Transmit Power

Q. How much RF power can a ham legally transmit with?

A. It varies with frequency/band, license class and licensing authority.  Maximum transmitter power levels are regulated by country; we will discuss the rules in the USA here.  It is one of the important regulatory subjects covered by the question pool for amateur radio license exams.

The average VHF/UHF handheld transceiver (HT) puts out 5 to 10W maximum.  A typical VHF mobile rig is capable of 50 to 75W.  Most modern HF transceivers peak at 100W.

Before we get to maximum levels, in the USA the general guidance is to use the least amount of power needed.


Of course, that’s easier said than done so many hams just go with the radio’s max power setting unless they know that a lower power setting works well or are operating a weak-signal mode.

In general, US hams are limited to 1500W (1.5kW) peak envelope power (PEP).  That doesn’t mean you should, just that you legally can.  This applies to General and Extra Class licensees for most bands and Technicians at VHF and higher.


There are specific power limitations on 2200m, 630m, 60m, and 30m bands:


As you can see from the band plan (based on FCC regulations), Technician class licensees have 200W power limits on the HF bands, with HF privileges rather limited already.


So why a would a ham want to use more power than their stock radios can transmit, and how would they increase their default power level?

To answer the why question, it is simply that more transmit power gives more signal energy at the receiving end.  Increased wattage improves the chance of making contacts under poor conditions by overpowering signal attenuation and background noise.

To answer the how question, hams use RF amplifiers (linear power amps) to increase the power of their basic transmitter.


This RF power amplifier must operate linearly so that it does not distort the waveform.


RF amps can be for single or multiple bands.  More commonly you will find multi-band HF (or HF+6m) amplifiers which tend to be large boxes:

HF Amp

You will also find broadband or single-band VHF and/or UHF amplifiers:

Mirage 2m Amp

Besides all these commercially available amplifiers some hams build their own.  This is partly a nod to tradition—hams being DIY types—and partly because commercial amps may not be readily available for very low or high frequencies.

Ham-speak note:  When a ham says that s/he is running barefoot it means raw transmitter output power, unamplified beyond the stock radio capabilities.  Typically 100W or less.

Power amps are not just for handheld VHF/UHF FM transceivers; they can amplify most any amateur radio RF signal.  They are mainly useful for voice (AM, SSB, FM) and video Continue reading

DC Power Supply Ratings

Except for handheld transceivers (HTs), most modern ham radio gear uses 12V DC power.  You may find vintage radios and more recent designs that require AC main power, but the VHF/UHF mobile radios and the latest HF transceivers run off of 12-13.5VDC.   Nearly all of the modern all-band transceivers use 12VDC power as well so that they can be operated mobile or portable.


If you want to install a mobile radio in your home instead of your vehicle (an excellent idea, by the way, if you don’t have an all-band rig) you will need a DC power supply for it.  Same goes for the latest HF transceivers; they require 12VDC power but don’t often include the power supply.  Additionally, many radio accessories require 12V nominal power.

Astron RS-35M 35 Amp DC Power Supply with Meters 120V AC in / 13.8 Volts DC Out     MFJ 4230MVP 30 AMP Switching Power Supply With Meter, 4-16 Volts & Power Poles    NEW Pyramid PS8KX AC to DC 8 Amp 12V Fully Regulated Low Ripple Power Supply     NEW QJE PS50SWIII 50 Amp Switching Power Supply with Volt/Amp Meter     JETSTREAM JTPS30LCD - 9 ~ 12 Volt 30 AMP Max Switching Power Supply w/ LCD Meter

Examples of ham gear DC power supplies.

The 50W mobile radios and 100W transceivers need a lot of current at 12V to operate at full output power.  Sizing a DC power supply for these plus accessories isn’t quite as straightforward as it would seem.

For one, you cannot simply take radio output power and divide by 12V to get amperes. Continue reading