Re: [Elecraft] KPA500 SWR Calibration
I've been doing a bit of looking at SWR indications. The numbers are factually frightful. With 100 watts forward power and 0.25 watts reflected the SWR is 1.1:1. And with 500 watts forward and 1.25 watts reflected the SWR is still 1.1:1. I believe that says 0.25% of the power is being reflected. But I ask, what is the SWR at the antenna feed point? It is certainly higher than at the transmitter due to feed line losses. In using 100 ft of RG-213 at 14 MHz, the matched line loss is 0.780 dB. With a 1.1:1 SWR the total loss goes up by 0.001 dB and the SWR at the Load is 1.12:1 where Z = 48.25 -j4.63 ohms. All of this is just "killer math" and makes absolutely no difference except to the operator that expects an SWR of 1.0:1 all the time. 73 Bob, K4TAX http://elecraft.365791.n2.nabble.com/K3-SWR-Numerical-Indication-td7643839.html#a7643944 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA500 SWR Calibration
http://elecraft.365791.n2.nabble.com/K3-SWR-Numerical-Indication-td7643839.html#a7643944 On 11/17/2019 2:34 PM, AJ8MH Radio wrote: I know I've seen an explanation somewhere, but it's common to have different readings between the tuner, amp and rig when connected to an antenna. Readings seem to even out when connected to a dummy load...at least in my case. 20 meters is my worst, and the amp will kick out at times. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA500 SWR Calibration
The Breune Bridge directional coupler, designed by and named for Warren Breune of Collins Radio, can be a very accurate and useful device for measuring power. I was lucky to learn about it from W1FB when we both worked at the League. Elecraft has used it in several radios, including the K2. We moved to the two-toroid directional coupler many years ago when we went to higher power designs. This coupler has the advantage that it is the turns count on the toroids that determines the amount of signal available at the sampling port. I believe the KPA500 uses a 30db coupler (not exactly 30db, but very close). There are no capacitors or pots to adjust, so the measurement accuracy essentially is determined by the tolerance of the components in the circuit - namely the resistors and capacitors, as well as the measurement device. These days that is the ADC on the micro controller that is calculating and displaying the measurement. As in all measurement devices, the accuracy is not absolute, but depends on these tolerances. We provide the ability to adjust the measurement data so that if you have a highly accurate and well calibrated device, you can use it to calibrate the power that the Elecraft device displays. Warren Breune created some really fantastic things, including the directional coupler that bears his name. 73! Jack, W6FB > On Nov 18, 2019, at 12:22 PM, ab2tc wrote: > > Hi all, > > I am not familiar with the term "Breune" as applied to SWR bridges or > directional couplers, so I Googled it. As I suspected, it applies to the > single transformer design where the RF voltage is sampled by a capacitive > divider. While these can be made to work adequately well when properly > adjusted, the need for adjustment is a definite disadvantage. As long as the > two transformers in the two transformer design are well matched (ideally > identical) there is no need for any (balance or null) adjustment in this > design. I am happy to see that all of the Elecraft equipment I have seen use > the the two transformer design. > > AB2TC - Knut > > > AJ8MH-Radio.Joe.Hutchens wrote >> I know I've seen an explanation somewhere, but it's common to have >> different readings between the tuner, amp and rig when connected to an >> antenna. Readings seem to even out when connected to a dummy load...at >> least in my case. 20 meters is my worst, and the amp will kick out at >> times. >> >> On 11/17/2019 2:19 PM, Bob McGraw K4TAX wrote: >>> Jack, et.al. >>> >>> Thanks, Yes I see from the circuit it is not a Breune. I have >>> calibrated the indications for power and all is well in that regard. >>> I just see a higher SWR that actually exists. That under certain >>> conditions causes the amp to fault. I'll figure a work-a-round and >>> be able to deal with it. >>> >>> 73 >>> >>> Bob, K4TAX >>> >>> >>> On 11/17/2019 10:12 AM, Jack Brindle wrote: Bob; The KPA500 does not use a Breune style bridge, but rather a true directional coupler. It does not need to be nulled; there is no adjustment. There is an adjustment for the power; see the PWR ADJ setting in the manual. 73! Jack, W6FB >> > > > > > > -- > Sent from: http://elecraft.365791.n2.nabble.com/ > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to jackbrin...@me.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA500 SWR Calibration
Hi all, I am not familiar with the term "Breune" as applied to SWR bridges or directional couplers, so I Googled it. As I suspected, it applies to the single transformer design where the RF voltage is sampled by a capacitive divider. While these can be made to work adequately well when properly adjusted, the need for adjustment is a definite disadvantage. As long as the two transformers in the two transformer design are well matched (ideally identical) there is no need for any (balance or null) adjustment in this design. I am happy to see that all of the Elecraft equipment I have seen use the the two transformer design. AB2TC - Knut AJ8MH-Radio.Joe.Hutchens wrote > I know I've seen an explanation somewhere, but it's common to have > different readings between the tuner, amp and rig when connected to an > antenna. Readings seem to even out when connected to a dummy load...at > least in my case. 20 meters is my worst, and the amp will kick out at > times. > > On 11/17/2019 2:19 PM, Bob McGraw K4TAX wrote: >> Jack, et.al. >> >> Thanks, Yes I see from the circuit it is not a Breune. I have >> calibrated the indications for power and all is well in that regard. >> I just see a higher SWR that actually exists. That under certain >> conditions causes the amp to fault. I'll figure a work-a-round and >> be able to deal with it. >> >> 73 >> >> Bob, K4TAX >> >> >> On 11/17/2019 10:12 AM, Jack Brindle wrote: >>> Bob; >>> >>> The KPA500 does not use a Breune style bridge, but rather a true >>> directional coupler. It does not need to be nulled; there is no >>> adjustment. >>> >>> There is an adjustment for the power; see the PWR ADJ setting in the >>> manual. >>> >>> 73! >>> Jack, W6FB >>> > -- Sent from: http://elecraft.365791.n2.nabble.com/ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA500 SWR Calibration
I know I've seen an explanation somewhere, but it's common to have different readings between the tuner, amp and rig when connected to an antenna. Readings seem to even out when connected to a dummy load...at least in my case. 20 meters is my worst, and the amp will kick out at times. On 11/17/2019 2:19 PM, Bob McGraw K4TAX wrote: Jack, et.al. Thanks, Yes I see from the circuit it is not a Breune. I have calibrated the indications for power and all is well in that regard. I just see a higher SWR that actually exists. That under certain conditions causes the amp to fault. I'll figure a work-a-round and be able to deal with it. 73 Bob, K4TAX On 11/17/2019 10:12 AM, Jack Brindle wrote: Bob; The KPA500 does not use a Breune style bridge, but rather a true directional coupler. It does not need to be nulled; there is no adjustment. There is an adjustment for the power; see the PWR ADJ setting in the manual. 73! Jack, W6FB On Nov 17, 2019, at 6:58 AM, Bob McGraw K4TAX wrote: I need to null the SWR detector on my KPA500. I've not found any adjustment procedure as such. And from the schematic, there is none. I do have a rather precise Bird 50.5 ohm dummy load. I see SWR values higher than 1:1 on the LED display and also on the LCD display on higher frequency bands. I've found that the PWR ADJ does affect not only the indicated power but the FAULT values as well. I am suspect that the SWR error likewise affects the Fault actions. Any thoughts? 73 Bob, K4TAX __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to jackbrin...@me.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to aj8mh-ra...@charter.net -- Joe Hutchens AJ8MH - Radio Marquette, MI __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA500 SWR Calibration
Jack, et.al. Thanks, Yes I see from the circuit it is not a Breune. I have calibrated the indications for power and all is well in that regard. I just see a higher SWR that actually exists. That under certain conditions causes the amp to fault. I'll figure a work-a-round and be able to deal with it. 73 Bob, K4TAX On 11/17/2019 10:12 AM, Jack Brindle wrote: Bob; The KPA500 does not use a Breune style bridge, but rather a true directional coupler. It does not need to be nulled; there is no adjustment. There is an adjustment for the power; see the PWR ADJ setting in the manual. 73! Jack, W6FB On Nov 17, 2019, at 6:58 AM, Bob McGraw K4TAX wrote: I need to null the SWR detector on my KPA500. I've not found any adjustment procedure as such. And from the schematic, there is none. I do have a rather precise Bird 50.5 ohm dummy load. I see SWR values higher than 1:1 on the LED display and also on the LCD display on higher frequency bands. I've found that the PWR ADJ does affect not only the indicated power but the FAULT values as well. I am suspect that the SWR error likewise affects the Fault actions. Any thoughts? 73 Bob, K4TAX __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to jackbrin...@me.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA500 SWR Calibration
Bob; The KPA500 does not use a Breune style bridge, but rather a true directional coupler. It does not need to be nulled; there is no adjustment. There is an adjustment for the power; see the PWR ADJ setting in the manual. 73! Jack, W6FB > On Nov 17, 2019, at 6:58 AM, Bob McGraw K4TAX wrote: > > I need to null the SWR detector on my KPA500. I've not found any adjustment > procedure as such. And from the schematic, there is none. > > I do have a rather precise Bird 50.5 ohm dummy load. I see SWR values higher > than 1:1 on the LED display and also on the LCD display on higher frequency > bands. I've found that the PWR ADJ does affect not only the indicated power > but the FAULT values as well. I am suspect that the SWR error likewise > affects the Fault actions. > > Any thoughts? > > 73 > > Bob, K4TAX > > > > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to jackbrin...@me.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] KPA500 SWR Calibration
I need to null the SWR detector on my KPA500. I've not found any adjustment procedure as such. And from the schematic, there is none. I do have a rather precise Bird 50.5 ohm dummy load. I see SWR values higher than 1:1 on the LED display and also on the LCD display on higher frequency bands. I've found that the PWR ADJ does affect not only the indicated power but the FAULT values as well. I am suspect that the SWR error likewise affects the Fault actions. Any thoughts? 73 Bob, K4TAX __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
