Biquad TV antenna for UHF

[K_horse 2]

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

 

[clanon 258]

is a pcb antenna ?

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

[K_horse 2]

would be aluminium plate, with reflector

Edited March 29, 2021 by K_horse

[clanon 258]

 strip width...? thickness...?

[BurgHammer 1]

Strip width = (L1-L2)/2 = 31mm

[clanon 258]

[clanon 258]

the GAP is of most importance for impedance   

[clanon 258]

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

Gain is okay at High frecuency

[K_horse 2]

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

 

[clanon 258]

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

 

Edited March 31, 2021 by clanon

[K_horse 2]

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.

Edited April 2, 2021 by K_horse

[clanon 258]

BI QUADs for dTV

[K_horse 2]

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 April 2, 2021 by K_horse

[clanon 258]

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

 

[K_horse 2]

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?

[clanon 258]

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 April 3, 2021 by clanon

[vova.gumerov 23]

Klanon did you optimize this Biquad? If the 700-800MHz parameters are good, that would suit me. You need to accurately determine the dimensions. Internal clearance? Impedance? Preferably 75 ohm. Galvanized 0.5mm.

[Admin 2581]

VOVA, maybe you are interested in this ... !!!

 

Vova0,75.cst

[vova.gumerov 23]

Hello Jomy! I hope everything is fine with you. And we have a disaster ....... To make such antennas, you need a 3D cutter! Such things are not done with scissors and a grinder!

[Fred 2]

WIDE BAND COVERAGE!!! THE SHAPE OF THE ANTENNA LEADS TO BATWING SHAPE. 

[clanon 258]

On 17/11/2022 at 10:05 AM, vova.gumerov said:

Hello Jomy! I hope everything is fine with you. And we have a disaster ....... To make such antennas, you need a 3D cutter! Such things are not done with scissors and a grinder!

0.2 0.3 BRASS paper...? and a sharp cutter...several tries (using a printed PAPER taped on top) cut through the printed lines...?

solder the vertical strips...

PS: 0.2 is pretty RIGID...