Ok here is a good one. A post in another forum. Guy is running a 980 and a K30 magnet mount antenna. His VSWR is 1.75:1. He also is having trouble understanding why the radio will put out more power at the resonant point of the antenna and not at across the entire 40 channels. I did some explaining. This included that he should be careful about using the radio with a VSWR of 1.75:1 due to the MOSFET being used in the radio. Well I got flamed by some guy that says he worked for a major CB company or something, and told me that I was wrong to tell the poster to watch it with a VSWR of 1.75:1 with his uniden 980. He told me he has keyed up countless CB radios with Bipolar trsnsistors with bad VSWR and they didn't blow. Actually I'll copy the post. Am I the one in the wrong here or is he full of it?? Please let me know as if this is the case. Why the heck do CB Mosfets have such issues with bad mismatch and VSWR. And I wasn't speaking about HF RADIOS either!! I made this clear.
Here is the post.
Uniden 980 SSB Watts Lower on Higher Channels?
At one time I worked for the largest CB mfr in the world and had my hands inside more CBs than most people. I can tell you the final RF transistors in any CB made since the early 1970s through today are purpose designed and made for CB service. They may be found in a few other radios but they were all made with CB in mind because its the largest customer for the product. Mosfets are relatively new to the CB market with plain old bipolar devices being the most prevalent.
I've also tried to destroy countless CBs over the years by disconnecting the antenna and transmitting for long periods of time. I was never able to hurt one and that includes the cheapest bottom of the line and some high end radios. Even today I will take any of the CBs laying around here and will transmit with no antenna all day long to make a point and I'm confident nothing bad will happen to it. With that said I don't think a 1.75:1 VSWR will hurt any radio.
[quote name="222DBFL" post=2622711]You can't measure power correctly with an antenna. You need a 50 ohm dummy load and a decent VSWR meter. The meter you have now is not very good. I would venture to say if you place it on a dummy load it will read the same power across the 40 channels. JMO. Also how are you checking the output on SSB? Hopefully with a 1000hz sine wave tone. Your phone should have an app for this. But like I said, using the antenna to perform this won't work correctly. And also a 1.75:1 VSWR is going to end up blowing that final at some point. The finals used in most if not all CB radios are not true RF type Mosfets. They can be made to work, but aren't truly made for that purpose. Now an HF or ham radio does use RF type Mosfets for the PA. And the K30 is a POS antenna. Sorry not trying to be rude, but a 3ft antenna is about like placing a coat hanger on a magnet mount. The bandwidth is very narrow and they usually don't tune very well. Just my experience with these type of antennas. Get an antenna that is at least 6ft or longer. You'll notice a big difference in your RX and TX distance and most likely a better match or VSWR reading. Remember that all these antennas will tune to only 1 frequency at resonance. You might see a good VSWR on channels 1 and 20, but there is more to antennas and how they work then just VSWR.
is totally correct with what he stated as well. Get rid of the truck stop VSWR (SWR) meter and find a better one. Diawa makes a good meter, or even find a radio shack meter off eBay or check around at your local radio shack, some still carry the VSWR/watt meters.
Do some research on how mono band antennas work. Also the connector that is on the end of that mag mount you have is a problem area as well. If it's the 2 piece sma to PL259 adapter. They are a known failure point. But IMO, with the VSWR as high as it is (1.75:1), your radio isn't going to last very long. Those finals are already a known weak point and don't like VSWR above 1.3:1. They create a lot of heat and will show you readings just like what you are seeing. Again, these are just my experiences with antennas using an antenna analyzer. Like I said, read up some about your antenna (k30 magnet mount), and you'll find that what you are experiencing is quite normal for these type antennas. Hope this helps and don't get discouraged. It's not your radio. JMHO's. And again, hope this helps. Have a good day sir.
