Tag Archives: Roelof Bakker PA0RDT

Don Pushes Portable Antennas Further: Loop Size, Performance, and Real-World Limits (Part 2)

Many thanks to SWLing Post contributor Don Moore–noted author, traveler, and DXer–who shares the following post:

Two Portable Antennas for Remote DXing (Part Two)

By Don Moore

Don’s traveling DX stories can be found in his book Tales of a Vagabond DXer [SWLing Post affiliate link]. If you’ve already read his book and enjoyed it, do Don a favor and leave a review on Amazon.

In my initial comparison of the PA0RDT mini-whip and the MLA-30+ MegaLoop, the mini-whip performed best on medium wave and the lower shortwave bands, while the loop worked better on the higher bands. But, I wondered, why should the MLA-30+ be restricted to that small steel loop? The wire loops I use with my Wellbrook ALA-100LN typically range from twenty to fifty meters in circumference.

I threw a twenty-five-meter wire over a tree branch and formed it into a delta with the MLA-30+ in the bottom center. Remember, I was testing in the northern Chicago suburbs. My SDRs were completely overloaded. Medium wave was useless and I had strong MW stations all over the shortwave bands. The MLA-30+ doesn’t have the same strong-signal handling capabilities as the Wellbrook. And there are a lot of strong medium wave signals in the Chicago suburbs.

So I took that wire down and replaced it with a loop of twelve meters circumference.

That did the trick. I had lots of signals on medium wave without the overloading. Here’s what the upper end of the MW band now looked like with the MLA-30+.

For comparison, here’s the same wire loop using the Wellbrook ALA-100LN. The Wellbrook has a slightly lower noise floor but otherwise the signals are about the same.

Out of curiosity, I replaced the Wellbrook power unit with the Bias-T from the MLA-30+ but left the Wellbrook antenna head unit in place. With this hybrid setup there’s no visible difference with the full Wellbrook.

I was satisfied with my findings but I still wondered how much wire the MLA-30+ could handle. A few weeks later I ran some more tests in Kansas, where I knew the dial wouldn’t be as crowded. The MLA-30+ easily handled a 25-meter delta loop without overloading.

Two weeks after doing the Kansas tests I was at a DXpedition in rural western Pennsylvania. The MLA-30+ worked fine with a 40-meter circumference loop, other than being a tad noisier than the Wellbrook with the same wire. So how much wire you can use with the MLA-30+ components depends on how strong your local medium wave stations are.

Findings

From the SDR images above it would be easy to conclude that with the right length of wire an MLA-30+ is just as good as a Wellbrook ALA-100LN even though it is significantly cheaper. But that’s not the full picture. Back in the 1990s my Drake R-8 cost about three times what my Sony ICF-2010 did. All other things being equal, I would say that 95% of the DX heard on the Drake could have been heard equally well on the Sony. I wanted the Drake for the other five percent.

I have no doubt that if I did a very careful head-to-head comparison of the two units under serious DX conditions on the same wire that the Wellbrook would get things the MLA-30+ couldn’t. But I suspect the difference would be around that five percent mark. I’m willing to accept that tradeoff for an effective cheap light-weight travel antenna. And the MLA-30+ is like having two antennas in one. I can use it with the steel loop in limited space situations or with a larger wire loop when I have access to some garden space with a tree. Together, the MLA-30+ and the PA0RDT make the perfect DX travel antennas.

The only thing I didn’t like about the MLA-30+ was that pre-attached coax cable. It’s not the best quality and I’d rather carry my own cable. I’m not very handy with a soldering iron in tight spaces but at our recent DXpedition my friend Bill Nollman replaced the coax with a BNC jack for me.

The MLA-30+ now looks like this when connected to a wire loop.

Finally, I should address powering the MLA-30+ via USB. While it can be connected to a spare USB port on your laptop, I found doing that sometimes introduced a tad more noise. Instead I’ve been using one of those battery packs used for recharging cellphones. Mine is rated at 6700 mAh and it can power the MLA-30+ for over 48 hours before needing a recharge. But be sure to test yours before doing any serious DXing. I’ve read that some power packs have a minimum required power draw and will automatically shut off if the draw is too low.

Another Option?

While I was finishing this article I heard about another option from my friend Guy Atkins. This antenna is a combination of the YouLoop with a low-priced Chinese made clone of the LZ1AQ amplifier. Some users say it’s better than the MLA-30+. Guy says it works well on shortwave up to 16 meters but he hasn’t tried it on medium wave. Guy says it’s a “low price, good value” antenna. I’m traveling in Southeast Asia for the winter but will definitely have to try this antenna when I get back to the USA. So maybe there will be a follow-up article next summer.

Links

[Note: Amazon links are affiliate and support the SWLing Post at no cost to you.]

Info on ordering a quality PA0RDT from Roelof Bakker. (Other cheaper versions have had issues with quality control.)

https://dl1dbc.net/SAQ/miniwhip.html

There are various versions of the MLA-30+ and the original MLA-30. This is the version that Mark Taylor recommended and that I bought.

https://amzn.to/3MEKjPY

There are numerous YouTube videos on using and modifying both versions of the MLA-30+. This one shows how to replace the coax with a BNC jack.

https://www.youtube.com/watch?v=OAqh2Lawwdc

Here’s the Amazon link for the YouLoop/LZ1AQ antenna that Guy has.

https://amzn.to/4s1RB09

And the same antenna on Ali Express.

https://www.aliexpress.us/item/3256808527623276.html

Portable Antennas for Serious DXing: Don’s Field Tests from Parks to the Open Road (Part 1)

5 Replies

Many thanks to SWLing Post contributor Don Moore–noted author, traveler, and DXer–who shares the following post:

Two Portable Antennas for Remote DXing (Part One)

By Don Moore

Once upon a time, I had a traditional DX shack with an L-shaped desk and shelves of receivers, radio gadgets, and DX books. Everything I wanted or needed as a DXer was right at hand. Then I retired and was finally able to pursue my lifelong itch for serious travel. But there was no way to carry that DX shack along with me. Fortunately, modern technology was there to help. SDRs are significantly more travel-friendly than my old Sony ICF-2010 (let alone the Drake R-8). Instead of books and bulletins, my DX reference materials are websites and PDF files on my laptop.

I spend several months a year traveling internationally with just a suitcase and knapsack. That doesn’t leave much room for DX equipment. Several years ago I described my approach to vagabond DXing in an article here.

https://swling.com/blog/2019/03/radio-travel-a-complete-sdr-station-for-superb-portable-dxing/

Since writing that article in 2019, I’ve continued to work on making my portable DX shack better and more compact. Recently, I replaced the Elad FDM-S2 with three Airspy HF+ Discovery SDRs. Not only are they smaller and lighter, but I can record three different band segments at once. Next up was rethinking my travel antennas. A wire loop with the Wellbrook ALA-100LN is still, in my opinion, the best travel antenna. But the components are heavy and are now irreplaceable since they are no longer made. So over the summer, I set about testing and comparing both old and new options. But you don’t have to wander the globe for my findings to be useful to you. This can be just as helpful for DXing from a nearby park. That’s how I did my testing.

I spent the past summer staying at an AirBnB in the north Chicago suburbs. I wanted a better location for testing so I checked out parks in the area and finally settled on Preserve Shelter B (42.26797, -87.92208) at the Old School Forest Preserve, east of Libertyville in northern Illinois. The shelter was entirely wood, with standard asphalt shingles (rather than steel), and had no nearby power lines. I made four daytime DXpeditions there to do some utility DXing and to run my tests. Here’s a photo of my setup.

I decided I should rerun the tests at least one other location. So while driving across the US in mid-October, I stopped for a few hours one morning at Park Shelter A (39.11144, -94.86629) in Wyandotte County Park, just west of Kansas City, Kansas. There, I just had a minimum setup.

The Antennas

So, what were the antennas I was testing? The first was the tried-and-true PA0RDT mini-whip from Roelof Bakker. The PA0RDT is described in my 2019 article and is probably the most portable quality antenna you can get. To power it I use a battery box and eight rechargeable lithium-ion AA cells.

For the traveling DXer, setting up the PA0RDT is as easy as it comes. I just attach the coax cable and throw it over a support, such as a picnic shelter beam or a tree branch.

But I’ve always believed that the best antenna is another antenna. That is, every antenna works differently, and therefore the more options you have, the more likely you will have something that works well in any situation. So if I wanted to leave the Wellbrook at home, what might complement the PA0RDT? I contacted my friend Mark Taylor, who I knew had a large collection of the various inexpensive Chinese-made amplified loops. With his help, I settled on the MLA-30+ MegaLoop from DmgicPro.

This antenna consists of a steel wire loop that connects to terminals on the amplifier box. The amplifier has a ten-meter coax cable, which in turn is connected to a small bias-T power supply, which gets its power via a USB connection. The MLA-30+ is designed to be used in a permanent installation with some sort of vertical support, such as a PVC pipe. Some users replace the wire loop with copper tubing.

Those options aren’t practical for me, and simply hanging the antenna from the top would cause the steel loop to stretch and deform. So I came up with the idea of tying a strong cord from the top to the bottom of the loop so that the cord, and not the loop, bears the weight. To hang the antenna, I throw the cord over the support, attach the antenna, and then pull it up into place. That works well if you have rear support to hold it in place, such as the beams of a picnic shelter.

It’s a bit more difficult to mount the MLA-30+ in a tree.

Comparing the Antennas

I ran comparisons between the antennas several times at Old School Forest Preserve and then again at Wyandotte County Park. The results were practically the same every time. The images below were made at Old School unless otherwise stated.

The PA0RDT was designed to be a good performer on longwave and medium wave. Unsurprisingly, it shows a lot of signals on the upper end of the medium wave band, even during the daytime. Except for being non-directional, the PA0RDT is an excellent MW antenna.

The MLA-30+, on the other hand, isn’t good for much beyond hearing the strongest local signals on medium wave.

When I ran these tests in the late morning, WWV on 5 MHz was the only signal in the 60-meter band. It had a very listenable signal on the PA0RDT.

But on the MLA-30+, WWV was barely there.

Likewise on 49 meters, CFRX on 6070 kHz was very clear on the PA0RDT but barely listenable on the MLA-30+. But when I moved up to 31 meters, the difference between the antennas mostly disappeared, as in these images made in Kansas. The PA0RDT is top and the MLA-30+ on the bottom.

On 25 meters, the PA0RDT is picking up a lot of noise and the signals are not that strong. Nor were signals very strong on 19, 16, 0r 13 meters.

However, on 25 meters with the MLA-30+ there isn’t much noise and the signals are booming in. And 19, 16, and 13 meters likewise had strong signals.

So the PA0RDT is clearly the best antenna for MW and the lower shortwave bands, but it doesn’t do as well on the higher bands. This wasn’t a surprise to me as I’ve always felt that the PA0RDT underperformed above nine or ten Megahertz. The MLA-30+ was abysmal at the lower frequencies but worked better or just as well in the middle and higher shortwave bands. The best antenna is another antenna. Each one performs better in different situations. But I couldn’t help but wonder … was the problem with the MLA-30+ that small steel wire loop?

Look for Don’s Part 2 article next weekend on the SWLing Post!