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Call Sign : 26-CT-4694, M7EUS Posts : 232 Times Thanked : 14 Join date : 2022-11-13 QTH or Location : Dorchester UK Equipment Used : Yaesu FT950, 66FT Endfed Antenna, Various Other Bits and Pieces Age : 57
Subject: How to read ERP? Sat Jul 08, 2023 11:23 pm
I bought an ATU off EvilBay and exchanged a few messages with the seller, who happened to be a full licence holder. Not that I am going to do it, but he said that with a compromised antenna that as a Foundation licence holder could probably run 15W to 20W and still remain within the legal ERP.
My question to the usual suspects (Victor) would be how do you actually measure ERP? I am sure there is a significant amount of maths that could be used to work it out, it just got me curious and would like to add that I have a cat and am not one
Ain't I just full of questions today.
Edit Just realised he was talking rubbish about the power being ERP for Foundation, most bands are PEP.
SangueG Major contributor
Call Sign : 26-CT-3971 / 2E0LMI Posts : 1164 Times Thanked : 68 Join date : 2021-01-30 QTH or Location : Cirencester, Gloucestershire Equipment Used : Little radios, home-made antennas
Subject: Re: How to read ERP? Sun Jul 09, 2023 7:32 am
You're correct Mark, there are not many frequency allocations that state maximum erp, most state pep. To calculate your erp you need to take the output of your transmitter, subtract feeder losses, then multiply (or subtract) the gain (or loss) of your antenna antenna.
If you've got 3db (halving your power) feeder losses and your antenna has a 1db loss, then for a max erp of 10W the person you messaged has given good theoretical figures.
Kept it simple for now, but does that help and make sense?
FamousPablo, Victor and 13oots2 like this post
chazwozza Senior contributor
Posts : 124 Times Thanked : 1 Join date : 2020-02-15 QTH or Location : England Equipment Used : Radios
Subject: Re: How to read ERP? Fri Jul 28, 2023 8:28 am
Wouldnt worry about erp to much unless using a beam and pointing at houses other than that the power you can use is at antenna point
43CT016 Major contributor
Call Sign : 43-CT-016 Posts : 357 Times Thanked : 22 Join date : 2019-11-17 QTH or Location : Perth Equipment Used : iCom IC-7610/IC-9700/IC-705 Age : 55
Subject: Re: How to read ERP? Fri Jul 28, 2023 9:48 am
SangueG wrote:
You're correct Mark, there are not many frequency allocations that state maximum erp, most state pep. To calculate your erp you need to take the output of your transmitter, subtract feeder losses, then multiply (or subtract) the gain (or loss) of your antenna antenna.
If you've got 3db (halving your power) feeder losses and your antenna has a 1db loss, then for a max erp of 10W the person you messaged has given good theoretical figures.
Kept it simple for now, but does that help and make sense?
Aren't your power limits set as "into the antenna", and not ERP though?
SangueG Major contributor
Call Sign : 26-CT-3971 / 2E0LMI Posts : 1164 Times Thanked : 68 Join date : 2021-01-30 QTH or Location : Cirencester, Gloucestershire Equipment Used : Little radios, home-made antennas
Subject: Re: How to read ERP? Fri Jul 28, 2023 1:52 pm
43CT016 wrote:
SangueG wrote:
You're correct Mark, there are not many frequency allocations that state maximum erp, most state pep. To calculate your erp you need to take the output of your transmitter, subtract feeder losses, then multiply (or subtract) the gain (or loss) of your antenna antenna.
If you've got 3db (halving your power) feeder losses and your antenna has a 1db loss, then for a max erp of 10W the person you messaged has given good theoretical figures.
Kept it simple for now, but does that help and make sense?
Aren't your power limits set as "into the antenna", and not ERP though?
Mostly, yes. But there are a few exceptions if you check the licence terms and conditions.
Ivy Mike Major contributor
Call Sign : 26CT4113/G1HWY Posts : 464 Times Thanked : 12 Join date : 2021-05-16 QTH or Location : IO90uv Equipment Used : ICOM radios/antenna farm Age : 69
Subject: Re: How to read ERP? Sun Jul 30, 2023 8:37 am
13oots2 wrote:
I bought an ATU off EvilBay and exchanged a few messages with the seller, who happened to be a full licence holder. Not that I am going to do it, but he said that with a compromised antenna that as a Foundation licence holder could probably run 15W to 20W and still remain within the legal ERP.
My question to the usual suspects (Victor) would be how do you actually measure ERP? I am sure there is a significant amount of maths that could be used to work it out, it just got me curious and would like to add that I have a cat and am not one
Ain't I just full of questions today.
Edit Just realised he was talking rubbish about the power being ERP for Foundation, most bands are PEP.
RSGB EMF calculater does it all for you.
Stick in your station details and you will also cover yourself for complaince.
Today at 4:30 pm by Mr T
Subject: How to read ERP? 
