Connect with us

Return loss and effective radiated power

Discussion in 'Radio and Wireless' started by SparksFly, Aug 21, 2021.

Scroll to continue with content
  1. SparksFly

    SparksFly

    10
    0
    Jan 7, 2019
    Hello,

    I've been thinking about ERP/EIRP and how they're calculated. I see various definitions, but all broadly appear to be;

    EIRP = Ptransmitter - Lcable + Gantenna
    where P = power, L = loss, G = gain.

    That does make some sense, however I have been unable to find any resources that mention the effect of VSWR or return loss. RL is a loss, but they're don't fit into the cable loss parameter (ie insertion loss).

    To take an example, say I had a transmitter at 100dBm, an insertion loss of 4dB and an antenna gain of 3dBi then the EIRP would be 99dBm. Say I then tested my antenna and found it was a really bad match at my intended frequency, and 50% of my power was being reflected back into the transmitter. Following the formula above, the EIRP would still be 99dBm, but only half that (96dBm) would actually be "leaving" the antenna.

    Does EIRP take into account RL in a way that I've not realised, or is it deliberately not in there?

    Thank you!
     
  2. bertus

    bertus Moderator

    2,033
    766
    Nov 8, 2019
    Hello,

    Have a look at the attached PDF.

    Bertus
     

    Attached Files:

  3. SparksFly

    SparksFly

    10
    0
    Jan 7, 2019
    Wow, that's an eye opener. I continue to be amazed at how little I know! That answers everything. Thank you Bertus.
     
  4. bertus

    bertus Moderator

    2,033
    766
    Nov 8, 2019
    Hello,

    BTW, 100dBm is a huge amount of power ( 10 MegaWatt ).
    0 dBm = 1 mili Watt
    30 dBm = 1 Watt
    60 dBm = 1 Kilo Watt
    90 dBm = 1 Mega Watt
    Have a look at the power table.

    Bertus
     

    Attached Files:

    davenn likes this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Similar Threads
There are no similar threads yet.
Loading...
Electronics Point Logo
Continue to site
Quote of the day

-