Loops HF antennas for Aero SSB monitoring

[ILSAPP]

Hi all,

I'm looking into the ALA100LN to improve my HF aero listening experience. Any feedback about it for this purpose? I have space to put 20m wire loop thus I'm not considering the ALA1530...
Do you think that the PAR EF-SWL will be nearly as good for less than half the price?
Price of course is important but I'd rather spend more on a antenna that can probably provide me better reception performance... Btw I'm using the Airspy HF+.

Many thanks

 

[ka3jjz]

Loops and wire antennas work In very different ways. Loops are less sensitive to man made noise than most wire antennas, even the PAR, Comparing a large aperture loop to a 45 foot wire is really no comparison at all, as they work very differently. However you might find that the PAR does better than the loop at times, as well as the exact opposite. This is because propagation, as well as how a signal arrives on your antenna, is very difficult to generalize from day to day; it can and does change.

If you can swing it, having 2 distinctly different antennas may be an advantage worth having. Many top DXers do, for the reason above.

The only thing I might say is that depending on where you are, a 20 meter loop might be way too big for the Airspy to handle. Overloading might very well be an issue here. If this is the case, a passive (not active) preselector would be the answer here.....

https://wiki.radioreference.com/index.php/Improving_HF_Reception

Mike

 

[jwt873]

I have an ALA-100LN. I use it with a 34 foot loop I built on a plastic PVC frame.

It's fantastic from 2 Mhz on down. The 160 meter ham band, the AM broadcast band and the NDB beacons all shine.

They say the ALA-100LN is good up to something like 30 Mhz, but I never found it to be that impressive on frequencies above 2 Mhz. At least not for the price they charge. You might find the PAR EF-SWL is a better deal. Hopefully someone here has used the EF-SWL and can comment on how it performs.

 

[ka3jjz]

I only know a little about large aperture loops but I get the impression that, dependent on the freq and height above ground, their pattern is more vertical (maybe NVIS) and really doesn't have the directivity that a small loop - like the W6LVP series, for example - would have. Too, loops like the W6LVP are vertically mounted, not horizontal, as some large loops (such as skyloops) would be. Different animals, propagationally speaking.

That's not to say that a large loop won't work well. but orientation is obviously a factor. Take this little project that uses an ALA100LN as an example...this antenna is mounted vertically.

Video: Paul’s large aperture “Volleyball Net” loop antenna

Personally, I would use the ALA100LN to build a small loop, not a large aperture one. In fact, W6LVP sells a kit that is much like the Wellbrook, but not quite as expensive....Mike.

 

[ka3jjz]

Here's the page on the W6LVP website. Note that he mentions that 6 foot of wire will do fine for a loop...

W6LVP Magnetic Loop Antenna Experimenter’s Kit – W6LVP

Mike

 

[ILSAPP]

First of all many thanks both @jwt873 and @ka3jjz for your quick and clear reply.
So at the moment I'm debating between the 26LVP experimenter kit and the EF-SWL. Both will come at the same price in the end because for the EF-SWL I have to get a pole to get the best of it while for the loop a lower height will be sufficient...

 

[invergordon]

As a bit of an HF aero nut myself I hear your dilemma ILSAPP. I have, and continue to, experiment with my HF antenna to get the best reception from my QTH here in New Zealand. I strive to catch the ever diminishing short conversations between radio operator and pilot to areas of the world that would seem to be out of reach for a laymans (aka amateur) antenna.

I started a few years back with a Wellbrook AL1530 and it was pretty good, from here I could seasonally catch Shanwick, Santa Maria and Gander. A friend loaned me a TF2D which proved a simple wire and un/un could receive as well as the Wellbrook so from there I transitioned to a flat top dipole cut for 8MHz and that was really good reaching Magadan and Murmansk occasionally.

Currently I am trying a Delta Loop, a simple triangle with a 4:1 balun and testing the feedpoint in different locations such as top, centre bottom and corner. It's not looking as good as the dipole so the DL is not likely to remain.

I did try the PAR EF-SWL but it was no better than my homebrew dipole so we parted ways quite quickly!

I'm tempted to try the LZ1AQ amplifier kit as this would allow the antenna to be located away from noise sources and connected via ethernet cable.

I understand that most of my target signals will arrive at the antenna at fairly low angles and I think that should be a consideration for the antenna type you, or I, select based on cash at hand, build skills and time.

 

[ILSAPP]

@invergordon Thanks for your detailed reply. I have also tried different antennas (regular longwire, dipole for 7MHz, tuned magnetic loop) with good results but all of them can't make possible hear those faint signals from far away. Until now the best antenna I used was the manual tuned loop antenna via a variable capacitor (but of course not pratical for remote operation). At the moment I have the dipole plus the LZ1AQ with two loops (two loops in one plane and symmetrical vertical dipole) and I remotely can switch between both antennas. Still I think that there is room for improvement. Sometimes the loop perform better but I find that the dipole is most of the time the best performing antenna on HF aero bands.
I have also thought of the vertical antenna to get those low angles for DX but never tried it because of the needed big radials around it. Have you tried?
I admit that the power supply of the raspberry (which I need to listen remotely with my AirSpy HF+) may cause some additional noise as it is powered by a switching power supply rather than a linear power supply. Also the LZ1AQ amp is powered via a LM7815 connected to a +19V switching power supply.

 

[invergordon]

Yesterday was a watershed day for me. Having said previously that my Delta Loop would more likely be swapped out for a dipole I think I may have spoken just a bit too quickly there! The original construction of the loop included terminating the two ends with a 4:1 balun and while it worked reasonably well I found this example on the web recently and decided to swap the 4:1 for a 9:1. So I built the windings on a 2.4 inch toroid that I had skulking around the shack and honestly at 4pm in the afternoon I was picking up HFDL stations on 13MHz and 11MHz that I would not normally see. This bode well and as the evening and greyline approached up popped many more stations including additional NAT frequencies on 5MHz and 6MHz. I was a very happy chappy and with this antenna, transformer and feedline and I have gradually been reducing the amount of gain (or obversely, increasing the attenuation) of my SDRPlay RSP2 to accommodate the improved SNR.

So to summarise the antenna construction, I have a single aluminium mast of 8m. At the top is an eye through which a chord is fed to haul up the feed point which is a simple insulator of fibreglass where the two ends of the loop are connected to some 300ohm feedline. The feedline is then terminated at the base of the mast with the transformer described in the link above. I then have coax fed underground about three metres to my shack and connected through an RTL-SDR AM band filter to the RSP2. The two corners of the loop are fed through insulators and the long bottom of the loop is about 1.5m above ground and about 11m long.

 

[majoco]

I have just 'copied' Mike/Invergordon's antenna slightly modified to suit the physical arrangement of my back yard. Above my shack window is a TV antenna mast (with no TV antenna!) - the top is about 13feet off the ground - I took the two ends of my OCFD, 33 and 20feet each and secured them to the 6feet high wooden fence via insulators - then joined the two ends together with another 43feet of wire - a 9:1 unun and feedline choke up the top of the mast via coax to my multicoupler through another choke. I suppose you could call it an "off-centre fed sloping delta loop". Seems to work very well - noise levels are lower - the lady working NAT D Gander on 8911kHz was quite busy in our late afternoon - obviously a Noo Yoicker from the accent!

 

[invergordon]

I'm glad my designed worked for you Martin, and only yesterday I changed my antenna back to a flat top dipole. The reason I did this was that while the delta loop performed well across most bands the signals were not very strong, they were there but I thought just a bit too weak so I reverted to a tried and trusted dipole. The signal levels have risen significantly and my new KiwiSDR seems to be bringing them in very nicely. If anyone wants to have a listen, http://nzsdr.ddns.net:8073/ is the URL, enjoy!