Re: Feed Line Loss @ Freq vs. Price
At 23cm, is there any difference between the LMR-600 "Super Flex" and the normal one in terms of attenuation?
Super Flex always has slightly more attenuation as it uses a stranded center conductor instead of a solid center conductor. However you must use Super Flex around a rotator as the solid center conductor will break in a year or two.
73,
John KD6OZH
----- Original Message ----- From: "MKM" [email protected] To: [email protected] Sent: Thursday, May 10, 2007 15:37 UTC Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price
At 23cm, is there any difference between the LMR-600 "Super Flex" and the normal one in terms of attenuation?
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This is true. However, the connectors you must put in line from past the rotator to regular LMR-600 to the station would likely eat up all the delta in loss!
----Original Message Follows---- From: "John B. Stephensen" [email protected] To: "MKM" [email protected], [email protected] Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price Date: Thu, 10 May 2007 16:13:00 -0000
Super Flex always has slightly more attenuation as it uses a stranded center conductor instead of a solid center conductor. However you must use Super Flex around a rotator as the solid center conductor will break in a year or two.
73,
John KD6OZH
----- Original Message ----- From: "MKM" [email protected] To: [email protected] Sent: Thursday, May 10, 2007 15:37 UTC Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price
At 23cm, is there any difference between the LMR-600 "Super Flex" and the normal one in terms of attenuation?
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
This is true. However, the connectors you must put in line from past the rotator to regular LMR-600 to the station would likely eat up all the delta in loss!
To continue the thread accurately - we now need to know how lossy specific connectors are.
All of these "runs" described so far are about 40', a "typical" number for a small tower or structure many hams might have... but if you're running 100' up a tower or structure... the clear winner starts to emerge...
1/2" (or bigger!) hardline with a short jumper of something flexible at the top and high-quality N-connectors at that junction.
Right? Feel free to do the math... if you can find real world numbers for connector losses that you trust.
Also keep in mind if you ever plan on "re-purposing" any of the cable runs up the tower for duplexed service (going to put a repeater on the tower via one of your runs of cable), LMR is a very VERY poor choice for duplexing... its design leads to noise and desense problems. Not a problem in non-duplexed service, though.
In calculating cable run losses (that I have constructed) I use the figure of 0.5 dB loss per connector. Perhaps somebody makes them better than I do, however. (HI)
73, John - K8OCL
----Original Message Follows---- From: "Nate Duehr" [email protected] To: [email protected] Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price Date: Thu, 10 May 2007 13:46:35 -0600 (MDT)
This is true. However, the connectors you must put in line from past the rotator to regular LMR-600 to the station would likely eat up all the delta in loss!
To continue the thread accurately - we now need to know how lossy specific connectors are.
All of these "runs" described so far are about 40', a "typical" number for a small tower or structure many hams might have... but if you're running 100' up a tower or structure... the clear winner starts to emerge...
1/2" (or bigger!) hardline with a short jumper of something flexible at the top and high-quality N-connectors at that junction.
Right? Feel free to do the math... if you can find real world numbers for connector losses that you trust.
Also keep in mind if you ever plan on "re-purposing" any of the cable runs up the tower for duplexed service (going to put a repeater on the tower via one of your runs of cable), LMR is a very VERY poor choice for duplexing... its design leads to noise and desense problems. Not a problem in non-duplexed service, though.
-- Nate Duehr, WY0X
_______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "John Champa" [email protected] To: [email protected]; [email protected] Sent: Thursday, May 10, 2007 11:17 PM Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price
In calculating cable run losses (that I have constructed) I use the figure of 0.5 dB loss per connector. Perhaps somebody makes them better than I do, however. (HI)
73, John - K8OCL
Hi John, K8OCL
0.5 dB loss per connector at what frequency ?
If you screw up togheter 6 Male/Female connectors you get a 3 dB attenuator and with 100 watt input 50 watt are dissipated just 50/6= 8.33 watt per connector..........too hot !
73" de
i8CVS Domenico
UHF Series connectors used on 2M was the basis of my statement (0.25 each). I have gotten better results than that. That is just the estimate I used for calculating estimated line loss ahead of actual construction of the line.
----Original Message Follows---- From: "i8cvs" [email protected] To: [email protected],"Nate Duehr" [email protected],"AMSAT-BB" [email protected] Subject: Re: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price Date: Fri, 11 May 2007 04:42:32 +0200
----- Original Message ----- From: "John Champa" [email protected] To: [email protected]; [email protected] Sent: Thursday, May 10, 2007 11:17 PM Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price
In calculating cable run losses (that I have constructed) I use the figure of 0.5 dB loss per connector. Perhaps somebody makes them better than I do, however. (HI)
73, John - K8OCL
Hi John, K8OCL
0.5 dB loss per connector at what frequency ?
If you screw up togheter 6 Male/Female connectors you get a 3 dB attenuator and with 100 watt input 50 watt are dissipated just 50/6= 8.33 watt per connector..........too hot !
73" de
i8CVS Domenico
John,
That is a terrible spec for connector loss. If you use N-type connectors you should not see anymore than 0.05 dB loss/connector up to 1296 (at least). If you are getting more than that using N-connectors, then you are not assembling them correctly. For cable under ten foot length, I cannot measure loss with any accuracy to make meaningful results. If connectors had that much loss, it would show up with inches of coax. I measure the loss using the duplex connections of a spectrum analyzer. I can see 0.1 dB +/- 0.1 dB.
If you are using PL-259 (UHF) connectors for satellite use...shame! They may not be terrible up to 144-MHz but above that they are a no-no. Why? Because they introduce impedance mismatch (bumps) => high loss. And that is why they are no good. Other good connectors are TNC and 7/16-din (real expensive). BNC are OK but not for use where very good impedance match is important. They are usable into mw bands though. For low power the sma is preferred and good to 18-GHz (some are good even higher). N-connectors have been used at 10-GHz but not as good as sma.
Side comment to Nate: What is your problem with LMR cables? They are essentially double-shielded and lower loss than most coax other than hardline. Times Microwave LMR line of coax has equivalents up to 1-5/8 inch hardline for loss specs. If you mean use as jumper cables between the duplexer and the Tx and Rx of a repeater, then one should use RG-143 or Belden-8214 double-shielded cable. That is a shielding issue not a noise issue. If shielding is inadequate, repeater de-sensing can occur that effects the receiver sensitivity (Tx RF gets into the Rx).
I have a commercial 75w VHF repeater using about 60-feet of LMR-600 in service for over ten years with absolutely no problems. This site has about 7 other repeater users, BTW.
73 Ed - KL7UW
At 01:17 PM 5/10/2007, John Champa wrote:
In calculating cable run losses (that I have constructed) I use the figure of 0.5 dB loss per connector. Perhaps somebody makes them better than I do, however. (HI)
73, John - K8OCL
----Original Message Follows---- From: "Nate Duehr" [email protected] To: [email protected] Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price Date: Thu, 10 May 2007 13:46:35 -0600 (MDT)
This is true. However, the connectors you must put in line from past the rotator to regular LMR-600 to the station would likely eat up all the delta in loss!
To continue the thread accurately - we now need to know how lossy specific connectors are.
All of these "runs" described so far are about 40', a "typical" number for a small tower or structure many hams might have... but if you're running 100' up a tower or structure... the clear winner starts to emerge...
1/2" (or bigger!) hardline with a short jumper of something flexible at the top and high-quality N-connectors at that junction.
Right? Feel free to do the math... if you can find real world numbers for connector losses that you trust.
Also keep in mind if you ever plan on "re-purposing" any of the cable runs up the tower for duplexed service (going to put a repeater on the tower via one of your runs of cable), LMR is a very VERY poor choice for duplexing... its design leads to noise and desense problems. Not a problem in non-duplexed service, though.
-- Nate Duehr, WY0X
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
73, Ed - KL7UW ====================================== BP40IQ 50-MHz - 10-GHz www.kl7uw.com 144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w DUBUS Magazine USA Rep [email protected] ======================================
Side comment to Nate: What is your problem with LMR cables?
LMR is essentially a braid-over-foil design, which if it moves physically (has to be tied down properly), all those little "contact points" between the "bumpy" braid and the "flat" foil are all little passive-intermod connections waiting to make noise, in a duplexed system, anyway.
LOTS of people have reported major noise issues with it, in specific environments... a few of the more sensitive commercial tower sites have banned its use... citing it as an intermod/mixing problem in high-RF environments. Not many, but a few.
So it's not really "my" problem, but an overall lack of understanding of its limitations when it got "popular" in the last few years.
I have a commercial 75w VHF repeater using about 60-feet of LMR-600 in service for over ten years with absolutely no problems. This site has about 7 other repeater users, BTW.
You're lucky.
This thread has some of the recent conversation about it on Repeater-Builder... feel free to come over there and ask questions... basically the consensus over there right now is... "If you're getting away with it, great... if you want to do it right, run hard-line."
http://www.mail-archive.com/[email protected]/msg35670.html
Hunt around the thread for more info. There was a really nice article written by Andrew (taken with a grain of salt, since they have a dog in this fight), that described the typical "desense" type noise levels introduced in a system by using LMR. It was significant numbers at longer cable runs, hardline is much "quieter". Unfortunately, I can't find the article right now.
Personally I have no "problem" with LMR, it's just a trade-off like anything else. The entire VHF and up rover setup for the Jeep is done with LMR400 for the weak-signal stuff, using crimp N-connectors... but I won't put it on repeaters anymore.
Saw a chunk of it creating mixing problems one time... only takes once for me to decide messing around with sub-standard cabling at the site "isn't worth it"... when hardline is no more expensive (other than connectors) and lasts over 10 years, even in harsh environments...
As someone pointed out, pre-made 1/2" hardline is actually CHEAPER than some variants of LMR these days... LMR got "popular" and the price went up.
Bob,
Would you kindly please e-mail me OFF LIST at your first opportunity?
Thanks and 73, John Champa, K8OCL
While on this subject, has anyone used a "Return Loss Bridge" (RLB) to measure their actual total system loss. I was planning on doing that when I get my antenna system up and running to give me a base line for future improvements.
Any thoughts?
Thanks. RoD KD0XX
A good friend will come and bail you out of jail, A TRUE friend will be sitting next to you saying.....
"DAMN THAT WAS FUN"
-----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Nate Duehr Sent: Thursday, May 10, 2007 3:47 PM To: [email protected] Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price
This is true. However, the connectors you must put in line
from past the
rotator to regular LMR-600 to the station would likely eat up all the delta in loss!
To continue the thread accurately - we now need to know how lossy specific connectors are.
All of these "runs" described so far are about 40', a "typical" number for a small tower or structure many hams might have... but if you're running 100' up a tower or structure... the clear winner starts to emerge...
1/2" (or bigger!) hardline with a short jumper of something flexible at the top and high-quality N-connectors at that junction.
Right? Feel free to do the math... if you can find real world numbers for connector losses that you trust.
Also keep in mind if you ever plan on "re-purposing" any of the cable runs up the tower for duplexed service (going to put a repeater on the tower via one of your runs of cable), LMR is a very VERY poor choice for duplexing... its design leads to noise and desense problems. Not a problem in non-duplexed service, though.
-- Nate Duehr, WY0X
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "Stargate" [email protected] To: [email protected] Sent: Thursday, May 10, 2007 11:26 PM Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price
While on this subject, has anyone used a "Return Loss Bridge" (RLB) to measure their actual total system loss. I was planning on doing that when I get my antenna
system
up and running to give me a base line for future improvements.
Any thoughts?
Thanks. RoD KD0XX
Hi Rod, KD0XX
Disconnect your coax cable from the antenna connector and short circuit the inner conductor with the outer conductor at your transmission line output end.
Then using your RLB measure the Return Loss at the other end of the line near your TX or RX and convert the measured Return Loss in dB to the equivalent SWR
In this conditions the matched-line loss for the frequency of measurement may then be determined from:
Lm (dB) = 10 log [ (SWR+1) / (SWR-1) ] 10
Where SWR = the SWR value measured at the line input with the other end shorted
Example:
If the measured return loss of your short-circuited line is 2.92 dB corresponding to a SWR = 6 then the matched-line loss of your transmission line at the frequency of measurement is Lm = 1.46 dB
Best 73" de
i8CVS Domenico
MKM expunged ([email protected]):
At 23cm, is there any difference between the LMR-600 "Super Flex" and the normal one in terms of attenuation?
LMR-600 @1296 = 3.056db loss per 100'
LMR-600UF @1296 = 3.641db loss per 100'
-Steve N1JFU
Thank you!
On May 10, 2007, at 1:59 PM, Steve Meuse wrote:
MKM expunged ([email protected]):
At 23cm, is there any difference between the LMR-600 "Super Flex" and the normal one in terms of attenuation?
LMR-600 @1296 = 3.056db loss per 100'
LMR-600UF @1296 = 3.641db loss per 100'
-Steve N1JFU
participants (8)
-
Edward Cole -
i8cvs -
John B. Stephensen -
John Champa -
MKM -
Nate Duehr -
Stargate -
Steve Meuse