antena pentru zapp - 450 Mhz

[joe]

salut! nu prea stiu multe in radio, de aia va rog sa ma ajutati si pe mine cu antena pentru receptie zapp, sau eventual un amplificator pt aceasta banda.multumesc.

[Vizitator kellooz]

Simple UHF Yagi Antennas for under $5A simple afternoon project by Dan Buchanan, KF4LNEThis paper was created to help the many 460MHz and 800MHz scanner lsiteners who want toimprove the quality of reception of the signals they hear. In the world of public safetycommunications most 460MHz and above operation involves the use of a repeater. Repeatersare usually located on the same site as other repeaters such as fire and rescue, police andcounty agencies as well as many amateur radio and other private repeater systems such asGMRS and business systems. When you listen to these agencies you aren't listening directly tothe unit you are hearing but to repeater that enhances that units radio coverage area. Thisdocument explains how to construct light weight directional antennas for the bands many of usare monitoring.450MHz Yagi constructed using inexspensive materials from Wal-MartBefore you begin this project you should know the locations of repeater sites in your area. Letsget started.Materials:All materials can be found at Wal-Mart. You may also find these materials at craft and hobbyshops as well.? 10 pack of wire clothes hangers? 1 36 inch wooden dowel rod, minium 5/8 inch diameter.? Epoxy or hot glue sticks and gun or other suitable adhesive? outdoor spray paint in a color you like, I used automotive primerTools? Heavy wire cutters? Drill and bits for the size wire used? clamps suitable for clamping the dowel to a work surface? File suitable for filing the sharp ends from the cut elements (Optional)Measurements: (In Centimeters)Freq Ref Driven Dir 1 Dir 2 Dir 3 Dir 4 Dir 5/6450LengthSpace32.58 32 30.05 29.856 28.786 28.640 X0 17.64 11.618 12.429 16.157 15.009 X460Length 31.870 31.300 29.397 29.207 28.160 28.017 XSpace 0 17.255 11.365 12.158 15.806 14.683 X850Length 17.1 16.8 15.77 15.672 15.110 15.034 14.651Space 0 9.34 6.1507 6.5801 8.5539 7.9464 8.8070940Length 15.464 15.187 14.264 14.171 13.663 13.594 13.248Space 0 8.4443 5.5618 5.9500 7.7349 7.1856 7.9638450 and 460MHz antennas are only 6 elements due to the available boom length.Instructions: (Read these FIRST!)Gather all of your materials and tools first. Clamp your dowel to a suitable work surface thatyou can use to drill holes. Mark the location of each element on the boom and drill the holes asstrait and centered as you are able. If you have access to it a drill press is useful for this, if notyou may want to brace your drill against something to hold it strait. Measurements for theelement holes are measured from the previous element starting with the reflector. Drill yourreflector hole about 15 cm from the end of the boom to allow for mounting hardware. You willneed at least 75 cm of length to mount all the elements using these measurements. When youdrill the hole for the driven element be sure to drill two (2) holes for each half of the elementspaced about a half cm apart along the boom. Please read the detailed instructions aboutbuilding the driven element. When you cut your elements be sure to file the sharp ends off oryou may get seriously injured when working on the antenna. Do not yet cut the driven element,read the detailed instructions first. You can start mounting the elements to the boom. Be sureto center the elements wen you mount them or your antenna will look bad and may not performwell. Once you have installed all of the elements, including the driven element you shouldsecure these elements using your adhesive. I suggest hi-temp hot glue or quick-set epoxy. Onceit is completed apply several coats of paint to protect the materials.Driven Element Details:Your driven element is nothing more than a center fed half wave dipole. If you have it available#10 solid bare copper works great for this, otherwise you can use the clothes hanger wire. Tomake this element you need to cut two (2) quarter wave elements. These elements will be ?the length listed in the measurement table PLUS an additional length to accomadate mounting.For example, if you build the 450MHz antenna using a 2cm thick boom you would cut yourelements 17cm each plus the additional 2cm to mount to the boom making each quarter waveelement 19cm long. You should have drilled two (2) holes for the driven element, one for eachleg of the dipole. Mount these elements to the boom on oppisite sides to create the half wavedipole. Secure using your adhesive of choice. Once all of your elements have been sucured andthe adhesive has cured you can attach your coax. To do this you will need to attach the centerconductor to one leg of the driven element and the shield to the other. Be sure to remove anyrubber coatings on your elements to allow for electrical connections. You can coat theconnections with epoxy to secure them or if you used copper wire for the elements you cansolder the coax to the elements. Be sure to seal the open end of the coax to keep water out.Installation and Use:There are many ways to mount this antenna, however a simple mount can be made usingradiator hose clamps. To do this you will need a hose clamp small enough to tighten aroundyour antenna boom and another large enough to fit the mast. Secure the large clamp to theboom using the small clamp and tighten the large clamp to your mast. Be sure to leave accessto the clamp screws so you can adjust the polorization and direction of the antenna. If you planto use this antenna for typical UHF/800MHz scanner listening you will want to install it withvertical polorization and point it at the location of the transmitter you want to monitor. Not allsignals will come directly from the location you are pointed and you may have to point theantenna in another direction to receive a signal reflected off of a large building or mountain.This is the part you will have to tinker with to get the best reception. I hope this document ishelpful and informative. Enjoy!Other low cost antenna projects:? Simple Portable VHF Endfed Halfwave? Multiband SWL Wire Antennas? Simple VHF 3 Element Yagi? Portable Multi-Band Scanner Antenna? 2.4GHz WiFi Passive Repeaters? 2006 Dan Buchanan,KF4LNEThis document cannot be reprinted in part or whole for commercial use without express written permission from theauthor. This document can be distributed freely in unaltered form on internet websites related to radio scanning,amateur radio and other radio hobbys. This document is publically available and is not to be sold, leased or any feecharged for the access of this document. This document must not be distributed in a ?paid subscription? area of anyweb or FTP site. This document may be zipped or archived for distribution as needed provided the content of thedocument is not altered an any way.

[Vizitator kellooz]

Nu sunt nici eu vreun cunoscator, dar sper sa te ajute cumva. Chestia asta am gasit-o pe net, dar nu am incercat-o. Cand o sa am putin timp o sa incerc sa vad daca este buna schema si o sa te anunt(asta daca nu cumva mi-o iei inainte)

[Vizitator]

Nu era mai simplu asa:

 

http://forums.radioreference.com/attach ... tennas.pdf

 

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