Re: [Repeater-Builder] Cable lengths again
Good timing, I just now have one on the bench tune up. This 526 was originally on 454/459MHz. Both cables from the tee to the cans are 12 inches. This is measured from the far end of the N connector on both ends. In other words, it includes the length of the N connector. The 2 cables are Intercomp RG-214/U, so if you use something else you will have to take Velocity Factor in mind. Interestingly, the 4 inter-cavity cables are PDCC Type RG-8A/U cable. I don't know if this was an economy choice, or if the cables needed to be more flexible to make the sharp bends. Or, someone replaced some or all of the cables on the duplexer I have here. I'll see if I can check a couple of other 526's. 73, Joe, K1ike Al Wolfe wrote: Have a Phelps Dodge 526 UHF duplexer that's missing the cables from the tee to the cans. Google came up with one vague reference where someone thought these cables were 12 inches long. Is there a chart or formula somewhere to determine their proper length? Thanks, Al, K9SI Yahoo! Groups Links
RE: [Repeater-Builder] Cable prep and crimp on connectors
For small-diameter cables, I have Paladin CST Vario strippers. These are completely adjustable - you insert/remove the blade cartridges to get the strip dimensions you want for 3-level stripping, and you adjust the depths of the blades for each strip level for whatever cable you're using (i.e. the depths are varied depending on the diameter of the cable jacket, dielectric, and center conductor). These won't do large cables like RG8, 214, 393, etc. It's a bit tedious to set up the blades initially, but once you have them set, it's the best tool I've found. I have a few of them set up for different cables (RG58, RG400, RG59, and another that I adjust as-needed for other oddball cables). For larger cables, I just do them with a knife. I'm pretty good with the knife (practice makes perfect), and I can do as good of a job with a knife as the Vario does, but the Vario is faster. --- Jeff WN3A -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Dennis Wade Sent: Wednesday, December 02, 2009 5:50 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Cable prep and crimp on connectors Good Afternoon, I've been following the previous threads and doing a lot of research on the issue of crimp on coax connectors vs. solder. Based on that research and several very useful threads on this list I purchased a Paladin Crimp All tool with a couple of dies for RG-8/213 and type and RG-58/59 type cables. I bought some connectors from the same industrial jobber here locally to practice my installation technique. The results haven't been too bad...they look fine, are solidly on the cable, ohm out fine, etc (solder center pins). I used a sharp utility knife for prepping the cable. (Yes, I did verify that the hex dimensions of the dies match the connector manufacturer's specifications.) I really didn't like the knife approach..it worked, but was pretty tedious for me. So, the question is... For those who use something other than a utility knife, what is the coax prep tool of choice? Do you do a 2-level tool or 3? Is there such a think as one tool for both RG 8 and RG 58/59/RG-6 type cables? I'd rather not have one tool per cable size if I can help it. Thanks for your input! Dennis -- I've been wondering lately...Where am I going and why AM I in this hand basket?? - Dennis L. Wade KG6ZI Carmichael, CA No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.426 / Virus Database: 270.14.82/2525 - Release Date: 12/02/09 07:33:00
RE: [Repeater-Builder] Cable prep and crimp on connectors
http://www.dse.com.au/cgi-bin/dse.storefront/4b1707bf00b2dd42273fc0a87e01064e/Product/View/T3640 http://www.ripley-tools.com/tools.php?tool=LDTcategory=Drop%20Cable%20Tools To: Repeater-Builder@yahoogroups.com From: j...@broadsci.com Date: Wed, 2 Dec 2009 18:15:19 -0500 Subject: RE: [Repeater-Builder] Cable prep and crimp on connectors For small-diameter cables, I have Paladin CST Vario strippers. These are completely adjustable - you insert/remove the blade cartridges to get the strip dimensions you want for 3-level stripping, and you adjust the depths of the blades for each strip level for whatever cable you're using (i.e. the depths are varied depending on the diameter of the cable jacket, dielectric, and center conductor). These won't do large cables like RG8, 214, 393, etc. It's a bit tedious to set up the blades initially, but once you have them set, it's the best tool I've found. I have a few of them set up for different cables (RG58, RG400, RG59, and another that I adjust as-needed for other oddball cables). For larger cables, I just do them with a knife. I'm pretty good with the knife (practice makes perfect), and I can do as good of a job with a knife as the Vario does, but the Vario is faster. --- Jeff WN3A -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Dennis Wade Sent: Wednesday, December 02, 2009 5:50 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Cable prep and crimp on connectors Good Afternoon, I've been following the previous threads and doing a lot of research on the issue of crimp on coax connectors vs. solder. Based on that research and several very useful threads on this list I purchased a Paladin Crimp All tool with a couple of dies for RG-8/213 and type and RG-58/59 type cables. I bought some connectors from the same industrial jobber here locally to practice my installation technique. The results haven't been too bad...they look fine, are solidly on the cable, ohm out fine, etc (solder center pins). I used a sharp utility knife for prepping the cable. (Yes, I did verify that the hex dimensions of the dies match the connector manufacturer's specifications.) I really didn't like the knife approach..it worked, but was pretty tedious for me. So, the question is... For those who use something other than a utility knife, what is the coax prep tool of choice? Do you do a 2-level tool or 3? Is there such a think as one tool for both RG 8 and RG 58/59/RG-6 type cables? I'd rather not have one tool per cable size if I can help it. Thanks for your input! Dennis -- I've been wondering lately...Where am I going and why AM I in this hand basket?? - Dennis L. Wade KG6ZI Carmichael, CA No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.426 / Virus Database: 270.14.82/2525 - Release Date: 12/02/09 07:33:00 _ Use Messenger in your Hotmail inbox Find out how http://windowslive.ninemsn.com.au/hotmail/article/823454/web-im-for-hotmail-is-here
RE: [Repeater-Builder] Cable identity
I think it's 72-Ohm To: Repeater-Builder@yahoogroups.com From: cruising7...@aol.com Date: Sat, 23 May 2009 21:21:23 -0400 Subject: [Repeater-Builder] Cable identity Anybody know the nominal impedance of a coax cable labeled: Digital Microwave Corp LK 11? It has a copper solid center conductor (looks like 22 gauge), 3/16 foam dialectic that fits into an F connector for RG-6U, an inner aluminum foil shield and an outer braid shield. It looks like video cable but I can't find any specs on it. Thanks Bruce K7IJt A strong credit score is 700 or above. See Yours in Just 2 Easy Steps! _ Looking to move somewhere new this winter? Let ninemsn property help http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Edomain%2Ecom%2Eau%2F%3Fs%5Fcid%3DFDMedia%3ANineMSN%5FHotmail%5FTagline_t=774152450_r=Domain_tagline_m=EXT
RE: [Repeater-Builder] Cable velocity
Mike, The number E86650 is a listing reference for Underwriter's Laboratories. It is used to identify a class of wire and/or cable, not a specific part number. There may be dozens of cable products that share the same UL Listing number. Please advise the complete string of numbers that is stamped along the cable, and we may be able to identify what product you have. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of mike Sent: Monday, February 16, 2009 6:17 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Cable velocity I have been searching for the velocity factor for E86650 cable. This was the stamp on the cable. I think it is simular to RG-59 but want to make sure. I need to build a phasing harness and wanted to use this cable and of course the velocity factor is an important in determining the length. Thanks for any help Mike
RE: [Repeater-Builder] Cable velocity
If you have access to an MFJ antenna anal like the 259 series, in the manual it shows you how to determine the VF with it given a known length of cable to test. Don't know how accurate the measurement will be, but should get you close. Ralph W4XE -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of mike Sent: Monday, February 16, 2009 8:17 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Cable velocity I have been searching for the velocity factor for E86650 cable. This was the stamp on the cable. I think it is simular to RG-59 but want to make sure. I need to build a phasing harness and wanted to use this cable and of course the velocity factor is an important in determining the length. Thanks for any help Mike Yahoo! Groups Links
Re: [Repeater-Builder] Cable velocity
hi there -- Your making this all to hard -- if the coax is teflon then it is most likely .78 or .89 and if it isn't then it is .66. All of the velocity factors are in the ARRL antenna handbook. All you really need is information about the material in the coax and it will be easy to do. whether the center is foam, teflon, or plastic. take the velocity factor for it and built a 2 port harness. put 50 ohm resistors on the ports and measure the input SWR. If it is low, then measure the power into the harness and measure the power at one port. It shouldbe ~3db down. then your good to go. If it looks funny then meaure up and down a Meg and see if it gets any better. Assuming it does then your harness is long or short for the frequency you want to make it for. But most of the time you will be will within the necessary length if you get the correct factor. No matter who made it. GL -- Rick On Mon, Feb 16, 2009 at 7:27 PM, Ralph Hogan rhog...@comcast.net wrote: If you have access to an MFJ antenna anal like the 259 series, in the manual it shows you how to determine the VF with it given a known length of cable to test. Don't know how accurate the measurement will be, but should get you close. Ralph W4XE -Original Message- From: Repeater-Builder@yahoogroups.comRepeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.comRepeater-Builder%40yahoogroups.com] On Behalf Of mike Sent: Monday, February 16, 2009 8:17 AM To: Repeater-Builder@yahoogroups.com Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Cable velocity I have been searching for the velocity factor for E86650 cable. This was the stamp on the cable. I think it is simular to RG-59 but want to make sure. I need to build a phasing harness and wanted to use this cable and of course the velocity factor is an important in determining the length. Thanks for any help Mike Yahoo! Groups Links
RE: [Repeater-Builder] Cable length for NOTCH cavity?
So... I tuned a spare can as a notch (~19db) at freq X and intend to place it in-line with the Radius in hopes of removing (lowering) the level of freq X getting into the Radius transmitter. A 20 dB reduction should reduce the intermod by 40 dB IF the mixing is happening in the Radius. I hope. I intend to remove the antenna cable from the Radius, plug it into the T at the can and run a double-shielded cable from the can to the Radius. Does the length of the added cable matter? For the most part, no, it won't matter. If you were putting multiple cavities in series, with the notches all on the same frequency, cable lengths would be more critical. As long as the notch cavity is high-Q enough, and its return loss is high at the Radius' Tx and Rx frequencies, there won't be a problem. A more definitive test would be to just stick an isolator (dual stage preferably) between the Radius and the antenna. Key up the Radius and transmitter X, see if your receiver Y hears it. Sure, the receiver is going to be deaf while you do the test, but it will conclusive, and will only take a minute or so to run the test... --- Jeff WN3A
Re: [Repeater-Builder] Cable length for NOTCH cavity?
I trust you plan to do this with the Radius owner's blessing, and with him present? If not, DON'T touch his radio or feedline - you're setting yourself up for a world of legal trouble if he has problems down the line! 73, George, KA3HSW / WQGJ413 - Original Message - From: Bill Powell [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, July 26, 2008 9:29 PM Subject: [Repeater-Builder] Cable length for NOTCH cavity? [snip] So... I tuned a spare can as a notch (~19db) at freq X and intend to place it in-line with the Radius in hopes of removing (lowering) the level of freq X getting into the Radius transmitter. A 20 dB reduction should reduce the intermod by 40 dB IF the mixing is happening in the Radius. I hope. I intend to remove the antenna cable from the Radius, plug it into the T at the can and run a double-shielded cable from the can to the Radius.
RE: [Repeater-Builder] Cable formula
Sure, a UHF isolator will not protect the transmitter from VHF transmitter junk. But isn't the flip side that out of band VHF junk is less likely to produce UHF transmitter intermod than in band transmitter junk? Not necessarily. If it were the other way around (UHF coming back down the hose into a VHF transmitter), the harmonic filter built into the PA would prevent the VHF energy from getting to the devices. I had a UHF repeater (GE Mastr II 1/4 kW tube) with a VHF remote base (25 watt Micor mobile). The two antennas were about 20' apart from tip of the VHF to bottom of the UHF. I had mix problems in the tube PA that produces products at frequencies that intermod math would never predict to occur when the remote base Tx was keyed up. Adding a pass cavity to the repeater Tx cured it. And also, while a VHF band pass cavity might do its job resisting unwanted in band stuff, doesn't this cavity still easily pass undesired junk at frequency multiples? Sometimes yes. A quarter wave cavity will resonate just fine at odd multiples. The converse isn't true though; a UHF pass cavity will do a good job of keeping out VHF. --- Jeff
RE: [Repeater-Builder] Cable formula
The other ways to correct the problem, other than using a different transmitter that is not bothered by reactive loads as much, is to use a Z match or try different length cables that make the transmitter happier. But if the transmitter is bothered by the bad Z at frequencies outside of the pass, any matching device you put in line is only going to throw off the Z at the pass frequency. You can't have a duplexer that presents 50+j0 at the pass frequency, and then add a matching device between it and the PA and still have 50+j0 at the transmitter at the pass frequency. Sure, you can give the PA 50+j0 at some other off-channel frequency by doing this, but at the expense of messing up the pass performance, this seems like it's only creating new problems. Both of these transform the impedance/reactance presented by the duplexer to something more palatable to the transmitter and allow it to produce the power intended. If you have a PA that is happy with a good load at the carrier frequency, but isn't happy with the Z at other frequencies where it shouldn't be making power, I'd have to say you have a problem with the amplifier that needs to be fixed. The antenna system shouldn't have to be the cure for the amplifier's ills. I've never had a good PA (emphasis on good) that got unstable if it was looking into a matched load at the carrier frequency regardless of what was going on off-channel. There is no sin involved in using different length cables to make the system work properly. It is not a band-aid approach to mask other problems. Well, I guess we'll have to agree to disagree. The real problem is that some transmitters, because of the way they are designed, do not like reactive loads. They should like a good load at the carrier frequency, and be tolerant of strange load Z's off-channel. A PA that has a tendency to run away just because the load Z at frequencies well removed from carrier isn't perfect is an accident waiting to happen. Even if you mess with cable lengths and Z-matchers and walk away from the site with the PA running clean, there's a good chance the next time the antenna ices up or the HVAC fails that you'll be getting calls about spurs coming from your box. If I have a PA go spurious, for ANY reason, whether during commissioning or sometime during operation, it comes out of service until it can be fixed. That's just me. Close spaced duplexers will be the worst with off frequency reactance as the impedance has to change quickly as you move away from the wanted frequency in order for the duplexer to do its job. Mostly agree, except for notch-only duplexers with tend to have a fairly wide range of tolerable load Z outside the notch, and notch duplexers are fairly common in close-spaced situations. --- Jeff
Re: [Repeater-Builder] Cable formula
Doesn't the isolator typically installed at the transmitter output spin off any anything reflected from the duplexer (or the feedline) into it's load? In a message dated 7/1/2007 5:33:33 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: But at some off frequency that is not 50+j0 that impedance is going to get transformed into something yet again by the time the cable reaches the transmitter. ** See what's free at http://www.aol.com.
RE: [Repeater-Builder] Cable formula
Yes it does, if you have an isolator installed at the transmitter. With an isolator on the transmitter the transmitter will always see 50 ohms no matter what the load on the other end of the isolator is. There should be no problems with off frequency reactance when an isolator is used. But any reflected power into the isolators load (from on frequency signal) is lost in heat and never reaches the antenna. With an isolator, if the duplexer is not presenting a pure 50 ohms (at the wanted frequency) to the output of the isolator you could put a wattmeter between the isolator and the isolator load and change cable lengths between duplexer and isolator or tune a Z matcher if you have one, for minimum power into the isolators load. That will give you maximum power to the antenna and you will have a near perfect 50 ohm load on the transmitter always. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, July 01, 2007 8:30 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Cable formula Doesn't the isolator typically installed at the transmitter output spin off any anything reflected from the duplexer (or the feedline) into it's load? In a message dated 7/1/2007 5:33:33 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: But at some off frequency that is not 50+j0 that impedance is going to get transformed into something yet again by the time the cable reaches the transmitter. _ See what's free at AOL.com http://www.aol.com?ncid=AOLAOF0002000503 .
Re: [Repeater-Builder] Cable formula
That (isolator in place of tee) is how moto configured their Q package UHF Med Radio. The receive port gets the receive signal plus reflected energy that the preselector bounced back...never heard of that damaging an isolator, matter of fact, aside from burning up too small loads or lightning, I have never run into a damaged isolator, but I am sure there are instances - I have 14, 800 mhz smr boxes, and 80, 800 EDACS stations, plus 30 something UHF repeaters, I can only recall one piston capacitor failure on a telewave dual junction job. Steve NU5D. Gary Schafer wrote: Why would you ever want to do that? Unless you like destroying isolators. :) 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Steve S. Bosshard (NU5D) Sent: Sunday, July 01, 2007 8:52 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Cable formula That would be the typical installation, unless you install the isolator at the output of the duplexer with the #1 (input) toward the TX cavities, #3 (load) toward the receive cavities, and #2 port (output) toward the antenna, used in place of the TEE fitting. Steve NU5D [EMAIL PROTECTED] wrote: Doesn't the isolator typically installed at the transmitter output spin off any anything reflected from the duplexer (or the feedline) into it's load? In a message dated 7/1/2007 5:33:33 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: But at some off frequency that is not 50+j0 that impedance is going to get transformed into something yet again by the time the cable reaches the transmitter.
RE: [Repeater-Builder] Cable formula
Hi Steve, I don't recall ever seeing that done. What was the purpose of using an isolator there? As to toasting the isolator, if you should loose the antenna etc. there would be a short at the tx frequency rather than a load (assuming there is some kind of cavity between isolator and receiver). 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Steve S. Bosshard (NU5D) Sent: Sunday, July 01, 2007 9:35 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Cable formula That (isolator in place of tee) is how moto configured their Q package UHF Med Radio. The receive port gets the receive signal plus reflected energy that the preselector bounced back...never heard of that damaging an isolator, matter of fact, aside from burning up too small loads or lightning, I have never run into a damaged isolator, but I am sure there are instances - I have 14, 800 mhz smr boxes, and 80, 800 EDACS stations, plus 30 something UHF repeaters, I can only recall one piston capacitor failure on a telewave dual junction job. Steve NU5D. Gary Schafer wrote: Why would you ever want to do that? Unless you like destroying isolators. :) 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Steve S. Bosshard (NU5D) Sent: Sunday, July 01, 2007 8:52 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Cable formula That would be the typical installation, unless you install the isolator at the output of the duplexer with the #1 (input) toward the TX cavities, #3 (load) toward the receive cavities, and #2 port (output) toward the antenna, used in place of the TEE fitting. Steve NU5D [EMAIL PROTECTED] wrote: Doesn't the isolator typically installed at the transmitter output spin off any anything reflected from the duplexer (or the feedline) into it's load? In a message dated 7/1/2007 5:33:33 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: But at some off frequency that is not 50+j0 that impedance is going to get transformed into something yet again by the time the cable reaches the transmitter. Yahoo! Groups Links
Re: [Repeater-Builder] Cable formula
I remember asking Lloyd at Wacom about using an isolator in the output - seems like he told me that it allowed more flexibility in cable lengths on the output - might make sense because the Q package had frequencies from 458 to 468 with the apcor carry in units. Ancient history - nightmares when they gave trouble.. If I get the chance I will call him on the phone - see how retirement is going, etc. Steve. Gary Schafer wrote: Hi Steve, I don't recall ever seeing that done. What was the purpose of using an isolator there? As to toasting the isolator, if you should loose the antenna etc. there would be a short at the tx frequency rather than a load (assuming there is some kind of cavity between isolator and receiver). 73 Gary K4FMX
RE: [Repeater-Builder] Cable formula
Doesn't the isolator typically installed at the transmitter output spin off any anything reflected from the duplexer (or the feedline) into it's load? The generic answer is yes, but the qualified answer is that isolators, like everything else, have a finite bandwidth, so if the energy is far removed from the design frequency of the isolator, it doesn't do its job as well. At far-removed frequencies, some of the power incident on the output power (i.e. what's coming back down the hose) gets reflected at the isolator due to a poor match, some will makes its way around to the reject load, and some will make it 240 degrees around to the transmitter. As an example of the limitations of an isolator, a UHF isolator on a UHF repeater isn't going to isolate your PA very well from highband signals coming down the line. A bandpass cavity between the isolator and the duplexer will. --- Jeff
RE: [Repeater-Builder] Cable formula
If your duplexer presents 50+j0 at its input at the operating frequency and you are using 50 ohm cable to connect it to the transmitter then the transmitter is always going to see 50+j0 at the operating frequency no matter what the cable length is. But at some off frequency that is not 50+j0 that impedance is going to get transformed into something yet again by the time the cable reaches the transmitter. And depending on how long or short you make that cable will depend on what transformation it will make to that off frequency impedance all the while still delivering 50+j0 at the operating frequency. So cable length can be used to change unwanted reactance of off frequency things. Of course. But if you stuck a Z-matcher between the duplexer and the PA, then what started out as 50+j0 on-channel is not going to be 50+j0 at the PA. That was my point - the Z-matcher - not cable lengths. Even if the duplexer is not a perfect 50 ohms, changing cable lengths can have enough of an effect on off frequency things to make the system work sometimes. The sometimes is what troubles me... Transistors are strange animals. The do not equate to tubes in there operation especially when broad band combining devices are used at the output of the transistor amplifiers as most do. The devices themselves do strange things in the presents of reactance. That's mostly why many amplifiers have swr shutdown circuits or power roll back. Yeah, but those foldback circuits usually rely on a directional coupler to monitor reflected power. If all of the energy (well, almost all of it anyway) is being produced on-channel, the directional coupler is going to sense nothing and the transmitter is going to run full bore and be happy. If the PA were to go spurious, and all of the off-channel garbage came back down the line, then it would fold back. But if the PA's clean, and it's looking into a well-matched load, there should be no reason to fold back. problems are generally not one of excess current because of reflected power but the excess current the devices draw is from the unwanted reactance that they see. You're talking about reactive currents flowing in the matching networks I presume. But those reactances are present *inside* the PA, before the point where it is connected to the outside 50+j0 world. Most bipolars will operate into an infinite VSWR without giving up the ghost. Excess reactive currents within the PA circuitry will manifest as higher current draw, which is yet one more reason why I always recommend watching current consumption when doing any kind of matching trickery. Sometimes a duplexer just doesn't present a perfect 50 ohms to the transmitter either. Some transmitters will start cutting back the power with little reflected power. Others may not be able to put out all the power it is supposed to if it does not see a perfect 50 ohms. These are some of the reasons most duplexer manufacturers recommend trying different cable lengths between the duplexer and transmitter. You can't convert to a perfect 50 ohms using cable lengths if the load isn't already 50 ohms. I've said before, and I'm saying it again. If your duplexer 50 ohms load, you can pull all of the 50 ohm cables you want out of your bag and you'll never get it back to 50 ohms at the PA. But if the duplexer is designed, built, and tuned right, it should be very close 50 ohms. I can't think of any duplexer I've ever tuned up on a VNA that didn't have at least 20 dB return loss at the pass frequency, with many often being 30 dB or more. Of course, that's only as good as your antenna load, but let's keep that out of the equation for now since we're talking about matching between the PA and duplexer only. All transmitters are not created equal. Amen to that brother. I do agree with you that gross problems that show up are signs of problems that need to be fixed other than changing cables. See, we do agree on something! --- Jeff
RE: [Repeater-Builder] Cable formula
Hi Steve, I don't recall ever seeing that done. What was the purpose of using an isolator there? Steve will probably reply too, but I'll give you the quick answer. UHF Micor mobiles all came stock with an isolator in the antenna network, just like their big brother base/repeater stations. When the radio was in Rx mode, a relay switch the reject port on the isolator to the receiver instead of the load. When it was in Tx, the relay switched the reject port back to the load. With this arrangement, you never had full PA power going through the T/R relay, only reject power, so presumably they did it that way as a means of prolonging the life of the relay contacts (just a guess). --- Jeff
RE: [Repeater-Builder] Cable formula
You can't convert to a perfect 50 ohms using cable lengths if the load isn't already 50 ohms. I've said before, and I'm saying it again. If your duplexer 50 ohms load, you can pull all of the 50 ohm cables you want out of your bag and you'll never get it back to 50 ohms at the PA. Boy, I really butchered the English language on that one. It's late. Rewritten: You can't convert to a perfect 50 ohms using cable lengths if the load isn't already 50 ohms. I've said it before, and I'm saying it again. If your duplexer isn't a 50 ohm load, you can pull all of the 50 ohm cables you want out of your bag and you'll never get it back to 50 ohms at the PA. --- Jeff
RE: [Repeater-Builder] Cable formula
I remember when the micro first came out. I thought I remembered that the isolator was in there to help with transmitter stability when a perfect load was not applied. It may have well been to preserve the relay as well. Seems that I remember something about relay problems in the early days of that radio?? 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Sunday, July 01, 2007 10:47 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable formula Hi Steve, I don't recall ever seeing that done. What was the purpose of using an isolator there? Steve will probably reply too, but I'll give you the quick answer. UHF Micor mobiles all came stock with an isolator in the antenna network, just like their big brother base/repeater stations. When the radio was in Rx mode, a relay switch the reject port on the isolator to the receiver instead of the load. When it was in Tx, the relay switched the reject port back to the load. With this arrangement, you never had full PA power going through the T/R relay, only reject power, so presumably they did it that way as a means of prolonging the life of the relay contacts (just a guess). --- Jeff Yahoo! Groups Links
RE: [Repeater-Builder] Cable formula
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Sunday, July 01, 2007 10:51 PM To: 'Jeff DePolo'; Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable formula You can't convert to a perfect 50 ohms using cable lengths if the load isn't already 50 ohms. I've said before, and I'm saying it again. If your duplexer 50 ohms load, you can pull all of the 50 ohm cables you want out of your bag and you'll never get it back to 50 ohms at the PA. Boy, I really butchered the English language on that one. It's late. Rewritten: You can't convert to a perfect 50 ohms using cable lengths if the load isn't already 50 ohms. I've said it before, and I'm saying it again. If your duplexer isn't a 50 ohm load, you can pull all of the 50 ohm cables you want out of your bag and you'll never get it back to 50 ohms at the PA. --- Jeff Heh heh, I followed what you meant anyway Jeff. Yes I agree that you will never get it back to 50 ohms with a 50 ohm cable and I didn't mean to imply that you could although I guess that's what it sounded like as I wrote it. What I meant was that you can usually obtain some impedance that the transmitter likes better than what the duplexer might be supplying with a random length cable. Please note that most duplexer manufacturers recommend trying different cable lengths to cure the type of problems we have been discussing. 73 Gary K4FMX
Re: [Repeater-Builder] Cable formula
Sure, a UHF isolator will not protect the transmitter from VHF transmitter junk. But isn't the flip side that out of band VHF junk is less likely to produce UHF transmitter intermod than in band transmitter junk? And also, while a VHF band pass cavity might do its job resisting unwanted in band stuff, doesn't this cavity still easily pass undesired junk at frequency multiples? In a message dated 7/1/2007 8:49:50 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: As an example of the limitations of an isolator, a UHF isolator on a UHF repeater isn't going to isolate your PA very well from highband signals coming down the line. A bandpass cavity between the isolator and the duplexer will. ** See what's free at http://www.aol.com.
Re: [Repeater-Builder] Cable formula
OK, There was a long and detailed thread about z matchers on this group abou a year ago? Lots of interesting stuff about line matching emerged.. dont take my word for it have a look in the archives... I can only describe what I measure and that is cable leakage from a jumper between the transmitter and the duplexer when a DB products z matcher was used. (The z matcher was very nicley made with gold plated piston caps etc.) The cable leakage stopped when the z matcher was removed and the cable length was altered for optimum. Ive just dug out my line stretcher : 874-lk20L constant impedance adjustable line- general radio USA no striped paint here im afraid! Ian Ashford G8PWE - Original Message - From: [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 30, 2007 3:50 AM Subject: Re: [Repeater-Builder] Cable formula A good quality Z-Matcher has isolation caps on the trimmer ports so I don't think the matcher itself is producing any RF radiation. I don't understand your description of the z Matcher as introducing any mismatch. The mismatch is already there as a result of some disparity between the source, load and cable impedances. All the matcher does is permit you to match the source and cable impedances. In a message dated 6/29/2007 4:40:45 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: The z matcher is another option but in my practical experience it makes the jumper radiate RF you spend all that money on RG214/RG400 double silver plated shielding and then deliberatley mismatch it? Ian Ashford G8PWE -- See what's free at AOL.com.
RE: [Repeater-Builder] Cable formula
However, the load impedance of most PAs will vary significantly with the drive level, I think you meant source impedance. and the input impedance of a duplexer cavity is always reactive Not necessarily. You can tune a duplexer very close to 50+j0 at the pass frequency. It's at frequencies off the center frequency that the selective nature of the duplexer makes it appear as a Z other than 50+j0. However, a simpler approach is to install an impedance matching device, sometimes called a Z-Matcher, at the output of the PA and adjusting it for maximum forward power. I disagree with this and feel it is bad advice. The point where the transmitter makes maximum power may occur at some load Z other than what the transmitter was designed for. Just because you can eek out a few extra watts by futzing with the Z-matcher doesn't mean you've done anything to improve the stability of the amplifier, nor is it guaranteed to be operating at maximum efficiency, nor do you know if the increase in power you're seeing is due to new spurious/oscillation products being generated due to a bad match. If there is a means of adjusting the loading on the PA via a Z-matcher, be it internal or external to the PA, it should first be set flat at 50+j0 on a VNA or return loss bridge, then hooked up to the PA, and while monitoring current draw, power output, AND spectral purity, make minor adjustments if necessary to find the best balance. The Z-matcher itself performs as if it were a narrow-band device in the sense that it will only correctly match at a single frequency. The load Z of the duplexer, which varies as you get away from its tuned pass frequency, is going to present a varying load, which the Z-matcher is going to transform again, maybe for the better, maybe for the worse. So, at best, the Z-matcher is a band aid in my book. I would much rather see an isolator with a very good input return loss on the output of the PA if there are problems that can defintively be proven to be caused by the load Z of the duplexer and antenna system. I've always maintained that if you have amplifier stability problems or problems achieving rated specs for the PA (power out, current draw, spurious, etc.), then you've got fundamental problems that need to be fixed either in the antenna system or the amplifier itself. --- Jeff
RE: [Repeater-Builder] Cable formula
I don't think the cable cares whether the source and load impedances are 50 ohms resistive. I think the cable is indifferent to whether the load and source values are resistive or whether they present a complex impedance involving +/- J. as long as the composite value looks like 50 ohms. The cable only acts as a transformer if the *load* Z is not the same as the cable's characteristic Z. It doesn't care about the source Z; the mismatch that occurs at the source end only affects power transfer into the cable at that point. The conventional wisdom generally expressed is that as long as the cavities are properly tuned, that the interconnect length from the TX is immaterial. I question that: Properly tuned? When what's properly tuned and for what parameter? Is the pass section of the cavity(s) being tuned for maximum output or is it tuned for minimum reflection back to the TX source? Reflection (S11). Always always always tune pass or pass/reject cavity filters for best match (pounding on the desk as I type). Too many manufacturers' instructions say to tune for maximum power transfer or least insertion loss, probably because they assume the field techs don't have equipment for measuring return loss properly. That's just not good advice in my book. If the filter is designed and built right, the insertion loss minima and return loss maxima should conincide very closely. Even if they're off a tad and you can't get them to line up perfectly, you're always better off taking 10 dB more return loss in exchange for 0.1 dB of insertion loss degradation. That primarily applies to our little narrowband two-way radio world. In wideband applications, there are other things involved, such as group delay, that come into play, but for what we're talking about, return loss is the key. Only if the TX output impedance exactly matches the cavity impedance and the impedance of the interconnecting cable will the cavity tuning point be the same for either parameter. To assume that the TX output impedance is 50 ohms is optimistic and as you point out, altering the power level of the TX can affect TX output Z, the amount dependant on what TX stages are used to control TX output. Let's straighten something out here before we get off track. Most transmitters don't HAVE a 50 ohm source Z. They are designed to work INTO a 50 ohm Z. They have internal matching transformers (stripline or otherwise) to convert the very-low-Z output of the bipolar transistors to something approaching 50 ohms so that when it is connected to our external 50 ohm world that the devices are able to transfer power. Considering how nit-picky forum members are about designing and building their systems, (and I mean that in the best sense of the word), it seems inconsistent to be indifferent to how the duplexers might be affected by inserting what is potentially a radical impedance transformer between the TX and the cavities. In the absence of any way to measure any source and load mismatch, using a 1/2 wave (or half wave repeating) cable length will at least keep any existing mismatch status quo. It won't improve the match but at least it won't increase a mismatch because the 1/2 wave length simply repeats the TX output Z and does not act as a line transformer. But as the cable length departs from a 1/2 wave and approaches a 1/4 wave, the game changes and a 1/4 wave interconnect between a mismatched source and load can produce some eye opening shifts in the impedance reflected to the load and back to the source. Whether you have a half-wave or a quarter-wave cable terminated by a mismatched load, the VSWR remains the same. As as a simple example, assume the Z of the duplexer is 100 ohms. If you use a half-wave cable, the PA sees 100 ohms, a 2:1 VSWR. If the cable is a quarter wave, it transforms the 100 ohms to 25 ohms, again a 2:1 VSWR. Yes, the Z is not the same, but the VSWR is. You don't know whether the PA will be better off looking into the 25 ohm load versus the 100 ohm load, so why would you hold fast to the half-wave rule? For a given load Z, the VSWR remains constant no matter what cable length you use. A 50 ohm cable can't transform a non-50 ohm load to 50 ohms; it can only roll you around the Smith Chart at a constant VSWR, that being something other than 1:1. Round and round the Smith Chart we go, where she stops, nobody knows. Point being, if there is a mismatch, using a half wave cable does nothing to improve your chances of making your PA happy any more than would a quarter wave cable or any other random length. Without knowing the actual impedences involved, your odds of making an improvement using an X-length cable (pick your favorite value for X) are 50/50, nothing more, nothing less. Also keep in mind that the transformation the cable does in the case of a load mismatch is, for all practical purposes, random as you sweep across a range of
RE: [Repeater-Builder] Cable formula
OK so you have a reel of cable and two connectors to make up the jumper between transmitter and duplexer. The duplexer is tuned using 50 ohm test gear and the transmitter has been optimised into a 50 ohm load. Unfortunatley the output impedance of the transmitter is not 50 ohms and a length of cable to the duplexer will transform this impedance,detuning the first can in the transmit chain. No, it won't, you're putting the cart before the horse. The duplexer and antenna system is the load. You can't change the Z of the load by changing the Z of the source. Think about it this way. Get rid of your duplexer and antenna and replace them with a fixed resistor, pick a random value, say 1000 ohms, and use a perfect half-wave cable between the resistor and your PA. Now use three different amplifiers to transmit into this 1000 ohm load. Does each PA have the same source Z? No. Has your load Z changed?No. Has the Z at the input to the half-wave cable changed? No. No matter what you do at the source end, the load Z is 1000 ohms and will remain that way for ever and ever Amen. Let's look at it another way using a practical example. Say you have a single bandpass cavity filter that is properly tuned to present 50+j0 at its input port when its output port is terminated with a 50+j0 load. Now you hook it up to a PA that has a strange source impedence using a half-wave cable with a Bird wattmeter somewhere in the middle (its location in terms of distance from either end is immaterial). Will the Bird show any reflected power? Of course not; the Z on the transmission line is still 50 ohms, the E and I are still in-phase at a 50:1 amplitude ratio, the cavity hasn't been detuned at all. The Z on the line is 50+j0, the Z at the input to the cavity is 50+j0, the Z of the load Z is 50+j0. Now, if you look in the REVERSE direction, FROM the duplexer INTO the transmitter, as you change PA's the Z looking the other way is going to vary, but that's not what we're trying to match here. If we want to go down that road, I would argue just how BAD a Z-matcher could potentially be when used on the transmit side of a duplexer in terms of how it can throw off the termination Z and mess up the RECEIVE side performance. Ponder that for a bit (hint: what should be an open at the antenna tee no longer is). A Z-matcher is no substitute for an isolator. --- Jeff
Re: [Repeater-Builder] Cable formula
Do you recall if the leakage you observed was on channel or whether it was broadband noise? In a message dated 6/30/2007 3:53:42 A.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: The cable leakage stopped when the z matcher was removed and the cable length was altered for optimum. ** See what's free at http://www.aol.com.
Re: [Repeater-Builder] Cable formula
I don't think I ever suggested otherwise. I never said that using a half wave cable would improve anything. What I did say was that a half wave cable would repeat the prevailing condition neither making it better or worse and I further said that using any variation from a half wave cable could either mitigate the mismatch or aggravate it. Having said that, I still think that whatever measures you want to undertake to improve matching, utilizing a half-wave cable is the most coherent way to start. In a message dated 6/30/2007 8:54:45 A.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: Point being, if there is a mismatch, using a half wave cable does nothing to improve your chances of making your PA happy any more than would a quarter wave cable or any other random length. Without knowing the actual impedences involved, your odds of making an improvement using an X-length cable (pick your favorite value for X) are 50/50, nothing more, nothing less. ** See what's free at http://www.aol.com.
Re: [Repeater-Builder] Cable formula
Jeff You make some excellent points. Thanks! Bruce K7IJ ** See what's free at http://www.aol.com.
RE: [Repeater-Builder] Cable formula
I don't think I ever suggested otherwise. I never said that using a half wave cable would improve anything. What I did say was that a half wave cable would repeat the prevailing condition neither making it better or worse and I further said that using any variation from a half wave cable could either mitigate the mismatch or aggravate it. Having said that, I still think that whatever measures you want to undertake to improve matching, utilizing a half-wave cable is the most coherent way to start. What I was getting at was that the rule-of-thumb you recommended, i.e. sticking with a half-wave cable, doesn't give you any better or any worse of a chance in getting the right match. The rule could just as well be whatever cable is long enough to get from the transmitter to the duplexer and it would have just as good of a chance in making the PA happy. --- Jeff
Re: [Repeater-Builder] Cable formula
Can't argue with your analysis. My only point is that if you are intent on dealing with a TX to duplexer mismatch, a half wave cable replicates what ever mismatch exists. A random length cable can mask the real world condition by making the apparent mismatch better or worse than it really is. Do you have any thoughts on why or how a well designed Z match could produce cable radiation? In a message dated 6/30/2007 1:03:51 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: What I was getting at was that the rule-of-thumb you recommended, i.e. sticking with a half-wave cable, doesn't give you any better or any worse of a chance in getting the right match. The rule could just as well be whatever cable is long enough to get from the transmitter to the duplexer and it would have just as good of a chance in making the PA happy. ** See what's free at http://www.aol.com.
Re: [Repeater-Builder] Cable formula
I was thinking the same thing. I was wondering how the connection at the transmitter looked. My bet would be that this is where the real problem is. Chuck WB2EDV - Original Message - From: Jeff DePolo [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 30, 2007 6:22 PM Subject: RE: [Repeater-Builder] Cable formula Do you have any thoughts on why or how a well designed Z match could produce cable radiation? For the feedline to radiate, there would have to be currents flowing on the shield. It would seem to me the only way to get that to happen would be if there was an imperfect shield connection at the mating connector at one end or the other. Most Z-matchers I've dissected use a length of wire as an L, with shunt trimmer caps. Assuming the enclosure itself is bonded well to the connectors at either end, I can't come up with a good reason why such a device inserted in a transmission line would cause shield currents to flow absent a connector issue. --- Jeff
RE: [Repeater-Builder] Cable formula
Don, The length of that jumper cable must consider both the length of any cable between the TX output jack and the power amplifier itself, as well as the length of the coupling loop inside of the duplexer cavity. If the output of the PA and the input of the duplexer were purely resistive, the cable length would be irrelevant. However, the load impedance of most PAs will vary significantly with the drive level, and the input impedance of a duplexer cavity is always reactive. Therefore, there is no pat formula for determining the optimum length of the jumper cable. In most instances, the TX jumper cable acts as an impedance transformer of sorts, and the optimum length can be determined by a laborious cut-and-try method, or by experimenting with the addition of elbow adapters. However, a simpler approach is to install an impedance matching device, sometimes called a Z-Matcher, at the output of the PA and adjusting it for maximum forward power. If you have a vector network analyzer, you can then measure the transformation value of the jumper and Z-matcher combination, and fabricate a new jumper cable that is equivalent. This may not be cost-effective, since the round trip back to the shop probably will cost a lot more in time and fuel than a Z-matcher costs. A VNA is not something that most installers want to carry around in the service truck. If your repeater changes to a lower power level when on a backup battery, be aware that the cable length that is a good match at full power will no longer be a good match when running on the backup battery. That may not be a problem for you, but it is something to keep in mind. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Don Morehouse Sent: Friday, June 29, 2007 8:25 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Cable formula Does anyone know the formula for the cable length between a repeater and the duplexer? Thanks Don VE7EDA
Re: [Repeater-Builder] Cable formula
The length from the repeater to the duplexer isno critical (or SHOULD not be when properly tuned). Therefore, there is no 'formula' other than you want it as short as possible yet allowing enough flex/extra that it won't get stressed. Joe M. Don Morehouse wrote: Does anyone know the formula for the cable length between a repeater and the duplexer? Thanks Don VE7EDA
Re: [Repeater-Builder] Cable formula
Sheesh. isno should have been is not. Joe M. mch wrote: The length from the repeater to the duplexer isno critical (or SHOULD not be when properly tuned). Therefore, there is no 'formula' other than you want it as short as possible yet allowing enough flex/extra that it won't get stressed. Joe M. Don Morehouse wrote: Does anyone know the formula for the cable length between a repeater and the duplexer? Thanks Don VE7EDA Yahoo! Groups Links
Re: [Repeater-Builder] Cable formula not required.
I'll third that...even though duplexers are typically reactive, if it's right, length of the cables should not be an issue. If it is, I would look at either the duplexer or the antenna/feedline. As always, put a dummy load after the duplexer and see if all is well. If it is, it's an antenna system problem. If not, it's a duplexer problem. (barring repeater internal problems...) -- Jim Barbour WD8CHL Steve S. Bosshard (NU5D) wrote: Roger, Roger, Roger.Steve NU5D mch wrote: *The length from the repeater to the duplexer is not critical (or SHOULD not be when properly tuned). Therefore, there is no 'formula' other than you want it as short as possible yet allowing enough flex/extra that it won't get stressed.* Joe M. Don Morehouse wrote: Does anyone know the formula for the cable length between a repeater and the duplexer? Thanks Don VE7EDA
Re: [Repeater-Builder] Cable formula
OK so you have a reel of cable and two connectors to make up the jumper between transmitter and duplexer. The duplexer is tuned using 50 ohm test gear and the transmitter has been optimised into a 50 ohm load. Unfortunatley the output impedance of the transmitter is not 50 ohms and a length of cable to the duplexer will transform this impedance,detuning the first can in the transmit chain. A cable length can be found that minimises this effect this length can be found more easily by measurement than by calculation. I recommend a General Radio line stretcher as your next purchase from flea market/ebay. Using the stretcher an optimum electrical length can be found and copied to jumper length using the sweeper substitution method. All of this work can be done on site using a cheap sweeper and a line stretcher. Alternativley, a ferrite isolator can be put at the can end of the run, however the original posting is not in this area and isolator losses and sag make it an unattractive option. The z matcher is another option but in my practical experience it makes the jumper radiate RF you spend all that money on RG214/RG400 double silver plated shielding and then deliberatley mismatch it? Ian Ashford G8PWE
Re: [Repeater-Builder] Cable formula
I saw that line stretcher guy, Ian. He was next to the striped tower paint salesman. 73, Steve NU5D PS - I have used an isolator in place of the TEE on the output of a duplexer. Not very practical there, though, and it sure knocks down the receive if you put it in series with the antenna, else the load gets really warm if you hook it up backwards.steve IM Ashford wrote: OK so you have a reel of cable and two connectors to make up the jumper between transmitter and duplexer. The duplexer is tuned using 50 ohm test gear and the transmitter has been optimised into a 50 ohm load. Unfortunatley the output impedance of the transmitter is not 50 ohms and a length of cable to the duplexer will transform this impedance,detuning the first can in the transmit chain. A cable length can be found that minimises this effect this length can be found more easily by measurement than by calculation. I recommend a General Radio line stretcher as your next purchase from flea market/ebay.
Re: [Repeater-Builder] Cable formula
A good quality Z-Matcher has isolation caps on the trimmer ports so I don't think the matcher itself is producing any RF radiation. I don't understand your description of the z Matcher as introducing any mismatch. The mismatch is already there as a result of some disparity between the source, load and cable impedances. All the matcher does is permit you to match the source and cable impedances. In a message dated 6/29/2007 4:40:45 P.M. Pacific Daylight Time, [EMAIL PROTECTED] writes: The z matcher is another option but in my practical experience it makes the jumper radiate RF you spend all that money on RG214/RG400 double silver plated shielding and then deliberatley mismatch it? Ian Ashford G8PWE ** See what's free at http://www.aol.com.
Re: [Repeater-Builder] cable tv hardline loss question
Pardon my previous incorrect response..I was confused. At 05:57 AM 3/21/2006, you wrote: tony dinkel wrote: Can someone estimate for me, the approximate loss of typical half inch cable TV hard line at 450 mHz? CommScope .500 (1/2 inch) P3 cable is rated at 1.56 dB per 100 feet at 68 degrees F. http://www.commscope.com/docs/td_manual_1003.pdf 75 to 50 ohm transitions can be made by following this article: http://www.repeater-builder.com/rbtip/matchingstubs.html Kevin Custer Yahoo! Groups Links Thanks, Robin Midgett K4IDC 615-322-5836 office - rolls to pager 615-835-7699 pager 615-301-1642 home [EMAIL PROTECTED] http://www.people.vanderbilt.edu/~robin.midgett/index.htm Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable tv hardline loss question
Approximately 3dB/100 feet. The 3/4 stuff is much better for 450 MHz. At 07:23 PM 3/20/2006, you wrote: Can someone estimate for me, the approximate loss of typical half inch cable TV hard line at 450 mHz? tnx td wb6mie Yahoo! Groups Links Thanks, Robin Midgett K4IDC 615-322-5836 office - rolls to pager 615-835-7699 pager 615-301-1642 home [EMAIL PROTECTED] http://www.people.vanderbilt.edu/~robin.midgett/index.htm Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable tv hardline loss question
Keep in mind that cable TV coax is 75 ohm stuff. Dick W1NMZ - Original Message - From: tony dinkel To: Repeater-Builder@yahoogroups.com Sent: 20 March, 2006 17:23 Subject: [Repeater-Builder] cable tv hardline loss question Can someone estimate for me, the approximate loss of typical half inch cable TV hard line at 450 mHz?tnxtdwb6mieYahoo! Groups Links* To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/* To unsubscribe from this group, send an email to: [EMAIL PROTECTED]* Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/ YAHOO! GROUPS LINKS Visit your group "Repeater-Builder" on the web. To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
Re: [Repeater-Builder] cable tv hardline loss question
Right... Also keep in mind that 75 ohm cable has a lesser amount of loss for the same size cable as 50 ohm. And, for receive only systems, matching isn't quite as important. And, matching transformers are easily built, for other terminal impedances. And, cabling lengths can be substituted for the stubs, for impedance matching. And, 75 ohm cable can be obtained, many times, for nothing. And, if jacketed, works in duplex service as well as any other coax. Someone wrote: Keep in mind that cable TV coax is 75 ohm stuff. YAHOO! GROUPS LINKS Visit your group "Repeater-Builder" on the web. To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
Re: [Repeater-Builder] cable tv hardline loss question
is it P1 or P3 cabletony dinkel [EMAIL PROTECTED] wrote: Can someone estimate for me, the approximate loss of typical half inch cable TV hard line at 450 mHz?tnxtdwb6mieYahoo! Groups Links* To visit your group on the web, go to:http://groups.yahoo.com/group/Repeater-Builder/* To unsubscribe from this group, send an email to:[EMAIL PROTECTED]* Your use of Yahoo! Groups is subject to:http://docs.yahoo.com/info/terms/ YAHOO! GROUPS LINKS Visit your group "Repeater-Builder" on the web. To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
RE: [Repeater-Builder] Cable
Well, I was finally able to get them ordered today... I had the guy at the county add me on to their account as a user for web browsing and ordering. Also, FYI for all you guys (or youse guys, as it is usually pronounced here in Chicago) who prefer to just call Motorola - my guy called Motorola parts on the phone and they told him they preferred that he use the web site. Looks like they're trying to go away from the phone assist/ordering. SO if you're not set-up for online ordering yet, you might want to get it set-up now. And I'm not having any luck with the manual number I got regarding the R1011A power supply... Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, March 06, 2006 2:40 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable Well, it's only metering signals, and I'm pretty sure they're DC and filtered on the receiver, so shielding is just part of the overall effort to keep RF inside the chassis. I doubt it's critical unless you're using the receiver in a situation where any leakage of any kind could be picked up and intelligence gained from it (like inside the US Embassy in Russia). Worst case, you could wrap it in aluminum foil. I don't plan on using shielded wire for mine, just some plain #22 wires. Were you able to purchase the plugs from Motorola? Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: OK, thanks for the input, Bob. I actually measured the cable I have, and it measures about 7 1/4 overall... So 6 would have been a bit short. I'm wondering just how critical the shielding is on this particular cable? I have multi-conductor cable available, but it is unshielded. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, March 06, 2006 10:54 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable You should make the cable 11-12 inches long, like the manual says. I made mine 6 inches before looking at the manual or the chassis - way too short. Now I have to take it all apart and do it all over again. #22 or #24 stranded wire is fine. Bob M. Yahoo! Groups Links [EMAIL PROTECTED] __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
After signing their license agreement and purchasing an RSS package, they offered me the on-line stuff. It was so restricted I could only access items related to that RSS package. I called and they wouldn't open it up unless I became an authorized repair service. That was the end of MOL. I now just call them and order parts. It's their nickel, and when I don't have the part number, I speak to their people who are getting paid to sit there anyway. It's just the way they seem to want to do business, and so far, except when their phone system has troubles, it's worked out just fine. Good luck on your recovery. Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: Haven't had a chance to call them yet... I spent most of the day today at the doctors (trying to get a release to go back to work after pneumonia), so that's taken a lot of my time. I was trying to get setup for Internet access, but apparently they're not real forgiving at Motorola... They asked last Friday for some info regarding the account I want to setup, and I didn't have all the answers right away - I was planning on using the county's account as the basis for my request. Anyhow - I didn't get back to them today via e-mail with answers to their questions, so they closed the account... Now I have to call them on the phone. Not very customer-friendly, are they?? Hopefully, I'm going to attempt to find time to call Motorola tomorrow - if not, then later this week. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, March 06, 2006 2:40 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable Well, it's only metering signals, and I'm pretty sure they're DC and filtered on the receiver, so shielding is just part of the overall effort to keep RF inside the chassis. I doubt it's critical unless you're using the receiver in a situation where any leakage of any kind could be picked up and intelligence gained from it (like inside the US Embassy in Russia). Worst case, you could wrap it in aluminum foil. I don't plan on using shielded wire for mine, just some plain #22 wires. Were you able to purchase the plugs from Motorola? Bob M. __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
You should make the cable 11-12 inches long, like the manual says. I made mine 6 inches before looking at the manual or the chassis - way too short. Now I have to take it all apart and do it all over again. #22 or #24 stranded wire is fine. Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: Thanks for that information, Eric! It's nice to know that the plug is still available from Motorola parts. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric Lemmon Sent: Saturday, March 04, 2006 11:32 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable Or, you could just buy the 7-pin plug from Motorola Parts. It's part #2884208B01, about $3 apiece. 73, Eric Lemmon WB6FLY __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
OK, thanks for the input, Bob. I actually measured the cable I have, and it measures about 7 1/4 overall... So 6 would have been a bit short. I'm wondering just how critical the shielding is on this particular cable? I have multi-conductor cable available, but it is unshielded. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, March 06, 2006 10:54 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable You should make the cable 11-12 inches long, like the manual says. I made mine 6 inches before looking at the manual or the chassis - way too short. Now I have to take it all apart and do it all over again. #22 or #24 stranded wire is fine. Bob M. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
Well, it's only metering signals, and I'm pretty sure they're DC and filtered on the receiver, so shielding is just part of the overall effort to keep RF inside the chassis. I doubt it's critical unless you're using the receiver in a situation where any leakage of any kind could be picked up and intelligence gained from it (like inside the US Embassy in Russia). Worst case, you could wrap it in aluminum foil. I don't plan on using shielded wire for mine, just some plain #22 wires. Were you able to purchase the plugs from Motorola? Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: OK, thanks for the input, Bob. I actually measured the cable I have, and it measures about 7 1/4 overall... So 6 would have been a bit short. I'm wondering just how critical the shielding is on this particular cable? I have multi-conductor cable available, but it is unshielded. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, March 06, 2006 10:54 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable You should make the cable 11-12 inches long, like the manual says. I made mine 6 inches before looking at the manual or the chassis - way too short. Now I have to take it all apart and do it all over again. #22 or #24 stranded wire is fine. Bob M. Yahoo! Groups Links [EMAIL PROTECTED] __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
Haven't had a chance to call them yet... I spent most of the day today at the doctors (trying to get a release to go back to work after pneumonia), so that's taken a lot of my time. I was trying to get setup for Internet access, but apparently they're not real forgiving at Motorola... They asked last Friday for some info regarding the account I want to setup, and I didn't have all the answers right away - I was planning on using the county's account as the basis for my request. Anyhow - I didn't get back to them today via e-mail with answers to their questions, so they closed the account... Now I have to call them on the phone. Not very customer-friendly, are they?? Hopefully, I'm going to attempt to find time to call Motorola tomorrow - if not, then later this week. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, March 06, 2006 2:40 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable Well, it's only metering signals, and I'm pretty sure they're DC and filtered on the receiver, so shielding is just part of the overall effort to keep RF inside the chassis. I doubt it's critical unless you're using the receiver in a situation where any leakage of any kind could be picked up and intelligence gained from it (like inside the US Embassy in Russia). Worst case, you could wrap it in aluminum foil. I don't plan on using shielded wire for mine, just some plain #22 wires. Were you able to purchase the plugs from Motorola? Bob M. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
I'm pretty sure it is straight through. I checked my manual: pins 1-5 are metering 1-5, pin 6 is NC, and pin 7 is ground. They specify some 5-conductor shielded cable, 11 inches long. I didn't make mine that long, which might be a mistake - I won't know until I try to put it into the chassis. I think those same connectors are used by the various test sets. I know I bought an entire plug and shell 30 years ago when I was working on a Micor mobile, but I don't recall how the shell was assembled to the connector body. Anyway, good luck with finding the connectors. Worst come to worst, you could use some small finishing nails, push them through a piece of wood, or drill holes in a piece of plastic and push them through, and use that. Once it's built and in place, you'll never see it again. Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: Hi, Bob. Well if the plugs are still available, that may be my only option - to build my own cables. I looked at the manual, but I don't recall whether it was stated if these were pin-for-pin straight through or what... I suppose I could take a meter to the cable I have and find out, though. :-) Thanks for the part #... Another call to the big blue M is in order on Monday. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Friday, March 03, 2006 3:28 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Cable I bought just the 7-pin plugs in July 2005 ago because I needed exactly the same cable for one of my receivers. I planned on wiring it myself. Perhaps the plugs themselves are still available; they're used on lots of Micor stuff. p/n 2884208B01. I didn't bother with the outer shells. They were under $10 each, as I recall. Looking at them now, they're rather dull and tarnished; I'll dip them in some Tarn-X before using them. You can use individual wires, but the original probably used 6-conductor shielded. I'm pretty sure pin 7 is ground and the rest are signal pins, but I can check the book. Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: I need two cables for the SpectraTAC system I'm putting together. These cables plug into the receiver board at J101 and jumper to the Receiver Interconnect Board in the receiver shelf unit. It is Motorola Part #: 30-84761G01. The cable is about 6 inches long, with a 7-pin connector on each end. The cable allows for the use of the Receiver Service Module that slides into the receiver shelf assembly. Anybody got any of these?? I really need two - for two receivers I'm putting together. They're NLA from Motorola - already checked. Thanks! Mark - N9WYS __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
You know, Bob, that's not a bad idea... The hardest thing will be making a jig for drilling the holes at the correct spacing. And I think I have some brass finishing nails around here - somewhere. Another project. One of the things I like about the hobby - I can always putter around and make whatever it is I need to get the job done! Thanks again, Bob and all... Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Saturday, March 04, 2006 5:42 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable I'm pretty sure it is straight through. I checked my manual: pins 1-5 are metering 1-5, pin 6 is NC, and pin 7 is ground. They specify some 5-conductor shielded cable, 11 inches long. I didn't make mine that long, which might be a mistake - I won't know until I try to put it into the chassis. I think those same connectors are used by the various test sets. I know I bought an entire plug and shell 30 years ago when I was working on a Micor mobile, but I don't recall how the shell was assembled to the connector body. Anyway, good luck with finding the connectors. Worst come to worst, you could use some small finishing nails, push them through a piece of wood, or drill holes in a piece of plastic and push them through, and use that. Once it's built and in place, you'll never see it again. Bob M. == Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
Or, you could just buy the 7-pin plug from Motorola Parts. It's part #2884208B01, about $3 apiece. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of N9WYS Sent: Saturday, March 04, 2006 8:52 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable You know, Bob, that's not a bad idea... The hardest thing will be making a jig for drilling the holes at the correct spacing. And I think I have some brass finishing nails around here - somewhere. Another project. One of the things I like about the hobby - I can always putter around and make whatever it is I need to get the job done! Thanks again, Bob and all... Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Saturday, March 04, 2006 5:42 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable I'm pretty sure it is straight through. I checked my manual: pins 1-5 are metering 1-5, pin 6 is NC, and pin 7 is ground. They specify some 5-conductor shielded cable, 11 inches long. I didn't make mine that long, which might be a mistake - I won't know until I try to put it into the chassis. I think those same connectors are used by the various test sets. I know I bought an entire plug and shell 30 years ago when I was working on a Micor mobile, but I don't recall how the shell was assembled to the connector body. Anyway, good luck with finding the connectors. Worst come to worst, you could use some small finishing nails, push them through a piece of wood, or drill holes in a piece of plastic and push them through, and use that. Once it's built and in place, you'll never see it again. Bob M. == Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
Thanks for that information, Eric! It's nice to know that the plug is still available from Motorola parts. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric Lemmon Sent: Saturday, March 04, 2006 11:32 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Cable Or, you could just buy the 7-pin plug from Motorola Parts. It's part #2884208B01, about $3 apiece. 73, Eric Lemmon WB6FLY Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Cable
I bought just the 7-pin plugs in July 2005 ago because I needed exactly the same cable for one of my receivers. I planned on wiring it myself. Perhaps the plugs themselves are still available; they're used on lots of Micor stuff. p/n 2884208B01. I didn't bother with the outer shells. They were under $10 each, as I recall. Looking at them now, they're rather dull and tarnished; I'll dip them in some Tarn-X before using them. You can use individual wires, but the original probably used 6-conductor shielded. I'm pretty sure pin 7 is ground and the rest are signal pins, but I can check the book. Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: I need two cables for the SpectraTAC system I'm putting together. These cables plug into the receiver board at J101 and jumper to the Receiver Interconnect Board in the receiver shelf unit. It is Motorola Part #: 30-84761G01. The cable is about 6 inches long, with a 7-pin connector on each end. The cable allows for the use of the Receiver Service Module that slides into the receiver shelf assembly. Anybody got any of these?? I really need two - for two receivers I'm putting together. They're NLA from Motorola - already checked. Thanks! Mark - N9WYS __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Cable
Hi, Bob. Well if the plugs are still available, that may be my only option - to build my own cables. I looked at the manual, but I don't recall whether it was stated if these were pin-for-pin straight through or what... I suppose I could take a meter to the cable I have and find out, though. :-) Thanks for the part #... Another call to the big blue M is in order on Monday. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Friday, March 03, 2006 3:28 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Cable I bought just the 7-pin plugs in July 2005 ago because I needed exactly the same cable for one of my receivers. I planned on wiring it myself. Perhaps the plugs themselves are still available; they're used on lots of Micor stuff. p/n 2884208B01. I didn't bother with the outer shells. They were under $10 each, as I recall. Looking at them now, they're rather dull and tarnished; I'll dip them in some Tarn-X before using them. You can use individual wires, but the original probably used 6-conductor shielded. I'm pretty sure pin 7 is ground and the rest are signal pins, but I can check the book. Bob M. == --- N9WYS [EMAIL PROTECTED] wrote: I need two cables for the SpectraTAC system I'm putting together. These cables plug into the receiver board at J101 and jumper to the Receiver Interconnect Board in the receiver shelf unit. It is Motorola Part #: 30-84761G01. The cable is about 6 inches long, with a 7-pin connector on each end. The cable allows for the use of the Receiver Service Module that slides into the receiver shelf assembly. Anybody got any of these?? I really need two - for two receivers I'm putting together. They're NLA from Motorola - already checked. Thanks! Mark - N9WYS Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] cable length
I thank you for the response .I don't usually set the TX cable at one length andit varies at all my sites .most of the sites may be around aprox 1 meteror so
Thank You,
Ian Wells,
Kerinvale Comaudio,
www.kerinvalecomaudio.com.au
---Original Message---
From: Eric Lemmon
Date: 01/24/06 15:06:34
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] cable length
Ian,
The cable length is more important on the TX side than on the RX side. However, since the impedances of the power amplifier output and of the duplexer TX input are seldom known with any certainty, it is impossible to know in advance what length that jumper cable should be. The TX jumper cable acts as a linear impedance transformer, depending upon its length in relation to the wavelength of the TX carrier. The chances that any random length of cable will result in a perfect match are slim.
The method I use is to make up a cable that fits the installation neatly, and then measure the power going to the antenna from the duplexer with a Bird wattmeter. Then I install an impedance matcher ("Z-matcher") at the output of the PA. If tuning the Z-matcher makes a significant improvement in the forward power, I know that the jumper cable is probably not the ideal length. I now have two choices: I can start experimenting with longer and shorter cables until I find the optimum length, or I can set the Z-matcher for the optimum setting and close up the cabinet, turn out the lights, and head home. Opinions vary greatly on this issue...
73, Eric Lemmon WB6FLY
From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ian WellsSent: Monday, January 23, 2006 4:34 PMTo: Repeater-Builder@yahoogroups.comSubject: [Norton AntiSpam] [Repeater-Builder] cable length
Is it nessary to have the correct length coax from the diplexer to the rx and tx or is there a formular that can show the correct length .I am currently using RG223 coax for these links
Thank You,
Ian Wells,
Kerinvale Comaudio,
www.kerinvalecomaudio.com.au
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RE: [Repeater-Builder] cable length
I keep hearing about these "Z-Matchers". Who makes them, and are they expensive?
LJ
-Original Message- From: Eric Lemmon <[EMAIL PROTECTED]>Sent: Jan 23, 2006 9:06 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] cable length
Ian,
The cable length is more important on the TX side than on the RX side. However, since the impedances of the power amplifier output and of the duplexer TX input are seldom known with any certainty, it is impossible to know in advance what length that jumper cable should be. The TX jumper cable acts as a linear impedance transformer, depending upon its length in relation to the wavelength of the TX carrier. The chances that any random length of cable will result in a perfect match are slim.
The method I use is to make up a cable that fits the installation neatly, and then measure the power going to the antenna from the duplexer with a Bird wattmeter. Then I install an impedance matcher ("Z-matcher") at the output of the PA. If tuning the Z-matcher makes a significant improvement in the forward power, I know that the jumper cable is probably not the ideal length. I now have two choices: I can start experimenting with longer and shorter cables until I find the optimum length, or I can set the Z-matcher for the optimum setting and close up the cabinet, turn out the lights, and head home. Opinions vary greatly on this issue...
73, Eric Lemmon WB6FLY
From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ian WellsSent: Monday, January 23, 2006 4:34 PMTo: Repeater-Builder@yahoogroups.comSubject: [Norton AntiSpam] [Repeater-Builder] cable length
Is it nessary to have the correct length coax from the diplexer to the rx and tx or is there a formular that can show the correct length .I am currently using RG223 coax for these links
Thank You,
Ian Wells,
Kerinvale Comaudio,
www.kerinvalecomaudio.com.au
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Re: [Repeater-Builder] cable TV ground rods
Someone correct me if I am wrong but grounding the cable system to the AC panel ground is a National Electrical Code requirement. Neil - WA6KLA Chuck Kelsey wrote: The cable guys around here don't put in ground rods. They bond to the existing electrical ground system. Chuck WB2EDV Someone please tell the cable guys to stop putting in the 4ft rods and creating ground loops! ;) Tom W9SRV *//* Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable TV ground rods
The cable guys around here don't put in ground rods. They bond to the existing electrical ground system. Chuck WB2EDV Someone please tell the cable guys to stop putting in the 4ft rods and creating ground loops! ;) Tom W9SRV *//* Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
This is what happens when the a customer who knows nothing about radio, wants something cheep, buys low bid from someone who is out for a fast buck and the customer who is probably an administrator, is unwilling to admit that they made a mistake! All they had to do is write a performance guarantee into the purchase or specification with a penalty for non-performance. Fred W5VAY - Original Message - From: Jim B. [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, March 16, 2005 8:27 AM Subject: Re: [Repeater-Builder] cable run radiating cable Bob Dengler wrote: At 3/15/2005 01:48 PM, you wrote: what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof. On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. The answer that was proposed for one local hospital was to put the whole mess on a middle floor, with 3dB stick just outside. But because another cut-throat shop came in and bid a used flexar rptr, and said it would work just fine on an existing antenna on the roof, they went that way. Oh, while the rptr was UHF, the antenna they used was a VHF 4-bay. It was resonant. Didn't work for beans in the hospital, worked good about 10-12 mi away though. The antenna and rptr have since been replaced, but it still doesn't work all that well. -- Jim Barbour WD8CHL Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
At 08:02 PM 3/15/2005 -0500, you wrote: Then, there's convincing your in-house electrician that it DOESNT need to be in conduit... ;-) Good Luck. Plenum fire rated cable should be used. Joe Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
Bob Dengler wrote: At 3/15/2005 01:48 PM, you wrote: what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof. On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. The answer that was proposed for one local hospital was to put the whole mess on a middle floor, with 3dB stick just outside. But because another cut-throat shop came in and bid a used flexar rptr, and said it would work just fine on an existing antenna on the roof, they went that way. Oh, while the rptr was UHF, the antenna they used was a VHF 4-bay. It was resonant. Didn't work for beans in the hospital, worked good about 10-12 mi away though. The antenna and rptr have since been replaced, but it still doesn't work all that well. -- Jim Barbour WD8CHL Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
At 05:20 AM 3/16/05, you wrote: At 08:02 PM 3/15/2005 -0500, you wrote: Then, there's convincing your in-house electrician that it DOESNT need to be in conduit... ;-) Good Luck. Plenum fire rated cable should be used. Joe That was the story. Years ago DB made a big batch of cable for an install in multiple tall buildings in downtown L.A. If you looked up the part number in the catalog it stated that it was plenum rated cable but because the physical cable didn't have the word plenum painted on the side next to the part number every few feet then it obviously wasn't plenum rated. This objection was made AFTER it was hung in a 30-plus story building, tested (swept), and placed in use. I do not know the rest of the story... it may have had to be replaced, or it may have been accepted in place. The story did include the fact that multiple phone calls and faxes (including statements of compliance) went back and forth and that the DB folks offered to send someone out, swing them from a bosun's chair in the elevator shaft, and stencil Plenum on the cable every three feet. Multiple folks were supposed to have made comments that the stubborn inspector (other less polite words were used) could read what wasn't on the cable, but could not read the words plenum rated in the DB catalog. The point is, do your planning such that everybody is satisfied in advance. Mike WA6ILQ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
Hey John, You mite write to Dean Westbrook. He has done two subway systems using this Hard-Line type of coax and they even sent him to school on it. Neat stuff to use from the story I heard. I am not sure how close he is monitoring the list over there. They are closing out a very large job. 73, Russ - Original Message - From: Maire Company To: Repeater-Builder@yahoogroups.com Sent: Tuesday, March 15, 2005 4:48 PM Subject: [Repeater-Builder] cable run radiating cable what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof.On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. Or any other thoughts would help. John Yahoo! Groups Links To visit your group on the web, go to:http://groups.yahoo.com/group/Repeater-Builder/ To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
Re: [Repeater-Builder] cable run radiating cable
Local hospital where I have our 2mtr repeater, uses a single folded dipole, mounted horizontal to transmit straight down into the hospital for their security people. they are also on 154.mhz. It works for them. N3FLR - Frank Maire Company wrote: what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof. On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. Or any other thoughts would help. John *Yahoo! Groups Links* * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service http://docs.yahoo.com/info/terms/. No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.3 - Release Date: 3/15/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.3 - Release Date: 3/15/2005 Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
.. never have understood what folks who sell those setups are thinking... besides $$... Big power big antennas on the 15th floor -- and when the pager won't trip in the basement X-ray room, it's a mystery... must need a bigger antenna... Sheeesh.. You're on the right track thinking Radiax or such -- for 80-odd feet, 1/2 or 3/4 should do fine. A good leaky coax setup is part science, part magic, and a healthy dose of common sense and PLANNING -- if there's no need for significant coverage away from the building, drop a line ~down~ from the current station, terminated with a simple 1/4 GP at the bottom. (Load? Don't want no stinkin' Load !) Elevator shafts are perfect *IF* your zoning/fire-code will allow (and most places WONT). Look to centrally located pipe-chase service riser stacks -- maintain some spacing from 'big-iron', and (excuse the shouting) _USE_THE_PROPER_HANGERS_ recommended spacing so the cable isn't damaged. Andrew docs are very good references. Then, there's convincing your in-house electrician that it DOESNT need to be in conduit... ;-) Good Luck. Maire Company wrote: what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof. On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
At 3/15/2005 01:48 PM, you wrote: what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof. On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. I have a UHF repeater on a 40+ story building. While not solid, it is HT-accessible from the bottom sub-basement, 4 stories below ground level. Antenna is a GP9 only; no radiax. My guess is that the signal is rattling around between buildings (there are several highrises around it that are the same height a couple that are taller) bouncing back in from the outside. If it's an option, consider locating your repeater to an adjacent building directing the RF into your building from the side rather than the top. Bob NO6B Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
At 01:48 PM 3/15/05, you wrote: what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof. On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. Or any other thoughts would help. John Several office buildings in downtown Los Angeles are using that exact system, with DC remotes from the radio cabinet to a telephone set style remote at the guard desk. The antenna on the roof provides coverage for a short distance around the building and the Radiax (that is in one of the elevator shafts) gives saturation coverage in the building. If you end up installing Radiax USE THE PROPER HANGERS... and it's up to you to convince the fire inspector and the building maintenance folks that it DOESN'T go in conduit... there's a story behind that... An alternative method that I saw a hospital in a air conditioning building on the roof: A Motorola PURC (900MHZ Micor based) paging system TX fed a power divider - of a type I had never seen before - was an aluminum block the size of a red brick, with three ports, one labeled TX, the second labeled ANT-1, and the third labeled ANT-2, with stenciled text on the side... BIRD 900MHz power divider 75% to ANT1 25% to ANT2 The ANT1 feedline fed a super stationmaster on a 10 foot mast on a tripod mount. ANT2 was a 6 element beam pointed straight down into the building. The pagers worked even in the sub-basement x-ray room. Mike WA6ILQ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
John, If your intention is to cover the building interior, do not install any rooftop antenna. Use Radiax or similar leaky cable vertically through every floor. You should use a central vertical chase, such as an elevator shaft, being careful to keep the cable well away from parallel metal rails or HVAC ducting. This cable must be plenum rated, since it must NOT be installed in conduit, and there are strict rules on vertical cables in elevator shafts and chases. Be prepared to deal with fire inspectors and other bureaucrats who are clueless about radio- but treat them kindly, for they probably are really looking for a safe installation. Above all, read the Radiax installation instructions carefully, and follow them to the letter. Radiax performs admirably when installed correctly, but it will fail miserably if installed with makeshift hangers. 73, Eric Lemmon WB6FLY Maire Company wrote: what do you guys know about the installation of radiating cable for a repeater in a building. I have a 5 story building and sub basement. So it is like 6 stories. Thinking of putting the repeater in the lower level and installing the cable up to the roof. On the roof thinking a DB-408. (or would a dummy load be used) This would be a UHF repeater possible 2 watts or other low power use. The goal is to cover the floors as there are a lot of cement and metal. At this time they have a repeater on the roof but the lower floors are dead and there is very little receive in the sub basement. The current repeater is 40 watts. No preamp. Or any other thoughts would help. John --- Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable run radiating cable
I have to agree I work in a hospital and rf coverage from in house system is not the greatest, radiax is a good option, but remote receivers a voter is also good option. The hospital IT department should be able to supply some of the wire runs to tie the remote's in to the repeater. With many of the newer phone systems being digital I have seen that a lot of the older wire pairs are just abandoned and may be avaliable especially if it saves them money. good luck bob ___ Speed up your surfing with Juno SpeedBand. Now includes pop-up blocker! Only $14.95/month -visit http://www.juno.com/surf to sign up today! Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable question
RG-214/U Mil Spec. (make damn sure is silver plated, not nickel) The Mil Spec *should* assure that. Kevin Brent wrote: which would perform better to replace the cable between the duplexers and repeater RG-393 RG-400 RG-316 Thanks Brent Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] cable question
RG-214/U SILVER got it thanks Kevin Brent - Original Message - From: Kevin Custer [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Friday, March 04, 2005 9:01 PM Subject: Re: [Repeater-Builder] cable question RG-214/U Mil Spec. (make damn sure is silver plated, not nickel) The Mil Spec *should* assure that. Kevin Brent wrote: which would perform better to replace the cable between the duplexers and repeater RG-393 RG-400 RG-316 Thanks Brent Yahoo! Groups Links --- [This E-mail scanned for viruses at TNWEB LLC] -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 266.6.0 - Release Date: 3/2/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 266.6.0 - Release Date: 3/2/2005 --- [This E-mail scanned for viruses at TNWEB LLC] Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Cable on DB4001-1 Length
Mathew, Yes, and possibly. Perhaps Decibel Products Tech Support can advise you on the correct jumper length for a DB4001-2 filter, which is two DB4001-1 cavities in series. Adjust all four coupling loops for optimum return loss at the receive frequency and a total insertion loss of 1.0 dB. The jumper between the duplexer's RX output and the input to the first bandpass cavity should be approximately 1/2 wavelength, inclusive of the lengths of the coupling loops within the cavities at each end. Before getting wrapped around the axle on this, first try using a cable that is the same length as the jumpers on the RX side of the duplexer. You might get lucky with a random length, and if it works okay... 73, Eric Lemmon WB6FLY w9mwq wrote: I am going to use two of the Decibel Products DB-4001-1 Filters on the receive side of my repeater once I connect a preamp this week. What I need to know is, is there a certain length the cable has to be between the two cavities that connects them together as well as between the preamp and the filters? Mathew Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
