confirmation from the community.  And if my logic is wrong, an explanation.  Oh, and perhaps more important than my ego, to not damage the SA.

Moving forward...

A device can output up to 100 mW.  The TTi can measure up to an +20 dBm signal (damage after +25 dBm).  20 dBm = 100 mW.  Consequently, I should be able to use the TTi to test the SR 2050 without damage to TTi.

If I'm correct,

1) what would I set the reference level to?  0 dBm?
2) should I be concerned with frequency?  As of now, I would only be testing in VHF and UHF.

Thank you in advance...
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Henry Cohen

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Re: Testing Transmitter Power
« Reply #1 on: August 25, 2017, 06:38:02 pm »

1) what would I set the reference level to?  0 dBm?
2) should I be concerned with frequency?  As of now, I would only be testing in VHF and UHF.

1) Set reference level to +20. But have a 10dB attenuator on hand in case the composite energy is too much and the measurement is off scale.

2) Only somewhat, as long as the frequency is within the span setting and you place the marker at the peak. You will however get a more accurate measurement with a span equal to that of the occupied channel bandwith (200kHz for most analog equipment) along with the lowest RBW possible at that span and the detector set for RMS. Best to just center the frequency in the span. If however you have option U02, you can use the Channel Power measurement. 

Use the shortest piece of coax possible and best to use a low loss coax. (at least braid over foil shield, or better still for this testing, double braided). Allow for at least 1-2 dB coax and connector loss even with the low loss coax. Add an additional .5dB for each adapter.
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Henry Cohen

CP Communications    www.cpcomms.com
Radio Active Designs   www.radioactiverf.com

Mark Hannah

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Re: Testing Transmitter Power
« Reply #2 on: August 29, 2017, 12:43:26 pm »

Henry,

For now, I am using 100' of 9046 as my attenuator.  I will put a short piece of 400-UR and an attenuator on the wish list.

Have you memorized ratios between standard round number mW and dBm so you don't have to use a calculator every time to compare the analyzer reading to product specifications?

Thank you,
Mark

1) Set reference level to +20. But have a 10dB attenuator on hand in case the composite energy is too much and the measurement is off scale.
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Henry Cohen

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Re: Testing Transmitter Power
« Reply #3 on: August 30, 2017, 07:57:51 pm »

Have you memorized ratios between standard round number mW and dBm so you don't have to use a calculator every time to compare the analyzer reading to product specifications?

Remember these three constants:
  0dBm = 1mW.
  A 3dB change doubles (or halves) the power.
  A 10dB change is a tenfold (or one tenth) change in power.

After time it'll simply become muscle memory that
  10dBm = 10mW
  13dBm = 20mW
  17dBm = 50mW
  20dBm = 100mW
  24dBm = 250mW
  30dBm = 1W
  36dBm = 4W
  40dBm = 10W
  47dBm = 50W
  50dBm = 100W  (I also work with some higher power equipment)
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Henry Cohen

CP Communications    www.cpcomms.com
Radio Active Designs   www.radioactiverf.com
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