[OZAPRS] HF APRS upsets the car's climate control

Tim Ahpee tim at ahpee.org
Fri Dec 19 11:43:46 EST 2008 

Hi Ray,

No worries and no offence taken.

Cheers,
Tim

On Fri, Dec 19, 2008 at 11:33:05AM +1100, Ray Wells wrote:
> Ian,
>
> You're absolutely correct. My apology to Tim.
>
> Ray vk2tv
>
> Ian Bennett wrote:
>> Ray,
>> 	Just because you "know" does not mean everyone else does and conveying 
>> knowledge by belittling a person's attempt to do so does not work.
>> 	Had you posted this information previously in a more constructive 
>> tone, you may have saved Tim some work.
>>
>> Ian
>> VK1IAN
>>
>> On Fri, 19 Dec 2008 11:02:05 Ray Wells wrote:
>>   
>>> I'll say it again. You have an antenna radiating lots of RF and you're
>>> worried about radiation from the coax?
>>>
>>> You have vehicle wiring in the presence of a strong RF field from the
>>> antenna, not some piddling, insignificant leakage from the coax which,
>>> by the way, won't be affected by VSWR. Coax doesn't mysteriously become
>>> "leakier" just because the VSWR is high.
>>>
>>> Think about the nature of the situation, and when you have, dump any
>>> notion that radiation from the coax is likely to cause the problem.
>>>
>>> You need to prevent the RF on the wiring from getting into the
>>> controller by applying RF suppression techniques to the controller
>>> wiring. As somebody else commented, make sure the bonnet is bonded. Use
>>> DECENT bonding straps (the braid from RG213 coax should be considered an
>>> absolute minimum. Don't waste your time with RG58 braid) around the
>>> hinges (yes, both of them). Don't expect that to be a cure-all, because
>>> the front of the bonnet is a long way (in RF terms) from the grounding
>>> points, when the hinges are at the windscreen end. Is the problem any
>>> worse/better with the bonnet up/down. That will give an indication of
>>> the effectiveness of bonnet bonding. Fit ferrite "filters" around the
>>> wiring into the controller. RF bypass caps will likely have no effect
>>> because of the difficulty of providing a SHORT, DECENT ground point,
>>> which could also be alive with RF.
>>>
>>> Make yourself a field strength meter (a 1mA FSD moving coil meter,
>>> diode, bypass cap and a sensitivity control) in a metal enclosure with a
>>> coax socket for the input. Use a length of coax with just 25mm of the
>>> inner conductor protruding at the far end (away from the meter). Use
>>> that as a probe to assess the level of RF at various point on the car
>>> wiring. If you need more sensitivity, use a DC blocking cap (say 0.01uF)
>>> attached to the inner conductor of the coax and touch various points of
>>> the wiring with the capacitor. It's extremely simple and effective.
>>>
>>> Suppressing interference both to and from transceivers in a vehicle
>>> situation can be very time consuming and, sometimes, very ineffective.
>>> What works in one case won't work in another, and what you might think
>>> is "earthed" isn't necessarily so. A major trap with heavier 4WD
>>> vehicles is that the body is not necessarily bonded to the chassis, it
>>> sits on rubber mounts. Bonding around those mounts can return a huge
>>> improvement.
>>>
>>> Some years ago a neighbour's diesel Landcruiser produced S9+ noise on
>>> 27MHz. The source of the problem was a combination of the oil sender
>>> unit and the wiring to the instrument panel. I used a probe like the one
>>> described above, attached it  to the affected radio, and probed the
>>> engine compartment. The entire engine was alive with crud. I reduced
>>> that noise to absolutely nil by bonding around the two front rubber body
>>> mounts.
>>>
>>> Suppressing interference problems can take a lot of time, but that time
>>> can be reduced if you don't go chasing improbable causes.
>>>
>>> I had 25 years of installing two-way radios, and some of what I learned
>>> hasn't escaped via that sieve between my ears :-)
>>>
>>> Ray vk2tv
>>>
>>> Tim Ahpee wrote:
>>>     
>>>> Hi Folks,
>>>>
>>>> I spent sometime last night re-routing the coax from the left side of the
>>>> car to the right side of the car. Now the coax is away from the fan. I
>>>> also checked the antenna match using a network analyser and it reports an
>>>> SWR of 1.1:1. I also added a clamp on ferrite torroid onto the coax near
>>>> the antenna end.
>>>>
>>>> So far, no change. At least it's only the fan that it seems to be
>>>> upsetting and nothing crucial like the cruise control :-)
>>>>
>>>> I'm going to have a play with grounding over the weekend and also get a
>>>> hold of a dummy load.
>>>>
>>>> If worst comes to worst I can mount the antenna up the back of the car
>>>> away from the over-sensitive electronics.
>>>>
>>>> Cheers,
>>>> Tim
>>>>
>>>> On Thu, Dec 18, 2008 at 11:40:13AM +1100, Damien Gardner Jnr wrote:
>>>>       
>>>>> Yeah ditto on my the VR Calais I had - ended up using all remote head
>>>>> gear in the boot, with antennas mounted off the boot...  Havent gotten
>>>>> around to looking at what this VHF radio i swapped a mate an MTR-8000
>>>>> for many moons ago is yet, so haven't put radios in the VT wagon and see
>>>>> if that has a problem... :)   The old '87 diesel luxie never had any
>>>>> issues at all. It's just a shame it was such a dog to drive ;)
>>>>>
>>>>> --DG
>>>>>
>>>>> On 17/12/2008, at 8:52 PM, Norm VK3XCI wrote:
>>>>>         
>>>>>> I've been here with my old VN Calais. Make sure the bonnet is bonded
>>>>>> to the rest of the body!!! also the bullbar, tho I think you said the
>>>>>> spotlights are on it. Maybe bond the base of the antenna directly to
>>>>>> the rest of the body. Use double shielded coax?
>>>>>>
>>>>>> Worst possible case, put the antenna at the back of the vehicle. Good
>>>>>> luck, these things are usually simple or impossible.
>>>>>>
>>>>>> Norm VK3XCI
>>>>>>
>>>>>> Tim Ahpee wrote:
>>>>>>           
>>>>>>> G'day Folks,
>>>>>>> I've just got HF APRS running in preparation for my trip at the end
>>>>>>> of the
>>>>>>> year and have come across an interesting one. Each time the rig
>>>>>>> transmits the
>>>>>>> fan in the climate control goes to full power. Nothing else seems to
>>>>>>> be
>>>>>>> affected just the fan. It was a bit of a shock the first time it
>>>>>>> happened. I
>>>>>>> was driving along and heard the TX relays go click then I was
>>>>>>> blasted in the
>>>>>>> face with air. Details:
>>>>>>> Rig: Icom IC-7000
>>>>>>> Car: Toyota Prado 2008 Diesel
>>>>>>> Antenna: Diamond HF30FX mounted on the bull bar
>>>>>>> Any thoughts? I'm wondering if the RF is getting straight into the
>>>>>>> motor
>>>>>>> controller for the fan because if the fan is off nothing happens.
>>>>>>> Cheers,
>>>>>>> Tim
>>>>>>> VK3TZA
>>>>>>> _______________________________________________
>>>>>>> Ozaprs mailing list
>>>>>>> Ozaprs at aprs.net.au
>>>>>>> http://aprs.net.au/mailman/listinfo/ozaprs
>>>>>>>             
>>>>>> --
>>>>>> Regards de Norm, VK3XCI
>>>>>> Mildura on the Murray
>>>>>> QF15bt
>>>>>> _______________________________________________
>>>>>> Ozaprs mailing list
>>>>>> Ozaprs at aprs.net.au
>>>>>> http://aprs.net.au/mailman/listinfo/ozaprs
>>>>>>           
>>>>> _______________________________________________
>>>>> Ozaprs mailing list
>>>>> Ozaprs at aprs.net.au
>>>>> http://aprs.net.au/mailman/listinfo/ozaprs
>>>>>         
>>>> _______________________________________________
>>>> Ozaprs mailing list
>>>> Ozaprs at aprs.net.au
>>>> http://aprs.net.au/mailman/listinfo/ozaprs
>>>>       
>>> _______________________________________________
>>> Ozaprs mailing list
>>> Ozaprs at aprs.net.au
>>> http://aprs.net.au/mailman/listinfo/ozaprs
>>>     
>>
>>
>> _______________________________________________
>> Ozaprs mailing list
>> Ozaprs at aprs.net.au
>> http://aprs.net.au/mailman/listinfo/ozaprs
>>
>>   
>
> _______________________________________________
> Ozaprs mailing list
> Ozaprs at aprs.net.au
> http://aprs.net.au/mailman/listinfo/ozaprs
_______________________________________________
Ozaprs mailing list
Ozaprs at aprs.net.au
http://aprs.net.au/mailman/listinfo/ozaprs

More information about the Ozaprs mailing list