I've an MLA-30 set up as a vertical dipole with 2m of wire on each side. I had to use a different bias-tee as the provided one killed all reception under about 500 kHz. Compared to my 20m randomwire, my noisefloor is up about 20 dB but SNR generally increased by 20-40%. I've found it to be a very effective little antenna so far. I am likely to swap out the coax and see if that improves things..
Well the MLA-30 'sort of works' and it doesn't cost very much, so it's better than nothing for folks who don't want to build their own.
You get quite a bit for your money, and it's OK for use with say and RTL dongle in direct sampling mode, but I'll probably cry the first time I see one being used with a high end receiver like a Perseus or Airspy HF :-(
Here are some measured parameters of various popular loops using the same test setup.
Well despite the rain I put the MLA-30 up in the air today.
It's a pretty poor performer, as the noise floor is about 20dB higher than any other active antenna I've tried, and increasing the amplifier gain doesn't help improve the Signal to Noise ratio.
There's also a lot of unwanted noise around 60 & 120KHz emanating from the DC-DC switcher in the Biasing Tee.
I've left it connected to one of my KiWi SDR's so that folks can try it for themselves.
Hi Martin, lots of great info. The response curve makes sense from what I was seeing moving that peak about with loop types. I think I gave it 7/10, a bit generous now I've had longer to compare over a wider set of frequencies. I've recently tried another set of dipole arms and a big copper loop, every time it was sort of interesting and in some parts equal to other antennas but never as good as the best or as consistent as other types. I can't help feeling there should be a "Mark two" from the feedback (like your observations), they obviously can produce hardware to a half decent build quality for that price so why not improve the guts? The first purchases on Ebay seemed to be speculative, testing what the UK marked would accept as a retail price, maybe we won't get a MK II as we pushed down on price.
Thanks for taking the time to run a critical eye over the design and to publish that.
However adding a 1000uF 16v electrolytic across the secondary of the big common mode choke in the "Biasing Tee" removes just about all of the unwanted noise around 60 & 120KHz emanating from the DC-DC switcher.
I think it was an oversight on their part to not include something like this.
Comments
I've found it to be a very effective little antenna so far. I am likely to swap out the coax and see if that improves things..
Well the MLA-30 'sort of works' and it doesn't cost very much, so it's better than nothing for folks who don't want to build their own.
You get quite a bit for your money, and it's OK for use with say and RTL dongle in direct sampling mode, but I'll probably cry the first time I see one being used with a high end receiver like a Perseus or Airspy HF :-(
Here are some measured parameters of various popular loops using the same test setup.
MLA-30 OIP2 approx +46dBm OIP3 approx +20dBm
M0AYF OIP2 approx +75dBm OIP3 approx +27dBm
Wellgood (Copy of early Wellbrook) OIP2 approx +57dBm OIP3 approx +37dBm
LZ1AQ OIP2 approx +79dBm OIP3 approx +36dBm
I've now added the MLA-30 information, including circuit diagrams to my Active antennas webpage.
https://www.g8jnj.net/activeantennas.htm#MLA30
Regards,
Martin - G8JNJ
Well despite the rain I put the MLA-30 up in the air today.
It's a pretty poor performer, as the noise floor is about 20dB higher than any other active antenna I've tried, and increasing the amplifier gain doesn't help improve the Signal to Noise ratio.
There's also a lot of unwanted noise around 60 & 120KHz emanating from the DC-DC switcher in the Biasing Tee.
I've left it connected to one of my KiWi SDR's so that folks can try it for themselves.
http://southwest.ddns.net:8078/
You can use my other KiWi with a Loop on the ground as a reference.
http://southwest.ddns.net:8073/
Based on my tests, I wouldn't recommend it.
Regards,
Martin - G8JNJ
lots of great info.
The response curve makes sense from what I was seeing moving that peak about with loop types.
I think I gave it 7/10, a bit generous now I've had longer to compare over a wider set of frequencies.
I've recently tried another set of dipole arms and a big copper loop, every time it was sort of interesting and in some parts equal to other antennas but never as good as the best or as consistent as other types.
I can't help feeling there should be a "Mark two" from the feedback (like your observations), they obviously can produce hardware to a half decent build quality for that price so why not improve the guts?
The first purchases on Ebay seemed to be speculative, testing what the UK marked would accept as a retail price, maybe we won't get a MK II as we pushed down on price.
Thanks for taking the time to run a critical eye over the design and to publish that.
Best regards
Stu
It's possible to use an external 12v supply.
However adding a 1000uF 16v electrolytic across the secondary of the big common mode choke in the "Biasing Tee" removes just about all of the unwanted noise around 60 & 120KHz emanating from the DC-DC switcher.
I think it was an oversight on their part to not include something like this.
Regards,
Martin - G8JNJ