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[RFI] Broadcast interference potential (for N3JT)

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Subject: [RFI] Broadcast interference potential (for N3JT)
From: Pete Smith <n4zr@contesting.com> (Pete Smith)
Date: Sun, 23 Jan 2000 02:14:21 +0000
I have fixed the message as Tim suggested.  This is not from me but from
n3jt (jtalens@digizen.net).  Please respond either to the reflector or to him.

73, Pete N4ZR

Begin relayed message:

Folks -  I have been looking at a particular house in McLean, 
Viriginia, somewhat on a hill and in all respects quite acceptable, 
including for ham radio.  However, to the south, about .25 mile away, 
are 3 185 foot broadcast towers.  The proposed house is orthogonal to 
the axis of the towers.  The towers are for two A.M. broadcast 
stations, one at 1390 kHz and other at 1120 kHz. 

I took a 706 and small whip antenna to the house site and listened 
across all the ham bands, 160-10 m.  I didn't hear any birdies, 
intermod, or unusual noise except at 3630 kHz and 1800 kHz.  My 
current house, about 3 miles from the same station but much closer to 
the main lobe, feature similar signals, though somewhat weaker.  

My question is whether this proximity to the towers, and in view of 
this result, suggests a likely major problem that will lead to 
incurable problems for HF operation were I to erect a sizeable 
antenna system, meaning dipoles or loops for 160 and180 m, 
monobanders for 40-10m.  Note that the monitoring was conducted 
midday, when both a.m. stations were at maximum power.  However, the 
whip antenna does not capture a tremendous amount of rf, as would a 
sizeable ham antenna.  On the other hand, a ham antenna is itself a 
filter and might reject out-of-band rf energy.

Adding and subtracting 1390 and 1120, adding the difference, etc., 
produces no harmonics in the ham bands.  I'm not sure what other 
intermod products might do, such as those produced by a saturated ham 
receiver front end.  

Any advice on the risk of having a major problem?  If there is a 
problem, is it likely curable, e.g., by using a notch filter?


Jim, N3JT

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