SWR Question/Problem

[Lil'Yeshua]

My Sirio Performer PL5000 is tuned for a low swr at 27.285(home channel) in which if I go any lower in frequency the swr goes up. The Sirio also covers a good bit of 10 meters before the swr starts climbing sharply. Now that's good bandwidth .

 

[WhiteLightning73]

A quarter wavelength antenna typically refers to one that's close to a length of 234/F, where F is frequency in megahertz. That formula gives the length in feet. Use your favorite frequency for F

Most of the Wilson line have base or center loading coils which make the antenna a lot shorter than the full quarter wave (which may be good), but at the expense of having a narrower 2:1 SWR bandwidth (which may be bad).

The generally accepted quarter-wave antenna is a 102" SS whip with about a six inch spring. No loading coils, no goofy matching systems, just plug and play over whatever you come up with for usable range.

This 102" jobbie absolutely requires a lot of work on its installation and vehicle metal bonding.

Thanks for clearing that up. As far as the rest of this conversation goes, it's a little over my head.

 

[Captain Kilowatt]

My Sirio Performer PL5000 is tuned for a low swr at 27.285(home channel) in which if I go any lower in frequency the swr goes up. The Sirio also covers a good bit of 10 meters before the swr starts climbing sharply. Now that's good bandwidth .

Bandwidth is no indicator of efficiency however. The three parameters that can be varied in an antenna are, gain, SWR bandwidth and, front/back ratio in the case of a directional antenna. You can only optimize one at the expense of the other two so if the bandwidth is good then the gain is less than optimal as is the F/B ratio if it was a beam. really good high gain yagis have generally excellent F/B ratio as well but are narrow band.

 

[9C1Driver]

It's worth mentioning that every other market has enjoyed a nice increase in reliability as MOSFET technology has evolved. The latest devices can make a full kilowatt into a direct short without failing. Something that could even make an unprotected tube amp cringe. It's only CB'ers that have had to suffer from opening a brand new in the box 2950N2 or MOSFET linear to find it DOA or dead in a week. That's the price one pays when using a power supply transistor as an RF amp.

Good point.