[AMRadio] new AM rig
Hey AM'ers, I just got some E-mail from Dave Benson. Ok, for those who don't know Dave he sells Qrp kits such as the Rock mite CW rig. Dave has a AM rig almost ready in kit form, solid state with abt 8 watts out I hope to get me hands on one as soon as they are out to try. de Skip K3CC -- Internal Virus Database is out-of-date. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 266.7.0 - Release Date: 3/8/2005
[AMRadio] AM QRP
Sri my mind was else where Here's Dave Benson's website small wonder labs QRP stuff E-mail Dave and tell him you heard abt the AM QRP xcvr from me. http://www.smallwonderlabs.com That will get you there. The kit is not on the site,if we tickle him , maybe it will get there sooner. de SkipK3CC -- Internal Virus Database is out-of-date. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 266.7.0 - Release Date: 3/8/2005
[AMRadio] SSB AM revisited
SSB AM has been discussed before and was always thought the transmitter to have audio power down 3 db from regular double side band AM transmitter. This is because of only transmitting one side band and thus half the power in the side bands. A DSB AM transmitter has each side band 6 db down from the carrier. In thinking about it I was trying to come up with how we get the same PEP power with SSB AM as we do with DSB AM. It turns out that you can run 4 times the side band power in a single side band as you can when using double side band AM. With SSB AM 100% modulation the side band power equals the carrier power! It is not 6 db down as each side band is with DSB AM. If you look at PEP with AM, the voltage into the antenna doubles with modulation to make PEP 4 times what the carrier power is. With SSB AM the voltage also doubles to make PEP 4 times carrier power. But in this case it takes the same amount of power in the side band as there is in the carrier! Just to verify all this I hooked up the spectrum analyzer, scope and PEP watt meter to the old 20A. Here is how the numbers work out: On AM DSB. carrier power= 2 watts. carrier volts= 10 volts. side band power each = .5 watts. side band volts each = 5 volts. PEP of transmitter =8 watts. On SSB AM. carrier power = 2 watts. carrier volts = 10 volts. side band power = 2 watts. side band volts = 10 volts. PEP of transmitter =8 watts. When figuring PEP of an AM transmitter you must add the voltage of each component together and then square it and divide by the resistance it feeds. You can not add power directly. In the case of DSB AM the voltage of the carrier gets added plus the voltage of the upper side band plus the voltage of the lower side band. In the example above that equals 20 volts. 20x20=400. divide by 50 = 8 watts PEP. With SSB AM there is only the carrier and one side bands voltage to add together to find PEP. In the above example 10 volts carrier plus 10 volts side band = 20 volts. Squared= 400 divide by 50 = 8 watts PEP. But as you can see there is twice the voltage in the side band or 4 times more power in it than with double side band am. This still gives the same PEP. With 6 db more audio power in SSB AM than in one side band of DSB AM the recovered audio should be the same as with DSB AM. DSB AM was always thought to have a 6 db advantage because of having the second side band and being coherent in the detector. Seems this evens things out. Of course there are the distortion issues in the detector with SSB AM to deal with. With a little thinking you can see where you might be able to run more carrier power with SSB AM and not having to reduce the audio level as much as you would with DSB AM and have the PEP still stay within limits. Here are some numbers with the carrier increased to 3.34 watts (1.67 times) and audio down only by 3 db. carrier power= 3.34 watts. carrier volts= 12.93 volts. side band power = 1 watt. side band volts = 7.07 volts. PEP of transmitter =8 watts. 73 Gary K4FMX
Re: [AMRadio] new AM rig
That's great. Keep us posted. Mike Duke, K5XU
Re: [AMRadio] new AM rig
I hope you will let us all know about it and were to get it... Sounds like fun... Bob W1PE At 06:50 AM 3/17/05, you wrote: Hey AM'ers, I just got some E-mail from Dave Benson. Ok, for those who don't know Dave he sells Qrp kits such as the Rock mite CW rig. Dave has a AM rig almost ready in kit form, solid state with abt 8 watts out I hope to get me hands on one as soon as they are out to try. de Skip K3CC -- Internal Virus Database is out-of-date. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 266.7.0 - Release Date: 3/8/2005 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.3 - Release Date: 3/15/05 Very Best 73's Bob Peters-W1PE ARRL ASM, President QCWA Chapter 41 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.3 - Release Date: 3/15/05
RE: [AMRadio] SSB AM revisited
See the link at http://www.qsl.net/wa5bxo/amtech.html There is a picture at the bottom of the graphical analysis that Don is talking about. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester Sent: Thursday, March 17, 2005 6:04 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] SSB AM revisited In thinking about it I was trying to come up with how we get the same PEP power with SSB AM as we do with DSB AM. It turns out that you can run 4 times the side band power in a single side band as you can when using double side band AM. With SSB AM 100% modulation the side band power equals the carrier power! It is not 6 db down as each side band is with DSB AM. But when you achieve near 100% modulation with SSB AM the quadrature distortion makes it almost unreadable. You have to turn on the BFO on to demodulate it, just like with SSB suppressed carrier. In fact, SSB AM is nothing more than SSB with poor carrier suppression. With DSB AM, the quadrature distortion of one sideband nulls out the quadrature distortion of the othe, so that the envelope detector can demodulate it with (theoretically) negligible distortion. The only way SSB AM can be destortion free is to run a vely low percentage of modulation, or insert additional carrier (the BFO). That's why, with an old buzzard receiver without product detector, you have to turn the rf gain way down to demodulate SSB. Think of the BFO as the carrier, and the SSB signal as the sideband. With the rf gain turned all the way up, the percentage of modulation is high, and the signal is highly distorted. When you turn the rf gain down, you are effectively lowering the pecentage of modulation to the point that the quadrature distortion becomes negligible. The entire process can easily be graphically demonstrated with vector diagrams. The most effective use for SSB AM is for its carrier to serve as a pilot for a PLL-controlled local oscillator to lock onto, maintaining zero tuning error. Don K4KYV __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] SSB AM revisited
Gary: SSB AM, like any linear system must have the sideband amplitude carefully adjusted in relation to the carrier in order for the diode detector to reproduce the AM without excessive distortion. It can be made to sound fairly well, in my opinion. Other than the carrier being used to lock a PLL as Don-KYV has suggested, the carrier serves another good purpose. That is to quiet down any noise between sylables. Good quality SSB dosnt sound bad except for the junk in between sylables. The overall reduction in bandwidth on transmit makes us better neighbors and the reduction in receive bandwidth favors us without as much QRM. I dont expect many hams to use SSB AM, much like we didnt use NBFM or NBPM early on. If the radio didnt come equipped with mode, we would have to experiment. 73 , Charlie, K0NG Quoting Gary Schafer [EMAIL PROTECTED]: SSB AM has been discussed before and was always thought the transmitter to have audio power down 3 db from regular double side band AM transmitter. This is because of only transmitting one side band and thus half the power in the side bands. A DSB AM transmitter has each side band 6 db down from the carrier. In thinking about it I was trying to come up with how we get the same PEP power with SSB AM as we do with DSB AM. It turns out that you can run 4 times the side band power in a single side band as you can when using double side band AM. With SSB AM 100% modulation the side band power equals the carrier power! It is not 6 db down as each side band is with DSB AM. If you look at PEP with AM, the voltage into the antenna doubles with modulation to make PEP 4 times what the carrier power is. With SSB AM the voltage also doubles to make PEP 4 times carrier power. But in this case it takes the same amount of power in the side band as there is in the carrier! Just to verify all this I hooked up the spectrum analyzer, scope and PEP watt meter to the old 20A. Here is how the numbers work out: On AM DSB. carrier power= 2 watts. carrier volts= 10 volts. side band power each = .5 watts. side band volts each = 5 volts. PEP of transmitter =8 watts. On SSB AM. carrier power = 2 watts. carrier volts = 10 volts. side band power = 2 watts. side band volts = 10 volts. PEP of transmitter =8 watts. When figuring PEP of an AM transmitter you must add the voltage of each component together and then square it and divide by the resistance it feeds. You can not add power directly. In the case of DSB AM the voltage of the carrier gets added plus the voltage of the upper side band plus the voltage of the lower side band. In the example above that equals 20 volts. 20x20=400. divide by 50 = 8 watts PEP. With SSB AM there is only the carrier and one side bands voltage to add together to find PEP. In the above example 10 volts carrier plus 10 volts side band = 20 volts. Squared= 400 divide by 50 = 8 watts PEP. But as you can see there is twice the voltage in the side band or 4 times more power in it than with double side band am. This still gives the same PEP. With 6 db more audio power in SSB AM than in one side band of DSB AM the recovered audio should be the same as with DSB AM. DSB AM was always thought to have a 6 db advantage because of having the second side band and being coherent in the detector. Seems this evens things out. Of course there are the distortion issues in the detector with SSB AM to deal with. With a little thinking you can see where you might be able to run more carrier power with SSB AM and not having to reduce the audio level as much as you would with DSB AM and have the PEP still stay within limits. Here are some numbers with the carrier increased to 3.34 watts (1.67 times) and audio down only by 3 db. carrier power= 3.34 watts. carrier volts= 12.93 volts. side band power = 1 watt. side band volts = 7.07 volts. PEP of transmitter =8 watts. 73 Gary K4FMX __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] SSB AM revisited
[EMAIL PROTECTED] wrote: Gary: SSB AM, like any linear system must have the sideband amplitude carefully adjusted in relation to the carrier in order for the diode detector to reproduce the AM without excessive distortion. It can be made to sound fairly well, in my opinion. Other than the carrier being used to lock a PLL as Don-KYV has suggested, the carrier serves another good purpose. That is to quiet down any noise between sylables. Good quality SSB dosnt sound bad except for the junk in between sylables. The overall reduction in bandwidth on transmit makes us better neighbors and the reduction in receive bandwidth favors us without as much QRM. I dont expect many hams to use SSB AM, much like we didnt use NBFM or NBPM early on. If the radio didnt come equipped with mode, we would have to experiment. I missed some of the earlier posts. I did see the analysis that Gary did. Interesting. So why would you want to use SSB AM? Regards, Frank Kamp K5DKZ
Re: [AMRadio] SSB AM revisited
In a message dated 3/17/05 4:04:03 PM, [EMAIL PROTECTED] writes (in part): The only way SSB AM can be destortion free is to run a vely low percentage of modulation, or insert additional carrier (the BFO). Ah, so... wondered about that. Ran a Harris 301/302 a while ago which in the AM mode adds a carrier to it's normal USB output. Observed that to sound good it had to be adjusted so that on the scope it looked like DSB AM modulated about 50%. Dennis D. W7QHO Glendale, CA
