G8JNJ

Hi All,

Over on Simon Brown's SDR radio IO Group, he's just mentioned the Voice Activity Detection (VAD) component of Rnnoise, and thinks that it may be worthy of further investigation.

https://people.xiph.org/~jm/demo/rnnoise/

It's written in C and is available under a BSD license, and uses Recurrent neural networks (RNN) to provide voice detection and noise suppression.

Regards,

Martin - G8JNJ

HI,

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

Hi All,

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

Hi All,

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

Could this simply be someone using a VPN that assigns a new IP address each time it reconnects ?

Regards,

Martin - G8JNJ