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As the original poster under this heading I figured you might be interested
to know what I have achieved so far, even though I am not yet ready to send the white smoke up the chimney. Briefly, my problem was that my KAT500 would go into uncommanded tunes during a QSO, usually on digital modes.The practical result was that I had to restrict TX power to less than 40Watts on most bands to avoid a burst from the Chicago Piano in the KAT. I had assumed an antenna/feeder problem and had changed every last connector, wire, balun and insulator in my system before asking for help from the Reflector Brains Trust. All of the other people who subsequently reported a similar problem made me feel a little better, and I also received a lot of diagnoses and practical advice which I have followed or will follow soon. One of the simplest was from Ron WB4OOA: Carry out a K3 Gain Calibration via the K3 Utility (I had to download the latest Utility version to make this work properly) then Install the KAT500 V1.42 Beta (Not quite as easy as it sounds). After this things were better, and my power setting on the K3 always appeared on the KPA500 wattmeter. I could now operate at higher power on some bands but had to stay below 40W on 40m. I had also adjusted the per band retune trigger SWRs upwards via the KAT500 Utility which also helped a little. I remain convinced though, that the basic trigger problem lies with the antenna system (an OCF multiband dipole) and I am continuing to work on this aspect using my analyser. Why it should have suddenly kicked off after many months of solid performance, and why changing everything hasn't yet cured it remains a mystery. My next steps are to try a choke balun on the feeder (parts now to hand) and to prune the antenna to get a better resonance on the bands of interest. Now if only this darn rain would stop! (I still think some tweaking of the KAT500 software might also help!) Ray Coles, C.Eng. M0XDL 10 Littlemoor Road, Weymouth DT3 6AA Tel: +44 (0) 1305 833699 Mob: 07831 516517 ______________________________________________________________ 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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Hi Ray.
The OCF antennas are know to cause RF in the shack, and RF in the shack quite often result in strange behaviour from the radio equipment. A choke balun may work, but a current balun with ferrite is far better. Try to install 10-12 ferrites snap-ons on you're feedline as close to the feed point as possible, and try not to run the feedline parallel to the antenna wires. Another alterntive may be to install a socalled line isolator like the MFJ-915 close to the feedpoint. http://www.mfjenterprises.com/Product.php?productid=MFJ-915 The line isolator is a 1:1 current balun with ferrite, so it esential the same as the ferrite snap-ons in my first suggestion. Best regards, Martin Storli LA8OKA Oslo, Norway ARCTICPEAK's Radio pages! http://www.arcticpeak.com/radio.htm ________________________________ Fra: Ray Coles <[hidden email]> Til: [hidden email] Sendt: Onsdag, 8. januar 2014 11.57 Emne: [Elecraft] K3/KPA500/KAT500 SWR problem UPDATE As the original poster under this heading I figured you might be interested to know what I have achieved so far, even though I am not yet ready to send the white smoke up the chimney. Briefly, my problem was that my KAT500 would go into uncommanded tunes during a QSO, usually on digital modes.The practical result was that I had to restrict TX power to less than 40Watts on most bands to avoid a burst from the Chicago Piano in the KAT. I had assumed an antenna/feeder problem and had changed every last connector, wire, balun and insulator in my system before asking for help from the Reflector Brains Trust. All of the other people who subsequently reported a similar problem made me feel a little better, and I also received a lot of diagnoses and practical advice which I have followed or will follow soon. One of the simplest was from Ron WB4OOA: Carry out a K3 Gain Calibration via the K3 Utility (I had to download the latest Utility version to make this work properly) then Install the KAT500 V1.42 Beta (Not quite as easy as it sounds). After this things were better, and my power setting on the K3 always appeared on the KPA500 wattmeter. I could now operate at higher power on some bands but had to stay below 40W on 40m. I had also adjusted the per band retune trigger SWRs upwards via the KAT500 Utility which also helped a little. I remain convinced though, that the basic trigger problem lies with the antenna system (an OCF multiband dipole) and I am continuing to work on this aspect using my analyser. Why it should have suddenly kicked off after many months of solid performance, and why changing everything hasn't yet cured it remains a mystery. My next steps are to try a choke balun on the feeder (parts now to hand) and to prune the antenna to get a better resonance on the bands of interest. Now if only this darn rain would stop! (I still think some tweaking of the KAT500 software might also help!) Ray Coles, C.Eng. M0XDL 10 Littlemoor Road, Weymouth DT3 6AA Tel: +44 (0) 1305 833699 Mob: 07831 516517 ______________________________________________________________ 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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In reply to this post by Ray Coles
Ray,
Very interesting stuff, thanks. As the user of an off-center fed doublet myself, I was initially very nervous of running more than my usual 100W. As it happened, I need not have worried, as I have never experienced the problems you describe with the arrival of the KPA/KAT500. The reason may well be the choking I use on the doublet, and I suspect that you are on the right track here. I took a belt and braces approach to this a year or so ago. I have a drop of about 20 feet of 300 ohm 'balanced' feeder whereupon a conversion to heavy duty coax is made via a choke balun based upon GM3SEK's work - using the recommended ferrites, combining three different chokes in series to cover the whole of the HF range. It's very heavy and physically quite large so I have it mounted in a box on a flat roof about 20 feet above the operating position. The coax (short run) goes down to the shack and through another 3 section choke balun on the back of the amplifier. GM3SEK's article is well worth a careful read. Miscellaneous bits of ferrite are likely to do nothing, and the combination of coaxial coils and ferrite in Ian's design works extremely well in my experience. An added bonus was that it also reduced my local noise floor considerably. http://www.ifwtech.co.uk/g3sek/in-prac/index.htm#1005 ...is all you need. In the UK you can get the ferrites from Farnell in a couple of days although they are quite expensive. Accept no imitations! 73 Stephen G4SJP On 8 January 2014 10:57, Ray Coles <[hidden email]> wrote: > As the original poster under this heading I figured you might be interested > to know what I have achieved so far, even though I am not yet ready to send > the white smoke up the chimney. Briefly, my problem was that my KAT500 > would go into uncommanded tunes during a QSO, usually on digital modes.The > practical result was that I had to restrict TX power to less than 40Watts > on > most bands to avoid a burst from the Chicago Piano in the KAT. I had > assumed > an antenna/feeder problem and had changed every last connector, wire, balun > and insulator in my system before asking for help from the Reflector Brains > Trust. All of the other people who subsequently reported a similar problem > made me feel a little better, and I also received a lot of diagnoses and > practical advice which I have followed or will follow soon. One of the > simplest was from Ron WB4OOA: Carry out a K3 Gain Calibration via the K3 > Utility (I had to download the latest Utility version to make this work > properly) then Install the KAT500 V1.42 Beta (Not quite as easy as it > sounds). After this things were better, and my power setting on the K3 > always appeared on the KPA500 wattmeter. I could now operate at higher > power > on some bands but had to stay below 40W on 40m. I had also adjusted the per > band retune trigger SWRs upwards via the KAT500 Utility which also helped a > little. > > I remain convinced though, that the basic trigger problem lies with the > antenna system (an OCF multiband dipole) and I am continuing to work on > this > aspect using my analyser. Why it should have suddenly kicked off after many > months of solid performance, and why changing everything hasn't yet cured > it > remains a mystery. My next steps are to try a choke balun on the feeder > (parts now to hand) and to prune the antenna to get a better resonance on > the bands of interest. Now if only this darn rain would stop! (I still > think > some tweaking of the KAT500 software might also help!) > > > > Ray Coles, C.Eng. M0XDL > > 10 Littlemoor Road, > > Weymouth DT3 6AA > > Tel: +44 (0) 1305 833699 > > Mob: 07831 516517 > > > > > > > > ______________________________________________________________ > 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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In reply to this post by Ray Coles
I don't believe it is an antenna or stray RF problem.
I have "memorized" tuner settings for the entire 75 meter band at 20 kc steps. The K-Line is set up per instructions (although the manual supplied by Elecraft is a little thin). When I QSY, the KAT500 will click to a memory when I transmit (either by using TUNE on the K3 or PTT and start talking). That is what I expect. What happens next is not expected! While in QSO, the KAT500 will suddenly retune. Normally, this retune will be a click or two (seeking a known memory) and a light show on the KPA500 - followed by the tuner settling down and the QSO continues. This is random and quite disconcerting - sometimes happening several times during a single QSO. A great amount of effort has been expended in checking and rechecking the entire antenna system. I am using a normal dipole for 75 meters with proper feedlines/connectors. There were no problems noted (not that I expected any). When using the same antenna system on other rigs - there have been NO similar incidents to what the KAT500 does. Once the tuning or tune memory is selected - there is no further tuner activity during a QSO. As it should be. Having learned how to do a trace report of the KAT500's tuning activity, I am able to see what the tuner is doing when this happens. In simple terms, it gets lost mid-QSO and the tuner activity noted is an attempt to retune to the frequency it is sensing that frequency will not be what your VFO is showing. When it settles back down, it will once again be tuned to your current XMIT frequency. For some reason, the KAT500 senses an incorrect XMIT frequency during the QSO. I have been informed that a solution is being worked on by Elecraft. Bill W2BLC K-Line(?) ______________________________________________________________ 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 Stephen G4SJP
If I may, I would like to weigh jn here wjth what I have been using.
I put up an OCF of 137ft approximately (memory issue) with the feed point up about 37ft. I am set at 80/20 offset and I am using the dual core balun from Balun Designs (usual denials...yada yada yada) and I have very few issues with rf feedback and the k-line has behaved well. There are issues with interferance from time to time on the portable TV inside the motorhome so recently I added some snap on ferrite beads where I thought they wouod work and this seems to have largely cleaned the station up. When connecting to ann80m dipole, all the rf issues disappear. The OCF seems to work better on all bands over the 80m dipole although this is not a scientific way to do this, however, the OCF is definately quieter on all bands and I am happy with it. 73 Gary On 08/01/2014 10:31 PM, "Stephen Prior" <[hidden email]> wrote: > Ray, > > Very interesting stuff, thanks. As the user of an off-center fed doublet > myself, I was initially very nervous of running more than my usual 100W. > As it happened, I need not have worried, as I have never experienced the > problems you describe with the arrival of the KPA/KAT500. The reason may > well be the choking I use on the doublet, and I suspect that you are on the > right track here. I took a belt and braces approach to this a year or so > ago. I have a drop of about 20 feet of 300 ohm 'balanced' feeder whereupon > a conversion to heavy duty coax is made via a choke balun based upon > GM3SEK's work - using the recommended ferrites, combining three different > chokes in series to cover the whole of the HF range. It's very heavy and > physically quite large so I have it mounted in a box on a flat roof about > 20 feet above the operating position. The coax (short run) goes down to > the shack and through another 3 section choke balun on the back of the > amplifier. > > GM3SEK's article is well worth a careful read. Miscellaneous bits of > ferrite are likely to do nothing, and the combination of coaxial coils and > ferrite in Ian's design works extremely well in my experience. An added > bonus was that it also reduced my local noise floor considerably. > > http://www.ifwtech.co.uk/g3sek/in-prac/index.htm#1005 > > ...is all you need. In the UK you can get the ferrites from Farnell in a > couple of days although they are quite expensive. Accept no imitations! > > 73 Stephen G4SJP > > > > > On 8 January 2014 10:57, Ray Coles <[hidden email]> wrote: > > > As the original poster under this heading I figured you might be > interested > > to know what I have achieved so far, even though I am not yet ready to > send > > the white smoke up the chimney. Briefly, my problem was that my KAT500 > > would go into uncommanded tunes during a QSO, usually on digital > modes.The > > practical result was that I had to restrict TX power to less than 40Watts > > on > > most bands to avoid a burst from the Chicago Piano in the KAT. I had > > assumed > > an antenna/feeder problem and had changed every last connector, wire, > balun > > and insulator in my system before asking for help from the Reflector > Brains > > Trust. All of the other people who subsequently reported a similar > problem > > made me feel a little better, and I also received a lot of diagnoses and > > practical advice which I have followed or will follow soon. One of the > > simplest was from Ron WB4OOA: Carry out a K3 Gain Calibration via the K3 > > Utility (I had to download the latest Utility version to make this work > > properly) then Install the KAT500 V1.42 Beta (Not quite as easy as it > > sounds). After this things were better, and my power setting on the K3 > > always appeared on the KPA500 wattmeter. I could now operate at higher > > power > > on some bands but had to stay below 40W on 40m. I had also adjusted the > per > > band retune trigger SWRs upwards via the KAT500 Utility which also > helped a > > little. > > > > I remain convinced though, that the basic trigger problem lies with the > > antenna system (an OCF multiband dipole) and I am continuing to work on > > this > > aspect using my analyser. Why it should have suddenly kicked off after > many > > months of solid performance, and why changing everything hasn't yet cured > > it > > remains a mystery. My next steps are to try a choke balun on the feeder > > (parts now to hand) and to prune the antenna to get a better resonance on > > the bands of interest. Now if only this darn rain would stop! (I still > > think > > some tweaking of the KAT500 software might also help!) > > > > > > > > Ray Coles, C.Eng. M0XDL > > > > 10 Littlemoor Road, > > > > Weymouth DT3 6AA > > > > Tel: +44 (0) 1305 833699 > > > > Mob: 07831 516517 > > > > > > > > > > > > > > > > ______________________________________________________________ > > 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 > 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 LA8OKA
On 1/8/2014 3:24 AM, Martin Storli - LA8OKA wrote:
> The OCF antennas are know to cause RF in the shack, and RF in the shack quite often result in strange behaviour from the radio equipment. Correct. Because they are badly unbalanced, they also pick up lots of RX noise. > A choke balun may work, but a current balun with ferrite is far better. A ferrite choke is far more effective at solving both the noise and the RF in the shack. BUT off-center fed antennas, because they are badly unbalanced, establish very high common mode voltages across the choke. As a result, there is a high mortality rate with chokes on off-center-fed antennas. In other words, a ferrite choke on an OCF antenna is quite likely to fry with power. OCF antennas are an old idea whose time has passed. They should be avoided, unless, of course, you happen to live in an alternate universe where RX noise and RF in the shack are not a problem. :) 73, Jim K9YC ______________________________________________________________ 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 Ray Coles
An OCF is an unbalanced antenna and it must have a choke to keep RF off
the feed line into the shack. I use about ten turns of coax on a 4 inch PVC pipe right outside the wall where the feed comes into the house. It might be more or less, I am not at home to look. You can research it. Other choke baluns would help, if they present a high enough impedance. That seems to have cured RFI problems for me but I have occasionally felt like I needed more isolation. Many people have advised me to get rid of the OCF and go with something balanced but it suits my multi-band needs for now. I am pretty sure RF on the feed line would cause the tuning circuits in the KAT to act crazy. I'll leave that one for the Elecraft gurus to answer. Buck k4ia On 1/8/2014 5:57 AM, Ray Coles wrote: > As the original poster under this heading I figured you might be interested > to know what I have achieved so far, even though I am not yet ready to send > the white smoke up the chimney. Briefly, my problem was that my KAT500 > would go into uncommanded tunes during a QSO, usually on digital modes.The > practical result was that I had to restrict TX power to less than 40Watts on > most bands to avoid a burst from the Chicago Piano in the KAT. I had assumed > an antenna/feeder problem and had changed every last connector, wire, balun > and insulator in my system before asking for help from the Reflector Brains > Trust. All of the other people who subsequently reported a similar problem > made me feel a little better, and I also received a lot of diagnoses and > practical advice which I have followed or will follow soon. One of the > simplest was from Ron WB4OOA: Carry out a K3 Gain Calibration via the K3 > Utility (I had to download the latest Utility version to make this work > properly) then Install the KAT500 V1.42 Beta (Not quite as easy as it > sounds). After this things were better, and my power setting on the K3 > always appeared on the KPA500 wattmeter. I could now operate at higher power > on some bands but had to stay below 40W on 40m. I had also adjusted the per > band retune trigger SWRs upwards via the KAT500 Utility which also helped a > little. > > I remain convinced though, that the basic trigger problem lies with the > antenna system (an OCF multiband dipole) and I am continuing to work on this > aspect using my analyser. Why it should have suddenly kicked off after many > months of solid performance, and why changing everything hasn't yet cured it > remains a mystery. My next steps are to try a choke balun on the feeder > (parts now to hand) and to prune the antenna to get a better resonance on > the bands of interest. Now if only this darn rain would stop! (I still think > some tweaking of the KAT500 software might also help!) > > > > Ray Coles, C.Eng. M0XDL > > 10 Littlemoor Road, > > Weymouth DT3 6AA > > Tel: +44 (0) 1305 833699 > > Mob: 07831 516517 > > > > > > > > ______________________________________________________________ > 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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I have used OCF antennas in the past and currently have on up that is
fed with 600 ohm line and a balun for the coax transition to come in the house. It is a fine all band - 160-10 - antenna causing no RF problems in my shack. Although I rarely use this antenna, I hooked it up today and find the KAT500 misbehaves with this antenna the same as it does with a proper dipole. No joy! The OCF does, however, work well with my other auto-tune rigs. No hiccups noted. Bill W2BLC K-Line(?) ______________________________________________________________ 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 Buck - k4ia
If you are working the bands 30m and below and have the room you can
use inverted V antennas that all have the same feed point. The power will be distributed to the the antenna that is resonent at the transmit frequency. Until I was able to get room and funds for rotable antennas and longer wire antennas I used inverted V antennas fed from the same point. On Wed, 08 Jan 2014 15:45:48 -0500, you wrote: >An OCF is an unbalanced antenna and it must have a choke to keep RF off >the feed line into the shack. I use about ten turns of coax on a 4 inch >PVC pipe right outside the wall where the feed comes into the house. It >might be more or less, I am not at home to look. You can research it. >Other choke baluns would help, if they present a high enough impedance. > >That seems to have cured RFI problems for me but I have occasionally >felt like I needed more isolation. Many people have advised me to get >rid of the OCF and go with something balanced but it suits my multi-band >needs for now. > >I am pretty sure RF on the feed line would cause the tuning circuits in >the KAT to act crazy. I'll leave that one for the Elecraft gurus to >answer. > >Buck >k4ia > >On 1/8/2014 5:57 AM, Ray Coles wrote: >> As the original poster under this heading I figured you might be interested >> to know what I have achieved so far, even though I am not yet ready to send >> the white smoke up the chimney. Briefly, my problem was that my KAT500 >> would go into uncommanded tunes during a QSO, usually on digital modes.The >> practical result was that I had to restrict TX power to less than 40Watts on >> most bands to avoid a burst from the Chicago Piano in the KAT. I had assumed >> an antenna/feeder problem and had changed every last connector, wire, balun >> and insulator in my system before asking for help from the Reflector Brains >> Trust. All of the other people who subsequently reported a similar problem >> made me feel a little better, and I also received a lot of diagnoses and >> practical advice which I have followed or will follow soon. One of the >> simplest was from Ron WB4OOA: Carry out a K3 Gain Calibration via the K3 >> Utility (I had to download the latest Utility version to make this work >> properly) then Install the KAT500 V1.42 Beta (Not quite as easy as it >> sounds). After this things were better, and my power setting on the K3 >> always appeared on the KPA500 wattmeter. I could now operate at higher power >> on some bands but had to stay below 40W on 40m. I had also adjusted the per >> band retune trigger SWRs upwards via the KAT500 Utility which also helped a >> little. >> >> I remain convinced though, that the basic trigger problem lies with the >> antenna system (an OCF multiband dipole) and I am continuing to work on this >> aspect using my analyser. Why it should have suddenly kicked off after many >> months of solid performance, and why changing everything hasn't yet cured it >> remains a mystery. My next steps are to try a choke balun on the feeder >> (parts now to hand) and to prune the antenna to get a better resonance on >> the bands of interest. Now if only this darn rain would stop! (I still think >> some tweaking of the KAT500 software might also help!) >> >> >> >> Ray Coles, C.Eng. M0XDL >> >> 10 Littlemoor Road, >> >> Weymouth DT3 6AA >> >> Tel: +44 (0) 1305 833699 >> >> Mob: 07831 516517 >> >> >> >> >> >> >> >> ______________________________________________________________ >> 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 ______________________________________________________________ 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
Amateur Radio Operator N5GE
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