MFJ-1788X as a portable antenna? / What I think of the MFJ Magnetic Loop.
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- Опубліковано 20 лют 2020
- I got my hands on an MFJ-1788X mag-loop and decided to try it portable whilst away on holiday in my caravan for two days. Here's my thoughts.
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Thanks mate, super idea for my trailer, er caravan, have a used 1788. I didn't know about the inside batteries. Cheers Peter
brilliant setup using the hitch to mount your mast. very clever
Thanks for the review. I enjoyed it very much. I once had an AEA Isoloop, which was similar to this and the results were similar to what you found. I lived in an apartment and later a condo and the antenna worked pretty well. Not as well as a full sized antenna, but it helped me get out. One thing another reviewer noted about this antenna is it wasn't as noisy as his vertical and my Isoloop was the same. Maybe I'll pick up one of these for my attic space because it does make the contacts. Again, thanks for taking the time to review this item.
Did you try the loop verticaly orientated. Most of the mag loops ive seen on UA-cam were vertical. You would them have to rotate as the nulls would be on each side of the loop of course. Thanks for the video.
Wow, I'd forgotten about this video. This is one of my very early videos when I first started UA-cam.....a bit of a blast from the past!
I did do a video testing how directional the MFJ loop is. That would have been released shortly after this video if you want to take a look.
While not particularly scientific and probably flawed in my methodology, I think I came to the conclusion that a mag loop wasn't particularly directional.
Several years down the line (with more experience) I would probably amend that to say that the loop isn't particularly directional unless you are in the nulls.
The nulls are very deep, but only about 15 degrees wide on either side.
In other words, you have around 30 degrees of deep attenuation but around 330 degrees where the gain doesn't change all that significantly. There will be a change in gain but not enough for it to be particularly noticeable......thus giving the impression of being fairly omnidirectional.
Thanks for your review. Quite helpful actually.
I'm glad it was helpful. Thank you for the feedback.
I think you are honest and thats the way you all should be,
I am enjoying your experiments with the MFJ-1788. I am a fan of small things that can do a big job and have been curious about this antenna for years. From all the video and written reviews I have seen and read online, I'd say your findings are right in line with the others. I appreciate your honesty. For 10m - 20m they do sort of OK, especially with FT-8, but anything lower than 20m is a waste of time. Too bad loop antennas are so darn expensive. There really isn't that much material there. Especially with the 'Alex Loop' or 'Chameleon CHA F-Loop'. These antennas should be priced at half of what they are listed for. Then accepting their mediocre performance could be tolerated...lol! 73 my friend!
Thanks. Quite an old video this one. I'm looking to make a couple more videos on the MFJ loop as people seem to like them. The MFJ loops seem to attract a bit of a following!
In terms of my "honesty", I purchased this loop second hand on Ebay. I'm not sponsored by MFJ (or anyone else for that matter). Everything I have done so far on the channel has been funded out of my own pocket.
As long as I don't say anything which is clearly untrue (which would possibly leave me open to being sued) I can pretty much say whatever I want because I don't have any sponsors to upset!!!
I think a big part of the cost of mag-loop antennas is the big capacitors that you need due to the very high voltages. If you've seen my video "Inside The MFJ-1788x Mag Loop", the capacitors inside these things are substantial!
That said, I'm inclined to agree with you. I think that they are over-priced for what they are.
" I am a fan of small things that can do a big job" there is a joke here somewhere... Sorry I had to
@@JonathanAdami - Lol...!!! I am surprised someone else hasn't already. But of course I am referring to only radio and electronics. 73!
Excellent video ! Does the loop work better horizontal vs vertical? Also what cable are you using? Cheers..
I've not actually tried the loop in vertical orientation. Obviously it would become directional if you mounted it vertically. I didn't want to mess around with having to rotate it, which is why I went with horizontal.
In the manual MFJ state that you are likely to get better results mounted vertically if the antenna is less than 20ft, and better results mounted horizontally if the antenna is mounted at more than 20ft. I was at the crossover point, which was probably a bit of a compromise but I would have struggled to get it any higher with what I had available.
I may revisit this in the future as I would like to try it on a taller mast. Thinking that I might try it on my 12 meter mast at home, or maybe even another portable operation with a 15 meter tall mast!
The feeder cable was RG213U. Not the best cable if I'm honest as it has fairly high loss compared to alternatives such as Westflex 103 or Messi & Paoloni. It was the only piece of feeder cable that I had laying around which was long enough.
I'm not sponsored by anyone and the channel isn't monetised, so I'm working on a budget and have to make do with what I already have laying around or whatever I can get hold of on the cheap!!!
I don't even send out a carrier. You can do it just by listening to the noise signal and you will be spot on.
My personal experience is that you can get it very close by ear but it's never perfect. It's always required a slight tweak to get that low SWR. Then again, I did do around 15 years as a sound engineer/mobile DJ, so my hearing probably isn't great!
Did you only try it horizontally polarised ? This is probably not optimal for DX operation. I would be interested to see how it compares when mounted vertically. Of course then would require some occasional rotation...
From what I've read online over the years, mag loops can work reasonably well for DX when mounted horizontally AS LONG AS THEY ARE UP HIGH. Being too close to the ground in the horizontal orientation supposedly kills a mag loop's performance.
On the other hand, mounting it vertically close to the ground is meant to be good for NVIS........This would seem to align with MFJ's recommendations:-
If you believe what MFJ say, then you should get better results mounting it horizontally if it's more than 20ft above the ground. Less than that you are better off mounting it vertically according to the MFJ user manual.
In this video it was approximately 20ft off the ground, so right on that crossover point.
I did subsequently try mounting it on my 12m mast at home with a rotator:- ua-cam.com/video/aoD8gFPDXhY/v-deo.html
@@AmateurRadioUK Thank you for thorough answer. WiIl probably try out both ways but I am sure what you said is correct.
Can you say what indoor/portable antenna you would prefer to this MFJ-1788 for 40m? Thanks for your review. I'm thinking of getting on HF again but just now I'm in a temporary room at a relation's house. Is quality control the biggest weakness of the MFJ-1788 or is it really just an expensive dummy load on 40m as some have said? Both?
The antenna you would use depends very much on how much space you have available. My antenna of choice would be a huge beam on a tower, but that simply isn’t possible with my situation.
If you are specifically talking indoors then your options are limited, especially on lower bands such as 40m because the antennas are inherently quite big.
For the upper bands (such as 10m, 15m and maybe 20m) I’ve heard of people putting a dipole in the attic. Probably not practical for 40m as it would be around 20 meters long, although this could work if out portable.
Specifically for portable operation, people often use a simple dipole.
A lot of people also seem to rave about a half wave end fed (which is basically a dipole fed from the end instead of the centre).
I’ve used quarter wave verticals with great success, though watch out for people tripping over your radials if in a public place!!! Get to 40m and the antenna starts to get quite tall and you end up with quite a big radial field, though I have used this to great effect in the past.
I’ve heard quality control is a bit of an issue with these antennas, although I personally haven’t had any issues.
To say it’s a expensive dummy load is possibly a little unfair. Performance does lack on 40m compared to the upper bands and a dipole will likely easily outperform this loop on 40m. Once you get slightly higher up the bands (say 15m & 20m) I would say that gap starts to close.
For a while I had a Moxon beam for 20m on my tower. Obviously that ran circles around the mag loop........there simply wasn’t any comparison.
Ultimately a magnetic loop is very much a compromise antenna for confined spaces. There are other antennas that will easily outperform this if you have the space for them, but I don’t think that you would find anything this small that would match it’s performance.
@@AmateurRadioUK - My thoughts exactly. The Mag Loops are not the best and are indeed a compromise antenna. But if you have very little space, then the loops can be the only option making it the best choice.
How about modifying the excitation loop inside the cover so that it is oval and follows the curvature of the main loop, I have done this with mine but not tested it yet. Others who have done this have had improved performance on transmit.
Interesting idea, I will have to look into that.
@@AmateurRadioUK ua-cam.com/video/2RDtm6qXjuI/v-deo.html
73 VE7NDE
Good setup but can't help thinking a quarter wave wire with good grounding would knock the socks off it.
Hi Derek, by "quarter wave wire with good grounding" I presume that you mean a 1/4 wave vertical?
From my experience of having regularly used both antenna types, although admittedly not in a side-by-side test (another possible video there?) I would give the following analysis:-
Essentially I'd agree with that but with a couple of caviats.
For DX where a low take-off angle is desirable, I think you are absolutely right. A 1/4 wave vertical will have a lower take-off and will walk all over the mag-loop.
However, for regional work on 40m where you are relying on a very high angle of radiation (near enough NVIS), a 1/4 vertical has quite a deaf spot directly above it.
I know that a mag-loop also has a null straight up (if mounted horizontally as in this video) but in practical terms I've found this null to be so narrow that it makes little difference, even when mounted vertically on a rotator.
In short, I think the mag-loop would put out more radiation at high angles, therefore out-performing the vertical for close in (around 100-600 miles or so) on 40m despite the lower efficiency.
That said, I believe that the vertical would absolutely trash the mag-loop for longer distance contacts because the vertical will have more gain & low angles (& would also be more efficient than the loop).
What coax feeder cable were you using ?
RG-213
@@AmateurRadioUK Thanks for the info 73
Hi.. How much watts can you use max? 73 iz8dlm
I use it mainly for data (FT8 usually), so I tend to run relatively low power (anything from 5 to 50 watts).
I do occasionally put 100 watts SSB through it.
The specs online state a max power of 150 watts, although I personally wouldn't subject it to more than the 100 watts that most radios put out barefoot.
Thanks for the review. I am not convinced that you were real happy with the antenna. I have not found many people think very much good about this rig. It is expensive to not work very well. I think that I will pass.
I don't totally agree with your analysis.
Let me put it like this.......it's been well over a year (actually closer to two years) since I made this video, I still have the antenna & it has been in use at my home QTH.
I took it down about 6 months ago because it was giving a high SWR which I cannot tune out, so I need to open it up & have a look at what's going on inside it.
I have other better performing antennas but for an antenna that can be used on literally any frequency between 15m & 40m, it's hard to beat.
It's definitely a compromise antenna but for people that cannot have large antennas it might be the best they can do (and will get them on air).
Where I do agree with you is that they are very expensive.
Having to retune it every time you change frequency is a complete pain.......not a problem if you mainly run data modes (which is primarily what I use the antenna for).
I guess the question is "would I get another one"? The answer is yes, I would. That said I would get the other version which covers from 10m down to 30m (if my memory serves me correctly), because this antenna performs better on the higher frequencies. In terms of "not being real happy with the antenna" I would say that getting the 15m-40m version as opposed to the 10m-30m version is probably my only real regret with this antenna.
Despite having moved on a long way since this video was made, played with some significantly better antennas than this (including some big beams) & learnt a lot more about radio, this antenna will be going back up on the house when I eventually get round to figuring out what's gone wrong with it.
I have my big antennas for my main bands (80m, 40m & 20m) where I want the best possible performance, then use this to fill in the gaps on other bands where I'm willing to accept a compromise.
For me it's a keeper but I do understand that it's a bit of a marmite antenna that won't suit everyone, which is why I was somewhat reserved with my review.
That said I think it gets far more criticism than it's due. It has it's place.
Thanks, your controller says 1786. just confirming that your antenna is a 1788 . .
Well spotted, I hadn't noticed that!!!
Your comment prompted me to look online and I discovered that every online shop that I checked (including MFJ Enterprises own website) pictures the MFJ-1788 antenna with a controller that says 1786 on the front panel. Very strange.
As I understand it, the controllers for the two different antennas are identical (that is to say that they are interchangeable). Maybe it's a cost saving thing?
I purchased this second hand from eBay, it was advertised as a 1788. It was also supplied in the original manufacturers box, which said 1788 on the side. I didn't think any more of it!
The difference between the 1786 & 1788 is the frequency coverage. The 1786 covers 10-30 MHz, the 1788 covers 7-22 MHz. Basically it's a choice of do you want 12m & 10m, or do you want 40m.
As far as I can tell from looking at technical specifications online, both models of the antenna are physically the same size. The difference between them is the value of the tuning capacitor inside the antenna (which of course affects the frequency range that you can tune).
In short, I'm pretty sure that mine is a 1788.
If you can do 40m it will be the 1788
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