Re: Topband: Rotator creating spur on 1820- results
Thanks George "AM 890 x 2 = 1780 KHz + 1730 KHz = 3510 <- - your 80 meter birdie." Yep, that works, except I had a typo when saying one of the contributor to the 160 problem was 1730. No station on 1730. Copied the wrong number off my notes. Sorry. I should have said 1310. My 80 meter problem is also due to that 1310 station, (1310 + 890) + 1310 = 3510. Both very strong local stations. The really tough question is where is that mixer. Can't do much about the stations. Only hope is to find the mixer. There are lots of possibilities. Might be close, or maybe not. That 1820 problem was generated on my tower and radiated to my receiving antennas located 550 ft from the tower. Very glad to get rid of that one. Guess I will have to see if I can track the 80 meter problem by using a portable 3510 receiver. I can locate the general direction using my receiving antennas and it's not in the direction of either of those two stations. Funny thing is the 3510 birdie is minimum when the antenna is pointed at the 890 tower and I know that is one of the contributors. When pointed at that station. my receiving antenna has a null at 96 degrees to that station and that is the direction to the mixer. That direction passes very close to my tower so I was expecting to maybe see some change in the 80 meter problem when I put that strap on the rotator, but it didn't happen. Jerry, K4SAV On 11/5/2017 5:45 PM, k...@voyager.net wrote: Hi Jerry & Topbanders, Doing the math from the info below: AM 890 x 2 = 1780 KHz + 1730 KHz = 3510 <- - your 80 meter birdie. I hope this makes sense and helps solve the puzzle. As I noted before, it is probably generated off site by some rusty connection in a radio tower that is a nasty diode as well. 73, George, K8GG... _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820- results
*I put the strap around the rotator today. I no longer have a birdie on 1820. Not a trace of it on any antenna. Based on symptons, I can only conclude it was caused by intermittent contact at the rotator bearings or by intermittent contact at the bearing on top of the tower. Diodes inside the rotator do not seem to be a problem.** ** **The strap had no effect on my 3510 spur, which means the mixer for that one is somewhere else. That one is not a big problem because it goes away at nighttime due to one of the stations being daytime only.** ** **The strap is 1/4 inch diameter twisted (not braided) stranded tin plated wire, very flexible. Length is about 16 inches.** ** **Special thanks to Lloyd N9LB and Hank K7HP who had the correct answer.** ** **Jerry, K4SAV - happy camper* On 11/2/2017 5:27 PM, K4SAV wrote: Likely all the spurs you see on 160 that are caused by AM stations will land on 10 kHz increments because the stations are spaced on 10 kHz increments. I identified one of the stations that was a big contributor to my problem and that was on 1730. I haven't found the other station yet. I expected the station on 890 to be a contributor since it is only 1700 ft from my antenna but I don't think it is the one. (It is a contributor to the spur that happens on 3510). Regardless of which stations are involved, the main problem is that the mixing is being created near my rotator, and probably inside it somewhere. I have to kill the mixer somehow. More than likely the stations are clean. It will be interesting to see if the same mixer is causing both spurs, 1820 and 3510. Fortunately the 3510 spur goes away at night because one of the contributor stations is daytime only. Interesting video by N8PR, but he is fighting a different problem from what I have, I do not have a strap around the rotator. That's worth a try. Thanks Lloyd and Hank. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
I had a similar situation when I lived outside Mesa, AZ. Two AM BCB stations were mixing creating a mixer spur within 160. I was using an IC-756 PRO at the time. I used an ICE 430B HP filter in the receiver antenna line. The Icom didn't have RX antenna in/out jacks, so I had to add them using RG-174/U. It solved the problem. The current version seems to be https://www.arraysolutions.com/as-1r8-hpf-rx . 73, Jim N7US -Original Message- Thanks George. I'm pretty sure that the mixer in my case is the rotator or mast contact. All I have to do to knock the spur down is just barely move the rotator. It will stay down for a few minutes, then return. The mechanism causing that is unknown at this point. I see some possibilities. It could be due to intermittent contact in the rotator bearings, or intermittent contact at the tower top bearing, or due to the diodes in the rotator power lines (inside the rotator). Looks like those diodes have no RF bypassing. I can guess why Yaesu didn't do that. Caps can easily fail when they are in circuits near lightning. If that happens the rotator would have to come down for repair. That would not be a popular feature. I'm hoping it's not those diodes. The fact that the spur drops for a few minutes after moving the rotator, is a vote in favor of something mechanical. The suggestion of a strap around the rotator is easy to do, so I will try that (after the storms get out of our area). If the mixer is the rotator bearings or that top bearing that strap should help. If the mixer is the diodes, the strap may do nothing. That rotator may be the mixer for both my 1820 and 3510 spurs. My 80 meter problem is from stations on 1310 and 890. (1310 + 890) + 1310 = 3510. Not sure about the contributors for the 160 spur, other than one of the stations is on 1730. If you have a problem and the mixer is at some distance from your station you may never find it. I was originally worried that my 80 meter problem was due to a rusty fence (lots of those around here), but it could turn out to be that rotator. My old MFJ analyzer was completely worthless on 160 due to a very close AM station. My new AA-600 is affected too but to a much lesser degree. I have a good homebrew high pass filter for my receiving antennas, 60 dB minimum. I put a 90 dB notch on the frequency of that AM station nearest me. Jerry, K4SAV On 11/3/2017 8:46 PM, k...@voyager.net wrote: > Jerry, et. al., > > I didn't have the problems from my own installation, but I used to > live about 1/2 mile from an AM 930 station and there would be a 2nd > harmonic spur at 1860 and a mixer spur of 2 x 1400 - 930 = 1870 KHz. > W0CD helped me find & build hi-pass filters in old ARRL Handbooks for my RX antennas. > The only way I could check the SWR was to turn the transceiver down to > about 2 watts and feed the beverages or pennants and scan the band to > make sure the terminations, etc., were OK. > > I have repeatedly missed a couple of 160 contest stations in the > former Yugoslavic area because they would run on 1870. Even 4+ miles > away at W8TOP in the CQ160 CW Contest there was no way for us to > listen thru the harmonic mixer. There was always some diode > rectifications off site so to speak. We suspect old support towers > for FM stations and a nearly abandoned AM station between the AM930 > and W8TOP, but, since the spur is not on site, we just live with it. > > The suggestion of a jumper across the rotator makes good sense if some > dissimilar metals in the unit are making the diode. > > GL, George, K8GG > > > > > >> Likely all the spurs you see on 160 that are caused by AM stations >> will land on 10 kHz increments because the stations are spaced on 10 >> kHz increments. I identified one of the stations that was a big >> contributor to my problem and that was on 1730. I haven't found the >> other station yet. I expected the station on 890 to be a contributor >> since it is only >> 1700 ft from my antenna but I don't think it is the one. (It is a >> contributor to the spur that happens on 3510). Regardless of which >> stations are involved, the main problem is that the mixing is being >> created near my rotator, and probably inside it somewhere. I have to >> kill the mixer somehow. More than likely the stations are clean. It >> will be interesting to see if the same mixer is causing both spurs, >> 1820 and 3510. Fortunately the 3510 spur goes away at night because >> one of the contributor stations is daytime only. >> >> Interesting video by N8PR, but he is fighting a different problem >> from what I have, >> >> I do not have a strap around the rotator. That's worth a try. Thanks >> Lloyd and Hank. >> >> Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Thanks George. I'm pretty sure that the mixer in my case is the rotator or mast contact. All I have to do to knock the spur down is just barely move the rotator. It will stay down for a few minutes, then return. The mechanism causing that is unknown at this point. I see some possibilities. It could be due to intermittent contact in the rotator bearings, or intermittent contact at the tower top bearing, or due to the diodes in the rotator power lines (inside the rotator). Looks like those diodes have no RF bypassing. I can guess why Yaesu didn't do that. Caps can easily fail when they are in circuits near lightning. If that happens the rotator would have to come down for repair. That would not be a popular feature. I'm hoping it's not those diodes. The fact that the spur drops for a few minutes after moving the rotator, is a vote in favor of something mechanical. The suggestion of a strap around the rotator is easy to do, so I will try that (after the storms get out of our area). If the mixer is the rotator bearings or that top bearing that strap should help. If the mixer is the diodes, the strap may do nothing. That rotator may be the mixer for both my 1820 and 3510 spurs. My 80 meter problem is from stations on 1310 and 890. (1310 + 890) + 1310 = 3510. Not sure about the contributors for the 160 spur, other than one of the stations is on 1730. If you have a problem and the mixer is at some distance from your station you may never find it. I was originally worried that my 80 meter problem was due to a rusty fence (lots of those around here), but it could turn out to be that rotator. My old MFJ analyzer was completely worthless on 160 due to a very close AM station. My new AA-600 is affected too but to a much lesser degree. I have a good homebrew high pass filter for my receiving antennas, 60 dB minimum. I put a 90 dB notch on the frequency of that AM station nearest me. Jerry, K4SAV On 11/3/2017 8:46 PM, k...@voyager.net wrote: Jerry, et. al., I didn't have the problems from my own installation, but I used to live about 1/2 mile from an AM 930 station and there would be a 2nd harmonic spur at 1860 and a mixer spur of 2 x 1400 - 930 = 1870 KHz. W0CD helped me find & build hi-pass filters in old ARRL Handbooks for my RX antennas. The only way I could check the SWR was to turn the transceiver down to about 2 watts and feed the beverages or pennants and scan the band to make sure the terminations, etc., were OK. I have repeatedly missed a couple of 160 contest stations in the former Yugoslavic area because they would run on 1870. Even 4+ miles away at W8TOP in the CQ160 CW Contest there was no way for us to listen thru the harmonic mixer. There was always some diode rectifications off site so to speak. We suspect old support towers for FM stations and a nearly abandoned AM station between the AM930 and W8TOP, but, since the spur is not on site, we just live with it. The suggestion of a jumper across the rotator makes good sense if some dissimilar metals in the unit are making the diode. GL, George, K8GG Likely all the spurs you see on 160 that are caused by AM stations will land on 10 kHz increments because the stations are spaced on 10 kHz increments. I identified one of the stations that was a big contributor to my problem and that was on 1730. I haven't found the other station yet. I expected the station on 890 to be a contributor since it is only 1700 ft from my antenna but I don't think it is the one. (It is a contributor to the spur that happens on 3510). Regardless of which stations are involved, the main problem is that the mixing is being created near my rotator, and probably inside it somewhere. I have to kill the mixer somehow. More than likely the stations are clean. It will be interesting to see if the same mixer is causing both spurs, 1820 and 3510. Fortunately the 3510 spur goes away at night because one of the contributor stations is daytime only. Interesting video by N8PR, but he is fighting a different problem from what I have, I do not have a strap around the rotator. That's worth a try. Thanks Lloyd and Hank. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Jerry, et. al., I didn't have the problems from my own installation, but I used to live about 1/2 mile from an AM 930 station and there would be a 2nd harmonic spur at 1860 and a mixer spur of 2 x 1400 - 930 = 1870 KHz. W0CD helped me find & build hi-pass filters in old ARRL Handbooks for my RX antennas. The only way I could check the SWR was to turn the transceiver down to about 2 watts and feed the beverages or pennants and scan the band to make sure the terminations, etc., were OK. I have repeatedly missed a couple of 160 contest stations in the former Yugoslavic area because they would run on 1870. Even 4+ miles away at W8TOP in the CQ160 CW Contest there was no way for us to listen thru the harmonic mixer. There was always some diode rectifications off site so to speak. We suspect old support towers for FM stations and a nearly abandoned AM station between the AM930 and W8TOP, but, since the spur is not on site, we just live with it. The suggestion of a jumper across the rotator makes good sense if some dissimilar metals in the unit are making the diode. GL, George, K8GG > Likely all the spurs you see on 160 that are caused by AM stations will > land on 10 kHz increments because the stations are spaced on 10 kHz > increments. I identified one of the stations that was a big contributor > to my problem and that was on 1730. I haven't found the other station > yet. I expected the station on 890 to be a contributor since it is only > 1700 ft from my antenna but I don't think it is the one. (It is a > contributor to the spur that happens on 3510). Regardless of which > stations are involved, the main problem is that the mixing is being > created near my rotator, and probably inside it somewhere. I have to > kill the mixer somehow. More than likely the stations are clean. It > will be interesting to see if the same mixer is causing both spurs, 1820 > and 3510. Fortunately the 3510 spur goes away at night because one of > the contributor stations is daytime only. > > Interesting video by N8PR, but he is fighting a different problem from > what I have, > > I do not have a strap around the rotator. That's worth a try. Thanks > Lloyd and Hank. > > Jerry, K4SAV > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Likely all the spurs you see on 160 that are caused by AM stations will land on 10 kHz increments because the stations are spaced on 10 kHz increments. I identified one of the stations that was a big contributor to my problem and that was on 1730. I haven't found the other station yet. I expected the station on 890 to be a contributor since it is only 1700 ft from my antenna but I don't think it is the one. (It is a contributor to the spur that happens on 3510). Regardless of which stations are involved, the main problem is that the mixing is being created near my rotator, and probably inside it somewhere. I have to kill the mixer somehow. More than likely the stations are clean. It will be interesting to see if the same mixer is causing both spurs, 1820 and 3510. Fortunately the 3510 spur goes away at night because one of the contributor stations is daytime only. Interesting video by N8PR, but he is fighting a different problem from what I have, I do not have a strap around the rotator. That's worth a try. Thanks Lloyd and Hank. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Hi Lloyd: I would not recommend using braid to connect the mast to the tower. The braid will take on water quickly and become less effective. A large flexible insulated cable is the best way to go. There are several ways to do what you describe. I think the bypass is very good practice to eliminate noise and RFI. I have all of my rotors and bearings bypassed. We actually put a kit of parts together here at DXE to do just that. Most guys have enough stuff in their spare parts area to roll their own bearing/rotor bypass cable, but the photos and drawings on the link below will give you the idea. https://www.dxengineering.com/parts/dxe-bbgk-2-25-p 73 Tim K3LR -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Lloyd - N9LB Sent: Thursday, November 02, 2017 1:12 PM To: topband@contesting.com Subject: Re: Topband: Rotator creating spur on 1820 Do you have a heavy gauge flexible strap jumpering the mast pipe to the top of the tower? The mast pipe must be at the same electrical potential as the tower. The thrust bearing and rotor motor probably is not a low impedance path. I use the commonly available 1 inch wide woven braid / ground strap material to connect my mast pipe to the top of the tower. It runs parallel to my coax rotor loop at tower top ( about 24 inches long ). 73 Lloyd - N9LB > - Original Message - > > From: "K4SAV" <radi...@charter.net> > To: topband@contesting.com > Sent: Thursday, November 2, 2017 2:40:49 PM > Subject: Topband: Rotator creating spur on 1820 > > I have a problem for which someone on this forum has the solution. I > know that because I have seen that message sometime in the past. > > The problem is that my rotator is rectifying a couple of AM station > signals and creating a spur on 1820. It's normally pretty weak on my > receiving antennas but sometimes it's a problem. I found that if I > listen on my XM-240 near that rotator it can be very loud. As soon as > I move the rotator it causes the spur to go away, or become weak. A > few minutes later it is back again. It pops in and out. > > So who had the problem and how did you fix it? > > Note that my XM-240 actually shows a low SWR on 160. That's because > the > XM-240 balun doesn't work well on 160 and the common mode currents on > the feedline couple to the tower and the tower becomes the real > antenna on 160. So in this case the tower is the antenna and it has > that rotator cable against it picking up max signal from that cable > (also radiating it to my other antennas). No, the XM-240 is not used > on 160 (except to find the source of this problem). > > The rotator is a Yaesu G-2800DXA. > > Jerry, K4SAV > _ > Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Do you have a heavy gauge flexible strap jumpering the mast pipe to the top of the tower? The mast pipe must be at the same electrical potential as the tower. The thrust bearing and rotor motor probably is not a low impedance path. I use the commonly available 1 inch wide woven braid / ground strap material to connect my mast pipe to the top of the tower. It runs parallel to my coax rotor loop at tower top ( about 24 inches long ). 73 Lloyd - N9LB > - Original Message - > > From: "K4SAV" <radi...@charter.net> > To: topband@contesting.com > Sent: Thursday, November 2, 2017 2:40:49 PM > Subject: Topband: Rotator creating spur on 1820 > > I have a problem for which someone on this forum has the solution. I > know that because I have seen that message sometime in the past. > > The problem is that my rotator is rectifying a couple of AM station > signals and creating a spur on 1820. It's normally pretty weak on my > receiving antennas but sometimes it's a problem. I found that if I > listen on my XM-240 near that rotator it can be very loud. As soon as > I move the rotator it causes the spur to go away, or become weak. A > few minutes later it is back again. It pops in and out. > > So who had the problem and how did you fix it? > > Note that my XM-240 actually shows a low SWR on 160. That's because > the > XM-240 balun doesn't work well on 160 and the common mode currents on > the feedline couple to the tower and the tower becomes the real > antenna on 160. So in this case the tower is the antenna and it has > that rotator cable against it picking up max signal from that cable > (also radiating it to my other antennas). No, the XM-240 is not used > on 160 (except to find the source of this problem). > > The rotator is a Yaesu G-2800DXA. > > Jerry, K4SAV > _ > Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Interesting you have the spur on 1820. I have the exact same situation on 1820 as well. Sometimes I can actually pull weak audio off the spur but have not been able to identify which local station or stations are mixing to create the spur. It never varies in strength and I just assumed it was part of the hazards of operating on topband. Didn't consider it might be the rotor and or cable going up the tower. In my situation it hasn't caused enough interference to detract form DXing so far in at lest 20 years +. Good information to have for those closer to AM broadcast towers in the future. Dick K9RT In a message dated 11/2/2017 10:41:52 A.M. Eastern Daylight Time, radi...@charter.net writes: I have a problem for which someone on this forum has the solution. I know that because I have seen that message sometime in the past. The problem is that my rotator is rectifying a couple of AM station signals and creating a spur on 1820. It's normally pretty weak on my receiving antennas but sometimes it's a problem. I found that if I listen on my XM-240 near that rotator it can be very loud. As soon as I move the rotator it causes the spur to go away, or become weak. A few minutes later it is back again. It pops in and out. So who had the problem and how did you fix it? Note that my XM-240 actually shows a low SWR on 160. That's because the XM-240 balun doesn't work well on 160 and the common mode currents on the feedline couple to the tower and the tower becomes the real antenna on 160. So in this case the tower is the antenna and it has that rotator cable against it picking up max signal from that cable (also radiating it to my other antennas). No, the XM-240 is not used on 160 (except to find the source of this problem). The rotator is a Yaesu G-2800DXA. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Hi Jerry Any cable/wire is an antenna. If it long enough or near 120ft it will work like a 1/4 wave vertical. The path to the ground is important because the current will add to other circuits at the input of the receiver. Even the AC line can be the return path to ground. You can watch the movie bellow and you can see the same problem at N8PR station and how Pete fixed the common mode noise problem with few chokes.. https://www.youtube.com/watch?v=-4os4qcaT08 Interesting that disconnecting the rotor box from the AC line stops the noise. Some BC IMD can be generated by oxidation on towers or external metal structures as well. 73's JC N4IS -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of donov...@starpower.net Sent: Thursday, November 02, 2017 10:47 AM To: topband@contesting.com Subject: Re: Topband: Rotator creating spur on 1820 Hi Jerry, There's a good chance the problem originates inyour control box rather than your rotator. Does the problem stop if you completely disconnect the control box? 73 Frank W3LPL - Original Message - From: "K4SAV" <radi...@charter.net> To: topband@contesting.com Sent: Thursday, November 2, 2017 2:40:49 PM Subject: Topband: Rotator creating spur on 1820 I have a problem for which someone on this forum has the solution. I know that because I have seen that message sometime in the past. The problem is that my rotator is rectifying a couple of AM station signals and creating a spur on 1820. It's normally pretty weak on my receiving antennas but sometimes it's a problem. I found that if I listen on my XM-240 near that rotator it can be very loud. As soon as I move the rotator it causes the spur to go away, or become weak. A few minutes later it is back again. It pops in and out. So who had the problem and how did you fix it? Note that my XM-240 actually shows a low SWR on 160. That's because the XM-240 balun doesn't work well on 160 and the common mode currents on the feedline couple to the tower and the tower becomes the real antenna on 160. So in this case the tower is the antenna and it has that rotator cable against it picking up max signal from that cable (also radiating it to my other antennas). No, the XM-240 is not used on 160 (except to find the source of this problem). The rotator is a Yaesu G-2800DXA. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Unfortunately no. Already tried that. That would have been too easy of a fix. Jerry On 11/2/2017 9:47 AM, donov...@starpower.net wrote: Hi Jerry, There's a good chance the problem originates inyour control box rather than your rotator. Does the problem stop if you completely disconnect the control box? 73 Frank W3LPL - Original Message - From: "K4SAV" <radi...@charter.net> To: topband@contesting.com Sent: Thursday, November 2, 2017 2:40:49 PM Subject: Topband: Rotator creating spur on 1820 I have a problem for which someone on this forum has the solution. I know that because I have seen that message sometime in the past. The problem is that my rotator is rectifying a couple of AM station signals and creating a spur on 1820. It's normally pretty weak on my receiving antennas but sometimes it's a problem. I found that if I listen on my XM-240 near that rotator it can be very loud. As soon as I move the rotator it causes the spur to go away, or become weak. A few minutes later it is back again. It pops in and out. So who had the problem and how did you fix it? Note that my XM-240 actually shows a low SWR on 160. That's because the XM-240 balun doesn't work well on 160 and the common mode currents on the feedline couple to the tower and the tower becomes the real antenna on 160. So in this case the tower is the antenna and it has that rotator cable against it picking up max signal from that cable (also radiating it to my other antennas). No, the XM-240 is not used on 160 (except to find the source of this problem). The rotator is a Yaesu G-2800DXA. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Rotator creating spur on 1820
Hi Jerry, There's a good chance the problem originates inyour control box rather than your rotator. Does the problem stop if you completely disconnect the control box? 73 Frank W3LPL - Original Message - From: "K4SAV" <radi...@charter.net> To: topband@contesting.com Sent: Thursday, November 2, 2017 2:40:49 PM Subject: Topband: Rotator creating spur on 1820 I have a problem for which someone on this forum has the solution. I know that because I have seen that message sometime in the past. The problem is that my rotator is rectifying a couple of AM station signals and creating a spur on 1820. It's normally pretty weak on my receiving antennas but sometimes it's a problem. I found that if I listen on my XM-240 near that rotator it can be very loud. As soon as I move the rotator it causes the spur to go away, or become weak. A few minutes later it is back again. It pops in and out. So who had the problem and how did you fix it? Note that my XM-240 actually shows a low SWR on 160. That's because the XM-240 balun doesn't work well on 160 and the common mode currents on the feedline couple to the tower and the tower becomes the real antenna on 160. So in this case the tower is the antenna and it has that rotator cable against it picking up max signal from that cable (also radiating it to my other antennas). No, the XM-240 is not used on 160 (except to find the source of this problem). The rotator is a Yaesu G-2800DXA. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Rotator creating spur on 1820
I have a problem for which someone on this forum has the solution. I know that because I have seen that message sometime in the past. The problem is that my rotator is rectifying a couple of AM station signals and creating a spur on 1820. It's normally pretty weak on my receiving antennas but sometimes it's a problem. I found that if I listen on my XM-240 near that rotator it can be very loud. As soon as I move the rotator it causes the spur to go away, or become weak. A few minutes later it is back again. It pops in and out. So who had the problem and how did you fix it? Note that my XM-240 actually shows a low SWR on 160. That's because the XM-240 balun doesn't work well on 160 and the common mode currents on the feedline couple to the tower and the tower becomes the real antenna on 160. So in this case the tower is the antenna and it has that rotator cable against it picking up max signal from that cable (also radiating it to my other antennas). No, the XM-240 is not used on 160 (except to find the source of this problem). The rotator is a Yaesu G-2800DXA. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband
