Need advice on filter/noise cancelling

[gcopter1]

I live near broadcast antennas that bleed all over my shortwave listening. I can rotate my loop to pretty much null out the broadcast antennas and at the same time lower the noise floor. However, if I wanted to keep searching for distant AM stations, I need to rotate the loop, but the noise returns along with the bleed over from the nearby broadcast antennas. Would a noise cancelling device such as the MFJ-1025,6 do dual duty for lowering my noise and null out the bleed over? Or should I just get an AM filter and deal with the noise separately?

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[SCPD]

It depends on what the exact issue is... the question is whether the MW energy bleeding into your feedline and creating images or is it just a signal / overloading issue.

The cheapest solution to try first would be a BCB filter. For SWL, I use the Clifton Z10023A filter. Jack tweaked mine slightly since my biggest AM offender is around 1540khz. Mine technically breaks into the 160M ham band but I rarely monitor it anyway. Mine doesn't have a pass-thru switch but I'm sure he could add one for you if requested.

You can find used BCB filters for quite a bit cheaper but you get what you pay for -- a quality filter is important.

You may find that you need both a filter and a phase cancelling device to really help with your dilemma but I would start with the BCB filter. Quite honestly, anyone remotely close to a major city should have one anyway for SWL monitoring.

http://www.cliftonlaboratories.com/z10023a_elliptic_high_pass_filter.htm

 

[gcopter1]

I thought about getting the filter first because is the cheapest solution. Did not knew I could end up using both devices but after seeing the description for the MFJ, thought I could kill two birds in one shot.

 

[k9rzz]

Is it one station causing you grief or more than one? If just one, then maybe you could build a tunable notch filter for that one frequency, knock them down 30 to 40db and not kill the whole AM BCB band for DXing.

 

[gcopter1]

Less than a mile away from my home, I've got WINZ 940 AM. And within a 3 mile radius there are 6 FM and or TV stations. To be honest, not sure which one is causing the interference, but pretty sure by distance alone, has to be the AM station. Also, while tuning on the AM bands and a little bit above, have heard the same station(s) in more than one frequency.

 

[SCPD]

Yeah it could just be RF overload. I have something similar going on at my QTH. The AM station that hurts me drops down to 5,000 watts at night so it's not that bad but during the day it's up to 25,000 watts. Grr!

 

[gcopter1]

Well, payday is rapidly approaching and I will be making a decision soon. For now, I've found an MFJ 1026 only $15 bucks above what a PAR filter would cost me. I think I will get this instead as I really see no reason not to buy something that can do both things. On the one hand, the filter, will take care of my bleed over on the AM bands, but I would still have to contend with the noise problem that I think I have nailed due to the fact that by rotating the loop I can see my noise floor drop dramatically. Whenever I get the device, will repost with results. Thanks to all who have contributed.

 

[a29zuk]

I have the MFJ 1026 and it works great for eliminating noise. But make sure you put up a good outside noise antenna. The whip antenna that comes with the unit does not work well for eliminating noise. The key is to have both antennas tuned to the same signal strength before using the phase control.
On the AM band, with two antennas within a half wavelength from each other, I can phase out the local stations and hear what is behind them. This eliminates the need for a loop antenna.

Good Luck.
Jim

 

[gcopter1]

Jim, I have a Wellbrook loop. When you say " half a wavelength ", could you please explain further. My understanding is that I would need another antenna wire that can hear in the same bands as the loop? Could I just lay out some cooper wire, attach that to some rg8 I already have laying around from a previous antenna? I live in a trailer home and I think there's not much more difference in the noise level in or out due to the fact that my loop sits only, maybe 15 feet away from the radio inside and am surrounded by metal.

 

[Boombox]

What kind of radio are you using?

If you're getting a lot of WINZ bleedover on the AM band, and you're trying to DX the AM band (as you mentioned you sometimes do) it my not just be the antenna set-up, it could also be the radio.

Some radios just can't handle high local RF levels as well as other radios, whether its interference in the AM band or SW bands.

Have you tried a different radio?

 

[a29zuk]

Jim, I have a Wellbrook loop. When you say " half a wavelength ", could you please explain further. My understanding is that I would need another antenna wire that can hear in the same bands as the loop? Could I just lay out some cooper wire, attach that to some rg8 I already have laying around from a previous antenna? I live in a trailer home and I think there's not much more difference in the noise level in or out due to the fact that my loop sits only, maybe 15 feet away from the radio inside and am surrounded by metal.

Sorry, I've been pretty busy working overtime, and haven't been on the website in a while.
That's an interesting question. I've never used the 1026 with a loop antenna! I didn't know you had little room to work with antenna wise. The 1026 works best with two random length antennas about 5' to 15' apart.
All I can say is lay out some copper wire and give it a try! Otherwise you may need a tight preselector or notch filter to cut that local station out.

Good luck,
Jim

 

[gcopter1]

a29zuk, thanks for the reply. I've gotten the filter, I'm still getting some bleed over, but not as bad as before. The literature that came with it, explains it, if I live nearby, I'm SOL. Now I'm finding that with the filter online, wether on or off, I'm not receiving wefax broadcasts as strong as before and rotating the loop, does not help much. I will remove the filter from the line, and try again receiving those wefaxes. If it works, I'll be getting a Par end fed antenna, then the MFJ 1026. I might end up moving from this home soon. If I do, I'll hold up getting the wire antenna and try again with the loop. It was working very well before and unless propagation is bad as of late, then the loop maybe too much of a good thing. I might also try putting it up higher as it now sits 5 feet from the ground.

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