My K3 is working well on PSK31, but I have seen some information about operating digital at 25 watts. Presently I transmit at 25 watts with great success. The comments are that at that low power the fan may not keep the equipment cool enough. One suggestion was to transmit at a higher power, and another was to schedule a break every few minutes to allow the rig to cool. I will appreciate you sharing any information or experience you have. I am getting ready for Winter Field Day and hope to make many PSK31 contacts.
________________________________ From: [email protected] <[email protected]> on behalf of [email protected] <[email protected]> Sent: Tuesday, January 19, 2021 5:56 PM To: [email protected] <[email protected]> Subject: Elecraft Digest, Vol 201, Issue 26 Send Elecraft mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit http://mailman.qth.net/mailman/listinfo/elecraft or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of Elecraft digest..." Today's Topics: 1. Re: K4 Receive Filter question (David Box) 2. Re: K4 Receive Filter question (George Thornton) 3. Re: K4 Receive Filter question (Louandzip) 4. Re: K4 Receive Filter question (Wes) 5. Re: Efficiency of MFJ remotely-tuned loop antennas (Fred Jensen) 6. Absurd remarks about FCC and ARRL notices. (Joseph Shuman) 7. Re: Absurd remarks about FCC and ARRL notices. (kennedyjp) 8. Re: Absurd remarks about FCC and ARRL notices. (Al London) 9. Re: Absurd remarks about FCC and ARRL notices. (Wayne Burdick) 10. Something different, old memories and using the KX3 (Paul GACEK) 11. Re: Something different, old memories and using the KX3 (Dave Sublette) 12. Re: Absurd remarks about FCC and ARRL notices. ([email protected]) 13. Re: Efficiency of MFJ remotely-tuned loop antennas (Alan Bloom) 14. Re: Efficiency of MFJ remotely-tuned loop antennas (Louandzip) 15. Re: Absurd remarks about FCC and ARRL notices. (Barry) 16. Re: Efficiency of MFJ remotely-tuned loop antennas (Eric Garner) ---------------------------------------------------------------------- Message: 1 Date: Tue, 19 Jan 2021 12:51:52 -0600 From: David Box <[email protected]> To: [email protected] Subject: Re: [Elecraft] K4 Receive Filter question Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8; format=flowed Bruce, Below are the receiver sensitivity specs from page 42 of the recently updated manual Sensitivity??? (MDS) (Typical??? values;??? main??? or sub??? RX,??? BW??? =??? 500??? Hz) 0.1-1.5??? MHz*:??? ??? ??? ??? Preamp??? OFF/1/2: -120/-130/-135??? ??? dBm 1.5-23??? MHz:??? ??? ??? ??? ??? ??? ??? Preamp??? OFF/1/2: ??? -120/-132/-137??? dBm 23-54??? MHz:??? ??? ??? ??? ??? ??? ??? ??? Preamp??? OFF/1/2: ??? ??? -120/-132/-141??? dBm *0.1-1.5??? MHz??? MDS??? measured??? at??? RX??? antenna inputs.??? When using??? shared??? RX/TX??? antenna,??? sensitivity decreases??? below??? 1.5 MHz??? due??? to??? intentional??? high-pass??? response??? of T-R??? switch. de Dave K5MWR On 1/19/2021 12:40, BRUCE WW8II wrote: > I work in the 2 to 3 db above the noise floor CW, and 6 to 10 db above the > noise floor on SSB now, (that is why I presently own a K3s and a P3VGA) so > I guess I will have to wait for the real answer. I really cannot > believe that Elecraft did not run their own test. If and when I spend my > cash I am not looking for the pretty blinkie colored lights and a fancy > screen, I want performance. My really big issue is: receiver noise floor, > sensitivity and DSP that does not distort or degrade the incoming signal. > But thank all of you for your input and I truly appreciate all the > comments. > > Bruce > WW8II > > > > On Tue, Jan 19, 2021 at 10:43 AM Louandzip via Elecraft < > [email protected]> wrote: > >> That's not a simple or easy question to answer, especially since there's >> been no independent test of a K4, and there are many different criteria >> that go into it. That said, I'll go out on a limb and say that in most >> all practical situations on the air, it won't be. I say that because I've >> listened to and half-assedly compared a number of very good radios and some >> less good radios on the air. They might sound different, and take some >> tweaking of the controls to make them sound a similar as possible, but in >> the end I couldn't copy sigs better on one than the other. The K3 is really >> good in the tests, and I'm confident the K4 will surpass it, but that's at >> level that will only matter in what I consider to be exceptional >> circumstances. >> >> I'll add that I'm not the radio connoisseur that some are, and what I feel >> is largely the same, others may find hugely different. That doesn't stop me >> from wanting the best, even if I believe it won't make a practical >> difference in my operating. >> >> >> >> >> On Tuesday, January 19, 2021, 12:47:17 AM MST, BRUCE WW8II < >> [email protected]> wrote: >> >> I also would appreciate a real answer to the question. The question is >> will the K4 or K4D be as good or better on receive than my K3s with the >> 2.1kHz and the 200Hz filters. >> >> Bruce WW8II >> >> On Tue, Jan 19, 2021 at 12:56 AM RVZ via Elecraft < >> [email protected]> >> wrote: >> >>> I believe there are no crystal Roofing Filters in the standard K4 model. >>> Yet the manual talks about "one set of receive filters". Please advise >> the >>> type and bandwidth of these filters? (DSP?) >>> >>> From the K4 Manual: There are three models: the basic K4, with one set >> of >>> receive filters and one analog-to-digital converter (ADC); the K4D, with >> a >>> second set of receive filters and a second ADC; and the K4HD, which adds >> a >>> superheterodyne front end that can be enabled as needed to provide even >>> greater dynamic range. The superhet module uses high-performance, >>> narrow-band crystal filters such as those used in the Elecraft K3S. >> Thanks >>> & 73, Dick- K9OM >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[email protected] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to [email protected] >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] > ------------------------------ Message: 2 Date: Tue, 19 Jan 2021 19:13:18 +0000 From: George Thornton <[email protected]> To: BRUCE WW8II <[email protected]>, Louandzip <[email protected]> Cc: elecraft <[email protected]> Subject: Re: [Elecraft] K4 Receive Filter question Message-ID: <mwhpr16mb1694594af532ce3ba7a96cf0b4...@mwhpr16mb1694.namprd16.prod.outlook.com> Content-Type: text/plain; charset="us-ascii" I have followed the Sherwood Receiver test data over the years and I know Elecraft has always been in or near the top spot. I also would be reluctant to upgrade to a K4 if my K3 is the same or pretty close to the same in the key performance characteristics. I wonder whether we are nearing the theoretical limit of what can be gained in receiver performance. The difference among the top eight to ten on the Sherwood list is not likely to be practically significant. -----Original Message----- From: [email protected] <[email protected]> On Behalf Of BRUCE WW8II Sent: Tuesday, January 19, 2021 10:40 AM To: Louandzip <[email protected]> Cc: elecraft <[email protected]> Subject: Re: [Elecraft] K4 Receive Filter question I work in the 2 to 3 db above the noise floor CW, and 6 to 10 db above the noise floor on SSB now, (that is why I presently own a K3s and a P3VGA) so I guess I will have to wait for the real answer. I really cannot believe that Elecraft did not run their own test. If and when I spend my cash I am not looking for the pretty blinkie colored lights and a fancy screen, I want performance. My really big issue is: receiver noise floor, sensitivity and DSP that does not distort or degrade the incoming signal. But thank all of you for your input and I truly appreciate all the comments. Bruce WW8II On Tue, Jan 19, 2021 at 10:43 AM Louandzip via Elecraft < [email protected]> wrote: > That's not a simple or easy question to answer, especially since > there's been no independent test of a K4, and there are many different > criteria that go into it. That said, I'll go out on a limb and say > that in most all practical situations on the air, it won't be. I say > that because I've listened to and half-assedly compared a number of > very good radios and some less good radios on the air. They might > sound different, and take some tweaking of the controls to make them > sound a similar as possible, but in the end I couldn't copy sigs > better on one than the other. The K3 is really good in the tests, and > I'm confident the K4 will surpass it, but that's at level that will > only matter in what I consider to be exceptional circumstances. > > I'll add that I'm not the radio connoisseur that some are, and what I > feel is largely the same, others may find hugely different. That > doesn't stop me from wanting the best, even if I believe it won't make > a practical difference in my operating. > > > > > On Tuesday, January 19, 2021, 12:47:17 AM MST, BRUCE WW8II < > [email protected]> wrote: > > I also would appreciate a real answer to the question. The question > is will the K4 or K4D be as good or better on receive than my K3s with > the 2.1kHz and the 200Hz filters. > > Bruce WW8II > > On Tue, Jan 19, 2021 at 12:56 AM RVZ via Elecraft < > [email protected]> > wrote: > > > I believe there are no crystal Roofing Filters in the standard K4 model. > > Yet the manual talks about "one set of receive filters". Please > > advise > the > > type and bandwidth of these filters? (DSP?) > > > > From the K4 Manual: There are three models: the basic K4, with one > > set > of > > receive filters and one analog-to-digital converter (ADC); the K4D, > > with > a > > second set of receive filters and a second ADC; and the K4HD, which > > adds > a > > superheterodyne front end that can be enabled as needed to provide > > even greater dynamic range. The superhet module uses > > high-performance, narrow-band crystal filters such as those used in the > > Elecraft K3S. > Thanks > > & 73, Dick- K9OM > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[email protected] > > > > This list hosted by: http://www.qsl.net Please help support this > > email list: http://www.qsl.net/donate.html Message delivered to > > [email protected] > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net Please help support this email > list: http://www.qsl.net/donate.html Message delivered to > [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net Please help support this email > list: http://www.qsl.net/donate.html Message delivered to > [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ------------------------------ Message: 3 Date: Tue, 19 Jan 2021 19:38:58 +0000 (UTC) From: Louandzip <[email protected]> Cc: elecraft <[email protected]> Subject: Re: [Elecraft] K4 Receive Filter question Message-ID: <[email protected]> Content-Type: text/plain; charset=UTF-8 I own a radio that's currently #1 on Sherwood's list. My 20 year old K2 is essentially equal at digging weak CW out of the noise (always dominated by band noise and not the noise floor of the rig) in virtually all situations I've run into. The K2 has no KSSB so I don't compare it on SSB. If I was up against a lot of really strong close-by sigs, presumably the new rig would win, but I haven't yet run into a situation with the two rigs side by side where big nearby sigs have actually caused a discernible difference. Comparing SSB with other rigs, the new rig can beat the others on readability of weak sigs in noise, but I don't think it's due to the fundamental performance numbers in these cases but rather the DSP algorithm which makes the difference, and I don't believe this is quantified in the testing done by Sherwood or ARRL, except perhaps in subjective comments in the text of a QST review. . On Tuesday, January 19, 2021, 12:13:20 PM MST, George Thornton <[email protected]> wrote: I have followed the Sherwood Receiver test data over the years and I know Elecraft has always been in or near the top spot. I also would be reluctant to upgrade to a K4 if my K3 is the same or pretty close to the same in the key performance characteristics. I wonder whether we are nearing the theoretical limit of what can be gained in receiver performance. The difference among the top eight to ten on the Sherwood list is not likely to be practically significant. -----Original Message----- From: [email protected] <[email protected]> On Behalf Of BRUCE WW8II Sent: Tuesday, January 19, 2021 10:40 AM To: Louandzip <[email protected]> Cc: elecraft <[email protected]> Subject: Re: [Elecraft] K4 Receive Filter question I work in the 2 to 3 db above the noise floor CW, and 6 to 10 db above the noise floor on SSB now, (that is why I presently own a K3s and a P3VGA)? so I guess I will have to wait for the real answer. I really cannot believe that Elecraft did not run their own test. If and when I spend my cash I am not looking for the pretty blinkie colored lights and a fancy screen, I want performance.? My really big issue is: receiver noise floor, sensitivity and DSP that does not distort or degrade the incoming signal. But thank all of you for your input? and I truly appreciate all the comments. Bruce WW8II On Tue, Jan 19, 2021 at 10:43 AM Louandzip via Elecraft < [email protected]> wrote: >? That's not a simple or easy question to answer, especially since > there's been no independent test of a K4, and there are many different > criteria that go into it.? That said,? I'll go out on a limb and say > that in most all practical situations on the air, it won't be. I say > that because I've listened to and half-assedly compared a number of > very good radios and some less good radios on the air. They might > sound different, and take some tweaking of the controls to make them > sound a similar as possible, but in the end I couldn't copy sigs > better on one than the other. The K3 is really good in the tests, and > I'm confident the K4 will surpass it, but that's at level that will > only matter in what I consider to be exceptional circumstances. > > I'll add that I'm not the radio connoisseur that some are, and what I > feel is largely the same, others may find hugely different. That > doesn't stop me from wanting the best, even if I believe it won't make > a practical difference in my operating. > > > > >? ? On Tuesday, January 19, 2021, 12:47:17 AM MST, BRUCE WW8II < > [email protected]> wrote: > >? I also would appreciate a real answer to the question.? The question > is will the K4 or K4D be as good or better on receive than my K3s with > the 2.1kHz and the 200Hz filters. > > Bruce WW8II > > On Tue, Jan 19, 2021 at 12:56 AM RVZ via Elecraft < > [email protected]> > wrote: > > > I believe there are no crystal Roofing Filters in the standard K4 model. > > Yet the manual talks about "one set of receive filters".? Please > > advise > the > > type and bandwidth of these filters?? (DSP?) > > > > From the K4 Manual:? There are three models: the basic K4, with one > > set > of > > receive filters and one analog-to-digital converter (ADC); the K4D, > > with > a > > second set of receive filters and a second ADC; and the K4HD, which > > adds > a > > superheterodyne front end that can be enabled as needed to provide > > even greater dynamic range. The superhet module uses > > high-performance, narrow-band crystal filters such as those used in the > > Elecraft K3S. > Thanks > > & 73, Dick- K9OM > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[email protected] > > > > This list hosted by: http://www.qsl.net Please help support this > > email list: http://www.qsl.net/donate.html Message delivered to > > [email protected] > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net Please help support this email > list: http://www.qsl.net/donate.html Message delivered to > [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net Please help support this email > list: http://www.qsl.net/donate.html Message delivered to > [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ------------------------------ Message: 4 Date: Tue, 19 Jan 2021 14:07:42 -0700 From: Wes <[email protected]> To: [email protected] Subject: Re: [Elecraft] K4 Receive Filter question Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8; format=flowed I happen to own the K3S that is #5 or Rob's list.? I also got tired of waiting on the K4 and having a burning desire for a new radio I have a month-old TS-890, which is now my primary radio.? The K3S is set up in a receive-only state, sharing the RX antenna out of the '890. A few mornings ago I was tuning 160 near sunrise and copied a fishing buoy 60 Hz above one of the commonly used frequencies (forget which one).? My friend, and local ham, N7DD began calling CQ 60 Hz below the buoy.? Larry runs an Icom 7851, which is very clean and a BIG amplifier.? He is at least S9+40 db.? On the TS-890, cranked down to 80 Hz BW,? I could still copy the buoy which was S6 or so.? On the K3S I heard N7DD calling CQ. Without QRM the rigs are comparable at hearing signals in the noise but the Kenwood sounds better. Wes? N7WS On 1/19/2021 12:38 PM, Louandzip via Elecraft wrote: > I own a radio that's currently #1 on Sherwood's list. My 20 year old K2 is > essentially equal at digging weak CW out of the noise (always dominated by > band noise and not the noise floor of the rig) in virtually all situations > I've run into. The K2 has no KSSB so I don't compare it on SSB. If I was up > against a lot of really strong close-by sigs, presumably the new rig would > win, but I haven't yet run into a situation with the two rigs side by side > where big nearby sigs have actually caused a discernible difference. > Comparing SSB with other rigs, the new rig can beat the others on readability > of weak sigs in noise, but I don't think it's due to the fundamental > performance numbers in these cases but rather the DSP algorithm which makes > the difference, and I don't believe this is quantified in the testing done by > Sherwood or ARRL, except perhaps in subjective comments in the text of a QST > review. . > > On Tuesday, January 19, 2021, 12:13:20 PM MST, George Thornton > <[email protected]> wrote: > > I have followed the Sherwood Receiver test data over the years and I know > Elecraft has always been in or near the top spot. > > I also would be reluctant to upgrade to a K4 if my K3 is the same or pretty > close to the same in the key performance characteristics. > > I wonder whether we are nearing the theoretical limit of what can be gained > in receiver performance. > > The difference among the top eight to ten on the Sherwood list is not likely > to be practically significant. ------------------------------ Message: 5 Date: Tue, 19 Jan 2021 13:35:17 -0800 From: Fred Jensen <[email protected]> To: [email protected] Subject: Re: [Elecraft] Efficiency of MFJ remotely-tuned loop antennas Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8; format=flowed The plates in the two air variables in the [now ancient] ARC-5 command TX from WW2 were very securely welded in place to the rotor axle.? We'd remove many of the rotor plates and re-pad it with a fixed capacitor to spread out the ham band on the dial.? It took a lot of bending back and forth to break the welds.? Lower power loops often use butterfly caps since there is no resistive loss through the rotor connection.? Higher powered loops often use vacuum variables because of the high voltages, although I saw a design not long ago that used two coaxial copper pipes with a PVC pipe as the insulator.? The inside conductor was mounted to a long threaded rod moving it in and out of the outer conductor. In your list of pros, you might note that while the bi-directional primary lobes of the loop when mounted vertically are very broad, the null perpendicular to the plane of the loop is extremely narrow and deep.? You can use it to null out noise or even another signal without sacrificing much of anything in the forward direction. My Alexloop works ok on 30, poorly on 40, and really seems to come into its own on 20 and up. 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County On 1/18/2021 8:54 PM, Alan Bloom wrote: > > There is a reason why top quality variable capacitors often use > welded plates. > > I believe they do weld the capacitor plates and also weld the loop to > the capacitor.? (I don't have one, but that's what I've read.) > > > Yours is a limited theoretical analysis ... not a practical one. > > A number of reviews I have read (including the QST review of August > 1994) have reported comparable performance to full-sized wire antennas > located on the same site.? If the loop is down by, say, 3 dB, that's > only half an S unit, which would hardly? be noticeable in the QSB of a > typical amateur band. > > > As I see it, the advantages of the MFJ-1786 10-30 MHz loop are: > > - Continuous coverage on 6 amateur bands.? A convenient way to cover > all the WARC bands. > - Small and light. > - Omni-directional (when mounted horizontally)? so does not need a rotor. > - No control cable required - control voltage is fed through the coax. > - Narrow bandwidth provides excellent RF selectivity.? Might be good > on Field Day to reduce inter-station QRM. > - Users have reported lower receiver noise compared to wire antennas.? > No doubt that is because the isolated pickup loop prevents feedline > radiation/pickup. > > And the disadvantages: > > - Expensive ($500 list price) > - Less gain than a simple dipole (although you would theoretically > need 6 of them). > - Fiddly to tune.? If you QSY too far you have to re-tune. > - MFJ quality control leaves something to be desired.? (You may have > to open it up when you get it and? make minor repairs.) > - You have to pay attention to the problem of entry of water and/or > bugs into the housing. > - The controller can be damaged by a DC short in the coax e.g. from an > shorting-type antenna switch.? (I don't understand why MFJ didn't > include a fuse or some other way to protect the controller.) > > I probably wouldn't buy the 7-21 MHz MFJ-1788 because of the poor > efficiency at 7 MHz.? I think you'd have a better signal just using > the coax as a random end-fed wire (with a tuner). > > Alan N1AL > > > On 1/18/2021 8:17 PM, David Gilbert wrote: >> >> You are neglecting the losses in various connections in the system >> ... including possibly the construction of the capacitor itself. I >> don't believe that they are insignificant.? There is a reason why top >> quality variable capacitors often use welded plates. >> >> I would also guess that contact resistance is worse for dissimilar >> materials, such as a copper wire to an aluminum tube. >> >> Yours is a limited theoretical analysis ... not a practical one. >> >> Dave?? AB7E >> >> >> >> On 1/18/2021 5:38 PM, Alan Bloom wrote: >>> Well let's see... >>> >>> Radiation resistance of a small loop is 31,171 * (Area / >>> wavelength^2)^2 >>> >>> For a loop with a 91cm diameter at 14 MHz, I believe that comes out >>> to 0.064 ohms. >>> >>> Assuming the loss is due to the RF resistance of the loop: >>> >>> From the internet I get the volume resistivity and skin depth for >>> 6063 aluminum is 0.03 microohms-meter and 23.3 micrometers >>> respectively, so the surface resistivity is 0.03/23.3 = 0.0013 ohms >>> per square.? The outside circumference of the tubing is PI * 1.05" = >>> 3.3" and the loop length is PI * 36" = 113" so the loss resistance >>> is .0013 * 113/3.3 = 0.045 ohms. >>> >>> So I calculate an efficiency of 0.064 / (0.064 + 0.045) = 59% >>> >>> So worse than AEA claimed, but in the ballpark. >>> >>> Alan N1AL >>> >>> >>> >>> >>> On 1/18/2021 3:39 PM, Wayne Burdick wrote: >>>> Hi Alan, >>>> >>>> 72% sounds a bit high. Is this number based on loop size alone ("in >>>> theory")? Or are they taking conductor geometry and other losses >>>> into account? >>>> >>>> Wayne >>>> N6KR >>>> >>>> >>>>> On Jan 18, 2021, at 2:05 PM, Alan Bloom <[email protected]> wrote: >>>>> >>>>> MFJ makes a pair of small, remotely-tuned loop antennas, the >>>>> MFJ-1786 that covers 10-30 MHz and the MFJ-1788 that covers 7 to >>>>> 21+ MHz.? As far as I can tell, the two antennas are identical >>>>> except for the size of the tuning capacitor.? Each consists of a 3 >>>>> foot (91 cm) diameter loop made of aluminum tubing and a plastic >>>>> housing that contains the tuning capacitor, motor, and coupling >>>>> loop. No control cable is required since the control voltage is >>>>> sent from the control box in the shack to the motor in the antenna >>>>> via the coaxial cable. >>>>> >>>>> Before I purchase one of these I wanted to get an idea of the >>>>> efficiency of such a small loop.? MFJ is silent on the subject so >>>>> I did my own calculations.? The calculations and results are on a >>>>> 1-page document that I uploaded to Dropbox and can be downloaded >>>>> here: >>>>> >>>>> https://www.dropbox.com/s/l8mv67cjrck2ssn/MFJ-1786-1788.pdf?dl=0 >>>>> >>>>> My calculations are based on the assumption that the efficiency of >>>>> the MFJ antennas is similar to the (no longer manufactured) AEA >>>>> Isoloop (my reasoning for that is in the document) and that AEA's >>>>> specification of 72% efficiency at 14 MHz is correct.? From that >>>>> number I can calculate the efficiency and gain on all the other >>>>> bands. >>>>> >>>>> If you don't want to download the document, here is a summary of >>>>> the results: >>>>> >>>>> Freq??? Eff??? Gain with respect to a half-wave dipole >>>>> MHz??? dB??? dBd >>>>> 7.0??? -7.3??? -7.7 >>>>> 10.1??? -3.5??? -3.9 >>>>> 14.0??? -1.4??? -1.8 >>>>> 18.068??? -0.6??? -1.0 >>>>> 21.0??? -0.4??? -0.8 >>>>> 24.89??? -0.2??? -0.6 >>>>> 28.0??? -0.15??? -0.5 >>>>> >>>>> I'd be interested in any comments people may have on the accuracy of >>>>> my assumptions and calculations in the document. >>>>> >>>>> Alan N1AL >>>>> ______________________________________________________________ >>>>> Elecraft mailing list >>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>>>> Help: http://mailman.qth.net/mmfaq.htm >>>>> Post: mailto:[email protected] >>>>> >>>>> This list hosted by: http://www.qsl.net >>>>> Please help support this email list: http://www.qsl.net/donate.html >>>>> Message delivered to [email protected] >>>> >>> >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[email protected] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to [email protected] >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ------------------------------ Message: 6 Date: Tue, 19 Jan 2021 16:35:55 -0500 From: Joseph Shuman <[email protected]> To: Elecraft Mail Server <[email protected]> Subject: [Elecraft] Absurd remarks about FCC and ARRL notices. Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8 This new OT topic and the preceding old OT topic combined has been one of the greatest examples of free speech I have ever seen on-line. Kudos to this forum for open and honest participation, it fills me with hope to see such a wonderful exchange of contrasting viewpoints without digital censorship. It may be ?OT? but the unprecedented notice by the FCC and the ARRL should be openly discussed by all licensees. After all, our hobby is an advancement of free speech that pre-dates the digital age, and in my view free speech is NEVER ?absurd.? Keeping Watch - shu Joe Shuman, NZ8P ------------------------------ Message: 7 Date: Tue, 19 Jan 2021 14:37:15 -0700 From: kennedyjp <[email protected]> To: Geoffrey Feldman <[email protected]>, [email protected], [email protected] Subject: Re: [Elecraft] Absurd remarks about FCC and ARRL notices. Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8 Enough already. Keep your political views and beliefs off this forum.? Not needed, not wanted.?JimW7OUU?Sent via the Samsung Galaxy S9+, an AT&T 5G Evolution capable smartphone -------- Original message --------From: Geoffrey Feldman <[email protected]> Date: 1/18/21 19:06 (GMT-07:00) To: [email protected], [email protected] Subject: [Elecraft] Absurd remarks about FCC and ARRL notices. The letters to this list regarding FCC and ARRL notices? were factuallyfalse and have absolutely nothing to do with Elecraft products exceptperhaps as some might choose to use such radio transmitting products tocommit unjustified criminal acts.? Those who have false pride in theircomments can read what I write here and readily determine their factualmistakes for themselves.? The reason for the FCC and ARRL Notices is factually not because of the nextadministration but the present one which incited a riot. IN THAT? CRIMINALOFFENSE, Radios were used unlawfully to commit Federal offenses againstdemocracy and the Constitution.?? I also see the FCC notice as one askingcivilians to report criminal use of Amateur and other civiliancommunications g ear - This I will do as well as working with other lawabiding hams to find, locate and document criminal use, especially againstthe Constitution and US Government.?? The reason why Washington D.C. is anarmed camp is that on 1/6 We had a president incite insurrection. ThatPresident is the only one with two impeachments, both of which are morelegally substantive than the two which preceded them.? Those personscriminally acted to disrupt lawful congressional preceding.? Many claim tohave done this on behalf of the current President, failing to understandnobody is above the law and any apparent direction to violate theconstitution is illegal no matter the source. That entire event wasunprecedented in the USA and the responses are and will be as well.? Theelection was not fraudulent.? It was certified in each of the states, inmost cases by Republican elected authorities.? Over 60 cases whose lawyersclaimed fraud, were thrown out by Federal judges, many of whom appointed bythe cur rent President.? In several cases these judges noted there was noevidence at all and in the rest, no evidence that would show a change in theend result for that state.? The Supreme Court also spoke on this matter -against the Presidents false claims.? There are over 60 case transcripts,public oral opinions by the judges and supreme court, as well as the remarksof AG Barr who quit in disgust with his own administration.Frankly to blame the next administration for the FCC and ARRL notice isidiotic - they are not in power yet.? That assault on the Capitol wasunprecedented and THAT is what has led to the other unprecedented things.The reason is that under our constitution, nobody is above the law,including the President and those who stormed the capitol.? Acting toenforce the law should not be offensive to anyone who claims to be a patriotor writing in the traditions of Amateur Radio or the ARRL.?? Interesting? toknow the false sympathies of some of you though. I encourage you t o spendthe reasonable efforts of citizens to go and learn what you didn't. Geoffrey FeldmanW1GCF______________________________________________________________Elecraft mailing listHome: http://mailman.qth.net/mailman/listinfo/elecraftHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:[email protected] list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.htmlMessage delivered to [email protected] ------------------------------ Message: 8 Date: Tue, 19 Jan 2021 21:47:59 +0000 From: Al London <[email protected]> To: Geoffrey Feldman <[email protected]>, "[email protected]" <[email protected]>, "[email protected]" <[email protected]>, kennedyjp <[email protected]> Subject: Re: [Elecraft] Absurd remarks about FCC and ARRL notices. Message-ID: <bn7pr05mb4257db73ebdfdf3cce4277f0a5...@bn7pr05mb4257.namprd05.prod.outlook.com> Content-Type: text/plain; charset="us-ascii" Jim Thank you for your concise comments. Greatly appreciated. The last thing we need is more politics. Al N4DIY Sent from my Verizon, Samsung Note20 smartphone ________________________________ From: [email protected] <[email protected]> on behalf of kennedyjp <[email protected]> Sent: Tuesday, January 19, 2021 4:37:15 PM To: Geoffrey Feldman <[email protected]>; [email protected] <[email protected]>; [email protected] <[email protected]> Subject: Re: [Elecraft] Absurd remarks about FCC and ARRL notices. Enough already. Keep your political views and beliefs off this forum. Not needed, not wanted. JimW7OUU Sent via the Samsung Galaxy S9+, an AT&T 5G Evolution capable smartphone -------- Original message --------From: Geoffrey Feldman <[email protected]> Date: 1/18/21 19:06 (GMT-07:00) To: [email protected], [email protected] Subject: [Elecraft] Absurd remarks about FCC and ARRL notices. The letters to this list regarding FCC and ARRL notices were factuallyfalse and have absolutely nothing to do with Elecraft products exceptperhaps as some might choose to use such radio transmitting products tocommit unjustified criminal acts. Those who have false pride in theircomments can read what I write here and readily determine their factualmistakes for themselves. The reason for the FCC and ARRL Notices is factually not because of the nextadministration but the present one which incited a riot. IN THAT CRIMINALOFFENSE, Radios were used unlawfully to commit Federal offenses againstdemocracy and the Constitution. I also see the FCC notice as one askingcivilians to report criminal use of Amateur and other civiliancommunications g ear - This I will do as well as working with other lawabiding hams to find, locate and document criminal use, especially againstthe Constitution and US Government. The reason why Washington D.C. is anarmed camp is that on 1/6 We had a president incite insurrection. ThatPresident is the only one with two impeachments, both of which are morelegally substantive than the two which preceded them. Those personscriminally acted to disrupt lawful congressional preceding. Many claim tohave done this on behalf of the current President, failing to understandnobody is above the law and any apparent direction to violate theconstitution is illegal no matter the source. That entire event wasunprecedented in the USA and the responses are and will be as well. Theelection was not fraudulent. It was certified in each of the states, inmost cases by Republican elected authorities. Over 60 cases whose lawyersclaimed fraud, were thrown out by Federal judges, many of whom appointed bythe cur rent President. In several cases these judges noted there was noevidence at all and in the rest, no evidence that would show a change in theend result for that state. The Supreme Court also spoke on this matter -against the Presidents false claims. There are over 60 case transcripts,public oral opinions by the judges and supreme court, as well as the remarksof AG Barr who quit in disgust with his own administration.Frankly to blame the next administration for the FCC and ARRL notice isidiotic - they are not in power yet. That assault on the Capitol wasunprecedented and THAT is what has led to the other unprecedented things.The reason is that under our constitution, nobody is above the law,including the President and those who stormed the capitol. Acting toenforce the law should not be offensive to anyone who claims to be a patriotor writing in the traditions of Amateur Radio or the ARRL. Interesting toknow the false sympathies of some of you though. I encourage you t o spendthe reasonable efforts of citizens to go and learn what you didn't. Geoffrey FeldmanW1GCF______________________________________________________________Elecraft mailing listHome: http://mailman.qth.net/mailman/listinfo/elecraftHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:[email protected] list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.htmlMessage delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ------------------------------ Message: 9 Date: Tue, 19 Jan 2021 14:00:23 -0800 From: Wayne Burdick <[email protected]> To: Elecraft Reflector <[email protected]> Subject: Re: [Elecraft] Absurd remarks about FCC and ARRL notices. Message-ID: <[email protected]> Content-Type: text/plain; charset=us-ascii My overworked business partner (WA6HHQ) is rightly trying to shut down this thread. We certainly don't want red and blue Elecraft forums. Before he does, I'd like to slip in a final comment. The intent of my posting (yes, I started this) was to call attention to a highly unusual FCC announcement that was assumed to be of general interest. Similar postings were made to many other ham forums in the same time frame. It's clear that the message has been received loud and clear. Interpretations are hereby officially left to the reader as a [private] exercise. Thanks, Wayne N6KR ------------------------------ Message: 10 Date: Tue, 19 Jan 2021 14:06:19 -0800 From: Paul GACEK <[email protected]> To: Elecraft Reflector <[email protected]> Subject: [Elecraft] Something different, old memories and using the KX3 Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8 I?ve been sorting out some of my LoTW records which inevitably covered the 2016 NPOTA event. I did a lot of low power phone activations in the Western USA using my KX3 for NPOTA many in the San Francisco Bay Area when I was living in that fine city. Loved the event, love my KX3 and just wanted to jot down a few memories for me to re-read over a glass of whisky sometime in the future and not surprisingly thinking about the past is almost as good as going out now which clearly isn?t so easy. No technical insights nor stellar Q counts here?..just old fashioned memories of a more human kind. Delete if not interested or peruse at https://nomadic.blog/2021/01/19/camaraderie-in-the-age-of-national-parks-on-the-air/ <https://nomadic.blog/2021/01/19/camaraderie-in-the-age-of-national-parks-on-the-air/> Paul W6PNG/M0SNA www.nomadic.blog<http://www.nomadic.blog> <http://www.nomadic.blog/> ------------------------------ Message: 11 Date: Tue, 19 Jan 2021 17:14:47 -0500 From: Dave Sublette <[email protected]> To: Paul GACEK <[email protected]> Cc: Elecraft Reflector <[email protected]> Subject: Re: [Elecraft] Something different, old memories and using the KX3 Message-ID: <cakynjknrzk352b_++hycx6xs3eh_31z60lp0uzi8lxfl+-0...@mail.gmail.com> Content-Type: text/plain; charset="UTF-8" Well done, Paul. It is a joy to read your account and I know you have had some great adventures. You are right about we older folks who cherish the memories of our adventures through the years. 73, Dave, K4TO On Tue, Jan 19, 2021 at 5:06 PM Paul GACEK via Elecraft < [email protected]> wrote: > I?ve been sorting out some of my LoTW records which inevitably covered the > 2016 NPOTA event. > > I did a lot of low power phone activations in the Western USA using my KX3 > for NPOTA many in the San Francisco Bay Area when I was living in that fine > city. > > Loved the event, love my KX3 and just wanted to jot down a few memories > for me to re-read over a glass of whisky sometime in the future and not > surprisingly thinking about the past is almost as good as going out now > which clearly isn?t so easy. > > No technical insights nor stellar Q counts here?..just old fashioned > memories of a more human kind. > > Delete if not interested or peruse at > https://nomadic.blog/2021/01/19/camaraderie-in-the-age-of-national-parks-on-the-air/ > < > https://nomadic.blog/2021/01/19/camaraderie-in-the-age-of-national-parks-on-the-air/ > > > > Paul > W6PNG/M0SNA > www.nomadic.blog<http://www.nomadic.blog> <http://www.nomadic.blog/> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ------------------------------ Message: 12 Date: Tue, 19 Jan 2021 17:54:58 -0500 From: <[email protected]> To: "'Wayne Burdick'" <[email protected]>, "'Elecraft Reflector'" <[email protected]> Subject: Re: [Elecraft] Absurd remarks about FCC and ARRL notices. Message-ID: <[email protected]> Content-Type: text/plain; charset="us-ascii" Thanks for posting this originally - I wouldn't have seen it otherwise. The problem with political discussions - especially in the world of 24/7 news coverage and op eds - we all show how uneducated we are on the topics and are willing to believe what we are told without doing the research. The rhetoric is all too often divisive. We can all agree on how fun and fulfilling ham radio is to each of us in its own special way - let's stick to that. Hank K4HYJ -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Wayne Burdick Sent: Tuesday, January 19, 2021 5:00 PM To: Elecraft Reflector <[email protected]> Subject: Re: [Elecraft] Absurd remarks about FCC and ARRL notices. My overworked business partner (WA6HHQ) is rightly trying to shut down this thread. We certainly don't want red and blue Elecraft forums. Before he does, I'd like to slip in a final comment. The intent of my posting (yes, I started this) was to call attention to a highly unusual FCC announcement that was assumed to be of general interest. Similar postings were made to many other ham forums in the same time frame. It's clear that the message has been received loud and clear. Interpretations are hereby officially left to the reader as a [private] exercise. Thanks, Wayne N6KR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ------------------------------ Message: 13 Date: Tue, 19 Jan 2021 15:56:16 -0700 From: Alan Bloom <[email protected]> To: Wayne Burdick <[email protected]> Cc: Elecraft Reflector <[email protected]> Subject: Re: [Elecraft] Efficiency of MFJ remotely-tuned loop antennas Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8; format=flowed I've been convinced that AEA's specification of 72% efficiency for the Isoloop at 14 MHz is too high, certainly too high for the MFJ antennas.? So I re-did the calculations using the 59% efficiency figure calculated below.? The new results can be downloaded here: https://www.dropbox.com/s/ve1v49b3gjvmt64/MFJ-1786-1788_2.pdf?dl=0 If you don't want to download the (1-page) document with the pretty graph, here's a synopsis of the results: Freq? ? ? Eff.???? Gain with respect to a 1/2-wavelength dipole MHz?? ?? dB????? dBd 7.0??? ? ?? -9.5??? -9.9 10.1?? ? ? -5.1??? -5.5 14.0?? ? ? -2.3??? -2.7 18.068 ? -1.1??? -1.5 21.0?????? -0.7??? -1.1 24.89???? -0.4??? -.8 28.0?????? -0.26? -0.65 My basic conclusions still stand.? With almost minus 10 dBd of gain on 7 MHz, the 40 meter coverage of the MFJ-1788 doesn't seem very useful.? That is confirmed by some of the reviews I have seen.? I think you'd get better results by just loading up the coax feedline as a random-wire antenna with a tuner. The 10 MHz performance is a little better.? Good enough to at least allow you to get on the 30 meter band. On the higher bands, the gain is within less than 3 dB of a full-sized dipole, which seems a useful trade-off for its small size and wide-band continuous coverage. Disclaimer:? Again, I have never seen one of these things so this is all based on theory and on the many reviews I have read.? Even if my figures are off a bit, at least this gives an idea of the relative performance on the various bands. Alan N1AL On 1/18/2021 5:38 PM, Alan Bloom wrote: > Well let's see... > > Radiation resistance of a small loop is 31,171 * (Area / wavelength^2)^2 > > For a loop with a 91cm diameter at 14 MHz, I believe that comes out to > 0.064 ohms. > > Assuming the loss is due to the RF resistance of the loop: > > From the internet I get the volume resistivity and skin depth for 6063 > aluminum is 0.03 microohms-meter and 23.3 micrometers respectively, so > the surface resistivity is 0.03/23.3 = 0.0013 ohms per square.? The > outside circumference of the tubing is PI * 1.05" = 3.3" and the loop > length is PI * 36" = 113" so the loss resistance is .0013 * 113/3.3 = > 0.045 ohms. > > So I calculate an efficiency of 0.064 / (0.064 + 0.045) = 59% > > So worse than AEA claimed, but in the ballpark. > > Alan N1AL > > > > > On 1/18/2021 3:39 PM, Wayne Burdick wrote: >> Hi Alan, >> >> 72% sounds a bit high. Is this number based on loop size alone ("in >> theory")? Or are they taking conductor geometry and other losses into >> account? >> >> Wayne >> N6KR >> >> >>> On Jan 18, 2021, at 2:05 PM, Alan Bloom <[email protected]> wrote: >>> >>> MFJ makes a pair of small, remotely-tuned loop antennas, the >>> MFJ-1786 that covers 10-30 MHz and the MFJ-1788 that covers 7 to 21+ >>> MHz.? As far as I can tell, the two antennas are identical except >>> for the size of the tuning capacitor.? Each consists of a 3 foot (91 >>> cm) diameter loop made of aluminum tubing and a plastic housing that >>> contains the tuning capacitor, motor, and coupling loop.? No control >>> cable is required since the control voltage is sent from the control >>> box in the shack to the motor in the antenna via the coaxial cable. >>> >>> Before I purchase one of these I wanted to get an idea of the >>> efficiency of such a small loop.? MFJ is silent on the subject so I >>> did my own calculations.? The calculations and results are on a >>> 1-page document that I uploaded to Dropbox and can be downloaded here: >>> >>> https://www.dropbox.com/s/l8mv67cjrck2ssn/MFJ-1786-1788.pdf?dl=0 >>> >>> My calculations are based on the assumption that the efficiency of >>> the MFJ antennas is similar to the (no longer manufactured) AEA >>> Isoloop (my reasoning for that is in the document) and that AEA's >>> specification of 72% efficiency at 14 MHz is correct.? From that >>> number I can calculate the efficiency and gain on all the other bands. >>> >>> If you don't want to download the document, here is a summary of the >>> results: >>> >>> Freq????? Eff????? Gain with respect to a half-wave dipole >>> MHz????? dB????? dBd >>> 7.0??????? -7.3??? -7.7 >>> 10.1? ? ? -3.5??? -3.9 >>> 14.0?? ?? -1.4??? -1.8 >>> 18.068? -0.6??? -1.0 >>> 21.0?? ?? -0.4??? -0.8 >>> 24.89??? -0.2??? -0.6 >>> 28.0????? -0.15? -0.5 >>> >>> I'd be interested in any comments people may have on the accuracy of >>> my assumptions and calculations in the document. >>> >>> Alan N1AL ------------------------------ Message: 14 Date: Tue, 19 Jan 2021 23:37:59 +0000 (UTC) From: Louandzip <[email protected]> Cc: Elecraft Reflector <[email protected]> Subject: Re: [Elecraft] Efficiency of MFJ remotely-tuned loop antennas Message-ID: <[email protected]> Content-Type: text/plain; charset=UTF-8 Certainly don't want to throw away power in wasted heat, but when I turn down my 200W rig to 5W for QRP, it's still useful and that's 16 dB down. With ant restrictions, I'm looking at building a small horizontal loop for 6m.? It'd be a little more than 4' in circumference, 16" dia,? and the capacitor could be be two 4 cm diameter plates ~2mm apart. That should be reasonably easy to make relatively efficent as there are not a lot of plates that need to be connected with very low resistance.? I calculate ~85% with 1/2" copper.? Should be good for 200W.? I'd orient it horizontally for horizontal polarization (weak sigs) and local noise rejection. I have a squalo made from a lawn chair, but technically that's not a small loop and a little big to be stealth. On Tuesday, January 19, 2021, 3:58:09 PM MST, Alan Bloom <[email protected]> wrote: I've been convinced that AEA's specification of 72% efficiency for the Isoloop at 14 MHz is too high, certainly too high for the MFJ antennas.? So I re-did the calculations using the 59% efficiency figure calculated below.? The new results can be downloaded here: https://www.dropbox.com/s/ve1v49b3gjvmt64/MFJ-1786-1788_2.pdf?dl=0 If you don't want to download the (1-page) document with the pretty graph, here's a synopsis of the results: Freq? ? ? Eff.???? Gain with respect to a 1/2-wavelength dipole MHz?? ?? dB????? dBd 7.0??? ? ?? -9.5??? -9.9 10.1?? ? ? -5.1??? -5.5 14.0?? ? ? -2.3??? -2.7 18.068 ? -1.1??? -1.5 21.0?????? -0.7??? -1.1 24.89???? -0.4??? -.8 28.0?????? -0.26? -0.65 My basic conclusions still stand.? With almost minus 10 dBd of gain on 7 MHz, the 40 meter coverage of the MFJ-1788 doesn't seem very useful.? That is confirmed by some of the reviews I have seen.? I think you'd get better results by just loading up the coax feedline as a random-wire antenna with a tuner. The 10 MHz performance is a little better.? Good enough to at least allow you to get on the 30 meter band. On the higher bands, the gain is within less than 3 dB of a full-sized dipole, which seems a useful trade-off for its small size and wide-band continuous coverage. Disclaimer:? Again, I have never seen one of these things so this is all based on theory and on the many reviews I have read.? Even if my figures are off a bit, at least this gives an idea of the relative performance on the various bands. Alan N1AL On 1/18/2021 5:38 PM, Alan Bloom wrote: > Well let's see... > > Radiation resistance of a small loop is 31,171 * (Area / wavelength^2)^2 > > For a loop with a 91cm diameter at 14 MHz, I believe that comes out to > 0.064 ohms. > > Assuming the loss is due to the RF resistance of the loop: > > From the internet I get the volume resistivity and skin depth for 6063 > aluminum is 0.03 microohms-meter and 23.3 micrometers respectively, so > the surface resistivity is 0.03/23.3 = 0.0013 ohms per square.? The > outside circumference of the tubing is PI * 1.05" = 3.3" and the loop > length is PI * 36" = 113" so the loss resistance is .0013 * 113/3.3 = > 0.045 ohms. > > So I calculate an efficiency of 0.064 / (0.064 + 0.045) = 59% > > So worse than AEA claimed, but in the ballpark. > > Alan N1AL > > > > > On 1/18/2021 3:39 PM, Wayne Burdick wrote: >> Hi Alan, >> >> 72% sounds a bit high. Is this number based on loop size alone ("in >> theory")? Or are they taking conductor geometry and other losses into >> account? >> >> Wayne >> N6KR >> >> >>> On Jan 18, 2021, at 2:05 PM, Alan Bloom <[email protected]> wrote: >>> >>> MFJ makes a pair of small, remotely-tuned loop antennas, the >>> MFJ-1786 that covers 10-30 MHz and the MFJ-1788 that covers 7 to 21+ >>> MHz.? As far as I can tell, the two antennas are identical except >>> for the size of the tuning capacitor.? Each consists of a 3 foot (91 >>> cm) diameter loop made of aluminum tubing and a plastic housing that >>> contains the tuning capacitor, motor, and coupling loop.? No control >>> cable is required since the control voltage is sent from the control >>> box in the shack to the motor in the antenna via the coaxial cable. >>> >>> Before I purchase one of these I wanted to get an idea of the >>> efficiency of such a small loop.? MFJ is silent on the subject so I >>> did my own calculations.? The calculations and results are on a >>> 1-page document that I uploaded to Dropbox and can be downloaded here: >>> >>> https://www.dropbox.com/s/l8mv67cjrck2ssn/MFJ-1786-1788.pdf?dl=0 >>> >>> My calculations are based on the assumption that the efficiency of >>> the MFJ antennas is similar to the (no longer manufactured) AEA >>> Isoloop (my reasoning for that is in the document) and that AEA's >>> specification of 72% efficiency at 14 MHz is correct.? From that >>> number I can calculate the efficiency and gain on all the other bands. >>> >>> If you don't want to download the document, here is a summary of the >>> results: >>> >>> Freq????? Eff????? Gain with respect to a half-wave dipole >>> MHz????? dB????? dBd >>> 7.0??????? -7.3??? -7.7 >>> 10.1? ? ? -3.5??? -3.9 >>> 14.0?? ?? -1.4??? -1.8 >>> 18.068? -0.6??? -1.0 >>> 21.0?? ?? -0.4??? -0.8 >>> 24.89??? -0.2??? -0.6 >>> 28.0????? -0.15? -0.5 >>> >>> I'd be interested in any comments people may have on the accuracy of >>> my assumptions and calculations in the document. >>> >>> Alan N1AL ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ------------------------------ Message: 15 Date: Tue, 19 Jan 2021 16:48:35 -0700 (MST) From: Barry <[email protected]> To: [email protected] Subject: Re: [Elecraft] Absurd remarks about FCC and ARRL notices. Message-ID: <[email protected]> Content-Type: text/plain; charset=UTF-8 There's no place for anonymous posting, either. How hard is it to include your name and/or call? Barry W2UP Elecraft mailing list wrote > Listen. > This is no place for political BS. I don?t care if you are right, left, or > in the f?ing middle. This is a place to discuss Elecraft equipment, uses, > procedures, and other at least semi- related information. NOT POLITICS. > There are plenty of sites out there on the never ending internet where you > can put down this or the next president and administration. > > Sent from my iPhone -- Sent from: http://elecraft.365791.n2.nabble.com/ ------------------------------ Message: 16 Date: Tue, 19 Jan 2021 15:54:39 -0800 From: Eric Garner <[email protected]> To: Elecraft Reflector <[email protected]> Subject: Re: [Elecraft] Efficiency of MFJ remotely-tuned loop antennas Message-ID: <CABqdsz96VjYEXO9c8v=9rh_ejeguvkwoqd1rlcj6fljetyk...@mail.gmail.com> Content-Type: text/plain; charset="UTF-8" Here's an interior shot of the tuning capacitor https://imgur.com/a/sYdvgzF -Eric KI7LTT On Mon, Jan 18, 2021 at 10:59 PM Alan Bloom <[email protected]> wrote: > > That doesn't sound like they are welded, and given the cost > difference for welded air variables I doubt MFJ used them. > > As I said, I don't have one so I can't say for sure. I got my > information from the MFJ web site: "All welded construction, no > mechanical joints, welded butterfly capacitor with no rotating contacts > ... Each plate in MFJ's tuning capacitor is welded for low loss and > polished to prevent high voltage arcing, welded to the radiator ...". > https://mfjenterprises.com/products/mfj-1786 > > Also, for what it's worth, some of the reviews on eham.com and qrz.com > mention that it has a welded tuning capacitor. > > I got the impression that one reason people often receive units with > bent capacitor plates is that they got bent in the welding process. > > It would be interesting to look at one and see what they actually mean > by "welded". > > Alan N1AL > > > > On 1/18/2021 10:10 PM, David Gilbert wrote: > > > > According to another ham who recently posted here, he had to "tighten" > > the plates on the MFJ capacitor to get it to work properly. That > > doesn't sound like they are welded, and given the cost difference for > > welded air variables I doubt MFJ used them. > > > > I sincerely doubt that an actual practical small loop is only down 3 > > dB from a full size antenna. That makes no sense to me at all. If > > that were the case everyone would be using one, because they are not > > that difficult to make ... at least for manually tuned ones. > > > > But you seem determined to believe differently, and it's not my place > > to convince you otherwise. You asked for inputs and I have made > > mine. Hopefully you are right and I am wrong. > > > > 73, > > Dave AB7E > > > > > > > > On 1/18/2021 9:54 PM, Alan Bloom wrote: > >> > There is a reason why top quality variable capacitors often use > >> welded plates. > >> > >> I believe they do weld the capacitor plates and also weld the loop to > >> the capacitor. (I don't have one, but that's what I've read.) > >> > >> > Yours is a limited theoretical analysis ... not a practical one. > >> > >> A number of reviews I have read (including the QST review of August > >> 1994) have reported comparable performance to full-sized wire > >> antennas located on the same site. If the loop is down by, say, 3 > >> dB, that's only half an S unit, which would hardly be noticeable in > >> the QSB of a typical amateur band. > >> > >> > >> As I see it, the advantages of the MFJ-1786 10-30 MHz loop are: > >> > >> - Continuous coverage on 6 amateur bands. A convenient way to cover > >> all the WARC bands. > >> - Small and light. > >> - Omni-directional (when mounted horizontally) so does not need a > >> rotor. > >> - No control cable required - control voltage is fed through the coax. > >> - Narrow bandwidth provides excellent RF selectivity. Might be good > >> on Field Day to reduce inter-station QRM. > >> - Users have reported lower receiver noise compared to wire > >> antennas. No doubt that is because the isolated pickup loop prevents > >> feedline radiation/pickup. > >> > >> And the disadvantages: > >> > >> - Expensive ($500 list price) > >> - Less gain than a simple dipole (although you would theoretically > >> need 6 of them). > >> - Fiddly to tune. If you QSY too far you have to re-tune. > >> - MFJ quality control leaves something to be desired. (You may have > >> to open it up when you get it and make minor repairs.) > >> - You have to pay attention to the problem of entry of water and/or > >> bugs into the housing. > >> - The controller can be damaged by a DC short in the coax e.g. from > >> an shorting-type antenna switch. (I don't understand why MFJ didn't > >> include a fuse or some other way to protect the controller.) > >> > >> I probably wouldn't buy the 7-21 MHz MFJ-1788 because of the poor > >> efficiency at 7 MHz. I think you'd have a better signal just using > >> the coax as a random end-fed wire (with a tuner). > >> > >> Alan N1AL > >> > >> > >> On 1/18/2021 8:17 PM, David Gilbert wrote: > >>> > >>> You are neglecting the losses in various connections in the system > >>> ... including possibly the construction of the capacitor itself. I > >>> don't believe that they are insignificant. There is a reason why > >>> top quality variable capacitors often use welded plates. > >>> > >>> I would also guess that contact resistance is worse for dissimilar > >>> materials, such as a copper wire to an aluminum tube. > >>> > >>> Yours is a limited theoretical analysis ... not a practical one. > >>> > >>> Dave AB7E > >>> > >>> > >>> > >>> On 1/18/2021 5:38 PM, Alan Bloom wrote: > >>>> Well let's see... > >>>> > >>>> Radiation resistance of a small loop is 31,171 * (Area / > >>>> wavelength^2)^2 > >>>> > >>>> For a loop with a 91cm diameter at 14 MHz, I believe that comes out > >>>> to 0.064 ohms. > >>>> > >>>> Assuming the loss is due to the RF resistance of the loop: > >>>> > >>>> From the internet I get the volume resistivity and skin depth for > >>>> 6063 aluminum is 0.03 microohms-meter and 23.3 micrometers > >>>> respectively, so the surface resistivity is 0.03/23.3 = 0.0013 ohms > >>>> per square. The outside circumference of the tubing is PI * 1.05" > >>>> = 3.3" and the loop length is PI * 36" = 113" so the loss > >>>> resistance is .0013 * 113/3.3 = 0.045 ohms. > >>>> > >>>> So I calculate an efficiency of 0.064 / (0.064 + 0.045) = 59% > >>>> > >>>> So worse than AEA claimed, but in the ballpark. > >>>> > >>>> Alan N1AL > >>>> > >>>> > >>>> > >>>> > >>>> On 1/18/2021 3:39 PM, Wayne Burdick wrote: > >>>>> Hi Alan, > >>>>> > >>>>> 72% sounds a bit high. Is this number based on loop size alone > >>>>> ("in theory")? Or are they taking conductor geometry and other > >>>>> losses into account? > >>>>> > >>>>> Wayne > >>>>> N6KR > >>>>> > >>>>> > >>>>>> On Jan 18, 2021, at 2:05 PM, Alan Bloom <[email protected]> wrote: > >>>>>> > >>>>>> MFJ makes a pair of small, remotely-tuned loop antennas, the > >>>>>> MFJ-1786 that covers 10-30 MHz and the MFJ-1788 that covers 7 to > >>>>>> 21+ MHz. As far as I can tell, the two antennas are identical > >>>>>> except for the size of the tuning capacitor. Each consists of a > >>>>>> 3 foot (91 cm) diameter loop made of aluminum tubing and a > >>>>>> plastic housing that contains the tuning capacitor, motor, and > >>>>>> coupling loop. No control cable is required since the control > >>>>>> voltage is sent from the control box in the shack to the motor in > >>>>>> the antenna via the coaxial cable. > >>>>>> > >>>>>> Before I purchase one of these I wanted to get an idea of the > >>>>>> efficiency of such a small loop. MFJ is silent on the subject so > >>>>>> I did my own calculations. The calculations and results are on a > >>>>>> 1-page document that I uploaded to Dropbox and can be downloaded > >>>>>> here: > >>>>>> > >>>>>> https://www.dropbox.com/s/l8mv67cjrck2ssn/MFJ-1786-1788.pdf?dl=0 > >>>>>> > >>>>>> My calculations are based on the assumption that the efficiency > >>>>>> of the MFJ antennas is similar to the (no longer manufactured) > >>>>>> AEA Isoloop (my reasoning for that is in the document) and that > >>>>>> AEA's specification of 72% efficiency at 14 MHz is correct. From > >>>>>> that number I can calculate the efficiency and gain on all the > >>>>>> other bands. > >>>>>> > >>>>>> If you don't want to download the document, here is a summary of > >>>>>> the results: > >>>>>> > >>>>>> Freq Eff Gain with respect to a half-wave dipole > >>>>>> MHz dB dBd > >>>>>> 7.0 -7.3 -7.7 > >>>>>> 10.1 -3.5 -3.9 > >>>>>> 14.0 -1.4 -1.8 > >>>>>> 18.068 -0.6 -1.0 > >>>>>> 21.0 -0.4 -0.8 > >>>>>> 24.89 -0.2 -0.6 > >>>>>> 28.0 -0.15 -0.5 > >>>>>> > >>>>>> I'd be interested in any comments people may have on the accuracy of > >>>>>> my assumptions and calculations in the document. > >>>>>> > >>>>>> Alan N1AL > >>>>>> ______________________________________________________________ > >>>>>> Elecraft mailing list > >>>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft > >>>>>> Help: http://mailman.qth.net/mmfaq.htm > >>>>>> Post: mailto:[email protected] > >>>>>> > >>>>>> This list hosted by: http://www.qsl.net > >>>>>> Please help support this email list: http://www.qsl.net/donate.html > >>>>>> Message delivered to [email protected] > >>>>> > >>>> > >>>> ______________________________________________________________ > >>>> Elecraft mailing list > >>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft > >>>> Help: http://mailman.qth.net/mmfaq.htm > >>>> Post: mailto:[email protected] > >>>> > >>>> This list hosted by: http://www.qsl.net > >>>> Please help support this email list: http://www.qsl.net/donate.html > >>>> Message delivered to [email protected] > >>> > >>> ______________________________________________________________ > >>> Elecraft mailing list > >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft > >>> Help: http://mailman.qth.net/mmfaq.htm > >>> Post: mailto:[email protected] > >>> > >>> This list hosted by: http://www.qsl.net > >>> Please help support this email list: http://www.qsl.net/donate.html > >>> Message delivered to [email protected] > >> > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] -- --Eric _________________________________________ Eric Garner ------------------------------ _______________________________________________ Elecraft mailing list Post to: [email protected] http://mailman.qth.net/mailman/listinfo/elecraft You must be a subscriber to post. Elecraft web page: http://www.elecraft.com End of Elecraft Digest, Vol 201, Issue 26 ***************************************** ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
