Category Archives: Antenna

The U.S. Nation­al Sci­ence Foun­da­tion is accept­ing pro­pos­als from any­one who wants to take over oper­a­tions.

By Asso­ci­at­ed Press and Dan­i­ca Coto
Jan 25, 2017 

The future of one of the world’s largest sin­gle-dish radio tele­scopes is in ques­tion after the U.S. Nation­al Sci­ence Foun­da­tion announced Wednes­day it was accept­ing pro­pos­als from those inter­est­ed in assum­ing oper­a­tions at the Areci­bo Obser­va­to­ry in Puer­to Rico.

The announce­ment comes as the fed­er­al agency runs out of funds to sup­port the obser­va­to­ry, which fea­tures a 1,000-foot-wide (305-meter-wide) dish used in part to search for grav­i­ta­tion­al waves and track aster­oids that might be on a col­li­sion course with Earth.
Offi­cials with the foun­da­tion stressed in an inter­view Wednes­day with The Asso­ci­at­ed Press that the agency prefers that the obser­va­to­ry remain open with the help of col­lab­o­ra­tors that would pro­vide a fund­ing boost.

Our (com­mu­ni­ty reviews) have rec­og­nized that Areci­bo does great sci­ence and will con­tin­ue to do great sci­ence,” said Ralph Gaume, act­ing divi­sion direc­tor for the foun­da­tion’s Divi­sion of Astro­nom­i­cal Sci­ences.

How­ev­er, he warned it’s pos­si­ble none of the pro­pos­als that have to be sub­mit­ted by late April will be cho­sen. This would leave the foun­da­tion with alter­na­tives includ­ing sus­pend­ing oper­a­tions at the obser­va­to­ry, turn­ing it into an edu­ca­tion­al cen­ter or shut­ting it down.

The first hint that the 53-year-old obser­va­to­ry was at risk came a decade ago, when a pan­el of experts rec­om­mend­ed it be shut down unless oth­er insti­tu­tions could help the foun­da­tion. The agency finances two-thirds of the obser­va­to­ry’s $12 mil­lion annu­al bud­get, and offi­cials said it could pro­vide some $20 mil­lion over a five-year peri­od to a poten­tial new oper­a­tor.

Sci­en­tists use the obser­va­to­ry in part to detect radio emis­sions emit­ted by objects includ­ing stars and galax­ies, and it has been fea­tured in the Jodie Fos­ter film “Con­tact” and the James Bond movie “Gold­en­Eye.” It attracts about 90,000 vis­i­tors and some 200 sci­en­tists a year that use the obser­va­to­ry for free to do research, said obser­va­to­ry direc­tor Fran­cis­co Cor­do­va.

How­ev­er, he told the AP that could change depend­ing on the type of pro­pos­als sub­mit­ted.

Per­haps in the future, sci­en­tists might have to pay to use it,” he said, adding that the obser­va­to­ry still plays a key role in research includ­ing the study of solar erup­tions capa­ble of dis­rupt­ing elec­tron­ic equip­ment.

The obser­va­to­ry has been threat­ened in recent years by big­ger, more pow­er­ful tele­scopes in places like Chile and Chi­na, where offi­cials recent­ly unveiled the Five-hun­dred-meter Aper­ture Spher­i­cal Tele­scope, or FAST.

The foun­da­tion said it expects to make a deci­sion by late 2017 as it awaits com­ple­tion of a final envi­ron­men­tal impact state­ment, which will out­line all alter­na­tives for the obser­va­to­ry’s future.


Category: Antenna

 

One of the most crit­i­cal parts of a ham radio set­up is the anten­na. You can have the most expen­sive and the most pow­er­ful rig on the mar­ket today but your sig­nal goes nowhere with­out a good prop­er­ly set­up anten­na sys­tem. I will give you a basic intro­duc­tion to Ham Radio Anten­nas.

There are many dif­fer­ent types of anten­nas for the ham radio oper­a­tor. There are direc­tion­al anten­nas such as the yagi and quad and nondi­rec­tion­al anten­nas such as the ver­ti­cal. Each of these types of anten­nas have their place. There are wire anten­nas of all types and sizes depend­ing on the fre­quen­cy being used and how much room you have to put one up. Wire anten­nas for the most part are semi-direc­tion­al and usu­al­ly radi­ate their sig­nals in a fig­ure eight, broad­side to the plane of the wire. Wire anten­nas can be made direc­tion­al depend­ing on the design and con­fig­u­ra­tion. So can ver­ti­cal anten­nas but it requires more than one anten­na and ade­quate space to erect them.

The yagi type of anten­na is direc­tion­al and has sev­er­al ele­ments that are gen­er­al­ly designed for one fre­quen­cy. There are those that will tune to two or three ama­teur fre­quen­cy bands but lose some pow­er and band­width in the design. These anten­nas are designed to be mount­ed on a tow­er or pole type of sup­port with a means of turn­ing them in the direc­tion that you want the sig­nals to go. They are very pop­u­lar with the seri­ous hams because of their abil­i­ty to receive and trans­mit radio sig­nals in the desired direc­tion.

The cubi­cal quad anten­na, like the yagi, is a direc­tion­al anten­na also. These anten­nas tend to be very large at some fre­quen­cies. They are very effec­tive direc­tion­al anten­nas if you have the room to put them up. Cubi­cal quad anten­nas are made of wire and some kind of sup­port­ing struc­ture such as bam­boo or fiber­glass poles. They also are mount­ed so they may be rotat­ed into the desired direc­tion.

Wire anten­nas are for the most part designed with a spe­cif­ic fre­quen­cy in mind. They can be very sim­ple in design such as a dipole, which is two pieces of wire insu­lat­ed in the cen­ter and installed between two sup­ports and rel­a­tive­ly flat or sup­port­ed by one pole and the sides slop­ing like an invert­ed vee shape or sup­port­ed by a sin­gle pole with the wire slop­ing in the direc­tion that you want the sig­nal to go. These anten­nas are very sim­ple to design, tune and install and are very pop­u­lar with begin­ning ham radio oper­a­tors. Wire anten­nas can be very com­plex also with many pieces of wire, sig­nal traps, coils, insu­la­tors and tuner com­po­nents.

These anten­nas are the most used types of Ham Radio Anten­nas. Anten­na design, tun­ing and instal­la­tion can con­sume a lot of the ham radio oper­a­tors time, but it is very reward­ing when those sig­nals come in and go out where you want them to, with the max­i­mum trans­fer of pow­er.

Source by William Weaver


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Mobile com­mu­ni­ca­tions anten­nas come in all dif­fer­ent sizes and shapes. They also are designed for oper­a­tion on var­i­ous fre­quen­cies usu­al­ly divid­ed into var­i­ous com­mu­ni­ca­tions ser­vices. Some the com­mu­ni­ca­tions ser­vices include the busi­ness band, mar­itime mobile, cit­i­zens band (CB radio), etc.. Regard­less of the fre­quen­cy or band of the anten­na there are sev­er­al com­mon con­sid­er­a­tions to think through when con­sid­er­ing both the type and loca­tion of mobile radio anten­na mounts. This arti­cle will review the major issues and dis­cuss options to con­sid­er.

Each type of anten­na and mount needs to have a good ground and a good ground plane. While the need for this will vary by fre­quen­cy, hav­ing a good ground and ground plane is desired for every fre­quen­cy in prac­ti­cal terms. Many base sta­tion anten­nas use the phys­i­cal ground, enhanced through the use of ground radi­al wires or not, to help form a take-off point for radio waves being trans­mit­ted. On a car the flat por­tion of the top of a car forms a ground plane for a mobile anten­na. Loca­tion of the anten­na on that ground plane becomes impor­tant. A cen­ter loca­tion pro­duces the most near­ly round pat­tern. A loca­tion towards one direc­tion pro­duces an elon­gat­ed pat­tern in the oppo­site direc­tion with less effec­tive­ness in the direc­tion towards the anten­na. While the cen­ter of the roof of a car can be a great loca­tion for a mobile anten­na mount it may be dif­fi­cult to work the coax­i­al cable back to the radio. An eas­i­er solu­tion from the coax­i­al cable’s per­spec­tive may be the trunk. Many peo­ple opt for a trunk lip mount. A mount in the cen­ter of the roof requires drilling a hole in the vehi­cle while a trunk lip mount uses set screws to hold the mount to the lip of the trunk.

Radi­a­tion of as much radio fre­quen­cy ener­gy as pos­si­ble is both a good thing and a prob­lem. If the anten­na is mount­ed in the cen­ter of the roof, the roof acts as a shield and pre­vents your body from being radi­at­ed by the anten­na to the extent prac­ti­cal. If the anten­na is mount­ed on the trunk lip then it is spray­ing radio fre­quen­cy ener­gy right at the pas­sen­gers of the car right through the back win­dow of the car. The amount of radio fre­quen­cy ener­gy and poten­tial risk varies with fre­quen­cy and amount of pow­er used as well as amount of time used.

Oth­er options exist and a review of cat­a­logs and blogs on the inter­net can pro­vide good qual­i­ty pic­tures and review of the advan­tages and dis­ad­van­tages of many of them. Expect to find anten­nas mount­ed on the gut­ters of the roof, var­i­ous sides and cen­ter of the trunk, side pan­els of a vehi­cle, front bumpers, back bumpers and even the engine hood. Remem­ber that there is no 100% per­fect solu­tion and the best solu­tion for a par­tic­u­lar per­son will depend on the type of anten­na, type of vehi­cle, bud­get, tech­ni­cal abil­i­ty, time, patience, etc..

Regard­less of loca­tion and shape of the ground plane, a good radio fre­quen­cy (RF) ground is need­ed. Think of this exam­ple — if neg­a­tive radio fre­quen­cy ener­gy can’t flow to ground pos­i­tive radio fre­quen­cy can’t flow off of the radi­at­ing ele­ment of the anten­na. I often tell new ham radio oper­a­tors there are three things you need to know about mobile anten­na mounts — grounds, grounds and grounds!

Once you deter­mine the loca­tion of the anten­na mount and how to achieve a good radio fre­quen­cy ground (usu­al­ly with a wide strap or mesh — radio fre­quen­cy flows along the OUTSIDE of met­al unlike elec­tric­i­ty) then con­sid­er the TYPE of mobile anten­na mount. Remem­ber that search engines and blogs are won­der­ful things for research­ing types and loca­tions of anten­na mounts. Any one cat­a­log or web­site like­ly will not have every imag­in­able type of anten­na mount. Also remem­ber that every anten­na mount will have both advan­tages and dis­ad­van­tages. I will review an exam­ple of two or three mounts and you will like­ly get the idea.

Con­sid­er the clas­sic ball and large spring mount. For a large whip type of anten­na this can be a good but per­haps not per­fect choice depend­ing on your pref­er­ences. Also con­sid­er a less stur­dy but less “springy” fixed trunk lip mount. Now — if you hit a large tree branch with that whip style anten­na while dri­ving there will like­ly be dif­fer­ent out­comes with these two mounts. The large spring on the ball and spring mount will have a lot of “give” and will allow the whip to stay attached to the mount with the mount stay­ing attached to the vehi­cle while the whip slides under the tree branch. A fixed mount attached to the lip of the trunk with a few set screws like­ly gets ripped off of the trunk and maybe the trunk lip gets bent.

There are dis­ad­van­tages to the stur­dy ball and spring mount which requires four good-sized holes in the body of the vehi­cle to mount it. One dis­ad­van­tage oth­er than poten­tial rust and reduc­tion in trade-in val­ue is the motion of the whip while dri­ving. A mount with­out a spring will result in a stead­ier whip than one with a spring. Remem­ber — the heav­ier the anten­na the heav­ier the mount. Larg­er ham radio anten­nas are tak­en by ama­teur radio oper­a­tors to met­al fab­ri­cat­ing shops to be cus­tomized. Also ask your local auto deal­er for ideas as well as any­one that works with trail­er man­u­fac­tur­ing, etc..

Source by Jon Kres­ki


Category: Antenna
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Ham radio equip­ment can be used by peo­ple with­out ama­teur radio licens­es as long as they do not trans­mit on any fre­quen­cy they do not hold a valid FCC license for. For exam­ple, just about any ama­teur radio trans­ceiv­er will have a high qual­i­ty receiv­er. Peo­ple that may find good use for the ama­teur radio may include avid short­wave radio lis­ten­ers, CB radio oper­a­tors that want to run a sep­a­rate high qual­i­ty receive radio and peo­ple want­i­ng a sen­si­tive AM or FM com­mer­cial broad­cast radio receiv­er. Before you run out and pur­chase an expen­sive ham radio for non-ama­teur radio uses make sure that the par­tic­u­lar radio has all the fea­tures you are expect­ing!

Any per­son want­i­ng a high qual­i­ty tow­er or tri­pod for use with a TV anten­na may be inter­est­ed in ham radio equip­ment of this nature. Ham radio anten­na rota­tors may also be con­sid­ered for TV anten­na pur­pos­es. Make sure to ask the price before mak­ing a com­mit­ment to buy the equip­ment. Also be sure to under­stand the load­ing char­ac­ter­is­tics of the equip­ment. For exam­ple, for a tri­pod or a tow­er, what is the max­i­mum wind speed it is designed to with­stand? Will you need to use guy wires? Will a con­crete pad be required and if so what are the dimen­sions and amount of con­crete required? What sort of ground­ing is required by the Nation­al Elec­tri­cal Code for the tow­er and anten­na? Per­haps most impor­tant­ly, what is the max­i­mum anten­na size the tow­er or tri­pod is designed to safe­ly sup­port? Is the rota­tor strong enough to turn the anten­na in ques­tion?

Some anten­na coax­i­al cables may be able to be used for oth­er pur­pos­es but be care­ful to under­stand the elec­tri­cal and pro­tec­tive char­ac­ter­is­tics of the coax­i­al cable being con­sid­ered. If you trans­mit on a radio designed for one type of coax­i­al cable with a coax­i­al cable not designed for the anten­na and radio used you can destroy your radio in the process. Most ham radio oper­a­tors should either know the var­i­ous types, know where to research the var­i­ous types or know some­one who should know the var­i­ous types of coax­i­al cables and their respec­tive spec­i­fi­ca­tions.

Some ham radio anten­nas can be used for oth­er pur­pos­es. Be care­ful to first under­stand the risk to your oth­er radio equip­ment if you use the wrong anten­na for the wrong pur­pose. One non ham radio pur­pose I found for my Gap Chal­lenger DX anten­na is for lis­ten­ing to com­mer­cial AM radio broad­casts. I found that the 31 foot ver­ti­cal anten­na works great for this pur­pose with the right coax­i­al cable and radio attached. Oth­er anten­nas may be able to be used for oth­er pur­pos­es such as CB radio. Note that it is much eas­i­er to make a CB radio anten­na short­er and use it on the ama­teur radio 10 meter band then it is to length­en an ama­teur radio anten­na for use in dif­fer­ent radio band. Care­ful­ly con­sid­er the pos­si­bil­i­ties, your bud­get and your skills before pur­chas­ing the equip­ment.

Used ham radio equip­ment may be found at the fol­low­ing places among oth­ers — swap fests, Craig’s List, e‑Bay, list­ed in local news­pa­pers and on local ham radio on the air nets. Before you make a pur­chase take time to dis­cuss your project with the per­son sell­ing the ama­teur radio equip­ment to find out if the equip­ment being con­sid­ered will work for your project.

 

Source by Jon Kres­ki


Category: Antenna, Radios
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There are many types of ama­teur radio anten­nas because licensed ham radio oper­a­tors (Hams) have many bands and many thou­sands of pos­si­ble fre­quen­cies they can use for two way radio com­mu­ni­ca­tion.

Most Hams today pass a sim­ple exam­i­na­tion which allows them to start in the hob­by with a VHF portable radio which works in the two meter band. These 2m trans­ceivers trans­mit at around 146 MHz, so a small anten­na works well for them.

Oth­er ama­teur radio oper­a­tors enjoy the excite­ment of long range radio, talk­ing over the short­waves to oth­er hams around town, in oth­er cities or in oth­er coun­tries. They need an ama­teur radio anten­na that is much larg­er, because the radio sig­nals there vibrate at a low­er (and longer) fre­quen­cy. And a trans­mit­ting anten­na always needs to res­onate (or match) the fre­quen­cy of the sig­nal it is send­ing.

So ham radio anten­nas for the short­wave bands vary from wire aeri­als that are more than 200 feet long to maybe 66 feet or so. And ver­ti­cal anten­nas or tow­ers can go up forty feet or more straight up in the air. All these dif­fer­ent two way radio aeri­als have dif­fer­ent strengths and weak­ness­es in store.

Cer­tain ama­teur radio anten­nas are excel­lent for long range work, oth­ers for short range or for mobile or portable use. Then there are beam anten­nas, which con­cen­trate their pow­er in one direc­tion and sup­press sig­nals at their back and sides. These beam anten­nas need to be mount­ed on a mast or a tow­er so they can be rotat­ed and aimed in what­ev­er direc­tion is need­ed that day.

There are three main designs for beam anten­nas. These are yagi anten­nas, quad anten­nas and broad­band log-peri­od­ic dipole anten­nas. Yagi anten­nas may be sin­gle band or mul­ti-band designs, and can he HF, VHF or UHF. The 14 MHz (20m band) is usu­al­ly the low­est ham band they cov­er, espe­cial­ly in 3 or 4 band yagi anten­na designs. Quad anten­nas on the HF bands usu­al­ly have just two ele­ments and can be mul­ti-band­ed. There are cubi­cal quads and spi­der quad designs. (On the vhf bands, a quad anten­na small­er than HF, so it might have four ele­ments. But yagis are more com­mon for vhf and uhf bands.) On the HF bands, log-peri­od­ic anten­nas are real­ly large — so they are more com­mon with gov­ern­ment embassies and the mil­i­tary. Few hams have the mon­ey or the real estate for such large short­wave anten­nas.

 

The sim­plest form of ama­teur radio anten­na is the wire half-wave dipole. This is fed in the mid­dle with coax­i­al cable that runs back to your radio trans­ceiv­er. If a wire anten­na is fed in the mid­dle with twin­lead instead of coax, it is known as a dou­blet anten­na. A dou­blet can be fed with home-made 600-ohm spaced wires, com­mer­cial­ly-made 450 Ohm lad­der-line or com­mon 300 Ohm TV twin­lead. Feed this into a good anten­na tun­ing unit, and you have an anten­na which can be used to work on sev­er­al dif­fer­ent ham bands…a sim­ple mul­ti-band ham anten­na.

In the ear­ly days of ama­teur radio, many hams hand-built a lot of their radio equip­ment includ­ing the receivers, trans­mit­ters and always their anten­nas. Today its a lot eas­i­er to go into a radio store and buy your radio trans­ceiv­er (two way radio) and a range of ama­teur radio anten­nas from dif­fer­ent man­u­fac­tur­ers.

Source by Steven J Deines


Category: Antenna
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