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The Alex Loop for SOTA

Thinking about trying to Alex Loop for SOTA. Particularly @ summits with very little room to put up my mast and my EFHW, this would be for summits with lack of trees or putting up a bigger antenna would be hazardous. In the past I’ve used an MFJ 1820 (what I call an HF HT Antenna). which has worked for me on 20m. Obviously I know a wire will almost always outperform a magloop but just curious if it’s worth the extra weight or if I’d be better off just sticking with the MFJ 1820 in these situations.

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I bought an AlexLoop about four years ago for operating from hotel balconies or holiday homes but never did (most hotels and holiday homes have lousy HF take-offs).

For backpacking portable (e.g. SOTA) the AlexLoop in its supplied bag takes up more volume than an EFHW, (collapsed) 4m pole and guys/pegs, It takes just as long to assemble and disassemble. You can’t use an ATU with a mag loop and the AlexLoop needs very careful tweaking of its tuning capacitor to optimize it for a given frequency. Also, it’s highly directional so in a CW pile-up you would be jumping up every 30s to rotate it for those faint stations thereby missing half of your chasers. Frankly, I think it would be a pain in the neck for SOTA.

Wire antennas like half-wave dipoles are more efficiency – and more practical. As mag loops go, I’m sure the AlexLoop is a good one. I sold mine a few months ago in hardly-used mint condition.

The majority of summits I activate don’t have trees. I consider this a blessing. Trees (especially wet ones) adversely affect the take-off and – in my experience – are rarely in the right place and distance from my operating point to be useful as a support post for the antenna.

Until this year I always used a 60/40/30/20 or 20/10/6 inverted V, linked dipole on a 7m pole or one of several EFHWs. But recently, especially for cramped or crowded summits I’ve been very happy with a HF vertical – a Chameleon MPAS Lite – expensive [“but I’m worth it”] and heavier than wire ones but robust in adverse weather and with a smaller footprint.

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Blimey. Just gone to look at that… £350!

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Had a loan of an Alex Loop for a week or so to try but only managed a single activation with it. I was interested for much the same reasons, restricted rocky summits.

On the plus side, on 20m it seemed to work well, I had about 20 qsos on the band including one from the USA.

On the negative side I found it impossible to find the noise peak on 30/40m due I think to a combination of the low noise level on the summit being drowned out by the wind noise blowing across my ear buds.

Would I buy one ? Not on your life at the monster price for a bit of coax and plastic , well ok am sure the capacitor costs a bit and you get a nice laptop bag to carry it in. The OM0ET version of the portable mag loop is slightly cheaper but not by much.

You might want to look at the PAC-12 antenna from Ali Express, costs a little over a hundred quid, EI9JF got one and has had a lot of success with it stuck next to his camper van when touring about.

Declan
ei6fr

Worthless on 30 and 40. I found a tripod small enough to fit in the bag that comes with the loop.

EL

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I only used mine for chasing and it was a bit of a pain to have to retune on the band. I never did get to do an activation before it got chopped in for the next toy, so I will leave it to someone with more experience based in reality.

I use a Super Antenna MP1 as my ‘low footprint’ antenna and it is superb down to 40m. You can make qsos on 60m and 80m with the coils but it is very compromised.

That’s where the SOTABeams Band Hopper 4 really shines.

The magloops are QRP only which should taken into account too. That might not matter to you. I pair the Super Antenna and the Band Hooper IV with rigs pushing anything from 2.5w to 150w, no complaints.

Having said all that I’ve had plenty of QSOs with folk using magloops and they often sound awesome.

Have fun!
Mark

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My mate Bernie made an Arduino based self tuning loop. It had a motor to drive the capacitor and SWR bridge and the controller drove the motor to get the lowest SWR whilst you put 500mW into the loop from your radio. I’ll see if I can find the video.

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I’ve used the Alex Loop on multiple activations, primarily on summits that I know will be crowded. I’ve found it to be an effective antenna, even on 30m and 40m. I’ve experienced difficulty tuning on 40m, but can usually manage it. I’ve seen no appreciable difference in the number of QSO’s I work with the Alex Loop versus my normal EFHW configuration. As mentioned, it is bulky, but for the summits I use it on, usually drive-ups or short walks (that’s why they are crowded), it’s not a problem to just carry the bag it comes in. I wouldn’t use it as a primary antenna, but for crowded, easy to access summits, I find it to be an effective alternative when a smaller footprint is desired.

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Here you go…

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As the sunspot cycle progresses and conditions improve, small transmitting loops become more viable as an option.

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The OM0ET loop seems to be a very odd design. He only uses the inner of the co-axial cable that forms the loop. He also seems to provide more performance data on the cardboard box that he sends them in than he does about the loop itself. On the plus side that means he avoids many ridiculous claims.

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But is is a beautifully engineered box :slight_smile:

Declan

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Richard, watched the video – I think your comments were a good summary of the pro and cons of mag loops. Glad to see your demo on a SOTA summit rather than in a local park where the vast majority of online videos demo’ing antennas are made [thereby understating some of the real challenges of erecting antennas on hilltops].

It reminded me that mag loops need a tripod or something similar (to be considered when making antenna comparisons). You had light winds on The Cloud that day, so some tripod mooring would be needed for stronger winds.

Finally, the declining trend line you showed of solar cycle maximums in recent decades suggests – whilst propagation conditions should improve over the coming years – operating low power with compromise antennas – especially on voice modes – will continue to be a challenge [All part of the interest and fun].

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To be fair to Old Sol, the actual sunspot figures show that the activity is consistantly greater than predicted for cycle 25 and the steepness of the rise suggests that the peak of cycle 25 will be quite a bit more than the predicted figure (115 IIRC) so hopefully we can look forward to better times than we were given by cycle 24.

With regard to loops, I looked into them some years ago and concluded that a shortened centre loaded vertical would outperform a loop and be more convenient to carry, set up and operate.

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A cheaper alternative is the HF-P1 Portabel Vertical 80m-2m 150W incl. Tasche, Stativ HF-P1-Set Portabel Vertical 80m-2m 150W incl. bag, tripod | Difona Onlineshop

Used a MP1 before … switched to the one mentioned above… there is even an adapter (separately available) if you would like to use those huge MFJ sticks… which I do.

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Hello Ingo,

As you replied to me and you linked to a HF vertical, I assume you are talking about the Chameleon MPAS Lite I mentioned above.

Yes, I’m sure most portable HF verticals are cheaper, an important consideration if one has to do the hobby on a budget. US-made equipment is expensive especially here in the UK as I found buying an Elecraft KX2 2.5 years ago [about which I also have no regrets].

While cost is important to me, other factors like quality of components, robustness, ease of set-up/pull-down, and ability to operate in wild weather were the driving factors for my choice. I was very impressed by the many positive reviews for Chameleon’s ‘big brother’ version, the MPAS 2.0 on these features. The newer MPAS Lite is aimed at the amateur radio market, and uses many of the same high-quality components but without most of the extras. I enjoy the ease of set-up even wearing gloves and expect it to work for many years to come.

I have operated the MPAS Lite in wild weather and the sturdy thick-diameter 5.2m (17ft) telescopic whip doesn’t bend as much as with other verticals. The 38-cm ground spike ensures the vertical doesn’t fall over in gale-force winds (as would ones with small tripods like the one you linked to).

As we say “It’s horses for courses”. [No one solution suits everyone].

Regards, Andy

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Thanks for the details Andy.
Indeed, in strong winds I have to secure it somehow… stones on the tripod or with some tape. Or if there is a bench around, fix it on it.

But winds here in the region are very often not comparable with those in the UK.

My Alexloop was perfect for operating from a cruise ship balcony. I made over 4000 QSOs during the contract, and worked over 100 DXCCs.

It doesn’t seem as efficient as a resonant antenna (dipole or groundplane) from a summit - which is to be expected.

As Richard says, it could prove to be an effective SOTA antenna as we head towards the peak of the solar cycle.

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I saw this improvement to loop antennas on you tube. Very interesting.
Ham Radio - A simple magnetic loop modification with a big improvement! - YouTube

73 Geoff vk3sq

Hi Geoff,
I did read about this changing the coupling loop shape trick as a way to improve SWR when it wasn’t possible by just fine tuning the variable capacitor and it’s something I did and experienced myself on my homebrewed magloop.
Flatenning the circular coupling loop into an oval shape did improve SWR response sometimes in certain bands.
What I didn’t know and found interesting in the video you posted is that the radiated RF also increases by increasing the length of coupling loop being close to the main antenna loop.
Thanks for the info.
73,

Guru

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