CHT and EGT off scale when transmitting

[mkbreezy]

I just finished installation of a D1000 with EMS in a Vans RV-9A The EMS module is mounted on the sub panel LH side between the firewall and the sub panel. During initial checkout noticed that the EGT and CHT indications were going off scale when transmitting on the SL30. All other indications were stable. It is frequency dependent. Worse in the mid freqs. better at each end of the spectrum. Is this a grounding issue? Would wrapping the thermocouple leads with foil tape or braid help? Any assistance would be nice.

 

[marchudson]

mkbreezy

I had the exact same problem with my SL-40 and GNS-430 when transmitting.  Went as far as removing the transmitter and antenna from the aircraft and making it a portable transceiver to make sure it wasn't an antenna grounding issue. I also used an SWR meter to ensure that the cable and antenna were connected properly.  

The fix that worked for ME.

Ordered the LCOM capacitive filters for all three connections that go to the EMS module.  Voila all RF noise now gone.  These are the same LCOM filters that Dynon used to fix some RF issues that some customers were having with the display itself.  

Have a look on LCOM's website.
http://www.l-com.com/productfamily.aspx?id=902

Hope this helps

Marc

 

[mkbreezy]

Ordering them as we speak, thanks for the info.

 

[mmarien]

Same here. I also had the problem with my analog gauges. I'll give the filters a try on my SV-EMS-220.

 

[dynonsupport]

As you guys try this, please post back with your results. We'll be interested to hear if this makes a difference for everyone. Generically, we've recommended getting the antenna and other radio bits away from the EMS module and SkyView Network cabling, but it would be interesting to know if there's another way to squash this issue that a few of you have seen.

 

[lgingell]

I have this issue in my RV also.

CHT/EGT's rise about 50-75 degrees on transmit. MAP goes up also. No other EMS sensors are affected.

I moved a 9 pin filter over to the EMS skynet connector, but the issue was unaffected.

My COM antenna coax is routed near my EGT/CHTS for a few inches (AND my oil temp/pressure/fuel pressure), but nowhere near my MAP sensor wire as far as I can see.

Cheers,
..lance

 

[jakej]

Are you using RG400 coax or equivalent ?

Jake J

 

[mkbreezy]

I just installed the L-Com filters on all 3 connectors on the EMS module. The problem is completely solved. I see just the tiniest movement of the gauges when talking, otherwise the indications are the same with keyed mic, as with no keyed mic. The installation was a breeze. Unscrew the connectors, insert the filters, and screw down the connectors. The screws on the filters on the DB-9 and DB-37 need to be reversed, but thats it.

BTW, everything works like a charm, so far I am delighted with the D1000

 

[marchudson]

Mkbreezy
Glad to see it worked for you.
Marc

 

[rocclobster]

I have the same issue in my Glastar.  I've shielded everything, added grounding braids and even re-routed the comm cable so it ran nowhere near the EMS module, nothing worked.

After reading this post I followed the link to buy the filters. Some of the the filter modules are currently out of stock, 5 week lead time.  The usual suspects like digi-key don't have them either.  Anyone know where to find them besides the L-Com web store?

 

[jakej]

Colin

The filters should work, I have a policy of fitting them to all the composite (including Glastar/Sportsman) aircraft that I work on.

Jake J

 

[rocclobster]

Does anyone know of a source for the L-Com filters besides the L-Com website? They want $43 for the part and $65 for shipping to Alaska. The shipping seems quite excessive for 3 little connectors that can fit in an envelope.

I inquired with Dynon Tech Support but they do not supply the filters for this particular problem. They supplied them for my SL-40 radio rx noise problem. They offered a couple other solutions that I've since implemented, albeit unsuccessfully.