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I used my HTX-252 for the first time last weekend, and was
told that the audio was muffled although intelligible. Anyone know of a cure for this muffled effect? Cal- I also have one of the bargain HTX-252 transceivers. I had read here about the low audio and expected that would be a problem for me as well. What I found was that the radio has no microphone gain adjustment, just a peak deviation adjustment, as has been discussed here. Checking modulation, I found that it was working well with no further adjustment needed. It is just set up to REQUIRE close talking to the microphone, and some people prefer to hold it several inches away. The microphone element is located at the top front of the microphone, so holding that spot within an inch of your mouth should give good modulation without having to shout. During my testing I tried a couple other similar microphone elements with no increase in sensitivity. The only reason I can think of that would cause muffled audio, would be if someone had gone into either the microphone or the transceiver's microphone amplifier circuits, and tried to "fix" it! If you recently purchased yours and it was the last one in the store, it is possible that it had been returned by a previous customer. As such, it might have a factory defect, or it might have been returned because of the failed attempt at improving it. Either way, your best bet may be to take it back to a Radio Shack store along with the receipt, and have them send it in for repair. I believe their technicians have seen most of the problems many times, and should make fast work of a repair. Per someone's suggestion here, I found service information for the Albrecht AE-540 at http://www.albrecht-electronic.de/se...eurfunk/AE540/ which appears to be almost exactly the same as the HTX-252. Following the microphone audio path, there is a 2200 Ohm resistor that leads to the push-to-talk circuit. That circuit is AC coupled by a 0.1 microfarad capacitor, to another 2200 Ohm resister, that connects to the audio processor integrated circuit. I believe some increase in microphone gain would be achieved if that second 2200 Ohm resistor were shorted. However, the frequency response might also be affected. As a wild guess, I would look on the bottom side of the main circuit board for that 2200 Ohm resistor. It is located near a shield as I recall. If you find it has been shorted, try un-shorting it and see if the audio improves. By the way, I also checked www.mods.dk and found a suggestion to remove a certain one microfarad capacitor to speed-up the radio's squelch response. I decided that it was a better idea to replace it with a 0.1 microfarad capacitor. As far as I can tell, that is the only worthwhile modification the radio needs. 73, Fred, K4DII |
"Muffled" HTX-252 Transmitted Audio
I used my HTX-252 for the first time last weekend, and was
told that the audio was muffled although intelligible. Anyone know of a cure for this muffled effect? Cal- I also have one of the bargain HTX-252 transceivers. I had read here about the low audio and expected that would be a problem for me as well. What I found was that the radio has no microphone gain adjustment, just a peak deviation adjustment, as has been discussed here. Checking modulation, I found that it was working well with no further adjustment needed. It is just set up to REQUIRE close talking to the microphone, and some people prefer to hold it several inches away. The microphone element is located at the top front of the microphone, so holding that spot within an inch of your mouth should give good modulation without having to shout. During my testing I tried a couple other similar microphone elements with no increase in sensitivity. The only reason I can think of that would cause muffled audio, would be if someone had gone into either the microphone or the transceiver's microphone amplifier circuits, and tried to "fix" it! If you recently purchased yours and it was the last one in the store, it is possible that it had been returned by a previous customer. As such, it might have a factory defect, or it might have been returned because of the failed attempt at improving it. Either way, your best bet may be to take it back to a Radio Shack store along with the receipt, and have them send it in for repair. I believe their technicians have seen most of the problems many times, and should make fast work of a repair. Per someone's suggestion here, I found service information for the Albrecht AE-540 at http://www.albrecht-electronic.de/se...eurfunk/AE540/ which appears to be almost exactly the same as the HTX-252. Following the microphone audio path, there is a 2200 Ohm resistor that leads to the push-to-talk circuit. That circuit is AC coupled by a 0.1 microfarad capacitor, to another 2200 Ohm resister, that connects to the audio processor integrated circuit. I believe some increase in microphone gain would be achieved if that second 2200 Ohm resistor were shorted. However, the frequency response might also be affected. As a wild guess, I would look on the bottom side of the main circuit board for that 2200 Ohm resistor. It is located near a shield as I recall. If you find it has been shorted, try un-shorting it and see if the audio improves. By the way, I also checked www.mods.dk and found a suggestion to remove a certain one microfarad capacitor to speed-up the radio's squelch response. I decided that it was a better idea to replace it with a 0.1 microfarad capacitor. As far as I can tell, that is the only worthwhile modification the radio needs. 73, Fred, K4DII |
"Fred McKenzie" wrote in message ... I used my HTX-252 for the first time last weekend, and was told that the audio was muffled although intelligible. Anyone know of a cure for this muffled effect? Cal- I also have one of the bargain HTX-252 transceivers. I had read here about the low audio and expected that would be a problem for me as well. What I found was that the radio has no microphone gain adjustment, just a peak deviation adjustment, as has been discussed here. Checking modulation, I found that it was working well with no further adjustment needed. It is just set up to REQUIRE close talking to the microphone, and some people prefer to hold it several inches away. The microphone element is located at the top front of the microphone, so holding that spot within an inch of your mouth should give good modulation without having to shout. During my testing I tried a couple other similar microphone elements with no increase in sensitivity. The only reason I can think of that would cause muffled audio, would be if someone had gone into either the microphone or the transceiver's microphone amplifier circuits, and tried to "fix" it! If you recently purchased yours and it was the last one in the store, it is possible that it had been returned by a previous customer. As such, it might have a factory defect, or it might have been returned because of the failed attempt at improving it. Either way, your best bet may be to take it back to a Radio Shack store along with the receipt, and have them send it in for repair. I believe their technicians have seen most of the problems many times, and should make fast work of a repair. Per someone's suggestion here, I found service information for the Albrecht AE-540 at http://www.albrecht-electronic.de/se...eurfunk/AE540/ which appears to be almost exactly the same as the HTX-252. Following the microphone audio path, there is a 2200 Ohm resistor that leads to the push-to-talk circuit. That circuit is AC coupled by a 0.1 microfarad capacitor, to another 2200 Ohm resister, that connects to the audio processor integrated circuit. I believe some increase in microphone gain would be achieved if that second 2200 Ohm resistor were shorted. However, the frequency response might also be affected. As a wild guess, I would look on the bottom side of the main circuit board for that 2200 Ohm resistor. It is located near a shield as I recall. If you find it has been shorted, try un-shorting it and see if the audio improves. By the way, I also checked www.mods.dk and found a suggestion to remove a certain one microfarad capacitor to speed-up the radio's squelch response. I decided that it was a better idea to replace it with a 0.1 microfarad capacitor. As far as I can tell, that is the only worthwhile modification the radio needs. 73, Fred, K4DII Thanks for the tips on the 252... I'll store them for future use. I bought 2 of them brand new, never had them out of the box yet. I had set them aside awaiting to use them for a project, then found they weren't able to be used for it. Now too late to return them, as it was past 30 days. ALL have extended warranty. If anyone should be interested in one of them or both, I'll sell em for what I got in them plus shipping. L. |
"Fred McKenzie" wrote in message ... I used my HTX-252 for the first time last weekend, and was told that the audio was muffled although intelligible. Anyone know of a cure for this muffled effect? Cal- I also have one of the bargain HTX-252 transceivers. I had read here about the low audio and expected that would be a problem for me as well. What I found was that the radio has no microphone gain adjustment, just a peak deviation adjustment, as has been discussed here. Checking modulation, I found that it was working well with no further adjustment needed. It is just set up to REQUIRE close talking to the microphone, and some people prefer to hold it several inches away. The microphone element is located at the top front of the microphone, so holding that spot within an inch of your mouth should give good modulation without having to shout. During my testing I tried a couple other similar microphone elements with no increase in sensitivity. The only reason I can think of that would cause muffled audio, would be if someone had gone into either the microphone or the transceiver's microphone amplifier circuits, and tried to "fix" it! If you recently purchased yours and it was the last one in the store, it is possible that it had been returned by a previous customer. As such, it might have a factory defect, or it might have been returned because of the failed attempt at improving it. Either way, your best bet may be to take it back to a Radio Shack store along with the receipt, and have them send it in for repair. I believe their technicians have seen most of the problems many times, and should make fast work of a repair. Per someone's suggestion here, I found service information for the Albrecht AE-540 at http://www.albrecht-electronic.de/se...eurfunk/AE540/ which appears to be almost exactly the same as the HTX-252. Following the microphone audio path, there is a 2200 Ohm resistor that leads to the push-to-talk circuit. That circuit is AC coupled by a 0.1 microfarad capacitor, to another 2200 Ohm resister, that connects to the audio processor integrated circuit. I believe some increase in microphone gain would be achieved if that second 2200 Ohm resistor were shorted. However, the frequency response might also be affected. As a wild guess, I would look on the bottom side of the main circuit board for that 2200 Ohm resistor. It is located near a shield as I recall. If you find it has been shorted, try un-shorting it and see if the audio improves. By the way, I also checked www.mods.dk and found a suggestion to remove a certain one microfarad capacitor to speed-up the radio's squelch response. I decided that it was a better idea to replace it with a 0.1 microfarad capacitor. As far as I can tell, that is the only worthwhile modification the radio needs. 73, Fred, K4DII Thanks for the tips on the 252... I'll store them for future use. I bought 2 of them brand new, never had them out of the box yet. I had set them aside awaiting to use them for a project, then found they weren't able to be used for it. Now too late to return them, as it was past 30 days. ALL have extended warranty. If anyone should be interested in one of them or both, I'll sell em for what I got in them plus shipping. L. |
muffled? Don't know about that one.
I just cranked rv2 1/2 turn then backed off the dtmf pot in the mike so the tones were clear and all my audio reports are "sounds Marvelous" I use It as my Primary NCS Radio KC*VIF Greg Z to thine own sound be true |
muffled? Don't know about that one.
I just cranked rv2 1/2 turn then backed off the dtmf pot in the mike so the tones were clear and all my audio reports are "sounds Marvelous" I use It as my Primary NCS Radio KC*VIF Greg Z to thine own sound be true |
greg z wrote:
: muffled? Don't know about that one. : I just cranked rv2 1/2 turn then backed off the dtmf pot in the mike : so the tones were clear and all my audio reports are : "sounds Marvelous" : I use It as my Primary NCS Radio I have one too. I adjusted the pot on the motherboard and still got poor audio reports. I kept asking and finally got what I hope is a better understanding of what it sounds like. What most folks are calling "muffled" may actually be a high bass response (or a low high end response) Asking hams for opionions on audio quality is dubious at best. I've heard a mobile fade almost completely out and get a report of "You're starting to break up" more times than I can count. The same with audio quality. Many hams don't listen that well, and as long as they can hear and understand you then you "sound great" Richard in Boston, MA, USA N1JDU |
greg z wrote:
: muffled? Don't know about that one. : I just cranked rv2 1/2 turn then backed off the dtmf pot in the mike : so the tones were clear and all my audio reports are : "sounds Marvelous" : I use It as my Primary NCS Radio I have one too. I adjusted the pot on the motherboard and still got poor audio reports. I kept asking and finally got what I hope is a better understanding of what it sounds like. What most folks are calling "muffled" may actually be a high bass response (or a low high end response) Asking hams for opionions on audio quality is dubious at best. I've heard a mobile fade almost completely out and get a report of "You're starting to break up" more times than I can count. The same with audio quality. Many hams don't listen that well, and as long as they can hear and understand you then you "sound great" Richard in Boston, MA, USA N1JDU |
I have one too. I adjusted the pot on the motherboard and still got poor
audio reports. I kept asking and finally got what I hope is a better understanding of what it sounds like. Richard in Boston, MA, USA N1JDU ------------------------------ Seriously Richard my 252 sounds great !!!! I've listened to it myself. The key for me was to get the pot up, hold mike 3.5'' away at a 45deg.angle and to remember the element is near the top of the mike. The tough part is getting used to talking on each radio a little differently. A ht with a good pair of hi-fi cans monitoring the input or simplex is a great tool in getting this one down. Many schematics for simple, easy to build deviation meters are to be had on the web. KC*VIF Greg Z to thine own sound be true |
I have one too. I adjusted the pot on the motherboard and still got poor
audio reports. I kept asking and finally got what I hope is a better understanding of what it sounds like. Richard in Boston, MA, USA N1JDU ------------------------------ Seriously Richard my 252 sounds great !!!! I've listened to it myself. The key for me was to get the pot up, hold mike 3.5'' away at a 45deg.angle and to remember the element is near the top of the mike. The tough part is getting used to talking on each radio a little differently. A ht with a good pair of hi-fi cans monitoring the input or simplex is a great tool in getting this one down. Many schematics for simple, easy to build deviation meters are to be had on the web. KC*VIF Greg Z to thine own sound be true |
I'd like to thank everyone who responded to my inquiry regarding the "muffled"
transmit audio on my HTX-252! There is a lot of very useful information among those responses. I think I'll try listening to myself first. FWIW, I'd bought the rig used, and, not being a 2M FM guy, only used it this past weekend on a trip to my 45th high school reunion. The report came from a guy I'd known in high school. Again, thank you all! 73 Cal K4JSI |
I'd like to thank everyone who responded to my inquiry regarding the "muffled"
transmit audio on my HTX-252! There is a lot of very useful information among those responses. I think I'll try listening to myself first. FWIW, I'd bought the rig used, and, not being a 2M FM guy, only used it this past weekend on a trip to my 45th high school reunion. The report came from a guy I'd known in high school. Again, thank you all! 73 Cal K4JSI |
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I'd like to be able to run the line
out audio from a scanner into the sound card and be able to display the audio envelope. The amplitude scale wouldn't need to be calibrated as long as I could count the number of divisions, I could compare the peak deviation from the 252 to other signals on the air. A quick and dirty deviation comparison checker. Mike- I have an old Heath deviation meter that uses a peak-reading meter to display deviation. It was necessary to calibrate it using the "Bessell null method" using a signal generator with sine-wave FM modulation. The signal is received on an SSB receiver with a fairly sharp filter. Modulation is adjusted for a carrier null, and the deviation is obtained from a table of bessell functions, based on the ratio of modulating frequency to peak deviation. This method is outlined in some ARRL publications that cover VHF-FM techniques. What you describe is very close to how other deviation meters work. They receive a signal, convert it to an intermediate frequency, FM detect and display the detector output on an oscilloscope. It is a lot easier to calibrate this kind of meter, since you only have to offset the transmitter's frequency by plus and minus one KHz increments, and adjust the oscilloscope to display the correct offset. Using a deviation meter, it is normal to use some loud sound such as whistling directly across the microphone, to adjust a radio's peak deviation control for about 5 KHz. Then you adjust the radio's microphone amplifier so average speech runs around 3 KHz. I have a Turner desk mic connected to the 252 at the moment. I don't really know if It's an improvement or not. I built a little adapter box with 6 push button switches so I can control the radio, The problem with the HTX-252, is there is no microphone amplifier adjustment, and some people think it should work when speaking some distance away from the microphone. Your Turner microphone may provide the extra amplification needed to talk at a greater distance. While I won't tell someone they shouldn't do that, I can at least partly justify keeping the adjustment set for talking very close to the microphone. By close, I mean about a quarter inch or one centimeter. At home in the shack, you probably don't have sound proofed walls and ceiling, but the ambient noise often consists of only an air conditioner blower or Television sound from the next room. Under that condition, it wouldn't hurt to have a little more gain so you keep the microphone at a comfortable distance. However, many uses of the HTX-252 involve mobile operation where there are a lot of loud noises from the engine, traffic and an even louder air conditioner blower. In a heavy rainstorm you may not realize how loud it becomes. The result is a decreased audio signal-to-noise ratio. The only way to overcome that is by close talking, which increases the signal level with respect to the background noise level. This condition is the basis of most Ham Radio and commercial communications equipment designs. Obviously many people don't subscribe to that philosophy, so there are a number of amplified microphones on the market! 73, Fred, K4DII |
I'd like to be able to run the line
out audio from a scanner into the sound card and be able to display the audio envelope. The amplitude scale wouldn't need to be calibrated as long as I could count the number of divisions, I could compare the peak deviation from the 252 to other signals on the air. A quick and dirty deviation comparison checker. Mike- I have an old Heath deviation meter that uses a peak-reading meter to display deviation. It was necessary to calibrate it using the "Bessell null method" using a signal generator with sine-wave FM modulation. The signal is received on an SSB receiver with a fairly sharp filter. Modulation is adjusted for a carrier null, and the deviation is obtained from a table of bessell functions, based on the ratio of modulating frequency to peak deviation. This method is outlined in some ARRL publications that cover VHF-FM techniques. What you describe is very close to how other deviation meters work. They receive a signal, convert it to an intermediate frequency, FM detect and display the detector output on an oscilloscope. It is a lot easier to calibrate this kind of meter, since you only have to offset the transmitter's frequency by plus and minus one KHz increments, and adjust the oscilloscope to display the correct offset. Using a deviation meter, it is normal to use some loud sound such as whistling directly across the microphone, to adjust a radio's peak deviation control for about 5 KHz. Then you adjust the radio's microphone amplifier so average speech runs around 3 KHz. I have a Turner desk mic connected to the 252 at the moment. I don't really know if It's an improvement or not. I built a little adapter box with 6 push button switches so I can control the radio, The problem with the HTX-252, is there is no microphone amplifier adjustment, and some people think it should work when speaking some distance away from the microphone. Your Turner microphone may provide the extra amplification needed to talk at a greater distance. While I won't tell someone they shouldn't do that, I can at least partly justify keeping the adjustment set for talking very close to the microphone. By close, I mean about a quarter inch or one centimeter. At home in the shack, you probably don't have sound proofed walls and ceiling, but the ambient noise often consists of only an air conditioner blower or Television sound from the next room. Under that condition, it wouldn't hurt to have a little more gain so you keep the microphone at a comfortable distance. However, many uses of the HTX-252 involve mobile operation where there are a lot of loud noises from the engine, traffic and an even louder air conditioner blower. In a heavy rainstorm you may not realize how loud it becomes. The result is a decreased audio signal-to-noise ratio. The only way to overcome that is by close talking, which increases the signal level with respect to the background noise level. This condition is the basis of most Ham Radio and commercial communications equipment designs. Obviously many people don't subscribe to that philosophy, so there are a number of amplified microphones on the market! 73, Fred, K4DII |
I had a KDK two meter FM rig that drove all of us nuts with a similar
problem. It turned out that it was just off frequency from the factory. No one thought to check its frequency until lots of other things had been tried. Talk about red faces. Ed, NM2K "Fred McKenzie" wrote in message ... I'd like to be able to run the line out audio from a scanner into the sound card and be able to display the audio envelope. The amplitude scale wouldn't need to be calibrated as long as I could count the number of divisions, I could compare the peak deviation from the 252 to other signals on the air. A quick and dirty deviation comparison checker. Mike- I have an old Heath deviation meter that uses a peak-reading meter to display deviation. It was necessary to calibrate it using the "Bessell null method" using a signal generator with sine-wave FM modulation. The signal is received on an SSB receiver with a fairly sharp filter. Modulation is adjusted for a carrier null, and the deviation is obtained from a table of bessell functions, based on the ratio of modulating frequency to peak deviation. This method is outlined in some ARRL publications that cover VHF-FM techniques. What you describe is very close to how other deviation meters work. They receive a signal, convert it to an intermediate frequency, FM detect and display the detector output on an oscilloscope. It is a lot easier to calibrate this kind of meter, since you only have to offset the transmitter's frequency by plus and minus one KHz increments, and adjust the oscilloscope to display the correct offset. Using a deviation meter, it is normal to use some loud sound such as whistling directly across the microphone, to adjust a radio's peak deviation control for about 5 KHz. Then you adjust the radio's microphone amplifier so average speech runs around 3 KHz. I have a Turner desk mic connected to the 252 at the moment. I don't really know if It's an improvement or not. I built a little adapter box with 6 push button switches so I can control the radio, The problem with the HTX-252, is there is no microphone amplifier adjustment, and some people think it should work when speaking some distance away from the microphone. Your Turner microphone may provide the extra amplification needed to talk at a greater distance. While I won't tell someone they shouldn't do that, I can at least partly justify keeping the adjustment set for talking very close to the microphone. By close, I mean about a quarter inch or one centimeter. At home in the shack, you probably don't have sound proofed walls and ceiling, but the ambient noise often consists of only an air conditioner blower or Television sound from the next room. Under that condition, it wouldn't hurt to have a little more gain so you keep the microphone at a comfortable distance. However, many uses of the HTX-252 involve mobile operation where there are a lot of loud noises from the engine, traffic and an even louder air conditioner blower. In a heavy rainstorm you may not realize how loud it becomes. The result is a decreased audio signal-to-noise ratio. The only way to overcome that is by close talking, which increases the signal level with respect to the background noise level. This condition is the basis of most Ham Radio and commercial communications equipment designs. Obviously many people don't subscribe to that philosophy, so there are a number of amplified microphones on the market! 73, Fred, K4DII |
I had a KDK two meter FM rig that drove all of us nuts with a similar
problem. It turned out that it was just off frequency from the factory. No one thought to check its frequency until lots of other things had been tried. Talk about red faces. Ed, NM2K "Fred McKenzie" wrote in message ... I'd like to be able to run the line out audio from a scanner into the sound card and be able to display the audio envelope. The amplitude scale wouldn't need to be calibrated as long as I could count the number of divisions, I could compare the peak deviation from the 252 to other signals on the air. A quick and dirty deviation comparison checker. Mike- I have an old Heath deviation meter that uses a peak-reading meter to display deviation. It was necessary to calibrate it using the "Bessell null method" using a signal generator with sine-wave FM modulation. The signal is received on an SSB receiver with a fairly sharp filter. Modulation is adjusted for a carrier null, and the deviation is obtained from a table of bessell functions, based on the ratio of modulating frequency to peak deviation. This method is outlined in some ARRL publications that cover VHF-FM techniques. What you describe is very close to how other deviation meters work. They receive a signal, convert it to an intermediate frequency, FM detect and display the detector output on an oscilloscope. It is a lot easier to calibrate this kind of meter, since you only have to offset the transmitter's frequency by plus and minus one KHz increments, and adjust the oscilloscope to display the correct offset. Using a deviation meter, it is normal to use some loud sound such as whistling directly across the microphone, to adjust a radio's peak deviation control for about 5 KHz. Then you adjust the radio's microphone amplifier so average speech runs around 3 KHz. I have a Turner desk mic connected to the 252 at the moment. I don't really know if It's an improvement or not. I built a little adapter box with 6 push button switches so I can control the radio, The problem with the HTX-252, is there is no microphone amplifier adjustment, and some people think it should work when speaking some distance away from the microphone. Your Turner microphone may provide the extra amplification needed to talk at a greater distance. While I won't tell someone they shouldn't do that, I can at least partly justify keeping the adjustment set for talking very close to the microphone. By close, I mean about a quarter inch or one centimeter. At home in the shack, you probably don't have sound proofed walls and ceiling, but the ambient noise often consists of only an air conditioner blower or Television sound from the next room. Under that condition, it wouldn't hurt to have a little more gain so you keep the microphone at a comfortable distance. However, many uses of the HTX-252 involve mobile operation where there are a lot of loud noises from the engine, traffic and an even louder air conditioner blower. In a heavy rainstorm you may not realize how loud it becomes. The result is a decreased audio signal-to-noise ratio. The only way to overcome that is by close talking, which increases the signal level with respect to the background noise level. This condition is the basis of most Ham Radio and commercial communications equipment designs. Obviously many people don't subscribe to that philosophy, so there are a number of amplified microphones on the market! 73, Fred, K4DII |
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