HFU HF Underground
Technical Topics => Equipment => Topic started by: alpard on August 27, 2020, 0008 UTC
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I have put out my MLA30 outside in the garden. I also replaced the stock wire like element to thick earth wire type element and made it into a perfect circle. And I put it horizontally for the omni directional reception, but about 2ft from the brick patio on the plastic box.
I have been monitoring the usual DX signals on various freq. and bands, but DX performance from that MLA30 in that location and position and height is disappointing. I couldn't hear any signals from South America on the tropical bands.
But it seems working better for 6065kHz Voice of Hope signal from Lusaka Zambia. This is one of a good DX signal to catch, and on this new setup of MLA30, that was the only signal which was a little better than before. But the rest was all very dismal.
I am wondering if there is ideal height and polarisation for better DX performance for the MLA30, or any active loop antenna in general.
Previously, the MLA30 was vertically polarised and was tied into a defunct coat hanger in the radio room upstairs. It was not the best, but about similar to what it is now = in the garden outdoor horizontally polarised on the plastic box 2ft above the ground.
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Anyone using MLA30 and how high is it set up? And how does it perform on DX on SW?
I noticed last night and this evening that my 20 meter long wire in the garden was performing far better than the MLA30+ horizontally mounted and 2ft above the ground level for copying KBS WORLD Radio.
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Well, not having one myself, so I doubt that I could really answer this. So, I'll ask, do you have a tree that you can put that loop in? Maybe try 10ft, (3 Meters), up it. Do you have a very low S/N Ratio with that antenna? If so, can you try a MW and HF preamp? Just some passing thoughts there, since a smaller loop antenna is almost always a compromise to a 1/2-wave dipole, or even a random length wire antenna.
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Thanks Dood.
Well, I have a few trees in the garden, but they are far away from the house. The feeder of the MLA30 is not very long about 3-4meters? My radio room is upstairs in the house, and when the feeder comes out the window, it really does't stretch far away until it runs out. So, it is sitting on the patio on the plastic box 2ft above ground.
But you know what? I saw a DXer who uses Wellbrook loop and his loop is actually hammered into the ground, and he catches all the good DX with it. So I was under impression that with the loop antenna, they don't need much height.
But my MLA30 was not copying great DX. It copies very nice if the signal is not DX and in good strength from all over Europe. It copies beautifully. But I was trying to copy the weak DX signals Txed with 1 - 10 KW from South America, and they are not heard.
I know the signal is there under the noise, but cannot read what it is with this MLA30. So, I thought maybe it needs height? And would it be better with vertical polarisation? I was asking these questions to myself, but wondering how other DXers use the MLA30 for their DXing. :)
I now concluded that one thing definite in this game is that, it doesn't matter what radio you have. It is the antenna which will make it or break it as far as DXing is concerned. I think your DX-440 or my D-808 will copy that DX signal no other radios costing 20 - 30 times more can hear, if they were fed with good efficient DX antenna set up with right height and location.
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If opting for horizontal polarization, you need to get it as high as possible due to incurred ground losses, especially weighted against the already small capture area.
My advice? Vertically polarize it to minimize ground loses for now, as it can be rather low to ground and still work okay. If you do not have a rotator, your best bet is probably pointing it to null local noise as best as possible. Turn to the noise floor hopefully drops to its lowest, then set and forget. :)
BTW, low horizontal loops can work. In fact the design of my loop-on-ground works in part due to ground losses, but it is also 148' in size.
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I am gonna try vertically setting the MLA30 up this weekend.
I will need a pole and some tripod type stuff making it stable.
I didn't know that RX antenna will suffer from the ground loss. Is it not the case for TX antennas only?
But maybe it does. The MLA30 horizontally lying on the plastic box 2ft above the ground, was not copying any DX signals at all.
On the tropical bands at night, the band noise increased with the MLA30, but no signals were heard. :(
I had to switch back to the long wire, and it sounded more pulling the weak signals than the MLA30.
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I have a W6LVP. From my research, I mounted it about 10 feet off the ground, vertically. Hope this helps.
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I have a W6LVP. From my research, I mounted it about 10 feet off the ground, vertically. Hope this helps.
Thanks for your info.
This evening I moved the MLA30 and put it on the ladder shaped as a long A. On the top of the A shaped ladder, I could VERTICALLY hang the MLA30 element made of hula hoop with thick earth wire all around it kindly donated by my xyl. The height is now about 7ft off the ground.
It seems working really powerfully well on 11 - 15Mhz. But from 9Mhz and below is full of MW stations breaking in. The worst is 4Mhz. On 6, 7 and 9 Mhz it is sparse break through from the MW stations. But on 4 Mhz, every part of the freq is filled with some strong MW stations.
I am not sure if that is due to the fact that the hula hoop is a about twice of the diameter of the original wire element, and also the supporting ladder is made of aluminium, and it is making the MLA30 about 4 - 5 times larger element than the original one, and causing horrendous overloading on 4 - 9 Mhz? Worst being the 4 Mhz. :(
Will keep experimenting with this trying to get best from the MLA30, but I am not sure if that is the limit.
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It seems working really powerfully well on 11 - 15Mhz. But from 9Mhz and below is full of MW stations breaking in. The worst is 4Mhz. On 6, 7 and 9 Mhz it is sparse break through from the MW stations. But on 4 Mhz, every part of the freq is filled with some strong MW stations.
I am not sure if that is due to the fact that the hula hoop is a about twice of the diameter of the original wire element, and also the supporting ladder is made of aluminium, and it is making the MLA30 about 4 - 5 times larger element than the original one, and causing horrendous overloading on 4 - 9 Mhz? Worst being the 4 Mhz. :(
Will keep experimenting with this trying to get best from the MLA30, but I am not sure if that is the limit.
The amplifier is being overloaded.
Here's the problem (both in this case and with many active antennas in general):
Because the actual antenna element is small, the output signal from your shortwave DX station of interest is small. If your receiver is not very sensitive, you need an amplifier before it, to amplify that weak signal. But... local MW stations (and maybe even FM stations) still produce a strong signal. And that gets into the amplifier also, and overloads it, causing images all over the place.
What's the solution?
One solution of course is a larger passive antenna, but you don't have room for that. What's another solution? Well... it's a better receiver. For example, the AirSpyHF+ / Discovery can work surprisingly well with a small passive antenna, such as the YouLoop. (Note I am referring in this case to this specific receiver. This is not generic for all SDRs.)
You could perhaps try putting some filters between the antenna and amplifier to alleviate the overloading/images, but 1) that might be difficult based on the design and 2) you're rapidly approaching what I like to call "lipstick on a pig". :)
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Most things considered, RX and TX are reciprocal for antennas. :) If you have high losses for TX, then you will have high losses for RX; be it ground losses or whatever. Same goes for gain, directivity, take off angles, and lost of other factors.
The difference is RX losses can be easier to overcome, like via the preamp in your active antenna, plus modern-era receivers have incredible gain. In other words, as long as there is a signal to discern, you can typically turn up the receiver volume to compensate for the lack of antenna gain.
As Chris noted, an amp in your RF chain likely is being overloaded. It is probably the inexpensive amp in the active antenna. You might try a smaller loop to limit capture area, thus lowering the input into the amp. First try going back to the factory-included wire loop IMO.
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Admittedly getting into the lipstick-on-the-pig territory, a few of many possible options in increasing order of expense:
* The receiver could be overloading, too, thus overrunning its own selectivity. If the receiver does not have an attenuator or RF gain feature, you can toss together a cheap 10-20dB pad attenuator with a few basic resistors: four for a pi network or three for an even simpler tee network. Like a couple of dollars or less. It is also a good basic RF building project. Lots of designs on the net. Drop a search.
* There also is the option of a high-pass filter to heavily attenuate the MW band to essentially "knock out" AM broadcasters. You can get a basic model via eBay for under $20, but do not expect miracles, especially if it is the active antenna preamp overloading. Ideally the filter needs to be *before* whatever is being overloading, which again I would suspect is the active antenna preamp.
Assuming you actually do live next door to an AM broadcaster, there are better high pass filter options to build or buy. Personally I can attest to the build quality of the PAR BCST-HPF, which uses a 7th order elliptic filtering network, but it also costs ~$70 new.
* A potentially more comprehensive solution could be a preselector, though that can get into serious annoyances due to keeping its tuning in sync with your receiver as you change frequencies. Again, though, it really needs to be before whatever is being overloaded, so it is not really where I would start with your current situation.
I have used various revisions of the MFJ-1045 as preselectors for years, especially with portable receivers. Such active preselectors tend to include preamp, attennuator, and preselector features in a single package. There also are passive models without integrated preamps, which can be preferable when needing extra gain is not an issue, as there is no active circuitry to generate more RF. Either way, the biggest downside IMO? Cost if buying instead of building. Most decent models are around $100 to $150 new.
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Great info & advice. Thanks.
Yeah, all true. I have tried different receivers with the new set up of the MLA30. They are the Tecsun S2000, Sangean ATS-803A, D-808 and a vintage Yaesu FRG-7, and they were all the same, serious overload throughout 4 Mhz.
What I have done at that moment was inserting a 0.001 uF capacitor between the antenna and the receiver, and Voila the Images disappeared.
I was wondering if it made the receivers deaf too. But it was copying Radio Havana 5025 kHz and 5040 kHz very well. So that wasn't the case.
Again I was wondering if high grade SDRs such as AirSpy or SDRplay duo, or even the new RX666 or RX888 would perform better with these images problems.
Anyhow, I failed copying the target DX signals (the low powered BC stations on the tropical 4 Mhz band from South America) last night with every receivers and antennas I tried. Maybe there were no propagation? I am going to try again tonight, but this time, I will set the MLA30 horizontally on the A shaped ladder. I think it will anchor at around 3ft off the ground on the A shaped ladder. If it still overloads, then I will go back to the original wire element.
If it works well, I wouldn't mind even putting on bikinis to the pig :D
73s
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What I have done at that moment was inserting a 0.001 uF capacitor between the antenna and the receiver, and Voila the Images disappeared.
I was wondering if it made the receivers deaf too. But it was copying Radio Havana 5025 kHz and 5040 kHz very well. So that wasn't the case.
IIRC you are using an active antenna. *Where* was the capacitor placed? Between the DC power inserter and receiver, or antenna and DC power inserter?
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What I have done at that moment was inserting a 0.001 uF capacitor between the antenna and the receiver, and Voila the Images disappeared.
I was wondering if it made the receivers deaf too. But it was copying Radio Havana 5025 kHz and 5040 kHz very well. So that wasn't the case.
IIRC you are using an active antenna. *Where* was the capacitor placed? Between the DC power inserter and receiver, or antenna and DC power inserter?
I have a capacitance box with different capacitance settings. It has 2 alligator clips for clipping things onto. I have clipped one to the wire antenna input of the FRG7, and the other clip to the antenna. The FRG7 is fed with a cable one end has two clips and the other end has a stereo 3.5mm input jack. The two clips go to the antenna and earth input of the FRG7, and the female stereo jack is inserted with the MLA30 ant. output.
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This evening I moved the MLA30 and put it on the ladder shaped as a long A. On the top of the A shaped ladder, I could VERTICALLY hang the MLA30 element made of hula hoop with thick earth wire all around it kindly donated by my xyl. The height is now about 7ft off the ground.
It seems working really powerfully well on 11 - 15Mhz. But from 9Mhz and below is full of MW stations breaking in. The worst is 4Mhz. On 6, 7 and 9 Mhz it is sparse break through from the MW stations. But on 4 Mhz, every part of the freq is filled with some strong MW stations.
I am not sure if that is due to the fact that the hula hoop is a about twice of the diameter of the original wire element, and also the supporting ladder is made of aluminium, and it is making the MLA30 about 4 - 5 times larger element than the original one, and causing horrendous overloading on 4 - 9 Mhz? Worst being the 4 Mhz. :(
AFAIK, there should be no metal parts inside or near the loop, except the connection. All successful receiving loops are supported with wood or plastic braces and poles.
The polarisation is of no importance for receiving SW skywaves as they are of mixed polarisation, but it can be used to cancel direct wave interference (or RFI) - as well as orientation in vertical or slant position. Close to the ground, probably the loop should be left vertical.
Any screen around a loop should be open, not being a closed loop. Then it should be balanced too, not to become part of an antenna near the loop. Before using a screen, try without any screen or metal parts near the loop!
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Regarding the inquiry about propagation, yeah, it has been in a deep hole in the past day or so. There was a geomagnetic store with a residual high Kp index for many hours.
Ray also offers sound advice. There should be no metal objects near your active loop. Get a plastic pvc pipe, wooden broom handle, or similar to mount the antenna.
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I have two suggestions (well two and a half):
1. Build a crossed parallel loop using a LZ1AQ pre-amp. I built one several years ago, and for the size it works extremely well. The LZ1AQ amp is well designed and is going to have much less overload and added noise issues than the video amp that comes with the MLA30 & friends. Yes, it's going to cost considerably more that what you have now, but it's also going to work a lot better. It's even directional on MW and LW. If you search here on the HFU you will find posts about mine as well as links to blog posts where I detail the construction.
1b. Alternately you can start small by getting the LZ1AQ amp and connecting a single small (say 1 meter in diameter) loop, or a pair of small loops, which is going to take much less construction time.
The next question is what receiver to feed this into. You said you have an FRG-7? That may be your best bet (of the radios you have now), assuming it is working correctly Portables, as well as portables masquerading as communications receivers, have their own issues which several of us have detailed in this thread (and maybe others, I have lost track).
2. Get an AirSpyHF+ Discovery and build/buy a YouLoop or similar. Not an SDRPlay. Not some Chinese "16 bit A/D" SDR we know nothing about. An AirSpyHF+ Discovery.
Of course these lead to:
3. Build a crossed parallel loop and connect an AirSpyHF+ Discovery to it :) I've done this myself, and actually run the loop *without a preamp* and just connected it to the Discovery, using a transformer. It worked amazingly well.
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Thanks for your suggestions.
But I have purchased the MLA30 after seeing this youtube review.
https://www.youtube.com/watch?v=k4G71UrANtA
https://www.youtube.com/watch?v=NB8RBEI-1xk
https://www.youtube.com/watch?v=GNN6T4C4dRk
It is supposed to be the best Active Loop Antenna on the market 2019 :)
Again it is not the best, but I don't want to spend more money on the antenna at present.
So, right now I am just trying to stick with it for a while.
It seems that it could be improved by playing around with the location and height and the length of the element as well.
And for AirSpy, I am not sure if it is a good buy at this point in time.
I read that some people had experience of it dying after less than a year of use.
And the new SDRs are coming out in the market, so it is maybe time to sit and wait?
And on the building these preamps and stuff, I was into the DIY kits and building things before, but I stopped it now. Because when you build these things, you loose time to listen to the actual radio, and end up just fiddling with the kits spending a lot of time on it.
I now decided just sit and play with the radio when I have spare time. :D
But thanks for your suggestions. Much appreciated.
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Hmmmmmmmmmmmm, yeah... I could see not wanting to spend time on kits, when you could be DX'ing. Then again, look at the experience that you gain 1st hand from building your own stuff, then document it to either repair later, (When necessary.), or to add a modification to it. BTW, using that "S" meter in that FRG-7, (Or as we use to call it, The FRoG-7.), is a nice visual indicator to use. So, I'm with Chris on that one. That, and if I remember right, the RF Gain is very useful there as well for incoming signal tests on that rig.
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The big issue for weak signal work with the FRG-7 is the very wide stock filter(s). Great for broadcast radio audio quality. Not so great for digging signals out the noise floor. It does at least have a potentially useful selectable attenuator, plus its Wadley loop circuit design still is subjectively better than even many modern superhet portables.
BTW, be careful with static discharge into the FRG-7. I recently had to replace the front-end FET in mine. It is a common issue, especially since the original FET lacked internal diodes for static protection. There are newer equivalents and compatibles, but I managed to find a new-old-stock 3N211 that was the recommended replacement back in the day. Includes integrated diodes, too.
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Alpard, you might not need an active antenna at all, particularly if targeting the tropical bands. I suspect your wire antenna(s) have more than enough gain for the purpose. If the noise floor appreciably increases when hooking up the antenna to the receiver for the desired band, then you likely have enough viable SNR to start hunting and listening.
Curious, do you have a balun, choke, etc. on the passive longwire antenna? If not, I suggest winding or buying one. A basic 9:1 balun for a random length longwire can be purchased for like under $15 on eBay. There might be better ratios for your particular antenna, but 9:1 is a good generic place to start for receiving longwires. It should help limit common mode noise if nothing else.
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I live in Florida next to the tropics, complete with routine thunderstorms, static crashing, etc. The below link is a quick video of the 80m amateur radio band taken earlier tonight using a Airspy HF+ Discovery and a mere 9' vertical ground mounted over just four 9' radials. No preamp, yet note even it has more than enough gain for the purpose. My larger 31' vertical should increase the detected signal strengths, but SNR likely would be similar since it would increase the noise floor as well, so it largely is a wash.
https://www.youtube.com/watch?v=ZG0WvQuNiVc
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FRG7 doens't have RF Gain control, but a selector for DX LOCAL and NORMAL. Depending on the incoming signals, it is very effective sometimes. But when I was repairing and DIY making stuff, I couldn't find the time for actual BCL / SWL at all. I concluded that I must do just one thing, because time is not allowing for doing various other stuff in life. DIY and Repair work could be fun and rewarding I suppose, and if one can do it very quickly in no more than an hour for finishing the repair or build, that's ok. But in my case it went on and on, and in the end, many projects just kept piling not getting finished off :( At the point, I just stopped doing it altogether, and now try not to get my hand dirty with DIY or repair stuff, if I am not sure how long it will take, or if I could just buy the new stuff for cheap.
Yes, I am very conscious of the the static noise damages to the front end, and whenever I change the antenna, I ensure the radio is off. But then there is also static noise problems when the neighbours use their electrical tools such as the angle grinder, electric drills and saws. And when my daughter and XYL use the food processor and grinder in the kitchen, the high level of statics can kill the front end of my radios :( I quickly switch the radio off, and so far there were no static damages to my radios.
I was also thinking about the balun, and I could make one for 4:1 because it can be made without the ferrite core, just by using a plastic tube from youtube and it looked simple and cheap enough. But for 9:1 balun, I think I must buy a ferrite core which is not cheap.
I try to use simpler and cheaper and older equipment and device for my SWLing and DXing, because it is just my hobby :)
And OK, if I had my court settlement from the inheritance this year which had been going on for last couple years started by my stepmother and brother, then I will get hold of some substantial amount of funds, and will be getting all these high grade receivers and antennas and filters in the new radio room - I am going make one in the corner of the garden.
But before that, I must try keep frugal with all the expenses and should not just keep buying new devices just because the MLA30 is not working for my DXing right now or AirSpy is supposed to be good etc. :)
Anyway, I think MLA30 will work well for DXing, but it needs to be set properly with the height and ideal spot in the location and also the element could be adjusted for the band that I am wanting the DX signals monitored. And this is just part of the fun in the hobby. If all was just hunky dory easy and no problems due to having used the most expensive devices in the market, maybe at that point, the fun could disappear. :)
I wonder if 4:1 balun could be also effective on RX in HF. And my wire antenna is now in loop configuration. I added some more wire, and made into a delta shape, and I am using also the AMECO PCL-2 loop tuner. This AMECO loop tuner is very powerful device. It is a preamp, but also active antenna. It can really increase the gain of the wire loop. It makes the weak signals a lot more readable state. But even with this I couldn't copy the DX signals on the tropical band last night.
With the MLA30 on horizontally set on the ladder, the MW images all disappeared, but there is some static noise on the 4-5 Mhz.
But it copied signals on 80m ham band really well. There were some signals not audible on the wire loop and Amoco, when changed over, the MLA30 copied with 59+, I couldn't believe it. Anyhow, the 4Mhz tropical band got very noisy as the night got late. It sounded exactly same as the 6m and 2m band is just about open with the Aurora. Very loud band noise were all over the band, but it was getting too late, and no signals were heard. I thought maybe another hour, when it is 2-3 am in the morning, some DX signals might appear, but I was damn tired as it was getting well past 1am, so just went to bed.
I have been to Florida many times years ago, when my parents used to live there in Orlando, and there are some of my relatives still in Orlando. At the time we drove to Tampa, Miami and Fort Larudale and Key West, and toured the Hemingway house etc. It was a great time. When we stopped by the beach in Tampa, there were some huts and wood stove in there, and we had barbecues and drinks ... :)) Good memories in there. But yeah, I do appreciate your comment on the static noise in Florida, because it had sometimes very severe rain with thunder and lightening suddenly. Here where we are in UK, we just get drizzling rain a lot but thunder and lightening is very uncommon thankfully. It happened a few week ago, and it was bad. Even a few hours before the actual thunder and lightning were coming to my area, the HF was very noisy and couldn't hear much. I left all the radios unplugged from the mains for the night. There is usually weather warnings for sever thunder and lightening from the weather centre but still have to be aware of it all the time I suppose. One of the Karma stuff of SWL. :)
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Managed to pick up a rare DX with the MLA30+ last night albeit very weak signal, I could hear it.
It is Radio Logos from Peru Txing with 1 kW and distance from me is 12,000 km. Not bad with a 29 Euro active loop antenna :D
https://twitter.com/Radio0Play/status/1300372125673549824
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Managed to pick up a rare DX with the MLA30+ last night albeit very weak signal, I could hear it.
It is Radio Logos from Peru Txing with 1 kW and distance from me is 12,000 km. Not bad with a 29 Euro active loop antenna :D
https://twitter.com/Radio0Play/status/1300372125673549824
Hopefully you actually had an ID. Your Twitter video posting had no intelligible audio.
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Managed to pick up a rare DX with the MLA30+ last night albeit very weak signal, I could hear it.
It is Radio Logos from Peru Txing with 1 kW and distance from me is 12,000 km. Not bad with a 29 Euro active loop antenna :D
https://twitter.com/Radio0Play/status/1300372125673549824
Hopefully you actually had an ID. Your Twitter video posting had no intelligible audio.
True. It was just trace of weak chorus in the fading signal. But I was sure it was the signal, because I heard some other SA stations on the other frequencies on 4885 4775 very strong last night. The path was open. But Radio Logos TXing with 1 kW, I was only grateful to get the glimpse of the signal :))
It is regarded as not copyable signal in Europe in normal situation due to the distance and its TX power, no matter even when the highest grade antennas and receivers are used. I would have thought something is not right, if the RL signal were stronger and more intelligible than that, when copied in utmost northern Europe using a 29 Euro MLA30 Active Loop Antenna and Tecsun Radio. :)) Not knocking down on the equipment, but there is no record of reception on the Radio Logos signal in whole Europe, I tried to search. It is just a couple of same fuzzy noise reception videos from whole Europe available in the search. If you were copying it from America, Afria or Australia or even in Asia, maybe it could be different story.
Even if the signal was strong, I wouldn't understand a word they are saying mostly, because I don't understand Portuguese or Spanish, so not sure if I could catch the ID. usually I just check it on the SW schedule site, or WRTH or with Google and that's it. But next time, I will try check going to one of the KiWi SDR in the country or continent where the TX signal is coming from.
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Hopefully you actually had an ID. Your Twitter video posting had no intelligible audio.
True. It was just trace of weak chorus in the fading signal. But I was sure it was the signal, because I heard some other SA stations on the other frequencies on 4885 4775 very strong last night.
It is regarded as not copyable signal in Europe in normal situation due to the distance and its TX power, no matter even when the highest grade antennas and receivers are used.
You believe you received a low power Latin American station, that apparently has never been logged before in Europe, using a MLA30 antenna and Tecsun receiver?
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Hopefully you actually had an ID. Your Twitter video posting had no intelligible audio.
True. It was just trace of weak chorus in the fading signal. But I was sure it was the signal, because I heard some other SA stations on the other frequencies on 4885 4775 very strong last night.
It is regarded as not copyable signal in Europe in normal situation due to the distance and its TX power, no matter even when the highest grade antennas and receivers are used.
You believe you received a low power Latin American station, that apparently has never been logged before in Europe, using a MLA30 antenna and Tecsun receiver?
Never said that. I said, the Radio Logos from Peru with clear intelligible signals videos copied from Europe is not coming up on the Google search.