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K_horse

Biquad TV antenna for UHF

Hello there, I'm making Biquad antenna for UHF TV in North of england, the winter hill transmitter, uses channels 29-55 or frequency range 538 to 754Mhz. Distance is about 30 kilometers, 100kW, and antenna will be used indoors.

I haven't made it yet, but I drew it using measurements from online calculators, with smallest and biggest channel together, + a little extra (Channel numbers move a lot). Can someone look at it, make sure it is correct?

What would impedance be? I have a lot of 300 to 75 ohm balun, if it needs one.

thanks

 

check.png

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is a pcb antenna ?

An all wire or metal sheet (NO DIELECTRICS) would ALWAYS be better...

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Posted (edited)

would be aluminium plate, with reflector

Edited by K_horse

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 strip width...? thickness...?

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the GAP is of most importance for impedance   

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Impedance , vswr an S11 is wrong...so far

Gain is okay at High frecuency

Captura.JPG

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Thanks for simulation, what program is that?

outside gap between squares is 36mm, at that place strip is 20mm wide, otherwise 31mm

I don't know how to calculate impedance. Want to try and get 300ohms, because I have a lot of 300-75 ohm baluns

 

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Posted (edited)

CST MWS...

as it is (5cm to reflector)...is NOT GOOD 

this gets better at 7 cms 

CENTERED at 600 mhz the best results

impedance as it is is close to 50 ohms (Around)

it could be tunned to 75 ohms

 

vswr.JPG

s11.JPG

z.JPG

Edited by clanon

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Posted (edited)

I have that software now, i'll learn to use it.

Seeing that the impedance is 50 ohms makes me wonder about another antenna I made, this one for broadcasting, specifically channel 23 (487Mhz). I don't know what it's impedance is. Most biquads I see people make are 2.4Ghz ones with direct connection to coax, don't know how everything changes when whole antenna is nearly 90cm wide.

dual biquad.png

Edited by K_horse
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Posted (edited)

Yes I've seen that thread before, it has a ready made design from the admin which works well for reception. But it does not explain anything or answer my questions.

double biquad is for sending, not reception, i want to know its impedance so that I can broadcast with best pattern. I can't have power lost from a radiating coax.

Edited by K_horse

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Impedance on any antenna could be tailored to any need...(with some compromises)

 

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That is true, but I do not know how. Nor do I know how to determine what the impedance of an antenna currently is.

This information is kept secret?

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Posted (edited)

metal THICKNESS and DISTANCES...that's all 

of course SHAPES  are of the utmost importance ...

every time you PUT a discrete port between two metals on ANY PLACE ...CST would tell you the impedance THERE...

Edited by clanon

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