## Field Day 2020 In Retrospect: The Core Planners.

Sunday, 23. August 2020

Open Source, Ham Radio, The Universe & Everything…

Sunday, 23. August 2020

Monday, 23. March 2020

Every time I have to figure out ERP or dB gain I always have to search the Internet to find the formulas. Well, I figured I could just look them up here if I posted them, so here they are!

Calculate dB gain based on actual output change. This is good for working out how much gain and amplifier gives you: 10 X log(power/refpower) = dBm Gain / loss Example using 65 Watt output from radio into an amp and seeing that the output power is 500 Watts. 10 X log(500/65) = 8.86 dBm gain Calculate dBm from output power: 10 X log(1000 X output watts) = Total DB Output Example using a 100 Watt output. 10 X log(1000 X 100) = 50 dBm Output Calculate output power from dBm 10^(dBm/ 10) / 1000 Calculate ERP based on radio output and Antenna gain: Radio Power * 10^(dBm gain/10) = ERP Example using 100 Watts radio output and a dB gain of 9 dBm from the antenna system: 100 * 10^(9/10) = 794 Watts Calculate percentage of gain or loss based on dB 1 - (10^((-(dBm Loss/10)))) = Percentage of Loss 10^(dBm Gain/10) = Percentage of Gain Example using a 3 dBm loss and gain: Loss: 1 - (10^((-(3/10)))) = 50% Gain: 10^(3/10) = 200% Calculate SWR Power Loss Percentage: (SWR -1 )Â² / (SWR + 1)Â² = Percentage of Loss Power and Attenuation Calculations: (all voltages are RMS) Drop in dBm = 20 x log(R1 / R2) Example: 50dBm = 20 x log(8000 / 25) R1 = 10^(dBm / 20) x R2 V = âˆš(Watts x 50Î©) Watts = VÂ² / 50Î© Watts Required = VÂ² / R1 Bulletin 65 Formulas: Power Density: S = PG / 4Ï€RÂ² Where: S = power density as mW/cm2 P = power at input of antenna G = power gain of antenna in the direction of interest R = distance to the center of the radiation of antenna Max Power for Distance: Max Power Density X (4Ï€ X (DistanceÂ²) = Max Power Minimum Distance: Square Of((Power / Max PD) / (4Ï€)) Adding for Reflection: ERP X (1.6)Â² There are the two I use all the time. These two also serve as a really good platform for all sorts of calculations. One note, if you are looking for Voltage Gain, change the base 10 to base 20.

— Stu

Wednesday, 24. July 2019

Tuesday, 23. July 2019

Saturday, 20. July 2019

Saturday, 20. July 2019

Tuesday, 4. June 2019

Monday, 9. April 2018

That question comes up a lot when talking to new hams. Although discussed in some detail in the ARRL Technician’s Handbook, the actual Technician test (at the time of this writing) has very few questions that mention contesting. Many General and Extra class operators don’t seem to get *‘the whole contest thing’* as well.

So why are contests important? Why should we care about radio sport at all? And what does this have to do with the new proposal put forward by ARRL to the FCC to grant additional HF privileges to Technicians?