Open question:
I’ve many times used a home made magnetic loop with very good results and I’d like to have been able to take it with me to some SOTA activations, but mine is too big (1,45 m diameter), so it’s hard to be fitted in a car and difficult to carry up to the top of a mountain.
I recently read about some SOTA activators using an AlexLoop antenna and after googling, I’ve been reading about it on the web. It seems this may well be the best antenna for SOTA activations, as it fits in a small and light package, it seems to be easy and quickly unpacked+assembled to start operation quickly / disassembled+packed to descent quickly.
How do you (the owners and users of this antenna) find the AlexLoop for SOTA activations from the portability as well as from the antenna performance points of view?
Would you mind sharing with us in this reflector your feels and experiences with this antenna?
Thank you in advance.
Best 73 de Guru - EA2IF
In reply to EA2IF:
I used an AlexLoop on most of my activations during winter 2013 when temperature was below freezing. It is very fast to setup on a small camera tripod and a perfect antenna for frigid weather. Performance is okay but not as good as a full size wire antenna, which is also lighter in weight.
73, Barry N1EU
I purchased an Alex loop principally for the convenience of overseas travel. Will be heading to France in May / June & doing some chasing from a small barge!.
I used the loop on a recent activation to Mt Bullfight. Access off track for about 90 minutes. This was a joint activation with Ron AX3AFW.
Antenna is light weight and fits perfectly into my camera tripod with the tilt head removed. A low profile, compact and convenient antenna.
I had the KX3 and loop up and running in no time at all & had made 1/2 a dozen s2s 40M contacts before Ron had finished setting up. The results on 40 metres were certainly down compared to the doublet but I felt that the lesser performance did not result in any lost contacts.
Tuning is very tight thus does not have the advantage of the doublet where one can scan across various bands for a listen without the need for tuning.
Summary. A convenient antenna to have in ones kit. Especially good in busy locations where a full sized antenna will be a hazard.
I am not certain how it would stand up to gusty winds often found on a summit.
Cheers Tony VK3CAT soon to be F/VK3CAT/P
In reply to EA2IF:
I sold my Buddipole and bought the Alexloop. The Buddipole was heavy, >6 kg, and is either an off-center fed loaded horizontal dipole or a vertical. As a horizontal, it is way too low except perhaps on 12/10 meters. Setup time was in excess of 30 minutes usually, and tuning when QSY took 20 min or so. The Alexloop weighs a little less than a kilo, my tripod brings the combination to about 1.5 kg, it sets up in about 5 minutes, and QSY is just turning the knob.
I set it up right over my head so I can reach up to the knob. It clearly works better than the Buddipole on 30-10 meters. It’s a little compromised on 40 meters because the loop is a bit small, but I still make QSO’s on 40 with it and 5W from my K2. The SWR null on 40m is quite sharp which can be a little issue in winds. That gets better on 30m and is fine on 20m and down. It is nearly insensitive to ground or me moving around under it. It is somewhat directional [in the plane of the loop] but that is very broad. There’s a moderate sharper null perpendicular to the plane of the loop.
It’s a resonant transformer design so you MUST bypass any autotuner and tune the antenna to resonance [and minimum SWR]. I have no problem getting it to 1:1-1:2. If you do not get it to resonance and let the autotuner match it, it will be a very good simulation of a dummy load.
73
Skip K6DGW
Auburn CA USA
In reply to EA2IF:
Guru,
As an activator I think you have to try various antennas and decide what your personal priorities are. A strong young man may be OK with carrying several Kilos of antenna gear. Speaking as an older operator, often climbing up high in thin air, minimizing weight and set-up time are what matters most. Operating on several bands is also a lot of fun.
My favorite antenna is 20M (66 ft) of #24 teflon copper/silver wire, supported as an inverted-L by a 6M fiberglass fishing pole, fed at the bottom by a homemade high-impedance tuner. This system is resonant and very effective on 40M, 20M, 15M, and 10M, and useful on 30M, 17M, and 12M as well (even though not resonant).
I have contacted you and your friend EA2LU several times recently from SOTA peaks here, on 20M and 15M, and that’s the antenna I used each time. The total weight of this easy antenna is about 1 KG, but it can be much less if you use a graphite (carbon) pole and thin wire. The key to the system is the tuner. The Hendricks SOTA tuner and several other tuners are similar to what I use. My system differs in that I have 2 tuners cascaded, to provide perfect matches on every band. An adjustable tuner similar to the classic BLT tuner runs at low impedance (50 - 200 ohms, plus some reactance) and feeds the high-Z resonant tuner. Other SOTA operators are using single tuners designed to provide the high-Z match. The impedance of this end fed antenna is between 1000 and 4000 ohms, with some reactance, depending on the frequency. Other lengths of wire perform well, such as 10M (EFHW) for 14 MHz.
There are no radials, and the only coax cable is a very short piece of RG-178 from the ATS-3B radio to the first tuner. Using two tuners sounds odd, and there’s the potential for loss, but usually I find an almost perfect match just tuning for band noise by ear. The final match is perfected with the resistive bridge with LED indicator.
I agree with N1EU that in cold weather the priorities are different. I have used my system in deep snow at -6 degrees C. Our here in Colorado we have strong winds, and sometimes it can scatter your gear and blow away the log! The single pole is OK if it’s tied to something - a tree or rocks - the antenna wire helps keep the pole stable in the wind, because everything is under moderate tension.
73 and CUL - thanks for many DX SOTA QSO’s!
George
KX0R
In reply to EA2IF:
How do you (the owners and users of this antenna) find the AlexLoop for SOTA activations from the portability as well as from the antenna performance points of view?
I have used magnetic loop antennas, including the Alexloop for many years.
My personal experience so far with the Alexloop is:
PRO’s:
-
gets you on the air
-
from any place (no trees or pole needed)
-
on all HF bands from 7 Mhz up (by just turning a knob)
-
in minutes (you can have a successful activation before your fellow activator finishes installing his wire antenna [private joke])
-
-
light enough to be carried to the summits I am able to activate
-
until now, it never failed to allow me to make many contacts from every summit
CON’s:
-
expensive (but really very well made)
-
very sharp tuning (this is in fact NOT a problem for an activator who stays on the same frequency for a while, but is annoying for “search and pounce” mode).
Magnetics loops are arguably not the most efficient antennas, and you probably can install more efficient antennas on SOTA summits. But they are extremely effective for SOTA activations, being true ALL-bands, lightweight, easily set up, and giving very acceptable results.
Anecdote: I was on holiday a few months ago in EA8 (Canary Islands), and for once I had plenty of time to set up an End Fed Half Wave antenna in the trees. Unfortunately, I could not manage to make a single SOTA contact with it that day… As the weather was changing quickly, I installed the Alexloop in minutes and made several SOTA contacts on 24 MHz… Activation “saved”.
Christophe
73 de ON6ZQ
Thanks everyone for your feedbacks.
I appreciate it.