Many thanks to SWLing Post contributor, crvee8, who shares a link to the K-180WLA, a new active mag loop antenna.
Based on the product description, the K-180WLA sounds a lot like a typical magnetic loop antenna (and resembles the popular MLA-30), but what makes it unique is the fact that it can be recharged via a Micro USB port.
This means, there’s no need for a separate power supply.
There’s no mention of how long a charged battery would power the amplifier, but I imagine it would be respectable given it employs the 3.7V 18650 lithium cell.
The frequency range is 0.1-180 MHz and the manufacturer claims it, “provides a gain of about 20 dB, even when working to 450MHz gain, there is still about 8.9 dB.”
Battery power would certainly make this a very portable active antenna loop option. The price is right, too, at $55.88 USD which includes shipping from China. The listing claims only 5 units are available at time of posting.
Click here to view on eBay (partner link).
Post readers: Please comment if you’ve purchased this antenna. We’d love to hear your thoughts/review.
K-180WLA schematic
https://ibb.co/n162NSR
where to get engish instructions?
I discovered that if you remove the cover from the amplifier there’s a small slide switch inside that doesn’t appear in Andrew’s MLA30 schematic so apparently the K-180WLA isn’t actually the same antenna except for being battery-powered as I had thought. The switch is mounted on a small circuit board atop the epoxy-covered guts of the amp. The stenciling on that PCB sayd that the up position is FM and the default down position is DX: however, this may be backwards as I’ve seen a noticeable performance improvement on HF with the switch in the up position. I’m also unable to receive my nearby airport’s ATIS on 126.6MHz with it up while I was able to with the switch down, though not nearly as well as with my homebrew airband vertical dipole made of two telescopic whip antennas connected to a chassis coax connector.
I checked the manual (which is in Chinese but does have pictures) and it shows that the switch selects between HF and FMDX modes, and it’s in FMDX by default. Remove the cover from the “alpmlifier” box and change that switch setting and I bet the antenna performs a lot better on shortwave.
Sorry to necropost. I recently bought one of these antennas from Lazada Philippines. Does anyone know whether the voltage doubler/tripler circuit is located inside the PS box containing the battery or inside the amplifier box? If the former I may try replacing the PS box with a bias-T injector board connected to a 9V battery to see if my noise floor on HF is any lower.
Thanks.
Never mind, after I commented I found the answer in the schematic that Andrew linked to below.
Did anyone try the ferrite binocular / wire winding idea between the loop and the pre amp ?
I’ve now got the bits to do it but I just want to be sure I understand where to put the wires…
If I can actually / finally post this successfully ( and god knows I’ve tried a few times now ) I’ll do it today and report back
Thanks
refer to the schematic here
https://www.g8jnj.net/activeantennas.htm#MLA30
now, the transformer wound on the binocular core should be placed between the preamp input (the twi going to the loop) at the far left of the schematic and the loop bind posts; 6 turns to the loop, 2 turns to the preamp (you may experiment with different ratios btw), as for excluding the voltage multiplier, referring to the circuit found at the same url above, cut the connections to pins 1, 2 and 4 of U1 and connect a red/black wire to the USB connector pins 1 and 5, add a standard power plug to the bias tee box and connect the red/black wire to it, this will allow to power the antenna using an external (CLEAN!) power supply (or battery) and will keep the DC line filters in place
Oh and I’d really like to hear from Vince about both the MLA and the LoG 🙂
Any news about the binocular core and bias-tee mods ?
Hi Andrew
If your still watching this space and Vince hasn’t tried the transformer mod yet I’ll be doing it next week once my binoculars and wire arrive !
Cutting the traces at C5 on the Bias tee is easy enough and I’ve an Audio grade low noise linear ps ready to go.
Hope your all still lurking around !
Looking forward to getting this done
And2
hi
This looks like the ML30+ PLUS
As mentioned in the Comments get rid of the Active NOISY Bias T and go with a Rechargeable battery pack. Consider the Low Self Discharge NiMh batteries Eneloop, Amazon Basics, and others, Transformer based Type II AC Adapters are low noise but not no noise.
Note the list of Accessories a lot more than the MLA-30. However not high-quality low noise Coax
Why an Impedance matching Transformer when the Preamps Output is 50 ohms Better yet to add some Common Mode Chokes
Note for those who use the OEM Bias T some Common Mode Chokes should help
More details can be found here:
https://m.intl.taobao.com/detail/detail.html?id=576789368315&spm=a2141.7631565.hotsell_goods_18036089441.576789368315&pvid=c65054ab-531b-423d-a32a-4b25c36514ca
The mechanical part doesn’t seem bad (although for a permanent insrallation I wonder how long it will last) and the declares freq range and gain even if possibly overrated are fine too, the problem is that there’s no noise figure nor any data about the cables used ant their characteristics; I understand that for such a price one won’t expect miracles, but some additional infos won’t cost them too much.
Also, I strongly suspect that the idea of using a rechargeable battery came as a solution for the power supply noise; my suspect is that this antenna is probably using the same (or a slighly modified version of the) MLA preamplifier
“The P.BOX feed box has a built-in 3.7V 18650 flat-head lithium battery with integrated power supply module. ”
This sounds like it’s only one battery. If this is case, the noisy voltage doubler/tripler is still being used.
The more I think about it, the more I think I’ll pass. :^)
This antenna is also available from Ali Express for a cheaper price:
https://www.aliexpress.com/i/4000739807174.html
Shipping is $47 with AliExpress!
I’m using an MLA-30 with a dollar store cellphone battery bank.
The important part is: Is the circuit different than the MLA-30? While it works, it’s not worth much more than the price charged.
One good thing I see with this new version is that the coax is not fixed to the head end. I still wished it was not an N connector (looks like).
The mounting hardware is also nice.
The price is competitive, but I wonder if the Cross-Country Wireless loop is not a better buy. For MW DXers, the new High Z antenna amp may be a better choice still. I’ll be getting one for my 160m pursuits.
http://www.crosscountrywireless.net/loop_antenna_amplifier.htm
http://www.crosscountrywireless.net/high_z_antenna_amplifier.htm
Vince, if you’ve that MLA-30 around, it would be interesting trying a small modification, that is, winding this transformer http://www.kk5jy.net/LoG/images/transformer-schematic.png on a #73 material binocular core and then placing it between the loop and the preamp input (6 turns to the loop, 2 turns to the input), see, looking at the antenna review and at the reverse engineered circuit found here
https://www.g8jnj.net/activeantennas.htm#MLA30
https://www.m0lmk.co.uk/2019/09/12/inside-the-mla-30-active-loop-antenna/
it sounds like one of the problems of the antenna is the impedance mismatch at the two ends of the 30MHz low-pass filter placed at the preamp input, now, since the PCB is totally covered with resin, and removing it would be difficult and may damage the circuit, the easier approach would be acting on the connection between the loop and the preamp, so adding the transformer shouldn’t be much difficult; all in all, given that such a type of transformer has successfully used here
http://www.kk5jy.net/rx-loop/
to directly feed the passive loop with 50 Ohm coax, such a transformer should at least allow to offer to the lowpass filter the correct impedance and may possibly improve the MLA-30 performance; sure, it will take some time do wind the transformer, disassemble the preamp unit and connect the transformer to it, but I believe it may be an interesting experiment (and then it will be interesting to hear about the result :D)
By the way there will still be the noisy voltage doubler (or tripler ?) issue, but I believe that it may be solved by cutting the power injector traces before C5 (see the schematic) excluding the voltage doubler and power the unit connecting a good, stabilized power supply there, that should cure the supply noise issue and further improve the antenna performance
Hi Andrew,
The transformer between the loop and the pre-amp is a good idea to try.
I have both #73 material binocular core in 202 and 302 sizes. I want to try KK5JY’s version of the LOG. Just waiting for the snow to melt and the temperature to go up, in addition to time. This is also the mix for the generic Youloop antenna, a.k.a. NCPL here on the forum.
I replaced the original MLA-30 power unit. I’m using a standard power feed with a linear 12 VDC supply. This improves low frequency usage. Lower MF and LF were totally obliterated by the noise generated by the original power unit.
I just received 3 meters of 6 AWG copper cable. This is for a new loop, just waiting for the end terminals.
Next on the list are adding a CMC on the output of the pre-amp, installing an F type connector on the pre-amp box, and replacing the coax cable.
I don’t regret purchasing the MLA-30, but people must be aware of its limitations and shortcomings. Not everybody is able and willing to modify it.
I still think that for a little more the Cross-Country Wireless loop amplifier may be a better option.
As for the new K-180WLA, I’m definitively not buying one.
Hi there again, Vince !
> The transformer between the loop and the pre-amp is a good idea to try.
Maybe it won’t have the desired effect, but given the impedance mismatch at both ends of the lowpass input filter, I believe it shouldn’t hurt and possibly allow to linearize a bit the impedance of the antenna and, in turn, improve the preamp performance a bit
> I have both #73 material binocular core in 202 and 302 sizes.
they should work, otherwise you may go for the original FairRite #73 core, but looking at the specs, the Amidon ones seem to be a bit better suited, as for the LoG, I’ve built a number of those for myself and friends, all I can say is that it’s an antenna you need to hear to believe, just as a note, read the first reply to this forum discussion
https://forums.qrz.com/index.php?threads/anyone-have-experience-with-loop-on-ground-receive-antenna.595179/
the folk went on and built two LoGs and the larger one seems to be the winner for MW/LW listening (although I still prefer the original smaller design), anyhow, in case you want some hints and infos about builting and laying down a LoG just ping Thomas (herein I authorize Thomas to give you my “grayhat” email address :D)
> I replaced the original MLA-30 power unit. I’m using a standard
> power feed with a linear 12 VDC supply.
Yes, the power supply uses a really screwed design, I understand that they probably did that to keep the costs down and use a cheap charger, but the voltage doubler (or what it is) introduces a whole lot of noise which, for an active antenna is a BAD thing, my suggestion to cut the traces was mainly to allow keeping the original box and bias-T while totally excluding the voltage raiser circuit so eliminating the noise it generates
Anyhow, as I wrote, if you’ll go on and try the transformer between the loop and the preamp, I’m really curious to know the results of such a modification, so if possible drop me an email if/when you’ll run that test
Vince, any update on the transformer idea for the MLA30 and also, did you build the LoG ?