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Hoskinmage
Member
Username: Hoskinmage
Post Number: 80
Registered: 3-2002
| | Posted on Thursday, January 10, 2019 - 7:32 pm: | 
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I'm kinda In over my head the wife wanted a 2013 kia and I'm not sure what size box it will handle? I have 2 radios a 959 galaxy(regular not a high drive) and a vr 9000 that I could drive it with the question is how much can these little cars handle and how many watts(saftly) can I use,get. It's a big difference than my 1999 jeep wrangler so im stuck. I dont want to damage the electronics in the little car but at the same times sometimes we all need a little help to get over the jump. Could someone please give me some help I'd rather be safe than sorry,if you know what I mean? I k ow the fr 9000 will drive it harder and the 959 is a single final radio will drive it less I like to put anywhere between 14 to 1/2 watt key up no more in to eather one. If someone could help me It would be APPRECIATED |
Tech237
Moderator
Username: Tech237
Post Number: 1937
Registered: 4-2004
| | Posted on Friday, January 11, 2019 - 8:22 am: |
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I used to run 100W (Ham) in a Kia Spectra, if that helps at all, BUT, I had shielded power cabling direct to battery,with a commode mode choke right at the radio, 90% shield on the coax and the antenna mounted as far away as possible from any auto electronics.
IN other words, if you use good installation practices, you should not have any issues, with the car, Now issues from the car to the radio can be another story, as I had to add a capacitor across the fuel pump to quieten it's noise.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Ke0koy
Junior Member
Username: Ke0koy
Post Number: 11
Registered: 12-2018
| | Posted on Friday, January 11, 2019 - 10:31 pm: |
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Common mode chokes are usually placed nearest the antenna connection as that is where common mode currents originate. The discontinuity of the shielding and skin effect cause signals that normally travel along the inside surface of the braid to access the outer surface of the braid and come back in the vehicle making the coax act as an antenna to wreak havoc on, say... THE CAR'S COMPUTER (and speakers etc..)!
Having an RFI choke at the DC input of the radio makes plenty of sense, but a COMMON MODE choke AT THE RADIO makes NO SENSE AT ALL. |
Tech237
Moderator
Username: Tech237
Post Number: 1938
Registered: 4-2004
| | Posted on Monday, January 14, 2019 - 11:47 am: |
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KE0KOY they can also be used on power cabling too, at the radio, which is what I specified. Used them many time, both professionally and as a Ham, to reduce/remove power-line noise issues.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Ke0koy
Junior Member
Username: Ke0koy
Post Number: 12
Registered: 12-2018
| | Posted on Tuesday, January 15, 2019 - 12:11 pm: |
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Tech237: Power lines are generally isolated from the RF source and RF chokes are used to filter out any RF the cable may have picked up through RF coupling. Think of the power cable acting as a receiving antenna.
Common mode currents happen when a conductor, one you do not wish to have RF on, happens to be electrically connected to a source of RF current. It is essentially giving just one side of what is supposed to be a balanced line an alternate path to follow. This is why twin lead or ladder line is considered a balanced feed line and coax is considered an unbalanced feed line. When RF leaves a shielded radio enclosure it travels down the inside of the coax. The RF currents travel along the center conductor and back along the INSIDE of the shield braid (it is normally confined to the inside surface only due to skin effect). Once the RF reaches the antenna, the center conductor drives one element and an equal current is returned through the other element or counterpoise and then travels back down the inner shield surface. Problem is, unlike the center conductor, the inner surface of the braid is not only electrically connected to the counterpoise element, but it is also electrically connected to the outer surface of the braid. This causes unwanted RF to flow on the outer surface of the braid and come back toward the radio. Hence blocking it at that point.
Although an RF choke and a common-mode choke do the same thing, block RF current flow along a specific path, they are distinguished from each other in terms because the cause of the unwanted RF is different. Therefore, "RF choke" and "common-mode choke" should not be used interchangeably as you are doing. It makes it difficult to the learner to research the "what" and "why" and just confuses people that are trying to learn the hobby.
Side question... Are all the TechXXX moderators on this forum service techs for Copper Electronics? |
Tech237
Moderator
Username: Tech237
Post Number: 1939
Registered: 4-2004
| | Posted on Wednesday, January 16, 2019 - 9:08 am: |
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Power lines can still pick up RF and other noises and the describes choke does work extremely well to remove them before they get to the radio.
Per Wikipedia - The common-mode choke, where two coils are wound on a single core, is useful for suppression of electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply lines and for prevention of malfunctioning of power electronics device. It passes differential currents (equal but opposite), while blocking common-mode currents.[3] The magnetic flux produced by differential-mode (DM) currents in the core tend to cancel each other out since the windings are negative coupled. Thus, the choke presents little inductance or impedance to DM currents. Normally this also means that the core will not saturate for large DM currents and the maximum current rating is instead determined by the heating effect of the winding resistance. The CM currents, however, see a high impedance because of the combined inductance of the positive coupled windings.
What I described is, based on that definition a Common-mode choke.
KE0KOY - most of us(if not all) are not.
I am an ex-RAAF radio tech who taught Electronic to apprentices. ran my own Communications business until health prohibited it. These day, with the aid of a Service Dog, I work in a call Center helping Field Techs repair Treadmills, Stepmills etc.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Ke0koy
Junior Member
Username: Ke0koy
Post Number: 13
Registered: 12-2018
| | Posted on Thursday, January 17, 2019 - 12:01 am: |
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I was not trying to make a battle out of someone else's post and I concede in the idea that you are correct with great apology. That said, my final words regarding the topic are as follows:
I guess we had better write the ARRL and tell them to make a correction to their Handbook for Radio Communications because they use the term "common-mode" choke almost exclusively with respect to coax connections near an antenna feed point and RFI chokes almost exclusively for DC line filtering. If we use the "2 coils on a single core" definition (which makes sense given the nature of the term), that completely excludes the use of the term for coax applications, because as seen from the outside of the coax, the coax is a single conductor or "coil". I guess all the people who were involved in that publication have it backwards. They must not have checked with wikipedia first and that totally screwed up my understanding. Forgive me  |
Dale
Senior Member
Username: Dale
Post Number: 2356
Registered: 12-2002
| | Posted on Sunday, January 20, 2019 - 6:17 pm: |
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id start simple with just the galaxy 959 no amp. see how noise ya gonna get .before thinking about a amp find out how many amp ya altenator is.your gonna need x amount of amps to run the vehicle plus x amount for radio gear =???this is just how ive done for many many years.in my setups with just 100 watts i had no issues. hope this helps
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
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Hoskinmage
Member
Username: Hoskinmage
Post Number: 83
Registered: 3-2002
| | Posted on Friday, February 08, 2019 - 1:13 pm: |
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Thank you all so much I'm old and usually in older cars I'd just hook them up to the battery and set my antenna ground everything good and then it would be good to go. With these new cars and all the fancy stuff they have I was just learry about everything I could mess up and it would be cost alot to fix not to mention the beating my wife would give me. The last hookup I used was in my 99 jeep wrangler I ran a dr 9000 or 959 with my 667 and did pretty good but like I said I'm not sure about her car maybe I should just run my vr 9000,30 to 35 watts, and just play it safe. Thank all of you for your help I really do appreciate it. This list is always my first go to place to find anything out about my hobby thank y'all so much
Snowman,273, in Kentucky thank you |
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