Category Archives: UHF

DSLWP amateur radio satellites launched to Lunar orbit

DSLWP is a lunar for­ma­tion fly­ing mis­sion led by Harbin Insti­tute of Tech­nol­o­gy for low fre­quen­cy radio astron­o­my, ama­teur radio and edu­ca­tion. It con­sists of a pair of 47 kg microsatel­lites launched from the Xichang Space Cen­ter into a lunar trans­fer orbit at 21:28 GMT on Sun­day, May 20, 2018 and they will enter a 300…


Lunar Amateur Radio Satellites DSLWP-A1/A2

Mingchuan Wei BG2BHC reports DSLWP is a lunar for­ma­tion fly­ing mis­sion for low fre­quen­cy radio astron­o­my, ama­teur radio and edu­ca­tion, con­sists of 2 microsatel­lites. Devel­oped by stu­dents at the Harbin Insti­tute of Tech­nol­o­gy the ama­teur radio pay­load onboard DSLWP-A1 will pro­vide telecom­mand uplink and teleme­try / dig­i­tal image down­link.


 

There are two major for­mats for two-way radios. They are Ultra High Fre­quen­cy (UHF) radio and Very High Fre­quen­cy (VHF) radio. Nei­ther fre­quen­cy band is inher­ent­ly bet­ter than the oth­er. They each have their plus­es and minus­es. Both for­mats are effec­tive ways to com­mu­ni­cate with anoth­er per­son. But how do you decide which one will fit your needs? Let’s go over the key com­po­nents of both fre­quen­cies to help you decide.

Two-way radios com­mu­ni­cate with each oth­er through use of radio waves. Radio waves have dif­fer­ent fre­quen­cies, and by tun­ing a radio receiv­er to a spe­cif­ic fre­quen­cy you can pick up a spe­cif­ic sig­nal.

Radio waves are trans­mit­ted as a series of cycles, one after the oth­er. You will always see the “Hz” abbre­vi­a­tion used to indi­cate the fre­quen­cy of a radio. Hertz is equal to one cycle per sec­ond.

Radio waves are mea­sured by kilo­hertz (kHz), which is equal to 1000 cycles per sec­ond, or mega­hertz (MHz), which is equal to 1,000,000 cycles per second–or 1000 kHz. The rela­tion­ship between these units is like this: 1,000,000 Hertz = 1000 kilo­hertz = 1 mega­hertz.

You may also hear the term “wave­length” when you hear about radio waves. This term is from the ear­ly days of radio when fre­quen­cies were mea­sured in terms of the dis­tance between the peaks of two con­sec­u­tive cycles of a radio wave instead of the num­ber of cycles per sec­ond. Low­er fre­quen­cies pro­duce a longer wave­length.

While wave­length mea­sures dis­tance between the peaks of cycles, fre­quen­cy refers to how long the mea­sured time is between the “crest” and “trough” of a wave arriv­ing at the source. So fre­quen­cy mea­sures time instead of dis­tance, but they are essen­tial­ly both say­ing the same thing.

What is sig­nif­i­cant about wave­length for two-way radios is that it affects trans­mis­sion range under cer­tain con­di­tions. A longer wave­length as a gen­er­al rule lets a radio sig­nal trav­el a greater dis­tance.

Low­er fre­quen­cies or wave­lengths have greater pen­e­trat­ing pow­er. That’s one of the rea­sons they are used for com­mu­ni­cat­ing with sub­marines. VLF radio waves (3−30 kHz) can pen­e­trate sea water to a depth of approx­i­mate­ly 20 meters. So a sub­ma­rine at shal­low depth can use these fre­quen­cies.

So from what you read above you may think VHF is always the bet­ter choice for a two-way radio no mat­ter where you are using it. That’s not nec­es­sar­i­ly true. Even though VHF has bet­ter pen­e­trat­ing capa­bil­i­ties, that does­n’t nec­es­sar­i­ly make it the bet­ter choice for build­ings. Remem­ber the con­ver­sa­tion about wave­length above? Wave­length has a big impact on trans­mis­sion.

To explain this let’s assume we are com­mu­ni­cat­ing from one side of a com­mer­cial build­ing to the oth­er. In between these two points is a met­al wall with a three foot door in it. Met­al is an ene­my to radio waves and they typ­i­cal­ly don’t pass through it.

For our exam­ple let’s assume that the UHF wave­length the radio uses is about a foot and a half long and a sim­i­lar VHF radio is around five feet long. These are in the ball­park of their nor­mal wave­lengths.

When the UHF trans­mits its sig­nal the foot and a half long wave will pass through the door since the door is wider than the wave­length. The VHF sig­nal will be total­ly reflect­ed since it is wider than the open­ing to the door.

Your microwave oven is an exam­ple of this. The glass front door has a met­al mesh with very small holes. Microwaves being a very high fre­quen­cy have wave­lengths that are only sev­er­al inch­es long. The mesh keeps the microwaves trapped in the oven but it allows you to see inside because light waves have a micro­scop­ic wave­length.

Just imag­ine walk­ing through the build­ing car­ry­ing a five foot wide pole. You will encounter the same chal­lenges a VHF sig­nal encoun­ters. Now imag­ine walk­ing through the build­ing with a pole that’s only a foot and a half wide like a UHF wave. There are lots few­er door­ways you could­n’t get through.

The one dif­fer­ence is that wire­less sig­nals will pen­e­trate through dry­wall, mason­ry, human bod­ies, fur­ni­ture, wall pan­el­ing, and oth­er sol­id objects. All these objects will reduce the sig­nal strength though. The more dense the object, the more it reduces the sig­nal. VHF will pen­e­trate these obsta­cles bet­ter than UHF, but that does­n’t nec­es­sar­i­ly mean that VHF is bet­ter for indoor appli­ca­tions as we will talk about in the UHF sec­tion below.

In our exam­ple above we assumed you had a met­al wall with an open­ing. If you reverse this and you have a three foot met­al object in front of the trans­mit­ting radio, then VHF would win. Since the object is three foot wide it will total­ly block the UHF sig­nal where­as the VHF sig­nal will get around it. Low­er fre­quen­cies such as VHF dif­fract around large smooth obsta­cles more eas­i­ly, and they also trav­el more eas­i­ly through brick and stone.

For most appli­ca­tions, low­er radio fre­quen­cies are bet­ter for longer range. A broad­cast­ing TV sta­tion illus­trates this. A typ­i­cal VHF sta­tion oper­ates at about 100,000 watts and has a cov­er­age radius range of about 60 miles. A UHF sta­tion with a 60-mile cov­er­age radius requires trans­mit­ting at 3,000,000 watts.

So there is no clear choice for which is bet­ter, VHF or UHF. There is a lot of “black mag­ic” to radio tech­nol­o­gy so it’s not always easy to tell which will work bet­ter for your appli­ca­tion. To help you decide on the best tech­nol­o­gy for you, more detail about each one is includ­ed below.

UHF Radio

UHF equip­ment oper­ates between the fre­quen­cies of 300 MHz and 3000 MHz. Until recent­ly, it was­n’t wide­ly used. Now, the UHF radio fre­quen­cy is used for GPS, Blue­tooth, cord­less phones, and WiFi.

There are more avail­able chan­nels with UHF so in more pop­u­lat­ed areas UHF may be less like­ly to have inter­fer­ence from oth­er sys­tems. If you are in an area where pop­u­la­tion is thin, VHF should work fine for you. Not too long ago the FCC also opened up a new VHF fre­quen­cy called MURS that is so far not heav­i­ly used in most areas. There’s more about MURS below in the VHF sec­tion. If you are in an area where inter­fer­ence from oth­er radios may be an issue, UHF trans­mit­ters and receivers could be your best choice unless you use a MURS VHF radio. UHF is bet­ter at squeez­ing through phys­i­cal bar­ri­ers like walls, build­ings, and rugged land­scape. Any­thing that obstructs a radio wave, will weak­en a radio sig­nal. UHF lessens that effect. Though it may not trav­el as far, UHF radio waves will tra­verse around obsta­cles bet­ter than VHF.

To high­light the dif­fer­ences in indoor range, below is an excerpt from a brochure of a lead­ing two-way radio mak­er on the pre­dict­ed range of one of their lines of hand­held VHF and UHF two-way radios:

Cov­er­age esti­mates: At full pow­er, line-of-sight, no obstruc­tions the range is approx­i­mate­ly 4+ miles. Indoor cov­er­age at VHF is approx­i­mate­ly 270,000 sq ft and 300,000 sq ft at UHF. Expect about 20 floors ver­ti­cal cov­er­age at VHF and up to 30 floors at UHF. Note: Range and cov­er­age are esti­mates and are not guar­an­teed.”

VHF waves are not very good at find­ing their way around walls, build­ings and rugged land­scape. There­fore range will be sig­nif­i­cant­ly reduced for VHF radios in these envi­ron­ments. That may not nec­es­sar­i­ly be a prob­lem if the range need­ed is only a few hun­dred feet. You can also add an exter­nal anten­na to an indoor VHF base sta­tion that will reduce or elim­i­nate this prob­lem.

One of the down­sides to UHF is that the FCC requires you to get a license to oper­ate in these fre­quen­cies. Although many fre­quen­cies in the VHF busi­ness band also require a license. If you choose a radio in the VHF MURS fre­quen­cies you can oper­ate it with­out a license. UHF equip­ment is usu­al­ly more expen­sive. The com­po­nents need to be fine­ly tuned and are more expen­sive to con­struct. This does not mean it’s nec­es­sar­i­ly bet­ter, just more expen­sive.

One advan­tage of UHF trans­mis­sion is the phys­i­cal­ly short wave that is pro­duced by the high fre­quen­cy. That means the anten­na on the radio can be short­er than an equiv­a­lent VHF radio.

VHF Radio

VHF equip­ment oper­ates between the fre­quen­cies of 30 MHz and 300 MHz. FM radio, two-way radios, and tele­vi­sion broad­casts oper­ate in this range.

Both UHF and VHF radios are prone to line of sight fac­tors, but VHF a lit­tle more so. The waves make it through trees and rugged land­scapes, but not as well as UHF fre­quen­cies do. How­ev­er, if a VHF wave and a UHF wave were trans­mit­ted over an area with­out bar­ri­ers, the VHF wave would trav­el almost twice as far. This makes VHF eas­i­er to broad­cast over a long range. If you are work­ing most­ly out­doors, a VHF radio is prob­a­bly the best choice, espe­cial­ly if you are using a base sta­tion radio indoors and you add the exter­nal anten­na.

Since VHF has been around longer and isn’t as com­pli­cat­ed to make, equip­ment is usu­al­ly cheap­er when com­pared to sim­i­lar UHF equip­ment. One dis­ad­van­tage to this equip­ment can be its size. Since the fre­quen­cy waves are big­ger, an anten­na must be big­ger.

VHF radios also have a small­er num­ber of avail­able fre­quen­cies. Inter­fer­ence with oth­er radios could be more like­ly to be a prob­lem. How­ev­er, the FCC recent­ly made this less of a prob­lem when they opened up the MURS fre­quen­cies. The 150 MHz fre­quen­cy is a Cit­i­zens Band radio spec­trum that is called the MURS ser­vice. MURS stands for Mul­ti-Use Radio Ser­vice. This ser­vice is for use in the Unit­ed States and Cana­da. It is a low pow­er, short range ser­vice in the VHF 150 MHz Cit­i­zens Band radio spec­trum. There are 5 chan­nels in the MURS fre­quen­cies with 38 pri­va­cy codes under each one that enable you to only pick up con­ver­sa­tions on your code. The FCC does not require users of prod­ucts for MURS to be licensed.

With MURS you can add a larg­er or exter­nal anten­na to improve range. If you want to put an anten­na on top of your house or busi­ness, you can do it with MURS. Some anten­na man­u­fac­tur­ers claim an exter­nal anten­na can increase the effec­tive radi­at­ed pow­er of a trans­mit­ter by a fac­tor of 4. These MURS inter­coms can trans­mit up to four miles, and per­haps more with an exter­nal anten­na depend­ing on the ter­rain.

One ben­e­fit of VHF wire­less radios is that bat­tery life is almost always bet­ter than for sim­i­lar UHF units. For hand­held radios this is a plus.

VHF equip­ment is usu­al­ly low­er cost for those on a bud­get. Equip­ment can be more eco­nom­i­cal than sim­i­lar UHF prod­ucts.

In sum­ma­ry, if you are plan­ning on using your two-way radios main­ly inside build­ings, then UHF is like­ly the best solu­tion for you. If you are main­ly using your two-way radios for com­mu­ni­ca­tion out­side, then VHF would be a good choice. Either radio tech­nol­o­gy can work for you if you don’t real­ly have a long range to cov­er. In that case you may want to choose VHF for it’s low­er cost.

Source by David Onl­slow


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Upgrade from the General Class License.

 

  • Exam Require­ment: 50-ques­tion Extra writ­ten exam (Ele­ment 4).
  • License Priv­i­leges: All Ama­teur band priv­i­leges.

 

Gen­er­al licensees may upgrade to Extra Class by pass­ing a 50-ques­tion mul­ti­ple-choice exam­i­na­tion. No Morse code test is required. In addi­tion to some of the more obscure reg­u­la­tions, the test cov­ers spe­cial­ized oper­at­ing prac­tices, advanced elec­tron­ics the­o­ry and radio equip­ment design. Non-licensed indi­vid­u­als must pass Ele­ment 2, Ele­ment 3 and Ele­ment 4 writ­ten exams to earn an Extra License. The FCC grants exam ele­ment 3 cred­it to indi­vid­u­als that pre­vi­ous­ly held cer­tain old­er types of licens­es. Find valid forms of Exam­i­na­tion Ele­ment Cred­it.

 

The HF bands can be awful­ly crowd­ed, par­tic­u­lar­ly at the top of the solar cycle. Once one earns HF priv­i­leges, one may quick­ly yearn for more room.  The Extra Class license is the answer. Extra Class licensees are autho­rized to oper­ate on all fre­quen­cies allo­cat­ed to the Ama­teur Ser­vice.


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