Discussion in 'Electronic Repair' started by [email protected], May 17, 2007.

1. ### Guest

I can't remember my formulas. If I have a transmitter that puts 1 watt
into a beam antenna that has a gain of 8.0DB what is my EFR? Please
show the work. I need to be able to demonstrate this to a customer.
Thanks alot.
Lenny Stein
Barlen Electronics.

2. ### Arfa DailyGuest

Just show him the calculator on this site

http://www.csgnetwork.com/antennaecalc.html

Should do the job.

Arfa

3. ### CharlesGuest

Take the anti-log of 0.8 (in this case).

based on:

8 dB = 10 x log (X/1)

divide both sides by 10 and then take the anti-log (10^x key).

4. ### Fred McKenzieGuest

Lenny-

Charles' method should work for you. If a customer asks, you need to
know more about the antenna's gain - is it compared to an isotropic
antenna (dBi) or compared to a dipole (dBd)? Note that 0 dBd = 2.1 dbi.
An antenna with isotropic gain of 8 dBi would have a gain of 5.9 dB with
respect to a dipole.

The isotropic gain is useful for calculating field strength at a
distance, but gain with respect to a dipole is easier to measure!

Fred

5. ### Arfa DailyGuest

The calculator that I pointed Lenny at does it for dBi and dBd. A lot easier
to just show your customer something that goes ahead and does the job,
rather than faffing about in front of him with a calculator, working with a
formula and numbers that you're not totally easy with ...

Arfa

6. ### CharlesGuest

He posted "Please show the work."

7. ### Arfa DailyGuest

That is true, but I assumed that he asked this such that he could
re-familiarise himself with the math so that he would be able to demonstrate
to his customer how to work it out. Based on my many years of dealing with
customers, and making myself look dumb on occasion by trying to explain
something that I was not properly familiar with, I just felt that it might
look slicker to the customer to be able to just enter the figures and see
the results, for both comparison schemes, instantly shown. If he really
wants to go down the route of doing it all himself, Google will turn up many
hits if he just enters " Antenna ERP " as the search string.

Arfa