QRM antenna

[johnkyrle]

I have read somewhere but for the life of me cannot find it again that you can construct a loop antenna that attracts QRM signals.I have just installed an IMAX 2000 and have noticed that the QRM is higher (obviously) compared to my Sigma Venom 5/8,due to the IMAX being more efficient.
Anyone any ideas?Apart from the QRM eliminator from Germany which,at the moment,is out of my price range.

[Admiral]

Good luck getting an answer to your question as it makes no sense to me whatsoever.

[WeatherWatcher]

viewtopic.php?f=2&t=52872
This thread might help

[paulears]

Remember that aerials don't attract anything - so perhaps 'capture' would be a better word. QRM is just unwanted noise, and the opposite is the wanted signals. Any antenna design should work as well as possible at capturing whatever is in the ether. They have performance that can be measured - gain, bandwidth and some have directional properties. Loops are a good example - they're physically small normally, so not that good an aerial one would assume, but they have very deep nulls - ships used them for years for direction finding. Twist them around till the signal disappears and then you'd know exactly where the transmission came from. An omni design might get swamped by all sorts of noise you don't want - which is where it might appear it attracts interference - it doesn't it captures it.

That QRM eliminator is a simple gadget that nulls out unwanted noise by phase cancellation as said already. If it works, that's great - but it isn't that clever.

If the Imax picks up more QRM, it will also pick up more signal. This is simply signal to noise ratio. If two aerials produce the same wanted signal but different unwanted noise, then they must be different in polar pattern, or have different reception angles - ones that capture from the noise direction and not so much from the wanted signal direction. Noise from the local welding workshop might be horizontal, but the weak signal from abroad coming down at an angle?

[DaveP]

Don't waste your cash or time getting a QRM eliminator, all it does is act like a pre-amp but in reverse, so not only will it cut down QRM but also readable signal. You have not said what band you are on or what coax you are using?? Have you fitted a balun?? If not very easy to fit and make your own, once done it should cut down the unwanted noise dramatically. I am assuming you are on 11 meters, un-screw the coax from the antenna and using a coke bottle, tin of beans or any circular object with the diameter of 4 to 4.5 inches wind the coax round tightly twice as close to the plug as possible, cairfully remove the former and tape you balun together, so that the end with the plug starts and the remaining coax is directly below. Refit the plug to the antenna and check, if you still have high QRM do one extra turn, no more than 3 or you start to make a choke which will reduce your signal by .5 DB by every turn. If that doesn't work then invest in better shielded coax, such as aircell 7 or for less money but in my opinion a better coax ultra flex 7.

Good luck. 73s Dave

[mof000]

Don't waste your cash or time getting a QRM eliminator, all it does is act like a pre-amp but in reverse, so not only will it cut down QRM but also readable signal. You have not said what band you are on or what coax you are using?? Have you fitted a balun?? If not very easy to fit and make your own, once done it should cut down the unwanted noise dramatically. I am assuming you are on 11 meters, un-screw the coax from the antenna and using a coke bottle, tin of beans or any circular object with the diameter of 4 to 4.5 inches wind the coax round tightly twice as close to the plug as possible, cairfully remove the former and tape you balun together, so that the end with the plug starts and the remaining coax is directly below. Refit the plug to the antenna and check, if you still have high QRM do one extra turn, no more than 3 or you start to make a choke which will reduce your signal by .5 DB by every turn. If that doesn't work then invest in better shielded coax, such as aircell 7 or for less money but in my opinion a better coax ultra flex 7.

Good luck. 73s Dave

My brother bought the Timewave ANC 4 to help with PLT. It certainly got rid of the noise AND every other wanted signal!
I have read reports that they (ANC) are good for plasma interference.

[wa10]

A look at any reputable source of info pertaining to winding chokes or using ferite on coax cable will confirm that chokes DO NOT
cause loss,
lower your power
filter harmonics
attenuate your signal by .5db per turn,
act like a low pass filter

chokes don't do any of that, they don't effect signals inside the coax at all,

where do people get their made up science from.