Log-periodic Antenna Range

[keyholder]

Maikling tanong lang po. Gumawa po kasi kami this past week ng Log-periodic antenna composed of 5 elements in a driven array. Ang frequency specifications po nya is 174 to 698 MHz (starting from Channel 7 to 58), with design ratio (τ: 0.7) at relative angle (α: 30°). Pero nung tinest po namin siya sa isang LG TV, nasagap pa rin po nya ang channels 2 (ABS-CBN ay super linaw) at 5 (TV5 ay mejo malabo, pero clear sound).

Defense na po ng antenna namin bukas, at eto lang po talaga ang di ko ma-explain. May mali po ba sa design ko?

Actually last month, gumawa din kami ng 5-element Yagi-Uda antenna specified for channel 7 lang. Pero nasagap pa rin namin ng sobrang linaw ang channel 2 kahit ang layo na ng frequency nya. Ano po bang meron kay Channel 2, bakit laging malinaw?

[akhen]

ganon talaga... it doesnt mean kc na nakadesign sa channel  yung antenna mo e di na nya madedetect yung lower frequencies... even antennas design for channel 23 can receive channel 2s frequency... kahit nga sandok lang nakakasagap e... ganyan ang nagyayari pag malakas ang signal ng station sa lugar nyo...

[alyas]

maraming pwedeng pasukan yung signal, di lang duon sa antenna radiator, lalu na kung napakalakas na signal tulad ng ch. 2.  pwede dun sa coax cable or antenna wire or pwede sa tv mismo.

Yung tv ko nga kahit di naka-kabit sa cable or may naka-kabit na antenna, nasasagap pa rin ang ch. 2

[rdpzycho]

tama. 'yung dine-design na band, 'yun 'yung magiging malapit sa 1 to 1.5 ang VSWR at halos consistent ang radiation pattern, kung saan magiging pinaka-efficient ang reception. kung malakas ang signal, kahit mataas ang VSWR, makikita pa rin.

kung papansinin, 'yung cut ng Baron is designed lang for channel 2, pero dahil malakas ang signal sa paligid, nare-receive din halos lahat ng channels.

[keyholder]

Ayun! Mejo nagets ko na po. So pag-focus lang talaga sa SWR yung function ng band range sa antenna. Maraming salamat po mga boss sa replies.

Tama rin si ate Mystique, naalala ko, nabanggit din pala ng prof namin yun. Ngayon ko lang naalala.

(Sinubukan ko rin yung sandok... Hahaha...)
Actually kahit ung 3 centimeter na soldering lead ung pinasok ko, sobrang linaw ng Channels 2, 7 at 11. @___@

[rdpzycho]

^ kahit karayom lang, basta malakas ang signal makikita 'yan.

[keyholder]

Wow. Pede nga rin. @___@
Siguro ready na to bukas. Good luck samin. Thanks mga masters. ^^v

[keyholder]

^___________^
Just an update:
Super Thank you mga masters. Coz of your simple replies, nagkaconfidence kami para sa defense kanina para i-defend the antenna. We got a whooping of 98 percent for the overall project of the Log-periodic antenna!!! Felt really good lalo na nung pinasok ko yung 3 cm soldering lead sa TV kanina and showed a good output for a lot of channels. It was really new and unique for us all.

Again, kudos mga bossing! ^^v

[bravokilo]

@keyholder,late na ako pero I wish to give you some explanation.

Of course the LP you made is supposed to auto adjust to the freq it "sees"(directional kasi).Noted also, yung range nyo is way above  54-56mhz ng low band (ABS nga).

You should not have been surprised to have received Ch2 with clarity. You can only test your antenna if all the stations hve equal transmitting power and of igual distance from you. In other words "all things equal" was important to make a conclusion. If you were near the antenna of the weakest station, malinaw yun.

The other thing you must understand is that antennas are cut proportional to the wavelength of the frequency it is to receive. Half wave and  quarter wave ang popular. It means the same antenna can be a half wave and a quater wave antenna, di ba?

Ok, say you made a half wave antenna for 100 Mhz, that is a quarter wave antenna for 200Mhz. malinaw din ang 200Mhz! In the case of Ch2, since your LP was 160+Mhz up, medyo malayo sa 56Mhz nya bka sheer power lang talaga ang reaon why malinaw.

The Baron antenna, to my analysis is not designed for ABS' Ch2. It was designed for the higher frequencies. Ch 2 is in 6 meter(WL). A half wave dipole would be 3 meters long. At these lengths, malayo siya to pick up the higher frequencies. The other way around is better., For example, if we have a 1.5 meter antenna, that is a full wavelength for 200 Mhz, malapit sa Ch 7. Half wave yan for 400Mhz, di  ba? now, for Ch2, since 6 m ang full wave, 1.5 is quarterwave.

Hope this enlightens...


BK 0922 281 0680