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Author Topic: 612 kHz  (Read 891 times)

renluop

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612 kHz
« on: February 05, 2018, 06:44:57 PM »

I might want to use my little AM Radio to check for a source of noise. This might seem a daft question, but is the radio held upright or horizontal; should the extendable aerial, or the internal?
Assume the noise were from a northerly point, what would the lie of the radio be?

I'm asking as some posts seen around are not clear to my aging brain.
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Black Sheep

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Re: 612 kHz
« Reply #1 on: February 05, 2018, 07:09:56 PM »

I use the official 444B Tester ..... which is little more than a glorified radio ...... but after doing this for quite a while now, I've found that (for example), if there is a telegraph pole with umpteen drop-wires shooting off in all directions, then walking underneath them one at a time with the antennae pointing towards the wires, you can sometimes (50/50) determine the offending wire and obviously the premises it's attached to ??

Wheteher this would work with a portable radio I couldn't say for certain, but I can't see a reason why it wouldn't ??

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roseway

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Re: 612 kHz
« Reply #2 on: February 05, 2018, 07:14:12 PM »

Presuming that it's got an internal ferrite rod aerial, then use that. Keep the radio horizontal, and rotate it for the strongest signal. Imagine a line drawn at right angles to the ferrite rod - the strongest signal will be on that line, either side of the rod. Now move to a different position and repeat. The source of the noise will be where the two imaginary lines intersect.

That's a considerable over-simplification of course, but I guess you get the idea.
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  Eric

benji09

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Re: 612 kHz
« Reply #3 on: February 05, 2018, 10:19:19 PM »



    For direction finding, turning the rod to 90 degrees from the maximum will give a sharp null, with the ferrite  rod pointing to, and from, the noise source. This  gives a more accurate direction finding ability.  Obviously both max and min modes of direction of the rod should be used in turn.............   

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sevenlayermuddle

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Re: 612 kHz
« Reply #4 on: February 05, 2018, 11:23:34 PM »

Bear in mind too, not only might signals at 612kHz cause interference, so might signals at other frequencies.

My own technique is to wander around whilst fiddling with the tuning dial.   I’m aware that BT OR use it as a kind of reference but to my knowledge, there is nothing that special about 612 kHZ.   If you detect interference at some other frequency, that matters too.

Per direction, ignore the extended antenna on most domestic receivers, as that is only used for VHF/FM reception.   For AM (MW/LW), the radio usually relies on an internal ferrite rod.   Being a ‘rod’, and being optimal when horizontal, the designer will maximise space efficiency by positioning it lenghtwise, side to side, within the receiver.   That being the case, for maximum pickup,  the radio will ‘face’ towards or away from the source.
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4candles

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Re: 612 kHz
« Reply #5 on: February 05, 2018, 11:26:18 PM »

Agreed with everything thus far, especially the point about nulls tending to be sharper.
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Most things are somewhere else

tickmike

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Re: 612 kHz
« Reply #6 on: February 06, 2018, 11:15:19 AM »

should the extendable aerial, or the internal?
 
internal only.
Quote
Assume the noise were from a northerly point, what would the lie of the radio be?
East to West.

@sevenlayermuddle
Quote
there is nothing that special about 612 kHZ
Only that it is a quite part of the spectrum around that frequency.

[Moderator edited to fix the broken [quote][/quote] tags.]
« Last Edit: February 06, 2018, 05:44:24 PM by burakkucat »
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renluop

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Re: 612 kHz
« Reply #7 on: February 06, 2018, 11:58:32 AM »

Thanks, guys! I think I may be on to the source of my troubles, as referred to in my larger thread.
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anything