Re: [Repeater-Builder] Re: subaudibe tones..
On Aug 28, 2007, at 10:29 PM, [EMAIL PROTECTED] wrote: At 8/28/2007 16:01, you wrote: Bob Dengler wrote: One concept that really helps in this area is CTCSS tone frequency standardization, IOW tones by region. All you then need to know is the freq. being used in the area you're traveling to. Many areas are already well established: 110.9 in Rochester NY, 107.2 in Niagara Falls San Diego, 131.8 in Santa Barbara, 127.3 in Springfield MA. Even if you don't know what tone is in use, all you have to do is find the tone of one system. After that you can find the others by kerchunking (with ID of course!) all the other pairs with that tone. Bob NO6B It seems to me that if you have all the repeaters in an area running the same CTCSS tone, and start fighting a mixing problem... everything is going to be back to keying everything else in short order. This gets us back to the CTCSS-bandaid issue. If your ham TXs are IMDing with each other landing back on your inputs, you need to fix it. The only IMD problems I've had linger on my systems were caused by non-amateur TXs. If amateur TXs were involved, we found the actual source of the problem fixed it. Ahh, but the reality is... all hams operating repeaters aren't created equal. If you push that all repeaters in an area run the same tone, and then some doofus comes along and his lashed up mess of a couple of mobiles and a mobile duplexer hooked up with RG-8X and it starts opening itself... he's just as likely to blame it on that big club repeater on the other leg of the tower than on his own ineptitude. If you're on a completely different CTCSS tone than Barney Fife there, he has no case and he'll go hunting elsewhere, without any bullets. :-) -- Nate Duehr, WY0X [EMAIL PROTECTED]
Re: [Repeater-Builder] Re: ltr repeater system
I think I have had enough ESAS for one natural lifetime. Actually, except for the remote computers locking up, and loosing track of circuit index, the stuff actually worked pretty well. Had it roaming, multisite dispatch, etc. Used Multitech VOIP equipment to tie sites together and remote print servers for RS232 links. When it worked it worked well. Got tired of having to go to sites for hard reset. Watch dog timers would not hunt ! Steve Tom Parker wrote: Try to buy a Trident Raider book... $35 hardly buys the postage... Also, home channel needs to be FB8 if at all possible. Steve, want to buy some more Uniden ESAS switches? We have four sites of six channels each! thp skipp025 wrote: Hi Mike, Nothing wrong with the way most Zetron Products work. My beef with Zetron is how they dropped all support after 5 years on some high end Zetron Products I have here. Then they tried to charge me $35 f No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.10/977 - Release Date: 8/28/2007 4:29 PM
[Repeater-Builder] Re: The T list
I typed in the stuff below in answer to a question on another list. Then I figured that the folks on this list might like to have it for their file cabinets. When I get time I'll put a web page wrapper around it. I've also got the info on the part number prefix - like why a 36- part is a knob, why a 41- is a spring and a 66 is a tool. But that is going to be a lot of typing and I've got to be out of my house in a few weeks. Mike WA6ILQ At 07:27 AM 08/27/07, you wrote: Howdy Folks, Has there been a list of the T designations posted anywhere? I haven't figured out any rhyme or reason to the ones on my equipment...I'm sure there's some logic there somewhere. TLN- for example. Thanks, Lar K2JIA This is from a 1960s Mot Buyers Guide - as far as I know it disappeared after 1969, and was never published again. My library has three buyers guides from around 1962, 1965 and 1969. Things have changed in this numbering plan since the 60s but a lot of it is still accurate. 1st letter T=two-way radio product (i.e. Illinois plants) N=Portable product (i.e. Florida plants) S=Test Equipment, CCTV, traffic light equipment and other special products 2nd letter A=antenna related but not duplexers, filters or feedline B=boxes or packaging kits (mostly used internally) C=control equipment (control heads, control panels, etc) D=drop ship items (i.e. stuff manufactured outside Moto, and shipped from the OEM plant to the end customer) E=service kits and conversion kits F=filters and duplexers G=panels (mostly metering panels) H=housings and cabinets J=coil kits K=cable kits L=misc non-categorized items M=Microphones P=power supplies and power supply related equipment R=receivers and receiver related S=speakers, earphones, and related T=transmitters U=unified chassis Other letters have been assigned since this list was printed in the 1960s. 3rd letter A= under 25mhz B=25-54 Mhz (yes, the buyers guide included 6m) C=72-76 Mhz (see note) D=144-174 Mhz E=400-470 Mhz (see note) F=890-960 Mhz N=not frequency dependent (like an audio-squelch board) (see note) C=was limited to the 72-76 USA assignment (one split) until the UK needed equipment for 66-89mhz land mobile in the early 70s, then it was widened to 66 to 88MHz. Some books say 60-99. In the USA the 60-66MHz range is television channel 3, the 66-72MHz range is TV channel 4, the 72-76MHz frequencies are used as Operational Fixed / Repeater frequencies (essentially commercial point-to-point links), 76-82MHz is TV channel 5, 82-88MHz is TV channel 6, and 88-108MHz is commercial FM broadcast. E was redefined downwards to 370mhz for certain military and spook equipment in the early 70s, and upwards to 490 and later to 512 as those frequencies were allocated. N is still used as not frequency sensitive even when there is some differences between wideband and narrowband equipment (like in the audio recovery circuitry in an low-IF / discriminator board). The numbers after the three letters are simply a design sequence number. One or two letters after the numbers are variations / revisions. Mike WA6ILQ
Re: [Repeater-Builder] Re: ltr repeater system
Last I'll say about it... we bought the stuff out of the Nextel Abilene warehouse (we're also in Texas) for our SMRS systems about a year before Relm pulled the plug on Uniden. Dennis tried to help in the beginning but in the end, it was a good idea, that never fully came to fruition and is long past it's prime... kinda like some of us I guess (grin) I just had to ask however... thp Steve S. Bosshard (NU5D) wrote: I think I have had enough ESAS for one natural lifetime. Actually, except for the remote computers locking up, and loosing track of circuit index, the stuff actually worked pretty well. Had it roaming, multisite dispatch, etc. Used Multitech VOIP equipment to tie sites together and remote print servers for RS232 links. When it worked it worked well. Got tired of having to go to sites for hard reset. Watch dog timers would not hunt ! Steve Tom Parker wrote: Try to buy a Trident Raider book... $35 hardly buys the postage... Also, home channel needs to be FB8 if at all possible. Steve, want to buy some more Uniden ESAS switches? We have four sites of six channels each! thp skipp025 wrote: Hi Mike, Nothing wrong with the way most Zetron Products work. My beef with Zetron is how they dropped all support after 5 years on some high end Zetron Products I have here. Then they tried to charge me $35 f -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.10/977 - Release Date: 8/28/2007 4:29 PM No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.10/977 - Release Date: 8/28/2007 4:29 PM
Re: Re: [Repeater-Builder] Re: subaudibe tones..
Nate all, Tone can be good for most, but not needed everywhere. Our FL council now requires tone decode/encode (same freq) on ALL repeaters here. About 15 years back the council did give suggested tone freq (here 146.2) for all parts of FL. The one mistake was they assigned 100 Hz to one area and as most know 100 Hz had been used to allow repeaters to put tone on without closing...kinda a universal tone. Now those that do it have problems with other areas. I think the powers to be think they know more than they do. Most of the time when things like this is mandated it is from a few who really are narrow minded. The best results comes from the repeater builder, not owners or clubs or trustees, but the ones who get in the mud and do the work. 73, ron, n9ee/r ps, my repeater is not toned. From: Nate Duehr [EMAIL PROTECTED] Date: 2007/08/29 Wed AM 01:08:58 CDT To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: subaudibe tones.. On Aug 28, 2007, at 10:29 PM, [EMAIL PROTECTED] wrote: At 8/28/2007 16:01, you wrote: Bob Dengler wrote: One concept that really helps in this area is CTCSS tone frequency standardization, IOW tones by region. All you then need to know is the freq. being used in the area you're traveling to. Many areas are already well established: 110.9 in Rochester NY, 107.2 in Niagara Falls San Diego, 131.8 in Santa Barbara, 127.3 in Springfield MA. Even if you don't know what tone is in use, all you have to do is find the tone of one system. After that you can find the others by kerchunking (with ID of course!) all the other pairs with that tone. Bob NO6B It seems to me that if you have all the repeaters in an area running the same CTCSS tone, and start fighting a mixing problem... everything is going to be back to keying everything else in short order. This gets us back to the CTCSS-bandaid issue. If your ham TXs are IMDing with each other landing back on your inputs, you need to fix it. The only IMD problems I've had linger on my systems were caused by non-amateur TXs. If amateur TXs were involved, we found the actual source of the problem fixed it. Ahh, but the reality is... all hams operating repeaters aren't created equal. If you push that all repeaters in an area run the same tone, and then some doofus comes along and his lashed up mess of a couple of mobiles and a mobile duplexer hooked up with RG-8X and it starts opening itself... he's just as likely to blame it on that big club repeater on the other leg of the tower than on his own ineptitude. If you're on a completely different CTCSS tone than Barney Fife there, he has no case and he'll go hunting elsewhere, without any bullets. :-) -- Nate Duehr, WY0X [EMAIL PROTECTED] Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
[Repeater-Builder] Re: LTR Rocks !
512 MHz and down to 136 or whatever will all be narrowband by 2013 anyway, except I haven't seen provisions for it for part 95 (GMRS) yet, so it will likely be exempt. And you will see a glut of surplus wideband commercial equip on the market around then. I have already been informed by a comm tech for one of the major class I railroads that they will have a couple of thousand radios both mobile and ht's that will be surplused. They are in the process of starting that now. I just hope I can get my hands on a few more of them. Kerry KE5OFO
[Repeater-Builder] PURC 5000 question
Hello, Can anybody direct me on how to get a Motorola PURC 5000 900MHz transmitter on 927? It is currently on 931. Also, what would be ideal for a receiver? It is only the transmitter. I'm thinking a spectra or maxtrac. Thanks for the help. -David
Re: Re: [Repeater-Builder] Re: subaudibe tones..
Since so many Ham repeaters are on sites free and at the blessing of 2-way companies or gov services, etc often when one does find an intermod or other interferring problem one just has to live with it. Trying to go to a site administrator and require one of his paying customers fix a problem, which is often not illegal in nature, is received with well you don't like the site move. Also if you become a pain they will do the moving for you. I've seen Hams try to command issues thinking they are in control because they have a piece of paper from the federal government. It is good to find the problem yourself, but fixing the problem is another issue. Tone is a good fix for some of these. 73, ron, n9ee/r From: [EMAIL PROTECTED] Date: 2007/08/28 Tue PM 11:29:35 CDT To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: subaudibe tones.. At 8/28/2007 16:01, you wrote: Bob Dengler wrote: One concept that really helps in this area is CTCSS tone frequency standardization, IOW tones by region. All you then need to know is the freq. being used in the area you're traveling to. Many areas are already well established: 110.9 in Rochester NY, 107.2 in Niagara Falls San Diego, 131.8 in Santa Barbara, 127.3 in Springfield MA. Even if you don't know what tone is in use, all you have to do is find the tone of one system. After that you can find the others by kerchunking (with ID of course!) all the other pairs with that tone. Bob NO6B It seems to me that if you have all the repeaters in an area running the same CTCSS tone, and start fighting a mixing problem... everything is going to be back to keying everything else in short order. This gets us back to the CTCSS-bandaid issue. If your ham TXs are IMDing with each other landing back on your inputs, you need to fix it. The only IMD problems I've had linger on my systems were caused by non-amateur TXs. If amateur TXs were involved, we found the actual source of the problem fixed it. Bob NO6B Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: RE: [Repeater-Builder] Duplexers
Jeff, I have Reflections II. Walt does good job explaining transmission lines. The only problem I had was all the complaining he did about other authors and articles. Some was good, but seemed to get carried away times, hi. I think the book is $19.95. One of the Ham mag has it, think CQ or World Radio...def not QST. 73, ron, n9ee/r From: Jeff DePolo [EMAIL PROTECTED] Date: 2007/08/27 Mon PM 05:11:42 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers As a side note for this discussion, I think Jeff's doing a great job of explaining how transmission line theory works... I try... For those that want to dive in a lot further (e.g. Do the math), the ARRL Antenna Book has a whole section dedicated to this topic, and it's written well enough that a mathematical dolt like myself can still follow the concepts and not scratch my head at the math. Another good, readily-available book is Reflections by Walt Maxwell W2DU. My copy is old; he put out an updated edition Reflections II later. It's a good read, but has one drawback (to me anyway). A lot of what he discusses relates to pi matching networks common in tube HF rigs. You have to keep in mind that a lot of the myths he dispels don't always translate directly to the world of VHF/UHF solid state amplifiers, but theory behind what he preaches is dead nuts on. --- Jeff Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
[Repeater-Builder] Re: [AR902Mhz Repeater-Builder] PURC 5000 questions
There are several controllers used with PURC5000 equipment. We'd need the station model number or some other description of the control unit to go further. One uses an EPROM that's programmed with an R-1801 suitcase programmer. Another uses a PC and RIB and the appropriate RSS software. A third has an actual numeric keypad on the front panel, but it's usually locked so it can't easily be changed. Either a password or flipping a DIP switch inside the unit would be necessary to allow frequency programming. 900 MHz Spectras have a 935-941 MHz filter in the receiver's front end. They will not receive well, if at all, at 902 MHz. There are no inexpensive filters you could buy to expand the range. There probably aren't any expensive filters available either. 900 MHz MaxTracs have similar front end filters, but these can be replaced with 915 MHz units that have a +/- 13 MHz bandwidth. Some other work would be necessary to get the radio to receive 902 MHz. 800 MHz MaxTracs are inexpensive. Replace the front end filters and it makes an excellent 902 MHz receiver. See the articles on www.repeater-builder.com in the Motorola MaxTrac and Motorola Spectra sections. Bob M. == --- radionut45 [EMAIL PROTECTED] wrote: Hello, Can anybody direct me on how to get a Motorola PURC 5000 900MHz transmitter on 927? It is currently on 931. Also, what would be ideal for a receiver? It is only the transmitter. I'm thinking a spectra or maxtrac. Thanks for the help. -David Moody friends. Drama queens. Your life? Nope! - their life, your story. Play Sims Stories at Yahoo! Games. http://sims.yahoo.com/
Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
From: Jeff DePolo [EMAIL PROTECTED] Date: 2007/08/27 Mon PM 01:57:13 CDT There's a capacitor hidden in in my coax? Where? I can't find it, and now I've ruined my cable looking for it :-) Yep, whenever one has two conductors with spacing between them you got a cap. For a cap in coax might try looking for the conductors of center and shield...looks like 2 conductors seperated to me, hi. Yep there are caps in that coax. That is what makes a feedline...parrallel caps and series inductors. They determine the coax or any other feedline characterist impedance. 73, ron, n9ee/r Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] Re: subaudibe tones..
I think I still have one of the Heathkit DTMF mikes with the 555s. Heath had so many problems with it drifting due to wide temp ranges and aging they eventually discontinued it. Also since the 555 had square wave output its low group tones harmonic would get into high group tones interfering with decoding. Lots of filtering was needed. A 555 is dependent on an RC network for its freq of operation. When tight specs are needed such as in CTCSS or DTMF encoding the 555 even with low coeff caps and resistors it still has problems. Of course now there are many other choices. The 555 is still useful in many applications, but ones requiring tight freq stability are not one of them. 73, ron, n9ee/r From: skipp025 [EMAIL PROTECTED] Date: 2007/08/28 Tue AM 11:13:58 CDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: subaudibe tones.. Per the 555 Timer Chip Data Sheet Operation Description: The 555 operational time values depends mostly on the ratio of voltage set-points and remains relatively free from most of the typical issues experienced with external rc networks and feedback type oscillators. Before there was really low cost crystal referenced tone generators there was a number of both well done 555 DTMF and 555 CTCSS tone generation circuits that worked without a hitch. 555 output Square waves should look just fine when filtered for audio at the end of a simple low cost rc network. Working 555 examples include the ctcss generator shown on the sonic web page. The Heathkit DTMF mic available with their early 2-meter kit radios. The gazillion made Heathkit Code Practice Oscillators. One nice thing about the 555 chip is the available output easily drives low impedance loads quite well. Also makes a nice oscillator to generate voltages independent of the package supply. Some 70's vintage radios used the 555 chip to generate a negative rail supply for those early eprom, prom and op-amp circuits. Quite the problem solving work-horse device and it has a practical use as a pretty good audio oscillator. cheers, s. The 555 has been used for many timer applications. However, it timing is controlled with and RC network and these are difficult to keep within any tight accuracy like that of DTMF encoding. Besides there are plenty of xtal controlled devices for this. And as you said the output is a square wave, not always desirable for audio. However, does make a pretty clock for digital circuits. There are many applications the 555 can be used for. 73, ron, n9ee/r From: skipp025 [EMAIL PROTECTED] Date: 2007/08/28 Tue AM 06:27:32 CDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: subaudibe tones.. W.r.t. early homebrew encoders, I never really liked the 555 version because of the non-sinewave output. Since the encoder need to cover more than an octave, fixed filtering of any kind couldn't be used to clean it up. You can find the 555 used as a pretty good tone generator in many a circuit, including a fair number of dtmf pads. If you look at the circuit on the sonic web page you'll notice the low pass filter, which works pretty well. Even with the values shown I found the described circuit puts out a lot more audio than required for a typical radio so after all the filtering you still had a high value resistor in series to knock the level down. So I went with the XR2206 function generator which put out a nice clean sine wave. Only other problem was frequency stability: Advantage to the 555, which by nature of design and operation is relatively immune to voltage and temp drift with more than a reasonable amount of change. only many years later after spending much time effort looking for the most stable Rs Cs did I discover when trying to build a 1000 Hz sine generator that the chip temperature affects the operating frequency. Never had much of a a problem with the 555 and the circuit is dirt cheap to build. cheers, s. Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: Re: [Repeater-Builder] duplexer design
Vikash, The typical design is use of coax or hard constructed coax...using large 6 or so pipes with interconductor. Normally we call these duplexers. They often have 1/4 wave length lengths being open at one end so they will look like short at source end producing a notch. But an open at the pass freq. The reason for large pipe type construction is to reduce the R so the Q will be high and allow the pass and notch freqs to be close together. There are many designs and sources for what you are talking about. They go back over 50 years and are still being built today. If you go to www.tessco.com you can see products from a number of manufactures with the specs. One has to look at what one wants...freq spacing and the amount of notch/filtering and pass attenuation. 73, ron, n9ee/r From: sms mms [EMAIL PROTECTED] Date: 2007/08/26 Sun AM 09:00:13 CDT To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] duplexer design I require the value of insertion loss on both frequencies. I have to design band reject type duplexer,please suggest the design. I will be grateful. vikash Ron Wright [EMAIL PROTECTED] wrote: Sounds as if you are designing a duplexer with coils and caps. It is often this approach will not have a high enough Q to have a notch at one freq and at the same time pass freq with low enough insertion loss. Normally duplexers use cavities which are made from coax made from heavy metal tubes, inter and outer conductors. Not your typical coax, but follow the same format. You may have the notch on both frequencies, but what is the insertion loss at the desired pass freq. 73, ron, n9ee/r From: sms mms [EMAIL PROTECTED] Date: 2007/08/24 Fri PM 12:11:46 CDT To: repeater repeater-builder@yahoogroups.com Subject: [Repeater-Builder] duplexer design Dear all, I am Vikash Gupta from India. I am designing a duplexer having low frequency:230 MHz, High gfreuqency: 234 MHz. I am usingà coil with 8 no. of turnsà and 22 PF capacitor. I have to get Insertion loss 1.2 on both low and high sides. But I have a problem in getting this. I have got Rejection of more than 80 dB and Return loss of better than 20 dB on both sides. Please give me suggestion what I have to do? thanks in advance. Vikash à 5, 50, 500, 5000 - Store N number of mails in your inbox. Click here. Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. Try the revolutionary next-gen Yahoo! Mail. Click here. Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] subaudibe tones..
Larry, CTCSS was from 60s with Motorola's PL or private line. Ham repeaters got started for the most part in late 60s and few used CTCSS. I'd say most really got into tone in 80s with so many repeaters and lots of other services started using radio for day to day comm. Most Ham VHF/UHF rigs of the 80s had tone option, but now most have at least built in encode from factory with programmable with each memory...very flexible. Motorola used expensive reeds that vibrated at the designed tone when excited and gave more output. A seperate reed was needed for each tone. Some companies like Comm Spec used resonator for each tone. Now with chip technology a programmable tone decoder and encoder is easy. Comm Spec now uses a microprocessor counting the tone period to decode. This is nice for no matter what the tone they know what it is. Just married a dip switch to determine if wanted to give output for particlar tone. Of course then it was easy to marry memory with a number of tones to respond to making a community repeater. Nice design. 73, ron, n9ee/r From: larry allen [EMAIL PROTECTED] Date: 2007/08/26 Sun PM 12:40:39 CDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] subaudibe tones.. Does anyone know when subaudabe tones were introduced into ham radio repeaters.. or more specifically when they became standard in ham radio sets? Larry ve3fxq Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Ralph, Transmission line theory for RF and AC power is totally different. In AC power lines little is paid attention to as for transmission except for R losses and power factor. Yes up the voltage/lower the current and the IR loss goes down. For RF this is totally different for the RF propergatesdown the line, not just passes as voltage and currents. This is why feedlines have specific impedances and loads used. One can have any impedance of coax or twin feeds one wants...that is if you have the material and space for it. One can get off the shelf 75 Ohm twin lead. Using 50 or 75 Ohm has more to do with stability especially at RF. IR drops in feedlines is much less than a factor than the LC/dielectric type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz will have radically different losses yet both have the same I and V and R. 73, ron, n9ee/r From: Ralph Mowery [EMAIL PROTECTED] Date: 2007/08/27 Mon AM 09:20:07 CDT To: Repeater-Builder@yahoogroups.com Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers --- Ron Wright [EMAIL PROTECTED] wrote: Jesse, Then why do twin feeders have much less loss than coax??? Skin affect is even more of a factor there due to the differences in the area of the outer shield in coax vs the twin feeders wire. Maybe it is because of the larger C coupling in the coax due to the larger surface area of the shield. Coax has a lower R even with skin effect than twin line feeders. Skin affect is a factor, but a small one compared to the LC factor. 73, ron, n9ee/r It is not open wire or coax that determins the power loss. It is the impedance of the line and the size of the conductors for frequencies up to 1000 Mhz or so. To transfer 1000 watts of power , the voltage will be higher and the current lower in most prectical open wire lines. That is because the impedance will be around 300 to 600 ohms. Coax is usually 50 or 70 ohms. To get 1000 watts of power through that impedance line it requires less voltage and more current. This is the principal of regular 60 hz power line transmission. Up the voltage to a few hundred thousand volts and the current will go down. This lowers the losses. I don't care to take time to do the calculations, but if you take some small guage wire (say # 20) and space it close to make about 200 ohms line and figuer the loss, it may be higher than some 1 inch or even 1/2 inch hardline. At frequencies below around 1000 Mhz the major loss is the IsqR loss in all lines. Radiation is a very small part. In coax there is a point in which the current on the shield is not flowing but jumping from point to point where the shield wires cross. This causes some resistance. That is partly why the foil shielded coax and hardline is lower in loss than regular coax. __ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=listsid=396545433 Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
The 300 Ohm or 50 Ohm is not part of the R in IR losses. The 300 and 50 are the characteristic impedances of the line and not the R values. One cannot measure the chartistic impedance using an Ohm meter...the R one can and it will most often be very low. Also the characteristic impedance of a transmission line has a bandwidth. Typical RG59 has a lower freq at being 75 Ohms of about 0.5 MHz. Larger lines have lower high freq limits mainly because they start to look like wave guide. Increasing the feedline size say at 100 GHz might actually increase the losses. I think we are getting somewhat confused here,hi. 73, ron, n9ee/r From: Jeff DePolo [EMAIL PROTECTED] Date: 2007/08/27 Mon AM 08:55:41 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers Jesse, Then why do twin feeders have much less loss than coax??? Skin affect is even more of a factor there due to the differences in the area of the outer shield in coax vs the twin feeders wire. The current in a 50 ohm cable is higher as compared to a 300 ohm cable for a given power (by a factor of the sqrt(300/50), or about 2.5) . Power lost due to I2R losses vary in proportion to the square of the current (obviously), so for a given effective resistance in the conductors, a 50 ohm cable would have 6 times greater I2R losses than a 300 ohm cable. But like Ron said, the conductor sizes are typically smaller in a 300 ohm twin lead cable (as compared to, say, 7/8 Heliax), so at some point you start getting into comparing apples and oranges... Maybe it is because of the larger C coupling in the coax due to the larger surface area of the shield. Coax has a lower R even with skin effect than twin line feeders. Again, it depends on the size of the conductors. It's not a valid statement that all 300 ohm balanced lines have lower loss than 50 ohm coax. But if you want to compare the two cables at approximately the same size (say, the diameter of the coax is equal to the width of the twin-lead), then the balanced line is probably going to be the winner in the loss department at VHF. Skin affect is a factor, but a small one compared to the LC factor. Please define the LC factor. --- Jeff Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] Re: subaudibe tones..
At 8/28/2007 23:08, you wrote: On Aug 28, 2007, at 10:29 PM, [EMAIL PROTECTED] wrote: At 8/28/2007 16:01, you wrote: Bob Dengler wrote: One concept that really helps in this area is CTCSS tone frequency standardization, IOW tones by region. All you then need to know is the freq. being used in the area you're traveling to. Many areas are already well established: 110.9 in Rochester NY, 107.2 in Niagara Falls San Diego, 131.8 in Santa Barbara, 127.3 in Springfield MA. Even if you don't know what tone is in use, all you have to do is find the tone of one system. After that you can find the others by kerchunking (with ID of course!) all the other pairs with that tone. Bob NO6B It seems to me that if you have all the repeaters in an area running the same CTCSS tone, and start fighting a mixing problem... everything is going to be back to keying everything else in short order. This gets us back to the CTCSS-bandaid issue. If your ham TXs are IMDing with each other landing back on your inputs, you need to fix it. The only IMD problems I've had linger on my systems were caused by non-amateur TXs. If amateur TXs were involved, we found the actual source of the problem fixed it. Ahh, but the reality is... all hams operating repeaters aren't created equal. If you push that all repeaters in an area run the same tone, and then some doofus comes along and his lashed up mess of a couple of mobiles and a mobile duplexer hooked up with RG-8X and it starts opening itself... he's just as likely to blame it on that big club repeater on the other leg of the tower than on his own ineptitude. So? If he's uncoordinated, he can blame whoever he wants. If you're on a completely different CTCSS tone than Barney Fife there, he has no case and he'll go hunting elsewhere, without any bullets. I don't see why I should make my repeater harder to find simply to cater to such lids. Bob NO6B
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
There's a capacitor hidden in in my coax? Where? I can't find it, and now I've ruined my cable looking for it :-) Yep, whenever one has two conductors with spacing between them you got a cap. For a cap in coax might try looking for the conductors of center and shield...looks like 2 conductors seperated to me, hi. Yep there are caps in that coax. It was a joke... That is what makes a feedline...parrallel caps and series inductors. They determine the coax or any other feedline characterist impedance. You forgot the resistors that are in series with the inductors and caps (in real-world transmission lines). If there weren't resistors in there too, transmissions lines would have no loss. --- Jeff
RE: [Repeater-Builder] Duplexers
It doesn t matter where the min and max are on the line. The same amount of reflected power will be seen at any point. Reflected power does NOT get back into the transmitter. It gets re-reflected back towards the antenna when it reaches the transmitter circuits. I don't buy into this. In order for reflected power to not be absorbed by the TX, it would have to appear totally reactive. Not necessarily true. If there exists a conjugate match at the transmitter, the reflected power will be re-reflected back to the load. The problem, though, is most of our solid state repeater amps may exhibit other problems due to the mis-matched load Z (efficiency drops, PA goes into oscillation, whatever). This doesn't sound right either, as there should be no reflected power at the antenna if it's been matched further down the line. There won't be any reflected power if the matching is done *at the antenna*. If the matching is done at the source end of the line (via a transmatch or similiar device), which is what I believe the topic of discussion was, then there will be reflected power (and likewise VSWR) on the feedline if the load (antenna) Z does not match the cable's characteristic Z. My guess is that the higher power reading on the wattmeter is due to the weird impedances it's seeing on both its input output. If placed along a length of transmission line that has a VSWR other than 1:1, a directional wattmeter (Bird or similiar) will show the sum of forward+reflected with the slug rotated to the forward direction due to the reflected power being re-reflected at the source end. --- Jeff
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
The 300 Ohm or 50 Ohm is not part of the R in IR losses. No, but the Z (300 or 50 or whatever) is what determines the *I* for a given amount of power. The actual losses are due to that I squared, and the R of the conductors themselves. Z is impedance. R is resistance. I think we are getting somewhat confused here,hi. I'm not, at least not yet, but it's still early in the day. --- Jeff
RE: [Repeater-Builder] Re: Duplexers
Quote: “In AC power lines little is paid attention to as for transmission except for R losses and power factor.” I can remember doing an experiment in college where we needed 60 HZ exactly and would have to call the generation plant to see if they were running at 60 HZ. I never did think we could guarantee we had 60 HZ as the Z will change somewhat with distance from the plant. That is why the power companies put large capacitors in the line to bring it back in phase. Quote: “Yes up the voltage/lower the current and the IR loss goes down.” This brought back a laugh as I once ran 500 foot of extension cord to run a circular saw. Wasn’t getting much done so I hooked it up to 220 volts source. Had about 140 volts under load. You could saw till the blade turned blue. Randy B. -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Wednesday, August 29, 2007 10:32 AM To: Repeater-Builder@yahoogroups.com Subject: Re: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers Ralph, Transmission line theory for RF and AC power is totally different. In AC power lines little is paid attention to as for transmission except for R losses and power factor. Yes up the voltage/lower the current and the IR loss goes down. For RF this is totally different for the RF propergatesdown the line, not just passes as voltage and currents. This is why feedlines have specific impedances and loads used. One can have any impedance of coax or twin feeds one wants...that is if you have the material and space for it. One can get off the shelf 75 Ohm twin lead. Using 50 or 75 Ohm has more to do with stability especially at RF. IR drops in feedlines is much less than a factor than the LC/dielectric type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz will have radically different losses yet both have the same I and V and R. 73, ron, n9ee/r From: Ralph Mowery HYPERLINK mailto:ku4pt%40yahoo.com[EMAIL PROTECTED] Date: 2007/08/27 Mon AM 09:20:07 CDT To: HYPERLINK mailto:Repeater-Builder%40yahoogroups.com[EMAIL PROTECTED] m Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers --- Ron Wright HYPERLINK mailto:mccrpt%40verizon.net[EMAIL PROTECTED] wrote: Jesse, Then why do twin feeders have much less loss than coax??? Skin affect is even more of a factor there due to the differences in the area of the outer shield in coax vs the twin feeders wire. Maybe it is because of the larger C coupling in the coax due to the larger surface area of the shield. Coax has a lower R even with skin effect than twin line feeders. Skin affect is a factor, but a small one compared to the LC factor. 73, ron, n9ee/r It is not open wire or coax that determins the power loss. It is the impedance of the line and the size of the conductors for frequencies up to 1000 Mhz or so. To transfer 1000 watts of power , the voltage will be higher and the current lower in most prectical open wire lines. That is because the impedance will be around 300 to 600 ohms. Coax is usually 50 or 70 ohms. To get 1000 watts of power through that impedance line it requires less voltage and more current. This is the principal of regular 60 hz power line transmission. Up the voltage to a few hundred thousand volts and the current will go down. This lowers the losses. I don't care to take time to do the calculations, but if you take some small guage wire (say # 20) and space it close to make about 200 ohms line and figuer the loss, it may be higher than some 1 inch or even 1/2 inch hardline. At frequencies below around 1000 Mhz the major loss is the IsqR loss in all lines. Radiation is a very small part. In coax there is a point in which the current on the shield is not flowing but jumping from point to point where the shield wires cross. This causes some resistance. That is partly why the foil shielded coax and hardline is lower in loss than regular coax. ___-_-_-_-_-_-__ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. HYPERLINK http://answers.yahoo.com/dir/?link=listsid=396545433http://answers.-yahoo .com/-dir/?link=-listsid=-396545433 Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Quote: “If there weren't resistors in there too, transmission lines would have no loss.” Yes, with a perfect Z, resistance would be the only math to do for loss. But it is never perfect as even FM has a changing frequency and we use a broad range of frequencies. I have enjoyed this thread so much I am printing it out and re-reading it to get more knowledge. I tip my hat and bow deeply in your direction. Randy W4CPT Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Wednesday, August 29, 2007 11:28 AM To: Repeater-Builder@yahoogroups.com Subject: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers There's a capacitor hidden in in my coax? Where? I can't find it, and now I've ruined my cable looking for it :-) Yep, whenever one has two conductors with spacing between them you got a cap. For a cap in coax might try looking for the conductors of center and shield...looks like 2 conductors seperated to me, hi. Yep there are caps in that coax. It was a joke... That is what makes a feedline...parralle-l caps and series inductors. They determine the coax or any other feedline characterist impedance. You forgot the resistors that are in series with the inductors and caps (in real-world transmission lines). If there weren't resistors in there too, transmissions lines would have no loss. --- Jeff No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
[Repeater-Builder] New file uploaded to Repeater-Builder
Hello, This email message is a notification to let you know that a file has been uploaded to the Files area of the Repeater-Builder group. File: /FluX Research/SEA ESP1000(M), ESP1100(M), ESP-504/FluX Research Technical Service Bulletin - FXR-06.pdf Uploaded by : dcflux [EMAIL PROTECTED] Description : Modifying SEA 220 - 222 MHz ACSSB equipment for 222 - 225 MHz ACSSB Amateur Radio Applications (v1.4 Updated 08-24-3007) You can access this file at the URL: http://groups.yahoo.com/group/Repeater-Builder/files/FluX%20Research/SEA%20ESP1000%28M%29%2C%20ESP1100%28M%29%2C%20ESP-504/FluX%20Research%20Technical%20Service%20Bulletin%20-%20FXR-06.pdf To learn more about file sharing for your group, please visit: http://help.yahoo.com/help/us/groups/files Regards, dcflux [EMAIL PROTECTED]
Re: [Repeater-Builder] Re: subaudibe tones..
[EMAIL PROTECTED] wrote: If you push that all repeaters in an area run the same tone, and then some doofus comes along and his lashed up mess of a couple of mobiles and a mobile duplexer hooked up with RG-8X and it starts opening itself... he's just as likely to blame it on that big club repeater on the other leg of the tower than on his own ineptitude. So? If he's uncoordinated, he can blame whoever he wants. Who said he would be uncoordinated? :-) If you're on a completely different CTCSS tone than Barney Fife there, he has no case and he'll go hunting elsewhere, without any bullets. I don't see why I should make my repeater harder to find simply to cater to such lids. I can only think of two VHF repeaters out of a completely full band out here that don't have tones on them and no one around here seems to have any difficulting finding them? Not sure what you mean. Might take someone 3 minutes to figure out the tone if they want to transmit through one of them, but scanning without tone still works fine to find them, AFAIK. I have two rigs in the house that will auto-scan for tones... they're both Amateur rigs, not commercial or anything fancy... One of our UHF repeaters has an on-channel link to it, so we set up the repeater in Tone-on-User-CTCSS mode, and while it was originally done for the link, I've come to enjoy the sound of it... you only hear when someone is talking. You can push the squelch open button on your rig if you're questioning whether or not you're in a good coverage area... to listen to the transmitter tail (which is sent without tone). Nate WY0X
[Repeater-Builder] Duplexer input and output power
Hi Guys, I have saved a whole lot of information (about duplexers) from all the engineer's explanations here for my radio club classes. Now I don't want to change the topic, but I have one simple question to asked. Is there a table or formula or ratio for power input to a duplexer, to the resulting output power of the said? For instance, if I put 10, 20, 50, 100 watts to the input, what should be the output, with a 50 Ohms at the load? example 10,20, 50, 100 watts in = x output @ 50 Ohms. BASED ON A PROPERLY TUNED DUPLEXER I think someone had a short for-instance on this, can't find it, and will like some insight on this. v44kai.Joel. - Original Message - From: Jeff DePolo [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, August 29, 2007 10:39 AM Subject: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers The 300 Ohm or 50 Ohm is not part of the R in IR losses. No, but the Z (300 or 50 or whatever) is what determines the *I* for a given amount of power. The actual losses are due to that I squared, and the R of the conductors themselves. Z is impedance. R is resistance. I think we are getting somewhat confused here,hi. I'm not, at least not yet, but it's still early in the day. --- Jeff
Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
I hope your printer has a lot of paper Randy, This will be the 61st message sent :) Jesse On 8/29/07, R. K. Brumback [EMAIL PROTECTED] wrote: Quote*: **If there weren't resistors in there too, transmission lines would have no loss.* Yes, with a perfect Z, resistance would be the only math to do for loss. But it is never perfect as even FM has a changing frequency and we use a broad range of frequencies. I have enjoyed this thread so much I am printing it out and re-reading it to get more knowledge. I tip my hat and bow deeply in your direction. Randy W4CPT Original Message- *From:* Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] ups.com] *On Behalf Of *Jeff DePolo *Sent:* Wednesday, August 29, 2007 11:28 AM *To:* Repeater-Builder@yahoogroups.com *Subject:* RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers There's a capacitor hidden in in my coax? Where? I can't find it, and now I've ruined my cable looking for it :-) Yep, whenever one has two conductors with spacing between them you got a cap. For a cap in coax might try looking for the conductors of center and shield...looks like 2 conductors seperated to me, hi. Yep there are caps in that coax. It was a joke... That is what makes a feedline...parrallel caps and series inductors. They determine the coax or any other feedline characterist impedance. You forgot the resistors that are in series with the inductors and caps (in real-world transmission lines). If there weren't resistors in there too, transmissions lines would have no loss. --- Jeff No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
[Repeater-Builder] Repeater Range : Estimate Program Available
OK Groovy Guys and Gals, Is there a simple rule of thumb radio range versus frequency and power level type computer program/software on the web? Maybe some software that also considers generic repeater operation from x-height agl with input frequency and power values. My friend doesn't need or really want a program with involved graphics or Lat Long issues. Most of his Ham Radio work is actually FM Simplex on flat ground and he's really interested in using the program for both VHF High and Low Bands as a very rough estimate of expected operational range (on flat ground) in miles. Your turn... Thanks in advance... skipp
[Repeater-Builder] Re: Duplexer input and output power
Hi Joel, In the real world it depends on the duplexer type, size, quality, operation and setup values, which may be fixed or adjustable. Just throwing out a generic rule of thumb... you will find many duplexers lose about 15% to 35% of the input power. One would hope for near zero loss but that will never happen. A common quality duplexer has adjustable probes or coax ports (the name used is based on the duplexer type), which often trade what we generic call insertion loss for increased performance. Loss through a duplexer is not always a linear graph of power in vs power out. Just to put something out... be happy if a properly setup and working duplexer delivers 75% to maybe 95% of the input power. Be grateful if you receive better than 85% of the rated power. A really tight duplexer might eat as much as 35% to 40% of your input power and there are much worse possible examples. cheers, s. Joel [EMAIL PROTECTED] wrote: Is there a table or formula or ratio for power input to a duplexer, to the resulting output power of the said? For instance, if I put 10, 20, 50, 100 watts to the input, what should be the output, with a 50 Ohms at the load? example 10,20, 50, 100 watts in = x output @ 50 Ohms. BASED ON A PROPERLY TUNED DUPLEXER I think someone had a short for-instance on this, can't find it, and will like some insight on this. v44kai.Joel.
Re: [Repeater-Builder] Repeater Range : Estimate Program Available
I use Radiomobile for all my plots. Works great, but there is a bit of a learning curve. It plots paths over dted and srtm elevation data and is quite good at guessing rx strength. For basic radio range it depends on line of sight so greatly that you really need something that will take hills into effect. Baring that you can always do a simple free space loss calculation. Jesse On 8/29/07, skipp025 [EMAIL PROTECTED] wrote: OK Groovy Guys and Gals, Is there a simple rule of thumb radio range versus frequency and power level type computer program/software on the web? Maybe some software that also considers generic repeater operation from x-height agl with input frequency and power values. My friend doesn't need or really want a program with involved graphics or Lat Long issues. Most of his Ham Radio work is actually FM Simplex on flat ground and he's really interested in using the program for both VHF High and Low Bands as a very rough estimate of expected operational range (on flat ground) in miles. Your turn... Thanks in advance... skipp
Re: [Repeater-Builder] Repeater Range : Estimate Program Available
skipp025 wrote: OK Groovy Guys and Gals, Is there a simple rule of thumb radio range versus frequency and power level type computer program/software on the web? Maybe some software that also considers generic repeater operation from x-height agl with input frequency and power values. My friend doesn't need or really want a program with involved graphics or Lat Long issues. Most of his Ham Radio work is actually FM Simplex on flat ground and he's really interested in using the program for both VHF High and Low Bands as a very rough estimate of expected operational range (on flat ground) in miles. Your turn... Thanks in advance... skipp Even though he doesn't need it, I think spending the effort to learn how to drive RadioMobile is time well spent, if you're into looking at paths, coverage, etc. For a free program, it's really not bad at all. And it'd give him something to grow into after he mastered the basics. Nate WY0X
[Repeater-Builder] 6 meter duplexer (system) web page
Found this while bumbling around the net... 6 meter duplexer (system) web page http://www.bcarn.net/6m_repeater_project.htm http://www.bcarn.net/6m-project-duplexer.htm cheers, skipp
Re: [Repeater-Builder] Re: Duplexer input and output power
Ya, duplexers will have insertion loss. Typically you get more insertion loss with more rejection, so its a balancing act. Insertion loss can range from .1 dB (very good) to 3 dB. Typically if I can get a duplexer to less than a dB I'm happy. *Insertion loss (dB) = 10 log ( P**IN** / P**OUT** ) * So Pout = Pin x 10^(Insertion Loss/10) So for 50 Watts: .1 dB = 48.9 Watts .3 = 46.7 .5 = 44.6 .8 = 41.6 1 = 39.7 1.2 = 37.9 1.5 = 35.4 2 = 31.5 2.5 = 28.1 3 = 25 Jesse On 8/29/07, skipp025 [EMAIL PROTECTED] wrote: Hi Joel, In the real world it depends on the duplexer type, size, quality, operation and setup values, which may be fixed or adjustable. Just throwing out a generic rule of thumb... you will find many duplexers lose about 15% to 35% of the input power. One would hope for near zero loss but that will never happen. A common quality duplexer has adjustable probes or coax ports (the name used is based on the duplexer type), which often trade what we generic call insertion loss for increased performance. Loss through a duplexer is not always a linear graph of power in vs power out. Just to put something out... be happy if a properly setup and working duplexer delivers 75% to maybe 95% of the input power. Be grateful if you receive better than 85% of the rated power. A really tight duplexer might eat as much as 35% to 40% of your input power and there are much worse possible examples. cheers, s. Joel [EMAIL PROTECTED] wrote: Is there a table or formula or ratio for power input to a duplexer, to the resulting output power of the said? For instance, if I put 10, 20, 50, 100 watts to the input, what should be the output, with a 50 Ohms at the load? example 10,20, 50, 100 watts in = x output @ 50 Ohms. BASED ON A PROPERLY TUNED DUPLEXER I think someone had a short for-instance on this, can't find it, and will like some insight on this. v44kai.Joel.
Re: [Repeater-Builder] Re: subaudibe tones..
Bob Dengler wrote: One concept that really helps in this area is CTCSS tone frequency standardization, IOW tones by region. All you then need to know is the freq. being used in the area you're traveling to. Many areas are already well established: 110.9 in Rochester NY, 107.2 in Niagara Falls San Diego, 131.8 in Santa Barbara, 127.3 in Springfield MA. Even if you don't know what tone is in use, all you have to do is find the tone of one system. After that you can find the others by kerchunking (with ID of course!) all the other pairs with that tone. Bob NO6B Right-Cleveland area 2M repeaters have used 110.9 since the mid-70's, since most of the PD's FD's in Cuyahoga Co. used it on VHF, and 131.8 on UHF, thus an abundance of reeds back then. -- Jim Barbour WD8CHL
[Repeater-Builder] D-STAR Presenter / Presentation Needed at DCC (Digital Communications Conference)
The upcoming DCC in Hartford, CT has two slots for presenters still open. In recent years there has been a D-STAR presentation, but this year no presenter has been identified and Icom is not available to do a presentation due to other obligations. I could do an Overview / Introduction presentation, but I hadn't planned to attend this year's DCC. Next year the DCC will be in Chicago I'm one of the local hosts. So is anyone planning to attend the DCC and if so could you do a D-STAR presentation? This presentation should be done by someone who has actually used D-STAR and has some degree of experience with D-STAR. I would be willing to share my presentation if someone needs it for the DCC. 73, Mark, WB9QZB Chicago, IL http://groups.yahoo.com/group/illinoisdigitalham/ - Forwarded Message From: [EMAIL PROTECTED] [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Wednesday, August 29, 2007 9:50:29 AM Subject: Fwd: [dcc] Introductory Talks In a message dated 8/29/2007 9:33:36 A.M. Central Daylight Time, [EMAIL PROTECTED] writes: Hi Everyone, The preliminary schedule is posted to the DCC web site. It is a full schedule. All but four of the authors are presenting. A very good turn out. This is a strong year for technical experimenting and the DCC. For Introductory talks I have Dan Welch's Eagle CAD for the first period (Dan volunteered again this year) and Steve Ford's Intro to HF Digital on the second period. I don't have any other intro topics. D-Star was mentioned, but we don't have anyone to present it. Any other topics? We need speakers to present them as well. I have two more slots. I would hope to fill at least one of them. - Steve N7HPR ___ dcc mailing list [EMAIL PROTECTED] https://lists.tapr.org/cgi-bin/mailman/listinfo/dcc Get a sneak peek of the all-new AOL.com. Hi Everyone, The preliminary schedule is posted to the DCC web site. It is a full schedule. All but four of the authors are presenting. A very good turn out. This is a strong year for technical experimenting and the DCC. For Introductory talks I have Dan Welch's Eagle CAD for the first period (Dan volunteered again this year) and Steve Ford's Intro to HF Digital on the second period. I don't have any other intro topics. D-Star was mentioned, but we don't have anyone to present it. Any other topics? We need speakers to present them as well. I have two more slots. I would hope to fill at least one of them. - Steve N7HPR ___ dcc mailing list [EMAIL PROTECTED] https://lists.tapr.org/cgi-bin/mailman/listinfo/dcc Shape Yahoo! in your own image. Join our Network Research Panel today! http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7
Re: [Repeater-Builder] Repeater Range : Estimate Program Available
Ya I use it at work too. Its better than at least 1/2 of the commercial products available. Quite amazing considering a Ham out of Quebec programmed it. Jesse On 8/29/07, Nate Duehr [EMAIL PROTECTED] wrote: skipp025 wrote: OK Groovy Guys and Gals, Is there a simple rule of thumb radio range versus frequency and power level type computer program/software on the web? Maybe some software that also considers generic repeater operation from x-height agl with input frequency and power values. My friend doesn't need or really want a program with involved graphics or Lat Long issues. Most of his Ham Radio work is actually FM Simplex on flat ground and he's really interested in using the program for both VHF High and Low Bands as a very rough estimate of expected operational range (on flat ground) in miles. Your turn... Thanks in advance... skipp Even though he doesn't need it, I think spending the effort to learn how to drive RadioMobile is time well spent, if you're into looking at paths, coverage, etc. For a free program, it's really not bad at all. And it'd give him something to grow into after he mastered the basics. Nate WY0X
Re: [Repeater-Builder] Re: [AR902Mhz Repeater-Builder] PURC 5000 questions
Bob M. wrote: A third has an actual numeric keypad on the front panel, but it's usually locked so it can't easily be changed. Either a password or flipping a DIP switch inside the unit would be necessary to allow frequency programming. The default password is 5000, and I have yet to see one where it had been changed. But yes, I remember there is a dip switch or push-on jumper that can disable the keypad. -- Jim Barbour WD8CHL
Re: [Repeater-Builder] Re: subaudibe tones..
Jack Taylor wrote: PL access is a useful tool when all other means have been taken to get rid of undesirable audio artifacts on a repeater. Usually this includes harmonious coordination with the other users at a site and a knowledgeable technical approach to the problem. All to often though, mandatory PL is just a band aid to hide the lack of expertise of those concerned. Not in Ohio-too many repeaters to avoid it. And then you get band openings along Lake Erie and suddenly a repeater in Buffalo is hand-held accessible in Cleveland, Toledo, and Detroit. Or vice versa. -- Jim Barbour WD8CHL
Re: [Repeater-Builder] Re: [AR902Mhz Repeater-Builder] PURC 5000 questions
There's probably some FCC rule that prohibits commercial stuff from being front-panel programmable by other than the manufacturer or a radio technician. Nucleus paging transmitters have a DIP switch inside that disables frequency programming. Some radios require a special dongle to be attached to allow freqs to be entered. So I figured that the PURC is no different and while it's capable of being programmed, there's a mechanism in place to inhibit it to all but those who should know what they're doing. Bob M. == --- Jim [EMAIL PROTECTED] wrote: Bob M. wrote: A third has an actual numeric keypad on the front panel, but it's usually locked so it can't easily be changed. Either a password or flipping a DIP switch inside the unit would be necessary to allow frequency programming. The default password is 5000, and I have yet to see one where it had been changed. But yes, I remember there is a dip switch or push-on jumper that can disable the keypad. -- Jim Barbour WD8CHL Park yourself in front of a world of choices in alternative vehicles. Visit the Yahoo! Auto Green Center. http://autos.yahoo.com/green_center/
RE: [Repeater-Builder] Duplexers
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, August 28, 2007 10:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers At 8/27/2007 20:52, you wrote: Yes your right VSWR is the ratio between Vmax and Vmin, node and anodes, of the interference pattern caused by standing waves. Even still there is a point where the voltage is at a minimum on the line. What happens if that point is at the transmitters output... does it help keep the heat down in the transmitter due to high SWR? It doesn t matter where the min and max are on the line. The same amount of reflected power will be seen at any point. Reflected power does NOT get back into the transmitter. It gets re-reflected back towards the antenna when it reaches the transmitter circuits. I don't buy into this. In order for reflected power to not be absorbed by the TX, it would have to appear totally reactive. Although I've never measured one, I don't believe that's the case. If you have two watt meters and an antenna matching device you can put one wattmeter between the transmitter and the matching device and tune it for minimum reflected power on the first meter. Then with a second meter between the tuner and the mismatched load you can see the second wattmeter that is reading the reflected power. The second wattmeter will have a higher forward power reading than the first due to the added re-reflected power. This doesn't sound right either, as there should be no reflected power at the antenna if it's been matched further down the line. The tuner would be adjusted so as to create a conjugate impedance of the antenna at the end of the feeding coax, thus eliminating the mismatch. My guess is that the higher power reading on the wattmeter is due to the weird impedances it's seeing on both its input output. Bob NO6B Hi Bob, Please read again what I wrote. I am not sure that you are following how the meters are in the circuit. Remember that whatever you do at the transmitter end of a transmission line has no affect on what is going on in the line itself. The only thing that will change the swr on the line is what you do at the load. 73 Gary K4FMX
RE: RE: [Repeater-Builder] Duplexers
Your typical swr meter does not measure voltage on the line. It is measuring a combination of voltage and current. By just measuring voltage it is impossible to tell which is forward and which is reflected. By using a slotted line you can find voltage min and max but you must have a line that is at least 1/4 wavelength long. This is impractical at HF frequencies and cumbersome at VHF. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Wednesday, August 29, 2007 9:00 AM To: Repeater-Builder@yahoogroups.com Subject: Re: RE: [Repeater-Builder] Duplexers I think he quote needs little correction...âWhen you are using a VSWR meter you are measuring voltageS, not just one voltage, hi. You are measuring voltage ratios. The SWR reading due to losses changes when one moves closer or farther away from the end of a feedline. The power going out is attenuated, then the load reflects a portion of this back and gets attenuated again and the reflected is measured. Moving closer increases the power to the load and also increases the reflected read at the source showing a higher SWR. Lengthing the cable does the opposite. This is why one can have say 500 ft of RG58 at 450 MHz completly open at the load end and the swr might read 1.5:1 at the source. Also for long feedlines with antennas can give deceptive readings at the source. SWR at the load is much more real. 73, ron, n9ee/r From: R. K. Brumback [EMAIL PROTECTED] Date: 2007/08/27 Mon PM 12:25:59 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Quote from Jesse: âWhen you are using a VSWR meter you are measuringvoltage, if you move the meter to a different spot on the cable, the voltage isdifferent, therefore it gives you a different reading.â This now makes more sense to me as I once saw a feed line demonstrationwith voltage and current sleds showing the difference at different points alongthe line. At some places the voltage was null (as with any sine wave). I donâtsee how this could happen at the antenna port of a transmitter unless it wasmicrowave as the cabling from the tuner to the output connector is not near ½ wave. Also to Alan, I appreciate your sympathy for us âlittle peopleâbut I do find this very interesting. And as you can see, the experts sometimesneed a tune up. Randy W4CPT -Original Message- From: [EMAIL PROTECTED]:Repeater- [EMAIL PROTECTED] OnBehalf Of Jesse Lloyd Sent: Monday, August 27, 2007 12:48 PM To:Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder]Duplexers The length of coaxdoesn't effect impedance. Trimming the coax effects what is read on theVSWR meter because what is actually happening is that there is an interferencepattern created when you have a mismatch on the end of feedline. This patternis sinusoidal and changes in voltage and current along the line, in 1/2 waveperiods. You will find max voltage peaks and min voltage peaks. Also current will go up and down too. When you are using a VSWR meter youare measuring voltage, if you move the meter to a different spot on the cable,the voltage is different, therefor it gives you a different reading. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating thereflected power into its heatsink. If you put it at a voltage null, Iwould suspect that the SWR would not get dissipated by the transmitter as muchas if you put it at a voltage peak. The standing waves are still there,there is still a mismatch, you will get the same power out, but its just notgoing to hurt your transmitter as much because of the heat. The only time coax length makes a difference to power out is if your using itin a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohmcable put it on the end of 50 ohm cable you will get a match with a 112.5 ohmload. You make an interesting point though, why does the cabling of duplexer's needto be a certain length. I would suspect that its because they are loopedand make an inductor. This then is part of the LC filtering, and changing thelength effects L. But I could be wrong on that. Jesse On 8/27/07, R. K. Brumback [EMAIL PROTECTED]wrote: I have heardthis point argued for years. Does trimming the coax affect theSWR? If the length of coax has an affect on impedance, then howcould it not affect power out? We strive to maintain 50 ohms at the tail of alldevices to match the end load. GE puts matching networks in their Mastr II's. Ihave taken a MFJ-259 and soldered a PL259 only at one end and then startedtrimming the coax down and watched the impedance change significantly with eachcut. Duplexers come with precise lengths of cabling. I have heard thattrimming coax only fools the meter. Not being
[Repeater-Builder] Re: Duplexer input and output power
Jesse, Your math is right on the money. And you are right about the balancing act. In order to achieve 40 dB of notch rejection in a typical 4-can BpBr duplexer for 2m operation, the coupling loops must be set for about 0.75 dB insertion loss per cavity. This results in an insertion loss of about 1.5 dB for each side of the duplexer, meaning that about 71% of the transmitter's power makes it to the antenna feedline. If you need 120 dB of notch depth, which usually calls for a six-cavity duplexer, you might have an insertion loss of about 2.2 dB. In this case, only 60% of the transmitter output is available at the output of the duplexer. The bottom line here is that you can adjust the loops to achieve any insertion loss you want- but the notch depth decreases as the loops are moved to reduce insertion loss. Let's not forget that any power lost in the duplexer due to insertion loss winds up heating the duplexer- it doesn't just evaporate into thin air. For example, a 250-watt 2m repeater with a six-cavity BpBr duplexer set for 2.5 dB insertion loss will have about 109 watts dissipated in the three TX cans. They may get pretty hot after a period of near-continuous operation. Even with special-alloy tuning shafts and high-quality construction, there will be some pumping of the tuning elements. Over time, this movement due to repeated heating and cooling will cause wear in the sliding contact surfaces, possibly exposing the base metal under the plating. Yes, a duplexer can wear out over time! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Wednesday, August 29, 2007 10:55 AM To: Repeater-Builder@yahoogroups.com Subject: [Norton AntiSpam] Re: [Repeater-Builder] Re: Duplexer input and output power Ya, duplexers will have insertion loss. Typically you get more insertion loss with more rejection, so its a balancing act. Insertion loss can range from .1 dB (very good) to 3 dB. Typically if I can get a duplexer to less than a dB I'm happy. Insertion loss (dB) = 10 log ( PIN / POUT ) So Pout = Pin x 10^(Insertion Loss/10) So for 50 Watts: .1 dB = 48.9 Watts .3 = 46.7 .5 = 44.6 .8 = 41.6 1 = 39.7 1.2 = 37.9 1.5 = 35.4 2 = 31.5 2.5 = 28.1 3 = 25 Jesse On 8/29/07, skipp025 [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: Hi Joel, In the real world it depends on the duplexer type, size, quality, operation and setup values, which may be fixed or adjustable. Just throwing out a generic rule of thumb... you will find many duplexers lose about 15% to 35% of the input power. One would hope for near zero loss but that will never happen. A common quality duplexer has adjustable probes or coax ports (the name used is based on the duplexer type), which often trade what we generic call insertion loss for increased performance. Loss through a duplexer is not always a linear graph of power in vs power out. Just to put something out... be happy if a properly setup and working duplexer delivers 75% to maybe 95% of the input power. Be grateful if you receive better than 85% of the rated power. A really tight duplexer might eat as much as 35% to 40% of your input power and there are much worse possible examples. cheers, s. Joel [EMAIL PROTECTED] wrote: Is there a table or formula or ratio for power input to a duplexer, to the resulting output power of the said? For instance, if I put 10, 20, 50, 100 watts to the input, what should be the output, with a 50 Ohms at the load? example 10,20, 50, 100 watts in = x output @ 50 Ohms. BASED ON A PROPERLY TUNED DUPLEXER I think someone had a short for-instance on this, can't find it, and will like some insight on this. v44kai.Joel.
RE: [Repeater-Builder] Re: Duplexer input and output power
Ooops, that's 40 dB per can- 80 dB per side. My bad! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric Lemmon Sent: Wednesday, August 29, 2007 7:03 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Duplexer input and output power Jesse, Your math is right on the money. And you are right about the balancing act. In order to achieve 40 dB of notch rejection in a typical 4-can BpBr duplexer for 2m operation, the coupling loops must be set for about 0.75 dB insertion loss per cavity. This results in an insertion loss of about 1.5 dB for each side of the duplexer, meaning that about 71% of the transmitter's power makes it to the antenna feedline. If you need 120 dB of notch depth, which usually calls for a six-cavity duplexer, you might have an insertion loss of about 2.2 dB. In this case, only 60% of the transmitter output is available at the output of the duplexer. The bottom line here is that you can adjust the loops to achieve any insertion loss you want- but the notch depth decreases as the loops are moved to reduce insertion loss. Let's not forget that any power lost in the duplexer due to insertion loss winds up heating the duplexer- it doesn't just evaporate into thin air. For example, a 250-watt 2m repeater with a six-cavity BpBr duplexer set for 2.5 dB insertion loss will have about 109 watts dissipated in the three TX cans. They may get pretty hot after a period of near-continuous operation. Even with special-alloy tuning shafts and high-quality construction, there will be some pumping of the tuning elements. Over time, this movement due to repeated heating and cooling will cause wear in the sliding contact surfaces, possibly exposing the base metal under the plating. Yes, a duplexer can wear out over time! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Jesse Lloyd Sent: Wednesday, August 29, 2007 10:55 AM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Norton AntiSpam] Re: [Repeater-Builder] Re: Duplexer input and output power Ya, duplexers will have insertion loss. Typically you get more insertion loss with more rejection, so its a balancing act. Insertion loss can range from .1 dB (very good) to 3 dB. Typically if I can get a duplexer to less than a dB I'm happy. Insertion loss (dB) = 10 log ( PIN / POUT ) So Pout = Pin x 10^(Insertion Loss/10) So for 50 Watts: .1 dB = 48.9 Watts .3 = 46.7 .5 = 44.6 .8 = 41.6 1 = 39.7 1.2 = 37.9 1.5 = 35.4 2 = 31.5 2.5 = 28.1 3 = 25 Jesse On 8/29/07, skipp025 [EMAIL PROTECTED] mailto:skipp025%40yahoo.com mailto:[EMAIL PROTECTED] mailto:skipp025%40yahoo.com wrote: Hi Joel, In the real world it depends on the duplexer type, size, quality, operation and setup values, which may be fixed or adjustable. Just throwing out a generic rule of thumb... you will find many duplexers lose about 15% to 35% of the input power. One would hope for near zero loss but that will never happen. A common quality duplexer has adjustable probes or coax ports (the name used is based on the duplexer type), which often trade what we generic call insertion loss for increased performance. Loss through a duplexer is not always a linear graph of power in vs power out. Just to put something out... be happy if a properly setup and working duplexer delivers 75% to maybe 95% of the input power. Be grateful if you receive better than 85% of the rated power. A really tight duplexer might eat as much as 35% to 40% of your input power and there are much worse possible examples. cheers, s. Joel [EMAIL PROTECTED] wrote: Is there a table or formula or ratio for power input to a duplexer, to the resulting output power of the said? For instance, if I put 10, 20, 50, 100 watts to the input, what should be the output, with a 50 Ohms at the load? example 10,20, 50, 100 watts in = x output @ 50 Ohms. BASED ON A PROPERLY TUNED DUPLEXER I think someone had a short for-instance on this, can't find it, and will like some insight on this. v44kai.Joel.
RE: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Transmission line theory is transmission line theory. It doesn't matter what the frequency is it all works the same. Power line transmission engineers worry about the same things in power transmission as do RF engineers. Only the wavelength is different. IR drops in feed lines is much less than a factor than the LC/dielectric type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz will have radically different losses yet both have the same I and V and R. A feed line at 10 MHz has a totally different R loss than the same feed line used at 1000 MHz. It does NOT have the same R at different frequencies. It has the same Z (surge or characteristic impedance) at all frequencies but not the same series resistance R. The resistance increases because of skin effect the higher the frequency is. This is where loss comes from. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Wednesday, August 29, 2007 9:32 AM To: Repeater-Builder@yahoogroups.com Subject: Re: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers Ralph, Transmission line theory for RF and AC power is totally different. In AC power lines little is paid attention to as for transmission except for R losses and power factor. Yes up the voltage/lower the current and the IR loss goes down. For RF this is totally different for the RF propergatesdown the line, not just passes as voltage and currents. This is why feedlines have specific impedances and loads used. One can have any impedance of coax or twin feeds one wants...that is if you have the material and space for it. One can get off the shelf 75 Ohm twin lead. Using 50 or 75 Ohm has more to do with stability especially at RF. IR drops in feedlines is much less than a factor than the LC/dielectric type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz will have radically different losses yet both have the same I and V and R. 73, ron, n9ee/r From: Ralph Mowery [EMAIL PROTECTED] Date: 2007/08/27 Mon AM 09:20:07 CDT To: Repeater-Builder@yahoogroups.com Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers --- Ron Wright [EMAIL PROTECTED] wrote: Jesse, Then why do twin feeders have much less loss than coax??? Skin affect is even more of a factor there due to the differences in the area of the outer shield in coax vs the twin feeders wire. Maybe it is because of the larger C coupling in the coax due to the larger surface area of the shield. Coax has a lower R even with skin effect than twin line feeders. Skin affect is a factor, but a small one compared to the LC factor. 73, ron, n9ee/r It is not open wire or coax that determins the power loss. It is the impedance of the line and the size of the conductors for frequencies up to 1000 Mhz or so. To transfer 1000 watts of power , the voltage will be higher and the current lower in most prectical open wire lines. That is because the impedance will be around 300 to 600 ohms. Coax is usually 50 or 70 ohms. To get 1000 watts of power through that impedance line it requires less voltage and more current. This is the principal of regular 60 hz power line transmission. Up the voltage to a few hundred thousand volts and the current will go down. This lowers the losses. I don't care to take time to do the calculations, but if you take some small guage wire (say # 20) and space it close to make about 200 ohms line and figuer the loss, it may be higher than some 1 inch or even 1/2 inch hardline. At frequencies below around 1000 Mhz the major loss is the IsqR loss in all lines. Radiation is a very small part. In coax there is a point in which the current on the shield is not flowing but jumping from point to point where the shield wires cross. This causes some resistance. That is partly why the foil shielded coax and hardline is lower in loss than regular coax. __ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=listsid=396545433 Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. Yahoo! Groups Links
Re: [Repeater-Builder] Re: subaudibe tones..
Which results in OH 'claiming' 30 of the 32 (or 38) available tones. That leaves 2 or 8 tones for everyone else. Not a particularly fair or reasonable plan. Joe M. Jim wrote: Right-Cleveland area 2M repeaters have used 110.9 since the mid-70's, since most of the PD's FD's in Cuyahoga Co. used it on VHF, and 131.8 on UHF, thus an abundance of reeds back then. -- Jim Barbour WD8CHL
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
You can not measure R with an ohmmeter either. R is the AC resistance of the wires in the line and must be measured at the operating frequency. Note that AC resistance is a different thing than impedance. AC resistance is the result of skin effect losses in a wire. Skin effect is the result of eddy currents within a conductor causing cancellations in current flow below the surface of the conductor so less depth of the conductor is effective in carrying the current thus the thinner surface available to carry current. The thin surface gets thinner as frequency is increased. This thinner surface has higher resistance the higher the frequency applied to the conductor. Thus the term AC resistance. It is the measure of resistance to an AC signal. Much different than DC resistance of the same conductor. As far as bandwidth goes,,, where do you get this .5 MHz for rg59 cable as a lower limit? Open wire lines begin to radiate as frequency is increased to the point where the line spacing becomes an appreciable portion of a wave length due to the time it takes for propagation of fields between wires. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Wednesday, August 29, 2007 9:37 AM To: Repeater-Builder@yahoogroups.com Subject: Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers The 300 Ohm or 50 Ohm is not part of the R in IR losses. The 300 and 50 are the characteristic impedances of the line and not the R values. One cannot measure the chartistic impedance using an Ohm meter...the R one can and it will most often be very low. Also the characteristic impedance of a transmission line has a bandwidth. Typical RG59 has a lower freq at being 75 Ohms of about 0.5 MHz. Larger lines have lower high freq limits mainly because they start to look like wave guide. Increasing the feedline size say at 100 GHz might actually increase the losses. I think we are getting somewhat confused here,hi. 73, ron, n9ee/r From: Jeff DePolo [EMAIL PROTECTED] Date: 2007/08/27 Mon AM 08:55:41 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers Jesse, Then why do twin feeders have much less loss than coax??? Skin affect is even more of a factor there due to the differences in the area of the outer shield in coax vs the twin feeders wire. The current in a 50 ohm cable is higher as compared to a 300 ohm cable for a given power (by a factor of the sqrt(300/50), or about 2.5) . Power lost due to I2R losses vary in proportion to the square of the current (obviously), so for a given effective resistance in the conductors, a 50 ohm cable would have 6 times greater I2R losses than a 300 ohm cable. But like Ron said, the conductor sizes are typically smaller in a 300 ohm twin lead cable (as compared to, say, 7/8 Heliax), so at some point you start getting into comparing apples and oranges... Maybe it is because of the larger C coupling in the coax due to the larger surface area of the shield. Coax has a lower R even with skin effect than twin line feeders. Again, it depends on the size of the conductors. It's not a valid statement that all 300 ohm balanced lines have lower loss than 50 ohm coax. But if you want to compare the two cables at approximately the same size (say, the diameter of the coax is equal to the width of the twin-lead), then the balanced line is probably going to be the winner in the loss department at VHF. Skin affect is a factor, but a small one compared to the LC factor. Please define the LC factor. --- Jeff Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. Yahoo! Groups Links
