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Can Antenna problems damage a com transmitter?

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Mar 31, 2013 2:50 pm Post subject: Can Antenna problems damage a com transmitter?

At 11:28 AM 3/31/2013, you wrote:

 	  Quote: 	
		  



I intend to do some experimenting with homemade com antennas 

connected to my IC-A200.

Is there a danger of damaging the transmitter if the antenna is 

either open or short circuited or otherwise unsuitable?

Thanks,

Joe


	


   The very first solid state VHF transmitter I

   crossed paths with was indeed vulnerable to

   high SWR loading. But that was 1968 and

   the transistors were germanium PNP devices.



   A lot of improvements have been made over

   the years not only in the efficiency of transistors

   suited to the task but in their relative ruggedness

   as well. Nowadays, it is so easy to build a reflectometer

   right into a transceiver. The reflected power

   function is used to reduce drive to the transmitter's final

   amplifiers such that the transceiver is self protecting in

   extreme SWR situations (shorted or open coax).



   When using your transceiver for exploratory

   measurements, look at SWR first and excited

   the test setup for only long enough to see

   that your SWR readings are not really out of

   whack. The IC-A200 manual allows normal operations

   at SWR as high as 3:1 but is silent as to

   any cautions for still higher numbers.



   Open and shorted coaxes are part and parcel

   of living in the real world. Your transceiver

   is not at risk for the short duration measurements

   you're needing to accomplish.



   When ever we needed to make extended tests

   on a transmission line/antenna combo with

   high SWR, we would stick a 6 db attenuator

   in the line (100 feet of RG-58 coax works

   good too. The losses through the attenuator/coax

   are so great that TERRIBLE swr at the far end has

   no great effect on the energy source. The attenuator

   would keep the transmitter's auto-power down

   circuit happy.

   Bob . . .

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user9253

Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan

Posted: Mon Apr 01, 2013 4:31 am Post subject: Re: Can Antenna problems damage a com transmitter?

Thanks for the info, Bob.

I will proceed with caution.

Joe

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Joe Gores

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