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Spark gap xmtr!

S

SamBuca

Guest
Seems my new house came with a spark gap transmitter in the basement.

I'm fiddling around with some AM equipment and all of a sudden I hear this loud buzz for a second or two. An hour later I hear it again. Later on that night my computer speakers (VERY noisy/sensitive amp in them) buzz like crazy for a second or two.

Well, holy crap...the freaking natural gas furnace has a spark device that goes off when it turns on. Pollutes the air waves AND feeds back into the electrical system. That must be one hell of an ignition unit.

What kind of filtering should I put on the electrical line?<P ID="signature">______________
</P>
 
> Seems my new house came with a spark gap transmitter in the
> basement.
>
> I'm fiddling around with some AM equipment and all of a
> sudden I hear this loud buzz for a second or two. An hour
> later I hear it again. Later on that night my computer
> speakers (VERY noisy/sensitive amp in them) buzz like crazy
> for a second or two.
>
> Well, holy crap...the freaking natural gas furnace has a
> spark device that goes off when it turns on. Pollutes the
> air waves AND feeds back into the electrical system. That
> must be one hell of an ignition unit.
>
> What kind of filtering should I put on the electrical line?
>
Welcome to the world of homeownership, Buca. Check your thermostat, there is a spark that generates in the older "knob" thermo's. (Turn the knob while in a dark room, you'll see what i mean) If you get one of the newer digital programmable thermo's, this might fix your problem.<P ID="signature">______________

njrm.org - The New Jersey Radio Museum
</P>
 
The older thermostats often use a mercury switch, which usually doesn't arc enough to be a problem. Besides, even the oldest thermostats usually are switching low voltage control circuits.

It's the igniter, used instead of a pilot. Oil furnaces are notorious for this.

Try putting in an mov on the breaker that controls this circuit. Has worked for similar devices such as as copiers that cycle heaters on and off.
 
> It's the igniter, used instead of a pilot. Oil furnaces are
> notorious for this.

Yeah...it's the igniter. I have a sexy new digital thermostat with time settings. Furnace is fairly new though..I'd say 5 years or so.

> Try putting in an mov on the breaker that controls this
> circuit. Has worked for similar devices such as as copiers
> that cycle heaters on and off.

Home Depot have those or should I hit up mouser?

Gotta love natural gas. CH<sub>4</sub> + 2O<sub>2</sub> + igniter -> 2H<sub>2</sub>O + CO<sub>2</sub> + RF + transients :)<P ID="signature">______________
</P>
 
Spark gap xmtr! (1970 style!)

Speaking of "spark gap transmitters", I recall in 1970 (at the age of 10 in Randolph, MA), I just had started doing the Citizens Band hobby (WELL BEFORE the "good buddy" crap of the late 1970's). We actually had licenses (KDO-9550, later KACG-1233). Every morning around 6:45 AM, without fail, a neighbor down the street would start his car. Mind you this was not your average neighbor, he was a race car driver (from the old Norwood (MA) Arena days). Needless to say, his car was really "zooped up" for performance and in RF emissions it was VERY powerful! This neighbor lived over a half-a-mile away! Channels 1-23 (at that time, there were only 23 "legal" channels on the 11 meter band) were nothing but spark-gap transmissions for nearly 15 minutes. When he drove away at 7:00 AM, I would still receive his RFI for nearly 2 minutes. I would say that his "Class A/B" coverage was probably about 1 to 1.5 miles away. I'm sure it saturated the entire HF spectrum everywhere he drove. That thing must have had about 20,000 watts of power!

73,

Pete


> Seems my new house came with a spark gap transmitter in the
> basement.
>
> I'm fiddling around with some AM equipment and all of a
> sudden I hear this loud buzz for a second or two. An hour
> later I hear it again. Later on that night my computer
> speakers (VERY noisy/sensitive amp in them) buzz like crazy
> for a second or two.
>
> Well, holy crap...the freaking natural gas furnace has a
> spark device that goes off when it turns on. Pollutes the
> air waves AND feeds back into the electrical system. That
> must be one hell of an ignition unit.
>
> What kind of filtering should I put on the electrical line?
> <P ID="signature">______________
Peter Q. George (K1XRB)
Whitman, Massachusetts</P>
 
Re: Spark gap xmtr! (1970 style!)

> .....Needless to say,
> his car was really "zooped up" for performance and in RF
> emissions it was VERY powerful! This neighbor lived over a
> half-a-mile away! Channels 1-23 (at that time, there were
> only 23 "legal" channels on the 11 meter band) were nothing
> but spark-gap transmissions for nearly 15 minutes. When he
> drove away at 7:00 AM, I would still receive his RFI for
> nearly 2 minutes. I would say that his "Class A/B" coverage
> was probably about 1 to 1.5 miles away. I'm sure it
> saturated the entire HF spectrum everywhere he drove. That
> thing must have had about 20,000 watts of power!

Radio Shack used to sell an electronic ignition kit for about
20-bucks. Took about an hour to assemble and it could raise the
dead in terms of hard-starting cars! Damn thing delivered around
35,000 Volts of raw energy; would set off sparklies in even cable-
connected TV's for about a half mile and forget about AM reception
for several blocks.

People who used them on cars like MGs and Volvos with Bosch distributor
caps learned to carry spare caps. These little finned boxes could burn
out the spring-loaded center (carbon) conductor in those caps in about
3,000 miles use! When they failed and you didn't have a spare you
sometimes could rip the spring out of a retractible ball point pen and
stick it in the cap to make it home. But then you had to change the
rotor, too, 'cause it would have a neat little hole burned into it where
the spring made contact!<P ID="signature">______________
When you're done impeaching the prez, keep on going; recall every member of congress and lock 'em up! Let's try NO govt. for a while.</P>
 
your local electrical supply house..get the kind that go into the panel box & stick the hot lead on the same breaker as the furnace lead. If that don't work, you haven't wasted anything as that protects the house against lightning strikes.
You can also get the little MOV's that look like ceramic caps (rated at 150 v of course,) and stick them right across the contactor for the igniter. These you can probably find through Mouser.
 
> It's the igniter, used instead of a pilot. Oil furnaces are
> notorious for this.

My new gas furnace doesn't have anything that resembles a spark igniter. Instead, it has some kind of electric heating element that glows orange for about 10 seconds before it fires up the burners. No RFI. However, the 240V electric water pump in my well makes nasty crackling on AM/shortwave for about 5 seconds whenever it kicks on. <P ID="signature">______________
It's a common mistake to not use punctuation in its proper form.
<a target="_blank" href=http://www.cgl.uwaterloo.ca/~csk/its.html>Be kind to your friend, the apostrophe.</a></P>
 
I think the MOV's will only take out voltage spikes, not RFI. You may want to look at some of the surplus electronic joints for an AC RFI filter. Make sure and get whatever is appropriate voltage wise. I think mouser also sells such things new as well, just not sure who makes them. Our local surplus place sells 'em for a few bucks. The contain an inductor & cap combo to get rid of the racket, and they filter the hot & neutral sides. A 3 legged one may be needed for a 240 circuit, so ya get both hots & the neutral.

Another thought would be to contact Amidon and tell them the trouble, and they can sell you some appropriate ferrite beads to place on the wires to choke out the racket. The mix that is used in the ferrite is critical in maximizing rejection on the band/s of interest..

A buddy had some RFI at his place from the microprocessor in a damn water conditioner. We never did get rid of that noise, although we at least made a dent in it.

Let us know how ya do in the battle..

dave/fmnostatic


> your local electrical supply house..get the kind that go
> into the panel box & stick the hot lead on the same breaker
> as the furnace lead. If that don't work, you haven't wasted
> anything as that protects the house against lightning
> strikes.
> You can also get the little MOV's that look like ceramic
> caps (rated at 150 v of course,) and stick them right across
> the contactor for the igniter. These you can probably find
> through Mouser.
>
 
> > It's the igniter, used instead of a pilot. Oil furnaces
> are
> > notorious for this.
>
> Yeah...it's the igniter. I have a sexy new digital
> thermostat with time settings. Furnace is fairly new
> though..I'd say 5 years or so.
>
> > Try putting in an mov on the breaker that controls this
> > circuit. Has worked for similar devices such as as copiers
>
> > that cycle heaters on and off.
>
> Home Depot have those or should I hit up mouser?
>
> Gotta love natural gas. CH4 + 2O2 + igniter -> 2H2O + CO2 +
> RF + transients :)

Aint due to the NG.....LP, Propane or that "bastard" gas (according to Hank Hill) Butane would also be the same...quiet...its the ignitor...(hmmmm ignition noise? hehehehe)..personally I would never build a house without Nat Gas..period

Personally I would put some 0.01 or similar caps @ 250V or more across the power leads to the system...and maybe some to earth gnd....wouldnt hurt...A MOV wont fire unless the voltage spikes...and thus wont get rid of AC induced RF noise...a filter (LC or RC) is the answer.

73
 
> Personally I would put some 0.01 or similar caps @ 250V or
> more across the power leads to the system...and maybe some
> to earth gnd....wouldnt hurt...A MOV wont fire unless the
> voltage spikes...and thus wont get rid of AC induced RF
> noise...a filter (LC or RC) is the answer.
>
> 73
>
Good point--but that gets complicated. We used a couple of ceramic stand-offs, .01 250 volt ceramics and coils made of #12 (all built into a metal handy box) to build a network feeding ac into the equipment rack at the AM we once owned. Worked well, but would have given an electrical inspector a heart attack.
 
> Personally I would put some 0.01 or similar caps @ 250V or
> more across the power leads to the system...and maybe some
> to earth gnd....wouldnt hurt...A MOV wont fire unless the
> voltage spikes...and thus wont get rid of AC induced RF
> noise...a filter (LC or RC) is the answer.

Wouldn't I need to figure out the load and then stack a bandpass filter on it?

Or is this as simple as a little .01uf 250v guy between hot and neutral?<P ID="signature">______________
</P>
 
Voltage more important than load. That's why you want something rated at 250 volts. Just stick it between hot and neutral as close to the igniter circuit as you can get.

If you try to build a network to calm things down, then you have to consider the current running though the network. Our device was built using coils made of #12 wire on ceramic stand-offs (insulators) that we got surplus somewhere. Not much load--processor, remote control, STL receiver. Kind of a "T" as I remember:

AC in>.-coil-.-coil->load
|
cap
|
neutral------------------

Would take a fair size coil to eliminate low freq. RF, our device was more for lightning suprression. Some commercial RF filters use similar approach, and are designed for mounting inside small devices. Look at the Kobiconn line of filters at Mouser, they have some that have lugs in and out and have some in the 1 to 3 amp range (and up). Don't look to be too expensive, under $10 for 3 amps. Do a search on their site for "Kobiconn EMI/RFI Power Line Filters"
 
Your MOV will explode if you put it on a gas furnace igniter. I had one that shot out over 1KV to start the spark, and MOVs would be toast directly on the HV igniter lead. You need an off the shelf supressor for the furnace power alone, then pester Honeywell about the igniter noise.


> I think the MOV's will only take out voltage spikes, not
> RFI. You may want to look at some of the surplus electronic
> joints for an AC RFI filter.
 
Re: Spark gap xmtr! (1970 style!)

> Damn thing delivered around 35,000 Volts of raw energy;
> would set off sparklies in even cable-connected TV's
> for about a half mile and forget about AM reception
> for several blocks.

It reminds me of a house I lived in as a kid. We had an electric "doorbell/buzzer" which was some kind of solenoid/spark-gap device wired to 120v AC. It literally shook the floor-joist it was attached to in the basement.

I'm not sure how far it interfered with AM, but my friend Brian couldn't hear anything on the entire band about 3.5 miles away.
 
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