Ferrite....

[144inBama]

We all know to use ferrite on power wires for noise suppression, but what type? Most use mix 43 which is good in the 25-300 MHz range for RFI/EMI common mode suppression. Mix 31 is good for the 1-300 MHz range and mix 73 is good < 50 MHz range, then 52 & 61 are good for the 200 - 1000 MHz range, followed by mix 75 at 150 KHz – 10 MHz. If we are trying to filter out simple RF, mix 43 would be ideal, but what about other engine noises? A car alternator runs around 400 Hz so mix 75 would be more suited, can you run multiple mixes to cover a broader range?
Also, can you use mixes 52, 61, & 75 on your coax since it doesn't filter the operational range you are transmitting in? Say if you wanted to filter out higher and lower freqs that are causing interference, would using that ferrite cause any issues?
Just some late night thinking....

 

[Handy Andy]

Just some late night thinking...

???
​

Oh - you said Ferrites - not Ferrets...

The alternator itself is a problem for many reasons, one mostly being the FREQUENCY of the output varies with engine RPM so it covers a wide range or band of frequencies itself.

So when you're faced with that - it could be more of a common ground loop problem - being older wiring the choke effect the ferrite would have on noise diminishes as the frequency goes lower - so the effectiveness is not the best even when trying to choke alternator output.

Remember too, the AMPERAGE varies in RPM as well as the RPM to Frequency.

A strong clue is to remember the more saturated the choke, the HOTTER it will get from the effects of voltage to current and current to voltage transformation within it.

Now the reason this comes up is from a repair we did to a truck that ran an amp but took the DC power output direct thru the firewall and they decided to use a choke at the engine side of the firewall - well that works to a point until the amp itself, due to the draw - starts to heat up the choke from that draw.

Can melt the insulation off the winds and start a small fire.

So really you should look into "bonding" as the best defense to reduce a ripple effect from the engine to body ground bonding. Chassis to Frame noises tend to collect around the main tie off points in older aged wiring so the less corrosion the less resistance improves the noise figure better than to try and see if Ferrite is the only solution - because it isn't going fix the resistive corroded path to ground that now looks like a high impedance path for noise to show up.

But then if you've already done that - Ferreting out the noise using Ferrite chokes is a specific solution but not the cure all for a condition known to exist in any vehicle.

 

[sp5it]

If you have noise from alternator it's time to repair it. Worked for me a few times.

 

[144inBama]

If you have noise from alternator it's time to repair it. Worked for me a few times.

I don't now, but I have in the past. I'm just thinking along the lines of noise in general. The old 80s and older trucks just had noise, from the factory they were just noisy. I was wondering more about the use of different mixes in combination on the coax itself for noise coming through the antenna and could it filter out transmitted harmonics?

 

[sp5it]

If it comes through antenna you have to cancel noise at it's source.
For alternator I recommend noise suppressing capacitor connected directly to alternator output screws. If it's already there, replace with new one, clean contacts.
Mike

 

[Handy Andy]

To help,

Usually the material used, and it's permeability "factor" or number - determines it's upper limits in frequency use.

High permeability - like 75 - might or might not contain magnesium versus Nickel - this affects heat production and as well as survivability in the environment it's in.

Nickel is the least reactive - but also has the LOWER Flux density - permeability - figure of merit. .

So magnesium for low to mid range <100,000Hz due it is permeability and flux density ratios are higher for those LOWER frequencies. (Heat factor is higher with these too)

Then switch to Nickel-based types for higher Frequency range - 1MHz and above - scenarios.

Now why I'm bringing this up this way - is so you can understand that on one level - RF issues work best with Nickel - based cores, other times - using DC values - the Magnesium - based ones do better.

So if you have power cord noise, use the Magnesium - based (Expensive but density is what you want).

While RF based, use Nickel -based types for their performance in low- flux density but high reaction times - again a $$$ to flexibility and packaging design consideration here - for RF getting in to the antenna. Those sources could also use the Magnesium types but limit their MUF (Max useable Frequency) to less than 1MHz effectively.

Nickel is interchangeable but the permeability factor is less as your got LOWER - means you get filter per $$$ at lower frequency ranges - still able, but not as effective.

 

[M0GVZ]

If we are trying to filter out simple RF, mix 43 would be ideal, but what about other engine noises? A car alternator runs around 400 Hz

But your receiver is at 27MHz so it won't hear 400Hz. It hears ignition noise because spark gap transmissions are extremely broad banded which is why spark gap transmitters like the Titanic used are banned worldwide.

 

[144inBama]

But your receiver is at 27MHz so it won't hear 400Hz.

I have no idea why that never clicked in my head....

To help,

Usually the material used, and it's permeability "factor" or number - determines it's upper limits in frequency use.

High permeability - like 75 - might or might not contain magnesium versus Nickel - this affects heat production and as well as survivability in the environment it's in.

Nickel is the least reactive - but also has the LOWER Flux density - permeability - figure of merit. .

So magnesium for low to mid range <100,000Hz due it is permeability and flux density ratios are higher for those LOWER frequencies. (Heat factor is higher with these too)

Then switch to Nickel-based types for higher Frequency range - 1MHz and above - scenarios.

Now why I'm bringing this up this way - is so you can understand that on one level - RF issues work best with Nickel - based cores, other times - using DC values - the Magnesium - based ones do better.

So if you have power cord noise, use the Magnesium - based (Expensive but density is what you want).

While RF based, use Nickel -based types for their performance in low- flux density but high reaction times - again a $$$ to flexibility and packaging design consideration here - for RF getting in to the antenna. Those sources could also use the Magnesium types but limit their MUF (Max useable Frequency) to less than 1MHz effectively.

Nickel is interchangeable but the permeability factor is less as your got LOWER - means you get filter per $$$ at lower frequency ranges - still able, but not as effective.

That is some great reading, thanks Andy.

 

[Captain Kilowatt]

But your receiver is at 27MHz so it won't hear 400Hz. It hears ignition noise because spark gap transmissions are extremely broad banded which is why spark gap transmitters like the Titanic used are banned worldwide.

Yes but you CAN hear 400 Hz over your 27 MHz receiver when the alternator produces a whine that comes in on the power leads and gets into the audio circuitry. Good grounds can help as can a good filter on the power leads.

 

[Handy Andy]

That is some great reading, thanks Andy.

Hope your days goes better than mine!

 

[Slowmover]

We all know to use ferrite on power wires for noise suppression, but what type? Most use mix 43 which is good in the 25-300 MHz range for RFI/EMI common mode suppression. Mix 31 is good for the 1-300 MHz range and mix 73 is good < 50 MHz range, then 52 & 61 are good for the 200 - 1000 MHz range, followed by mix 75 at 150 KHz – 10 MHz. If we are trying to filter out simple RF, mix 43 would be ideal, but what about other engine noises? A car alternator runs around 400 Hz so mix 75 would be more suited, can you run multiple mixes to cover a broader range?
Also, can you use mixes 52, 61, & 75 on your coax since it doesn't filter the operational range you are transmitting in? Say if you wanted to filter out higher and lower freqs that are causing interference, would using that ferrite cause any issues?
Just some late night thinking....

I joke about buying them by the 5-gal bucket, but expense can add up quickly.

I have been using MIX 31 and MIX 61 for my CB-only noise hunts.

No disappointments, per se, they’re an experiment.

That said, some others ‘round here make the mic cord into a set of rosary beads, every mix imaginable an exact number turns of the doubled-length mic cord apart.

Work clarifier, HOLD MIC “Just So”. Drape over forearm. (PTT)


.

 

[Handy Andy]

Work clarifier, HOLD MIC “Just So”. Drape over forearm. (PTT)

And Check SWR ...
You don't want too many Standing Waves
between you and your "Contact"​