Cobra 25 Ltd strange issue

If you change radios then you might have to change antennas to either resize them to fit or the coax is too long or short. It apparently likes your radio without problems but gags on the other.

 

Sounds to me like there is a problem with the power output with the cobra 25 radio, since you can’t get your external swr meter to calibrate.

 

Bear, just wondering with the connex radio, what was the swr reading for your antenna?

 

I also wonder, a very stupid question. Call me a dunce for this one but SWR wants to be all the way left and barely twitching when I hollar with my big mouf right?

What DOES it take to get the #### thing all the way over?

 

For the most part that is correct. Although you really don't need an swr of 1.1 like most people think. For example, most 1/4 wave mobile antennas are around 25 to 36 ohms impedance (from what I understand), so with a 50 ohm radio, and an antenna at 36 ohms impedance, your swr should be around 1.4 for swr. That's according to the math on paper... 50/36 = 1.38.

As far as your 2nd question, I assume you are referring to the swr needle? Are you referring to the calibration of the swr meter? Sorry I'm confused.

 

You got me thinking about this, so I did a quick experiment. I have 2 older swr meters. One is an Olson brand, and the other meter is an Ultratec. Using my Galaxy 959 radio, I can very the RF output power from 1 watt to 4 watts. It took about 3.5 watts for the Ultratec meter to reach the calibration/set point on the meter. I was able to calibrate the Olson swr/power meter with just 1 watt from the radio. I'm not sure what meter you have, but this reminded me that some meters have to have more output power from the radio to work than others. Sounds like this maybe the case for you, since the connex radio puts out more RF power than the Cobra 25. Great question.

 

I understand calibration to allow the radio to know how much antenna it is on. Maybe Im the wrong one with that thought. IF anything is not enough or too "Dirty" your signal will likely be bad going out and almost impossible coming in.

I have had a number of very basic cobras that sold for like 50 dollars and had maybe a channel dial and a power dial and that's it. Nothing to adjust. hissing static all day. The Uniden was a game changer with that SWR.

 

I suggest testing radios and their features on a "Dummy Load" rated at twice the output of the equipment being tested. Example, 50 watt radio, 100 watt dummy load.. For testing radios and Amps, this dummy load would work great, click on Parts and Accessories ...

 

If you're getting different readings with different radios the SWR never changed so obviously you can't trust what the radio is telling you.
It would be worthwhile to have somebody with an antenna analyzer check your antenna system.