Category Archives: VHF

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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I recent­ly con­tact­ed Astro­naut Dou­glas Whee­lock on board the Inter­na­tion­al Space Sta­tion with a sim­ple ham radio attached to a small mag­net mount­ed anten­na inside our home in Apple­ton, WI. While a ham radio license is required, it is not dif­fi­cult to obtain. Ham radio clubs in your area can help you obtain one. Con­tact the Amer­i­can Radio Relay League (ARRL) or vis­it ARRL.org to obtain more infor­ma­tion. The radio equip­ment required is not over­ly expen­sive in my opin­ion. While I made my con­tact with a radio in the $750 price range, a sim­ple 2 meter ham radio in the $200 price range would be just fine as well. The anten­na I used was a mag­net mount anten­na attached via mag­net mount to our 4 draw­er office file cab­i­net. The anten­na is in the $50 price range. If you do not have a file cab­i­net any large met­al object would prob­a­bly work as well. Many peo­ple use kitchen cook­ie sheets. A stove would work and a wood stove would be excel­lent.

My first con­tact with him was on 10/11/2010. Was it worth the effort… well… YEAH!!!

• My 2 meter ham radio used 50 watts but you can do the job with a HT (hand-held radio) and 5 watts. Peo­ple have used hand-held ham radios and as lit­tle as 5 watts. If you go the portable radio route then a satel­lite anten­na (a hand-held beam anten­na) is sug­gest­ed.

• One thing that is required is the abil­i­ty to trans­mit on one fre­quen­cy and lis­ten on anoth­er. Sound like basic repeater func­tion­al­i­ty? Yeah — but the dis­tance between the receive and trans­mit fre­quen­cies is much greater than on stan­dard repeaters. Read fur­ther for details on fre­quen­cies. No tones are need­ed for the Inter­na­tion­al Space Sta­tion (ISS). Tones are required for oth­er ama­teur radio satel­lites.

• Very help­ful in my esti­ma­tion is the abil­i­ty to track, or pre­dict, when the Inter­na­tion­al Space Sta­tion (ISS) will fly over, what direc­tion it will come from and go to, and what height (angle) it will be in the sky. There is no one best method. Your choice will depend on your bud­get, resources, etc.. I had a PC and inter­net con­nec­tion and I down­loaded the FREE “Ham Radio Deluxe” pro­gram that includes a satel­lite track­ing pro­gram. Get your Ham Radio Deluxe soft­ware FREE and get to know it. I used the soft­ware to alert you, even via dig­i­tal voice, when to make your attempt. There are web-based alter­na­tives — do a Google search for “satel­lite pre­dic­tions” and “satel­lite track­ing” for many more alter­na­tives.

• Know the cor­rect fre­quen­cies. Vis­it AMSAT,org to find the infor­ma­tion on var­i­ous satel­lites and how to work them. For specifics on the Inter­na­tion­al Space Sta­tion (ISS) go to their sec­tion. Specif­i­cal­ly, read every­thing from this sec­tion http://www.amsat.org/amsat-new/ariss/#freqs through the bot­tom of the page.

• Set-up your radio. Ham radio repeaters use spe­cial silent tones in some instances. This allows mul­ti­ple repeaters to use the same fre­quen­cy with­out inter­fer­ing with each oth­er. The ham radio oper­a­tor trans­mits a silent tone on the spe­cif­ic fre­quen­cy to sig­nal which repeater s/he wants to oper­ate with. The Inter­na­tion­al Space Sta­tion (ISS) uses no tone. Learn to say your call sign in prop­er, stan­dard pho­net­ics. Remem­ber that you are talk­ing to trained pro­fes­sion­als. They will NOT appre­ci­ate and may not even under­stand any “cutesy” per­son­al­ized pho­net­ics. Also learn to trans­mit your CITY quick­ly after your call sign. The city will help oth­ers know that the astro­naut wants YOU to tell them the rest of your call sign in case they miss part of it.

• Last­ly, do have some patience. They may be busy. You may be busy. Remem­ber that ham radio on the Inter­na­tion­al Space Sta­tion is gen­er­al­ly done in their spare time. Good luck bust­ing your first space pile-up!

specif­i­cal­ly

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Source by Jon Kres­ki
Category: VHF

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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