Ham Radio - The Hula Loop active RX antenna

[@larrygrigar3793]

4 years ago and this is still a great video. I built one after watching your video.:0)

[@bob4analog]

Great demo of your loop. If it works that good in your house, i can only imagine how good it'd work outside!

[@LarryDeSilva64]

Just found your channel looking at a Friends channel who was going to make your hula loop antenna thought i would come over and subscribe. I'm studying for my general class was a novice back in 1967 getting back into it after all those years. Thanks for sharing

[@loughkb]

Welcome back to the hobby Larry. Good luck on the test.

[@LarryDeSilva64]

Thanks my old brain cells are still having trouble but i'm 67 . I have been restoring old amateur radios on my you tube channel . I am currently working on a BC 348Q just finished a R-336/GRC-26 from ww2 and it works fine in the ham bands.

[@SDR-DXobserver]

Kevin, as we all noticed the gain is increased by the loop, but the S/N is still the same compared to the miniwhip, so there is no usable benifit when using a decent sensitive receiver on LW/MW and HF. Have both types of antenna in use and use the loop to stir away from qrm and listening to frequencies above 10 mHz as the miniwhip is producing less gain when higher in frequency. When using a balanced amplifier the base noise will be lower so the S/N is increased. Usin a good low noise amp and perfect balance between boths amplifiers is obligatory to obtain good results. Good luck whith your experiments. 73'

[@KenWiggerAnotherAncientGamer]

I enjoyed your loop video. I recently picked up a W6LVP Magnetic Loop a few weeks ago and put it up about 20 ft on a Channel Master rotator and use it as my receive antenna on my ham station while using a 132 ft Carolina Windom antenna for transmit. I really have found a tremendous difference in noise after going to a loop. The W6LVP will null effectively noise or interfering signals perpendicular to the loop. My personal experience is that it has a very tight null of just a few degrees. The null is incredible, but aiming at stations the peak isn't that sharp which is why some people just place the antenna where it nulls the worse noise source and just leaves it there. But with a rotor you will find that noise source direction varies by frequency and time of day. But usually there is a main direction that is the worse. I also have a Timewave ANC-4 Noise reducing device that works great in combination with either antenna when fighting noise that is not nulled out by the loop because I am using the loop at times to pick between stations in different locations on the ham bands and also BCB stations on the exact same frequency. I have a 12 ft noise dipole at 3 ft above the ground for the ANC-4 that I placed right under my electrical power line pole. The combination of a W6LVP Magnetic Loop and the ANC-4 has allowed me to enjoy listening to Shortwave like back in the 50s and 60s before all of the electrical environment issues we face today. 73s WD9GNG

[@loughkb]

Yep, loops are great receiving antennas!

[@benoitmangin8948]

Hello Kevin, What could you say about the LF/MF performance of such a setup ? Did you try something ? Plus, how do you cope with the potentially brutal impedance mismatch between the loop output and the preamp input ? 73, DE F8GRY/Ben

[@waynedavies3185]

You made a fan-loop antenna on a cross-diamond like frame, and a triangle pick-up coupling loop to feed your receiver, would a signal amp. connected to the coupling loop, do equally as well in gathering more gain from that type of antenna? Do you understand what I am asking? Of course this will be a receive antenna only.

[@afleak]

would have been interesting to compare the loop pre and post preamp

[@loughkb]

I'll be doing more experimenting with it. The mini whip is amplified, so it was apples to apples, mostly.... ;-)

[@terryglenweaver]

Yeah... What he said

[@KA4UPW]

Did you make a video chasing small signals?

[@ВасилийПу-м5л]

For proper comparison of two antennas you would need to switch antennas between antenna inputs. Right now it is not clear if both antenna inputs have the same sensitivity.

[@TalmidAndy]

I know that this is six years old but It would have been interesting to see you rotate the loop, which is directional, to see what the signals were like in the nulls or what effect making it a two-turn loop would have been.

[@dambuster6387]

Hi I have built one on the same lines but looks smaller than yours with a matching transformer on the input and output of a push pull amp. Used it in doors then placed it at the bottom of the garden on a 20 ft pole made a about 3 to 4 s points improvement in noise reduction. its a copy of the Wellbrook Loop From the UK called the Wellgood Loop which I found on the web including the circuit.

[@AtomicElectronCo]

Is there a schematic for that preamp? Really looks great. I'm out in the desert in Northern AZ and I'm sure I'd get nice reception here.

[@freepcb]

I guess I am repeating some previous comments, but when you are comparing active antennas, it doesn't make sense to compare signal strength, since that will depend on the gain of the preamplifier. If you are using the miniwhip that I am familiar with, the preamp doesn't have any gain, it is just an impedance converter. The hulaloop has a preamp that probably has significant gain, at least 20 dB, so that is the difference that you are seeing. If you added a 20 dB preamp to the miniwhip, it would have a stronger signal than the hulaloop. The point is that you can't just compare signal strength, you have to look at signal-to-noise ratio.

[@jmgerstlauer8825]

The only relevant parameter is SNR!!

[@BarefootBeekeeper]

Impressive comparison. I don't seem to be able to find that antenna pre-amp anywhere, though (UK). Is there an alternative?

[@donnyknows6346]

Apart from the added performance of the signal amplifier, I am wondering if the loop shape works better than any other shape, example, a square, triangle or just a straight wire.

[@Jimwill01]

Interesting! At the Mena Hamfest I picked up a MFJ 1020B Active Anetnna! Haven't used it yet but thought about trying it on a cheap SW portable I have (in a drawer somewhere). It does require external 12 volts, but that's not really a problem. Jim KF5AQF

[@loughkb]

I've read good things about that antenna in the past, somewhere.. The only down side is that the amp also amplifies unwanted signals. You have to keep it away from noise sources.

[@ladyattis]

So I tried out the amp on my shielded loop project and it doesn't seem to be working well, no idea why (note: I'm not even a HAM, just someone trying to learn this stuff for fun). I was using a 1:1:1 balun setup (BN43-202 core with 6 turns CT for the loop side, 6 turns on the amp side with one connected to ground and the other to the capacitor), I'm not sure if the balun helped. I just used it for my MMIC amp project which it did kind of help regain directionality of the loop but it still had the flaw all MMICs have (they're too sensitive to broadcast stations nearby which it seems the FM stations are VERY strong here in downtown Minneapolis).

[@kc2mxh]

Hi Did you try this antenna on 80m band? It seems very i teresting. I use a 80m dipole on a very noisy envirlment in Costa Rica with an S9 noise level. Wilk it work on 80m? Javier TI2JS

[@az_pit_viper4270]

Is there a website where I can get the build plans for this antenna? Also, how well will this work as strictly a receiving antenna for an HF 10-80 meter rig?

[@DeeegerD]

Nice. How does it work without the preamp vs the mini?

[@loughkb]

I'll be playing around with it some more. Without the pre, multiple turns, 1:1 current balun at the coax connector, etc. Throw one together!

[@DeeegerD]

I'll be looking for one at Walmart lol.

[@stevenaustin2860]

can you use a ordinary pre amp with the rx antenna and great video because i get a lot of noise tried torroids everythink so im going to try a recieve antenna because i have one one the back of my icom 756 pro 3

[@unklewink]

Two questions, Kevin: 1. You say the preamplifier is powered through the coaxial cable by a bias T. Looking at the schematic of the W7IUV preamplifier shows a separate DC connection point. How did you accomplish the bias T connection? 2. Also, it specifies the input impedance as 50 ohms. Would you not get better results with a higher input impedance amplifier when feeding it with a loop antenna?

[@loughkb]

The center of the coax connection goes through the choke to the B+ for the amp. The output of the amp is capacitively coupled back to the center of the coax. The cap isolates the DC. And maybe you would get even better results with a better match at the input, but it does pretty darn well as is. I wasn't even running the amp at full gain, I was only feeding it 4.7 volts from the SDRplay. At a full 12 volts, it would have been even hotter.

[@unklewink]

Thanks, Kevin. I just discovered your 4th of July video that clarifies the D.C. question. As far as the input impedance, it might be interesting to experiment with a ferrite transformer; maybe a 3:1 for starters. If nothing else, it would restore the balance to the loop itself.

[@brianmartin7964]

What kind of a loop antenna would be good for a mobile home park? Something I can put up and take down. (low cost)

[@loughkb]

Magloops are easy to build. You do have to retune them often if you move frequency a lot. Even when QSYing within a band. They're very narrow, but they work pretty well.

[@jeff-73]

Thanks for mentioning about local broadcast towers. I am making one and would of though my attempt was crap living by 3 of them. Would the twisted wire do something negative with electricity though? I think in ethernet cables wires are insulated AND twisted inside to prevent cross talk. I returned a roll of wire thinking this. cheers and thanks for the vid... you explain things well enough for even stupid people like me can follow along 80% of the time.

[@loughkb]

All of the wires are tied together, acting in unison as a single conductor. There's no difference in potential between them, so there's nothing to interact.

[@jeff-73]

@@loughkb thanks!

[@ericjohnson8482]

I am looking at putting an antenna on my 20 ft light pole to run my old Zenith shutter dial radio. How does something like this work on the lower end of the AM scale? like 1000khz ?

[@loughkb]

Not too well. You would need to use light gauge wire and do 15 or 20 turns to get sensitive down that low.

[@anthonycosta1776]

Excellent presentation, I am not skilled with electronics , can you recommend a good pre amp I can purchase. I would greatly appreciate that. Thank you again.

[@paulschmolke188]

Any details on the preamp circuit?

[@mrz80]

www.mtmscientific.com/preamp.html

[@tglenn3121]

Is there a parts list / schematic diagram available for the circuit board?

[@loughkb]

There are several versions of this pre amp out there. If you search for "w7iuv pre amp" you should find several sources.

[@tglenn3121]

Thanks.

[@MindaugasMacijauskas]

But... doesn't this antenna need tuning capacitor? Currently I'm looking for antenna options for myself and I stumbled upon loop antennas, since longwires/dipoles requires a lot of space and height (both are quite limited for me). But idea about tuning the antenna every time I want to change bands on my SDR is not very compelling.

[@loughkb]

You could set it up with a tuning cap, but for receiving, that only has the effect of reducing signals outside of the tuned section. Tuning a RX antenna won't get you any more signal than the antenna can provide. As is, it's broad banded.

[@robertdimuzio1585]

Kevin, where can I buy the preamp ready made. References on line point to kits which I am physically unable to build. I am new to ham radio and just bought the rsp 1A with SDR Uno V1.3. Sadly it' all greek to me. I really need a users manual written for "dummies" so I can at least hear/search for signals. Any help would be greatly appreciated. Greg D

[@hobbified]

There's options out there. LZ1AQ sells a preamp that's specifically designed for small loops that you can get *almost* fully built (you just have to put the amplifier board into the enclosure, and provide the controller board with its own enclosure and some switches or jumpers to set the mode), or there's the DX Engineering RPA-2 which is a really beautiful Norton amplifier.

[@nsoter1]

Hi Kev, thanks for a great video. I am in the process of building this antenna and the preamp, any chance you could let me know what the value is, of the inductor used to feed the power via the coax. Thanks in advance.

[@loughkb]

Anything above 180nH should work

[@stevebailey1682]

Hey Kevin...you mention you are using the bias-t from the sdrplay (RSP1A?). Looking up specs on your preamp it looks it needs ~12 volts to operate, but the RSP1A only puts out 5 volts for the bias-t. Thoughts?

[@loughkb]

It still operates at the lower voltage, just doesn't provide as much gain.

[@stevebailey1682]

@@loughkb Kevin....do you have a schematic showing the DC coupling from the bias-t to the preamp power rail? You mention a decoupling diode and a choke.

[@stevebailey1682]

I meant decoupling capacitor.

[@loughkb]

@@stevebailey1682 It's a common design. A capacitor to pass the rf and block the voltage, a choke on the power in to block the RF. This article has an example schematic. www.hayseed.net/~jpk5lad/K5LAD%20Memories/Vols%2031-35/Memories--Vol33.htm

[@stevebailey1682]

@@loughkb Thanks very much Kevin!

[@peterlosangelos4108]

What is the frequency range of preamp? Is it possible to receive multipl bands with the same preamp?

[@Dazzwidd]

Well he went from 4.5 to nearly 8mhz and it was pretty good. I'd say it would be good from 3-30mhz and even beyond. It may even receive well down on 160m. I would try it anyway

[@stevebailey1682]

Hey Kevin...what size choke are you using on your preamp board (W7IUV design)?

[@marc_frank]

What does the radiation pattern look like? Or recieve pattern XD Does the diametre make a difference? If yes, would it work on Gigaherz wavelengths equally good?

[@loughkb]

The pattern around a loop looks like a doughnut. And no, it wouldn't work well that high up, too big. You could make a loop for microwave and up, but it would be much much smaller. Maybe about the diameter of a nickle.

[@davidnachbaur6805]

Can you bypass the amp? Or is it needed to make it work? I built one. With the w7iuv preamplifier. But if I shut the power off to the preamp. The loop will not work.

[@loughkb]

Yes, you could bypass the amp. You could use a switch. Just put a small cap like a .001 disc ceramic cap in series so you don't burn out your power supply by accidentally feeding it into the loop directly. The reception would be weak though.

[@gregorgman]

Kevin, I do SWL only, no Ham. Would this work with a radio for general coverage like a Tecsun PL-880 ? AM,FM,SW, LW, MW, SW-SSB? Thanks, love your channel.

[@gregorgman]

@@lysippus oh, thanks, didn't catch that.

[@edbeckerich3737]

Isn't the Hulaloop directional??

[@loughkb]

A little bit, but it didn't seem to be as much as my magnetic loop. I'll be doing more experimenting with it.

[@bbolin711]

Recently started with the whole SRD thing. Got an rtl-sdr USB stick and using CUBICSDR also. Right now just using stock antenna. How are you switching between antennas? Using Linux for my desktop

[@loughkb]

The soapy module for the SDRPlay has built in support for switching it's antenna inputs. Cubic recognizes that and adds menu items for switching. You won't see those menu's since the RTL doesn't have that capability.

[@bbolin711]

Are you running CubicSDR on Windoze or Linux? I've been using CubicSDR on local Linux desktop with the RTL-SDR plugged in and also with CubicSDR local with RTL-SDR running on ODROID-C2 (Ubuntu server ARM) running SoapyServer. Nice to have the tuner/antenna plugged in somewhere else. Love SoapyServer... SDR Touch (android tablet) isn't happy with it had to use rtl_tcp

[@loughkb]

All my machines run linux. No windows here. I worked in I.T. for 30 years, I've had enough of windows and osx. I used to tell people, I fix computer problems all day long, I just want to use my home machines, not have to fix them as well.

[@bbolin711]

Kevin Loughin Ditto. B4 Google existed or default GW because networking didn't exist. Unix admin. Isn't it fun when the contract ends and one day your apparently to old to hire

[@MauriatOttolink]

Before you said it, I reckoned that loop would be much quieter..better S/N ratio than the mini whip.

[@waynedavies3185]

Make note, that some SDR dongles don't support using an active antenna.

[@loughkb]

In the case where the SDR hardware doesn't provide a bias voltage, you can just build a bias T to go between the SDR and the antenna.

[@dave_yeg8596]

What's the inductance look like?

[@loughkb]

This was a long time ago and it's been dismantled since.

[@ladyattis]

Nice, I've been looking into using the w7iuv as a preamp for a loop after having middling success with an MMIC based amp (FM broadcasters are just incredibly powerful here despite the towers being at least 10 miles away from me in downtown Minneapolis). I've done m0ayf's amplified loop (it's based on an earlier version of the same amplifier done by another HAM in the 80s apparently) and it works well but this makes me want to try out the w7iuv more since it seems simpler to construct by comparison. Just a dumb question, do you think a 1:1 transformer in this situation would be decent if I used a "shielded" coax loop instead of a regular wire loop?

[@FXGreggan.]

Which transistor are you using? Apperantly there have been many revisions to the design so there's not just one schematic...

[@loughkb]

Sorry, I don't remember. The device is currently up in the attic and it would take some effort to get to it. (I have a bad back). I think the different rev.s probably used the same transistor, it was common in RF pre amps.

[@blacksmock445]

@@loughkb The 2N5109 or 2N3866 are specified, mainly because they were designed for CATV systems up to the low UHF region, where intermodulation has to be kept to a minimum. The same reasoning leads to their use as the emitter follower in the Mini-Whip antenna. If you don't have any strong local BC or FM stations locally you could always try other NPN transistors as long as they can dissipate the power and work at rf. I recently built a Mini-Whip and substituted a 2N2222 for a 2N5109. There is intermodulation, the main product occurs at 360kHz as here, in Southern England, I can receive strong LF signals on 198kHz (BBC) and 162kHz (carrier with no AM from Allouis, France) The French signal formerly carried France Inter but now has only phase-modulated data. Apparently the French Railways rely on it for time signals.

[@KB9BVN]

Kevin...would this loop RX antenna and pre-amp work well on an AM crystal receiver?

[@loughkb]

No. A crystal receiver rely's on the power coming from the antenna to drive the earphone. You would have to take out the preamp. I don't know if just one turn of wire would be enough of a loop for a crystal receiver. You'd need 5 or more turns to get down there in frequency and get any volume out of the receiver earphone.

[@jeff-73]

Love the Tardis!!!

[@kellypaws]

Kevin, really like this video. Did you ever use this antenna on HF SSB? I gace rampant QRM from neighbours and one of these seems like a good answer.

[@johncliff5417]

Hi Kevin, Interesting video of the Hula Loop rx antenna. I knocked up a twin transistor pre-amp for an sdr Rx that I built a few years back, so may give that a try out on a Rx loop. I know that the pre-amp works and is not too noisy so concidered it should work. I have very restricted space here for antennas. So loop antennas seem to be favour of the day here. I keep my eye on your videos for any tips about them. so 73 and many thanks de John-aka-G0WXU

[@caulktel]

Kevin, what is the diameter of your loop? I bought a Hula Hoop that is 34.5 inches across, seems too small to work. This is what I'm building and they say to make the loop about 60 inches. www.qsl.net/m0ayf/active-loop-receiving-antenna.html#Circuit_details_and_constructional

[@loughkb]

+Joel Caulkins oh, any diameter is going to work, the freq range of best sensitivity will change. I've found that this nearly 3ft loop starts falling off a little around 3mhz and down

[@caulktel]

Kevin Loughin Okay, thanks Kevin. I decided to build the same preamp that you did, so we will see how it turns out. Ordered some type 75 toroid cores and some 2n5109s from Diz.

[@caulktel]

Kevin Loughin Hey Kevin, I finished my Hula Loop yesterday and it works great. Last night I was listening to all kinds of stuff. Thanks for the video.

[@caulktel]

Hi Kevin, I enjoyed your video. I realize that this loop is pretty broad band, but does it have a specific bandwidth, like would it do well at 80 meters for instance?

[@loughkb]

Yes, it's very broad. It does cover 80 pretty well, but starts dropping off below 80. In the 80 meter band, it was still stronger than the mini-whip. But around 2 Mhz they were even and below 2 Mhz, the mini-whip was doing better. I think it the loop were three to four turns of wire, it would drop right down in freq. I'll be experimenting with it more.

[@MnACreations]

Just an FYI. I sent you an email to the address that is listed on QRZ.

[@philipchandler330]

What a great idea!!!

[@MubarakNour]

You R Great

[@jdmeaux]

You sleep about like I do. Three or hours hours at a time. You need to do a video on the pre-amp and explain it more. Moe K2JDM

[@loughkb]

Hi Moe, I did talk a little bit more about it on a previous video where I used it with my junk box magloop. It's a very popular circuit with lots and lots of reference material and re-designs out there. I could do one if there was enough interest though I suppose. Here's the other vid where I used it on the junk box magloop. kzbin.info/www/bejne/hau2ZYtsjspnnMk

[@jdmeaux]

I knew I missed something.

[@kcroach7747]

kermit the frog ........is that you !!!!

[@efrenredondo6896]

you have to peel the skin of loop ,is very important ¡¡¡ """ your loop is a box of Faraday"""

[@giovannimotta9176]

No, the tape is some sort of mylar. It's shiny but not metallic.

[@Dazzwidd]

There's a break at the bottom so it wouldn't make any difference anyway even if it's aluminum foil

[@cowboy6591]

I abandoned SW listening because of the religious zealots that took over all of the stations. I got so sick of that.