RV-12 ELT antenna

[JRo]

I just finished Ops checking my 406 ELT. Fortunately I had my electronics specialist buddy on hand. After successfully testing the ELT, and entering the due dates for ALL 3 batteries (ELT, audio alerter & Remote control) both on the devices and in the Aircraft Maintenance Record, we went to re-stow the ELT.

My ET buddy 'bout had a fit when he saw how Vans instructed us to stow that co-ax antennae cable! Co-ax cables have a specified minimum bend radius. They should be gently "looped" to stow. Vans has us "kinking" them again and again to be tightly tie wrapped to the ELT in a small bundle. I've been assured by Jerry that, if stowed as instructed, rather than gently looped, it is only a matter of time and heat exposure before the cable will fail.

Who knew!?

Jim R.
N448JR

 

[az_gila]

RG-58A/U - the one with the multi-strand center core - is usually listed as a 2 inch minimum bend radius.

RG-400 - to the Mil Spec - is listed as a 1 inch minimum bend radius.

How tight do the RV-12 instruction want the bend radius?

 

[Tony_T]

ELT Antenna cable routing

The bend radius is more than 1":

Plans:

Tony

 

[az_gila]

...

My ET buddy 'bout had a fit when he saw how Vans instructed us to stow that co-ax antennae cable! Co-ax cables have a specified minimum bend radius. They should be gently "looped" to stow. Vans has us "kinking" them again and again to be tightly tie wrapped to the ELT in a small bundle. I've been assured by Jerry that, if stowed as instructed, rather than gently looped, it is only a matter of time and heat exposure before the cable will fail.

Who knew!?

Jim R.
N448JR

Show your buddy this data sheet....

http://www.wellshow.com/spec/cable/Harbour-RG400.pdf

 

[rvbuilder2002]

The bend radius is more than 1":

Plans:

Tony

Actually, the KAI drawings for the ACK 406 Mh ELT (the one currently suppied in the avionics kit) do show a much tighter bend radius. The one shown in these now obsolete drawings was the Artex. The error will be corrected in a future revision.

Aside from Gils chart, the common rule of thumb for coax minimum bend radius is 5 - 6 X the diam of the coax (depending on which coax it is).

 

[az_gila]

Aside from Gils chart, the common rule of thumb for coax minimum bend radius is 5 - 6 X the diam of the coax (depending on which coax it is).

RG-58 and RG-400 are essentially the same diameter and yet they have a 2:1 difference in bend radius.

...and that is why "common rules of thumb" are not very useful...

Look up the specific data, it's much better than a rule of thumb...

 

[rvbuilder2002]

RG-58 and RG-400 are essentially the same diameter and yet they have a 2:1 difference in bend radius.

...and that is why "common rules of thumb" are not very useful...

Look up the specific data, it's much better than a rule of thumb...

Well, I actually did look it up a while back (though I no longer remember where), and the chart I looked at put RG-400 at 5X the diam., and RG-58U at 6X, so I am not just winging it Gil...
But it does just go to show you that on the internet you can find a lot of information that is not correct. Yea, unfortunately even here on VA (though I can assure you I am not the only one providing it )

 

[az_gila]

Well, I actually did look it up a while back (though I no longer remember where), and the chart I looked at put RG-400 at 5X the diam., and RG-58U at 6X, so I am not just winging it Gil...
But it does just go to show you that on the internet you can find a lot of information that is not correct. Yea, unfortunately even here on VA (though I can assure you I am not the only one providing it )

Maybe, but "charts" on the internet can be just the same as "rules of thumb"...

In this case it's actually quite easy to get real data from the cable manufacturers, and that real data rarely (ever?) quotes bend radius as a multiple of diameter.

RG58A/U straight from Belden -

http://www.belden.com/techdatas/english/8219.pdf

2 inch minimum radius - just over 10x the diameter.

RG400 from another manufacturer/supplier with numbers taken from the M17/128-RG400 Mil Spec.

http://www.farnell.com/datasheets/1714215.pdf

1 inch minimum bend radius - just over 5x the diameter.

Don't use table/charts and rules of thumb, go for real data from the suppliers...

I'm sure the engineers at Vans work that way.