[RFI] Splatter from AM Radio Station WNTS Indianapolis

[Hare, Ed, W1RFI]

The  majority of RFI cases ARRL receives about AM-broadcast intermod and even harmonics are at least made worse due to receiver overload.  It is important to try 10 or 20 dB of attenuation for the receive antenna, to see if the intermod or harmonics drop by much more than 20 dB.  A high-pass filter often fixed broadcast harmonics or intermod, indicating that the problem is caused by receiver non-linearities.

Ed


-----Original Message-----
From: RFI <rfi-bounces+ehare=arrl.org at contesting.com> On Behalf Of D C _Mac_ Macdonald
Sent: Wednesday, October 27, 2021 4:02 PM
To: jim at audiosystemsgroup.com
Cc: rfi at contesting.com
Subject: Re: [RFI] Splatter from AM Radio Station WNTS Indianapolis

Possible that the intermod was being created in your receiver front end!

73 de Mac, K2GKK/5 in OKC, OK

Sent from my iPhone

On Oct 27, 2021, at 14:12, Jim Brown <jim at audiosystemsgroup.com> wrote:

On 10/27/2021 6:29 AM, Gary Peterson wrote:
> Every AM broadcast station is required to perform annual measurements, searching for these types of problems.  I contract to perform spectral measurements for most of the AM stations within a 100 mile radius of my home.  I have the necessary equipment and travel to within approximately 1 kilometer of each transmitter site.  I measure each station’s occupied bandwidth, measure harmonics, up through and including the 6th and search for spurious signals, below, in and above the broadcast band.

Yes. But do those spectral measurements also include intermod products? I started out in ham radio in jr high school with two 5kW non-DAs within a mile of each other and about 1.5 miles from me, on 930 and 1470 kHz producing a strong product at 3870 kHz. There may have been others products, but that one gave me a lot of grief.

73, Jim K9YC


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