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| Homemade vertical mounting....."thing" |
After doing some "playing" with the location of my 1788 mag loop on the balcony and getting really nowhere with lowering the SWR. The lowest I could get it was 1.6:1. I decided to go vertical with the loop to see what happened. Now those of you that have the MFJ 1788 loop know there is a bracket that comes with the loop for just this purpose. Well when I moved I know I put this bracket somewhere safe...........and it's still there as I can't remember where this "safe" place is! I did try putting the loop vertical bout a month ago but at the time I was tired from all the fiddling around on the balcony and my vertical attempt was very hap-hazard. That approach did not seem to work for me either and I just left it at that. As time passed I decided to take a more serous approach at mounting the loop in a vertical position. I went to the hardware store and picked up some metal conduit and the finished product was a decent looking mount that allowed the loop to be vertical. In a vertical position I knew the antenna would be directional but if the SWR was lower that was just fine with me. Low and behold on a certain place on the balcony the SWR is 1.4:1 which I am pleased with.The loop is still mounted inside a tripod on the balcony and you can see some holes in the tubing. When the new loop vertical bracket is placed inside the tripod tubing I slide a pin through. This stops the loop from spinning if a wind comes up. The next step will be to put some watts into it and see what
happens! It just really gets me how time just flies and all the non ham things pop up which make me very happy that in just over a year I will be retired. I will have as much time as I need to get things done (not just ham things) I can't see myself getting board......well that is the plan anyway. Now I did mention in my last post about an update on the Sun SDRpro 2 rig that is going to have to wait for about 1 more week.
The MFJ loop finally has a decent SWR match!!
16 December 2018 | by 
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I was having issues with the SWR on my repaired MFJ Loop (as blogged on here)
https://www.amateurradio.com/in-the-loop-first-impressions-of-the-mfj-1788/
It would be fine, then later the SWR wouldn’t be but only on 40m, other bands were fine. I then worked out that it was being affected by the metal roof of the neighbour’s garage, depending on how it was rotated. There a reasonable distance between it and the loop but had a big effect
73
Andrew M0NRD
you will not find any difference between 1.6 and 1.4 swr
I have a 1788 also. New out of the box I needed to work it over to make it work properly. There were loose screws on the capacitor drive mechanism and a few other mechanical problems. The antenna mounted vertically is not very directional. There are, of course, a couple of near nulls, but other than that it is almost non-directional. Why worry about about 1.6:1 SWR? I’m pretty sure neither you nor the radio can tell the difference between 1.4 and 1.6. I’ve considered rebuilding the antenna with a stepper motor and an arduino controller. It should be an interesting project. The MFJ control box doesn’t impress me at all and I think it is pretty much a clever gimmick. The whole thing could be replaced with a faster motor drive and tune it by ear in much shorter time.
Good evening Andrew and very nice to hear from you, that is crazy that the metal roof on a neighbours roof would affect your SWR! It was good that you found it as that could drive you nuts trying to find.
Thanks for taking the time to comment
73.
Mike
Top of the evening Jack, it’s very true that 1.6 or 1.4 not much difference BUT for me with the loop my goal in getting the SWR as low as possible is as I tune my rig up or down the band the SWR goes up. With an SWR of 1.6 to start I have to retune the loop more often compared to a starting SWR of 1.4 or lower.
73 and have a great weekend
Mike
Good evening Les and thanks for taking the time to leave a comment, when my loop arrived it had a defective push button on the control unit but fortunately it was only for the light. MFJ sent me a couple of new ones and I just replaced it on my own. I did get a great bit of advice from a fellow ham who has the loop as well. He adjusted the pot that controls the fine adjustment of the loop on the control box. With the slower speed he was able to improve his SWR! I am going to try that on the weekend and see how it works. The reason I wanted the lowest SWR is because how the SWR climbs as you turn your rig up or down the band. The lowest SWR gets me greater bandwidth before a retune.
Les thanks for the comment and have a great week and Christmas!
73,
Mike
True there’s little difference between 1.4 & 1.6 to one SWR but the danger of having more than say 1.5 to one is concerning the fact that it is the conjugate condition which can cause high voltages from the VSWR – OK for valve rigs but deadly with semicon rigs