Saturday, March 31, 2018

Spring tuneup on the MFJ 1788 Loop antenna

Oliver was going to watch over the operation
Each year around this time I bring the MFJ 1788 Mag loop in to take the covers off and have a look around to see how it has faired over the past year. This antenna has been great for me with my very restricted condo situation. I have been able to get all around the world on CW with most of the time 5 watts QRP. I am about 60 feet in the air, it's on the balcony and we do have other condo's all around us but having said that I have been very pleased with the performance of the loop. At first tuning the
Cleaned covers

loop took some time but now I really have the hang of things and am able to tune it in no time. Most of the time the SWR is flat or very close to flat on all bands it's designed for. Now as for band width on 15m it's very nice but as you move closer to 40m it gets very narrow but it is what it is. When reading the reviews of this antenna on Eham many have mentioned how the antenna when new from MFJ had an issue or two. My antenna also out of the box had an issue with the tuning box with a switch that had to be replaced. I purchased the antenna through DX engineering and they were very fast to have MFJ send me a replacement switch.
Now back to my yearly maintenance, the antenna is covered with a patio table cover to help it look like balcony furniture and funny thing is it does not affect the SWR at all so the cover is kept on all the time. This year I picked up a new cover as the old one was 4 years old no longer water proof and showing it's age. I removed the plastic covers  and cleaned the inside out which were really not all that dirty. I found as I do each year some loose nuts and bolts that require
Keep track of parts 
snugging up but this year I noticed one of the nut/bolt combination seemed to have some burning on it. This was one of two nut/ bolts that help secure the loop to the tuning cap. All other nut/bolt combinations were fine it was just this one that I ended up replacing with close substitution from my nut/bolt collection.  I have posted a picture of the nut/bolt that was removed, any suggestions as to what may had happened? The nut/bolt was not at all loose and it was only this nut/bolt that had an issue. One other thing I like to do is run the tuning cap full turn in both directions looking for smooth operation, spacing moving fins against the stationary fins and the function of the micro switches that stop the tuning cap at the end of each end.  Overall the antenna was in great shape and just to make sure once it was all back together and covered with new cover I tuned it through each band to make double sure all was well.
New cover and ready to go
Nut/bolt that was replaced
New nut/bolt installed

Checking fin alignment 


  1. Hey Mike,
    Do you notice any interaction with the balcony railing? I have to keep my 1786 as far back from the railing (glass/metal) as possible otherwise the swr begins to get unacceptable.
    Thanks and 73.
    Paul VA3ZC

    1. Good afternoon Paul and thanks for taking the time to read the blog and commenting, I too keep my loop in the centre of the balcony as there is the railing and glass that bothers it but I also have a large concrete pillar to the left side that I have to stay away from as well. I have a black mark on the balcony floor were I move the loop to when in use and then off to the side of the balcony when not in use.

  2. Mike, great post about your antenna and how to beat the HOA or renters worries. I’ve used a variety of a antennas but I’ve not tried a mag loop yet. The only reason why I haven’t is that I’d rather not have to carry a tuner with me if possible and my radio does not have one built in. For that reason I tend to stick with simple and resonate antennas. That being said I know lots of guys that have worked the world off a mag loop. I got a good laugh when I saw your “stealthy cover” tarp over the antenna!

    72 de Mike KQ9RP

    1. Hi Mike very nice to hear from you and yes there is always a creative ways around the HOA. The stealthy cover keeps it out of sight and out of mind.