How Much Does It Take To Burn Out A Radio?

[ND999]

So, I installed a switch to be able to swap between two radios on one antenna. Then, I proceeded to immediately do a bonehead move! I was going to check SWR on one radio.......wait for it....... while I had the switch in the position for the other radio! So, I technically transmitted for a few seconds on a radio with no antenna. What is the likelihood that I did any damage? How would I know? Once I had switch in correct positions, SWR was good for both radios. And the meter also has capability of showing output power. Both check fine there too. Am I still OK? Thanks!

 

[walterjn]

I'd say you'll be fine. Pretty sure it takes more than a few minutes keyed up with no antenna to do any real damage.
If I'm wrong, one of the more experienced guys here will set us straight.

 

[FlatlandBusa]

You are likely ok. Most radios and amplifiers will tolerate very high SWR briefly if they aren't driven within an inch of their life already.

 

[Shadetree Mechanic]

If power and swr still check fine, then I would say that your radio is ok. I have a big MFJ switch and have done the same thing. I now only turn on the radio that I am using.

I plugged the wrong microphone in an old Midland one time. I didn't realize that the meter was pegged, because the wrong microphone keyed the radio. By the time I realized what was happening, it was too late. Ruined a good old radio for no reason.

 

[ND999]

If power and swr still check fine, then I would say that your radio is ok. I have a big MFJ switch and have done the same thing. I now only turn on the radio that I am using.

I plugged the wrong microphone in an old Midland one time. I didn't realize that the meter was pegged, because the wrong microphone keyed the radio. By the time I realized what was happening, it was too late. Ruined a good old radio for no reason.

I will probably do the same as far as only turning on one I'm using. I've even considered making some sort of cover for the mic of whichever is not connected to antenna. It's either that or just not be in such a hurry and pay attention to what I am doing!

 

[Shadetree Mechanic]

When I was getting in the routine of unplugging my coax when not in use, I put a clothes pin on the microphone cord. That would remind me that the coax was unplugged. Then I plugged in the coax and put the clothes pin on it to remind me to put the pin on the mic when I disconnect.

 

[ND999]

When I was getting in the routine of unplugging my coax when not in use, I put a clothes pin on the microphone cord. That would remind me that the coax was unplugged. Then I plugged in the coax and put the clothes pin on it to remind me to put the pin on the mic when I disconnect.

That is also a good idea which I might consider. Thanks!

 

[nomadradio]

In the city, the noise level is usually enough to notice. More to the point, a lack of that noise level should be easy to notice. Told customers to treat that noise level like the "dial tone" on their landline phones. Until you hear it, no point in making a call. Won't go through without the dial tone.

73

 

[9C1Driver]

Lou Franklin wrote an article many years ago where he tell a story about this. He would have lunch with a cb friend and to prove a point he would un-hook his coax and then put a rubber band on the mic keeping it keyed. When they finished lunch he would plug the coax back in and the radio would work fine. This was obviously long before mosfet finals.

 

[brandon7861]

I do it all the time. My coax switch and tuner coax switch both short the unused port and I've keyed down good several times with both set wrong. For storms, I have a jumper cable clamp that I attach above my loading coil so lightning dont shred my coil and I've keyed into that countless times. Even a mosfet that isn't biased into self-destruction can take some abuse.

 

[ND999]

I do it all the time. My coax switch and tuner coax switch both short the unused port and I've keyed down good several times with both set wrong. For storms, I have a jumper cable clamp that I attach above my loading coil so lightning dont shred my coil and I've keyed into that countless times. Even a mosfet that isn't biased into self-destruction can take some abuse.

I'm glad you mentioned that it shorts the unused port. I noticed this while testing continuity with multimeter and wondered if it was normal. So, you answered that question for me. Thanks

 

[brandon7861]

I'm glad you mentioned that it shorts the unused port. I noticed this while testing continuity with multimeter and wondered if it was normal. So, you answered that question for me. Thanks

I guess its worth adding then that if the switch fails to short the unused terminal, the isolation between ports will drop. When transmitting through one side of the switch, the signal that appears on the shorted port is around 60dB down into a 50Ω load. If the switch fails to short the unused port, the isolation is only around 30dB. That can make the difference between smoking a receiver or not. My switch is a bit sketchy when shorting the unused port now and I think it is because the casted housing the contact pushes into when shorting can oxidize.

I use mine as a 60dB attenuator for doing s-meter adjustments and checking receive sensitivity because I am too cheap to buy two more 30dB attenuators or a good sig gen. If I want a specific signal strength, I need to cobble together junk and use my SA to know what my signal level is. Its a real PITA.