CHT/EGT rise when PTT is depressed

[preid]

I noticed in the last couple of flights that my CHT and EGT for 1,2,and 5 rise whenever I or the copilot side depress the PTT switch.
Any ideas why this may be occurring?
Thank you!

 

[rocclobster]

Mine do the same thing. I've tried shielding the wires, moving my comm coax and added a bonding strap to the EMS module but it didn't make any difference at all.

I read in a previous post that the L-Comm d-sub filters remedy the problem but I have not ordered them. L-Comm wanted over $50 for shipping and handling for 3 little D-Sub connectors to AK so I declined.

 

[lgingell]

Put a filter on the EMS connectors and this should help. I have one on each D connector, but the key was a filter on the DB25.

There's another thread on this somewhere, but they are the L-COM filters. http://www.l-com.com/item.aspx?id=3139

Cheers,
..lance

 

[lgingell]

Oh, yes, L-Com are terrible on shipping and horrible to deal with when they send the wrong 25 cent part!

 

[dynonsupport]

I noticed in the last couple of flights that my CHT and EGT for 1,2,and 5 rise whenever I or the copilot side depress the PTT switch.
Any ideas why this may be occurring?
Thank you!

reidvaitor:

Talked to you on the Tech Support phone, and as I explained, this isn't all that common. Some suggestions:

1. Carefully inspect your radio's coaxial cable and antenna installation as you do not want stray RF wandering around on the cabin interior. Ideally, 100% (or as near as the physics of your coax and antenna dictate) should be be transmitted from the radio, through the coaxial cable, and out through the antenna. It would be a good idea to get an avionics tech to help here to check your antenna and coax. He can do a simple test for "SWR" (Standing Wave Ratio) to see if RF is being reflected back into your radio from the antenna not being tuned correctly for the aviation band. He can also temporarily attach a "dummy load" to see if that clears up the problems, and if so, that points to coax / antenna problems.

2. Try routing cables differently and seeing if / when that makes a difference.

3. Try adding a some length to the EGT/CHT wires. Sometimes the EGT/CHT wires are the perfect length to be a receive antenna for the aviation frequencies and thus particular sensitive to stray RF energy.

We don't currently have a recommendation for the filters mentioned by others in this post to be used with the EMS. We understand that some customers have had success with them, but Dynon Engineering has not blessed the use of these filters, so Tech Support cannot.

 

[rfazio1951]

I added the L-Com filters to all three D-sub connectors on the EMS module. It did not help at all, not even a little bit. I moved the EMS module further away from the radio. Mine was mounted right behind the radio. This also did nothing. Now I'm running new RG-400 coax from the radio to the antenna. I had RG-59. We'll see what that does. It is not really a problem except when you are trying to lean. If you press transmit it screws up your settings.

 

[dynonsupport]

I added the L-Com filters to all three D-sub connectors on the EMS module. It did not help at all, not even a little bit. I moved the EMS module further away from the radio. Mine was mounted right behind the radio. This also did nothing. Now I'm running new RG-400 coax from the radio to the antenna. I had RG-59. We'll see what that does. It is not really a problem except when you are trying to lean. If you press transmit it screws up your settings.

I'd be surprised if you actually installed RG59 coaxial cable. That's what's used for cable television, has a solid center conductor, foil shielding, and a characteristic impedance of 75 ohms, and most radios have a characteristic impedance of 50 ohms. Not to mention that most RG59 coax is cheaply made and definitely isn't designed for use with a radio transmitter.

If you did actually install RG59, I think you identified your RF interference issue.

 

[preid]

I spent most of the day working with a Avionics tech. He found everything normal with the radio, coax (RG-400) and antenna. The length of all 6 CHT's are different and it appears that 1,2,and 5 is now anything (aka changes from EGT to CHT, to all spiking)
Cable wise I have the EMS in the far right corner with the probe wires coming through the firewall directly into the EMS on the inside, they are a good 3 feet away from my SL40 and any radio antennas/coax.

Richard- Please respond with your results using the RG-400. If it works with the LCom filters, I buy one, as I believe I have exhausted anything else.

 

[jakej]

I spent most of the day working with a Avionics tech. He found everything normal with the radio, coax (RG-400) and antenna. The length of all 6 CHT's are different and it appears that 1,2,and 5 is now anything (aka changes from EGT to CHT, to all spiking)
Cable wise I have the EMS in the far right corner with the probe wires coming through the firewall directly into the EMS on the inside, they are a good 3 feet away from my SL40 and any radio antennas/coax.

Richard- Please respond with your results using the RG-400. If it works with the LCom filters, I buy one, as I believe I have exhausted anything else.

I do a lot of installations on all types of aircraft so I may be of help to you.

What type of aircraft do you have ? Composite or ally ?

Did changing to RG 400 (the only type to use IMO) do anything ?

Jake J

 

[rfazio1951]

Sorry, I posted that I used RG-59. It was RG-58A/U, stranded center conductor, not RG-59. I had a senior moment. I am in the process of changing the wire now to RG-400.

 

[jakej]

I'm working on this issue with a 'poster' and will post the results here when it's resolved.

FWIW - I've found if you have good quality coax (eg RG400) and component grounding, that prevents 95% of problems.  However there are many other factors involved including quality of connectors, proper crimping or soldering plus a whole lot of other things.

Coax cable in wire bundles - there has been comment about this however, from my experience, I've never had a problem when using RG400 in this situation if I have no other choice.

HTH

Jake J

 

[DennisW]

I just installed the L-Comm Filters and it did not fix the noise issue. I will keep looking for solutions and let you know.

 

[lwheat2083]

Just as I was reading your post I thought I should check my EGT and CHT readings as well and sure enough they jump about 15 degrees as the PTT is pressed. I have the 7" system installed in a Pulsar III which is just about ready for first flight. Personally I don't think this is a particularly big issue in my case, but I certainly appreciate the heads up. Cheers

 

[Sportsman7064]

Has anyone found a solution for this yet? I have the engine temps jumping 15-25 degrees with the PTT, but also the vertical speed indicates a sudden climb...

Looking for advice.

Thanks

Russ

 

[preid]

The solution for the EGT spikes is a new Sv-EMS 220 that will be released in Mid-September. http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1340939442

I have no idea about the Altitude spikes, maybe the upgraded hardware will resolve it as well?

 

[jakej]

Has anyone found a solution for this yet?  I have the engine temps jumping 15-25 degrees with the PTT, but also the vertical speed indicates a sudden climb...

Looking for advice.

Thanks

Russ

pm me, I may be able to help.

Jake J

 

[dynonsupport]

Yep, the next build of the SV-EMS-220 units, which SHOULD BE mid-September or so, will have a change which fixes this issue (it's pretty rare, overall).

 

[Camillo]

I also experience tris issue in my RV9A.
Temperature rise is 50 Celtius degrees on 2 cylinders when transmitting on com1 (Garmin Gns430w) and less than half when transmitting on com2 (Garmin SL40).
Main concern is than when PTT is activated a red CHT alert highlights. Not a real problem, but I have to reset it every time I speak in the radio.
I would be glad to know how to solve the issue.
If new EMS unit will fix it, I will take it.
My installation is RG400 and engine monitor module is attacched to the firewall, pilot side.

 

[rocclobster]

I set my EGT and CHT alarms to turn off automatically once the "red" condition is no longer present. I, too, am looking forward to the new EMS module. If you use the leaning function and have to key the radio before you're done you have to start from the beginning.

 

[Bubblehead]

Any update on availability of the updated EMS 220? I get temp spikes when i transmit which goofs up the lean setpoints.