eHam

eHam Forums => Mobile Ham => Topic started by: G7MRV on January 26, 2014, 01:44:01 PM



Title: Snap on ferrites for FT-857 power cable?
Post by: G7MRV on January 26, 2014, 01:44:01 PM
I have my FT-857 mounted in the trunk. I wish to add more suppression to the power cables. Can anyone recommend suitable and effective snap on type ferrites for this task? How many would be reasonably effective against engine impulse noise carried on the power cables?


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: K0BG on January 26, 2014, 02:57:01 PM
The question is, why?

The best ferrite money can buy for noise suppression (mix 31), has a crossover point over 1.5 MHz. Therefore, it is worthless to use for interference below that point. What's more, RF induced or conducted on, or to, the DC power cable just doesn't happen, unless the wiring it totally inadequate.



Title: RE: Snap on ferrites for FT-857 power cable?
Post by: G7MRV on January 26, 2014, 03:18:31 PM
ok, good point  :)

The issue I have is ignition noise, and a fair amount of it. The car is rather old now.
I have the bonnet and boot lids bonded (trunk and hood in US parlance?) but not yet the doors. I also think extra earth bonding is needed inside the engine bay but am having trouble trying to find exactly where I can do that,

My thought was that the impulse noise was being propagated up the power cables. The power for the radio comes directly from the battery, both + and - wired direct to the terminals. The radio is further grounded via its mounting bracket to the metal bodywork in the boot.

I suppose what I should really do is revisit your website!


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: KK4LGR on January 26, 2014, 11:46:48 PM
What make/model car?


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: K7RBW on January 27, 2014, 06:40:30 AM
The issue I have is ignition noise, and a fair amount of it. The car is rather old now.

Maybe the car's old ignition components are the problem? Perhaps it's time for some new wires & plugs (and points, rotor cap, etc. if it's that old).


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: M6GOM on January 27, 2014, 05:37:05 PM
I have my FT-857 mounted in the trunk. I wish to add more suppression to the power cables. Can anyone recommend suitable and effective snap on type ferrites for this task? How many would be reasonably effective against engine impulse noise carried on the power cables?

 Use wide flat braid from the engine block to the bulkhead and also from the exhaust to the underside of the car. There are always suitable bolts on the rear of the engine and nuts on the bulkhead.

How is the antenna mounted?


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: G8YMW on January 28, 2014, 06:30:19 AM
Are you sure that its the power leads that are causing the problem?
I'm with K7RBW, New sparklers (resistive), HT leads rotor arm, distributor cap and if its that old, points and condensor.
What size/rating are the power leads?


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: K0BG on January 28, 2014, 02:29:41 PM
As plugs wear, the gap increases which also increases the level of RFI generated. The more RF energy, the further up the spectrum the harmonics go. Regardless of what the manual says, replacing plugs are about 50k miles is almost a requirement.

If the engine uses wires, they should be replaced too.

Unless the vehicle was made prior to 1973 or so, it won't have points, although it might have a distributor and rotor. Their gap increases with age too.

Probably the most important thing to do, is bond the hood across both hinges, and thee exhaust system in at least three place. If you do everything above, you should be able to get the RFI level down to an S unit or so.


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: K5LXP on January 29, 2014, 06:55:53 AM
My V6 Chevy S-10 had horrible ignition noise.  S9+ on most bands.  I came to discover that while it used resistor plugs it had solid core wires.  I re-vamped the ignition with resistor wires and plugs, then set about doing the "standard" panel, driveline and exhaust bonding procedure.  The  noise went down to around S1, which I was satisfied enough with.

The uptake of this is that there's probably no single solution to the problem.  The total benefit will be the cumulative effects of several techniques and remedies.

Mark K5LXP
Albuquerque, NM


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: G7MRV on January 31, 2014, 01:26:31 AM
Sorry for the delay in replying. Car is a 07 plate Ford Fiesta. Antenna is mounted via a through panel SO239 in the center rear of roof (dead center has my Panorama M8 mount for VHF), Radio is boot mounted, bolted into metal of boot floor. Power cables are independantly run direct to battery terminals via inline fuses located within inches of the battery. Bonnet and Boot door (hood and trunk?) are bonded with braid from offcuts of RG-213 coax. Doors are not yet bonded, neither is exhaust, I dont have the facility to safely work under the car (I can jack it onto axle stands but would feel safer on ramps)

I was looking at bonding from the engine block to the chassis, but although I can locate various suitable bolts on the engine, Im having trouble finding anything on the body thats definately proper metal and not just a panel added on! I suspect if I can get under the car it might be easier to find something.

The engine is a duratec, I dont know too much about its ignition system or injector system, but I dont think its anything I can easily rework. I might be just about ok to swap the plugs!

I was considering the ferrites as at this time of year its too cold for me to work on the car for long, certainly not long enough to work in the engine bay, and wondered if a few ferrites might have some negating effect? I understand that the bonding is the real key here, its just that will take a  lot longer to get completed.

How many additional bonds from the engine block should I be looking at? On aspect I have noticed is that the alternators bolts to the engine block dont look amazingly good, so was considering adding a strap across from the alternator to the engine block, and from there also to the chassis?


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: K7RBW on January 31, 2014, 06:43:18 AM
On aspect I have noticed is that the alternators bolts to the engine block dont look amazingly good, so was considering adding a strap across from the alternator to the engine block, and from there also to the chassis?

That statement made me think that perhaps it's not worn out ignition components but corrosion in an existing ground line or electrical connection. Maybe just a little brushing and sanding is in order? Granted, that's not something fun to do in the rain and the cold.


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: W5LZ on February 03, 2014, 05:32:51 PM
Just for grins, have you tried removing the antenna to see if the noise is still there?
 - Paul


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: K6CPO on February 04, 2014, 10:45:25 AM
There are inline noise filter available that plug right into the power lines on the radio.  I use one on my 1998 Dodge Dakota to quiet alternator noise.  Below is a link to one made by Yaesu...

http://www.hamradio.com/detail.cfm?pid=H0-002787


Title: RE: Snap on ferrites for FT-857 power cable?
Post by: N1GMV on March 10, 2014, 08:01:58 AM
that device is only 13 amps (160 watts) but should suffice, not sure if it would help though. I have one but mine is considerably larger. I may connect mine up to see if it helps.

My car is a 2010 Dodge Challenger and I also have popping. I upped the level of my NB to 9. It helps but still there. I also had some RFI going into my stereo like a talk back while on 15 meter phone.

FYI, cars today use ignition modules, my car does not have plug wires but it has 16 plugs in it since it is a Hemi.

I put snap on Ferrite chokes on the power leads at the battery and again at the radio. I also ran a short ground strap from the rig to the chassis. All of this helped one way or another but I just installed it last night but I will probably be adding more braid to the hood and trunk.

How bad is yours? Mine is not to the point where my rig is un-usable but somewhat annoying.