Are Preselectors Useful For MW Listening?

[cc333]

I have an MLA 30+ loop and Radioshack DX-398 radio, and while reading a recent thread here, I was wondering if a preselector would be useful for AM (MW) DXing?

I've tried using a Tecsun AN-100 tunable loop antenna with it's output connected to the MLA 30's output, which seemed to offer an additional boost (this was the setup that enabled me to catch one of those DX tests from MT a few weeks back; neither the AN 100 or MLA 30 individually were able to pull it in, but this combination of both did).

Thanks!

c

 

[merlin]

For weak signal work below 75 Mhz, they make a vast improvement.
A good one will have bandpass filtering, low noise preamplification, and at least ,10 Db step attenuation.
Weak signal AM DX can be tricky for local BC. the use of a variable notch filter can help that. A secret to SWLing is not amplifying the desired signal, but getting rid of
unwanted signals and noise.

 

[ka3jjz]

Careful now. The MLA loop already has 20db or so of gain, and you add too much gain from an active preselector and overloading / noise is a distinct possibility, particularly with old portables such as the OP is using, or a SDR like the RTL stick. It's dependent on your RF environment, of course.

A better solution- particularly in urban radio with dozens of AM stations in the area - is a passive preselector (one that has no gain). It will still act like a gate and reject out of band slop without the hazards of overdriving the radio. The idea of tuning the output of the loop is sound - it just needs to be handled with some RF care.

I'm unsure whether the below model would handle a loop, but it's a good example of one that goes right down to LW. It's not really an antenna tuner - that term has been misused for years.

MFJ-956, ANT. TUNER, VLF/MW/SWL, 150 kHz TO 35 MHz

VLF/MW/SWL 150 kHz to 35 MHz Antenna Tuner Boost your favorite stations while rejecting images, intermod, and phantom signals! The MFJ-956 Pre-Selector/Antenna Tuner greatly improves reception from .15 to 30 MHz -- especially below 2MHz. It has tuner bypass/ground receiver positions. The...

mfjenterprises.com

Mike