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  #11  
Old 01-31-2017, 10:48 AM
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mikeyj350 mikeyj350 is offline
 
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Quote:
Originally Posted by Mike F View Post
I've used RG-393 in a couple of larger aircraft (not RV's). It has the same physical qualities as RG-400 (double shield, silver plate, FEP jacket - not PVC) but a larger diameter (same as RG-213 I believe). It is expensive, I pay around $6/ft. At 1000 MHz, 15' has a 1.125 dB loss.
Hey Mike, thanks a ton for the info! I hadn't come across RG-393 but with a little more research it looks like it might be perfect! Diameter-wise yeah it is still pretty fat but still a smidge smaller than RG-213 (0.39" vs. 0.405")...at least it isn't bigger...

Cost-wise yeah if I can get it at $6/foot and two $8 connectors (looks like they share some part numbers with the 213) it's not ideal but at least not terrible for just one cable.

I've already got a message into the G3Xpert folks (asking about the 213), we'll see what they have to say too but I think I found a winner here.

Again, appreciate all the help from the VAF brain trust!
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  #12  
Old 01-31-2017, 11:26 AM
Canadian_JOY Canadian_JOY is offline
 
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Longer coax is never a good substitute for optimal antenna placement. I say this based on too many years of dealing with very expensive and cumbersome antenna configurations on a variety of special-purpose aircraft.

I'm not sure where you've mounted your comm antenna. Obtaining the minimum distance between comm and transponder is important, but on an aircraft of this size should be easily accomplished. I've got both a belly-mount comm and transponder antenna on our Sportsman - no problem getting the separation. The RV10 should be pretty easy in this regard.

Big fat coax is great stuff, but its lifecycle costs are VERY high. Sure, you'll never have to touch it, until that day you find it's been chafed by unseen contact with a sharp edge and it has to be replaced. Or a connector corrodes and has to be replaced. All these things are very good reasons to stick with the cheapest, simplest, most common coax cable and connectors.
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  #13  
Old 01-31-2017, 11:48 AM
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digidocs digidocs is offline
 
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Check out LMR-240-UF from Times Microwave.
Times Coax Loss Calculator

It's 0.240" diameter, has a double shield (foil+braid), costs <$1/ft, uses readily available connectors, and shows 1.5-1.7dB loss for your 15' run. Do make sure you get the Ultraflex version (LMR-240-UF) as it uses a stranded center conductor instead of solid. There are even places that will make up the whole assembly for you for reasonable cost. The PVC jacket isn't really a big deal, just install it so no chafing is happening.

David
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  #14  
Old 01-31-2017, 06:22 PM
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Default Transponder Antenna Location

"Longer coax is never a good substitute for optimal antenna placement. I say this based on too many years of dealing with very expensive and cumbersome antenna configurations on a variety of special-purpose aircraft."

I have to agree with this statement. My only regret with my -10 build was not paying more attention to weight reduction/elimination. While you may find the right 15' cable to minimize attenuation, the real solution is to find a location to eliminate 10-12' of unnecessary cable. Other considerations are ensuring the right size ground plane, eliminating shadowing, and ease of accessibility.

Brian
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Last edited by 10builder : 01-31-2017 at 06:26 PM.
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  #15  
Old 03-24-2018, 08:39 PM
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sglynn sglynn is offline
 
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Default Transponder Coax

Can RG58 coax be used for Transponder? I'm using RG400 for radios and GPS and I've run out. But I have a 5 foot piece of RG58 which would fit for my transponder. Is RG58 good enough for transponder or do I need to buy more RG400. I noted that my ELT came with a piece of RG58.
thanks
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  #16  
Old 03-25-2018, 08:59 AM
RVDan RVDan is offline
 
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Quote:
Originally Posted by sglynn View Post
Can RG58 coax be used for Transponder? I'm using RG400 for radios and GPS and I've run out. But I have a 5 foot piece of RG58 which would fit for my transponder. Is RG58 good enough for transponder or do I need to buy more RG400.
Only if it were 1960 would it be good enough. . RG 58- PVC jacketed therefore burns well, and many brands have very poor shielding leading to interference with other systems. Get RG 142 or RG400 depending on length.
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  #17  
Old 03-25-2018, 10:07 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quality RG-58 coax (think Belden) actually has slightly less loss per foot than RG-400. I used RG-58 in my first plane and all is well after 18 years.

I now use RG-400 in my builds as it is more mechanically robust and I got over the high price tag. For our applications, the double shield is really not needed, but it does not hurt either.

Carl
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  #18  
Old 03-25-2018, 02:37 PM
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GalinHdz GalinHdz is offline
 
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Quote:
Originally Posted by sglynn View Post
Can RG58 coax be used for Transponder? I'm using RG400 for radios and GPS and I've run out. But I have a 5 foot piece of RG58 which would fit for my transponder. Is RG58 good enough for transponder or do I need to buy more RG400. I noted that my ELT came with a piece of RG58.
thanks
Short answer: Yes it can be used.
Better answer: You should use RG-400.

But a 5ft run isn't going to make much of a difference. Depending on the RG58 used, it might be about .25 of a db. You loose more than that with each connector.

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Last edited by GalinHdz : 03-25-2018 at 02:52 PM.
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