2020 SDR Guide Ep 4 : Antenna Basics for SDR Beginners inc RTL-SDR / Nooelec NESDR SMArt bundle

hi folks and welcome back to frugal radio today's video is an introduction to the most important part of your software-defined radio the antenna we will look at popular antenna types tips for using your antenna i will reveal my favorite frugal coax and i will show you how to make best use of the antenna kits that come in the rtl sdr blog and new elec bundle packages i'm sure you don't want to miss a thing today so let's get stuck in many sdr beginners start off with either the rtl sdr or new elect bundled kits these are great value starter kits because they include everything you need to begin exploring the world of software defined video there are links to both of these bundles in the description below in case you don't already have one as you'll see from the photos they include various types of antennas the common antenna in both is the telescopic whip something you often receive with bass and mobile scanners as well you adjust the length of the telescopic whip in order to get best reception i'll be demonstrating how to do that a little later in this video in the case of the rtl bundle you use two out of the four whips to make a simple dipole antenna again more about how to do that later the new elec telescopic whip is used to make a quarter wave magma and antenna this is the antenna you'll probably use most from the kit the other two are fixed frequency antennas which are less versatile and are best used on the frequency they are tuned for it is important to note the antennas in both these kits are suitable for vhf and uhf operation but not for hf or shortwave reception there are many designs of antennas but probably the three most common types are shown here vertical antennas come in a variety of shapes and sizes they are sometimes known as collinears and sometimes they are made as ground plane verticals in which case you may see spikes known as radials coming out from around the bottom tuned verticals offer higher gain on their design frequencies which can be really good if you want to receive signals in a specific band from a distance disc cones are popular wideband scanning antennas as well typically sold as covering 25 to 1300 megahertz many are designed with a low swr on the 2 meter and 70 centimeter amateur radio frequencies which means they can also be used to transmit if you are a licensed operator prices typically start around fifty dollars for these dipoles are produced for a specific frequency range they can be bought commercially but are also easy to make at home for just a few dollars although they are not considered wideband antennas they can still be used to pick up signals across a wider range of frequencies there are of course many other types so you'll hear about designs like yagi's j-poles slim gyms and so on i'll be releasing a few antenna reviews on the channel over the next few months in this video i want to give you four tips that are going to help you receive more on your software-defined radio if you've been playing with radio for some time you will likely already know these things but if you're starting out you'll want to pay special attention your antenna is really the ear of your radio for it to work at its best it needs to be located high up this is the reason you see antennas mounted on masts and tars on the top of hills and mountains height gives antennas a great advantage so get your antenna as high as possible many people install theirs on the roof of their house or shed and some people actually purchase a small mast or tar for their backyard others are unable to install antennas outdoors for a variety of reasons so they place a disc cone or dipole in their loft my second tip is to position your antenna away from as many obstacles as possible especially objects that block radio signals for example placing an antenna on the floor beside a fridge is not going to serve you well similarly having it next to an interior wall is not going to do you any favors if your antenna is inside you'll generally get a better signal by positioning it next to a window facing the direction you want to monitor for example if you want to listen to a local airport to the west of you try to locate your antenna next to a westward-facing window if it's next to an eastward-facing window the signals also have to travel through the rest of your property to reach your antenna if you live in an apartment and have a balcony make use of it you can attach antennas to balcony rails or place them on small tripods you can even position a magnetic mount antenna on top of a metal patio table or barbecue lid only when it's cool of course having your antenna outside is generally better than having it inside tip number three is to keep coax runs as short as possible coax is the type of cable that runs between your antenna and your software defined video as the electrical current flows from the antenna along this cable it loses power the longer the cable run the greater the loss therefore you achieve best performance from your antenna when your coax is only as long as it needs to be if making your own antennas or installing outdoor antennas keep your coax runs as short as possible the following table allows you to see how much of a signal is lost as it is transferred along different types of coax cable at different frequencies the higher the frequency the more loss that is experienced let's have a look at the table on the 400 megahertz frequency you'll notice that rg174 coax loses 17.3 decibels across 100 feet of cable however rg213 only loses 4.8 decibels and if you go to one of the more expensive cables the rf9913 you'll notice that it only loses 2.6 dashboards over the same 100 foot of cable another advantage that str users have is that we can use uxb extension cables to give us a few extra feet of distance without incurring any loss in signal through coax however usb extension cables can be finicky and of varying quality personally i haven't used cables over distances greater than 15 feet the lowest loss coax cables are expensive and they often have a very thick diameter making them quite challenging to work with and install however there is a great type of coax that works really well for sdr users rg6 is my preferred coax for several reasons firstly it's easy to obtain rg6 is used for most satellite and cable installations in north america and europe frequencies used by tv and satellite range from 470 megahertz to over a gigahertz so this cable performs well across the entire frequency range because it's used so widely the price is low let's compare it to some other types of coax in lowe's i can buy rg6 coax for 12 cents a foot rg 8x from a radio supplier would cost me 69 cents a foot that's five times more expensive and look at the loss values at 700 megahertz the more expensive rg it x cable loses twice as much signal as the inexpensive satellite tv coax coax like lmr 400 is excellent it offers low loss but that means it's thicker and more difficult to handle and more expensive to buy so the frugal radio recommended coax is rg6 satellite coax it offers the best bang for your buck with lower levels of signal loss than many types of coax at an incredible price point my next tip is to let you know you can make your own antennas very easily and at a fraction of the cost of commercial antennas there are lots of designs out there that just need a few pieces of wire a little bit of coax and some connectors one of the first sdr antennas i made was this adsb spyder antenna it was easy to make i connected it to some rg6 attached it to the top of an 8-foot pvc pipe which was then mounted on the roof of my workplace i connected it to a cheap generic sdr which in turn was connected to an old laptop and tuned to 1090 megahertz with that i was receiving position reports from aircraft over 180 miles away i confess i'm not that good at making things i have low diy skills and little experience so it was quite a thrill to be able to build a successful antenna and sdr flight tracking station for a total cost of under 30 dollars many people begin by making dipole antennas and i would certainly recommend this indoor dipoles are very easy to construct using some electrical wire q wax and a terminal block or chocolate block connector as it's sometimes called dipoles are designed to operate around the center frequency so you need to know the frequency you want to use it on then you apply a simple formula to calculate the length of the two elements that you will need to monitor that frequency let's look at the chart here now i grew up in europe so i use meters and centimeters for my measurements i keep my apologies in advance to those of you who use imperial measurements of feet and inches as i can't quite wrap my head around those so here we see the formula is 143 divided by the frequency that's going to give you the measurements in metric if it's foot in inches you want then you're going to do 468 divided by the center frequency that you wish to use so the example i've got here the first one is the civil air band the center of the air band civil range is 127.5 megahertz so to work out the length of the elements we're going to first do 143 we're going to divide that by the center frequency in this case 127.5 that gives us a dipole length of 1.12 meters now obviously we need to divide that in two so we get the element lengths so we divide that by two giving us a length of 56 centimeters and those would be these lengths here if we cut those to 56 centimeters each we would then have a half wave dipole antenna centered in the middle of the airband range while the optimum reception of a dipole will be its design frequency it will still receive signals and other frequencies too just not as well as an antenna tuned for those frequencies but there's nothing to stop you making multiple dipoles for the different frequencies you want you can also easily weatherproof them and install them outdoors for even better reception and range there are also lots of helpful web pages that automatically calculate antenna element lengths for you a quick search online will yield multiple results for those of you using a bundled antenna kit here are the ways you can make best use of it position it at or on a window if using it indoors upstairs rooms will generally work better than downstairs rooms if a window isn't available make sure the antennas view is not obstructed by large solid objects like televisions computer monitors kitchen appliances or walls instead of using a coax extension try to use a usb extension to connect your sdr to your laptop then adjust for the frequency by using the dipole formula that we just looked at earlier in the video okay here i have my laptop running sdr sharp it's connected to a usb extension cable plugged into the extension cable we have the newer lac any sdr smart which in turn is connected to the rtl bundled telescopic dipole setup so right now it's mounted on a suction cup and you can see it's set actually at the minimum telescopic size for that particular antenna so with it set on the smallest size that that telescopic antenna will go the signal to noise ratio is about between 15 and 18 really so let's average that out around 16 somewhere for this particular data signal now watch what happens i'm going to increase the length of the web and we'll see what happens to the actual signal to noise ratio and to that signal as i make the antenna longer so this is the telescopic antenna now extended to its maximum deviation you can see it going up there way up to the top doesn't even fit on the door knife properly it actually pokes through into the property but if we look at the sdr display on the computer you'll see the signal that we're receiving is basically gone it's showing right now a signal to noise ratio of 3.6 sometimes going up to a little over four what crazy difference that makes a lot of people think to get the best out of an antenna telescopic antenna you extend it to the maximum well it's simply not right you need to use the formula to figure out what length your antenna should be so if i make that short again we'll watch the signal increase so we'll just watch the computer screen as i shorten the antenna so here we are again with the antenna now reduced in size back to being the smallest length that this particular telescopic whip can go and actually i would be better putting on the um the smaller whips because even this is a little bit too long for the frequency to make a dipole of this length i really uh the dipole needs to be a little bit shorter but you can see the difference that that makes like i said most people think that having a longer antenna is better simply not the case it must be tuned to the frequency that you want to use it on if you want to receive the best possible signal you can get magnetic mount antennas need a ground plane to function correctly they were originally designed to be used on the roof of vehicles a simple solution when using them at home is to set the magnetic antenna in the middle of a piece of metal this could be a cookie tray the top of a filing cabinet or other metal structure ideally there should be an area of approximately a quarter wavelength of metal around the base of the magmod it's always useful to have sma antenna adapters around if you're experimenting with various antennas both rtl sdr blog and nuelec offer adapter kits which are incredibly useful when you're starting out i've placed links to these in the description below however you can also find these connectors at electronic suppliers across the country well i hope that's been a helpful video for you today if it has please hit the like button and subscribe if you aren't already following the channel there will be some antenna reviews as the channel grows so keep an eye out for those in the meantime this is frugal radio saying over and out

Channel: Frugal Radio

Views: 49,092

Keywords: software defined radio, sdr, beginner's guide, sdr guide, 2020, episode, frugal radio, low-cost sdr, beginner sdr guide, sdrsharp, SDR#, amateur radio, ham radio, VHF, UHF, HF, Frugal Radio (FR), SDRs, Nooelec, NESDR, SMArt, dongle, USB, RTL-SDR, RTL-SDR v3, antenna, antennas, bundle, rtl-sdr blog, discone, dipole

Id: ZPt9ct4lEYE

Length: 15min 5sec (905 seconds)

Published: Tue Jul 28 2020

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[u/FrugalRadio]

This episode is about antennas, and includes a demonstration of how to adjust a telescopic dipole correctly.