[TenTec] Power Line QRN?
Wed, 28 Apr 1999 09:31:36 EDT
The technique you describe below has been around awhile, and you could build
it yourself for a lot less than $190. It is covered in my 1941 Radio
Handbook, and I'm sure it is covered in others. It consists [if i remember
correctly] of a "voltage probe" type of antenna [small whip] that is tuned
out of phase with the main antenna, and the signals are combined. The
drawback with this technique is that it needs to be readjusted for every band
change, and should only be in line during receive.
If you want more details than the scant few I can provide here, I will check
my old handbook tonite at home.
73, Jim NĜOCT
In a message dated 27-Apr-99 23:59:30 Central Daylight Time, firstname.lastname@example.org
> I've also heard from two sources that another treatment may be effective.
> That is a technique for receiving the QRN with a device that is essentially
> an out of band receiver which nonetheless receives essentially the same
> power line QRN which is then inverted and with careful phase adjustment,
> used to cancel the QRN as a common mode rejection. I have found what
> to be one such device from JPS Communications, their ANC-4 for around $190.
> (MFJ has something that looks very similar (MFJ1025 or MFJ1026), but I
> it actually uses a different technique, that of nulling signals from a
> direction. That wouldn't be very useful in my case since the power lines
> along a broad line to the east of me where much of my listening would be
> directed.) I understand from an old Motorola commercial communications
> systems engineer that they once used that technique, but one flaw in the
> theory it had was that in a crowded metropolitan area you could have
> locating the necessary alternate frequency band that was devoid of traffic.
> Any signal other than the QRN in the alternate receiver would not cancel
> properly with the QRN signal in the primary band and would therefore become
> an inverted spurious QRM in the primary band.
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