[OZAPRS] HF APRS upsets the car's climate control
Ray Wells
vk2tv at exemail.com.au
Fri Dec 19 11:33:05 EST 2008
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
>>>>>> _______________________________________________
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>>>>>> 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
>>>>>
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