[RFI] RFI to and from adjacent cell site

Hare, Ed W1RFI w1rfi at arrl.org
Thu Sep 8 06:44:14 PDT 2011

"Birdies" that are sometimes reported on HF from these things are not a function of the cellular-telephone transmitter. They would be a function of the digital control circuitry and/or computers that are associated with the installation, or with the switch-mode power supplies that are associated with nearly everything nowadays. 
Such spurii would not be atypical, especially considering that the cell tower would almost certainly be considered by FCC to be a commercial environment, so it is likely that Class A devices could be used.
It may be possible to control much of the noise, typically with common-mode chokes, although in some cases, if it is possible for a ham to simply tell them to remove the installation when the contract is up, or if the contract requires "no RFI," chokes may be more trouble to install than they are worth.
Ed Hare, W1RFI
ARRL Laboratory Manager
225 Main St
Newington, CT 06111
Tel: 860-594-0318
Email: W1RFI at arrl.org


From: Tim Duffy K3LR [mailto:k3lr at k3lr.com]
Sent: Fri 9/2/2011 9:57 PM
To: 'Patrick'; rfi at contesting.com
Subject: Re: [RFI] RFI to and from adjacent cell site

Hi Pat:

I have built cell sites for more than 25 years. I have also operated on the
160 meters through 2 meters on these same cell site towers (so this would be
a worst case scenario). I have good experience in this area.

Using 1500 watts output on these bands - Amateur radio never caused a
problem "to" the cell site equipment (which used 800 and 1900 MHz
equipment). There were no noise issues noted that affected my ability to
receive on 160 through 2 meters.

W3YQ had a 200 ft cellular tower on his property and never had a problem.

When you work KL7WV on the air now (from Alaska - his operations occur at a
cell site) - no problem either way.

All that being said - cell site equipment and technology changes constantly
- so what is OK today - might not be tomorrow. And the frequencies above 2
meters - might cause a problem - or be affected - I don't have any data
above 148 MHz.

Tim K3LR

-----Original Message-----
From: rfi-bounces at contesting.com [mailto:rfi-bounces at contesting.com] On
Behalf Of Patrick
Sent: Friday, September 02, 2011 6:42 PM
To: rfi at contesting.com
Subject: [RFI] RFI to and from adjacent cell site


Someday in the next few years I hope to relocate to a house with greater
acerage where I may pursue ham radio without neightbors being too
close.  I had in mind 3 or more arces so that I might run legal limit on
the HF bands without bothering too many of my neighbors.

I was earlier today looking at a property for sale (just browsing
realtor sites online) that pretty much meets all of our requirements.
When looking at a satellite view of the house and land I found a cell
tower probably not over 200 feet away from the house.

This close to a cell site might be a real problem (or not).  I can
imagine that switching supplies and computers may cover the HF bands
with switching hash.  I can also imagine that a KW on 75 meters might
also make it's way into the cell system equipment giving the cellular
operator a fit. Regardless of who is technically right or wrong, I don't
need to buy into aggravation.

Does anyone have any personal experience with living adjacent to a cell
sight with HF gear?

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