Avionics-List Digest Archive

Tue 07/10/07


Total Messages Posted: 3



Today's Message Index:
----------------------
 
     1. 11:38 AM - Re: Need Comm Troubleshooting Advice (Perry, Phil)
     2. 07:04 PM - Re: Need Comm Troubleshooting Advice (Roger Roy)
     3. 10:42 PM - Re: Need Comm Troubleshooting Advice (John Rippengal)
 
 
 


Message 1


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    Time: 11:38:19 AM PST US
    Subject: Need Comm Troubleshooting Advice
    From: "Perry, Phil" <Phil.Perry@netapp.com>
    I agree with John. The bird meters are great but they're just a company who built the watt/swr meters. They've been around for years and are not manufactured any more. and are more of a novelty for hard-core radio operators to own. There are certainly many modern meters out there that are less expensive and more available. The $20 radio shack model is fine. Here's some a few tips that you can squirrel away for the next time you need to do some tuning. First, make sure the antenna is properly grounded to the aircraft. Several people will ground the antenna to a painted surface, this is a bad idea! The paint/primer acts as an insulator and the antenna won't be able to balance the ground plane (aircraft) with the transmitting element (antenna). If you don't have a good ground, you will pull your hair out trying to tune the antenna and it won't work very well anyway. Checking grounding is always a great place to start. Next, you'll need to tune your antenna to the appropriate length. The frequency range determines the length of the antenna. The lower the frequency; the longer the antenna. The higher the frequency; the shorter the antenna. This is because low frequencies have longer wave lengths and higher frequencies have shorter wave lengths. Since we're dealing with frequencies in the VHF band (108Mhz - 137Mhz), we're dealing with fairly short antenna lengths. Keep in mind that an antenna is tuned EXACTLY for only one frequency. As you deviate (up or down) from that frequency, the antenna becomes out of tune. The further your deviation, the less in-tune the antenna will be. So you will want to tune for a frequency that is in the middle of your transmit range. Since 108Mhz - 112Mhz are receive-only NAV frequencies, we aren't too concerned in tuning for those frequencies. Since 112Mhz - 136Mhz is the range of communication frequencies that we transmit on, you want to tune for those. So pick a frequency in the middle and make that the frequency you tune for. In this case, 124Mhz is exactly in the middle of 108Mhz and 136Mhz. If you tune for 124Mhz, the antenna will be a perfect match at 124Mhz and only slightly off at the extreme edges of your transmitting frequency range 112Mhz and 136Mhz. Let's stop right here for a minute and talk about Standing Wave Ratios or SWR. When a transmitter is keyed, a signal is obviously transmitted down the coax and ultimately destined for the antenna to broadcast. In a perfect world (or a perfectly tuned antenna) all of the signal power from the transmitter is radiated by the antenna. So if you have a transmitter that is radiating 25watts of signal power, all 25 watts exit the antenna and is radiated out in space for others to hear. But what happens if the antenna isn't tuned perfectly? Actually the signal will traverse the coax and reach the antenna. But since the antenna isn't the appropriate length only a portion of the wave (signal) will be radiated. The portion that isn't radiated is reflected back down the coax and toward the transmitter. (YIKES!) Transmitters are made to transmit 25 watt signals, not have them blasted back down the coax like a fire hose. The ratio of signal that is radiated by the transmitter vs the amount reflected by the antenna is referred to as the Standing Wave Ratio (SWR). In the perfect situation your standing wave ratio should be 1 to 1 (presented as 1:1). This means that all of your power is being radiated and there is no reflective wave coming back to the transmitter. So it's important to tune for the best SWR because: 1) You want as much of your signal to leave the antenna and be radiated for the rest of the world to receive and 2) Excessive reflected waves WILL RUIN your transmitter. So lets tune our antenna. Install it like the manufacture suggests and put a SWR/Watt meter inline with the coax. (The closer to the transmitter, the better) If you have a low-power option on your radio, select it. The least amount of power you can use, the better. This will keep the reflected signals to a minimum, while the antenna still isn't correctly tuned. Not to mention you'll be less likely to interrupt a frequency that's in use. Dial up 124Mhz and make sure the frequency isn't in use! If it is, just change to another unused frequency nearby. Now it's time to check the SWR. Key the transmitter and check your reading on the meter. (You'll need to follow the directions that came with your meter on how to set it up. I can't go through the setup procedure for your meter, but I promise. It's not complicated!) Measure your SWR. If you see 1:1, you're lucky! More than likely, you won't. You might see something like 1.7:1 or 2:1 or worse. So how do you figure out if you have to lengthen or shorten your antenna? It's pretty simple, trial and error. Most antennas have a set screw that you can loose and adjust then antenna length. First try lengthening the antenna by 1/4 inch and re-checking your SWR. Did it improve or did it get worse? If it got worse, try the other direction and shorten the antenna by 1/4 inch. If it got better, try lengthening it a hair more. It's a good idea to keep track of each adjustment on a piece of paper, so you can get an idea of how each change is affecting your SWR. This will help you zero in on that perfect length. As you get closer and closer to 1:1, you're adjustments need to be refined with smaller increments. Don't be surprised is you can't get exactly 1:1. The transmitted waves can be reflected back toward the antenna by metal (such as your empennage). So when you tune your antenna, get it away from metal buildings or other structures and tune for the best available SWR at 124Mhz. You want the signal to be as unaffected as possible. If you can get it down to 1.1:1 or 1.2:1, you're doing great! I wouldn't be happy with anything over 1.5:1. 1.5 is my personal minimum and it's easy to obtain. Once you think you've tuned your antenna for 124 Mhz, you need to check the extreme edges of your transmit range. Dial down to 112 Mhz. Once again, make sure you won't be interrupting anyone. Check your SWR. It will be higher than it was at 124 Mhz, because at 112Mhz the antenna is slightly out of tune. But if your inside 1.5:1, you're good. I'd be okay with 1.7:1 on the extreme edges. Next dial up 136Mhz and give it a shot. Once again, make sure no one is using the frequency. I'm okay with 1.7ish:1 up there too. Antenna problems really aren't that complex or difficult to tune. A little practice and you'll have it in no time. A couple of other things. 1) Make sure you use the correct coax. Usually 50 Ohm and don't buy the cheap stuff!! Radio shack and other retailers have cheap coax. I am a fan of Belden RG58-A/U coax. It has relatively low loss at the cable lengths required for an airplane, the center conductor is braided (important for high vibration installations), it has a very good braided external conductor (Most cheap cables will skimp here), and it has a solid inner-core insulator. Nearly any Amateur Radio (Ham) store will carry Belden Cable. If you can't find it, I know aesham.com carries it. The coax is the only thing between your transmitter and your antenna, make sure you use good cable! It's worth a couple of extra dollars. 2) If you suspect a cable issue or short in the cable, disconnect the cable from both the transmitter and the antenna. Use a continuity meter and check to make sure you have continuity through the center conductor. Same thing for the external braided conductor, check it. If you've got continuity all the way through, you've eliminated the possibility of a broken wire. Next check and see if you have continuity from the center conductor to the external conductor. If you do, there's a problem. Either your cable has a short or you've got a connector that isn't soldered on properly. Check the connectors first be re-soldering them. If that doesn't fix it, you need a new cable. Finally, if you're still having problems, check your connectors. Make sure the solder joints are good. Your continuity can be fine, but if you've got a cold solder joint, that can cause problems. Please don't use the cheap retail connectors, they're junk. Get good quality connectors. If you can find silver connectors, they are the best and are the easiest for solder to stick to. I use the ones made by Amphenol. If you're gonna get the good coax, make sure you get the good connectors too! Most places that sell Belden also sells Amphenol connectors. I know aesham.com has them too, but it's been several years since I've had to place and order with them. I'm sure they still carry both brands. Anyway, that's all I can think of. Hopefully you'll tuck this stuff away somewhere and use it one day. Otherwise,the delete button looks like a red "X" at the top of the screen. :) Take care, Phil ________________________________ From: John Rippengal [mailto:j.rippengal@cytanet.com.cy] Sent: Tuesday, July 03, 2007 2:00 PM Subject: Re: Avionics-List: Need Comm Troubleshooting Advice Glad it seems to be ok now Roger. An aircraft standing around for quite a time while a new avionics pack is being fitted is a good clue to there being a flat battery. However the other advice given to you to check with a VSWR meter is a good one. The Bird Thru' Line meter is a sort of Rolls Royce professional type and you really don't need that for a good check on your antenna/coax/connector setup. Try Radio Shack or similar for a cheap VSWR meter that covers the 2 metre amateur band. Should only cost about $20 or less and every home installer of avionics should have one. It will give you confidence in the antenna installation together with the feeders and connectors. John From: Roger Roy <mailto:Savannah174@msn.com> Hi John, How's the avionics guru? I did as you suggested and put my battery charger on the battery and all seem to workload and clear. I was unable to had another person TX with the portable I will check this out tomorrow, again thank you, Cheers RJ From: John Rippengal <mailto:j.rippengal@cytanet.com.cy> Roger, What are the battery volts when you switch the equipment on?? The fault is common to both comms so suspect something common like the battery. You should check the equipment with the battery on charge and a battery voltage of about 14v WITH the equipment switched on. John


    Message 2


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    Time: 07:04:52 PM PST US
    From: "Roger Roy" <Savannah174@msn.com>
    Subject: Re: Need Comm Troubleshooting Advice
    Hi Phil, Thanks for the step by step use of the SWR meter. I would like to check my VHF antenna and the RG-400 cable installed in my aircraft but was wondering how I would accomplish this task, I at least have a guide, Cheers Regards, RJ Roy ----- Original Message ----- From: Perry, Phil<mailto:Phil.Perry@netapp.com> To: avionics-list@matronics.com<mailto:avionics-list@matronics.com> Sent: Tuesday, July 10, 2007 2:34 PM Subject: RE: Avionics-List: Need Comm Troubleshooting Advice I agree with John. The bird meters are great but they're just a company who built the watt/swr meters. They've been around for years and are not manufactured any more. and are more of a novelty for hard-core radio operators to own. There are certainly many modern meters out there that are less expensive and more available. The $20 radio shack model is fine. Here's some a few tips that you can squirrel away for the next time you need to do some tuning. First, make sure the antenna is properly grounded to the aircraft. Several people will ground the antenna to a painted surface, this is a bad idea! The paint/primer acts as an insulator and the antenna won't be able to balance the ground plane (aircraft) with the transmitting element (antenna). If you don't have a good ground, you will pull your hair out trying to tune the antenna and it won't work very well anyway. Checking grounding is always a great place to start. Next, you'll need to tune your antenna to the appropriate length. The frequency range determines the length of the antenna. The lower the frequency; the longer the antenna. The higher the frequency; the shorter the antenna. This is because low frequencies have longer wave lengths and higher frequencies have shorter wave lengths. Since we're dealing with frequencies in the VHF band (108Mhz - 137Mhz), we're dealing with fairly short antenna lengths. Keep in mind that an antenna is tuned EXACTLY for only one frequency. As you deviate (up or down) from that frequency, the antenna becomes out of tune. The further your deviation, the less in-tune the antenna will be. So you will want to tune for a frequency that is in the middle of your transmit range. Since 108Mhz - 112Mhz are receive-only NAV frequencies, we aren't too concerned in tuning for those frequencies. Since 112Mhz - 136Mhz is the range of communication frequencies that we transmit on, you want to tune for those. So pick a frequency in the middle and make that the frequency you tune for. In this case, 124Mhz is exactly in the middle of 108Mhz and 136Mhz. If you tune for 124Mhz, the antenna will be a perfect match at 124Mhz and only slightly off at the extreme edges of your transmitting frequency range 112Mhz and 136Mhz. Let's stop right here for a minute and talk about Standing Wave Ratios or SWR. When a transmitter is keyed, a signal is obviously transmitted down the coax and ultimately destined for the antenna to broadcast. In a perfect world (or a perfectly tuned antenna) all of the signal power from the transmitter is radiated by the antenna. So if you have a transmitter that is radiating 25watts of signal power, all 25 watts exit the antenna and is radiated out in space for others to hear. But what happens if the antenna isn't tuned perfectly? Actually the signal will traverse the coax and reach the antenna. But since the antenna isn't the appropriate length only a portion of the wave (signal) will be radiated. The portion that isn't radiated is reflected back down the coax and toward the transmitter. (YIKES!) Transmitters are made to transmit 25 watt signals, not have them blasted back down the coax like a fire hose. The ratio of signal that is radiated by the transmitter vs the amount reflected by the antenna is referred to as the Standing Wave Ratio (SWR). In the perfect situation your standing wave ratio should be 1 to 1 (presented as 1:1). This means that all of your power is being radiated and there is no reflective wave coming back to the transmitter. So it's important to tune for the best SWR because: 1) You want as much of your signal to leave the antenna and be radiated for the rest of the world to receive and 2) Excessive reflected waves WILL RUIN your transmitter. So lets tune our antenna. Install it like the manufacture suggests and put a SWR/Watt meter inline with the coax. (The closer to the transmitter, the better) If you have a low-power option on your radio, select it. The least amount of power you can use, the better. This will keep the reflected signals to a minimum, while the antenna still isn't correctly tuned. Not to mention you'll be less likely to interrupt a frequency that's in use. Dial up 124Mhz and make sure the frequency isn't in use! If it is, just change to another unused frequency nearby. Now it's time to check the SWR. Key the transmitter and check your reading on the meter. (You'll need to follow the directions that came with your meter on how to set it up. I can't go through the setup procedure for your meter, but I promise. It's not complicated!) Measure your SWR. If you see 1:1, you're lucky! More than likely, you won't. You might see something like 1.7:1 or 2:1 or worse. So how do you figure out if you have to lengthen or shorten your antenna? It's pretty simple, trial and error. Most antennas have a set screw that you can loose and adjust then antenna length. First try lengthening the antenna by 1/4 inch and re-checking your SWR. Did it improve or did it get worse? If it got worse, try the other direction and shorten the antenna by 1/4 inch. If it got better, try lengthening it a hair more. It's a good idea to keep track of each adjustment on a piece of paper, so you can get an idea of how each change is affecting your SWR. This will help you zero in on that perfect length. As you get closer and closer to 1:1, you're adjustments need to be refined with smaller increments. Don't be surprised is you can't get exactly 1:1. The transmitted waves can be reflected back toward the antenna by metal (such as your empennage). So when you tune your antenna, get it away from metal buildings or other structures and tune for the best available SWR at 124Mhz. You want the signal to be as unaffected as possible. If you can get it down to 1.1:1 or 1.2:1, you're doing great! I wouldn't be happy with anything over 1.5:1. 1.5 is my personal minimum and it's easy to obtain. Once you think you've tuned your antenna for 124 Mhz, you need to check the extreme edges of your transmit range. Dial down to 112 Mhz. Once again, make sure you won't be interrupting anyone. Check your SWR. It will be higher than it was at 124 Mhz, because at 112Mhz the antenna is slightly out of tune. But if your inside 1.5:1, you're good. I'd be okay with 1.7:1 on the extreme edges. Next dial up 136Mhz and give it a shot. Once again, make sure no one is using the frequency. I'm okay with 1.7ish:1 up there too. Antenna problems really aren't that complex or difficult to tune. A little practice and you'll have it in no time. A couple of other things. 1) Make sure you use the correct coax. Usually 50 Ohm and don't buy the cheap stuff!! Radio shack and other retailers have cheap coax. I am a fan of Belden RG58-A/U coax. It has relatively low loss at the cable lengths required for an airplane, the center conductor is braided (important for high vibration installations), it has a very good braided external conductor (Most cheap cables will skimp here), and it has a solid inner-core insulator. Nearly any Amateur Radio (Ham) store will carry Belden Cable. If you can't find it, I know aesham.com carries it. The coax is the only thing between your transmitter and your antenna, make sure you use good cable! It's worth a couple of extra dollars. 2) If you suspect a cable issue or short in the cable, disconnect the cable from both the transmitter and the antenna. Use a continuity meter and check to make sure you have continuity through the center conductor. Same thing for the external braided conductor, check it. If you've got continuity all the way through, you've eliminated the possibility of a broken wire. Next check and see if you have continuity from the center conductor to the external conductor. If you do, there's a problem. Either your cable has a short or you've got a connector that isn't soldered on properly. Check the connectors first be re-soldering them. If that doesn't fix it, you need a new cable. Finally, if you're still having problems, check your connectors. Make sure the solder joints are good. Your continuity can be fine, but if you've got a cold solder joint, that can cause problems. Please don't use the cheap retail connectors, they're junk. Get good quality connectors. If you can find silver connectors, they are the best and are the easiest for solder to stick to. I use the ones made by Amphenol. If you're gonna get the good coax, make sure you get the good connectors too! Most places that sell Belden also sells Amphenol connectors. I know aesham.com has them too, but it's been several years since I've had to place and order with them. I'm sure they still carry both brands. Anyway, that's all I can think of. Hopefully you'll tuck this stuff away somewhere and use it one day. Otherwise,the delete button looks like a red "X" at the top of the screen. :) Take care, Phil ------------------------------------------------------------------------- ----- From: John Rippengal [mailto:j.rippengal@cytanet.com.cy] Sent: Tuesday, July 03, 2007 2:00 PM To: avionics-list@matronics.com Subject: Re: Avionics-List: Need Comm Troubleshooting Advice Glad it seems to be ok now Roger. An aircraft standing around for quite a time while a new avionics pack is being fitted is a good clue to there being a flat battery. However the other advice given to you to check with a VSWR meter is a good one. The Bird Thru' Line meter is a sort of Rolls Royce professional type and you really don't need that for a good check on your antenna/coax/connector setup. Try Radio Shack or similar for a cheap VSWR meter that covers the 2 metre amateur band. Should only cost about $20 or less and every home installer of avionics should have one. It will give you confidence in the antenna installation together with the feeders and connectors. John From: Roger Roy<mailto:Savannah174@msn.com> Hi John, How's the avionics guru? I did as you suggested and put my battery charger on the battery and all seem to workload and clear. I was unable to had another person TX with the portable I will check this out tomorrow, again thank you, Cheers RJ From: John Rippengal<mailto:j.rippengal@cytanet.com.cy> Roger, What are the battery volts when you switch the equipment on?? The fault is common to both comms so suspect something common like the battery. You should check the equipment with the battery on charge and a battery voltage of about 14v WITH the equipment switched on. John href="http://www.matronics.com/Navigator?Avionics-List">http://www.matr onics.com/Navigator?Avionics-List href="http://forums.matronics.com">http://forums.matronics.com http://www.matronics.com/Navigator?Avionics-List<http://www.matronics.com /Navigator?Avionics-List>


    Message 3


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    Time: 10:42:01 PM PST US
    From: "John Rippengal" <j.rippengal@cytanet.com.cy>
    Subject: Re: Need Comm Troubleshooting Advice
    Yes but Phil the low edge of the band is 118Mhz NOT 112 Mhz so the centre frequrency is 127 not 124. Second I would most certainly not bother tuning a broadband antenna. Assuming it is a professionally made antenna or something like Jim Weir's tape antenna then there is no point whatever in tuning it. Just check that the VSWR stays between 2:1 max over the range - it should be closer to 1:1.5 over most of the band - but the main idea is to check that there is no fault in the coax or connectors in which case you would see figures way over the 2:1. John From: Perry, Phil I agree with John. The bird meters are great but they're just a company who built the watt/swr meters. They've been around for years and are not manufactured any more. and are more of a novelty for hard-core radio operators to own. There are certainly many modern meters out there that are less expensive and more available. The $20 radio shack model is fine. Here's some a few tips that you can squirrel away for the next time you need to do some tuning. First, make sure the antenna is properly grounded to the aircraft. Several people will ground the antenna to a painted surface, this is a bad idea! The paint/primer acts as an insulator and the antenna won't be able to balance the ground plane (aircraft) with the transmitting element (antenna). If you don't have a good ground, you will pull your hair out trying to tune the antenna and it won't work very well anyway. Checking grounding is always a great place to start. Next, you'll need to tune your antenna to the appropriate length. The frequency range determines the length of the antenna. The lower the frequency; the longer the antenna. The higher the frequency; the shorter the antenna. This is because low frequencies have longer wave lengths and higher frequencies have shorter wave lengths. Since we're dealing with frequencies in the VHF band (108Mhz - 137Mhz), we're dealing with fairly short antenna lengths. Keep in mind that an antenna is tuned EXACTLY for only one frequency. As you deviate (up or down) from that frequency, the antenna becomes out of tune. The further your deviation, the less in-tune the antenna will be. So you will want to tune for a frequency that is in the middle of your transmit range. Since 108Mhz - 112Mhz are receive-only NAV frequencies, we aren't too concerned in tuning for those frequencies. Since 112Mhz - 136Mhz is the range of communication frequencies that we transmit on, you want to tune for those. So pick a frequency in the middle and make that the frequency you tune for. In this case, 124Mhz is exactly in the middle of 108Mhz and 136Mhz. If you tune for 124Mhz, the antenna will be a perfect match at 124Mhz and only slightly off at the extreme edges of your transmitting frequency range 112Mhz and 136Mhz. Let's stop right here for a minute and talk about Standing Wave Ratios or SWR. When a transmitter is keyed, a signal is obviously transmitted down the coax and ultimately destined for the antenna to broadcast. In a perfect world (or a perfectly tuned antenna) all of the signal power from the transmitter is radiated by the antenna. So if you have a transmitter that is radiating 25watts of signal power, all 25 watts exit the antenna and is radiated out in space for others to hear. But what happens if the antenna isn't tuned perfectly? Actually the signal will traverse the coax and reach the antenna. But since the antenna isn't the appropriate length only a portion of the wave (signal) will be radiated. The portion that isn't radiated is reflected back down the coax and toward the transmitter. (YIKES!) Transmitters are made to transmit 25 watt signals, not have them blasted back down the coax like a fire hose. The ratio of signal that is radiated by the transmitter vs the amount reflected by the antenna is referred to as the Standing Wave Ratio (SWR). In the perfect situation your standing wave ratio should be 1 to 1 (presented as 1:1). This means that all of your power is being radiated and there is no reflective wave coming back to the transmitter. So it's important to tune for the best SWR because: 1) You want as much of your signal to leave the antenna and be radiated for the rest of the world to receive and 2) Excessive reflected waves WILL RUIN your transmitter. So lets tune our antenna. Install it like the manufacture suggests and put a SWR/Watt meter inline with the coax. (The closer to the transmitter, the better) If you have a low-power option on your radio, select it. The least amount of power you can use, the better. This will keep the reflected signals to a minimum, while the antenna still isn't correctly tuned. Not to mention you'll be less likely to interrupt a frequency that's in use. Dial up 124Mhz and make sure the frequency isn't in use! If it is, just change to another unused frequency nearby. Now it's time to check the SWR. Key the transmitter and check your reading on the meter. (You'll need to follow the directions that came with your meter on how to set it up. I can't go through the setup procedure for your meter, but I promise. It's not complicated!) Measure your SWR. If you see 1:1, you're lucky! More than likely, you won't. You might see something like 1.7:1 or 2:1 or worse. So how do you figure out if you have to lengthen or shorten your antenna? It's pretty simple, trial and error. Most antennas have a set screw that you can loose and adjust then antenna length. First try lengthening the antenna by 1/4 inch and re-checking your SWR. Did it improve or did it get worse? If it got worse, try the other direction and shorten the antenna by 1/4 inch. If it got better, try lengthening it a hair more. It's a good idea to keep track of each adjustment on a piece of paper, so you can get an idea of how each change is affecting your SWR. This will help you zero in on that perfect length. As you get closer and closer to 1:1, you're adjustments need to be refined with smaller increments. Don't be surprised is you can't get exactly 1:1. The transmitted waves can be reflected back toward the antenna by metal (such as your empennage). So when you tune your antenna, get it away from metal buildings or other structures and tune for the best available SWR at 124Mhz. You want the signal to be as unaffected as possible. If you can get it down to 1.1:1 or 1.2:1, you're doing great! I wouldn't be happy with anything over 1.5:1. 1.5 is my personal minimum and it's easy to obtain. Once you think you've tuned your antenna for 124 Mhz, you need to check the extreme edges of your transmit range. Dial down to 112 Mhz. Once again, make sure you won't be interrupting anyone. Check your SWR. It will be higher than it was at 124 Mhz, because at 112Mhz the antenna is slightly out of tune. But if your inside 1.5:1, you're good. I'd be okay with 1.7:1 on the extreme edges. Next dial up 136Mhz and give it a shot. Once again, make sure no one is using the frequency. I'm okay with 1.7ish:1 up there too. Antenna problems really aren't that complex or difficult to tune. A little practice and you'll have it in no time. A couple of other things. 1) Make sure you use the correct coax. Usually 50 Ohm and don't buy the cheap stuff!! Radio shack and other retailers have cheap coax. I am a fan of Belden RG58-A/U coax. It has relatively low loss at the cable lengths required for an airplane, the center conductor is braided (important for high vibration installations), it has a very good braided external conductor (Most cheap cables will skimp here), and it has a solid inner-core insulator. Nearly any Amateur Radio (Ham) store will carry Belden Cable. If you can't find it, I know aesham.com carries it. The coax is the only thing between your transmitter and your antenna, make sure you use good cable! It's worth a couple of extra dollars. 2) If you suspect a cable issue or short in the cable, disconnect the cable from both the transmitter and the antenna. Use a continuity meter and check to make sure you have continuity through the center conductor. Same thing for the external braided conductor, check it. If you've got continuity all the way through, you've eliminated the possibility of a broken wire. Next check and see if you have continuity from the center conductor to the external conductor. If you do, there's a problem. Either your cable has a short or you've got a connector that isn't soldered on properly. Check the connectors first be re-soldering them. If that doesn't fix it, you need a new cable. Finally, if you're still having problems, check your connectors. Make sure the solder joints are good. Your continuity can be fine, but if you've got a cold solder joint, that can cause problems. Please don't use the cheap retail connectors, they're junk. Get good quality connectors. If you can find silver connectors, they are the best and are the easiest for solder to stick to. I use the ones made by Amphenol. If you're gonna get the good coax, make sure you get the good connectors too! Most places that sell Belden also sells Amphenol connectors. I know aesham.com has them too, but it's been several years since I've had to place and order with them. I'm sure they still carry both brands. Anyway, that's all I can think of. Hopefully you'll tuck this stuff away somewhere and use it one day. Otherwise,the delete button looks like a red "X" at the top of the screen. :) Take care, Phil ------------------------------------------------------------------------- ----- From: John Rippengal [mailto:j.rippengal@cytanet.com.cy] Sent: Tuesday, July 03, 2007 2:00 PM To: avionics-list@matronics.com Subject: Re: Avionics-List: Need Comm Troubleshooting Advice Glad it seems to be ok now Roger. An aircraft standing around for quite a time while a new avionics pack is being fitted is a good clue to there being a flat battery. However the other advice given to you to check with a VSWR meter is a good one. The Bird Thru' Line meter is a sort of Rolls Royce professional type and you really don't need that for a good check on your antenna/coax/connector setup. Try Radio Shack or similar for a cheap VSWR meter that covers the 2 metre amateur band. Should only cost about $20 or less and every home installer of avionics should have one. It will give you confidence in the antenna installation together with the feeders and connectors. John From: Roger Roy Hi John, How's the avionics guru? I did as you suggested and put my battery charger on the battery and all seem to workload and clear. I was unable to had another person TX with the portable I will check this out tomorrow, again thank you, Cheers RJ From: John Rippengal Roger, What are the battery volts when you switch the equipment on?? The fault is common to both comms so suspect something common like the battery. You should check the equipment with the battery on charge and a battery voltage of about 14v WITH the equipment switched on. John href="http://www.matronics.com/Navigator?Avionics-List">http://www.matr onics.com/Navigator?Avionics-List href="http://forums.matronics.com">http://forums.matronics.com




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