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Does anyone here have experience with mag Loops?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by G4SEB, Sep 6, 2020.

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  1. AI3V

    AI3V Ham Member QRZ Page

    Your dipole is in a very poor location.

    Get it higher than the house and surrounding objects and you will see a tremendous improvement.

    Perhaps a local hilltop you can hike up sota style?

    Rege
     
    AK5B likes this.
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    What's restricting the "height" to such a low elevation?

    On 20m, you'd want the dipole to be at least 32' (10m) above ground to actually work like a dipole. All bets are off at lower elevations, and if its current height is lower than the roof of your home and surrounding homes, that makes it all the worse.

    A G5RV at that elevation won't be any better.

    The STLs (small transmitting loops, often called "mag loops") aren't as picky about height above ground, but remain just as picky with regard to "blockage" from manmade structures like houses. Houses that are made of only wood, with wood or vinyl siding and no cement, bricks, stucco, aluminum, foil-backed insulation and such are fairly "transparent" to RF, but other materials aren't. Cement and stucco are really bad, and "stone" or bricks (which are just fired clay) isn't good, either. With homes made of such materials, you need to be "above" them or at least very far away from them.

    Among other rigs, I have a G90 and run it at 20W output (its max, and only 3 dB more power than you run at 10W) and worked Bulgaria with it on 20m last week...from southern California. Probably ~6000 miles. 559 report. But I'm using a beam on a tower, not a very low dipole.

    Antennas matter a lot.

    I do have an MFJ "Super Hi-Q Loop" which many might refer to as a magnetic loop (I call it an STL) and it works amazingly well when I'm camping/portable and "in the clear" of obstacles. I have the 40m through 15m model and have worked a lot of DX with it, mostly on 30m CW and some on 17m. It's not great on 40m, although it can make contacts with timing and patience. I don't use it at home, though: Mostly "camping," and sometimes with it just hanging from a low tree limb by a piece of rope -- maybe 7-8' above ground. But in such cases, it's "wide open" all around it except for a few trees, and the operating locations can be pretty good, like at the beach (nothing but sea in one direction) or on a mountaintop (like when we camped for a week on the south rim of the Grand Canyon, which is around 7000' above sea level or something with a clear view in several directions and the only obstructions being some trees).

    If I tried using that "at home" next to my stucco-sided (cement sided, really) house, it would probably be pretty bad unless I could get it well above the roof.
     
    AK5B and KF5KWO like this.
  3. N8TGQ

    N8TGQ Ham Member QRZ Page

    Hi Sebastian! After reading more about your situation and reading you QRZ page, I have some ideas.
    First, is your 20m dipole really 10 meters on each leg? A halfwave dipole should only be a half-wave long, as the name implies.
    I live in an apartment and can't put up any antennas at home, so I use an end-fed half-wave antenna at the parks. I use a 5 meter telescoping fishing rod at the middle and is only about a meter off the ground at the ends. Its only 20 meters long and works without a tuner on 40, 20,15 and 10 meters. I have been using it for years and can put it up or down in about 5 minutes.
    Check Sotabeams, QRPGuys or QRPKits for their products. Some even have the schematics right online if you want to build your own.
    I can work the whole eastern half of the US with 3 watts CW.
     
    KF5KWO likes this.
  4. AK5B

    AK5B Ham Member QRZ Page

    Sebastion; Any chance of getting up to the top part of that church tower pictured on your QSL card? That could be a potentially great portable operating site if so.

    Also wondering if your 20m dipole is 20 meters per side or is that an oversight? A proper 20m dipole should measure around 32--33 feet or about 5 meters/16.5 feet per side.

    I love to operate portable on17 and 20m by the seaside with a simple elevated fan vertical with two radials per band---another idea for you if you are close to the sea (saltwater enhances the lower angle radiation from verticals about 6db). Let me know if you need the details; simple to build with wire and a fishing pole. 10 watts could give you a lot of good results far better than a dipole way too close to ground.

    I have a lot of experience with STLs, too (small transmitting electromagnetic loops) and although I am very fond of them I will not recommend one to you because building a really good one isn't a simple sort of undertaking at all. In a nutshell, most of the commercial ones are downright mediocre at best (the expensive Ciro Mazzonis and a couple of MFJs are the only exceptions as far as I know).

    So building one yourself is the best solution, should you want to go that route later on---but be aware--besides the expense of vacuum variable tuning capacitors and remote tuning mechanisms, there are logistical and construction aspects that require patience, brazing and other mechanical skills---not a simple weekend project in most cases. Even 5 watts to a STL will generate 1100 volts and very high RF current---care must be taken in their design and use. Maybe later on in your ham "career" you will be better able to explore one as a possibility---but starting out it is always best to go with a good, simple antenna like a dipole or vertical.

    I build all of my STLs for operation at 500-600 watts, too---the higher power really helps overcome some of their shortcomings, particularly when using ssb instead of the more efficient modes like CW or digital. So tuck this idea into your hat for now and maybe you'll decide to come back later when you have a need for multiple antennas and a place for them in your QTH.

    Hope this helps and do let us know if you are actually trying to use a 20--meter long dipole on 20 meters---that is a big problem right there!

    Otherwise, welcome to ham radio and we are all rooting for your success!

    73,

    Jeff

    The Loopy guy in South Texas
     
  5. AI3V

    AI3V Ham Member QRZ Page

    You should post a picture of you, your rig, and your toy loop that "works amazingly well hanging from a tree"

    Or, let's quit trying to convince a 15 year old novice to pi$$ away $500

    Rege.

    Who once again would like to remind Steve that I installed a 32 loop RECEIVING array, that was mediocre at best on RECEIVE and totally useless on tx.

    It would be like strapping a lawn mower engine on a bicycle and thinking you were ready for the Isle Of Man...
     
  6. KB1CKT

    KB1CKT Ham Member QRZ Page

    What does a 32 loop receiving array look like? (32) 3' loops over an acre or more? I'm trying to figure out what this looks like.
     
  7. AH7I

    AH7I Ham Member QRZ Page

    These days the 20 m band is not good all day or every day. But on occasion it's hot and you'll be able to work some people with a good dipole at a poor height of 2 m. It will be noticeably better for every meter higher. It's a great antenna at 10 m. Try some CW and digital in addition to SSB. Having to put it up and take it down and only running 10 W, you might try some portable work. Take it to the seaside. Bring a long fishing pole. You can use it to support the antenna or if the band is dead, for fishing.

    73, -bob ah7i
     
    AK5B likes this.
  8. PU2OZT

    PU2OZT Ham Member QRZ Page

    STL are fun, you can light up a neon lamp with no contact [​IMG]
    and pretend you're Nikola Tesla.
    Seriously, by the second a wrongly constructed MLA capacitor sparks you've destructed your finals, I guess. I managed to see a few sparks (my cats too) but I expect them and monitor closely via meters, and my rig survived because it's a Kenwood hybrid. However, made a hole in plastic insulator, made of an ice-cream lid, not the best Teflon®.
    Ever add all costs for a solidly constructed homebrew MLA?
    Not even a Ciro Mazzoni's uses vacuum variable caps.

    Oliver
     
  9. K6CLS

    K6CLS Ham Member QRZ Page

    Use vertical antennas near salt water! How about a nice QRPguys 9:1 EFHW. Horizontal dipoles back home.
     
  10. AH7I

    AH7I Ham Member QRZ Page

    Send him the EFHW. It might help. No need to spend on one though.

    For a 'free' vertical, he can run one side of the dipole up the pole and use the other as a single radial or add two more and run the three to stakes to keep the pole vertical. Save the money for a battery to take to the seaside.

    To see what's happening on 20 m:
    Listen for NCDXF beacons on 14.100
    The call sign and the first dash are sent at 100 watts. The remaining dashes are sent at 10 watts, 1 watt and 100 milli-watts. These beacons are running vertical antennas so if you can hear the ten Watt signal, propagation in the reverse direction should be about the same.
    Look at dxmaps. Select 20 m and most recent 15 minutes for a current picture.
    Look at reverse beacon network. You'll see signal strengths.

    With your current antenna, listening for the strongest stations and calling them may be the best strategy.

    73, -Bob
     
    AK5B likes this.

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