Funny power measurements
Locked
 
|
I created what I thought was a reliable method of measuring the power out of
my K2 and am puzzled by the results. What I did was: 1. Built the RF probe from the K2 manual onto a 50 ohm dummy load. 2. Attach that to one of the antenna connections on my KAT2. 3. Tune the load on all bands at the band-center frequency to be measured. 4. Attach my DMM to the probe connection points. The table below shows my voltage measurements and computed power. I am very puzzled about 80- meters and have done that one twice without significant difference. The top end of 10 meters resulted in HiCur=3.00 so that one may need some help but only that one. I am using a 5 amp supply so that should not be an issue. Anybody with any ideas as to where I should start untangling things? Fran P.S. If the table below does not look ve4ry good, just paste it into notepad and it should be more easily read. -------------------------------------------------------- | Freq (Mhz) | V (RMS) || Watts for R = 50 | | PwrSet-> | 1 | 4 | 10 || 1 | 4 | 10 | |------------+------+------+------++------+------+-------| | 3.500 | 3.6 | 14.4 | 14.4 || 0.26 | 4.15 | 4.15 | | 3.750 | 6.2 | 21.8 | 21.7 || 0.76 | 9.50 | 9.42 | | 4.000 | 6.2 | 20.8 | 20.8 || 0.76 | 8.65 | 8.65 | |------------+------+------+------++------+------+-------| | 7.000 | 7.9 | 14.2 | 20.3 || 1.25 | 4.03 | 8.24 | | 7.150 | 8.7 | 15.5 | 21.6 || 1.50 | 4.81 | 9.33 | | 7.300 | 8.2 | 14.6 | 20.5 || 1.33 | 4.26 | 8.41 | |------------+------+------+------++------+------+-------| | 10.100 | 8.2 | 10.7 | 18.3 || 1.35 | 2.29 | 6.70 | | 10.125 | 8.2 | 10.7 | 18.2 || 1.33 | 2.29 | 6.62 | | 10.150 | 8.2 | 10.7 | 18.1 || 1.33 | 2.29 | 6.55 | |------------+------+------+------++------+------+-------| | 14.000 | 9.8 | 10.7 | 22.3 || 1.90 | 2.29 | 9.95 | | 14.175 | 10.2 | 11.2 | 22.7 || 2.06 | 2.51 | 10.31 | | 14.350 | 8.0 | 8.7 | 20.1 || 1.26 | 1.51 | 8.08 | |------------+------+------+------++------+------+-------| | 18.068 | 7.2 | 13.0 | 16.7 || 1.02 | 3.38 | 5.58 | | 18.118 | 7.3 | 13.3 | 16.9 || 1.05 | 3.54 | 5.71 | | 18.168 | 7.3 | 13.4 | 16.9 || 1.06 | 3.59 | 5.71 | |------------+------+------+------++------+------+-------| | 21.000 | 9.0 | 12.8 | 20.0 || 1.63 | 3.28 | 8.00 | | 21.225 | 8.8 | 12.6 | 19.7 || 1.53 | 3.18 | 7.76 | | 21.450 | 7.8 | 11.2 | 18.8 || 1.20 | 2.51 | 7.07 | |------------+------+------+------++------+------+-------| | 24.890 | 8.6 | 12.8 | 19.8 || 1.48 | 3.28 | 7.84 | | 24.940 | 8.2 | 12.4 | 19.5 || 1.34 | 3.08 | 7.61 | | 24.990 | 7.8 | 11.9 | 19.1 || 1.23 | 2.83 | 7.30 | |------------+------+------+------++------+------+-------| | 28.000 | | 14.6 | 19.5 || | 4.26 | 7.61 | | 28.400 | | 13.9 | 18.9 || | 3.86 | 7.14 | | 28.800 | | 9.7 | 15.5 || | 1.88 | 4.81 | -------------------------------------------------------- Expect | 7.07 | 14.14| 22.36 _______________________________________________ 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: Funny power measurements
|
|
Fran, it's almost impossible to get a decent power reading by measuring the
RF voltage at the load unless the load has a very, very low SWR. No common SWR meter is capable of showing when your load is well enough matched to give you any significant accuracy. That is, a small mismatch that won't hardly cause your SWR meter to wiggle is enough to cause very serious errors in your power measurement. The sensitivity of most SWR meters drops with frequency too, so 80 meters is usually the least-accurate band! The simple fact is that it does not make one whit of difference whether the load shows an SWR of 1:1 or 1.2:1 to a decently-designed transmitter, so SWR meters are not designed to show you that difference accurately, but it can make a big difference in the RF voltage across the load. You really, really need a good non-reactive 50 ohm dummy load for these tests. Ron AC7AC _______________________________________________ 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 Francis Belliveau
Fran,
First, you said 'tune the load' -- there should be no tuner of any kind on the output of the K2 when measuring power into a 50 ohm dummy load. The varaition of power within any band can and likely is) a result of an input impedance varaition in the tuner. If you are using the KAT2, put it into one of the bypass states (see the KAT2 manual). Secondly, the accuracy of your power measurement is highly dependent on the dummy load. If you have a good antenna analyzer, check the dummy load at all frequencies of interest - if the dummy load is truly good, it will have a reactance of zero and a pure resistance of 50 ohms. A precision dummy load should be within 1% of those values - if yours is otherwise, you can take steps to calculate the true power, but if there is any evidence of reactance in the load, the math becomes non-trivial. 73, Don W3FPR > -----Original Message----- > > I created what I thought was a reliable method of measuring the > power out of > my K2 and am puzzled by the results. What I did was: > > 1. Built the RF probe from the K2 manual onto a 50 ohm dummy load. > 2. Attach that to one of the antenna connections on my KAT2. > 3. Tune the load on all bands at the band-center frequency to be > measured. > 4. Attach my DMM to the probe connection points. > > The table below shows my voltage measurements and computed power. > I am very > puzzled about 80- meters and have done that one twice without significant > difference. > > The top end of 10 meters resulted in HiCur=3.00 so that one may need some > help but only that one. I am using a 5 amp supply so that should > not be an > issue. > > _______________________________________________ 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 |
|
|
The math is already more complex than most folks realize. The output
of the diode detector is not RMS, but rather peak. So, you need to multiply it by SQRT(2) to get the real voltage to work with. On top of that, you should add in the diode drop, which is variable based on the current going through the diode, which, of course, is based on the RF voltage. 1N4148s have rather high voltage drop that can greatly alter the output voltage. We use 1N5711 diodes in our power meters since they have a much lower forward voltage drop than the 1N4148s. Even still, at low power levels they add in some error to the calculations. I suspect the load isn't as critical as others believe, as long as it is within a few percent of the "estimated" load value. Yes, the best accuracy will be with a purely resistive load at 50 ohms (if that is what you need the load to be), but remember that other component tolerances (including those in the voltmeter) will cause variances in the readings. Still, if you are careful, you should be able to get amazingly good results. It appears that if Fran were to compare his calculated results with a well calibrated watt meter, he may find his results off by a factor of two, not including the diode drop! On Jul 23, 2006, at 7:57 PM, Don Wilhelm wrote: > Fran, > Secondly, the accuracy of your power measurement is highly > dependent on the > dummy load. If you have a good antenna analyzer, check the dummy > load at > all frequencies of interest - if the dummy load is truly good, it > will have > a reactance of zero and a pure resistance of 50 ohms. A precision > dummy > load should be within 1% of those values - if yours is otherwise, > you can > take steps to calculate the true power, but if there is any > evidence of > reactance in the load, the math becomes non-trivial. - Jack Brindle, W6FB ------------------------------------------------------------------------ --------------------- _______________________________________________ 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: Funny power measurements
|
|
Okay, I guess I left out some critical details from my original post.
I am using a 50 ohm load that is intended to be used to convert test equipment from hi-impedence input to 50 ohms. It is labled 50 ohms and measures 50 ohms with my DMM. It should be purely resistive and I do not have any equipment to prove that it is. The need to load it properly using the KAT2 was only because I wanted the KAT2 in-circuit for improved forward power measurement within the K2. I knew that it would need to load things to cancel itself out. Based upon what Ron, Don and Jack have said, I guess that I should remove the KAT2 and RF probe and try something similar to what I tried last time I attempted to understand how well this radio tracks against the published specifications. Would it be reasonable to just place a short piece of coax between the load and an O'Scope, measure the peak-to-peak voltage, divide by 2*SQRT(2) and go from there? Would this require knowing the coax velocity factor and dealing with prioper lengths of coax based upon wavelength (half or quarter) at the different frequencies? I ask these questions because last time I tried using my Scope to make these measurements, the measurements were obviously incorrect because they indicated that my rig was way more than 100% efficient. What I expect is that I can make apropriate measurements at 3 points on each band and see that I get no more that 10% variation across said band and from band-to-band. I expect that I have a problem on 10 Meters because I am getting a HiCur indication at 3 amps when set for 10 watts, so something needs changing there. However, until I have trustable measurements on the other bands, I expect that untangling the issues will be impossible. Help from the experts is needed on how to make such measurements without fancy RF power meters. Obviously a purely resistive 50 ohm load is the first requirement, and I believe that I have that. 73, Fran _______________________________________________ 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: Funny power measurements
|
|
Sure, Fran, an O'scope is a good way to measure the voltage. I'd suggest a
good 10:1 probe on that scope instead of driving the vertical input directly. Many scopes have a 50-ohm termination at their input that can throw the readings way off since the rig would see 25 ohms looking into both of the scope and dummy load in parallel. Also, the scope termination is not designed to dissipate any power and you'd likely destroy it with any significant power. The 10:1 probe isolates the scope from the dummy load. Divide the Vp-p reading you measure with the scope by 2.82 to get Vrms and go from there: (Vrms)^2/50 = watts. Ron AC7AC -----Original Message----- Okay, I guess I left out some critical details from my original post. I am using a 50 ohm load that is intended to be used to convert test equipment from hi-impedence input to 50 ohms. It is labled 50 ohms and measures 50 ohms with my DMM. It should be purely resistive and I do not have any equipment to prove that it is. The need to load it properly using the KAT2 was only because I wanted the KAT2 in-circuit for improved forward power measurement within the K2. I knew that it would need to load things to cancel itself out. Based upon what Ron, Don and Jack have said, I guess that I should remove the KAT2 and RF probe and try something similar to what I tried last time I attempted to understand how well this radio tracks against the published specifications. Would it be reasonable to just place a short piece of coax between the load and an O'Scope, measure the peak-to-peak voltage, divide by 2*SQRT(2) and go from there? Would this require knowing the coax velocity factor and dealing with prioper lengths of coax based upon wavelength (half or quarter) at the different frequencies? I ask these questions because last time I tried using my Scope to make these measurements, the measurements were obviously incorrect because they indicated that my rig was way more than 100% efficient. What I expect is that I can make apropriate measurements at 3 points on each band and see that I get no more that 10% variation across said band and from band-to-band. I expect that I have a problem on 10 Meters because I am getting a HiCur indication at 3 amps when set for 10 watts, so something needs changing there. However, until I have trustable measurements on the other bands, I expect that untangling the issues will be impossible. Help from the experts is needed on how to make such measurements without fancy RF power meters. Obviously a purely resistive 50 ohm load is the first requirement, and I believe that I have that. 73, Fran _______________________________________________ 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 Francis Belliveau
Fran,
You are correct in leaving the KAT2 out of the picture for that measurement - unless the KAT2 is in a bypass state. The addition of extra tuning elements (the tuner L and C values) can create a tuning peak that is unaccounted for in the relationship that you are trying to verify. Too many variables cause un-needed confusion. If you have a 10X probe for the 'scope you can make accurate RF Voltage measurements. Check the probe and 'scope calibration first, most 'scopes have a built-in calibrator that can allow you to check that a nice clean square wave is displayed (if not adjust the compensating cap in the probe), and also check that the vertical deflection is correct based on the internal calibrator. Apply the 10X probe at the dummy load location rather than at the signal generator (K2) end for the better accuracy. Be aware of the frequencies that you will be testing and the specified frequency limits of your 'scope and probe. With my 100 mHz 'scope and my 150 MHz rated probes, I find the 'scope displayed peak to peak voltage is correct through 15 meters and it drops off noticably at 10 meters. This is a frequency factor of approximately 5 (100 MHz to 20 MHz) where I can depend on the displayed voltage being accurate. Check your equipment before simply believing that it is telling you what you are seeing - instruments sometimes 'tell falsehoods' - know your equipment, and trust it only to the extent that it has proven itself. Once you know that you have good RF Voltage measurements, it is a simple matter to compute the power. The standard method of first converting to RMS voltage and then calculating will work, but you can also use formula reduction to do it all in one 'fell swoop' - the reduced formula for power from resistance and peak to peak voltage is: Power = (Vp-p)squared/8R, so for a 50 ohm load, it is a easy matter on most calculators to obtain the square of the peak to peak voltage and divide by 400. A 40 volt peak to peak RF Voltage will be 4 watts of power into a 50 ohm load. The derivation of this relationship is an "exercise left to the student" <G>. You may want to do calculation of the potential error values too. You should be aware that the potential percentage error of your power calculation will be proportional to 2 times your ability to correctly read the peak to peak voltage and also directly proportional to the tolerance of your dummy load. The net of all that is to say you will have to read the RF voltage carefully. A reading of 40 volts p-p will be 4 watts, but if your reading is in error by 1 volt (2.5%), the error (at that power level) will be 0.2 watts (or 5%) - the percentages will hold true for all power levels, the actual error value will have to be computed for any particular level. All that is not to say that such measurements are bad - indeed quite the opposite, for I consider this method to be the best available for the equipment I have. It is just valuable to be able to quantify how far off the mark your readings and results can be due to whatever variables are beyond our control or abilities - that is why it is important to understand the limits of whatever equipment may be used in the measurements - we then know whether any 'problems' are real or are the result of measurement tolerances. If your goal is to have less than 10% power output variation across each band, I would expect that you could achieve that for all bands except for 10 meters (10 meters is quite broad). The K2's power controlling ALC will also be a factor, and can contribute to a raw variation of up to 10% in addition to your potential measurement error. You can minimize the K2 power ALC error by taking many readings at the same frequency (I would say averaging 10 readings should be sufficient). If you do not average, and you read the RF voltage to within 1 volt, you could state that a 15% variation in readings would indicate that the 10% spec is met. 73, Don W3FPR > -----Original Message----- > > I am using a 50 ohm load that is intended to be used to convert test > equipment from hi-impedence input to 50 ohms. It is labled 50 ohms and > measures 50 ohms with my DMM. It should be purely resistive and I do not > have any equipment to prove that it is. > > The need to load it properly using the KAT2 was only because I wanted the > KAT2 in-circuit for improved forward power measurement within the K2. I > knew that it would need to load things to cancel itself out. > > Based upon what Ron, Don and Jack have said, I guess that I should remove > the KAT2 and RF probe and try something similar to what I tried > last time I > attempted to understand how well this radio tracks against the published > specifications. > > Would it be reasonable to just place a short piece of coax > between the load > and an O'Scope, measure the peak-to-peak voltage, divide by > 2*SQRT(2) and go > from there? > > Would this require knowing the coax velocity factor and dealing > with prioper > lengths of coax based upon wavelength (half or quarter) at the different > frequencies? > > I ask these questions because last time I tried using my Scope to > make these > measurements, the measurements were obviously incorrect because they > indicated that my rig was way more than 100% efficient. > > What I expect is that I can make apropriate measurements at 3 > points on each > band and see that I get no more that 10% variation across said > band and from > band-to-band. I expect that I have a problem on 10 Meters because I am > getting a HiCur indication at 3 amps when set for 10 watts, so something > needs changing there. However, until I have trustable measurements on the > other bands, I expect that untangling the issues will be impossible. > > Help from the experts is needed on how to make such measurements without > fancy RF power meters. Obviously a purely resistive 50 ohm load is the > first requirement, and I believe that I have that. > > 73, > Fran > _______________________________________________ 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 |
|
|
I did fail to point out that by doing these measurements, you will only be
verifying that the K2 firmware is capable of controlling the power to within 10% by its ALC control algorithms. As long as the power is kept below the maximunm that the transmit chain will produce, the Power Control ALC will keep the output level within those 10% bounds, and in the process compensate for any weak points in the transmit chain (such as a mistuned bandpass filter). I believe the K2 is unique in the way it controls the power output, and the method used will compensate for gain variations through the transmit chain as long as it is operating below the maximum gain limits. So Fran, your measurements will really only be testing the ability of the firmware to track the requested power setting. If your goal is to test the gain variation through a band (i.e. checking the bandpass filter bandwidth), you will have to either operate the K2 at max power or disable the Power control ALC and use a fixed amount of BFO injection for your test. 73, Don W3FPR > -----Original Message----- > > Fran, > > You are correct in leaving the KAT2 out of the picture for that > measurement - unless the KAT2 is in a bypass state. The addition of extra > tuning elements (the tuner L and C values) can create a tuning > peak that is > unaccounted for in the relationship that you are trying to > verify. Too many > variables cause un-needed confusion. > > If you have a 10X probe for the 'scope you can make accurate RF Voltage > measurements. Check the probe and 'scope calibration first, most 'scopes > have a built-in calibrator that can allow you to check that a nice clean > square wave is displayed (if not adjust the compensating cap in > the probe), > and also check that the vertical deflection is correct based on > the internal > calibrator. > > Apply the 10X probe at the dummy load location rather than at the signal > generator (K2) end for the better accuracy. > > Be aware of the frequencies that you will be testing and the specified > frequency limits of your 'scope and probe. With my 100 mHz 'scope and my > 150 MHz rated probes, I find the 'scope displayed peak to peak voltage is > correct through 15 meters and it drops off noticably at 10 > meters. This is > a frequency factor of approximately 5 (100 MHz to 20 MHz) where I > can depend > on the displayed voltage being accurate. Check your equipment > before simply > believing that it is telling you what you are seeing - > instruments sometimes > 'tell falsehoods' - know your equipment, and trust it only to the extent > that it has proven itself. > > Once you know that you have good RF Voltage measurements, it is a simple > matter to compute the power. The standard method of first > converting to RMS > voltage and then calculating will work, but you can also use formula > reduction to do it all in one 'fell swoop' - the reduced formula for power > from resistance and peak to peak voltage is: Power = (Vp-p)squared/8R, so > for a 50 ohm load, it is a easy matter on most calculators to obtain the > square of the peak to peak voltage and divide by 400. A 40 volt peak to > peak RF Voltage will be 4 watts of power into a 50 ohm load. The > derivation > of this relationship is an "exercise left to the student" <G>. > > You may want to do calculation of the potential error values too. > You should > be aware that the potential percentage error of your power > calculation will > be proportional to 2 times your ability to correctly read the peak to peak > voltage and also directly proportional to the tolerance of your > dummy load. > The net of all that is to say you will have to read the RF voltage > carefully. A reading of 40 volts p-p will be 4 watts, but if your reading > is in error by 1 volt (2.5%), the error (at that power level) will be 0.2 > watts (or 5%) - the percentages will hold true for all power levels, the > actual error value will have to be computed for any particular level. > > All that is not to say that such measurements are bad - indeed quite the > opposite, for I consider this method to be the best available for the > equipment I have. It is just valuable to be able to quantify how far off > the mark your readings and results can be due to whatever variables are > beyond our control or abilities - that is why it is important to > understand > the limits of whatever equipment may be used in the measurements - we then > know whether any 'problems' are real or are the result of measurement > tolerances. > > If your goal is to have less than 10% power output variation across each > band, I would expect that you could achieve that for all bands > except for 10 > meters (10 meters is quite broad). The K2's power controlling > ALC will also > be a factor, and can contribute to a raw variation of up to 10% > in addition > to your potential measurement error. You can minimize the K2 power ALC > error by taking many readings at the same frequency (I would say averaging > 10 readings should be sufficient). If you do not average, and > you read the > RF voltage to within 1 volt, you could state that a 15% variation in > readings would indicate that the 10% spec is met. > > 73, > Don W3FPR > > > > -----Original Message----- > > > > > I am using a 50 ohm load that is intended to be used to convert test > > equipment from hi-impedence input to 50 ohms. It is labled 50 ohms and > > measures 50 ohms with my DMM. It should be purely resistive > and I do not > > have any equipment to prove that it is. > > > > The need to load it properly using the KAT2 was only because I > wanted the > > KAT2 in-circuit for improved forward power measurement within the K2. I > > knew that it would need to load things to cancel itself out. > > > > Based upon what Ron, Don and Jack have said, I guess that I > should remove > > the KAT2 and RF probe and try something similar to what I tried > > last time I > > attempted to understand how well this radio tracks against the published > > specifications. > > > > Would it be reasonable to just place a short piece of coax > > between the load > > and an O'Scope, measure the peak-to-peak voltage, divide by > > 2*SQRT(2) and go > > from there? > > > > Would this require knowing the coax velocity factor and dealing > > with prioper > > lengths of coax based upon wavelength (half or quarter) at the different > > frequencies? > > > > I ask these questions because last time I tried using my Scope to > > make these > > measurements, the measurements were obviously incorrect because they > > indicated that my rig was way more than 100% efficient. > > > > What I expect is that I can make apropriate measurements at 3 > > points on each > > band and see that I get no more that 10% variation across said > > band and from > > band-to-band. I expect that I have a problem on 10 Meters because I am > > getting a HiCur indication at 3 amps when set for 10 watts, so something > > needs changing there. However, until I have trustable > measurements on the > > other bands, I expect that untangling the issues will be impossible. > > > > Help from the experts is needed on how to make such measurements without > > fancy RF power meters. Obviously a purely resistive 50 ohm load is the > > first requirement, and I believe that I have that. > > > > 73, > > Fran > > > _______________________________________________ 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: Funny power measurements
|
|
Okay so now I have made Peak-to-Peak measurements with my O'Scope.
KAT2 removed. 50 Ohm dummy load with 10x Probe attached. Measurements are in the table at the bottom of this email. It should be easier to read in Notepad. Although there is likely a bit more inaccuracy in my readings, consistency should be reasonably maintained. The readings are still mostly all over the place with 20 & 30 meters looking pretty good. 80 meters is still way off base. Something seems wrong here to me but I have no clue where to start chasing things. Fran ----------------------------------------- | Freq (Mhz) | V (P-P) || Watts; R=50 | | PwrSet-> | 4 | 10 || 4 | 10 | |------------+------+------++------+------| | 3.500 | 50.0 | 70.0 || 6.3 | 12.3 | | 3.750 | 74.0 | 86.0 || 13.7 | 18.5 | | 4.000 | 71.0 | 80.0 || 12.6 | 16.0 |HiCur=3.0 |------------+------+------++------+------| | 7.000 | 49.0 | 76.0 || 6.0 | 14.4 | | 7.150 | 53.0 | 79.0 || 7.0 | 15.6 | | 7.300 | 50.0 | 74.0 || 6.3 | 13.7 | |------------+------+------++------+------| | 10.100 | 40.0 | 76.0 || 4.0 | 14.4 | | 10.125 | 40.0 | 74.0 || 4.0 | 13.7 | | 10.150 | 40.0 | 74.0 || 4.0 | 13.7 | |------------+------+------++------+------| | 14.000 | 40.5 | 76.0 || 4.1 | 14.4 | | 14.175 | 43.5 | 78.0 || 4.6 | 15.2 | | 14.350 | 36.5 | 64.0 || 3.3 | 10.2 | |------------+------+------++------+------| | 18.068 | 52.0 | 79.0 || 6.8 | 15.6 | | 18.118 | 53.0 | 80.0 || 7.0 | 16.0 | | 18.168 | 54.0 | 80.0 || 7.3 | 16.0 | |------------+------+------++------+------| | 21.000 | 56.0 | 80.0 || 7.8 | 16.0 | | 21.225 | 53.0 | 77.0 || 7.0 | 14.8 | | 21.450 | 48.0 | 74.0 || 5.8 | 13.7 | |------------+------+------++------+------| | 24.890 | 47.5 | 82.0 || 5.6 | 16.8 | | 24.940 | 46.0 | 82.0 || 5.3 | 16.8 | | 24.990 | 44.0 | 80.0 || 4.8 | 16.0 | |------------+------+------++------+------| | 28.000 | 75.0 | 84.0 || 14.1 | 17.6 | | 28.400 | 72.0 | 81.0 || 13.0 | 16.4 | | 28.800 | 58.0 | 68.0 || 8.4 | 11.6 | ----------------------------------------- Expect | 40.0 | 62.2 | _______________________________________________ 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 |
|
|
Fran,
It appears that you have a problem with the power control mechanism there. Are you using the TUNE button to initiate transmit or are you using a key closure? If you are using the TUNE button, what power does the K2 display indicate? Delay doing your testing across each band and resolve the power control problem first. The power control circuits are not band dependent (even though your data may indicate that it is) - you may have some sort of spurious response in the transmit stages too. Check the frequency with the time base on your 'scope to see if it is anywhere near correct. 73, Don W3FPR > -----Original Message----- > > Okay so now I have made Peak-to-Peak measurements with my O'Scope. > KAT2 removed. > 50 Ohm dummy load with 10x Probe attached. > > Measurements are in the table at the bottom of this email. It should be > easier to read in Notepad. > > Although there is likely a bit more inaccuracy in my readings, consistency > should be reasonably maintained. The readings are still mostly > all over the > place with 20 & 30 meters looking pretty good. 80 meters is still way off > base. Something seems wrong here to me but I have no clue where to start > chasing things. > > Fran > > ----------------------------------------- > | Freq (Mhz) | V (P-P) || Watts; R=50 | > | PwrSet-> | 4 | 10 || 4 | 10 | > |------------+------+------++------+------| > | 3.500 | 50.0 | 70.0 || 6.3 | 12.3 | > | 3.750 | 74.0 | 86.0 || 13.7 | 18.5 | > | 4.000 | 71.0 | 80.0 || 12.6 | 16.0 |HiCur=3.0 > |------------+------+------++------+------| > | 7.000 | 49.0 | 76.0 || 6.0 | 14.4 | > | 7.150 | 53.0 | 79.0 || 7.0 | 15.6 | > | 7.300 | 50.0 | 74.0 || 6.3 | 13.7 | > |------------+------+------++------+------| > | 10.100 | 40.0 | 76.0 || 4.0 | 14.4 | > | 10.125 | 40.0 | 74.0 || 4.0 | 13.7 | > | 10.150 | 40.0 | 74.0 || 4.0 | 13.7 | > |------------+------+------++------+------| > | 14.000 | 40.5 | 76.0 || 4.1 | 14.4 | > | 14.175 | 43.5 | 78.0 || 4.6 | 15.2 | > | 14.350 | 36.5 | 64.0 || 3.3 | 10.2 | > |------------+------+------++------+------| > | 18.068 | 52.0 | 79.0 || 6.8 | 15.6 | > | 18.118 | 53.0 | 80.0 || 7.0 | 16.0 | > | 18.168 | 54.0 | 80.0 || 7.3 | 16.0 | > |------------+------+------++------+------| > | 21.000 | 56.0 | 80.0 || 7.8 | 16.0 | > | 21.225 | 53.0 | 77.0 || 7.0 | 14.8 | > | 21.450 | 48.0 | 74.0 || 5.8 | 13.7 | > |------------+------+------++------+------| > | 24.890 | 47.5 | 82.0 || 5.6 | 16.8 | > | 24.940 | 46.0 | 82.0 || 5.3 | 16.8 | > | 24.990 | 44.0 | 80.0 || 4.8 | 16.0 | > |------------+------+------++------+------| > | 28.000 | 75.0 | 84.0 || 14.1 | 17.6 | > | 28.400 | 72.0 | 81.0 || 13.0 | 16.4 | > | 28.800 | 58.0 | 68.0 || 8.4 | 11.6 | > ----------------------------------------- > Expect | 40.0 | 62.2 | > _______________________________________________ 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 |