[SI-LIST] Re: High frequency transmission

Kirti Barpande wrote:

>Hello! Experts,
>I want to transmit a 500 MHz sinusoidal signal, 2 to 3 volts peak to peak 
>over 300 metres long coaxial cable. Can it be successfully done with minimum 
>loss using coaxial cable? Which cable will be more suitable? I Plan to use 
>RG-8 cable.
>Kirti
>
>
>  
>
RG-8 (Belden 9913) has a loss of 3.02 dB/100 feet at 500 MHz
RG-8 (Belden 8237) has a loss of 4.8 dB/100 feet at 500 MHz


For a matched cable 300 meters long you will have the following losses:

Belden 9913:     -29.75 dB  or  a voltage ratio of .0316
Belden 8237:    - 47.27 dB  or  a voltage ratio of .0043

Since dB=20log (V1/V2)


   So your output voltage will be about (3*.0316) 0.048 volts for 9913 cable
or (3*.0043) 0.0129 volts for 8237 cable.

Exotic rigid heliax like Andrew LDF6-50A would give you about 9.57 dB loss
or abour .94 volts at the end of your cable (at a cost of many $$$$/meter)

Bottom line: 500 MHz over 300 meters of coax can't be done with low loss!
(at least with commonly available cables)

Ray Anderson   WB6TPU
Staff SI Engineer
Sun Microsystems

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