High Amps on Transmit

[Nev]

I've got a Dynon Skyview approximately 5 years old installed in my Bearhawk. When I transmit on the radio, the amperage rises rapidly to 50-60 amps and will set off an alert. Does anyone know how I can fix this issue ?

Any help appreciated.

 

[jakej]

Not enough info eg -
Did this happen recently or has it been an ongoing issue ?
If it's a recent event - did you change anything eg Com antenna location etc ?
What type of antenna coax cable are you using ? RG58 or RG400 ?
Where is that antenna located on the airframe ?

 

[Nev]

It's been an ongoing issue since new that I've been slow to address.
So in that regard nothing has changed - it's always done this.

The VHF antenna is mounted underneath the boot cowl. The radio has always worked very well. The cable is RG400.

Thanks.

 

[airguy]

It's not likely that your system is suddenly pulling that much power and the amperage reading is accurate - unless your system voltage is also sagging significantly during transmit - that's easy to verify. Much more likely that you're getting some stray RF into the EMS box that senses the shunt current. Some of the older EMS boxes were more sensitive to RF and it was a known problem back in the 2010's, I know there was a fix for it but you had to send the EMS box back to Dynon.

Short of that, if you have a break in the coax you can be leaking a lot of RF - this is not likely in the coax run itself if you are using RG400, but would probably be at the termination ends, either at the radio or the antenna. Check those ends, cut and recrimp if they are suspect.

 

[Nev]

Thanks. Definitely the system is not pulling that much power. It seems to be a spurious issue and the stray RF idea seems very plausible.

 

[jakej]

I’d be checking the connectors especially if they’re the type where the shield is held in place with a nut. Also check the centre pin is locked in place as the tip of the pin should be close to being flush with the end of the ‘body’ - that applies to the shield crimp sleeve type as well.

 

[Nev]

I’d be checking the connectors especially if they’re the type where the shield is held in place with a nut. Also check the centre pin is locked in place as the tip of the pin should be close to being flush with the end of the ‘body’ - that applies to the shield crimp sleeve type as well.

Thanks for this. I'll check the items you've mentioned. Appreciated.

 

[GKC Aviation]

Yes, I've seen an installation where on transmit, all the CHT and EGT's go high.
In this case, it was because the VHF antenna coax (even though it was RG400) was run very close to the EMS and EMS wiring harness.
Moving the coax away fixed it.
I don't think the EMS is shielded very well from RF energy, but from memory they did end up bringing out an updated model that was better.

 

[Nev]

Yes, I've seen an installation where on transmit, all the CHT and EGT's go high.
In this case, it was because the VHF antenna coax (even though it was RG400) was run very close to the EMS and EMS wiring harness.
Moving the coax away fixed it.
I don't think the EMS is shielded very well from RF energy, but from memory they did end up bringing out an updated model that was better.

Great - I'll take a look at this too. Thanks.

 

[airguy]

Contact Dynon with the serial number of your EMS, they may have a fix for that. The phone call is free.

 

[jakej]

Your unit is probably the later unit so modifying/replacing it will not change anything if it's an earlier unit in which case a cheaper alternative may be to use the L-C0M brand of 'filtered' dsub connectors. I believe they were used as a temporary measure to mitigate the problem until a permanent solution was found.
Airguys solution is good

 

[kurtfly]

Another thing to consider is the location of the shunt and the EMS differential pair of wires connected. It only takes 50mV (.050 V) difference between the wires to indicate 50AMPS. These wires must be a twisted pair and should be isolated from other high current carrying wires.

Kurt