Hi everyone, thanks for your interest, it's worth tinkering with.
My technical adaptations use common knowledge described on the web, but I will add some details:
- the MLA box is solidly made of white ABS and has 4mm thick walls, so it won't deform easily or crack quickly. Colleague Ray rightly suggested to protect the material against UV degradation by spraying with varnish.
- the lid of the box is solid and has a channel with a well-fitted gasket, but the cable passes through the opening in the box without a sealing gland. There is enough space to fill a BNC, F / TV or SMA socket tightly. The socket can be easily soldered to the cable inserted into the amplifier board, without interfering with the board, it is flooded with black hard resin (probably epoxy) and the gouging will result in tearing off the elements and damaging the board.
- the loop is screwed through M-4 (stainless) screws through the box walls. In my opinion, it is worth sealing with epoxy resin, and on the outside of the box put (stainless, epoxy) washers to strengthen the mechanical connection with the loop. A large loop under wind pressure can exert considerable force on the box, and the box transfers it to the pole supporting the antenna.
- I have 3mm thick Ag / AL wire and I wanted to make a new loop larger than the original one. I had to slide it into a PE / AL layered pipe to shield against electrical interference from industrial interference signals.
I searched my apartment for the source of interference using the original MLA loop. It turned out that the TV, cable tuner, router, power supplies, computer, lighting and neighbors do not sow them into the environment (at a noticeable level).
In this situation I gave up shielding the loop and made a large loop from the pipe.
Both ends of the pipe, about 3 cm long, must be flattened by crushing and then bent 90 degrees to allow it to be screwed to the MLA box. The aluminum layer is thin and breaks when bent, so the bend must be made on a flat length before you remove the PE layer. It is best to remove the insulating PE coating (about 2 cm) with a hot tip of the (large) soldering iron. Now drill holes for screwing the box. Screw the loop through the washers to ensure good electrical contact with the pipe surface and strengthen the connection.
- as I described in the previous post, the antenna works great if the large loop is tuned to resonance with a variable capacitor (or varikap), and the MLA amplifier box is connected to a small coupling loop (1 / 5D). The signal strength (and noise increase) is so high that it requires optimization of gain and attenuator - both blue potentiometers are visible in the pictures.
It is possible that even better results will be achieved by optimizing the degree of coupling of a small loop with a large one, but I haven't had time for it yet.
- DC 12V stabilized voltage is fed to the MLA amplifier with an antenna cable. There on the plate it is probably reduced to 8V resistors which is optimal for a well-integrated differential amplifier. I advise against gouging in resin - experiment safely with the voltage supplied through the cable.
- In the "Biasing Tee" box you can safely gouge: increase the capacity of electrolytic capacitors, bypass the DC 5 / 12V converter, change the USB power socket and SMA sockets connecting to the antenna and receiver.
- I use a widely available, convenient and good for HF coaxial cable type RG6. I use SMA / F or SMA / BNC adapter connectors, sockets, plugs and F connectors for TV installations, as required.
Good luck and write about your experience!
For the record, here is the schematic diagram of the MLA-30 system
https://www.g8jnj.net/activeantennas.htm#MLA30
