Airspy YouLoop

Discuss commercial and home made antennas.
VE3EAR
Posts: 39
Joined: Sat Oct 05, 2019 10:13 pm

Re: Airspy YouLoop

Post by VE3EAR » Mon Jun 29, 2020 3:34 am

I tried another feed method for the DIY YouLoop today. Went with a centre-tapped 8 turn winding on the antenna side, and 16 turns on the radio side. The centre-tap connected to the shields of the loop at the feed point. Again, it worked, but it still wasn't anything to get excited over.

Time to try another antenna completely, so I built a "conventional" shielded loop out of some half inch hardline I had laying around. The circumference is 10 feet, with a diameter of 38 inches. Standard build, with a gap of a half inch in the shield at the top, opposite the feed point at the bottom. The loop shield is connected directly to the feed line shield, and the one turn loop winding is connected to a 1:2 step up transformer to galvanically isolate it from the receiver, along with serving as a balun to preserve loop balance.

Testing it this evening with the loop hanging in a tree in front of the house and connected to my DX-440 portable, via a twenty foot length of RG-58U coax. It blows the doors of the YouLoop! Very solid signals on the amateur 160, 80, and 40 metre bands, along with WWV on 5, 10 and 15 mHz. It cuts the noise big-time when I switch between the loop and the receiver's whip antenna. Signals buried in the noise on the whip, are solid copy with little to no noise on the loop!

I think I'll throw in the towel on the YouLoop! 73, Bruce, VE3EAR

JEL
Posts: 178
Joined: Wed Feb 07, 2018 2:08 am

Re: Airspy YouLoop

Post by JEL » Wed Jul 01, 2020 2:26 am

Do you have a diagram, or maybe some detailed photos, for the new loop you made?

I do have a tall tree nearby, that I wish I could 'decorate' with some wire, but the rules around here does not allow for putting up an outside-antenna, so looking for any possible alternative that can yield extra SNR :)

The loop I made myself is at lawn-level, so despite being big it is not 'up there' where it would probably be receiving much better.

VE3EAR
Posts: 39
Joined: Sat Oct 05, 2019 10:13 pm

Re: Airspy YouLoop

Post by VE3EAR » Wed Jul 01, 2020 1:37 pm

The loop I made myself is at lawn-level, so despite being big it is not 'up there' where it would probably be receiving much better.
From what I've read and seen on numerous YouTube videos, the height above ground isn't all that important. If you can get it up about two loop diameters above ground, it should work just fine.

Here's how I built the new loop. I took a 10 foot length of hardline coax (RG-8 or RG-213 will work too) and at the half-way point I removed a half inch section of the outer jacket and the shield. I applied some hot-melt glue to the area and slid a piece of old garden hose over it for reinforcement.

At each end, I removed about an inch of the outer jacket and cut back the shields about half an inch. I also removed about a quarter-inch of the inner insulation to expose the centre conductors. I formed the coax into a loop, bringing the two ends very close together. I soldered a jumper to join the two shields and to also connect them to the shield of the feed line.

The two centre conductors connect to a four turn primary on the balun. The centre conductor and shield of the feed line connect to an eight turn winding on the balun. I used a binocular core, but a small toroid core would work too. After I had checked that everything was connected correctly, I sealed the entire area with hot melt glue.

As you can now appreciate, pictures wouldn't show you much. I should have taken some while building the loop!

73, Bruce, VE3EAR

VE3EAR
Posts: 39
Joined: Sat Oct 05, 2019 10:13 pm

Re: Airspy YouLoop

Post by VE3EAR » Tue Jul 14, 2020 1:04 am

I think I'll throw in the towel on the YouLoop! 73, Bruce, VE3EAR
I couldn't let it rest, so once again down to the workshop to try something different yet again. Since I didn't have an extra
binocular core laying around, I had to make one. An old monitor cable had two cylinder-style cores on it for noise suppression, so I salvaged the pair and glued them side-by-side, making a jumbo-sized binocular core.

I wound on five turns for both the loop side and the radio side of the transformer. The shields of the loop were connected to the feed line shield, and the loop inner wires went to the transformer primary. On the radio side of the transformer, the feed line was connected to the transformer secondary.

Did it work? Yes, it did....finally! It's still outshone by the conventional shielded loop, but not by the huge amount it had been with the other feed methods I had tried. I'm going to build another YouLoop the same size as the conventional loop just to give fairness in the comparisons. As the newsman says, "Details at 11:00".

73, Bruce, VE3EAR

JEL
Posts: 178
Joined: Wed Feb 07, 2018 2:08 am

Re: Airspy YouLoop

Post by JEL » Sun Jul 19, 2020 4:07 am

VE3EAR wrote:
Wed Jul 01, 2020 1:37 pm
The loop I made myself is at lawn-level, so despite being big it is not 'up there' where it would probably be receiving much better.
From what I've read and seen on numerous YouTube videos, the height above ground isn't all that important. If you can get it up about two loop diameters above ground, it should work just fine.
It used to work, but for some reasons I don't get emails from this forum anymore, so I miss all the notifications at the moment.

Anyway, the loop I built is ~5 meters wide and 1.5 meters tall.

It's a rectangular square actually, with 6 turns.

The bottom of the square lays on the ground

And I have 2 of them set up perpendicular to each other, to cover 4 directions (Or that is the idea anyway, but one loop is feed from the bottom-center and the other from the bottom-corner, so I'm not really sure how accurate this array's behavior is to the theory behind the layout :) )

I seem to get a lot of signal (Relative to any other antenna I have tried, but I do not know if my noise-floor is as good as it could be. So far it has beaten anything else I have tried, but I am very much an amateur when it comes to antenna-design, so somebody with your level of expertise might laugh at my setup and be able to perhaps improve it significantly :)

But as you say, part of the fun is in tinkering with these things, so for now I am having fun with it :)

Anyway, what I wanted to say is that I can't get it any higher, since I have to keep it below hedge-level (HOA restrictions. If it had not been for those I would have already erected a 100 foot tower and put up a military-grade discone for HF :lol: )

I was easier being into radios in the 1980s.
I used to have a 5/8 CB-antenna with 4 radials mounted 30 feet high back then. That thing is the most beautiful antenna I have ever had and it really did vacuum the signals like it had a turbo-suction :lol:

But the loop-array has to have a very low visibility-footprint, so it is probably about as good as it will ever get here.

I do not know if a small youloop hidden higher up in the trees might work better. Perhaps it might. But come winter when the leaves all fall it would obviously become visible and so I do not really dare try something like that (I do not really want to push my luck with the HOA by beginning to do things like that)

VE3EAR
Posts: 39
Joined: Sat Oct 05, 2019 10:13 pm

Re: Airspy YouLoop

Post by VE3EAR » Sun Jul 19, 2020 12:43 pm

Anyway, the loop I built is ~5 meters wide and 1.5 meters tall. It's a rectangular square actually, with 6 turns.
The bottom of the square lays on the ground. I have 2 of them set up perpendicular to each other.
I'd say you've done pretty well, working with the restrictions put on you by the HOA. Are you using a balun or transformer to match the feed lines to the loops? Why did you not feed them both the same way? You mentioned your noise floor is some concern. Mine varies quite a lot, and as I sit here typing this message, it's about -80 dB listening to 80 metres, but it can be as good as -110 dB when there are no t-storms in the area.

73, Bruce, VE3EAR

JEL
Posts: 178
Joined: Wed Feb 07, 2018 2:08 am

Re: Airspy YouLoop

Post by JEL » Mon Jul 20, 2020 6:41 am

VE3EAR wrote:
Sun Jul 19, 2020 12:43 pm
I'd say you've done pretty well, working with the restrictions put on you by the HOA. Are you using a balun or transformer to match the feed lines to the loops? Why did you not feed them both the same way? You mentioned your noise floor is some concern. Mine varies quite a lot, and as I sit here typing this message, it's about -80 dB listening to 80 metres, but it can be as good as -110 dB when there are no t-storms in the area.

73, Bruce, VE3EAR
Thank you Bruce :)

No baluns or transformers. Just the 2 wires connected straight to an antenna-plug (And one extra separate wire going directly into the ground itself. That wire had a huge impact on lowering the noise-floor without lowering signal-levels)

I have a galvanic isolator just before the radio's antenna-input and a small surge-protector (At least that's what the ad says) just where the antenna-cable comes inside the house (The surge-protector is actually sold for satellite-TV equipment and is listed as covering 47-2500 MHz, so I'm not sure if it is useful or not. It doesn't seem to have any negative impact on the signal on any frequency. It looks just like any other filter you might put on the antenna-cable)

I feed them differently mostly out of convenience.

The one loop I could hide the cables under the lawn with, so that one I could feed in the center-bottom, which I read would make it bi-directional with equally low intercept-angles on both sides (To make it 'see' the longest possible skip-distance)

The other loop comes across a terrace paved with slabs, so to feed that the same way as the other loop would be a mess of cables. So I decided to corner-bottom feed that one instead. This way I also avoid having feed-lines running in parallel with the antenna itself.
This, I read, makes it bi-directional, slanted slightly upwards in one direction and slightly downwards in the other.

The signals I receive appear to fit with the expected directionality, so I think the theory (Reading tons of web-pages on loop-antenna design before building it) holds up quite well :)

I'm using SDR#, so I'm not quite sure how valid the noise-floor numbers really are (I get different values in SDRconsoleV3, compared to SDR#, when I set the setting called spectrum-offset (Or something like that) to zero offset. SDR# does not have any setting like that, so I'm not sure if it uses an offset or not)
And in SDR# I get one value on the main spectrum and a quite different value on the IF-spectrum.
So I tend to only focus on the SNR instead :)

Anyway, here are some values as they get reported in SDR# :
I use "Airspy HF+ discovery" for HF, and on 80m I get (As the conditions were a bit more than 3 hours after sun-rise local time) around -90 dB on the IF-spectrum and around -60 dB on the main spectrum.
2.5 MHz is the most quiet area overall. There I get about -115 dB on the IF and around -85 dB on the main.
On 9 MHz I get -90 on IF and -65 on main.
And then above around 17-18 MHz it begins to drop in both noise and signal level and I only receive close transmitters above that frequency (Local CB-stations come in strong on 27 MHz, for example)
Both noise and signal-levels (Mostly signal-levels though) vary somewhat between night and day-time.
I have to use attenuation on occasion to avoid signals from spiking above 0 dB. It is mostly AM-broadcast stations anywhere between DC and 18 MHz that, especially at dusk-time, tend to spike above 0 dB without attenuation.
Obviously some days have low signal-levels and other days have huge signal-levels.
Compared to the online 'Twente' SDR, I sometimes get better signal than it does and other times it gets better signals than I do (Which makes sense, of course, since we are not placed in the same location :) ). It often sounds less noisy than my receiver though, so I'm sure my setup still has some room for improvement.

One caveat to those values; the noise-floor has different 'hills and valleys' across the spectrum when each loop is connected independently vs when they are both connected at the same time, but mostly they do indeed seem to complement each other rather than cause any nulls.

As I said; when it comes to antenna-design I'm only a 'happy amateur' :lol:
I try to educate myself by reading what I can find on the internet, but for now I have mostly skipped the things about baluns and transformers since I don't have as easy an access to the materials needed to build such things as I do to the more generally available things like wires and cables (And also because those topics are still a bit further above my head, in terms of what it actually does and how it works, than simply laying out some wire hoping it will pick up some signals :lol: )

VE3EAR
Posts: 39
Joined: Sat Oct 05, 2019 10:13 pm

Re: Airspy YouLoop

Post by VE3EAR » Sun Aug 02, 2020 2:52 pm

I decided that more testing of the YouLoop was needed, but I wanted to start with a clean page. I built two identical loops using some 3/8 inch heliax scraps I had on hand. Both are one metre in diameter and employ the same feed arrangement, with a balun wound on a half inch square binocular core of type 75 mix. There are four turns on the antenna side and eight on the feed line side, of #24 gauge plastic insulated wire. The feed line shield connects to the antenna shields. The only difference between the two antennas is at the top of the loop, opposite to the feed point. One has a simple one inch gap in the shield, with the centre conductor passing across the gap, while the second one uses the crossover connection of the YouLoop design.

I've been running some A-B comparison listening sessions, both mid-day and in the evenings after local sunset. The testing is done outside, with the antennas hanging on a low limb of a maple tree in front of the house. The feed line is about twenty feet of coax which connects to my Realistic DX-440 receiver on the front porch. Testing is done listening to the AM broadcast band and the 160, 80, and 40 metre ham bands, with the loop aligned both E-W and N-S and about one loop diameter off the ground. Both loops work well, but I do have to give the nod to the YouLoop, which produces a stronger signal of two S-units higher than the conventional loop. It also has deeper and sharper nulls, which can sometimes produce total nulling of the station!

73, J.B., VE3EAR

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