SWR Question/Problem

[WhiteLightning73]

I'm pretty new to the hobby but I've always had an interest in radio, so be gentle.
I've got a Galaxy 99v2, a Texas Star DX 350, a Wilson 1000 mag mount, and I'm using a Astatic PDC1 SWR/Watt meter to check my SWRs. Ok, on band E channels 1-40 for example, I get an SWR of 1.0-1.1 on both the Astatic and the radios meter, so those both jive with each other. But on Band H channels 1-40, I get SWRs between 2.0 and 2.5 area. What's happening here? Do I need to retune my antenna for each band or what? I know an SWR above1.3 is not good for my amp. Any help would be much appreciated.

 

[C2]

yes. the antenna is not broadbanded enough to cover that frequency range.

 

[WhiteLightning73]

I'm not sure I understand. According to Wilson's website, the specs say that the "Frequency Range 26MHz to 30MHz". That falls between that range.

 

[C2]

yes. I'm sure your radio covers that range too, but needs some adjustment to do so (such as turning the channel selector).

The antenna can be tuned over that range, but that is not an SWR bandwidth spec, it is merely an operating spec. You can make it work over that entire range, but just not all at once. You will need to tune the whip to move the operational bandwidth over the range that you want to operate.

 

[Mudfoot]

The antenna itself can cover that range, but only by adjusting the length of the stinger in the coil base, or cutting the stinger and adjusting it as well.

I operate 10/11 meter mobile frequently and use a Wilson 1000. I'm able to adjust my stinger length so that it is bottomed out in the base. I have a second stinger that is cut for 10 meter phone and bottoms out as well. All I have to do is just quickly change stingers without worrying about readjusting it within the base.

When I operate 10 meter CW, I can use the 11 meter stinger without VSWR issues since it's at the bottom band edge.

That's just how I roll. I have used an antenna coupler before, but really don't like to.

 

[WhiteLightning73]

yes. I'm sure your radio covers that range too, but needs some adjustment to do so (such as turning the channel selector).

The antenna can be tuned over that range, but that is not an SWR bandwidth spec, it is merely an operating spec. You can make it work over that entire range, but just not all at once. You will need to tune the whip to move the operational bandwidth over the range that you want to operate.

That's a very good explaination! I actually understand it now. But it does kinda bite that I I can't just change bands without having to stop the car and retune the radio to the antenna.

M42duster: I follow you, and that's a great tip! Thanks to you both!

 

[9C1Driver]

It's a bummer but that's the way it has always been. If you tune a mobile antenna to say cb channel 20 you will have about 60-70 channels in either direction to use before your SWR will be too hi to key up. Even worse with with these new mosfet radio's that don't tolerate higher SWR levels.

 

[W5LZ]

Are you ready for some 'nit picking'?
"...without having to stop the car and retune the radio to the antenna."
That's exactly backwards. You don't retune the radio -to- the antenna, you are retuning the antenna to something closer to the radio (or what the radio will be happy with). It really does make a difference in how you think about this...
- 'Doc

 

[Captain Kilowatt]

That's what I always liked about running a 1/4 wave whip. Nice W I D E bandwidth.

 

[WhiteLightning73]

That's what I always liked about running a 1/4 wave whip. Nice W I D E bandwidth.

I take it the Wilson isn't a 1/4 wave whip?? Can you give me an example what is a 1/4 wave and the benefits over what I've got?!

 

[Beetle]

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.

 

[Shockwave]

Even worse with with these new mosfet radio's that don't tolerate higher SWR levels.

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.

 

[Captain Kilowatt]

I take it the Wilson isn't a 1/4 wave whip?? Can you give me an example what is a 1/4 wave and the benefits over what I've got?!

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.

What he said. ↑↑↑↑↑↑↑↑↑↑↑↑↑

 

[Captain Kilowatt]

Even worse with with these new mosfet radio's that don't tolerate higher SWR levels.

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.

I have to agree with Shockwave 100%. The only MOSFET radios that seem to have a poor SWR tolerance and higher than normal failure rate are CB radios. Commercial and amateur radios have been using them flawlessly for decades.....yes DECADES. I first encountered MOSFETS in 100% commercial broadcast duty in 1982 with a Nautel AMFET-1 commercial AM broadcast transmitter. The only time we had a problem with the MOSFETS was during a lightning strike and that could hardly be blamed on the device itself. Freescale has developed a MOSFET that will produce 1.2 Kw into an infinite SWR from a dead short to an open circuit. The MOSFETS used in CB radios are cheap power supply switching types that were NEVER intended to operate as an RF amplifier. The best thing CBer's could ever do is refuse to buy these radios and let the manufacturers know the reason why. There is no excuse for people to be screwed over by the manufacturers in an effort to save a couple dollars on a radio costing a couple hundred dollars. The issue is not the device type as much as it is the device selection used that is causing the problem with the new CB radios.Stand up and let the manufacturers know that you want the same quality that every other radio user has.

 

[Shockwave]

The best thing CBer's could ever do is refuse to buy these radios and let the manufacturers know the reason why. There is no excuse for people to be screwed over by the manufacturers in an effort to save a couple dollars on a radio costing a couple hundred dollars. The issue is not the device type as much as it is the device selection used that is causing the problem with the new CB radios.Stand up and let the manufacturers know that you want the same quality that every other radio user has.

Now the nail has been struck right on the head. We absolutely need to become more educated as consumers and stop buying the crap they are stuffing into today's CB final stages. It's probably the most unreliable application I've ever seen a transistor repetitively misused in. Some may have noticed I'm very critical of these MOSFET's but the criticism has been well earned by the high failure rates and marketing that keeps plugging the use of this junk.

Haven't we noticed every time a high demand part goes out of production, China is right there to pretend they have a suitable replacement? Without them, who could we thank for counterfeit 2879's that work like a MRF-454, 3-500Z's that last a year if you're lucky and finals for our output stages that are ready to blow up before the first transmission? You can wrap sh*t up in fancy paper and a bow but it's still sh*t and smells like it too.