Re: KC3EF Mobile Equipmemt

Jerry N9AVY


Funny you should mention smoke detectors. Worked with smoke detectors for 40+ years and they can be quirky.  Most of the home units are ionization type (little radioactive sticker is indicative). They are cheap to produce, hence the mass use.  Problem is they are high impedance and very susceptible to RFI... like Hi-Z microphones. Verified that with an Engineer friend back then.  

The solution has always been to replace ionization smoke detectors with photo electric ones which have low impedance front ends.    Have solved a lot of RFI problems for hams that way.
Photoelectric detectors are a bit more expensive, but it's worth it.

Jerry  n9avy

On Thursday, April 22, 2021, 07:40:31 PM CDT, Rick - N7WE <n7we1980@...> wrote:

When doing the initial shakedown on my /P setup for the car (hamsticks on mag mount, center of the CRV roof) I tuned the hamsticks with a MFJ 259B.  But when I put 25W into it from the rig, I had enought RFI inside the car to cause the computer to go all wonky and the SWR up substantially.  Bought a Balun Designs Model 1110 - QRP 1:1 Isolation/Choke Balun 1-54 MHZ, SO-239 connectors in and out.  It was about $50 as I recall.  It is rated to 300W SSB even though it says QRP.  So it is easily good for 75W continous modes.  Put it in the coax about 12" from the base of the Mag Mount and RFI disappeared.  SWR also went back to the tuned level.  My conclusion...I had massive common mode on the coax without the isolation.  These are great little chokes for PSKers.  I used another on the EagleOne off the back of the motor home as motor homes have lots of circuits (like furnace blowers, smoke alarms, vent fans, etc.) that just love to suck up RFI and do strange things.  I'm told, but haven't verified, that common mode on the coax can mess with your radiation pattern too. Of course, YMMV but that was my experience.
Rick - N7WE
070 - #1602

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