From w9ac at arrl.net Mon Nov 9 08:39:29 2020 From: w9ac at arrl.net (Paul Christensen) Date: Mon, 9 Nov 2020 08:39:29 -0500 Subject: [Hi-zreceivingarraydiscussions] BC IMD Message-ID: <004501d6b69d$c06ce110$4146a330$@arrl.net> Lee, N4CC and I installed the new Hi-Z preamps on our 160m 8-cicle array. Balance is better than with the old preamps and while listening last night, F/B was excellent with no signs of skewing. However, starting at 6:15am this morning, I heard significant broadcast band IMD every 10 kHz on 160m. We have a Hi-Z HPF between the controller and Hi-Z final preamp. The main culprit seems to be WBOB-AM. In a prior life I was Director of Engineering at the station. It operates with 5KW on 600 kHz. ND daytime, and 5-tower DA inline array at night with a very narrow lobe to the east, right over Jacksonville. Our site is about 15 miles NW of WBOB-AM and as such, the nighttime pattern has very little effect on us. But the ND daytime field strength is very strong. I don't recall the post-sunrise switch time for the month of November, but I'm guessing it's at 6:15 am. I see that Jeff, AC0C is using a notch filter right at each Hi-Z whip antenna preamps. I will do some more investigating but if it turns out that we need the filters, do you supply these? Any impact on system balance with these filters? Also, I am not sure if 600 kHz is the only Jacksonville station causing a problem. It's certainly the main cause at the moment. Others that are potential candidates in Jacksonville are at 690 kHz and 1460 kHz. By the way, I don't recall having the BC IMD issue with the prior antenna preamps. Just an observation. Paul, W9AC From w9ac at arrl.net Mon Nov 9 08:43:01 2020 From: w9ac at arrl.net (Paul Christensen) Date: Mon, 9 Nov 2020 08:43:01 -0500 Subject: [Hi-zreceivingarraydiscussions] BC IMD In-Reply-To: <004501d6b69d$c06ce110$4146a330$@arrl.net> References: <004501d6b69d$c06ce110$4146a330$@arrl.net> Message-ID: <004601d6b69e$3e9ad1f0$bbd075d0$@arrl.net> Sorry folks. This was meant only for Lee, not the list. I'm not paying attention this morning. -----Original Message----- From: Hi-zreceivingarraydiscussions On Behalf Of Paul Christensen Sent: Monday, November 9, 2020 8:39 AM To: 'Hi-Z Receiving Array Discussions' Cc: n4cc at windstream.net Subject: [Hi-zreceivingarraydiscussions] BC IMD Lee, N4CC and I installed the new Hi-Z preamps on our 160m 8-cicle array. Balance is better than with the old preamps and while listening last night, F/B was excellent with no signs of skewing. However, starting at 6:15am this morning, I heard significant broadcast band IMD every 10 kHz on 160m. We have a Hi-Z HPF between the controller and Hi-Z final preamp. The main culprit seems to be WBOB-AM. In a prior life I was Director of Engineering at the station. It operates with 5KW on 600 kHz. ND daytime, and 5-tower DA inline array at night with a very narrow lobe to the east, right over Jacksonville. Our site is about 15 miles NW of WBOB-AM and as such, the nighttime pattern has very little effect on us. But the ND daytime field strength is very strong. I don't recall the post-sunrise switch time for the month of November, but I'm guessing it's at 6:15 am. I see that Jeff, AC0C is using a notch filter right at each Hi-Z whip antenna preamps. I will do some more investigating but if it turns out that we need the filters, do you supply these? Any impact on system balance with these filters? Also, I am not sure if 600 kHz is the only Jacksonville station causing a problem. It's certainly the main cause at the moment. Others that are potential candidates in Jacksonville are at 690 kHz and 1460 kHz. By the way, I don't recall having the BC IMD issue with the prior antenna preamps. Just an observation. Paul, W9AC _______________________________________________ Hi-zreceivingarraydiscussions mailing list Hi-zreceivingarraydiscussions at hizantennas.com http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_h izantennas.com From k7tjr at msn.com Mon Nov 9 12:31:07 2020 From: k7tjr at msn.com (Lee STRAHAN) Date: Mon, 9 Nov 2020 17:31:07 +0000 Subject: [Hi-zreceivingarraydiscussions] BC IMD In-Reply-To: <004501d6b69d$c06ce110$4146a330$@arrl.net> References: <004501d6b69d$c06ce110$4146a330$@arrl.net> Message-ID: Hi Paul and group, It is time I addressed this here on the reflector. First it is imperative that the supply voltage at the Hi-Z amps be up around 13 volts or maybe 13.5. This gives the best operating point for the best IMD specs. Also, the new V2 amps draw a bit more current than the older amps so you may want to check that voltage first. Secondly I do make some filters for the Hi-Z amps that have a notch in the BC band and usually solves any BCI problems. I will send this as 2 messages because the reflector is limited in message space. Lee K7TJR Lee, N4CC and I installed the new Hi-Z preamps on our 160m 8-cicle array. Balance is better than with the old preamps and while listening last night, F/B was excellent with no signs of skewing. However, starting at 6:15am this morning, I heard significant broadcast band IMD every 10 kHz on 160m. We have a Hi-Z HPF between the controller and Hi-Z final preamp. From k7tjr at msn.com Mon Nov 9 12:46:29 2020 From: k7tjr at msn.com (Lee STRAHAN) Date: Mon, 9 Nov 2020 17:46:29 +0000 Subject: [Hi-zreceivingarraydiscussions] BCI filters Message-ID: I now make 2 versions of the BCI filter. I have to closely match inductors and capacitors so each element is the same. The old style amp filters were mounted on the outside of the enclosures on the antenna input terminals. They have occasionally suffered from some problems due to the voltage on the terminals and moisture seeping into the components. Each element/amp needs a filter. The new amps have a new design using tiny parts and will fit inside the new enclosures. Maybe not something all users would be in the position to do. Actually I am quite surprised that Paul has seen IMD with the new amps and not the old as bench tests have shown better IMD specs on the new amps. Maybe something else at work here. I sell the filters direct and anyone needing filters should contact me directly at contact at hizantennas.com . So far they have removed or way diminished BCI spurs to an acceptable level. I do not have a lot of the filter parts in stock at the moment but will be able to support more soon. I will eventually post some pictures about this subject. Lee K7TJR Hi-Z Antennas From k7tjr at msn.com Mon Nov 9 12:55:37 2020 From: k7tjr at msn.com (Lee STRAHAN) Date: Mon, 9 Nov 2020 17:55:37 +0000 Subject: [Hi-zreceivingarraydiscussions] BC IMD In-Reply-To: References: <004501d6b69d$c06ce110$4146a330$@arrl.net> Message-ID: One important point I forgot to mention. When measuring the antenna terminal voltage on the V2 Hi-Z amps you must measure between the antenna input and the RG-6 shield to get the actual amplifier voltage. The new amps are AC coupled to ground eliminating a DC ground loop to the ground post. Typical new amps are around 6.3 Volts DC instead of the old amps at 4 to 5 VDC. Lee K7TJR Hi-Z Antennas From w5xz at att.net Wed Nov 11 09:59:07 2020 From: w5xz at att.net (dan edwards) Date: Wed, 11 Nov 2020 14:59:07 +0000 (UTC) Subject: [Hi-zreceivingarraydiscussions] BC IMD In-Reply-To: <004601d6b69e$3e9ad1f0$bbd075d0$@arrl.net> References: <004501d6b69d$c06ce110$4146a330$@arrl.net> <004601d6b69e$3e9ad1f0$bbd075d0$@arrl.net> Message-ID: <1611863329.4253164.1605106747463@mail.yahoo.com> paul, was that what you heard VU2 with the other night?? my LAST zone, IF i ever get it 73, w5xz, dan On Monday, November 9, 2020, 07:45:17 AM CST, Paul Christensen wrote: Sorry folks.? This was meant only for Lee, not the list.? I'm not paying attention this morning.? -----Original Message----- From: Hi-zreceivingarraydiscussions On Behalf Of Paul Christensen Sent: Monday, November 9, 2020 8:39 AM To: 'Hi-Z Receiving Array Discussions' Cc: n4cc at windstream.net Subject: [Hi-zreceivingarraydiscussions] BC IMD Lee, N4CC and I installed the new Hi-Z preamps on our 160m 8-cicle array. Balance is better than with the old preamps and while listening last night, F/B was excellent with no signs of skewing.? However, starting at 6:15am this morning, I heard significant broadcast band IMD every 10 kHz on 160m. We have a Hi-Z HPF between the controller and Hi-Z final preamp.? The main culprit seems to be WBOB-AM.? In a prior life I was Director of Engineering at the station.? It operates with 5KW on 600 kHz.? ND daytime, and 5-tower DA inline array at night with a very narrow lobe to the east, right over Jacksonville.? Our site is about 15 miles NW of WBOB-AM and as such, the nighttime pattern has very little effect on us.? But the ND daytime field strength is very strong.? I don't recall the post-sunrise switch time for the month of November, but I'm guessing it's at 6:15 am. I see that Jeff, AC0C is using a notch filter right at each Hi-Z whip antenna preamps.? I will do some more investigating but if it turns out that we need the filters, do you supply these?? Any impact on system balance with these filters?? Also, I am not sure if 600 kHz is the only Jacksonville station causing a problem.? It's certainly the main cause at the moment. Others that are potential candidates in Jacksonville are at 690 kHz and 1460 kHz.? By the way, I don't recall having the BC IMD issue with the prior antenna preamps.? Just an observation. Paul, W9AC _______________________________________________ Hi-zreceivingarraydiscussions mailing list Hi-zreceivingarraydiscussions at hizantennas.com http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_h izantennas.com _______________________________________________ Hi-zreceivingarraydiscussions mailing list Hi-zreceivingarraydiscussions at hizantennas.com http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_hizantennas.com From w9ac at arrl.net Wed Nov 11 15:24:56 2020 From: w9ac at arrl.net (Paul Christensen) Date: Wed, 11 Nov 2020 15:24:56 -0500 Subject: [Hi-zreceivingarraydiscussions] BC IMD In-Reply-To: <1611863329.4253164.1605106747463@mail.yahoo.com> References: <004501d6b69d$c06ce110$4146a330$@arrl.net> <004601d6b69e$3e9ad1f0$bbd075d0$@arrl.net> <1611863329.4253164.1605106747463@mail.yahoo.com> Message-ID: <009d01d6b868$b95281b0$2bf78510$@arrl.net> Yes. The 160m 8-circle worked great last night. For about three minutes, VU2GSM was an honest S7 on the K3 S meter. S5 about 10 minutes before and after the peak. Copy was from the NE as expected. No copy at all in the N and E directions. F/B from W1AW last night was better than 40 dB. S9 NE and nothing heard in the SW position. All switch positions are definitely working. This afternoon, N4CC and I just finished re-deploying radials for the "T" top transmit antenna. Sure wished it was ready yesterday! 100 ft vertical section and a flat T top that is between 80-100 ft. We could not remember the length as we discussed it today. I do want to validate 100 ft to ensure there's little or no interaction with the 40m Yagi. IMD update: clean for the last 48 hours. I did adjust the power supply current threshold on an HP lab supply and validated system voltages. Nothing conclusive though. We'll see how it goes. Paul, W9AC -----Original Message----- From: Hi-zreceivingarraydiscussions On Behalf Of dan edwards Sent: Wednesday, November 11, 2020 9:59 AM To: Hi-Z Receiving Array Discussions Subject: Re: [Hi-zreceivingarraydiscussions] BC IMD paul, was that what you heard VU2 with the other night?? my LAST zone, IF i ever get it 73, w5xz, dan On Monday, November 9, 2020, 07:45:17 AM CST, Paul Christensen wrote: Sorry folks. This was meant only for Lee, not the list. I'm not paying attention this morning. -----Original Message----- From: Hi-zreceivingarraydiscussions On Behalf Of Paul Christensen Sent: Monday, November 9, 2020 8:39 AM To: 'Hi-Z Receiving Array Discussions' Cc: n4cc at windstream.net Subject: [Hi-zreceivingarraydiscussions] BC IMD Lee, N4CC and I installed the new Hi-Z preamps on our 160m 8-cicle array. Balance is better than with the old preamps and while listening last night, F/B was excellent with no signs of skewing. However, starting at 6:15am this morning, I heard significant broadcast band IMD every 10 kHz on 160m. We have a Hi-Z HPF between the controller and Hi-Z final preamp. The main culprit seems to be WBOB-AM. In a prior life I was Director of Engineering at the station. It operates with 5KW on 600 kHz. ND daytime, and 5-tower DA inline array at night with a very narrow lobe to the east, right over Jacksonville. Our site is about 15 miles NW of WBOB-AM and as such, the nighttime pattern has very little effect on us. But the ND daytime field strength is very strong. I don't recall the post-sunrise switch time for the month of November, but I'm guessing it's at 6:15 am. I see that Jeff, AC0C is using a notch filter right at each Hi-Z whip antenna preamps. I will do some more investigating but if it turns out that we need the filters, do you supply these? Any impact on system balance with these filters? Also, I am not sure if 600 kHz is the only Jacksonville station causing a problem. It's certainly the main cause at the moment. Others that are potential candidates in Jacksonville are at 690 kHz and 1460 kHz. By the way, I don't recall having the BC IMD issue with the prior antenna preamps. Just an observation. Paul, W9AC _______________________________________________ Hi-zreceivingarraydiscussions mailing list Hi-zreceivingarraydiscussions at hizantennas.com http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_h izantennas.com _______________________________________________ Hi-zreceivingarraydiscussions mailing list Hi-zreceivingarraydiscussions at hizantennas.com http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_hizantennas.com _______________________________________________ Hi-zreceivingarraydiscussions mailing list Hi-zreceivingarraydiscussions at hizantennas.com http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_hizantennas.com From contact at hizantennas.com Wed Nov 11 16:08:54 2020 From: contact at hizantennas.com (contact at hizantennas.com) Date: Wed, 11 Nov 2020 13:08:54 -0800 Subject: [Hi-zreceivingarraydiscussions] BC IMD In-Reply-To: <009d01d6b868$b95281b0$2bf78510$@arrl.net> References: <004501d6b69d$c06ce110$4146a330$@arrl.net> <004601d6b69e$3e9ad1f0$bbd075d0$@arrl.net> <1611863329.4253164.1605106747463@mail.yahoo.com> <009d01d6b868$b95281b0$2bf78510$@arrl.net> Message-ID: <000201d6b86e$dda5c3f0$98f14bd0$@hizantennas.com> Awesome Paul, I was just setting here thinking I should email Paul and see how things were going. I really think that with the 8 circle with the improved accuracy of the V2Plus Hi-Z amps the 8 circle should work even better than it did before. It apparently does from your report. I suspect all my arrays will benefit in time. Glad to hear the IMD has not reappeared. I may use some of your words Paul in my testimonials if you don't mind. You made my day Paul!!! Lee K7TJR Hi-Z Antennas Yes. The 160m 8-circle worked great last night. For about three minutes, VU2GSM was an honest S7 on the K3 S meter. S5 about 10 minutes before and after the peak. Copy was from the NE as expected. No copy at all in the N and E directions. F/B from W1AW last night was better than 40 dB. S9 NE and nothing heard in the SW position. All switch positions are definitely working. This afternoon, N4CC and I just finished re-deploying radials for the "T" top transmit antenna. Sure wished it was ready yesterday! 100 ft vertical section and a flat T top that is between 80-100 ft. We could not remember the length as we discussed it today. I do want to validate 100 ft to ensure there's little or no interaction with the 40m Yagi. IMD update: clean for the last 48 hours. I did adjust the power supply current threshold on an HP lab supply and validated system voltages. Nothing conclusive though. We'll see how it goes. Paul, W9AC