K3: two problems
Locked
12
12
 
|
today I observed a problem with my K3 ATU.
on some bands the ATU does not find a fix. I connected the transceiver to a 50 ohm 100 Watt dummy load. I tried on 1850 - no fix - rattle rattle - display says: - . - with Xmit: 1.0 - 1 3700 - quick fix 1.0 - 1 5330 - no fix but when I press transmit it shows 1.2 - 1 1.0 ATU in bypass 7080 - no fix with xmit 1.0 - 1 10142 - no fix with xmit 1.4 - 1 (tuner inline - 1.0 - 1 tuner bypass) 14142 - quick fix 1.0 - 1 18068 - quick fix 1.0 - 1 21000 - quick fix 1.0 - 1 24890 - quick fix 1.0 - 1 28000 - quick fix 1.0 - 1 50750 - quick fix 1.0 - 1 second problem: I have the impression that the switch from Mic high and low level does not work anymore. I observed a low power output (about 40W max) with Mic high sensitivity, and no change when I switch to low. Front and Back panel is the same. I hope I can get a hint where to look. 73! de Werner OE9FWV -- Failing to plan is planning to fail. Email powered by Pegasus Mail free at <http://www.pmail.com> Homepage: <http://www.qsl.net/oe9fwv/> Fone +43 5522 75013 Fax +43 820 555 85 2621 Mobile +43 664 6340014 Elecraft K2 #5203 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
Hi Werner:
With respect to your second problem, the mic high / low setting is working on #202 with latest firmware. It is easy to demonstrate if you set the MAIN:MIC SEL to high (rP.H in my case), set compression to zero(0), and MIC gain to zero(0), and the METER to display the ALC. Tap the XMIT button to key transmitter, speak into mic and increase the MIC gain to produce an ALC indication of 4-5. Then reset the the MAIN:MIC SEL to low (rP.L in my case). Now, without changing the MIC gain or the compression, tap the XMIT button and speak into mic. I see no ALC action at this time. This clearly indicates that the high / low setting is working. 73, Ken Wagner K3IU K3 #202 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dr. Werner Furlan wrote: > today I observed a problem with my K3 ATU. > > on some bands the ATU does not find a fix. > I connected the transceiver to a 50 ohm 100 Watt dummy load. > > I tried on > > 1850 - no fix - rattle rattle - display says: - . - with Xmit: 1.0 - 1 > 3700 - quick fix 1.0 - 1 > 5330 - no fix but when I press transmit it shows 1.2 - 1 1.0 ATU in bypass > 7080 - no fix with xmit 1.0 - 1 > 10142 - no fix with xmit 1.4 - 1 (tuner inline - 1.0 - 1 tuner bypass) > 14142 - quick fix 1.0 - 1 > 18068 - quick fix 1.0 - 1 > 21000 - quick fix 1.0 - 1 > 24890 - quick fix 1.0 - 1 > 28000 - quick fix 1.0 - 1 > 50750 - quick fix 1.0 - 1 > > > > second problem: > I have the impression that the switch from Mic high and low level does not > work anymore. I observed a low power output (about 40W max) with Mic > high sensitivity, and no change when I switch to low. Front and Back panel is > the same. > > I hope I can get a hint where to look. > > > 73! de Werner OE9FWV > > Elecraft mailing list Post to: [hidden email] 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 |
|
|
hi Ken,
Ken K3IU schrieb am 28 Apr 2008 um 14:20: > With respect to your second problem, the mic high / low setting is > working on #202 with latest firmware. It is easy to demonstrate if you set > the MAIN:MIC SEL to high (rP.H in my case), set compression to zero(0), and > MIC gain to zero(0), and the METER to display the ALC. Tap the XMIT button > to key transmitter, speak into mic and increase the MIC gain to produce an > ALC indication of 4-5. Then reset the the MAIN:MIC SEL to low (rP.L in my > case). Now, without changing the MIC gain or the compression, tap the XMIT > button and speak into mic. I see no ALC action at this time. This clearly > indicates that the high / low setting is working. 73, Ken Wagner K3IU K3 you are right! with this method I find the same performance like you. Is a maximum power output of 45 Watt peak in SSB normal? (mesured with a LP100) Power with CW is showing 100W with the same instrument. 73! de Werner OE9FWV -- Good judgment comes from experience, and a lot of that comes from bad judgment. Email powered by Pegasus Mail free at <http://www.pmail.com> Homepage: <http://www.qsl.net/oe9fwv/> Fone +43 5522 75013 Fax +43 820 555 85 2621 Mobile +43 664 6340014 Elecraft K2 #5203 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
Hi again, Werner:
I can't speak to what you might see on your LP100 meter. I know nothing about it except that is held out to be good! Since I have very little experience with SSB, I'd best not suggest what might be normal :-). I have a Diamond SX-200 wattmeter and in the Averaging position I see a max of about 45 - 50 watts and in the so-called PEP position I see anywhere between 60 and 90 watts indicated. That is with the Heil ProSet from Elecraft, mic gain set to 8, and Compression set to 16. 73, Ken K3IU ~~~~~~~~~~~~~~~~~~~~~~~ Dr. Werner Furlan wrote: > hi Ken, > > Ken K3IU schrieb am 28 Apr 2008 um 14:20: > > >> With respect to your second problem, the mic high / low setting is >> working on #202 with latest firmware. It is easy to demonstrate if you set >> the MAIN:MIC SEL to high (rP.H in my case), set compression to zero(0), and >> MIC gain to zero(0), and the METER to display the ALC. Tap the XMIT button >> to key transmitter, speak into mic and increase the MIC gain to produce an >> ALC indication of 4-5. Then reset the the MAIN:MIC SEL to low (rP.L in my >> case). Now, without changing the MIC gain or the compression, tap the XMIT >> button and speak into mic. I see no ALC action at this time. This clearly >> indicates that the high / low setting is working. 73, Ken Wagner K3IU K3 >> > > you are right! > with this method I find the same performance like you. > > Is a maximum power output of 45 Watt peak in SSB normal? > (mesured with a LP100) > Power with CW is showing 100W with the same instrument. > > > 73! de Werner OE9FWV > > Elecraft mailing list Post to: [hidden email] 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 |
|
|
On sx-200 that is normal for all 100 watt rigs.
Your output is normal. Tom LA1PHA ----- Original Message ----- From: "Ken K3IU" <[hidden email]> To: <[hidden email]> Cc: <[hidden email]> Sent: Monday, April 28, 2008 9:23 PM Subject: Re: [Elecraft] K3: two problems > Hi again, Werner: > > I can't speak to what you might see on your LP100 meter. I know nothing > about it except that is held out to be good! Since I have very little > experience with SSB, I'd best not suggest what might be normal :-). > > I have a Diamond SX-200 wattmeter and in the Averaging position I see a > max of about 45 - 50 watts and in the so-called PEP position I see > anywhere between 60 and 90 watts indicated. That is with the Heil ProSet > from Elecraft, mic gain set to 8, and Compression set to 16. > > 73, > Ken K3IU > ~~~~~~~~~~~~~~~~~~~~~~~ > Dr. Werner Furlan wrote: >> hi Ken, >> Ken K3IU schrieb am 28 Apr 2008 um 14:20: >> >> >>> With respect to your second problem, the mic high / low setting is >>> working on #202 with latest firmware. It is easy to demonstrate if you >>> set >>> the MAIN:MIC SEL to high (rP.H in my case), set compression to zero(0), >>> and >>> MIC gain to zero(0), and the METER to display the ALC. Tap the XMIT >>> button >>> to key transmitter, speak into mic and increase the MIC gain to produce >>> an >>> ALC indication of 4-5. Then reset the the MAIN:MIC SEL to low (rP.L in >>> my >>> case). Now, without changing the MIC gain or the compression, tap the >>> XMIT >>> button and speak into mic. I see no ALC action at this time. This >>> clearly >>> indicates that the high / low setting is working. 73, Ken Wagner K3IU K3 >>> >> >> you are right! >> with this method I find the same performance like you. >> Is a maximum power output of 45 Watt peak in SSB normal? >> (mesured with a LP100) >> Power with CW is showing 100W with the same instrument. >> >> >> 73! de Werner OE9FWV >> >> > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > 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 > > > > > -- > No virus found in this incoming message. > Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.5/1400 - Release > Date: 27.04.2008 09:39 > > -- Jeg bruker gratisversjonen av SPAMfighter for privatbrukere. Den har fjernet 433 søppelpostmeldinger til nå. Betalende brukere har ikke denne meldingen i e-postene sine. Få tak i SPAMfighter gratis her: http://www.spamfighter.com/lno _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
In reply to this post by oe9fwv
On Mon, 28 Apr 2008 21:10:25 +0100, Dr. Werner Furlan wrote:
Werner, I get similar results to you. This is using the LP-100A in peak hold mode, where the speed of it's response is very fast. I need a COMP setting of around 20 to get the commanded 100W peak. With my K3 into a dummy load and looking with a scope it is apparent that the peak RF signal changes by around 50% over the range of the COMP control. This may be the effect of the ALC, but in a well designed system should not happen. The ALC should respond to peak not average. 73 Stewart G3RXQ > you are right! > with this method I find the same performance like you. > > Is a maximum power output of 45 Watt peak in SSB normal? > (mesured with a LP100) > Power with CW is showing 100W with the same instrument. > > > 73! de Werner OE9FWV _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
In reply to this post by Ken Wagner K3IU
hi Ken,
thank you for answering, Ken K3IU schrieb am 28 Apr 2008 um 15:23: > I have a Diamond SX-200 wattmeter and in the Averaging position I see a max > of about 45 - 50 watts and in the so-called PEP position I see anywhere > between 60 and 90 watts indicated. That is with the Heil ProSet from > Elecraft, mic gain set to 8, and Compression set to 16. my mic gain settings were much higher, I tried up to 60 but it did not change much. But there is an increase in output after some time of QSO. I have seen up to 100W after some time. But then it will suddenly go back to 50 Watts when whistling. 73! de Werner OE9FWV -- How many Zen Masters does it take a light bulb to change? Email powered by Pegasus Mail free at <http://www.pmail.com> Homepage: <http://www.qsl.net/oe9fwv/> Fone +43 5522 75013 Fax +43 820 555 85 2621 Mobile +43 664 6340014 Elecraft K2 #5203 K3 #656 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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: [hidden email] 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 |
|
|
In reply to this post by oe9fwv
Today the 28th of October 2008 K3 Number #775 Arrived.
It was ordered on October 19, 2007, and is an assembled 100 watt unit. Starting to test it out now and will see how it plays. 73 Bruce N9BX _______________________________________ No viruses found in this outgoing message Scanned by iolo AntiVirus 1.5.3.5 http://www.iolo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
In reply to this post by Brian Lloyd-6
CONTENTS DELETED
The author has deleted this message.
|
|
|
In reply to this post by oe9fwv
quick addon. I found something weird by experimenting:
I can "fix" the problem, when I change the frequency offset of my 2.7 kHz filter. On the filter the offset frequency is marked -0.89. If I set the filter offset to less than -.70 the tuner finds a match on all bands tested. Regarding the mic gain / ALC problem I'll go to a friend with equipment and look at the spectrum. I agree that also with a good peak wattmeter it is not possible to see the spectrum ;-) 73! de Werner OE9FWV |
Re: Measuring power output of an SSB transmitter
|
|
In reply to this post by G4LNA
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: [hidden email] >> 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: [hidden email] 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: Measuring power output of an SSB transmitter
|
|
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 "aaaa...". 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. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com * KComm - http://www.g4ilo.com/kcomm.html * KTune - http://www.g4ilo.com/ktune.html |
Re: 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 "aaaa...". 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: [hidden email] 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 |
|
|
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
|
Re: 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: [hidden email] 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: 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: [hidden email] > 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: [hidden email] 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: 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: [hidden email] > > 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: [hidden email] > 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: [hidden email] 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: 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" <[hidden email]> To: "Romanchik Dan" <[hidden email]> Cc: "Mailing List Elecraft" <[hidden email]> 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: [hidden email] >> > 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: [hidden email] >> 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: [hidden email] > 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: [hidden email] 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: 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" <[hidden email]> > To: "Romanchik Dan" <[hidden email]> > Cc: "Mailing List Elecraft" <[hidden email]> > 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: [hidden email] >>> > 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: [hidden email] >>> 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: [hidden email] >> 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: [hidden email] > 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: [hidden email] 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 |
«
Return to Elecraft
|
1 view|%1 views
| Free forum by Nabble | Edit this page |