HFU HF Underground
Technical Topics => Equipment => Topic started by: JustGreg on February 07, 2022, 2319 UTC
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I have been looking at various small antennas. Soon to be 72, I know a change will come in the future that will not allow me to have an outside wire antenna.
I have looked at the MLA-30, which is Okay if one wants to listen to shortwave broadcasters. I tried the "mini-whip", which is an excellent antenna for listening to electronic noise. When I got my AirSpy HF + Discovery, I also got the YouLoop.
Using the YouLoop even with the HF + Discovery, it was clear that a preamplifier was needed. I tried several ideas such as increasing the loop size. The larger loop size was a help but a preamplifier was needed. Going through my radio stuff, I did not find a preamplifier that did the trick.
For another other idea, I purchase Nooelec LaNA preamplifier. Another idea bit the dust. This week stuck in the house due to the cold weather and COVID, I decided to try the YouLoop and the Nooelec LaNA preamplifier.
I was pleasantly surprised to find they were almost as good as my outside wire antenna in limited frequency ranges. The YouLoop/LaNA work well from about 1 to 4 Mhz and in the FM broadcast band up to about 106 MHz. I used 2 meter pieces of
cable for the loop elements, which are long and reduced the VHF performance. The longer cable elements did help in the lower bands.
The YouLoop/preamplifier in the 1 to 4 MHz range produces signals that are clearer due to less noise pickup and a lower noise floor. Over the rest of the HF band, the wire is better. But for listening to shortwave broadcasters, the YouLoop/LaAA is usable up to about 12 MHz.
It seems to be hit or miss above 12 MHz. I am not sure what is going on. I tried using an antenna analyzer to determine the impedance of the YouLoop by itself as function of frequency. I got inconsistent results, especially above 12 MHz.
I now have a good small antenna for listening in the house. Below is a picture of the YouLoop and preamplifier on a wooden frame. The loop dimensions are 48 inches wide by 45 inches high. I hope this is a help for others.
(https://i.imgur.com/XxqrpVM.jpg)
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Thank you for the wright up on the YouLoop and pre-amp. I had been considering ordering that pre-amp from Nooelec for some time now to compliment my YouLoop but have never gotten around to it. I have both the Nooelec Flamingo AM and FM notch filters and have been pleased with them. Same with the YouLoop.
My method of mounting is far less sophisticated. All I use is a string between the top and lower couplers. This allows me to hang the antenna pretty much anywhere as for example in a window hanging from a curtain rod. The weight (pull) from the feed line keeps things taught and the the string between the couplers keep the loop formed.
(http://www.milspec.ca/board/img/youloop-string-mounting.png)
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An "Oh By the Way" on the Nooelec LaNA, there is no noise figure specification for it. I have attempt to get an ideas of what the value is. My guess is somewhere between 6 and 10 dB, which is fine for HF work. I have been doing several different experiments and the wood frame does help. Yes, my initial use of the YouLoop was hanging it on a wall with some cup hooks into the wall board.
Last night, I used it for Undercover Radio on 1720 K. The YouLoop/LaNa was better for the station than the wire.
My next step is to try AirSpy preamplifier, with a noise figure specification on .75dB. It also covers a wider range (50 KHz to 4 GHz). It should be here by the weekend. I will post the results after the weekend listening.
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I see that their preamps are manufactured by Uputronics. You can get further data here:
https://store.uputronics.com/index.php (https://store.uputronics.com/index.php)
I cannot find this 50 KHz to 4 GHz AirSpy preamp you are referring to.
The only similar product which I can see is one with a frequency range of 100 MHz to 4 GHz which will not cover the HF band. AirSpy has is listed as Wideband 0.1-4 GHz Preamp which in reality is 100 MHz to 4 GHz.
From the AirSpy web site: https://v3.airspy.us/product/upu-fpwb/ (https://v3.airspy.us/product/upu-fpwb/)
From the Uptronics web site: https://store.uputronics.com/index.php?route=product/product&path=59&product_id=102 (https://store.uputronics.com/index.php?route=product/product&path=59&product_id=102)
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My mistake on frequency range. I confused the LaNA low end with UpUtronics amplifier. Oh well, I will try to it see how it works for FM broadcast and NOAA stations after I get it. Thanks for the information on the data sheet. I have it.
Just checked the data sheet and it lists 0.1 MHz on the low end. So this weekend, I will be testing the UpUtronics. Hopefully, it will be better. It is almost twice the cost of the Nooelec LaNA.
On Nooelec LaNA, I had to get mine with a case from Amazon. The Nooelec store does not list the version with the case.
Thanks for the help ~SIGINT :D
~SIGINT was correct. There was a typographical error on the datasheet. The low frequency is 100 MHz (0.1 GHz). I told the manufacture of the error on his datasheet. Hopefully, it will be corrected.
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If an e-field probe - i.e. an active miniwhip - returned mostly electronic noise, then you are likely testing these antennas in an EMI/RFI-rich location. No preamp is going to help. In fact, most will make it worse, especially with these various untuned small fractional-wavelength antennas.
Getting an antenna even just a few feet outside and/or above your residence can dramatically improve SNR.
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RobRich, thanks for the information. I am not using E field sensor (active mini whip). I am experimenting with the YouLoop, which at MF is small magnetic loop. I have just completed an EMI source hunt through out the house and have found them (most were small USB chargers or LED lights). I took the appropriate measures, either replace them with a better low noise charger or make sure they are off or removed from the power when I listen. The remaining sources are located on other properties.
Once interesting one is my neighbor's solar panels on their roof. The DC to AC converters are very noisy in MF/HF region. The noise is on powerlines and can be heard under them for about a 1/2 mile. The good news is at my wire antenna location is far enough away so this source is not an issue.
I do agree with an additional preamplifier will not help any of the E-field type antenna, which always seem to pick local noise sources. This is me trying to get the best performance out of the YouLoop.
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This has been an interesting experiment over the last two weeks. Here is what I found out.
The YouLoop with longer elements does work. But, one needs to have a low noise receiver. For most HF receivers, one will need
a low noise preamplifier (noise figure < 2 dB).
I found the YouLoop with a preamplifier was best from 1 to about 4 or 5 MHz It was OK for general purpose broadcast listening from 5 to 15 MHz This is not the antenna for weak HF signals. The aperture area of the YouLoop is not that large and limits performance. It is a small magnetic loop.
I did find the YouLoop with a preamplifier was better for medium wave AM broadcasts than my wire antenna. It works OK in the VHF FM broadcast band. For FM broadcast stations, it is about equal to a 29 inch whip or commercial
folded dipole.
I tried the Nooelec LaNA and generic Chinese one. Both use a RFIC gain device and have similar performance. I found powering the Nooelec LaNA through its USB port by a USB charger. The USB charger introduced broadband noise into the LaNA and reduced its performance. The Nooelec LaNA also needs a DC block on its output when powered through the USB port. The generic Chinese one with a 12 volt "wall wart" does the job.
For its price, the YouLoop is worth it. Yes, you need to add a preamplifier, but you can get a decent one for less than 50 dollars. The total cost is close to that of MLA-30 loop and one gets better performance in my humble opinion. Yes, both loops have limited HF performance. I will keep my YouLoop combination and connect it to my Malachite DSP SDR for listening to the AM and FM broadcast stations.
Who knows, maybe the weather will give me a brief power outage and I can find out how it works in a lower noise environment.
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I was going by the comment: "I tried the "mini-whip", which is an excellent antenna for listening to electronic noise." ;)
I use active miniwhips, but they are away from the house and RF grounded.
I have used the YouLoop with an antenna tuner to improve the match with a portable receiver, thus improving the usable signal transfer enough to not need a preamp. Also the tuned circuit can serve as a passive preselector.
https://www.hfunderground.com/board/index.php/topic,71326.msg241978.html#msg241978
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Thanks RobRich for the information. Yes, I agree with using an antenna tuner or matching device with the YouLoop. I tried my MFJ Versa Tuner (MFJ-941D) with YouLoop. I found I could not match to the YouLoop. One frequency, I did get a match to 2.5 to 1. It was CHU on 3330 KHz. The signal of CHU was improved a bit. I found the noise floor dropped and signal increased. It was an improvement, but not as great as I hoped. I see you used a simple LC tuner. Good idea, simpler things sometimes work better.
Your antenna measurements are similar to what I found with my antenna analyzer.