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Re: [Paparazzi-devel] Berg Receiver Mod

From: Matthew Currie
Subject: Re: [Paparazzi-devel] Berg Receiver Mod
Date: Thu, 18 Oct 2007 11:07:05 -0700
User-agent: Thunderbird (Windows/20070728)


  Thanks for the info.  I just placed what should be my final order with Mouser with expected delivery for tomorrow.  I will now have black/red/white/blue/grey colors of the 2843/19 Teflon wire.  I assembled an entire harness yesterday and got comfortable with the crimper and used a large optical magnifier to inspect the crimped terminals.  I am confident this combination of wire/crimps/connectors is about the best we can do for this size.

  The RX antenna, referencing the Wiki it says the antenna connection is weak and should be strengthened.  I want to know what exactly this is referring to.  The wire antenna is passing through a PCB hole, upward to the solder point so at initial inspection it appears to be strain relieved.  I am curious what would break, the wire strands in the antenna just outside the RX PCB?  Or is it more possible the antenna will actually break off the solder joint?  Just curious.

  I have disappointing news about the new Male Wire-to-Wire Molex connectors, Mouser appeared to carry them but it appears to be more like they have them in their database only.  I was only able to get a handful of 2 conductor housings and no male crimpable terminals.  The rest are backordered with insane shipping times into the next year!  I will begin searching for these with spare time and see what we can't come up with, I would really like to make some disconnects in my harnesses for flexibility.

Matthew Currie

address@hidden wrote:
Just run the antenna out the wing and it'll be far and perpendicular from everything.  I've found that the Berg works better with a wire antenna cut to some random length than with a base loaded antenna.  Don't know why, I read somewhere that the Berg does some automatic impedence matching magic and I noticed that it comes with a random length antenna (newer versions are 1m).

-- Matthew Currie <address@hidden> wrote:

  Sounds about right.  Just as a side note I am almost SURE they are using some thin conformal coating on this receiver.  It was difficult to get reflow and it gave off an odd odor.  There also appear to be drops of something in between closely spaced components, etc.. I am not absolutely sure but it made me wonder.  You are right that impedance-wise, this circuit could be less susceptible to the affects of moisture but then I had never considered moisture mucking with RF circuitry =)  I will be abandoning the coating and already had some suitable lightweight shrink set aside I had used for building small battery packs.  I also plan on using some surplus 1206 SMT ferrite chokes which I used to filter ~ 72MHz and coming up with a clever way to incorporate them in series with this wiring for a more bulletproof link.  I used to use these in other RC products I designed and they made a dramatic difference to glitching.

  On a somewhat related note.  Would it be more suitable to use a 1/4" whip or something out of solid rod and make an antenna that could get perpendicular faster instead of running past every transceiver in th plane?  Only thinking out loud here.  I have a few of those tiny tuned antennas meant for parkflyers which turn the 30+" wire into a 4" antenna at the expense of a quoted 10% range as well.


address@hidden wrote:

The IR sensors use very large value resistors that are easily affected by humidity but the receiver does not rely on such things.  Also 72MHz is a pretty low frequency and not so sensitive to detuning.  Lastly, Castle Creations doesn't coat these receivers and they know a lot more about it than we do. :)

Just slap some heat shrink on it, keep it away from the GPS, and try to keep the antenna perpendicular to other antennas.

-- Matthew Currie <address@hidden> wrote:

 I will be modifying the Berg 4L receiver tonight and was curious if
there is any reason why I should _not_ coat the entire assembly in an
Aerosol Silicone Conformal Coating for protection mechanically and
problems of moisture in foggier weather, etc.  While I realize the IR
sensors may be of limited use in rain / fog I sure don't want the weak
link to be something I can correct for now.  My only reasons for being
cautious would be RF detuning, contamination, etc.

Matthew Currie

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