[Elecraft] Antennas in the attic

Tue Aug 13 15:27:27 EDT 2013

I've had two meter and UHF antennas in the attic without issues.  I also 
have two perpendicular 40M and two perpendicular 20M dipoles in the attic of 
my house.  Up to a year ago, all was fine with my K3 running 100W, either 
band.  Now, if I transmit as low as 20W on one of the 40M dipoles, it 
instantly sets off the fire/smoke detectors in my home security system. 
These fire/smoke detectors are probably 15 or more years old, the whole 
security system is wired.  Most of the wiring IS in the attic, so no big 
surprise.  The 40M dipoles do get our really well, even in the attic.

Since the fire/smoke detectors are being triggered, they set off the whole 
alarm, including calling the monitoring service, whether the alarm system is 
set (enabled) or not.  The SWR on the primary offending 40M dipole has a 
very low SWR, less than 1.2:1 at 7.23MHz.

I'm now researching chokes and bypass caps, and maybe rewiring the smoke 
detectors with shielded cables.  The security system hasn't a clue....

So, getting out is not the only issue....
73, Terry, WB4JFI

-----Original Message----- 
From: Mike WA8BXN
Sent: Tuesday, August 13, 2013 2:57 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Antennas in the attic

Remember things are different on VHF/UHF bands. Its often FM which reduces
noise problems to some extent, and the wavelengths are shorter and get out
between conductors a lot better than HF.

73 - Mike WA8BXN

-------Original Message------- 

From: Phil Kane

Date: 8/13/2013 2:40:41 PM

To: elecraft at mailman.qth.net

Subject: Re: [Elecraft] Antennas in the attic

On 8/13/2013 9:56 AM, Edward R Cole wrote:

> So this suggests that VHF and UHF ham antennas can also work in attics.

For several years I used a 2-m mag-mount antenna upside-down on the

ductwork in the plenum area above my office - 3rd floor of a 6-story

building. Had no problem reaching repeaters 30+ miles away. "Radio is

magic" <G>

73 de K2ASP - Phil Kane

Elecraft K2/100 s/n 5402

>From a Clearing in the Silicon Forest

Beaverton (Washington County) Oregon
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