RFI With KPA500 Full Output on 40m

[Jim Bennett]

Just when one thinks all is good in the world... I re-worked a Hustler 5BTV so that it covers 40-30-20-15-10 meters, rather than 80-40-20-15-10. The mod was simple - cutting off five inches from the top tube. No problem. It now has a 1.1:1 SWR across most of the bottom of 40 meters. Sweet. Kinda.

When I crank my KPA500 up to full output on 40 meters, I get RFI on my home security system. Lights up all the remote panel lights and beeps. Luckily it does NOT set off the alarm. If I back off output to 350 watts or so, no RFI problem. Both ends of my RG-8 coax have ferrite chokes. This problem ONLY happens on 40 meters; full power on any of the other bands causes no issues.

The vertical is mounted on the ground, 25 feet away from the house, with about 40 fairly short radials. The security system controller (an Ademco 4150, 21 years old) is in a metal case, and is located in a closet on the second floor of the house.

Anyone else have RFI problems with their security system? If so, how were you able to cure it? I was thinking that perhaps ferrite beads on every lead coming into the controller box may do it?

Tnx, Jim / W6JHB
Folsom CA

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[Vic Rosenthal]

One or more of the wires going to your system must be resonant on 40 meters and is picking
up RF directly from the antenna.

I had horrible problems when I had an inverted L with the horizontal part over the house.
My alarm is a 'wired' type that has terminating resistors at each of the switches. 1.5 kW
on 160 meters simply vaporized one of the resistors, and heated others at the alarm box. I
fixed it by winding each of the wires going to the switches around ferrite cores at the
alarm box. I also treated the phone line and the wires that go to the battery and the bell
box.

I used various cores, but the square Radio Shack things worked. No. 31 ferrite mix is
recommended.

That fixed it, but I replaced the inverted L with a T and got rid of a lot of RF floating
around.

Since all of your lights are lighting up, I would start with the phone line and the power
supply. Remember, at 40 meters you need to as many turns as you can get around the cores.
Just passing the wire through a bead won't do it.

On 3/17/2012 8:51 PM, Jim Bennett wrote:

> Just when one thinks all is good in the world... I re-worked a Hustler 5BTV so that it
> covers 40-30-20-15-10 meters, rather than 80-40-20-15-10. The mod was simple - cutting
> off five inches from the top tube. No problem. It now has a 1.1:1 SWR across most of
> the bottom of 40 meters. Sweet. Kinda.
>
> When I crank my KPA500 up to full output on 40 meters, I get RFI on my home security
> system. Lights up all the remote panel lights and beeps. Luckily it does NOT set off
> the alarm. If I back off output to 350 watts or so, no RFI problem. Both ends of my
> RG-8 coax have ferrite chokes. This problem ONLY happens on 40 meters; full power on
> any of the other bands causes no issues.
>
> The vertical is mounted on the ground, 25 feet away from the house, with about 40
> fairly short radials. The security system controller (an Ademco 4150, 21 years old) is
> in a metal case, and is located in a closet on the second floor of the house.
>
> Anyone else have RFI problems with their security system? If so, how were you able to
> cure it? I was thinking that perhaps ferrite beads on every lead coming into the
> controller box may do it?
>
> Tnx, Jim / W6JHB Folsom CA
>

--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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[Mike K2MK]

Hi Jim,

I think it may be a fact of life with alarm systems since they have wiring all over the house. On mine, high power would signal an alarm identified as a fire alarm. I identified the wires in the alarm panel that went to the smoke detector input screw terminals and added a clamp-on ferrite core. Problem solved.

In your case you should identify the cables (probably 4 or 5 conductor) coming from the alarm keypads and clamp on a core on each one.

Anybody with an amplifier should probably have a supply of clamp on ferrite cores. Odd things start to happen as you approach legal limit. My heated matress pad would start blinking also on 40 meters. I had to use a larger diameter split core and wrap the AC power cord for the matress pad controller through it several times to solve that one.

73,
Mike K2MK

Jim Bennett wrote

Just when one thinks all is good in the world... I re-worked a Hustler 5BTV so that it covers 40-30-20-15-10 meters, rather than 80-40-20-15-10. The mod was simple - cutting off five inches from the top tube. No problem. It now has a 1.1:1 SWR across most of the bottom of 40 meters. Sweet. Kinda.

When I crank my KPA500 up to full output on 40 meters, I get RFI on my home security system. Lights up all the remote panel lights and beeps. Luckily it does NOT set off the alarm. If I back off output to 350 watts or so, no RFI problem. Both ends of my RG-8 coax have ferrite chokes. This problem ONLY happens on 40 meters; full power on any of the other bands causes no issues.

The vertical is mounted on the ground, 25 feet away from the house, with about 40 fairly short radials. The security system controller (an Ademco 4150, 21 years old) is in a metal case, and is located in a closet on the second floor of the house.

Anyone else have RFI problems with their security system? If so, how were you able to cure it? I was thinking that perhaps ferrite beads on every lead coming into the controller box may do it?

Tnx, Jim / W6JHB
Folsom CA

[Jim Sheldon]

For some reason, probably resonant length of coax or something, plus the 40 meter dipole runs directly over the house and parallel to the incoming power service, Every time I key a rig with more than about 50 watts, I trip every GFI outlet in the house.  I haven't found enough big snap-on ferrites to hit all the romex coming out of the panel, but when I do, I'll certainly put 'em on.  A really big one that would snap around the incoming line at the panel would be nice, but so far I haven't found a source of snap on's that I can afford.  Not sure either on what material would be best for that.

Jim - W0EB

>> When I crank my KPA500 up to full output on 40 meters, I get RFI
>> on my
>> home security system. Lights up all the remote panel lights and
>> beeps.
>> Luckily it does NOT set off the alarm. If I back off output to
>> 350 watts
>> or so, no RFI problem. Both ends of my RG-8 coax have ferrite
>> chokes. This

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[Mike Cox]

I had similar issues over the years with my GFI receptacles. I put
ferrites on the power leads both at the receptacles and in the main
distribution panel but was only able to reduce the problem and/or move
it to other bands. I then tried different brands of receptacles and,
after trying everything from Lowe's and Menard's, finally found that the
Leviton brand GFI receptacles (I found them at Home Depot) completely
eliminated my problems.

Mike - AB9V

On 3/18/2012 10:05 AM, Jim Sheldon wrote:

> For some reason, probably resonant length of coax or something, plus the 40 meter dipole runs directly over the house and parallel to the incoming power service, Every time I key a rig with more than about 50 watts, I trip every GFI outlet in the house.  I haven't found enough big snap-on ferrites to hit all the romex coming out of the panel, but when I do, I'll certainly put 'em on.  A really big one that would snap around the incoming line at the panel would be nice, but so far I haven't found a source of snap on's that I can afford.  Not sure either on what material would be best for that.
>
> Jim - W0EB
>
>>> When I crank my KPA500 up to full output on 40 meters, I get RFI
>>> on my
>>> home security system. Lights up all the remote panel lights and
>>> beeps.
>>> Luckily it does NOT set off the alarm. If I back off output to
>>> 350 watts
>>> or so, no RFI problem. Both ends of my RG-8 coax have ferrite
>>> chokes. This
> ______________________________________________________________
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[Jim Brown-10]

On 3/18/2012 12:08 AM, Vic K2VCO wrote:
> I would start with the phone line and the power
> supply. Remember, at 40 meters you need to as many turns as you can get around the cores.
> Just passing the wire through a bead won't do it.

Security systems are notoriously awful for RFI.  Vic has given you good
advice, but I would also consider RF bypass caps on any cables going to
external sensors (if there are any) that are simply carrying dry switch
contacts. Even better, if you can, replace any parallel wire cables with
twisted pair.  0.01uF or 0.0047 uF would be good values to use.

73, Jim K9YC
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[Jim Brown-10]

On 3/18/2012 7:05 AM, Jim Sheldon wrote:
> I trip every GFI outlet in the house.  I haven't found enough big snap-on ferrites to hit all the romex coming out of the panel, but when I do, I'll certainly put 'em on.  A really big one that would snap around the incoming line at the panel would be nice, but so far I haven't found a source of snap on's that I can afford.  Not sure either on what material would be best for that.

As was noted in another post, the ones that trip are defective (poor
design). The solution is to replace them with GOOD ones.

As K2VCO noted, ferrite beads clamped onto a wire are next to USELESS
for HF RFI.  Ferrite chokes work by adding a parallel resonance in
series with the wire that they surround, and a single bead or clamp-on
is resonant around 150 MHz. To make it useful at HF we must move the
resonance down to the HF bands by winding multiple turns through it.

Study http://audiosystemsgroup.com/RFI-Ham.pdf  for a detailed
explanation and lots of detailed advice.

73, Jim Brown K9YC
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[Jim Bennett]

Problem solved!

I tried a little aluminum shielding on the control box (the plastic one that supports their wireless sensors), and that was a waste of time. I gave it a shot while waiting for my delivery of ferrite cores from Mouser. Didn't cost anything and was worth a try.

The security system RFI was cured by inserting, at the vertical's feed point, a choke made from a stack of five ferrite cores (Fair-Rite part number 263180033802) with seven turns of RG-8X passing through the stack. I cranked the KPA500 up to 550 watts and not a sound was heard from that alarm system. Cool.

A side benefit to this was that I have a lower SWR at my desired "sweet spots" on 40 - 10 meters. So, placing the string of five ferrite beads on the coax (per a manufacturer's "RFI Kit"), simply wasn't getting the job done. The five mix 31 cores from Fair-Rite (actually from Mouser) did the trick.

Thanks for everyone's suggestions! And especially thanks for the good information on K9YC's web pages.

73, Jim / W6JHB


On   Sunday, Mar 18, 2012, at  Sunday, 8:51 AM, Jim Brown wrote:

> On 3/18/2012 7:05 AM, Jim Sheldon wrote:
>> I trip every GFI outlet in the house.  I haven't found enough big snap-on ferrites to hit all the romex coming out of the panel, but when I do, I'll certainly put 'em on.  A really big one that would snap around the incoming line at the panel would be nice, but so far I haven't found a source of snap on's that I can afford.  Not sure either on what material would be best for that.
>
> As was noted in another post, the ones that trip are defective (poor
> design). The solution is to replace them with GOOD ones.
>
> As K2VCO noted, ferrite beads clamped onto a wire are next to USELESS
> for HF RFI.  Ferrite chokes work by adding a parallel resonance in
> series with the wire that they surround, and a single bead or clamp-on
> is resonant around 150 MHz. To make it useful at HF we must move the
> resonance down to the HF bands by winding multiple turns through it.
>
> Study http://audiosystemsgroup.com/RFI-Ham.pdf  for a detailed
> explanation and lots of detailed advice.
>
> 73, Jim Brown K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Please help support this email list: http://www.qsl.net/donate.html

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