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Isotron 80/40

Get ready for the fall season. The easiest way to operate 80 and 40M.

 

www.isotronantennas.com

 

The Best Way To Operate HF 

Easy Installation

Excellent Performance

Durable Construction

CC&R Friendly (XYL also) 

 

The articles will also be on our web site.

TUNING AN ANTENNA

 

The most common way to check the tuning of your antenna is by a Standing Wave Ratio (SWR) measurement.

 

I have noticed for several years there may be some confusion of how to properly obtain this measurement from the modern radios.

 

Some of this confusion is due to not understanding what "Mode Of Transmission" means. This can be even more confusing when most of the radios are all mode units.

 

Most likely you have LSB, USB, AM, CW, FM and FSK or RTTY. Boy, that is a lot of modes. Which one do you use to check SWR?

 

Hopefully in future articles more details will be provided on each mode. However, for now, we just need the basics so you can use the radio effectively.

 

If your radio has a SWR meter built into it, then this will be the reading preferred. An outboard meter is fine, but the one in the radio is what the radio is going to use. If the SWR in the radio is high it will reduce your output power. Power reduction can easily be 50 to 90 percent. What is the best way to confirm this?

This is where knowing what mode to use is necessary.

 

USB and LSB modes do not produce RF energy unless you talk or make noise into the microphone. If you key the mic and all is quiet, there is no power out. I have had the humorous experience of operators saying the SWR is 1:1. However they were on USB or LSB and all was quiet. The meter reads nothing because there is no power out.

 

Many realize this. Their solution is to moan and groan or whistle into the mic. This will put power out, but it jumps around so much it is hard to get an accurate reading.

 

Some have put the radio in the CW mode. They key the mic and are happy to see a 1:1 SWR. However, they have not realized that their radio does not put power out on CW from the mic switch. A code key is needed for some radios.

 

Now there is the AM, FM and FSK modes.

 

AM is OK, but it does not put full power out. Initially you want to check SWR at low power anyway. The mic button will activate the radio. When you have your SWR acceptable, you will want to confirm that the radio will put the full power out. You can not do this on AM.

 

What about FM or FSK? Some have been hesitant to switch to these modes because they are not in the portion of the band it is allowed.

 

On FM, if you do not make any noise into the mic, it only produces a carrier. This is legal. On FSK or RTTY, it only produces a carrier. These are the easiest modes to use to check SWR.

 

Start at low power (5 watts). Using the internal SWR meter, check SWR and make the necessary adjustments to the antenna. Once acceptable, bring up the power. Use your "Relative Power Meter" in the radio. If you can get it to go full scale, you are ready to operate.

 

Your questions are welcome. I will try and answer them in future articles. Email me at wd0eja@isotronantennas.com.

 

73,

Ralph WD0EJA

SEPT 2021

 

Bilal Company

137 Manchester Dr.

Florissant, Co. 80816 U.S.A

PH/FX: 719/687-0650

wd0eja@isotronantennas.com

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