Anyone know if this would be a good piece of equipment or not. Been looking around for these since robb mentioned the usb scope to me. It is a usb 2ch. 60mhz digital oscilloscope spectrum analyzer dds signal generator sweep. I am not for sure if this would work for me or not just trying to find something not to awfull expensive. The name is instrustar by onetak. On e-bay and amazon for $158.00. Thanks for the help. daddyo.
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usb oscilloscope by onetak
- Thread starter daddyo
- Start date
That is not what I was talking about. That is a cheap usb o'scope that doesn't have enough range as a spectrum analyzer. It would need to have a range of at least 200mhz as a spectrum analyzer; it has only 60mhz to offer.
As a signal generator, it can only go as high as 20mhz; you need one that can go to 28mhz. So, it can't do that either.
It will work as a scope - though. But you could get a 50mhz analog scope for $25-75 that would do the same job for far less money.
As a signal generator, it can only go as high as 20mhz; you need one that can go to 28mhz. So, it can't do that either.
It will work as a scope - though. But you could get a 50mhz analog scope for $25-75 that would do the same job for far less money.
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Comtek is a program that uses the line input of your sound card to see the SINAD.
From Wikipedia:
A typical example, quoted from a commercial hand held VHF or UHF radio, might be:
Receiver sensitivity: 0.25μV at 12dB SINAD
which is stating that the receiver will produce intelligible speech with a signal at its input as low as 0.25μV. Radio receiver designers will test the product in a laboratory following a procedure. A typical example procedure is as follows:
Translated, this means that a SINAD meter is basically making sure that when a receiver is being peaked that it is not peaked too much and go into distortion and noise. These elements can make a receiver nasty sounding and hard to understand - in simplest terms. Doing a receiver is not exactly a 'piece of cake' for the beginner.
So, you see that SINAD is important to get the best signal to distortion ratio when doing a receiver alignment. You will also need a signal generator as well. But we are getting ahead of ourselves here.
Think the equipment you need at this point would be a dummy load, watt meter, DVM, O-scope, and perhaps a freq counter. Forget about doing receiver alignments until you can establish transmit alignments first. Receiver alignments are a bit trickier and a bit more costly - equipment wise - as well as a bit tougher to grasp and perform if done well.
This link is for the Spectrum analyzer I talked about. Never used one of these units and I don't know if it will do the job as yet:
http://rover.ebay.com/rover/1/711-5...0001&campid=5336136228&icep_item=111805709667
If it does work as I hope, this could a very simple and inexpensive means to monitor a CB for spurious emissions/'harmonics'. Until now, lab grade analyzers are very expensive, but aren't really necessary to get the job needed for the CB.
From Wikipedia:
A typical example, quoted from a commercial hand held VHF or UHF radio, might be:
Receiver sensitivity: 0.25μV at 12dB SINAD
which is stating that the receiver will produce intelligible speech with a signal at its input as low as 0.25μV. Radio receiver designers will test the product in a laboratory following a procedure. A typical example procedure is as follows:
- With no signal present on the input, the noise and distortion of the receiver are measured at a convenient level
- A signal is applied to the input which causes the output to increase 12 dB
- The level of the signal needed to produce this is noted and is found to be 0.25 microVolts.
Translated, this means that a SINAD meter is basically making sure that when a receiver is being peaked that it is not peaked too much and go into distortion and noise. These elements can make a receiver nasty sounding and hard to understand - in simplest terms. Doing a receiver is not exactly a 'piece of cake' for the beginner.
So, you see that SINAD is important to get the best signal to distortion ratio when doing a receiver alignment. You will also need a signal generator as well. But we are getting ahead of ourselves here.
Think the equipment you need at this point would be a dummy load, watt meter, DVM, O-scope, and perhaps a freq counter. Forget about doing receiver alignments until you can establish transmit alignments first. Receiver alignments are a bit trickier and a bit more costly - equipment wise - as well as a bit tougher to grasp and perform if done well.
This link is for the Spectrum analyzer I talked about. Never used one of these units and I don't know if it will do the job as yet:
http://rover.ebay.com/rover/1/711-5...0001&campid=5336136228&icep_item=111805709667
If it does work as I hope, this could a very simple and inexpensive means to monitor a CB for spurious emissions/'harmonics'. Until now, lab grade analyzers are very expensive, but aren't really necessary to get the job needed for the CB.
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That was great robb you laid that out in simple terms this is giving me a guide to go by and what it would be used for. Just what I wanted. Big thanks. Now I have a problem I just done a mod to a cobra29 nw as follows: first mod called for irf-520 did not have used a irf-510 removed r55,r56,c61. Add a 68pf cap across c59 made a en369fn companion part 230k resistor,360ohm resistor and 1/ 1n4148 diode. Put that in r56 spot. With positive lead towards r123. Removed tuning slug from L-14. Called for a 22 pico in r-55 spot maybe give more swing. I also put a 100k pot from c116 positive side to irf-510 gate. Replaced c62 with a 390pf 50v cap. now the solder side had a cap on c62 left it off first then put it back on. The problem is it had a really bad whine on the other end when I talked to someone and that was with the l-14 slug in took slug out and the said whine went away but was not as clear as it should be. adjusting pot gave a higher or lower dk. With dk high audio chip gets real hot so does irf-510. And you can feel audio chip vibrate when I talk.Also mod said you can adjust gate voltage with pot but I don't know if I was doing it right with dvm to measure voltage do you put one lead of dvm to gate and other to ground. thanks for any help. daddyo
Haven't done any AM-only radios in a while.
Sounds like it is working. Check the gate voltage and see if it is between 3.5-4v. Generally when you put in a MOSFET final, tuning/peaking the transmit chain is necessary for optimal results. What are seeing with your watt meter? Do you have a 50 ohm dummy load yet? You will need one for tuning.
If the audio amp is getting hot, I would suspect that you have the mic gain too high and have the limiter removed. Set it stock and then test with a dummy load for best results. Listen to the radio with another radio if you have one until you can get a O-scope to see how it is tuned. If you hear distortion,you are over peaking.
Which mod sheet did you use for the install; CBTricks?
Should work fine.
Sounds like it is working. Check the gate voltage and see if it is between 3.5-4v. Generally when you put in a MOSFET final, tuning/peaking the transmit chain is necessary for optimal results. What are seeing with your watt meter? Do you have a 50 ohm dummy load yet? You will need one for tuning.
If the audio amp is getting hot, I would suspect that you have the mic gain too high and have the limiter removed. Set it stock and then test with a dummy load for best results. Listen to the radio with another radio if you have one until you can get a O-scope to see how it is tuned. If you hear distortion,you are over peaking.
Which mod sheet did you use for the install; CBTricks?
Should work fine.
Mod sheet I think was off of mouldroppers.com Limiter is in place. 50ohm dummy load is on the way. I am trying to adjust gate voltage w/ 100k pot but can not get it to go that low it will got to 7-8 then to 0 then way above . Am I correct on how to measure voltage: one lead on gate other on a ground somewhere and you have to key mike correct. Iam looking for a o-scope as we speak 50mhz analog as you said but all I come up w/ is $100 junk or $200-300 on e-bay and amazon. I guess I should have posted as new thread so everyone could read this. Iwould copy and paste this in new forum if I knew how or can you do that. Might have to get the wife in on that. Thanks for all the help things are coming together as to what I need and where to start. BIG THANKS.daddyo
Look locally for a scope, or the nearest large city to you. Ebay will have them at various prices; some fair and some not so. Plus shipping makes it more. Some of them are 'Make Offer' too. Remember, that some are trying to unload them because they often now have the new digital scopes, making the analog scopes obsolete. But not unusable for your needs.
If you are reading the gate correctly, that MOSFET will have died an explosive death if they get 7-8 volts. So, if the radio is working, then you are doing something wrong in testing. Always check and double check your work. Otherwise, you will start turning radios into useless junk or parts radios. You are trying to turn that tide in the other direction, so do things carefully.
If you are reading the gate correctly, that MOSFET will have died an explosive death if they get 7-8 volts. So, if the radio is working, then you are doing something wrong in testing. Always check and double check your work. Otherwise, you will start turning radios into useless junk or parts radios. You are trying to turn that tide in the other direction, so do things carefully.
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