Antenna for 800 MHz Police scanner

kirkman123

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I do most of my scanning listening to 800 MHz on my SDS200 Uniden scanner. For an outside antenna which is probably better, the Tram 1410 or the Tram 1411 for listing to 800 MHz ?
 

vagrant

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Neither of those antennas are better or good for 800 MHz. See this thread regarding an antenna for 800 MHz and why it is improved over a typical discone.


I do most of my scanning listening to 800 MHz on my SDS200 Uniden scanner. For an outside antenna which is probably better, the Tram 1410 or the Tram 1411 for listing to 800 MHz ?
 

jonwienke

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Those discones can work fine on 800MHz if you cut all the radials in half to retune it to the higher frequency band.
 

Ubbe

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Most discone designes are for some reason optimized to the 90-100MHz band, with the lower elements having a lenght of 35 inch or longer and diameter of the horisontal elements 25 inch tip to tip. Reduce all elements to 75% to still receive max at the VHF airband. Airplanes are usually received at line of sight with any sort of antenna so that could probably also be sacrified and then use the suggested cut all lenghts to half method to still receive max at mil air frequencies. If only 400MHz and above are needed then cut down to 1/4 lenght of the original size to really optimize the 700-900MHz reception.

You can use the calculator at: VE3SQB Antenna calculators

/Ubbe
 

Marauder

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Most discone designes are for some reason optimized to the 90-100MHz band, with the lower elements having a lenght of 35 inch or longer and diameter of the horisontal elements 25 inch tip to tip. Reduce all elements to 75% to still receive max at the VHF airband. Airplanes are usually received at line of sight with any sort of antenna so that could probably also be sacrified and then use the suggested cut all lenghts to half method to still receive max at mil air frequencies. If only 400MHz and above are needed then cut down to 1/4 lenght of the original size to really optimize the 700-900MHz reception.

You can use the calculator at: VE3SQB Antenna calculators

/Ubbe
So if I want my tram 1411 to work better on 800mhz / P25 , Literally cut the whip in half ?
That would answer whether or not I should get it or something tuned from factory to 800 band
 

Ubbe

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You can see the diagram here how a discone works at different frequency bands. It's 10dB loss at 900Mhz from signals at the horizon. Cut the discone to half size and it will look like the 450Mhz diagram. Cut it even smaller and it will look more like the 145Mhz diagram in the 900MHz band. But remember that the best reception at lowest frequency will be raised by that scaling factor, 4 times means that 90Mhz are now 360Mhz as the lowest usuable frequency, without any extra loss. It will still receive at the lower frequencies, like a 1/4 wave GP antenna for 145Mhz will still receive the 118MHz airband with some loss compared to the optimum tuned frequency.





/Ubbe
 
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