The best antenna for HackRF Portapack (and Flipper Zero, Meshtastic, Quansheng, RTLSDR, etc.)

Which antenna is the best one for your  HackRF with well the short answer is   none of these I've tried to make the  longer answer as short as possible   covering only the basics of antenna theory  if you have patience I do feature a cool   gadget halfway through that you will  want to get after watching this video enjoy. First we need to clear something up  and that is that there is nothing magic about   antennas it's just a piece of metal and any piece  of metal with the same length will be equally as   good of an antenna any difference in price will  not be about performance if the antennas are tuned   equally but the difference might be about build  quality and functionality you can even make your   own antennas from cheap pieces of wire and have  just as good performance as the most expensive   antenna you can find the second thing we need to  clear up is that antennas ARE like magic they're   taking the power from the electronic circuits and  making it disappear into thin air when you plug a   device into the wall socket the power in that  socket is AC alternating current it oscillates   the voltage between each pole at a rate of 50  or 60 hertz depending on where in the world   you live Hertz is a measurement that means time  per second a radio is also an oscillator VFO is   an abbreviation for variable frequency oscillator  this just means that you can change the frequency   the frequency of a local FM broadcast station  might be at something like 91.9 MHz that's 91.9   million oscillations per second so what is it  about antennas that make them different from an   extension cord this is where antennas become like  magic if an antenna has a very specific length   it will be resonant at a very specific frequency  if you send oscillating power into an antenna of   this resonant length the power disappears Into  Thin Air it is transformed from the physical   electric circuits into an electromagnetic field  that we know of as a radio transmission if you   however try to send an oscillating signal into  an antenna that is not resonant at that specific   frequency or even worse no antenna at all then  the electric power will be bounced back into   the delicate radio transmitter amplifier circuit  this can destroy your transmitter this is the case   for all radio transmitting devices handheld  radios HackRF flipper zero sub ghz modules   Meshtastic or even Wi-Fi never use any of them  without having a proper antenna connected which   is resonant on the frequency you're going to  transmit on on HackRF transmits at a very low   power output so the reflected power will also be  low especially if you turn down the output gain   and accidentally transmitting on a non-resonant  antenna for short time periods will probably not   damage it but better safe than sorry transmitting  using a non-resonant antenna will also result in   poor performance since less of the transmission  is radiated to understand which antenna is the   best one with first need to understand what type  of antenna it is the most basic antenna type is a   dipole it's just two pieces of metal of equal  length connected to the center pin and shield   of an antenna cable or connector another very  common antenna is a ground plane antenna it's   similar to the dipole but instead the lower  part is a flat plane often made up by several   pieces of metal these magnet antennas are also  ground plane antennas they are actually just   half of an antenna because they require a metal  surface like a car roof to act like the lower   part of the antenna without it they will not be  performing as intended so find a piece of metal   to plunk them onto the same is true for handheld  radio antennas but they use the electric coupling   of your hand on the radio as the lower part of  the antenna if you disassemble some antennas you   will find that some of them are actually dipoles  where the antenna cable goes up through a pipe   in the middle the pipe acts like the lower part of  the dipole and there is a wire acting as the upper   part you will find other aners that is simply a  metal whip relying on the device as the ground   plane or counter poise and some of these whips are  coiled to make the physical length of the antenna   shorter but still meeting the required resonance  length for the specific frequency although at a   lower efficiency so how can we figure out how  long an antenna has to be to work efficiently   first we need to understand that radio  Transmissions happens as a wave with a   real physical size this is called wavelength  you can do a rough calculation of a specific   wavelength by dividing 300 with the frequency  in megahertz and get the result in meters so   if we wanted to know the wavelength of 433 MHz  we do 300 / 433 and the result is about 70 cm   this is why we say that 433 MHz is in the 70 CM  band as we go down in frequency the wavelength   increases for instance 144 MHz is the 2 M BAND  and 50 MHz is the 6 M BAND the antenna size   directly relates to the wavelengths a dipole  is typically a half wave antenna this means   that the physical size of the antenna needs to be  half of the wavelength of the frequency that we   wanted to be resonant at and so that each pole  is a quarter wavelength our quick calculation   from before isn't precise enough to get us an  accurate result for actual antenna designs as   the real calculation is based on the speed of  light and an adjustment Factor but you don't   need to know all this because you can just use  an antenna length calculator either an online   one or the one included in the utilities folder  on your HhackRF Portapack here you can input the   frequency and choose half wave to get the dipole  length the antenna calculator on your HackRF   also gives you a rough estimation of how much you  would need to extend the telescopic antenna 500,   700 or this cheap one you can also choose other  wavelength weed outs such as a quarter wavelength   which is useful for ground plane antennas as their  primary element is basically half a dipole and   thus a quarter wavelength so you might look at  this pile of antennas you got with your hacker   ref and think did some of these have really  wide frequency ranges like spanning several 100   mhz well I'm afraid those numbers are mostly just  made up regular antennas are resonant at a fairly   narrow frequency range like a few megahertz  at best and even if you buy antennas that are   supposedly resonant at a specific frequency  you would be surprised to discover that a lot   of them are actually way off and even if they are  resonant at the advertised frequency the location   they are placed in up objects nearby and even  the antenna cable can sometimes influence the   antenna performance so it's best to measure and  tune antennas before use some antennas provide   a way to tune them by adjusting the length while  others will have to be trimmed either by cutting   down or soldering on more wire since the  resonance is coupled with the wavelength   whenever you shorten the antenna the resonant  frequency goes up and when you increase the   length of the antenna the resonant frequency goes  down we live in an amazing future where what would   have been extremely expensive antenna analyser  equipment can now be had for next to nothing   one such device is the Nano VNA and it is a must  have if you are at all interested in fiddling with antennas the Nano VNA allows us to measure  the SWR standing wave ratio of our antenna the   higher the SWR the worse the antenna resonance  is and the more of our transmitted signal is   reflected back from the antenna the Nano VNA  can do SWR readings across a wide frequency   range allowing us to see the dip in s SWR at  the frequency where the antenna is resonant   we can also see that the width of the usable  frequency range is fairly narrow we need an   SWR between 1.5 and 2 preferably lower if  it is above three it is really bad when we   adjust the length of the antenna that we are  measuring we can see that the dip of the SWR   reading is changing as we increase the length  of the antenna the dip goes down in frequency   and as we decrease the length of the antenna  the dip goes up in frequency we can also see   that simply touching the antenna or moving  it near to other objects especially metal   ones severely changes the Resonance of the  antenna be careful to never actually touch   a transmitting antenna as the voltages can  be very high and cause arcing and skin burns so far I've only been talking about dipoles and  ground plane antennas because they are by far   the most common ones but there are lots  of other interesting antenna designs out there the primary reason for using other  antenna designs is to increase the gain   of the antenna in one or more directions  antenna gain is like squeezing a garden   hose or focusing a flashlight beam increasing  the gain can increase your signal strength   without having to increase the transmit power  a half wave dipole antenna radiates like a big   donut most of the signal is transmitted out to  the sides but a fair bit also goes up and down   if we don't need the signal to go up and down  we can instead use a 5/8 wavelength antenna   this antenna has higher gain and we can think  of this as pressing down on the donut making it   more flat more power goes out to the sides and  list goes up and down another common antenna   type is the directional yagi antenna a yagi  antenna is actually just a dipole but it has   a slightly longer piece of metal behind it which  acts like a reflector the reflector element is   not electrically connected to anything it's  just a piece of metal in front of the dipole   there are several pieces of metal at smaller  and smaller lengths added to increase the gain   in that direction none of these are electrically  connected to anything either they just exploit   the coupling properties of the electromagnetic  field this causes the antenna to have a large gain   in one direction if you go for a walk and look  up you will see antennas everywhere notice that   mostly they are vertically oriented this matters  because if you want to listen to a signal from   a vertical antenna your antenna should be  vertical as well otherwise there will be   a huge loss of signal strength this is known  as antenna polarisation there are many other   antenna designs such as patch antennas phased  array antennas log periodics J Poles circular   polarised antennas QFH antennas Loops spyer  antennas etc etc the discone antenna has a   much wider frequency range than other antennas  some antennas use a satellite dish to reflect   weak signals into the antenna some antennas with  shortwave are made from long pieces of wire some   antennas have built in low- noise amplifiers  that need to be powered and some antennas are   even printed directly on circuit boards a big  parts of the the radio hobby is experimenting   with and building different kinds of antennas  since they are all just simple pieces of metal   you can find the instructions and calculations  online to build them yourself out of cheap materials so which antenna is the best one  for your HackRF well it depends the best   antenna is the one that's resonant for the  frequency you're going to use it on if you   are only receiving it's less important to have  the antenna be perfectly resonant and you can   get away with using some of the bundled antennas  within the ranges they're made for or using the   telescopic whip and adjusting it roughly for the  frequency if you want to listen to shortwave just   get a long wire at least 3 m or longer hang it up  outside and connect it to the center pin of the   hack RF antenna connector you can even connect it  directly to the telescopic whip if you don't have   the proper connectors essentially you're just  extending the length of the whip to be closer   to the much longer wavelengths of short wave as  for transmitting it depends on what you plan on   transmitting realistically you're mostly going  to be transmitting in the ism bands the license   re bands that are used for things like remote  controlled switches doorbells and sensors in   Europe that's mostly on 433 MHz so just get an  antenna for that band if you want to send BLE   packets get a Wi-Fi antenna since Bluetooth  uses 2.4 GHz to get good signal reception you   need to get your antenna outside and up high  clear of surrounding buildings trees and Hills   either by actually going outside with your HackRF  Portapack it is portable after all or by mounting   an antenna outside or at least near your window a  bad antenna placed in a good location will always   outperform even the most expensive antenna  in a bad location so don't waste your money   on expensive antennas if you're just going to be  placing them inside in your basement cave right   next to your noise emitting computer when the  antenna isn't directly mounted to your HackRF   but you're using an antenna cable be mindful  that the cable also introduces signal loss the   thinner the cable the more loss the longer the  cable the more loss and importantly the higher   the frequency you're trying to use the more loss  getting a better antenna cable can be beneficial   especially if you plan on mostly using it for  higher frequencies at UHF or above for longer   distances than a few meters or at very low signal  levels measuring s SWR should always be done at   the antenna feed Point as the antenna cable  can also influence the reading also antenna   cable should not be placed near other electrical  cables network cables etc as they can introduce noise the great thing about learning about  antennas is that any knowledge you gain can be   applied to all other radio devices devices such  as Meshtastic drones or even Wi-Fi I hope this   slightly long video has given you a small  insight into the basics of antenna theory

Channel: sn0ren

Views: 12,646

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Id: wUE8DI61s60

Length: 15min 24sec (924 seconds)

Published: Sat Apr 13 2024