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Author Topic: JT400 vs LMR400  (Read 2942 times)
KJ4HVL
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Posts: 76




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« on: July 05, 2017, 05:22:20 AM »

Running a roughly 60' run to my VHF / UHF ground plane and hoping to maximize listening distance with a nice low loss coax (and possibly a pre-amp), this run may be re-used for satellite work at some point. For other projects I've used the times microwave LMR400, but I'm considering this time using JT400 (a supposedly similar product). Does anyone have any experience with the quality or behavior of JT400? Am I better off with a known brand of RG213? Should I spend the extra $20 and buy the Times Microwave product?
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W8JX
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« Reply #1 on: July 05, 2017, 06:57:50 AM »

Running a roughly 60' run to my VHF / UHF ground plane and hoping to maximize listening distance with a nice low loss coax (and possibly a pre-amp), this run may be re-used for satellite work at some point. For other projects I've used the times microwave LMR400, but I'm considering this time using JT400 (a supposedly similar product). Does anyone have any experience with the quality or behavior of JT400? Am I better off with a known brand of RG213? Should I spend the extra $20 and buy the Times Microwave product?


Real world  you are on the fence here and can do fine with 213, there is only about .5 db more loss than 400 on 2 meter and about .9 db more than 400 on 440. Neither are deal breakers. If you had a 100 foot or longer run on 440,  I would use a lower loss coax like 9913 or 400.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
N8EKT
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Posts: 595




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« Reply #2 on: July 05, 2017, 06:58:16 PM »

Its been my experience that nothing is better than the original

Most of these "lmr400" equivalent or "9913equivalents"
either use a lesser jacket material or have more sparse braid

I've seen several generic coax varieties over the years that used jacket material that was for indoor use only
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W8JX
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Posts: 12095




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« Reply #3 on: July 05, 2017, 07:40:17 PM »

Its been my experience that nothing is better than the original

Most of these "lmr400" equivalent or "9913equivalents"
either use a lesser jacket material or have more sparse braid

I've seen several generic coax varieties over the years that used jacket material that was for indoor use only


Well there is no mil spec standard for 400 so quality is suspect and in many years of flight test we never used on foot of it. We used 58c, 59, 142,174, 213, 214, 224, 393, 9913 and 1/2, 1 and 3 inch hard line and wave guides too but no 400. I is not a very rugged cable
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KJ4HVL
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Posts: 76




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« Reply #4 on: July 06, 2017, 05:45:16 AM »

I is not a very rugged cable

Well, yeah, I mean it has a solid center conductor, which rules out ruggedness pretty much from the start (especially where there will be lots of movement like a plane).

Price, Performance, Durability (pick two) is how I approach coax. I want to make sure that I'm not sacrificing too much of the latter two to save a nickel. The suspect braid is what I was worried about, but I recently tore into some RG-8 that was RandL branded (jetstream), and the braid was fully covering and thick, so I'm guessing I'll be ok unless that brand has crapped the bed recently. The sample I have is fairly old (guessing late 90's production).
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W8JX
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« Reply #5 on: July 06, 2017, 10:19:54 AM »

Well, yeah, I mean it has a solid center conductor, which rules out ruggedness pretty much from the start (especially where there will be lots of movement like a plane).

Not really, it is all firmly clamped inside pressurized fuselage and outside exposed to extremes in temperatures and pressure changes. 400 uses minimal dielectric density for a little less loss but trade of is cable is easily damaged bending it too tight,  clamping it too tight or even stepping on it. To me it a bad trade off and overrated for HF. 213 is very rugged by comparison.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KJ4HVL
Member

Posts: 76




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« Reply #6 on: July 06, 2017, 10:57:06 AM »

Not really, it is all firmly clamped inside pressurized fuselage and outside exposed to extremes in temperatures and pressure changes.

Once had a prof who worked on the awacs and said they had to use oil filled, pressurized waveguide to minimize the arcing due to the lower pressure and reduced water content (to bleed charge) in the air. Amazing stuff!
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W8JX
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Posts: 12095




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« Reply #7 on: July 06, 2017, 11:10:29 AM »

Not really, it is all firmly clamped inside pressurized fuselage and outside exposed to extremes in temperatures and pressure changes.

Once had a prof who worked on the awacs and said they had to use oil filled, pressurized waveguide to minimize the arcing due to the lower pressure and reduced water content (to bleed charge) in the air. Amazing stuff!

We used pressurized with dry air passed through a dryer or nitrogen depending on application. Nitrogen does not have ability to absorb or carry moisture. 
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Ham since 1969....  Old School 20wpm REAL Extra Class..
N6YFM
Member

Posts: 517




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« Reply #8 on: August 02, 2017, 11:13:53 AM »

Its been my experience that nothing is better than the original

Most of these "lmr400" equivalent or "9913equivalents"
either use a lesser jacket material or have more sparse braid

I've seen several generic coax varieties over the years that used jacket material that was for indoor use only


Well there is no mil spec standard for 400 so quality is suspect and in many years of flight test we never used on foot of it. We used 58c, 59, 142,174, 213, 214, 224, 393, 9913 and 1/2, 1 and 3 inch hard line and wave guides too but no 400. I is not a very rugged cable

Yes, but, ...  In MIL and in Flight conditions? :-)   Seriously.

He is talking about putting in a home QTH run, which is typically not something where you have recruits stomping on it,
airline mechanics ramming it with cargo containers, etc.    It's a home QTH.   I have 4 runs of LMR-400UF at my home,
and in the years it's been there, the only footsteps upon it may have been termites or ants.   It is just fine and looks/works
as good as new.

For field day, lots of foot traffic, lots of moving it around, coiling and uncoiling, tossing about, sure;  The MIL stuff.
But for a permanent installation, home QTH, cell phone tower;  LMR-400 is great.

Neal
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W8JX
Member

Posts: 12095




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« Reply #9 on: August 02, 2017, 07:30:49 PM »

Its been my experience that nothing is better than the original

Most of these "lmr400" equivalent or "9913equivalents"
either use a lesser jacket material or have more sparse braid

I've seen several generic coax varieties over the years that used jacket material that was for indoor use only


Well there is no mil spec standard for 400 so quality is suspect and in many years of flight test we never used on foot of it. We used 58c, 59, 142,174, 213, 214, 224, 393, 9913 and 1/2, 1 and 3 inch hard line and wave guides too but no 400. I is not a very rugged cable

Yes, but, ...  In MIL and in Flight conditions? :-)   Seriously.

He is talking about putting in a home QTH run, which is typically not something where you have recruits stomping on it,
airline mechanics ramming it with cargo containers, etc.    It's a home QTH.   I have 4 runs of LMR-400UF at my home,
and in the years it's been there, the only footsteps upon it may have been termites or ants.   It is just fine and looks/works
as good as new.

For field day, lots of foot traffic, lots of moving it around, coiling and uncoiling, tossing about, sure;  The MIL stuff.
But for a permanent installation, home QTH, cell phone tower;  LMR-400 is great.

Neal

Yes seriously, for HF ruggedness it important to me  and a lot more important than a few tenths of a db loss and cable that can easily be damaged.  I would only consider 9913 or 400 on long runs on 2m or 440, never on HF.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KJ4HVL
Member

Posts: 76




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« Reply #10 on: August 03, 2017, 11:23:38 AM »

Strangely enough the initial question never got answered... I was using 400 regardless of the opines here since I've used it before (unless the price got too high).

The original question was whether or not the Jetstream brand from RandL is a reputable product, or if it is such a bad knock-off/copy that it isn't worth ones time (in which case I'd probably forgo the 400 for a name brand 213/u).

In the meantime, I've managed to get my hands on some surplus cell-tower and/or military coax for free (Even terminated!) thanks to one of my old university prof's. Picking it up tonight.
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KM1H
Member

Posts: 2675




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« Reply #11 on: August 18, 2017, 04:09:04 PM »

Ive used standard RG-8 size 50 and 75 Ohm foam cables for several decades with never any damage. This is with 4 towers and lots of antennas from 160M to microwave.

All the commercial/public safety 2 way VHF/UHF stations use LMR-400 when the runs do not require LMR-600/900 or hardline. I havent seen RG-213 at those sites in about 20 years. 9913 is a poor choice in a harsh outdoor environment due to moisture ingress thru the jacket.
JX has had his head so far up his long ago flight test environment he will never see daylight. Roll Eyes

Carl
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