KX1 Spring Tune Up Update
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I purchased an Elecraft DL1 because of its' linearity and the built in VDC
test points. Here is the first set of test data. Notes: The SCOPE PWR was Vp-p * .3535 = Pav The TP1 PWR was ((V * 1.414) + 0.15))2 / 50 = P(watts) BAT: 1) DVM 11.93 UNLOADED 2) DVM 11.90 KX1 RECEIVE 3) KX1 11.6 KX1 RECEIVE 4) sDVM 11.72 KX1 TXMT FREQ SCOPE P-P SCOPE PWR TP1 TP1 PWR KX1 PWR KX1 SWR 3.55 30 VP-P 2.25 WATTS 7.60 VDC 2.424 WATTS 2.8-2.9 1.0 7.05 28 1.96 7.22 2.146 2.5-2.8 1.0 10.12 32.5 2.64 8.25 2.79 3.8-4.0 1.0 14.05 27 1.822 6.80 1.79 2.3-2.5 1.0 In every case the scope power is lower than the DL1 power and the KX1 TUNE power is higher than both! The DL1 specification claims 10% Accuracy! Is that 5% plus or minus? The scope used is a Tektronix 465. Its' self calibration shows that it is functioning properly. It was certified when I bought it. It uses a 10 Meg probe. The rig is fully loaded. 4 bands, ATU, power mod and the SMD CW TUNING AID. Projects left to do. 1. Understand why the Scope and the DL1 are not showing the same results. 2. Get the rig and the scope/DL1 readings to agree. 3. If in fact the output is lower than spec for 20 for example, correct that! 4. Explore the possibility of increasing the power output to a full 5 watts. Don has pointed out the fact that more than just the oscillator, final rf transistor and toroids are involved in putting out more than 4 watts. Perhaps an out board power amp using the KX1 as a VFO would be the way to go! QST has had several articles on power amp construction lately! Just for the record, the KX1 is working on all bands. I'll be going over the KX1 manual next. In the mean time, if anyone has any suggestions re: the data presented above, I would be glad to hear from you. Jack AE6GC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Jack,
First, the 10 MHz 'scope probe is your limiting factor on your 'scope measurements. What that 10 MHz rating means is that at 10 MHz, the response of your probe is down -3dB from the actual voltage. If the probe's rating is 'right on the money', the actual voltage measured at 10 MHz will be the measured voltage *divided by* 0.71. Using a 'rule of thumb' that says the measuring instrument must be rated for more than 3 times the frequency of operation, measurement of a 14 MHz signal requires a 'scope probe rated for 45 MHz or greater. Even using the 3 times 'rule of thumb' will produce some inaccuracies at the high frequency end - a better rule is to use a probe (and 'scope) that is rated at 5 times the highest frequency that will be measured for voltage. Note: I do not depend on the voltage readings from my Tek 465B 'scope (rated at 150 MHz) with 100 MHz probes at frequencies much higher than the 15 meter band. With 200 MHz probes, I can depend on it to 30 MHz (in this case, the 'scope limits the frequency rather than the probe). Secondly, the formula in the DL1 manual is in error. I am not certain where all that 'mish-mash' of calculations come from, but it is in error and can certainly be simplified as follows: The diode probe in the DL1 reads the peak RF voltage across 1/2 of the dummy load (the actual zero to peak RF voltage across the 50 ohm dummy load is 2 times the DMM reading plus the diode drop) . The diode drop must be added to the DMM reading before doing any other manipulation with the quantities. A real formula that will work accurately is (Vdmm + Vdiode)*2/25 or if you assume 0.15 volts drop in the diode, the formula is (Vdmm +0.15)*2/25. The derivation of that formula is left as an exercise "for the student", but the results from your DMM readings are: 3.5 MHz - 7.60 volts -> 2.40 Watts 7 MHz - 7.22 volts -> 2.17 Watts 10 MHz - 8.25 volts -> 2.82 Watts 14 MHz - 6.80 volts -> 1.93 Watts. I agree that the formula in the manual will yield results that are "in the ballpark", but they are not correct. If you want to go one step further in accuracy, measure the actual diode voltage drop in your DL1 and use that value instead of the 0.15 volt figure. Once calibrated for the actual diode drop, the DL1 measurement is very accurate if all the factors are considered, even at frequencies well above 30 MHz.. Thirdly, the wattmeter in your KX1 is set a bit too high. Reduce the setting of R1 a bit and try again. Remember that the power reading on the KX1 is +/- 1 (or sometimes 2) digits. So for an actual power of 2.5 watts, the KX1 display can show anywhere between 2.4 and 2.6 watts (or in the extreme case 2.3 and 2.7 watts). 73, Don W3FPR Jack Regan wrote: > I purchased an Elecraft DL1 because of its' linearity and the built in VDC > test points. Here is the first set of test data. > > > > Notes: > > The SCOPE PWR was Vp-p * .3535 = Pav > > The TP1 PWR was ((V * 1.414) + 0.15))2 / 50 = P(watts) > > BAT: 1) DVM 11.93 UNLOADED 2) DVM 11.90 KX1 RECEIVE 3) KX1 11.6 KX1 RECEIVE > 4) sDVM 11.72 KX1 TXMT > > > > FREQ SCOPE P-P SCOPE PWR TP1 TP1 PWR KX1 PWR KX1 SWR > > 3.55 30 VP-P 2.25 WATTS 7.60 VDC 2.424 WATTS 2.8-2.9 1.0 > > 7.05 28 1.96 7.22 2.146 2.5-2.8 1.0 > > 10.12 32.5 2.64 8.25 2.79 3.8-4.0 1.0 > > 14.05 27 1.822 6.80 1.79 2.3-2.5 1.0 > > > > In every case the scope power is lower than the DL1 power and the KX1 TUNE > power is higher than both! > > > > The DL1 specification claims 10% Accuracy! Is that 5% plus or minus? > > > > The scope used is a Tektronix 465. Its' self calibration shows that it is > functioning properly. > > It was certified when I bought it. It uses a 10 Meg probe. > > > > The rig is fully loaded. 4 bands, ATU, power mod and the SMD CW TUNING AID. > > > > Projects left to do. > > > > 1. Understand why the Scope and the DL1 are not showing the same results. > > > > 2. Get the rig and the scope/DL1 readings to agree. > > > > 3. If in fact the output is lower than spec for 20 for example, correct > that! > > > > 4. Explore the possibility of increasing the power output to a full 5 > watts. > Don has pointed out the fact that more than just the oscillator, final > rf > transistor and toroids are involved in putting out more than 4 watts. > Perhaps an > out board power amp using the KX1 as a VFO would be the way to go! > QST has had several > articles on power amp construction lately! > > > > Just for the record, the KX1 is working on all bands. > > > > I'll be going over the KX1 manual next. In the mean time, if anyone has any > suggestions re: the data presented above, I would be glad to hear from you. > > > > Jack AE6GC > > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jack
This update represents a more accurate determination of the power output AND
an adjustment of the KX1 so it would reflect these new, accurate power measurements. The DL1 was used to determine the power output. Some initial confusion occured becasue the DL1's formula for calculating power is not correct! Many thanks to Don Wilhelm for helping sort this out! He has been responding with detailed, accurate and elegant suggestions re: what is going on. The DL1 manual formula is... P(watts)=((V(volts)x1.414)+0.15))2/50 Three things are going on here. The TP1 is connected to the 25 ohm output of the resistor chain, the diode correction is not part of the rms correction and the value of the diode is not as accurate as it could be. Don's formula is... P(watts)=((V(volts)+diode drop))2/25 In his note to me re: this he "left the derivation to the student" and this is the formula I came up with. P(watts)=((V(volts)+diode drop))x 1.414))2/50 When my formula produced a result different than Don's (by a very small positive amount) I jumped to the conclusion that Don's formula was quick and easy ballpark technique! Wrong! The difference in our figures was that Don used the square root of two whereas I used the "standard" approximation 1.414!!!!! I will follow Don's lead and leave the derivation to the student! If you email me I will send you a copy of Don's math!!! Very simple and elegant! To continue... I measured my diode drop and found it to be .330mv so the formula for my DL1 is P(watts)=((V(volts)+0.33))2/25 or P(watts)=((V(volts)+0.33))x (sq. root of 2))2/50 Taking accurate measurements and finding (as previously posted) that the KX1 was showing too high an output I took Don's advice and redid the C9 and the Forward Power adjustments on the KX1. After adjusting the KX1 to show the same readings as the DL1 I now have the following baseline figures on the KX1 with 12VDC(DISP:BAT). FREQ TP1 VDC TP1 WATTS KX1 WATTS KX1 SWR 3.550 7.84 2.60 2.6 1.0 7.040 7.34 2.30 2.3 1.0 10.120 8.45 3.25 3.24-3.26 1.0 14.050 7.03 2.19 2.20 1.0 With the new baseline the agenda has changed. 1. If in fact these outputs are significantly low then correct them thru adjustments, not modifications. They are higher than the 9 VDC specs but are they far enough below the 12VDC specs to bother with. I'll do some reading and research and then decide. Any input or suggestions would be appreciated. 2. Explore the possibility of increasing the power output to a full 5 watts. Don has pointed out the fact that more than just the oscillator, final rf transistor and toroids are involved in putting out more than 4 watts. Perhaps an out board power amp using the KX1 as a VFO would be the way to go! QST has had several articles on power amp construction lately! 3. Understand why the Scope and the DL1 are not showing the same results. 4. Get the scope to match the DL1. Again, just for the record, the KX1 is working on all bands. Jack AE6GC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Jack,
You need to put an 'exponential' symbol between those parentheses and the "2" in those formulas - the voltage must be squared where the formulas you included indicate multiplying by 2. For your power output level, it *may* be a bit low. Check the output with a 13.8 volt supply voltage - if it does not come up close to the 4 watt level on 30 meters (highest output band), you may want to add the "Power Mod" - it is just 2 resistors to change. For those with KX1s already producing 4 watts or more on 30 meters, I do not recommend adding the power mod - see my prior responses on that subject. 73, Don W3FPR Jack Regan wrote: > This update represents a more accurate determination of the power output AND > an adjustment of the KX1 so it would reflect these new, accurate power > measurements. > > > > The DL1 was used to determine the power output. Some initial confusion > occured becasue the DL1's formula for calculating power is not correct! > > > > Many thanks to Don Wilhelm for helping sort this out! He has been > responding with detailed, accurate and elegant suggestions re: what is going > on. > > The DL1 manual formula is... > > > > P(watts)=((V(volts)x1.414)+0.15))2/50 > > > > Three things are going on here. The TP1 is connected to the 25 ohm output of > the resistor chain, the diode correction is not part of the rms correction > and the value of the diode is not as accurate as it could be. > > > > Don's formula is... > > > > P(watts)=((V(volts)+diode drop))2/25 > > > > In his note to me re: this he "left the derivation to the student" and this > is the formula I came up with. > > > > P(watts)=((V(volts)+diode drop))x 1.414))2/50 > > > > When my formula produced a result different than Don's (by a very small > positive amount) I jumped to the conclusion that Don's formula was quick and > easy ballpark technique! Wrong! > > > > The difference in our figures was that Don used the square root of two > whereas I used the "standard" approximation 1.414!!!!! > > > > I will follow Don's lead and leave the derivation to the student! If you > email me I will send you a copy of Don's math!!! Very simple and elegant! > > > > To continue... > > > > I measured my diode drop and found it to be .330mv so the formula for my DL1 > is > > P(watts)=((V(volts)+0.33))2/25 or > > P(watts)=((V(volts)+0.33))x (sq. root of 2))2/50 > > > > Taking accurate measurements and finding (as previously posted) that the KX1 > was showing too high an output I took Don's advice and redid the C9 and the > Forward Power adjustments on the KX1. > > > > After adjusting the KX1 to show the same readings as the DL1 I now have the > following baseline figures on the KX1 with 12VDC(DISP:BAT). > > > > > > FREQ TP1 VDC TP1 WATTS KX1 WATTS KX1 SWR > > 3.550 7.84 2.60 2.6 1.0 > > 7.040 7.34 2.30 2.3 1.0 > > 10.120 8.45 3.25 3.24-3.26 1.0 > > 14.050 7.03 2.19 2.20 1.0 > > > > With the new baseline the agenda has changed. > > > > 1. If in fact these outputs are significantly low then correct them thru > adjustments, not modifications. They are higher than the 9 VDC specs > but are they > far enough below the 12VDC specs to bother with. I'll do some reading > and research > and then decide. Any input or suggestions would be appreciated. > > > > 2. Explore the possibility of increasing the power output to a full 5 > watts. > Don has pointed out the fact that more than just the oscillator, final > rf > transistor and toroids are involved in putting out more than 4 watts. > Perhaps an > out board power amp using the KX1 as a VFO would be the way to go! > QST has had several > articles on power amp construction lately! > > > > 3. Understand why the Scope and the DL1 are not showing the same results. > > > > 4. Get the scope to match the DL1. > > > > Again, just for the record, the KX1 is working on all bands. > > > > Jack AE6GC > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.0.238 / Virus Database: 270.11.23/2016 - Release Date: 03/21/09 17:58:00 > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jack
-----Original Message----- From: Jack Regan [mailto:[hidden email]] Sent: Monday, March 23, 2009 5:06 PM To: 'Jack Regan' Subject: RE: [Elecraft] KX1 Spring Tune Up Update Don has pointed out that the formulas I posted did not appear as superscript 2, indicating a squaring function so I have changed the post to ^2 when squaring is required. This update represents a more accurate determination of the power output AND an adjustment of the KX1 so it would reflect these new, accurate power measurements. The DL1 was used to determine the power output. Some initial confusion occured becasue the DL1's formula for calculating power is not correct! Many thanks to Don Wilhelm for helping sort this out! He has been responding with detailed, accurate and elegant suggestions re: what is going on. The DL1 manual formula is... P(watts)=((V(volts)x1.414)+0.15))^2/50 Three things are going on here. The TP1 is connected to the 25 ohm output of the resistor chain, the diode correction is not part of the rms correction and the value of the diode is not as accurate as it could be. Don's formula is... P(watts)=((V(volts)+diode drop))^2/25 In his note to me re: this he "left the derivation to the student" and this is the formula I came up with. P(watts)=((V(volts)+diode drop))x 1.414))^2/50 When my formula produced a result different than Don's (by a very small positive amount) I jumped to the conclusion that Don's formula was quick and easy ballpark technique! Wrong! The difference in our figures was that Don used the square root of two whereas I used the "standard" approximation 1.414!!!!! I will follow Don's lead and leave the derivation to the student! If you email me I will send you a copy of Don's math!!! Very simple and elegant! To continue... I measured my diode drop and found it to be .330mv so the formula for my DL1 is P(watts)=((V(volts)+0.33))^2/25 or P(watts)=((V(volts)+0.33))x (sq. root of 2))^2/50 Taking accurate measurements and finding (as previously posted) that the KX1 was showing too high an output I took Don's advice and redid the C9 and the Forward Power adjustments on the KX1. After adjusting the KX1 to show the same readings as the DL1 I now have the following baseline figures on the KX1 with 12VDC(DISP:BAT). FREQ TP1 VDC TP1 WATTS KX1 WATTS KX1 SWR 3.550 7.84 2.60 2.6 1.0 7.040 7.34 2.30 2.3 1.0 10.120 8.45 3.25 3.24-3.26 1.0 14.050 7.03 2.19 2.20 1.0 With the new baseline the agenda has changed. 1. If in fact these outputs are significantly low then correct them thru adjustments, not modifications. They are higher than the 9 VDC specs but are they far enough below the 12VDC specs to bother with. I'll do some reading and research and then decide. Any input or suggestions would be appreciated. 2. Explore the possibility of increasing the power output to a full 5 watts. Don has pointed out the fact that more than just the oscillator, final rf transistor and toroids are involved in putting out more than 4 watts. Perhaps an out board power amp using the KX1 as a VFO would be the way to go! QST has had several articles on power amp construction lately! 3. Understand why the Scope and the DL1 are not showing the same results. 4. Get the scope to match the DL1. Again, just for the record, the KX1 is working on all bands. Jack AE6GC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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-----Original Message----- From: Jack Regan [mailto:[hidden email]] Sent: Monday, March 23, 2009 5:34 PM To: 'Jack Regan' Subject: RE: [Elecraft] KX1 Spring Tune Up Final Update! I have tested my output with my newly recalibrated KX1 at 13.9 VDC. These are my outputs in watts: 4.0 on 80 3.3 on 40 4.3 on 30 2.9 on 20 Other than a possible tweaking of the output on twenty I think my spring tune up is done! This thread can be considered closed Many thanks to Don Wilhem for all the help and guidance in getting my baby reading for some serious backpacking!!! Jack AE6GC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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