Bought an RTL-SDRv3 and MLA-30 loop! Advice needed! - Page 1
Forum section: electronics / rf-microwave

author: edy
author_rank: Super Contributor
timestamp: June 18, 2020, 03:01:05 am
content: Hi everyone,I have been enjoying my Tecsun PL-310ET for the past 5 months and now decided to dive in to an SDR. I picked up an RTL-SDRv3 (from the official storehttps://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/) and an MLA-30 loop antenna (https://www.aliexpress.com/item/4000975387758.html). I have yet to receive it but I've been reading stuff to get prepared and was hoping for some advice as to which of these ideas make sense.This SDR and loop antenna are very popular and cheap, with tons of YouTube videos on them. I'm trying to sort through the advice given and hopefully hear from someone with more experience and technical knowledge about this stuff.The first thing I saw was that as soon as people get the MLA-30 they cut the cable off and hook up a BNC connector. Some will also not even bother connecting the Biasing-T, saying it does nothing or make the signal worse (perhaps noise from their USB/power supply is bad). The RTL-SDRv3 has a built-in software toggled 4.5v Bias-T so perhaps that is why you don't need the one from the MLA-30 when using it with the SDR.I am not sure what connectors are being used and whether I need any adapters to connect to the RTL-SDR. It says SMA and they look like it... are these the same thing as my old cable TV coax? I have tons of spare coax cable but it's supposedly 75 ohm stuff. Should I be changing the cable coming out of the MLA-30? Should I be splicing up BNC connectors and making BNC cables (and getting a bunch of adapters)? Can I use a threaded SMA cable-TV type connector instead with my existing TV coax? Should I be getting 50 ohm cable or is 75 ohm ok?My Tecsun has a 3.5mm mono input for antenna, so with a BNC cable I could potentially hook it up to this BNC to 3mm mono adapter:https://secure.sayal.com/STORE2/View_SHOP.php?SKU=247405. I would like to be able to use the MLA-30 with my Tecsun as well, so I'm going to have to figure out what kind of cables I need to make. For those that change the main output cable of the MLA-30 to a BNC connector, I assume if they want to hook up the Bias-T they will need a cable with BNC on one end and SMA on the other end (which the Bias-T has). If I want to hook that into my Tecsun and use the Bias-T I will need to go from SMA to a 3.5mm mono. I haven't seen too many SMA cable ends at my local shop, it seems BNC is supported more so if I have to splice together a cable I can get all the bits and pieces and try to make something.Which brings me to the RTL-SDR. There is some debate as to whether to mount it close to the computer, or far away, how long a USB cable should be and so on. I'll explain my setup, it is pretty rudimentary at this point so that may limit things anyways.I'm planning to use it with my Linux laptop which has to be plugged in (battery it old, doesn't last much if not plugged in). I don't know if plugging in my laptop will cause a problem but when I charge up my Tecsun from the outlet (to charge it's internal NiMH batteries) the reception goes to crap and basically is unusable until the batteries are fully charged and I listen on battery-only again.Should I be plugging the RTL-SDR dongle straight into my computer, or should I have some kind of USB extension cable and have it a few feet away? I see people putting those snap-on ferrites on each end of the USB cables also. I plan on being a few feet away from the antenna which will be indoors or at best propped out my upstairs (2nd floor) window temporarily. So really I would only need a short USB cable (if any) and a few feet of cable to run from the antenna to the RTL-SDR.It looks like the RTL-SDR has an SMA connector, again I assume that is what a typical average person would recognize as the cable-TV connector for coax in homes. For simplicity is it better to just try to connect an SMA female connector to the MLA-30 instead of the BNC? Then I run my regular TV coax cable by threading one end on the MLA-30 and the other end to the RTL-SDR input? Or if I use my Tecsun radio I could potentially run the cable to from the MLA-30 to the Bias-T it comes with, and then make myself some kind of adapter (or even a short cable going from SMA to BNC) and use that BNC-3.5mm adapter? I have seen also some SMA female to 3.5mm mono adapters. Something like this maybe:https://canada.newark.com/mcm/27-805/female-f-to-male-3-5mm-adapter/dp/39C0542Sorry, so many questions and I still don't have even my order yet! Maybe I should just try it without any mods and just pray that I can get my Linux machine (Ubuntu) set up properly and all the drivers configured and see what happens first.

author: cdev
author_rank: Super Contributor
timestamp: June 18, 2020, 03:27:33 am
content: You'll need a USB extension cable and a bunch of ferrites. You may need to blacklist the DV driver.The RTLSDR in direct sampling mode does really well with a magnetic loop, which is jst a loop of wire and a variable capacitor and another small simple pickup loop that you put inside the larger loop.You know its working when the capacitor causes a wave of signals and noise to go up and down the spectrum. A high-Q loop should be very sharp..As far as an active loop, it should work but youre on your own. The RTLSDR dirct sampling works better than one would expect considering its a hack. But its still just an 8 bit SDR. its not a serious HF radio. Performance wise it may be better than the Tecsun but it also might not be. The cool thing about the RTLSDR and a magloop is a maglop is exactly what the RTLSDR lacks, a super sharp bandpass lifer. Its like a helical resonator for HF.Use the direct sampling Q input setting for HF. You can use CubicSDR software for general listening.I would recommend finding an appropriate variable capacitor and trying it out. You can just use a loop of insulated wire and any old variable capacitor, a multigang one from an old radio works great. USe a bunch of alligator clips to adjust the capacitance.Some of my best shortwave listening experiences have been with (tuned) magloops made just on the spur of the moment from parts that were lying around..

author: edy
author_rank: Super Contributor
timestamp: June 18, 2020, 01:06:13 pm
content: Thanks. I'm looking at some of the software and it is intimidatingly complex. There are so many options. I installed SDRSharp on one of my Windows 7 machines and don't know anything about setup and all these plugins that are available. I plan to use it on my Linux machine mostly. Seems SDRSharp is the most popular and powerful software. Hopefully something on Linux comes close in terms of features. I see that there are a bunch of complex steps involved downloading drivers initially, disabling other stuff in Linux and running command-line stuff to enable and disable features (like direct sampling Q). i guess once I have my hands on and start doing things I'll slowly figure it out and meet each challenge as I get there.So for now I should think about getting a 4-6 ft USB extender and maybe a couple of clip-on ferrites for each end? I still don't know what I should be doing about cabling and if I should bother replacing the thin cable that comes out of the MLA-30 with a SMA or BMC connector, and what I should do regarding 50 vs 75 ohm coax I have tons of laying around from my old TV. Finally, what's the easiest way to hook it up to my Tecsun antenna 3.5 mono input? Can I build myself an adapter if I just buy a bare 3.5mm mono connector? Does the tip go to the inner solid copper core of the coax?

author: Circlotron
author_rank: Super Contributor
timestamp: June 18, 2020, 01:19:42 pm
content: I used Gqrx on Linux. Not much in the way of options, but at least it just worked. Don't think there was anything at all in the way of fiddling around to get it running. You might want to try that first just to check your setup is running before moving on to something more sophisticated.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 18, 2020, 02:27:31 pm
content: I really do not think it matters if you use 75 or 50 ohm coax. However you do need the bias "T' .The MLA 30 is 50 ohm and your dongle is probably 75 ohm. The little Bias T connector box may have a transformer in it (50 to 75 ohm).75 ohm coax should be no problem on a receive only antenna. 75 ohm has lower loss than 50 ohm coax usually. Putting the correct connectors on might be a problem though. The Bias T supplies power that is DC over the coax that is used to amplify the antenna at the antenna connector box, so I think that doing away with any of these things defeats the purpose of the antenna. It essentially lets both the received signal (RF) and the power to share the same wire. Your dongle may do the same thing. Maybe with less loss and with less opportunity for interference.I would just connect things as they are to start with, then:If you wish to use your TV coax,I would get some decent adapters and/or connectors, figure out which ones you need, and order some, I do not know what freq you are planning to listen to. BNC may not work well at above 1 GHz. Physically connecting things to the 75 ohm TV cable may be the hardest thing to accomplish. Every connector or adapter has loss and some of them are hard to install correctly. You may want to look at the frequency specs of your 75 ohm cable.Maybe criticisms of the modifications to 75 ohm coax are due to bad connections,Also some of the cheap connectors and adapters do not work well at higher freq.You may want to get a shielded USB cord. Sometimes they help. Not really sure here. All the usb is doing is supplying 5 VoltsWally

author: cdev
author_rank: Super Contributor
timestamp: June 18, 2020, 02:40:11 pm
content: SDRSharp doesnt work for me on Linux. If anybody else has had success with it, please let me know.GQRX works, and with some things sometimes its worked better. I also like Linrad for HF particularly, for many things, although it has a steep learning curve, its worth learning. But te user interface makes changing modes and managing your preferences somewhat difficult, unless you use Unix to set up wrappers with your different settings which requires a high level of organization.. .CubicSDR is probably the easiest to use for beginners use on Linux.Linux setup is easy, just install your distros RTLSDR packages. You may find that your DVB dongle is picked up as DVB and not RTLSDR if your distro does not install udev rules. You may have to blacklist the DVB driver, see if its activated by means of the lsmod command. Look up Blacklist rtl2832 or something like that, I forget - it seems that I have not had to do that in many years on my system.Add ferrite beads until it stops making the noise better.Quote from: edy on June 18, 2020, 01:06:13 pmYou'll figure it out.Man pages are always helpful.

author: edy
author_rank: Super Contributor
timestamp: June 18, 2020, 04:05:05 pm
content: Thanks. I love this hobby as it is cheap to get into at a basic level, has a lot of stuff to learn, lots of free software available and so much room for growth. The last few years in particular with cheaper SW radio options and now SDR has really made it extremely accessible. There are also so many interesting signals to explore, and I can still be hands-on and build basic things.One of my first exhilarating experiences was randomly stumbling across some Cuban numbers station, and also some beacons in the 300-500 kHz range. I've found some AM over SW in the 3800-3900 kHz range that I could listen to, but many other "garbled" stuff which I can only presume may be on LSB/USB and my Tecsun can't decode those. So I'm hoping with the SDR I can start to explore LSB/USB communications, and learn about all the other stuff out there (digital signals, satellite data, image/video broadcasts, etc) that I see can be decoded if you have the right software/plugins. I'll have to find a master list somewhere of all the frequencies with these interesting things and have a go at receiving them.

author: MarkMLl
author_rank: Frequent Contributor
timestamp: June 18, 2020, 04:08:18 pm
content: Quote from: cdev on June 18, 2020, 03:27:33 amA /good/ USB extension: it it's long enough to get the SDR far enough from the PC to be clear of its QRM it's likely to drop too much voltage to be usable.MarkMLl

author: edy
author_rank: Super Contributor
timestamp: June 19, 2020, 01:19:32 pm
content: After seeing a bunch of YouTube videos and reading more review articles and blogs, it seems the most effective mod to the MLA-30 is to change the thin cable that exits the box with a jack (either BNC or SMA). People have tried making thicker loops (out of copper tubing instead of the thin wire it comes with) or adding ferrites to the inside cable and other methods. But the biggest improvement seems to be from having the option to use a better shielded thicker cable of your choice. I may opt for SMA jack (rather than BNC) since the RTL-SDR has an SMA jack also and I can use an RG-6 or various other TV coax cables I have lying around all of which have SMA males on either end. Apparently 50 vs 75 ohm didn't make a big difference for a short (few feet) run.I guess the other thing to consider if I use the Bias-T it came with is to find a USB 5v power source that is as clean a source possible. I'm not sure if a portable battery bank charger USB is any better than a well built mains supply, however one is DC to DC so that may already be improve the things? Or do I just have to try a bunch of supplies and see what interference I get? With the RTL-SDR I should be able to avoid the Bias-T box as the dongle can output 5v with a built in Bias-T. However it's 5v while apparently the antenna one actually converts the 5v of the USB and outputs 12v... people have reported it still works?The MLA-30 has been de-potted and analyzed and found to be a simple one step amplifier. There is a gain trim you can actually access (not potted) which is said to be a variable resistor. This is hooked up to the amplifier IC which I guess has a resistance-controlled amplifier gain setting.I have to also consider how to convert SMA male to 3.5mm mono male for my antenna input on the Tecsun. I see female F threaded connector adapter to 3.5mm but F looks way bigger than SMA. I may have to buy a combo of adapters. Hopefully having a few adapters linked up won't mess up the signal too much. Otherwise I may just buy a bare 3.5mm mono jack and solder the end of the coax to it.

author: cdev
author_rank: Super Contributor
timestamp: June 19, 2020, 08:15:40 pm
content: A bettery is the quietest power source for HF.They sell active USB extensions that basically contain a USB hub and they can be pretty long, I have one thats around 3 meters long. Adding lots of ferrite beads helps considerably, with the point of diminishing returns being a bunch of them.. six or more..Quote from: MarkMLl on June 18, 2020, 04:08:18 pm

author: MarkMLl
author_rank: Frequent Contributor
timestamp: June 20, 2020, 07:35:17 am
content: Quote from: cdev on June 19, 2020, 08:15:40 pmWell yes, better than anything else :-)QuoteAs a general query, should multiple ferrites be lumped at the ends of an extension or distributed, or does it depend on the source of the noise?I've recently found some adapters on Banggood which are very useful for measuring USB resistance:https://www.banggood.com/USB-Adapter-Board-Male-to-Female-Micro-Type-C-4P-2_54mm-USB4-Module-Converter-p-1543936.html?rmmds=myorder&cur_warehouse=CNhttps://www.banggood.com/5pcs-USB-To-DIP-Female-Head-Mini-5P-Patch-To-DIP-2_54mm-Adapter-Board-p-1167636.html?rmmds=myorder&cur_warehouse=CN...with the caveat that there's two sets of Vcc and Gnd connectors, and the tracking to one is heavier than to the other.MarkMLl

author: cdev
author_rank: Super Contributor
timestamp: June 21, 2020, 12:17:13 pm
content: re ferrites, I usually put mine at the ends, but honestly I don't know what would be best.

author: edy
author_rank: Super Contributor
timestamp: June 28, 2020, 03:28:20 pm
content: I’m still waiting for the Mag loop and SDR but this morning I was browsing the waves on my Tecsun and picked up a flurry of activity between 7000-7070 that sounded like CW Morse code although it seemed more complicated. I have attached some sample recordings.I tried to decode with a few different apps and an online tool:https://morsecode.world/international/decoder/audio-decoder-adaptive.html...to which I uploaded the files and it decoded into some kind of unintelligible jibberish. I haven’t tried a Linux-based app yet... does anyone have any recommendations? I have no idea what this is so I could be using completely wrong tools to try and decode it. It could also be the quality of the recordings... I was getting lots of static and poor reception. Also no idea where it’s coming from.I zipped them up as I couldn’t upload M4A format. It was recorded from iPhone voice recorder held up against speaker of the radio. Once I get my SDR this process will probably be much easier.

author: edy
author_rank: Super Contributor
timestamp: June 29, 2020, 03:19:49 am
content: Ok, so I installed "fldigi" fromhttp://www.w1hkj.com/using these commands:Code:sudo add-apt-repository ppa:kamalmostafa/fldigisudo apt-get updatesudo apt-get install fldigiIt installed I was able to load up the WAV files of those audio recordings I attached previously but there are so many modes I don't know what kind of signal these are. I choose from the menu and sometimes random text pops up but nothing I can read. Is it a matter of guessing and learning eventually what mode these chirps are?

author: A.Z.
author_rank: Super Contributor
timestamp: June 29, 2020, 09:45:52 am
content: Hello Edy and everyone else, I'm new here and this is my first post on this forumRegarding the MLA-30 active loop antenna, I think that you may find this review illuminatinghttps://www.g8jnj.net/activeantennas.htm#webs-bin-5d91d4d81739bbe7aba9ac8cin short, the MLA-30 design falls short on several aspects, starting from the noisy power supply and going all the way to the antenna/preamp impedance mismatch; sure, with a bit of patience and a soldering iron, one may modify the power supply and then try adding a transformer between the loop and the preamp input (the low pass filter) to at least try improving a bit the impedance matching, but my guess is that even with such mods, the MLA-30 won't be a so good performerTo say it all, some time ago I was evaluating some options for my simple SDR setup (I'm running an MSI.SDR unit - 10KHz-2GHz - 12 bit ADC) and considered the MLA-30 thinking it would have been a good antenna for my limited space, but then after reading the tests performed by Martin (G8JNJ) I discarded the idea and kept thinking about other antenna options for my space constraint setup; at the moment I'm using a short "cobra" dipole (around 8mt total) which I built and installed on my balconyhttps://www.nonstopsystems.com/radio/frank_radio_antenna_cobra.htmand I'm rather satisfied with it, it's much quieter than the other wire antennas I tried before it (but absolutely not deaf) and till now, it is serving me rather wellAndrewEDIT:Forgot, regarding the connection of the antenna to your tecsun, you may use a short run of coax (the TV one will be ok) to build a "pigtail" cable with two connectors like these (just an example)https://ae01.alicdn.com/kf/HTB1rJRuWhTpK1RjSZFKq6y2wXXaB.jpg_q50.jpgand use it to connect the antenna feedline to your receiverAs for Linux, to decide which software you like better you may try a SkyWave Linux "live" CDhttps://skywavelinux.com/just boot your laptop from the live distro and fiddle with the software, then by the way you'll also want to "RTFM" a bit

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 29, 2020, 01:54:16 pm
content: I have the MLA to the work good for me. For a Permanent Setup is there a better one available?Does anyone change the Cable how much performance it bring?

author: A.Z.
author_rank: Super Contributor
timestamp: June 30, 2020, 07:14:02 am
content: Quote from: Lord of nothing on June 29, 2020, 01:54:16 pmFine with me, but personally I'd rather go for a different antenna, even a simple passive loop like the one describedherewould give you much better SNR (and will probably perform better), plus nothing forbids one from adding an LNA unit to such a passive loop antenna, and the resulting setup will probably work much better than the bad design used for the MLA-30QuoteThe above one should fit, otherwise, willing an active loop and not willing to pay a lot of money for it, one may build the"WellGood Loop"it's a clone of the commercial "WellBrook ALA1530" loop but can be built at a fraction of the costQuoteWhile it may help a bit, I doubt it will do much. The problem with the MLA-30 is that the preamp stage is badly matched to the loop so causing the antenna performance to wildly vary over the bands, the preamp also has issues with IMD and the power injector unit uses a voltage multiplier to raise the 5V coming from the USB to the 12V used to feed the preamplifier, such a circuit generates a lot of noise which by the way worsens the situation; as I wrote it may be possible to modify the antenna a bit by adding a small wideband transformer/balun between the preamp input and the loop to try improving the matching and then modifying the power injector bypassing the voltage multiplier and directly feeding 12V to the bias T from a good and "silent" power supply unit, but at that point, wouldn't it be a better idea picking a different antenna?

author: cdev
author_rank: Super Contributor
timestamp: July 01, 2020, 09:24:09 pm
content: A well designed mag loop absolutely does not need a preamp. It should virtually crackle with signal, to the point where you have way too much signal a lot of the time. (In other words make a simple L-pad attenuator - this is an absolute must because RTLSDRs in direct sampling mode have no tolerance for such strong signals. I use a off the shelf CATV attenuator Ive had for ages)Luckily the super selective nature of the mag loop makes up really well for most of the RTLSDR's deficienciesPaired with a better receiver - if you are blessed with a quiet QTH (not my situation unfortunately) it might even be really good.How much signal might come out of a good mag loop tuned to a strong HF signal? (The bible thumpers and Radio Havana both used to do this, splattering all over the bands when I attempted to use my RTLSDR for receive without an attenuator)Some huge amount of RF is captured by a resonant loop., probably enough to on its own deflect a d-arsonval meter movement if you connect it up using a 1N34 germanium diode and capacitor . You could probably light up a small LED too. At least enough to see. (not bright, though)

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 01, 2020, 09:49:40 pm
content: In my case I would like use a Signal Combiner to get all direction covert up.I need to run my own HF decoding station. So a bunch of HF SDR I could use.Maybe use an propper Upconverter so all SDR could be normal and "cheap" one.

author: edy
author_rank: Super Contributor
timestamp: July 01, 2020, 10:15:34 pm
content: Quote from: A.Z. on June 29, 2020, 09:45:52 amThanks, I still haven't received my MLA-30 loop and RTL-SDRv3, so I can't report on any results so far. However, I am downloading Skywavelinux and will make myself a USB key and try booting it up and seeing what's there. I figure that's going to be easier than trying to find and install all the different radio software into my existing Linux installation. Also I would be trying to boot into some of my other machines and comparing performance. Hopefully skywavelinux has "persistent storage" or at least allows you to access a drive that you can save audio files or video captures.Hey I just did something really cool!!!! NEVER TRIED IT BEFORE! I went onwebsdr.organd was able to find all sorts of places around the world were I could tune in to various broadcasts! I also loaded up my local installed instance of "fldigi" and had it listen to the audio on my sound card (coming from one of the websdr.org stations) to try and decode the signal (RTTY or CW or otherwise)! Wow! This is amazing, even without an RTL-SDRv3 dongle I can already have fun listening!Went to Waller County Radio Club and tuned into 7047 kHz to a CW signal (http://74.118.150.5:8901/?frequency=7000#). It was just a bunch of beeps but with fldigi listening in on the soundcard, I was able to put it into CW mode and got the following text:QuoteIt is still full of mistakes but it at least looks somewhat legible!I also just installed the following "wsjtx" app on my Linux machine and tried to decode FT8 stuff, same idea.... on a websdr.org channel, grabbing a certain bandwidth and having the audio going to the wsjtx app for decoding:https://physics.princeton.edu/pulsar/K1JT/wsjtx.htmlAnd I just picked up RTTY athttp://n8mdp.ham-radio-op.net:8904/7094 kHz which I assume to be the base frequency and a signal at +1 khz very narrow. They keep testing out different modes, CW, RTTY (which has a spectrum with 2 peaks) and now BPSK-31 (a single peak). Here is the RTTY broadcast:QuoteAnd then the latest transmission in BPSK-31:QuoteI also heard some septuagenarians chatting about their old wives, keeping up with the computer decoding stuff and this whole FT8 thing taking over,!...plus some discussion on PSK, JT-9 and other stuff. Very interesting listening in on these conversations, you can learn a lot!How am I supposed to know what type of digital mode is being transmitted? I am guessing based on my limited experience, listening to examples athttp://www.w1hkj.com/FldigiHelp-3.21/Modes/and just trying my luck with the fldigi program to decode and see if unscrambles properly. Is that how it's done, or is there some easier way to know what mode these digital transmissions are in? Sometimes I compare spectra with the examples to see what bandwidth it takes up, how many peaks and how they are spaced.

author: edy
author_rank: Super Contributor
timestamp: July 05, 2020, 07:21:33 am
content: I had a difficult time putting together a bootable USB key with the skywavelinux ISO. I tried dd, unetbootin and a few others but in the end only Rufus did the trick, and on a Windows machine no less! I had a 4gb USB key so the first 2 gb are for the system and the remaining 2 gb were formatted as more persistent storage so I could save screen recordings, HAM books and other resources as I go along. Apparently an updated skywavelinux was slated to be released this spring but it hasn't yet happened. The current one is based on xenial 16.04 which is quite old now, but as long as it works I don't care. I hear skywavelinux 4.0 is coming soon (any moment) and I've seen some previews on YouTube! Can't wait!

author: edy
author_rank: Super Contributor
timestamp: July 10, 2020, 09:11:24 pm
content: I finally received the first half of my order... the MLA-30 loop antenna! I opened it up and had a brief look. It appears that the connectors on the antenna and the Bias T box are all a "mini" version of an SMA connector. It looks about 75% the size of a regular cable TV coax type SMA. Does this go by some other name? Now I understand why a lot of people will swap out the cable that comes with the MLA-30 loop and ditch it for either a BNC or regular size SMA coax type connector. I'm assuming the connector to the RTL-SDRv3 is a standard cable TV size coax, so the MLA-30 won't even connect to the RTL-SDRv3 out of the box. Does anyone know?Now the Bias T box it comes with also has those "mini" SMA connectors. If I want to use this box to power the antenna, I will need to also swap out the connectors on this box (much harder to do) or keep the small-size cable from the MLA-30 and find adapters to switch up to the larger size SMA. That's fine if I want to use the Tecsun for reception.However, if I use the RTL-SDRv3 I don't even need the Bias T because RTL-SDRv3 comes with a built-in Bias T that I can activate in software. Apparently the MLA-30 bias-T takes 5V USB input and then upconverts and sends 12V to the MLA-30. However the MLA-30 box says "input 5-12V" so it seems to work on a range of voltage and likely the RTL-SDRv3 will send 5V anyways as it is USB-powered.Does anyone have an MLA-30 and did it come with mini-SMA connectors, does it connect to the RTL-SDRv3 or did I get some strange knock-off product with the wrong size connectors?[UPDATE:]I just measured my regular cable TV cable SMA and it is 11mm across flat side of the hex, and the one with the MLA-30 loop is 8mm. It's probably just me being new to this subject so I'm not sure if SMA cables have different hex diameters as the average person would probably have only experienced a cable TV coax hookup. That's why I was surprised to see this smaller version.Ok I think I figured it out (silly newbie mistake)....the coax cable TV one is called an "F" connector. The SMA is "SubMiniature version A". It even says on the Wikipedia page (https://en.wikipedia.org/wiki/SMA_connector):QuoteI had no idea. You look at the pictures online as a newbie and unless you've ever come across it before, they all look the same. That means it is likely the RTL-SDRv3 will connect no problem to this antenna. All I need to find then is an SMA to mono 1/8" (3.5mm) adapter to plug into the Tecsun antenna input. Something like this (but eBay cost for such a cable is about $4 but they kill you on the shipping... adds another $7+ at least):Or I can pick up these 2 items for about $1.50 each (free shipping), total $3 should solve the problem for getting it to my Tecsun antenna input jack (from from SMA to F-type to 3.5mm):https://www.ebay.com/itm/1-F-Type-F-Jack-To-SMA-Male-Female-Plug-RF-Coaxial-Connector-Adapter-Convertor/392421705577F male to SMA female....PLUS THIS F female to 3.5mm mono, from my local store....https://secure.sayal.com/STORE2/View_SHOP.php?SKU=164696or from eBay... almost same price but in US$ a few cents more:https://www.ebay.com/itm/1-RF-Coaxial-Coax-Adapter-F-Female-Type-to-3-5mm-Male-Connector-for-FM-Antenna/392449952581

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 10, 2020, 11:37:03 pm
content: Does anyone here use the Tecsun Antenna to? With there Antenna I could not receive anything.With my MLA I could receive Radio on the Band.

author: A.Z.
author_rank: Super Contributor
timestamp: July 11, 2020, 06:32:10 pm
content: The MLA30 uses a standard SMA connector at the end of the coax going to the rx; so those "hex connectors" are just regular SMA ones; as for powering the preamp, it works with 12V DC while the RTL bias tee outputs 5V, now the MLA30 preamp may work at 5V but I suspect the preamp dynamic range and IMD will suffer, so you'd better use the original power injector; as for the adapter just find a SMA fenale to jack one and you should be ok

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 11, 2020, 07:22:57 pm
content: I use the other SDR and get good results out of it. Let be say it so I receive something where I before nothing (ok ok except Radio) received.So for someone who is not sure if he is able to receive any HF its a good one for the start.

author: edy
author_rank: Super Contributor
timestamp: July 14, 2020, 03:53:38 pm
content: Skywavelinux 4.0 released!!!!Perfect timing!https://skywavelinux.com/I'm going to try and make a persistent storage version so I can modify the key with additional apps. This tutorial seems to show how, I'll give it a try and report back with my results:https://www.howtogeek.com/howto/14912/create-a-persistent-bootable-ubuntu-usb-flash-drive/... my MLA-30 loop arrived last week, and I received a notification that my RTL-SDRv3 was delivered to my mailbox, which I will pick up tonight! Woo-hoo!!!!!!! Lots of stuff to do next few days, if the wife and kids will let me.First I have to download and install the latest Skywavelinux to my USB key. Then I have to build a mount for the MLA-30 from a bunch of PVC tubes I have left over from when my kids learned how to skate.It turns out I can open this up and use the T-junctions, L-corners and the 2 hinges to create a foldable easy to pack antenna mast that can extend up to 16 feet (each pipe is 2 foot long) and I have a 4 foot tripod base I can attach it to for a total of 20 feet height!

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 14, 2020, 04:29:45 pm
content: And how big are your feet?

author: edy
author_rank: Super Contributor
timestamp: July 14, 2020, 05:38:08 pm
content: Quote from: Lord of nothing on July 14, 2020, 04:29:45 pmI'll post photos of the skate-trainer antenna mast once I finish it. It may be a complete disaster.... only one way to find out!NOTE: This is not meant to be a permanent installation, it is something I put up and take down each time I use it. Inside the house I would only connect a few pieces and it would be maybe 6 feet tall facing near the window.

author: edy
author_rank: Super Contributor
timestamp: July 16, 2020, 02:06:46 pm
content: First impressions:I haven't put together the MLA-30 yet but I did have a chance to play with the RTL-SDRv3 dongle and stuff that came with it (accessories package which includes some antennae and stuff):I made myself a persistent USB key of skywavelinux 4.0 and after trying it on a few different computers I can tell you that I was not getting the best experience. Half of the apps crashed or didn't load or froze. For example, while Gqrx worked, CubicSDR didn't and LinHPSDR just stayed on the initialization dialog forever. It could be that skywavelinux doesn't like running on a USB key.Add to that the i3 Window Manager (which I am starting to like) but the key-mappings were not standard and overall the user-experience with the many crashing or half-working apps was not instilling much pleasure from booting up the key.So I decided to just install everything into my existing linux machine (Ubuntu Studio Bionic) and things went much better. I installed the RTL-SDR drivers, Gqrx (gprx-sdr) directly through sudo apt install commands, CubicSDR using an AppImage, and modified the conf files to blacklist the other drivers so that the dongle would be properly recognized when plugged in. All the instructions basically found on RTL-SDR.COM Quick Start Guide and this tutorial:https://ranous.files.wordpress.com/2018/02/rtl-sdr4linux_quickstartv2-18.pdfI had previously already installed fldigi and WSJT-X on same machine so now there is a Ham RADIO applications menu now showing up with all this stuff in it (somehow automatically ended up in there with all these apps going to that submenu).The only thing that didn't work from the tutorial is getting the Dump1090. I cloned the git suggested and followed the make instructions but there were warnings/errors that thwarted success. Even turning off the Werror flags in the Makefile didn't get me any further and I didn't have time to start debugging the code. So I may try to find another Dump1090 fork to see if I have any better luck.One other HARDWARE ISSUE that I found, which I'm not sure about... When I screw the whip antenna SMA male on to the RTL-SDR dongle SMA female, if I screw it on too much (too deep or tight) I lose reception, as if it is not plugged in at all. I tried everything from wiggling the cable, putting my finger on it, squeezing, etc. The same effect is reproducible. Basically... with no antenna attached there is basically just static. Once I thread on the antenna SMA maybe a few turns I get reception, but if I go past a certain point (SMA still easy to thread) I lose reception again....even until it finally is on tight, no reception.Is this something to do with the SMA hardware design and improper electrical contacts on the male/female? I haven't tried any other cables or antennas but this is my first experience out of the box with the whip antenna it comes with. Once it is attached properly (a few threads in but not tight) I get amazing FM stereo reception and can even see RDS music/station info. I get so-so AM reception (I use the direct sampling to get down under 24Mhz) but can definitely pick it up. And I also find some of the stronger (mostly religious) shortwave stations in the 3000-8000 Khz range on the whip.So far all these tests were in the kitchen. I'm looking forward to going upstairs and trying the long-wire antenna and higher elevation, as well as MLA-30 loop to see what differences I get.A lot of "tongue at the right angle" it seems but slowly getting there!

author: edy
author_rank: Super Contributor
timestamp: July 17, 2020, 06:48:39 am
content: I managed to mount my MLA-30 loop and plugged in the BIAS-T into my laptop USB port, and RTL-SDRv3 dongle in the other and I'm picking up tons of stations using CubicSDR to listen!I'm getting clear reception on so many SW stations.... right now I'm listening to 3990 kHz which is either in Chinese or Korean, playing music. I can't figure out where this station is... I can't believe it is in China/Korea. Do they use repeaters locally to rebroadcast? I've attached some photos of my setup and screenshot. I am very impresssed, my MLA-30 loop is on the first floor in a house in an urban area. I haven't even tried upstairs or using the longer extensions, or better yet... out in the country a bit away from the city.[UPDATE:]I tried to see how long I could get with the antenna outside today (see last 2 photos) and was able to get up to 4 segments max on top of the tripod. Each segment being 2' and tripod about 4' when fully extended it was a total of about 12'.I have another 4x 2' segments but things were starting to get really wobbly after 12' and so there is no way I'll be able to stay stable and safe at 20' just sliding the pieces together. Maybe I could push it to 14' if I really anchor one into another but by 16' it's bent over to the point of collapse or going to rip the base out of the tripod mount. Tripod is very heavy, no concern that it will topple over. If I want anything higher I'll have to go out and buy something but I'm not sure I care to at the moment.I'm using the bias T that came with the MLA-30. Next step is to try to activate the RTL-SDR dongle bias T and see if it make sense any difference. AM and FM reception nice, but I'm getting spotty reception in the SW bands (2400-14000 kHz). But I'm downstairs inside with my laptop. I should bring it upstairs and bring up the laptop or run it out to the top of a hill somewhere and see if I have any better luck.I jokingly called it "Alien Signal Telescoping Receiver Antenna" or A.S.T.R.A.Friends all think I'm crazy, they never heard of HAM before.

author: A.Z.
author_rank: Super Contributor
timestamp: July 19, 2020, 08:31:48 am
content: The loop doesn't have to be round, It may be a Square/diamond, a pentagon/octagon... so willing to make It bigger just use some plastic pipes and slide insulated wire inside them, connect the wire ends to the antenna posts and there you go

author: radiolistener
author_rank: Super Contributor
timestamp: July 19, 2020, 04:29:50 pm
content: Quote from: A.Z. on July 19, 2020, 08:31:48 amYes, but the goal is to have more area of shape. For a fixed wire length, area of circle shape has the largest value than square, diamond, pentagon, etc.

author: A.Z.
author_rank: Super Contributor
timestamp: July 19, 2020, 05:51:58 pm
content: Agreed, but a Square Is easier to build, and example; pick two pipes of say 1 mt each, build a cross and use It to support a diamond shaped loopSeehttp://www.kk5jy.net/rx-loop/

author: edy
author_rank: Super Contributor
timestamp: July 23, 2020, 02:41:08 am
content: I opened up my MLA-30 loop and it does not have an LED light in it. Also it says on the box input voltage 5-12V whereas others I've seen reviewed show an LED inside the box under the black conformal coating clearly visible when powered, and have voltage 4-14V written on outer box. Any idea if this is normal or some fake copy?I did turn on the bias-Tee on my RTL-SDRv3 and confirmed with a multimeter that 4.95V was output. As well it does make a difference when I use the MLA (with and without power). So I'm sure it's doing something but I wonder if this is simply a design change or many places are making copies of copies at this point with various PCB designs and trying to just cheapen out on parts (the LED is normally not even visible as it is inside the box).