Author Topic: Help pls.....regarding sa Impedance Matching (Read 1719 times)

Marui · « **on:** October 12, 2009, 11:17:10 AM »

Mga Master's tanong ko po regarding sa Impedance Matching.tama po ba ang computation ko?
nabasa ko po kc sa ARRL Book:

   wavelength= 300Mhz./frequency
kung ang frequency ko ay 60Mhz.:
   wavelength=300Mhz./60Mhz.
   wavelength=5 para sa fullwave Dipole
kung halfwave dipole ang gamitin ko 5/2 =2.5mtr.
   2.5mtr.=8.2021 ft.
  So ang maging Driven element ko po ay 8.2021 ft.
  Impedance computation:
   Kung gagamit po ako ng rg6 coax cable 75ohms tama po ba na gamitan ko sya ng 150/75 ohms matching x'former
Pakicorrect po kung may mistakes sa computations tnx.

Philippine Electronics Forum · « **on:** October 12, 2009, 11:17:10 AM »

zer0w1ng · « **Reply #1 on:** October 12, 2009, 02:03:06 PM »

1.25 meters each x 0.95 velocity factor = 1.19 meters per driven element (2x quarter wavelength).
The radiation resistance is 73 ohms for this kind of antenna.
Most radios have 50ohms output impedance thus you will have around 1.5 SWR if connected directly.

To have a max power transfer, you need proper matching from 73 to 50ohms.
The most common matching network for dipoles is the gamma match.

http://www.hamuniverse.com/n2kbk6meterantennas.html

Philippine Electronics Forum · « **Reply #1 on:** October 12, 2009, 02:03:06 PM »

rdpzycho · « **Reply #2 on:** October 12, 2009, 02:08:18 PM »

kung RG6, wala ng transformer, lagyan lang ng ferrite sleeve or ibuhol 'yung coax ng multiple turns para mabawasan 'yung common mode currents.

tama si sir zerowing, times 0.95 dahil sa velocity factor.

saan nga pala gagamitin 'yung 60MHz antenna? sa baba kasi ng frequency na 'yan, maliit lang ang bandwidth ng dipole. mataas na kaagad SWR sa paligid kahit matched 'yung 60MHz.

Philippine Electronics Forum · « **Reply #2 on:** October 12, 2009, 02:08:18 PM »

Marui · « **Reply #3 on:** October 12, 2009, 02:37:53 PM »

project po kc namin gumawa ng antenna low/high band ch.2 dapat masagap din po hanggang ch.13
pero dapat masagap din UHF.may nakikita ako mga design kso po mahahaba ang elements and boom ang pinapagawa kc samin ng prof.ko efficient but economical

Philippine Electronics Forum · « **Reply #3 on:** October 12, 2009, 02:37:53 PM »

rdpzycho · « **Reply #4 on:** October 12, 2009, 02:43:32 PM »

e sa Metro Manila kahit 'yung dipole lang marami ka ng masasagap dahil sa lakas ng transmitter powers. look at Baron antenna, siniksik sa isang dipole para sa lahat ng channels. hindi gaanong kaganda ang pattern niya, pero economical siya dahil ilang elements lang. but of course, hindi siya angkop sa lahat ng scenario, at dahil maliit ang directivity niya, maraming ghosts.

'yung mahahaba ang boom, considered kasi lahat ng channels and/or directivity.

Philippine Electronics Forum · « **Reply #4 on:** October 12, 2009, 02:43:32 PM »

Marui · « **Reply #5 on:** October 12, 2009, 03:02:20 PM »

Ibig ba sabihin sir kailangan pala talaga ang mahaba na boom para makakuha ng good reception?

Marui · « **Reply #6 on:** October 12, 2009, 03:37:41 PM »

Sir pogi pts. sa inyo sir Zer0w1ng at sir pzycho mga instructors po b kau?Tumatanggap po ba kau ng tutorials?hehe

zer0w1ng · « **Reply #7 on:** October 12, 2009, 03:59:59 PM »

Quote from: Marui on October 12, 2009, 03:37:41 PM

Sir pogi pts. sa inyo sir Zer0w1ng at sir pzycho mga instructors po b kau?Tumatanggap po ba kau ng tutorials?hehe

Hindi pa ako instructor.

For tutorials, just post your questions or needs in this forum. I am sure many will give answers and help.

Marui · « **Reply #8 on:** October 19, 2009, 10:14:12 AM »

Mga sir,
Tanong ko po pano ang pagcompute ng distance ng elements sa boom kung magdadag pa ng elements or directors pano din ang pagcompute sa impedance tnx.

rdpzycho · « **Reply #9 on:** October 19, 2009, 11:28:15 AM »

check mo sa mga antenna sites. 'yung impedance calculation is higly mathematical. 'yung additional elements (passive), by trial and error nila ginawa dati. I suggest you learn NEC kung gusto mag-simulate ng iba-ibang antenna configuration.

Marui · « **Reply #10 on:** October 19, 2009, 03:58:13 PM »

Sir un nga po sana gusto ko matutunan pano po b paggamit nun at san inaapply?tnx,.

rdpzycho · « **Reply #11 on:** October 19, 2009, 04:32:31 PM »

try to look for 4nec2x. madali lang naman siya gamitin. lalagay mo lang 'yung wires (elements) then connections. to keep it simple pwedeng 'di ilagay 'yung boom (ideal ang simulation). may mini-tutorial na kasama 'yun.

ginagamit siya to simulate antennas using NEC (Numerical Electromagnetics Code).

http://www.df9cy.de/tech-mat/wi432-10/wi432-10.htm

looking at his simulation, disregarded 'yung boom at 'yung tower. in real life, may effects sila, but at least you get the picture of what you're trying to do.

merong ibang gumagawa ng simulations, to keep it as close as possible to actual results, sinasama pati 'yung dimensions ng bubong na paglalagyan (they can act as reflectors). medyo overkill nga lang at time consuming sa paggawa ng model.

Marui · « **Reply #12 on:** October 20, 2009, 09:29:14 AM »

Ang lupit mo talaga sir RF engr. kb? 10pogi pts. sir!!!!

rdpzycho · « **Reply #13 on:** October 20, 2009, 09:58:57 AM »

nope. depende sa kailangan ng client 'yung ginagawa ko. pero interesting naman lahat para sa akin 'yung mga aspects at subparts ng electronics kaya ok lang.

Ka irnie · « **Reply #14 on:** October 20, 2009, 02:05:22 PM »

Philippine Electronics Forum · « **Reply #14 on:** October 20, 2009, 02:05:22 PM »

Author Topic: Help pls.....regarding sa Impedance Matching (Read 1719 times)

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