Ham Radio - Trying a pre amp on my homebrew youloop build.

[@michaelkaliski7651]

Loops will always have a lower signal pickup simply due to the lack of copper up in the air. However loops are less sensitive to noise so although the signals are overall weaker, the interference is also at a lower level due to the way in which the loop responds. So for near to medium range signals, a loop is often the better choice over a long wire or tuned dipole. For distant stations the rule will always be the more wire up in the air the better the performance.

[@johnwest7993]

A wire antenna is almost always better at picking up signals. It's simply a matter of the much larger cross-sectional area the wire antenna has. The only reason to run a loop is if you are limited to an indoor antenna or you suffer from high noise levels you are desperate to get rid of. Then a small loop makes sense. And the best small loop is a tuned small loop, since you are reducing all other noise sources on other frequencies and *amplifying* through resonance the signal of interest. Ultimately, the best noise-eliminating antenna only receives the bandwidth of the signal of interest. Since you dislike constant tuning, (I actually enjoy it,) perhaps you can come up with a micro-controlled 'tracker' that tunes the antenna to follow the receiver tuning. That sounds like a fun project.

[@larrybomber83]

I love the idea of a small loop, so please keep working on the solution. Thanks for trying it out Kevin.

[@maikerumine]

I have had my MLA-30+ loop outside for a year and a half, it still works exceptionally well and was the BEST investment for my sdr needs to date. I would buy another in a flash, it works that well. Remember it is only for receive not TX.

[@skinnyflea2628]

I’m so glad you still have that pre amp. That was one of my favorite videos. I appreciate the videos and keep up the good work. 73.

[@joepereira3421]

Small active or magnetic loops are compromise antennas with the ability to tune out local close interference, I have tested the MLA-30+ vs 40m wire dipole and the dipole does produce stronger signals but the loop is much better tuning out local noise. Thanks for your testing very interesting :)

[@ladyattis]

Yeah prog can be a bit of a jerk at times. But I'll explain the antenna since Owen Duffy and Chris Trask have explored loop antennas (Chris Trask had a varactor tuned loop using these so-called shield loops in one paper) and the idea is quite simple. The gap whether it's a 'mobius' loop or a 'shielded' loop is the same core principle where it suppresses common mode noise due to the gap (imagine a current going the same direction on the inside and outside parts of the shield to see how this would go, Owen Duffy's paper goes into detail with this) thus it's quite good if you're in a noisy place. But the drawback is the fact you have to deal with varying impedance (usually high after LF/MF) so most SDRs are built with a 50 ohm source in mind won't do so well. A fet-based amplifier could help in taking the higher impedance and transforming it down to something reasonable but even then I'd say the ideal frequency range for such loops are in VLF to MF with some low HF (80 meters) use cases. It's not a 1-30mhz antenna by any stretch of the term.

[@loughkb]

That last point is what I focused on after seeing the claim on the web page of full HF coverage. I guess I had hopes there was some magic sauce there somewhere.

[@WaynesWorld69]

Bit of a jerk? Completely rude and unhelpful waste of space. This channel is excellent for noobs like me as far as experimenting with antennas, software and other ham related info. Keep up the great work Kevin!

[@ladyattis]

@@WaynesWorld69 I guess I'm trying to be too nice heh. But over all the concept of a shielded loop isn't bad just the implementation that prog put together for Airspy. Ideally, you're gonna try to match it to the band of interest and maybe even add a capacitor across it as I've seen some diagrams for that by W8JI. The whole Airspy spiel about it being wide band is nonsense. It's LF (possibly VLF) and MW with some low HF. I really wish they wouldn't over promise over there.

[@WaynesWorld69]

Thanks for updating your experiments with this antenna. I'm new here and in the hobby and just love the way you present information and the clear passion you have for it.

[@simonbeliveau6852]

The main thing with any loop is impedance mayching. Impedance of a small loop like this is near 0 ohms (like 2 ohms or so). If no preamp is used, the mismatch is huge with a 50h coax resulting in the coax unable to pull much energy from the loop. If using a preamp, you must absolutely use a LOW Z amplifier with an input impedance near 0 ohms too. Several designs exist which are specifically design for low impedance loops (like commmon base transistor amplifiers). Designs and products are readily available on internet. Also, the real benefit of small loops is when fighting very nasty qrm which you can null. This benefit applies particularly when you tx antenna is vertical and is too noisy to rx due to qrm.

[@BabylonLurker]

Similar experience here, but then again, I have my own rule of thumb when it comes to antennas: You can play with 3 variables: 1) Small size (compared to the wavelength) 2) High bandwidth 3) High efficiency My rule is, you can get up to two of those, but never all three. I had an amplifier with a lot of gain (and bandwidth), so I had fairly good sensitivity, but heavy overload. My idea is to make some tests with band splitting and using different levels of gain for different bands. About the Youloop being resonant: Yes it has a very broad (very low Q) resonance. My home made one resonated around 4MHz. One thing was clear, though: The loop, when mounted indoors in the noise field, had a generally better S/N ratio than expected (when overload was not the trouble. I think that the can be made to work as a decent receiving antenna, but it is not quite as simple to do as some may think. For pure monitoring I am thinking of mounting two perpendicular (amplified) loops in the house, just for having a receive antenna when I occasionally disconnect the outdoor antennas - (yes, thunderstorms etc). Vy 73 de OZ9QV

[@eduardopower5254]

Good morning Kevin, nice video! I bought the Chinese MLA PLUS be sure you buy the "+" version. Lower noise on the amp. Better response in Lower freq. 73

[@W4BIN]

That pre-amp brought up the noise floor magnificently, a pre-amp with a MMIC amplifier IC may produce less noise. The larger aperture of the EF long wire cannot be exceeded by the untuned loop, the tuned Hi "Q" loop works the same as any dipole, but it does not need much height, Ron W4BIN

[@zenpharaohs]

Tuned loop is narrow but the Youloop is not used at the resonance. Hams generally think in terms of transmission where tuning is for the operating frequency. But if you tune a receive antenna to an out of band frequency, then you are getting very smooth phase behavior in band. If you don't transmit, you don't mind the resonance being off the operating frequencies, and for receive you get an antenna that you don't have to tune. Tuning a loop to resonance is usually really tricky because it's not hard to get a huge Q so most people have to do things like gear down their variable caps or pots (if they are using varactors, etc.

[@Nicktgrief]

If you re jig you preamp box and connect a loop of wire to the terminals you’ve pretty much got an MLA 30 . I have one and to be fair for the price its pretty good. Maybe not as good as a wellbrook but you’re looking at $30 against $300. I modded mine by swapping the thin coax supplied for a BNC socket so i could use better coax, that helped, but on MW (AM) its noise floor is higher than my 120’ longwire

[@stevebailey1682]

Hey Kevin...thank you for your good videos. You have rekindled my interest in all things radio. Regarding your Youloop performance...I have some ideas on what might be happening based on your results, general magnetic loop theory, and Progs comments. Any loop of wire (including the Youloop) acts as a magnetic loop...basically it looks like an inductor. Given there is always some low level of capacitance (stray capacitance) present in any circuit (including a loop of wire), any loop on its own has some natural resonant frequency...hence why it couples with the magnetic wave of a radio signal. Based on comments from Prog, he designed his Youloop to have a particular capacitance. When coupled with his loop length results in a natural resonant frequency at probably the middle of the band (~15 Mhz). He also more than likely designed this natural resonance with low Q...meaning to all you newbies that the gain is low at said resonant frequency...which means attenuation on either side of the band is not so great...meaning although signal levels are low on the band ends, they are still present. Therefore, the Youloop is a broad band (low gain) antenna with its peak gain around the middle of the band (~15 Mhz). Given the gain is so low, one needs a receiver with a very low MDS (Minimum Detectable Signal) figure (-140 db)...which is way lower than say an RTL-SDR stick. Kevin...I am guessing your DIY Youloop probably has stray capacitance lower than the Airspy version making your natural resonant frequency perhaps much higher than 15 Mhz...resulting in more attenuation down in the ham bands where you are looking. That might explain why your preamp is not making much difference (you need a signal present to amplify).

[@HitchHiker4Freedom]

I have a Tram 1411 for my SDR and CB. It's an interesting compact antenna. Good for 26mhz up to 2ghz IIRC. Great for hams who like the upper bands. Could be tuned to rx/tx on 10 meter plus upper bands.

[@cowboy6591]

Trouble is. An amplifier will amplify the noise floor as well. This whole loop thing is disappointing me but I will study this further.

[@adrianobueno6984]

Great, thanks! BTW there is the new QRP-Labs QDX transceiver that still needs a pro review!

[@Blues2cool]

Check out a TN07 they use a matching unit it works great. I have talked around the planet. 80 meters through 10 meters

[@pd1jdw630]

For small spaces I think you’d be better off with a magnetic loop antenna. Ore a multi wound window antenna.

[@nightwriter6480]

Youloop performs perfectly for me with Airspy HF+ Discovery (that has lna built in) on Windows 10. With the original blog rtl sdr it is not sensitive enough. Even with HF+ Discovery, not all software can activate the airspy hf lna. But for Win 10 and the HF+ the performance is acceptable. My Ft8 receipts are from around 1000km away tops. I live in reinforced concrete building.

[@stevec5000]

I tried some different loops until I found the MLA-30+ Loop Antenna works well, about the same as a wire, so I stopped there.

[@kd8opi]

Hi Kevin, when you increased the preamp voltage, was that real gain or did the noise floor come up too? Personally, I think this video shows how good your EFHW is. I’d suggest that EFHW’s are reasonable stealth antennas. But if you don’t have a yard or any way to put any wire antenna up, a magnetic loop with all of its Hi-Q, low bandwidth fun, is probably the only way to go. Even so, you can forget about 40m on the commercial mag loops in terms of transmitting, the efficiency is something like 10-20%. FT8 may doable.

[@kirknelson156]

I've been looking for exactly what you said, a compact receive only antenna,.Something that doesn't require me to mount a 20 foot pole to my roof, which sounds more like a lighting rod now that I think about it. I have a classic Sony SW receiver but found its reception with the built in antenna was poor, and a SDR receiver with a telescopic antenna fared even worse. help me Obi-Wan, your my only hope ;)

[@LionRoars918]

The YouLoop works well if you use an Airspy HF+ Discovery I use it for MW DX and it works well with no preamp.

[@alzeNL]

Wellbrook ALA1530AL all the way.

[@zenpharaohs]

It is completely fine to use the Youloop passively with an Airspy HF+ Discovery and short transmission on the coax. I do that all the time. I'm doing it right now.The results you experience are a good deal worse than what I see.I agree with the maker that your antenna might have a resonance where you don't want it. I took a screen shot of 40m but it doesn't appear KZbin has a way for me to put it here so you can see. And I have the original very short transmission line from the Airspy that reaches all two meters to the loop, which is oriented horizontally six feet above the floor, indoors, in my second floor room. Now I have a nice low noise amp for the Youloop - the Nooelec LANA HF. I only need that for less sensitive receivers. You did show your amp at least amplifies, not sure about the noise figure, but from the leakage you showed it probably isn't too noisy. But if for some reason you did have a doubt about your amp you could try this one. Just make sure to get the HF model if you want it for HF. The built in preamp on the SDRplay Duo doesn't really play nice with the Youloop, but the built in pre-amp on the Drake R8 works with it pretty well. I haven't teased out why, just noticed that when I tried it. I also have an MLA-30+. Definitely get the plus version if you try that. My experience is that is a fine choice for a lot of receivers but the Youloop is quieter with the HF+ Discovery. Like you, I built my own loop, but out of copper tubing, naturally tuned (no added variable capacitor - just the gap in the loop across which the feedline attaches). I used twisted pair feedline to the Nooelec LANA HF+ and it performs more or less like the MLA-30+ but the sensitivity is not the same across the bands. With a signal generator and scope I estimated the Q of this contraption to be about 4 - 6, with a natural resonance around 13MHz. It's decent with the various receivers I have, but not as good as the stock Airspy Youloop with the Airspy HF+ Discovery. None of these seem to be as unhappy as your Youloop. I am mildly surprised since you are using the Airspy HF+ Discovery, and your amp seems to work. Makes sense for you to give up on your antenna, but my Youloop with Airspy HF+ Discovery is my first choice portable rig, and I actually use it a lot compared to other choices I have.

[@BretChilcott]

Nice video! Thank you for sharing your knowledge! 73 Bret/AC0AE

[@peterk_hh]

You cannot amplify what you do not receive. Preamps have Pros and Cons, better have a better antenna without one. Interesting test, thx.

[@ManuelPinner]

It depends on the Size of the Loop!

[@danlarson5730]

Kevin, I tried to find the video where you go over your 12V monitor with Raspberry pi. I picked one up and works great and fairly quite RF wise on HF but found on VHF it is crazy noisy if using it to power the PI. Have you run into this? Any suggestion on a good choke as I tried a few with several wraps but could not kill the noise on VHF. Thanks for doing all the experimentation. Dan KD9M

[@loughkb]

Hi Dan, No, I hadn't noticed the noise on VHF. I have my 2 meter rig on all the time, but don't recall any interference. Maybe it's the Pi itself that generating the noise? Is your VHF radio connected to the pi in any way physically?

[@danlarson5730]

@@loughkb Yes was using the IC705 connected to the PI with USB cable for digital. I was running HF then decided to flip to VHF SSB. This is when I noticed the noise and found if I unplugged the PI from the monitor it went away. When I used a 12V to USB DC/DC power supply the PI it was ok so made me think it was the monitor's DC/DC was creating a harmonic on VHF. I will have to test without the USB between the IC705 and the PI on 2 Meters. Other than that I love the monitor for small easy portable setup.

[@loughkb]

@@danlarson5730 That's the worst kind of noise to deal with. I've no doubt the monitor's power supply is not filtered at all. It's cheap and we do get what we pay for. I think you have the only practical solution figured out. Power the pi a different way.

[@danlarson5730]

@@loughkb True was cheap and works well over all. I will try a Pi filter to see if that helps but at that point I may just stick with extra DC/DC instead of using the one in the monitor. Thanks for the feedback and all your videos. Enjoy the HAM and RV and whatever new subject you create. Keep up the great work!

[@madalinbetea9871]

Hello Kevin i have 2xFT140-43 toroid.I want to build a 2 core 4:1 Guallena Current Balun for OCF dipole,if you can help me with winding details.

[@loughkb]

See my video on winding a 4:1 balun. kzbin.info/www/bejne/ombVfXxue9WAb8k

[@DAVIDGREGORYKERR]

What about the design by LZ1AQ

[@EdLeonard47]

Much appreciated! 73 N9EdL

[@LiquidCheney]

How do you feel it compares to the mini-whip?

[@loughkb]

Mini whip is better. But I'm looking forward to testing the ML30a commercial active loop also.

[@LiquidCheney]

@@loughkb Awesome, great that there is even more coming!

[@TheSillyshyguy]

Try Rotating the loop. it's Bi-Directional?

[@PaulaBean]

Youloop is a hoax?

[@flexairz]

Seems like it..

[@lambdaprog]

Engineering... Or lack thereof.

[@WaynesWorld69]

You come across as rude and completely unhelpful. Not all hams are engineers or experts in antennas. Some of us love the learning process and experimenting side of the hobby. You comment contributes nothing except criticism. No encouragement, no suggestions, no "try this" or "try that". Clearly you're the "expert" on it and like to keep that knowledge to yourself and just tear apart others wanting to try and learn. I'm completely new to this hobby but you're the first unhelpful member of the ham community I've come across.

[@joeryvilches8786]

@@WaynesWorld69 Seems to me like he maybe "selling" or "advocating" for a useless product!!!! A person that knows their product work's wouldn't criticize on the contrary they would be more than willing to help, without all the you're wrong I'm right. If this person is the owner of this design this is "TERRIBLE P.R."

[@WaynesWorld69]

@@joeryvilches8786 couldn’t agree more!

[@mr1enrollment]

Hi, I would like to correspond with you on this topic. You have a website?

[@paul.alarner6410]

maybe you should add a key to your charge controller and call cq dx! lol

[@patrickdemeyer2210]

You loop is not worth buying , i made my own loop of 2,5 mm2 electric house wire around the garden total random lenght , never had so good reception on a SDR play duo high Z input cost 0,0 .And the thing is resonant at 20 and 40 m without cutting anything , no balun , unun .FT 8 goes to 15000km.

[@cthoadmin7458]

How long (about) was your loop Patrick, and was it on the ground or elevated from the ground?

[@patrickdemeyer4668]

@@cthoadmin7458 The wire is about 22 m +- ,2,5 m above ground in a square around my small garden , no coax , straight into the high Z input of the SDRPlay DUO , the wire is resonant at 20 and 40 m without cutting , no balun , unun , nothing .at night there to much signals .Doing WSPR and FT8 rightnow , daytime , 15000km , no problem.

[@cthoadmin7458]

@@patrickdemeyer4668 I know you say you have a small garden, but have you compared the receive loop to say, a vertical at your location? or an end fed half wave sloper? Tnx for the reply, by the way...