Re: [Elecraft] Measuring power output of an SSB transmitter
Say you have a narrow-band signal at 1350 kHz, the frequency of our local AM broadcast station KSRO. You could use a sampling frequency of, say, 1000 kHz. The samples from the 1350 kHz signal would be identical to the samples of a signal at 350 kHz or 2350 kHz or 3350 kHz, etc. But if you know in advance that the signal is band-limited, then you can accurately re-create the 1350 kHz signal eliminating the "images" at the other frequencies. If you measure the 1350 kHz AM signal with a digital oscilloscope that has a 1 MHz sample rate, it will appear that the signal is at 350 kHz. (That is, the samples are identical to those from a 350 kHz signal.) But that's OK if you only care about the modulation. Al N1AL On Tue, 2008-04-29 at 16:43, Andrew Faber wrote: > Al, > I'm confused. I always thought (at least before I became a lawyer and > stopped thinking about such things) that to reconstruct a waveform you > needed to sample at twice the highest frequency of the Fourier components > contained in the signal waveform. For a sine wave, that would be twice the > frequency. For a square wave, that would be virtually impossible to do > accurately, since it is composed of an infinite series of sine wave > harmonics, though you could approximate an accurate waveform to any degree > desired by sampling ever higher in frequency. Are you saying something > different, or do you mean that for a narrow-band signal, you have a > practical high-frequency cut-off, and thus a practical limit on how fast you > need to sample? > 73, Andy, AE6Y > > - Original Message - > From: "Alan Bloom" <[EMAIL PROTECTED]> > To: "Romanchik Dan" <[EMAIL PROTECTED]> > Cc: "Mailing List Elecraft" > Sent: Tuesday, April 29, 2008 1:14 PM > Subject: Re: [Elecraft] Measuring power output of an SSB transmitter > > > > Actually, for a narrow-band signal, you only have to sample at twice the > > BANDWIDTH, not twice the frequency. So long as there are no interfering > > signals around (reasonably accurate when measuring a transmitter), > > so-called "undersampling" works fine so long as: > > > > 1. The sample rate is more than twice the bandwidth. > > 2. None of the harmonics (sample_rate/2) fall close to the signal. > > > > Al N1AL > > > > > > On Tue, 2008-04-29 at 11:05, Romanchik Dan wrote: > >> Sampling at twice the bandwidth will allow you to accurately extract > >> frequency information about a signal, or if all you were viewing were > >> sine waves. To view the actual waveform, however, you really want to > >> sample at at least 4x or 5x the bandwidth, or, even better, 10x the > >> bandwidth. > >> > >> 73! > >> > >> Dan KB6NU > >> -- > >> CW Geek and MI Affiliated Club Coordinator > >> Read my ham radio blog at http://www.kb6nu.com > >> LET'S GET MORE KIDS INTO HAM RADIO! > >> > >> > >> > >> On Apr 29, 2008, at Apr 29, 1:32 PM, Stephen Prior wrote: > >> > >> > On a related topic, does anyone have any experience of using the > >> > usb types > >> > of 'oscilloscopes' which appear on eBay- dual channel 60MHz > >> > bandwidth and > >> > 150Mb/s sampling rate? It's a neat and cost-effective way of > >> > displaying the > >> > transmitted waveform for those of us without desk/bench room for a > >> > 'proper' > >> > scope. > >> > > >> > I've always been led to believe that sampling at twice the > >> > bandwidth is a > >> > decent decent rule of thumb and this one is better than that. > >> > > >> > I'd be grateful for any advice from someone who has one. > >> > > >> > Thanks > >> > > >> > Stephen G4SJP > >> > > >> > KX-1, K2, K3 almost! > >> > > >> > > >> > > >> > ___ > >> > Elecraft mailing list > >> > Post to: Elecraft@mailman.qth.net > >> > You must be a subscriber to post to the list. > >> > Subscriber Info (Addr. Change, sub, unsub etc.): > >> > http://mailman.qth.net/mailman/listinfo/elecraft > >> > > >> > Help: http://mailman.qth.net/subscribers.htm > >> > Elecraft web page: http://www.elecraft.com > >> > > >> > >> ___ > >> Elecr
Re: [Elecraft] Measuring power output of an SSB transmitter
One might, at the risk of some oversimplification, think of the sampling process as demodulation. To recover the envelope, one does not care about the absolute frequency. What you are concerned with is the variation in amplitude. As I said, over-simplified but nonetheless perhaps useful as a starting point. Jack K8ZOA A recovering lawyer as well as engineer. Andrew Faber wrote: Al, I'm confused. I always thought (at least before I became a lawyer and stopped thinking about such things) that to reconstruct a waveform you needed to sample at twice the highest frequency of the Fourier components contained in the signal waveform. For a sine wave, that would be twice the frequency. For a square wave, that would be virtually impossible to do accurately, since it is composed of an infinite series of sine wave harmonics, though you could approximate an accurate waveform to any degree desired by sampling ever higher in frequency. Are you saying something different, or do you mean that for a narrow-band signal, you have a practical high-frequency cut-off, and thus a practical limit on how fast you need to sample? 73, Andy, AE6Y - Original Message - From: "Alan Bloom" <[EMAIL PROTECTED]> To: "Romanchik Dan" <[EMAIL PROTECTED]> Cc: "Mailing List Elecraft" Sent: Tuesday, April 29, 2008 1:14 PM Subject: Re: [Elecraft] Measuring power output of an SSB transmitter Actually, for a narrow-band signal, you only have to sample at twice the BANDWIDTH, not twice the frequency. So long as there are no interfering signals around (reasonably accurate when measuring a transmitter), so-called "undersampling" works fine so long as: 1. The sample rate is more than twice the bandwidth. 2. None of the harmonics (sample_rate/2) fall close to the signal. Al N1AL On Tue, 2008-04-29 at 11:05, Romanchik Dan wrote: Sampling at twice the bandwidth will allow you to accurately extract frequency information about a signal, or if all you were viewing were sine waves. To view the actual waveform, however, you really want to sample at at least 4x or 5x the bandwidth, or, even better, 10x the bandwidth. 73! Dan KB6NU -- CW Geek and MI Affiliated Club Coordinator Read my ham radio blog at http://www.kb6nu.com LET'S GET MORE KIDS INTO HAM RADIO! On Apr 29, 2008, at Apr 29, 1:32 PM, Stephen Prior wrote: > On a related topic, does anyone have any experience of using the > usb types > of 'oscilloscopes' which appear on eBay- dual channel 60MHz > bandwidth and > 150Mb/s sampling rate? It's a neat and cost-effective way of > displaying the > transmitted waveform for those of us without desk/bench room for a > 'proper' > scope. > > I've always been led to believe that sampling at twice the > bandwidth is a > decent decent rule of thumb and this one is better than that. > > I'd be grateful for any advice from someone who has one. > > Thanks > > Stephen G4SJP > > KX-1, K2, K3 almost! > > > > ___ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
Al, I'm confused. I always thought (at least before I became a lawyer and stopped thinking about such things) that to reconstruct a waveform you needed to sample at twice the highest frequency of the Fourier components contained in the signal waveform. For a sine wave, that would be twice the frequency. For a square wave, that would be virtually impossible to do accurately, since it is composed of an infinite series of sine wave harmonics, though you could approximate an accurate waveform to any degree desired by sampling ever higher in frequency. Are you saying something different, or do you mean that for a narrow-band signal, you have a practical high-frequency cut-off, and thus a practical limit on how fast you need to sample? 73, Andy, AE6Y - Original Message - From: "Alan Bloom" <[EMAIL PROTECTED]> To: "Romanchik Dan" <[EMAIL PROTECTED]> Cc: "Mailing List Elecraft" Sent: Tuesday, April 29, 2008 1:14 PM Subject: Re: [Elecraft] Measuring power output of an SSB transmitter Actually, for a narrow-band signal, you only have to sample at twice the BANDWIDTH, not twice the frequency. So long as there are no interfering signals around (reasonably accurate when measuring a transmitter), so-called "undersampling" works fine so long as: 1. The sample rate is more than twice the bandwidth. 2. None of the harmonics (sample_rate/2) fall close to the signal. Al N1AL On Tue, 2008-04-29 at 11:05, Romanchik Dan wrote: Sampling at twice the bandwidth will allow you to accurately extract frequency information about a signal, or if all you were viewing were sine waves. To view the actual waveform, however, you really want to sample at at least 4x or 5x the bandwidth, or, even better, 10x the bandwidth. 73! Dan KB6NU -- CW Geek and MI Affiliated Club Coordinator Read my ham radio blog at http://www.kb6nu.com LET'S GET MORE KIDS INTO HAM RADIO! On Apr 29, 2008, at Apr 29, 1:32 PM, Stephen Prior wrote: > On a related topic, does anyone have any experience of using the > usb types > of 'oscilloscopes' which appear on eBay- dual channel 60MHz > bandwidth and > 150Mb/s sampling rate? It's a neat and cost-effective way of > displaying the > transmitted waveform for those of us without desk/bench room for a > 'proper' > scope. > > I've always been led to believe that sampling at twice the > bandwidth is a > decent decent rule of thumb and this one is better than that. > > I'd be grateful for any advice from someone who has one. > > Thanks > > Stephen G4SJP > > KX-1, K2, K3 almost! > > > > ___ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
Actually, for a narrow-band signal, you only have to sample at twice the BANDWIDTH, not twice the frequency. So long as there are no interfering signals around (reasonably accurate when measuring a transmitter), so-called "undersampling" works fine so long as: 1. The sample rate is more than twice the bandwidth. 2. None of the harmonics (sample_rate/2) fall close to the signal. Al N1AL On Tue, 2008-04-29 at 11:05, Romanchik Dan wrote: > Sampling at twice the bandwidth will allow you to accurately extract > frequency information about a signal, or if all you were viewing were > sine waves. To view the actual waveform, however, you really want to > sample at at least 4x or 5x the bandwidth, or, even better, 10x the > bandwidth. > > 73! > > Dan KB6NU > -- > CW Geek and MI Affiliated Club Coordinator > Read my ham radio blog at http://www.kb6nu.com > LET'S GET MORE KIDS INTO HAM RADIO! > > > > On Apr 29, 2008, at Apr 29, 1:32 PM, Stephen Prior wrote: > > > On a related topic, does anyone have any experience of using the > > usb types > > of 'oscilloscopes' which appear on eBay- dual channel 60MHz > > bandwidth and > > 150Mb/s sampling rate? It's a neat and cost-effective way of > > displaying the > > transmitted waveform for those of us without desk/bench room for a > > 'proper' > > scope. > > > > I've always been led to believe that sampling at twice the > > bandwidth is a > > decent decent rule of thumb and this one is better than that. > > > > I'd be grateful for any advice from someone who has one. > > > > Thanks > > > > Stephen G4SJP > > > > KX-1, K2, K3 almost! > > > > > > > > ___ > > Elecraft mailing list > > Post to: Elecraft@mailman.qth.net > > You must be a subscriber to post to the list. > > Subscriber Info (Addr. Change, sub, unsub etc.): > > http://mailman.qth.net/mailman/listinfo/elecraft > > > > Help: http://mailman.qth.net/subscribers.htm > > Elecraft web page: http://www.elecraft.com > > > > ___ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
Sampling at twice the bandwidth will allow you to accurately extract frequency information about a signal, or if all you were viewing were sine waves. To view the actual waveform, however, you really want to sample at at least 4x or 5x the bandwidth, or, even better, 10x the bandwidth. 73! Dan KB6NU -- CW Geek and MI Affiliated Club Coordinator Read my ham radio blog at http://www.kb6nu.com LET'S GET MORE KIDS INTO HAM RADIO! On Apr 29, 2008, at Apr 29, 1:32 PM, Stephen Prior wrote: On a related topic, does anyone have any experience of using the usb types of 'oscilloscopes' which appear on eBay- dual channel 60MHz bandwidth and 150Mb/s sampling rate? It's a neat and cost-effective way of displaying the transmitted waveform for those of us without desk/bench room for a 'proper' scope. I've always been led to believe that sampling at twice the bandwidth is a decent decent rule of thumb and this one is better than that. I'd be grateful for any advice from someone who has one. Thanks Stephen G4SJP KX-1, K2, K3 almost! ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
On a related topic, does anyone have any experience of using the usb types of 'oscilloscopes' which appear on eBay- dual channel 60MHz bandwidth and 150Mb/s sampling rate? It's a neat and cost-effective way of displaying the transmitted waveform for those of us without desk/bench room for a 'proper' scope. I've always been led to believe that sampling at twice the bandwidth is a decent decent rule of thumb and this one is better than that. I'd be grateful for any advice from someone who has one. Thanks Stephen G4SJP KX-1, K2, K3 almost! ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
Hi all, Just for the record, I determined empirically that I needed a compressor setting of 20 to get a reasonable amount of talk power. I have been using this setting since my first week of operation and I am still getting good audio reports. My "indication" of "talk power" is from watching the average reading analog meter in my tuner. With this said I have visibly more talk power with the K3 than I had with my IC-718 with its fixed compressor turned on. Some IC-718 owners describe the compressor as preset from the factory as overly aggressive and recommend touching up an internal adjustment. I never found mine excessive and I always got good audio reports with the 718. One of these days I will take a scope home and check if the peak power indeed varies with the compressor setting, which of course it should not. AB2TC - Knut Stewart G3RXQ wrote: > > I have now repeated the test with my 2 tone external source, and > get similar results to the microphone "Wurlo" test. The PEAK > signal amplitude is influenced by the Compression (Clipping ?) > > Approaching the anniversary of the product release, it's 'bout > time the SSB transmit side of the K3 was sorted out. > Brings back memories of the KSB2 saga ! > > 73 > Stewart G3RXQ > On Tue, 29 Apr 2008 03:46:46 -0700 (PDT), G4ILO wrote: >> >> >> Stewart G3RXQ wrote: >> >>> My PEAK power is down by about 50% as measured on an 200MHz >>> oscilloscope when the COMP is set to 0. This can't be right.. >>> >> I don't have your measuring equipment, Stewart, but something > doesn't seem >> right to me either. >> >> The power output doesn't seem consistent even when you don't > change the >> settings. With MIC=60 CMP=0 and PWR=12.0 if I "aaalo" into the > mic, my >> average reading power meter normally shows about 1W. But > sometimes it holds >> at 2W or even 3W and sometimes a bit less. I have also observed > the meter >> steady at say 2W then after about a second drop back to 1W, even > though I >> haven't changed the pitch or tone of my "...". I realize > this is not a >> scientific test, but I don't believe that there is that much > difference >> between my consecutive repetitions of "aaalo." >> >> I need CMP=20 to get a reasonable average level on speech. > Without any >> compression the talk power is too low. Even my FT-817 with 5W > pep output can >> manage an average of 1W on speech and it doesn't have a speech > compressor. > > -- View this message in context: http://www.nabble.com/K3%3A-two-problems-tp16943980p16960444.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
I have now repeated the test with my 2 tone external source, and get similar results to the microphone "Wurlo" test. The PEAK signal amplitude is influenced by the Compression (Clipping ?) Approaching the anniversary of the product release, it's 'bout time the SSB transmit side of the K3 was sorted out. Brings back memories of the KSB2 saga ! 73 Stewart G3RXQ On Tue, 29 Apr 2008 03:46:46 -0700 (PDT), G4ILO wrote: > > > Stewart G3RXQ wrote: > >> My PEAK power is down by about 50% as measured on an 200MHz >> oscilloscope when the COMP is set to 0. This can't be right.. >> > I don't have your measuring equipment, Stewart, but something doesn't seem > right to me either. > > The power output doesn't seem consistent even when you don't change the > settings. With MIC=60 CMP=0 and PWR=12.0 if I "aaalo" into the mic, my > average reading power meter normally shows about 1W. But sometimes it holds > at 2W or even 3W and sometimes a bit less. I have also observed the meter > steady at say 2W then after about a second drop back to 1W, even though I > haven't changed the pitch or tone of my "...". I realize this is not a > scientific test, but I don't believe that there is that much difference > between my consecutive repetitions of "aaalo." > > I need CMP=20 to get a reasonable average level on speech. Without any > compression the talk power is too low. Even my FT-817 with 5W pep output can > manage an average of 1W on speech and it doesn't have a speech compressor. > > After doing these tests I connected the antenna again and the power meter on > the MFJ tuner was showing a low reading. I put the PM20 back and sure > enough, the power was low. No control on the radio was changed. I twiddled > the power control down and then back up to 12.0 and full power was restored. > Go figure. > > - > Julian, G4ILO K3 s/n: 222 K2 s/n: 392 > G4ILO's Shack: www.g4ilo.com > Zerobeat Ham Forums: www.zerobeat.net/smf ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
Stewart G3RXQ wrote: > > My PEAK power is down by about 50% as measured on an 200MHz > oscilloscope when the COMP is set to 0. This can't be right.. > I don't have your measuring equipment, Stewart, but something doesn't seem right to me either. The power output doesn't seem consistent even when you don't change the settings. With MIC=60 CMP=0 and PWR=12.0 if I "aaalo" into the mic, my average reading power meter normally shows about 1W. But sometimes it holds at 2W or even 3W and sometimes a bit less. I have also observed the meter steady at say 2W then after about a second drop back to 1W, even though I haven't changed the pitch or tone of my "...". I realize this is not a scientific test, but I don't believe that there is that much difference between my consecutive repetitions of "aaalo." I need CMP=20 to get a reasonable average level on speech. Without any compression the talk power is too low. Even my FT-817 with 5W pep output can manage an average of 1W on speech and it doesn't have a speech compressor. After doing these tests I connected the antenna again and the power meter on the MFJ tuner was showing a low reading. I put the PM20 back and sure enough, the power was low. No control on the radio was changed. I twiddled the power control down and then back up to 12.0 and full power was restored. Go figure. - Julian, G4ILO K3 s/n: 222 K2 s/n: 392 G4ILO's Shack: www.g4ilo.com Zerobeat Ham Forums: www.zerobeat.net/smf -- View this message in context: http://www.nabble.com/K3%3A-two-problems-tp16943980p16957616.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
My PEAK power is down by about 50% as measured on an 200MHz oscilloscope when the COMP is set to 0. This can't be right.. 73 Stewart G3RXQ On Mon, 28 Apr 2008 22:25:36 -0700 (PDT), Paul G4LNA wrote: > > I quite agree with you Brian, I didn't think there was any other way of > monitoring SSB reliably. I've always used a scope way back when I used to > build AM transmitters and I have one permanently connected so I can keep an > eye on what's going on, meters tell lies I find. > > 73 Paul G4LNA. > > > Brian Lloyd-6 wrote: > >> There is no substitute for an oscilloscope. There are precious few >> meters that will read true peak power. Also, no meter is going to show >> you peak compression or outright flat-topping (clipping) like a 'scope. >> >> Someone mentioned that their power output went down when they turned >> the compression down and would Elecraft make power output remain >> constant as compression is reduced. Well, the power output (average) >> is *SUPPOSED* to decrease when you reduce compression. When speech >> compression is reduced, your peak-to-average power ratio increases. >> The peaks remain just as high but the average power is considerably >> less. This is another reason to want a 'scope to check your rig. >> >> BTW, how many people have done a two-tone test or a double trapezoid >> test for linearity? How many people even know what I am talking >> about? :-) >> >> (My first HF transmitter was a Central Electronics Multi-Phase exciter >> with a whopping 10W of output. When I got done making that work again >> you can bet I understood single-sideband. :-) >> >> Brian Lloyd >> Granite Bay Montessori School 9330 Sierra College Bl >> brian AT gbmontessori DOT com Roseville, CA 95661 >> +1.916.367.2131 (voice)+1.791.912.8170 (fax) >> >> PGP key ID: 12095C52A32A1B6C >> PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C >> >> >> ___ >> Elecraft mailing list >> Post to: Elecraft@mailman.qth.net >> You must be a subscriber to post to the list. >> Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >> Help: http://mailman.qth.net/subscribers.htm >> Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Measuring power output of an SSB transmitter
I quite agree with you Brian, I didn't think there was any other way of monitoring SSB reliably. I've always used a scope way back when I used to build AM transmitters and I have one permanently connected so I can keep an eye on what's going on, meters tell lies I find. 73 Paul G4LNA. Brian Lloyd-6 wrote: > > There is no substitute for an oscilloscope. There are precious few > meters that will read true peak power. Also, no meter is going to show > you peak compression or outright flat-topping (clipping) like a 'scope. > > Someone mentioned that their power output went down when they turned > the compression down and would Elecraft make power output remain > constant as compression is reduced. Well, the power output (average) > is *SUPPOSED* to decrease when you reduce compression. When speech > compression is reduced, your peak-to-average power ratio increases. > The peaks remain just as high but the average power is considerably > less. This is another reason to want a 'scope to check your rig. > > BTW, how many people have done a two-tone test or a double trapezoid > test for linearity? How many people even know what I am talking > about? :-) > > (My first HF transmitter was a Central Electronics Multi-Phase exciter > with a whopping 10W of output. When I got done making that work again > you can bet I understood single-sideband. :-) > > Brian Lloyd > Granite Bay Montessori School 9330 Sierra College Bl > brian AT gbmontessori DOT com Roseville, CA 95661 > +1.916.367.2131 (voice)+1.791.912.8170 (fax) > > PGP key ID: 12095C52A32A1B6C > PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C > > > > > ___ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > -- View this message in context: http://www.nabble.com/K3%3A-two-problems-tp16943980p16953021.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Measuring power output of an SSB transmitter
There is no substitute for an oscilloscope. There are precious few meters that will read true peak power. Also, no meter is going to show you peak compression or outright flat-topping (clipping) like a 'scope. Someone mentioned that their power output went down when they turned the compression down and would Elecraft make power output remain constant as compression is reduced. Well, the power output (average) is *SUPPOSED* to decrease when you reduce compression. When speech compression is reduced, your peak-to-average power ratio increases. The peaks remain just as high but the average power is considerably less. This is another reason to want a 'scope to check your rig. BTW, how many people have done a two-tone test or a double trapezoid test for linearity? How many people even know what I am talking about? :-) (My first HF transmitter was a Central Electronics Multi-Phase exciter with a whopping 10W of output. When I got done making that work again you can bet I understood single-sideband. :-) Brian Lloyd Granite Bay Montessori School 9330 Sierra College Bl brian AT gbmontessori DOT com Roseville, CA 95661 +1.916.367.2131 (voice)+1.791.912.8170 (fax) PGP key ID: 12095C52A32A1B6C PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
