SWLing with SDR in high noise environment

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markolinux

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I keep coming here via Google searches on various topics, so I thought I'd join the fun. :^)

I have been a SWLer / DXer on HF for about 35 years now. My involvement in the hobby waxes and wanes, but never goes away completely.

I'm currently looking into getting an SDR, but have seen in lots of reviews that local AM and FM stations can be problematic for SDR receivers. Stations nearby (within 2 miles):

AM station on 1270 - 5kW day / 1kW night
FM station on 104.7 - ERP of 50kW 24/7
FM station on 97.7 - 6kW ERP 24/7

The radiation pattern of the AM station is stronger in my direction.

There is also quite a bit of hash from nearby houses, even though I'm "out in the country".

So.... if I end up buying an SDR, I have a couple of questions:

1. Will I need to purchase other equipment (preselectors, filters, active loops, whatever) to operate SDR without overloading?
2. Are there SDR radios that perform better in such conditions?

I want to try out SDR, but am wondering what all will be needed for budgeting purposes. It might be too expensive to "try out" if I have to buy a bunch of other equipment to make it enjoyable, considering my location.

I couldn't decide where to post this, so I put it here in the general discussion forum for shortwave, since shortwave listening is what it's all about in the end.
 

ka3jjz

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Well let's start with what SDRs could be used for HF listening - our wiki has several of them, grouped by general frequency coverage

Software Defined Radios - The RadioReference Wiki

I can see where the FM stations might give you some problems. No doubt a FM trap would be a wise investment to block these.

The AM station might be a bit more problematic depending on the antenna you use. I would think that using a Wellbrook or Pixel on a rotator would be able to reduce the amount of energy you get from that station - but perhaps better would be an AM filter to block this out as well

Daisy chaining filters together can be a tricky business, and frankly something I've never had to do. Perhaps someone here can get some advice on that

It's been reported that the otherwise excellent Elad FDM-S2 sometimes has issues with strong BCB stations in the vicinity. The very-expensive Perseus seems to do better, since it has better front end filtering. I suspect, though, that no matter what you get you will have issues with those FM stations being so close.

A passive (not active) preselector might well be the answer here - somewhat expensive, but how is it against buying a series of filters is something to consider.

Most all of these SDRs have Yahoo mailing lists, and once you have settled on which one you want to get, I'd suggest joining one of them and asking questions along this line. Some are even hosted by the creator of the unit itself (such as the AFEDRI) which gives you a potentially very useful way to get information. We have some of these in our wiki as well (at the bottom of the article)

Mike
 
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