Re: Topband: Antenna analysers in close proximity to BC station.
On 2012-11-03 8:25 PM, WO0W wrote: Perhaps you can take a portable transmitter and manual tuner to the site. At the point where you wish to place an L network, attach the manual tuner and transmitter and adjust the tuner for a good match. Take the tuner away from the source of interference, put a 50 Ohm dummy load on the tuner input, and measure the impedance on the tuner output with the MFJ-259B. I believe that should be close to the value of the impedance of the antenna that was measured, with little or no affect from the strong broadcast signal. In event the application you are using doesn't report the voltages on the L network components, the application, Transmission Lines for Windows, found on the CD with the late versions of the Antenna Book will present values for the L components and the voltage applied to each with a given input power. 73 de WOØW This is a great idea. But don't forget that the output Z of the terminated tuner will look like the conjugate of the antenna impedance. In other words, the sign of the reactance (if any) will be reversed. 73, Terry N6RY ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station
Thinking again about this, we have missed out a stage. After measuring the tuner output impedance, we need to make a temporary L network which, when terminated with 50 ohms, looks like the antenna. Now put the MFJ on this terminated network and measure it's R +/- jX values which will represent the antenna. Networks with loss are not always bilaterial. Since tuners have unevenly distributed losses, they are not bilaterial. If I adjust a typical tuner for 1:1 SWR into 50 ohms and reverse it, the new input impedance will not be 1:1 SWR. ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station
So, I'm looking at setting a EWE antenna up - what happens if I simply make it a full loop? In other words, instead of driving 4' ground rods in at both ends I run a wire between the bottom of the terminating resistor and the matching balun.I'm going to try the shorter version first - 10 feet up and 21 feet across so the full loop will be 62' of wire in that rectangular shape. Thank you, in advance, for any feedback and 72, Jim Rodenkirch K9JWV ___ Topband reflector - topband@contesting.com
Topband: Antenna analysers in close proximity to BC station
Hi topBanders! I live in an area about 10km away from a BC station that transmits on frequency 981khz and whose power is 200Kw. Whenever I had tried to take measurements with a 160m antenna- with the latest equipment on the market- it was always impossible. The equipment was always becoming an FSM. The addition of filters given for this kind of projects did nothing. However, I did manage to solve the problem once and for all by building a simple circuit with materials found in almost every shack's junkbox. The basic circuit was first introduced by W8CGD Measurement of R+jx in QST June 1965 and was gradually improved throughout time. I will refer to relative articles like the ones by G3HCT in Radcom, June 1979, G3LDO ARRL ANTENNA COMPENDIUM Vol 4, Vol 5 and lastly a wonderful project and its software by SV1BYO which was based on the method of Five-Meter Method and a Computer. The whole set up consists of a power source (in my case, Elecraft K2- 1Watt), a digital Voltmeter and a laptop on the base of my antenna. You insert the measurements of the Voltmeter in the appropriate program boxes and you immediately get the results on the measurements of R and jx of the antenna without any interference by the BC station. 73 Manolis, SV1AOZ ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station
Thanks, Tom - looks like running that bottom wire would be worth it 'cuz I have one 4' ground rod near where I want to install the EWE so that saves the cost of buying another rod...Hi Hi. Appreciate the quick response! 72, Jim Rodenkirch K9JWV From: w...@w8ji.com To: rodenkirch_...@msn.com; topband@contesting.com Date: Mon, 5 Nov 2012 08:19:12 -0500 Subject: Re: Topband: Antenna analysers in close proximity to BC station So, I'm looking at setting a EWE antenna up - what happens if I simply make it a full loop? In other words, instead of driving 4' ground rods in at both ends I run a wire between the bottom of the terminating resistor and the matching balun.I'm going to try the shorter version first - 10 feet up and 21 feet across so the full loop will be 62' of wire in that rectangular shape. All EWE's, Flags, Pennants, K9AY's, and everything else are just small terminated loops. They all act like a pair of short verticals that have the cross-fire feedline phasing integrated into the horizontal conductor distance, with the vertical drops actually being the desired antennas. You could run a wire across the bottom, except the antenna load and source are not symmetrically placed. This means you would have to ground the bottom wire to prevent the system from being negatively impacted by the asymmetrically of the load and source position. 73 Tom ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station
Tom: is there data that nail down the horizontal wire to vertical wire ratio? I see in that write up by wa1on mention of 2.25:1 h to v but...is that some rule that can't be violated or.../ For instance, assuming a vertical section height of 10' I could run a longer horizontal section but don't know if that gains me anything. Thoughts?? Jim R. K9JWV From: tsho...@wmata.com To: rodenkirch_...@msn.com Subject: RE: Topband: Antenna analysers in close proximity to BC station Date: Mon, 5 Nov 2012 14:02:58 + Sounds to me, like something very close to a flag or rectangular pennant antenna which would be fed from an end. E.g. http://www.qsl.net/wa1ion/flag/flag_antenna.htm But I also note that I found webpages calling your proposal an elevated ewe, without a ground rod and feeding in a lower corner. I've always had better results with the antennas on the ground with ground rods (e.g. K9AY). Not sure what I've done wrong whenever I tried the elevated flag/pennants but they did not work well for me. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of James Rodenkirch Sent: Monday, November 05, 2012 8:08 AM To: topband@contesting.com Subject: Re: Topband: Antenna analysers in close proximity to BC station So, I'm looking at setting a EWE antenna up - what happens if I simply make it a full loop? In other words, instead of driving 4' ground rods in at both ends I run a wire between the bottom of the terminating resistor and the matching balun.I'm going to try the shorter version first - 10 feet up and 21 feet across so the full loop will be 62' of wire in that rectangular shape. Thank you, in advance, for any feedback and 72, Jim Rodenkirch K9JWV ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Topband: Antenna analysers in close proximity to BC station
That's an interesting idea Red and worth a try. 73 Tom G3OLB WO0W wrote: Perhaps you can take a portable transmitter and manual tuner to the site. At the point where you wish to place an L network, attach the manual tuner and transmitter and adjust the tuner for a good match. Take the tuner away from the source of interference, put a 50 Ohm dummy load on the tuner input, and measure the impedance on the tuner output with the MFJ-259B. I believe that should be close to the value of the impedance of the antenna that was measured, with little or no affect from the strong broadcast signal. ___ Topband reflector - topband@contesting.com
Topband: Antenna analysers in close proximity to BC station
Thinking again about this, we have missed out a stage. After measuring the tuner output impedance, we need to make a temporary L network which, when terminated with 50 ohms, looks like the antenna. Now put the MFJ on this terminated network and measure it's R +/- jX values which will represent the antenna. 73 Tom G3OLB WO0W wrote: Perhaps you can take a portable transmitter and manual tuner to the site. At the point where you wish to place an L network, attach the manual tuner and transmitter and adjust the tuner for a good match. Take the tuner away from the source of interference, put a 50 Ohm dummy load on the tuner input, and measure the impedance on the tuner output with the MFJ-259B. I believe that should be close to the value of the impedance of the antenna that was measured, with little or no affect from the strong broadcast signal. ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
At my QTH, many of the local (just a few miles away) AM BC stations cut back power a lot at sunset. The cleanup is remarkable on my transmit Marconi. Before sunset and without any reject filters, I literally have 50V RMS between antenna and ground. It can light up a neon light on modulation peaks of the nearest stations (OK I cheated and built a tuned circuit for 630 WMAL to make that happen! But it does happen.) At night it clears up dramatically and is closer to 10V RMS. It may be as easy as waiting for sunset to do the antenna analyzer thing. (Not sure if this helps the original poster in the UK... don't know if UK/Euro stations have the same day/night switcheroo that NA stations coordinate. And I think clear channel stations do not cut back power at night... do clear channel stations actually still exist?). Tim N3QE From: Topband [topband-boun...@contesting.com] on behalf of ZR [z...@jeremy.mv.com] Sent: Friday, November 02, 2012 8:11 PM To: Tom Boucher; 160 reflector; Chris G3SVL Subject: Re: Topband: Antenna analysers in close proximity to BC station. MFJ sells a filter for that but I dont know how well it works around serious BCB RF; 10KW at the high end of the band in 2 directions in about 7-8 miles doesnt bother my unfiltered 259B nor do the FM and UHF TV sites about 2 miles away. Carl KM1H - Original Message - From: Chris G3SVL ch...@g3svl.com To: Tom Boucher t...@telemetry.demon.co.uk; 160 reflector topband@contesting.com Sent: Friday, November 02, 2012 6:42 PM Subject: Re: Topband: Antenna analysers in close proximity to BC station. At 21:21 02/11/2012, Tom Boucher wrote: .. but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? Hi Tom, I have 2.4KW of MW BC transmitter 300m from the base of my 160m antenna, so I know the problem. I've found an ICE BC filter to be pretty good - but I've only ever used it to tweak a matching system, not to take absolute readings. I've used a loaned N8LP LP100A and that worked fine - but of course that's an entirely different measurement system. 73 Chris, G3SVL ___ Topband reflector - topband@contesting.com - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1427 / Virus Database: 2441/5369 - Release Date: 11/02/12 ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
Tim N3QE wrote: And I think clear channel stations do not cut back power at night... do clear channel stations actually still exist? There are about 116 AM broadcast stations in the U.S. using 50 kW transmitter power during the day. Some of them reduce power at night, however KFMB (760 kHz) San Diego operates with 5 kW non-directional days, and 50 kW directional at night. Some of these 116 stations are directional day and night, and some of those have different patterns for day and night. The directional patterns used by some of these 116 stations may have an ERP of around 500 kW at the center of their major lobe. The stations using 50 kW non-directional day and night are: KFI 640 kHz Los Angeles WSM 650 Memphis WFAN 660 NYC WSCR 670 Chicago KNBR 680 San Francisco WLW 700 Cincinnati WGN 720 Chicago WSB 750 Atlanta WJR 760 Detroit WABC 770 NYC WBBM 780 Chicago WGY 810 Schenectady WBAP 820 Ft. Worth WCCO 830 Minneapolis WHAS 840 Louisville KOA 850 Denver WCBS 880 NYC WLS 890 Chicago KDKA 1020 Pittsburgh WHO 1040 Des Moines KNX 1070 Los Angeles WTAM 1100 Cleveland KMOX 1120 St. Louis KSL 1160 Salt Lake City WHAM 1180 Rochester WOAI 1200 San Antonio WPHT 1210 Philadelphia WBZ 1030 Boston and WWL 870 New Orleans use 50 kW day and night, but with directional arrays to favor radiation over land areas. A groundwave field intensity of 2.5 V/m or more can be present at a radius of 1 km from the stations in the above list. That can rise to more than 7 V/m in the main lobe of a directional station with 500 kW ERP. The original concept of a clear channel meaning that only one 50 kW, 24/7, non-directional station was authorized on that frequency at night is gone. The FCC has allowed nighttime service on all of them by stations located far enough away from those on the list above when using fairly low power (some less than 1 kW), and usually, directional arrays. The stations listed above are given protection to their nighttime (secondary) service areas for interference to their 0.5 mV/m-50% skywave contour from stations on the same channels. RF ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
-Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom Sent: Friday, November 02, 2012 5:21 PM Subject: Topband: Antenna analysers in close proximity to BC station. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? Tom, The problem with a low pass filter is it acts like a transmission line and matching network combination. Even if an analyzer allows calibrating out, results can be compromised. Results are useless if you cannot calibrate out. The MFJ filter is a parallel tuned network in parallel with a series tuned trap for the AM band. Because it corrects as an open circuit at the desired frequency, it has almost no effect on the reading on the setup frequency. The amount of null depth depends on the characteristics of the antenna system you have and the spacing of the BC station to the frequency you are measuring. Typically I'd expect 20 dB. If you change the trap inductor to a higher Q inductor it might get up to 30 dB. What won't work is a low pass, high pass, or band pass, unless it appears as an open with near-zero transmission line effect. This limits the type of filters that will work to something like the MFJ. The exception is a filter designed into the detector, or an analyzer and filter that can calibrate out and tell you what is happening on the other side of the filter. I've been telling MFJ for years they need to get an analyzer that uses selective detectors. IMO that would be more important than sweeps and all that other stuff. Most people probably just want to know the R and j accurately, and don't care about a computer interface. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
Hi, Tom; Perhaps you can take a portable transmitter and manual tuner to the site. At the point where you wish to place an L network, attach the manual tuner and transmitter and adjust the tuner for a good match. Take the tuner away from the source of interference, put a 50 Ohm dummy load on the tuner input, and measure the impedance on the tuner output with the MFJ-259B. I believe that should be close to the value of the impedance of the antenna that was measured, with little or no affect from the strong broadcast signal. In event the application you are using doesn't report the voltages on the L network components, the application, Transmission Lines for Windows, found on the CD with the late versions of the Antenna Book will present values for the L components and the voltage applied to each with a given input power. 73 de WOØW From: Tom Bouchert...@telemetry.demon.co.uk To: 160 reflectortopband@contesting.com Subject: Topband: Antenna analysers in close proximity to BC station. A ham friend asked me to design a matching network for his 160 metre end fed quarter wave, so I asked him to provide an impedance reading using his MFJ-259B. I would then use the Berkley site (http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.html ) to provide the necessary values for an 'L' network, as I have done many times at my own station. The readings he provided were total nonsense and quite erratic, so we concluded his MFJ-259B was dead. He assured me that he always does a static discharge before connecting the MFJ. So I paid him a visit, taking along my Palstar Antenna analyser thing, which has always performed well at home, and what-do-you-know, the readings on that were also erratic, total nonsense and it behaved in a way I have never seen before. Than someone suggested the problem may be due to a 50Kw BC station on 909 KHz, situated less than 5 miles away, causing both antenna analysers to misbehave. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? 73 Tom G3OLB ___ Topband reflector - topband@contesting.com
Topband: Antenna analysers in close proximity to BC station.
A ham friend asked me to design a matching network for his 160 metre end fed quarter wave, so I asked him to provide an impedance reading using his MFJ-259B. I would then use the Berkley site (http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.html ) to provide the necessary values for an 'L' network, as I have done many times at my own station. The readings he provided were total nonsense and quite erratic, so we concluded his MFJ-259B was dead. He assured me that he always does a static discharge before connecting the MFJ. So I paid him a visit, taking along my Palstar Antenna analyser thing, which has always performed well at home, and what-do-you-know, the readings on that were also erratic, total nonsense and it behaved in a way I have never seen before. Than someone suggested the problem may be due to a 50Kw BC station on 909 KHz, situated less than 5 miles away, causing both antenna analysers to misbehave. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? 73 Tom G3OLB ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
Tom, I will be interested to see what the solution(s) will be for the BC station interference. Wanted to thank for the reference to the impedance problem calculators. They are great! 73, Bob K6UJ On Nov 2, 2012, at 2:21 PM, Tom Boucher wrote: A ham friend asked me to design a matching network for his 160 metre end fed quarter wave, so I asked him to provide an impedance reading using his MFJ-259B. I would then use the Berkley site (http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.html ) to provide the necessary values for an 'L' network, as I have done many times at my own station. The readings he provided were total nonsense and quite erratic, so we concluded his MFJ-259B was dead. He assured me that he always does a static discharge before connecting the MFJ. So I paid him a visit, taking along my Palstar Antenna analyser thing, which has always performed well at home, and what-do-you-know, the readings on that were also erratic, total nonsense and it behaved in a way I have never seen before. Than someone suggested the problem may be due to a 50Kw BC station on 909 KHz, situated less than 5 miles away, causing both antenna analysers to misbehave. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? 73 Tom G3OLB ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
I have the same problem with a 50KW FM station a couple of miles away affecting my Palstar ZM-30. It is useable on the rig side of an antenna tuning unit, but most of my antennas are self resonate therefore the FM broadcast RF rides right into the bridge making it mostly worthless when directly attached to any antenna such as a dipole, vertical, yagi, etc. Sometimes I can get a useable reading if I turn the antenna 90 to the broadcast tower, but that only works with the rotatable antennas. Experiments with filtering using small value caps, small pi networks, a series FM trap, or ferrites have been unsuccessful. Any filter I put in front of the analyzer influences the reading substantially. BTW... this broadcast station also comes in on my frequency counter too, with no antenna attached. Please let the group know if any of you have come up with a transparent at ham frequencies inline filter. 73 Lloyd - N9LB -Original Message- From: Topband [mailto:topband-boun...@contesting.com]On Behalf Of Tom Boucher Sent: Friday, November 02, 2012 4:21 PM To: 160 reflector Subject: Topband: Antenna analysers in close proximity to BC station. A ham friend asked me to design a matching network for his 160 metre end fed quarter wave, so I asked him to provide an impedance reading using his MFJ-259B. I would then use the Berkley site (http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch. html ) to provide the necessary values for an 'L' network, as I have done many times at my own station. The readings he provided were total nonsense and quite erratic, so we concluded his MFJ-259B was dead. He assured me that he always does a static discharge before connecting the MFJ. So I paid him a visit, taking along my Palstar Antenna analyser thing, which has always performed well at home, and what-do-you-know, the readings on that were also erratic, total nonsense and it behaved in a way I have never seen before. Than someone suggested the problem may be due to a 50Kw BC station on 909 KHz, situated less than 5 miles away, causing both antenna analysers to misbehave. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? 73 Tom G3OLB ___ Topband reflector - topband@contesting.com No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.930 / Virus Database: 2441.1.1/5369 - Release Date: 11/02/12 02:34:00 ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
MFJ makes a filter for their Antenna analysers. I am sure that if it does not work for you, you can get your monies back. 73..Price W0RI I have the same problem with a 50KW FM station a couple of miles away affecting my Palstar ZM-30. It is useable on the rig side of an antenna tuning unit, but most of my antennas are self resonate therefore the FM broadcast RF rides right into the bridge making it mostly worthless when directly attached to any antenna such as a dipole, vertical, yagi, etc. Sometimes I can get a useable reading if I turn the antenna 90 to the broadcast tower, but that only works with the rotatable antennas. Experiments with filtering using small value caps, small pi networks, a series FM trap, or ferrites have been unsuccessful. Any filter I put in front of the analyzer influences the reading substantially. BTW... this broadcast station also comes in on my frequency counter too, with no antenna attached. Please let the group know if any of you have come up with a transparent at ham frequencies inline filter. 73 Lloyd - N9LB -Original Message- From: Topband [mailto:topband-boun...@contesting.com]On Behalf Of Tom Boucher Sent: Friday, November 02, 2012 4:21 PM To: 160 reflector Subject: Topband: Antenna analysers in close proximity to BC station. A ham friend asked me to design a matching network for his 160 metre end fed quarter wave, so I asked him to provide an impedance reading using his MFJ-259B. I would then use the Berkley site (http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch. html ) to provide the necessary values for an 'L' network, as I have done many times at my own station. The readings he provided were total nonsense and quite erratic, so we concluded his MFJ-259B was dead. He assured me that he always does a static discharge before connecting the MFJ. So I paid him a visit, taking along my Palstar Antenna analyser thing, which has always performed well at home, and what-do-you-know, the readings on that were also erratic, total nonsense and it behaved in a way I have never seen before. Than someone suggested the problem may be due to a 50Kw BC station on 909 KHz, situated less than 5 miles away, causing both antenna analysers to misbehave. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? 73 Tom G3OLB ___ Topband reflector - topband@contesting.com No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.930 / Virus Database: 2441.1.1/5369 - Release Date: 11/02/12 02:34:00 ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
Hi Tom, I used to have the same problem with my N2PK VNA, but then I put a switchable high pass filter in before the detector - after the reflection bridge that is. Provided that the VNA calibration is done with the filter switch in the same state as you intend to do the measurement, it has no effect on the readings at all. Don't know how easy it is to mess with the insides of the either the MFJ or Palstar, but if you can get at the detector the same solution should work. 73, Greg, ZL3IX On 2012-11-03 10:21 a.m., Tom Boucher wrote: A ham friend asked me to design a matching network for his 160 metre end fed quarter wave, so I asked him to provide an impedance reading using his MFJ-259B. I would then use the Berkley site (http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.html ) to provide the necessary values for an 'L' network, as I have done many times at my own station. The readings he provided were total nonsense and quite erratic, so we concluded his MFJ-259B was dead. He assured me that he always does a static discharge before connecting the MFJ. So I paid him a visit, taking along my Palstar Antenna analyser thing, which has always performed well at home, and what-do-you-know, the readings on that were also erratic, total nonsense and it behaved in a way I have never seen before. Than someone suggested the problem may be due to a 50Kw BC station on 909 KHz, situated less than 5 miles away, causing both antenna analysers to misbehave. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? 73 Tom G3OLB ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
At 21:21 02/11/2012, Tom Boucher wrote: .. but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? Hi Tom, I have 2.4KW of MW BC transmitter 300m from the base of my 160m antenna, so I know the problem. I've found an ICE BC filter to be pretty good - but I've only ever used it to tweak a matching system, not to take absolute readings. I've used a loaned N8LP LP100A and that worked fine - but of course that's an entirely different measurement system. 73 Chris, G3SVL ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
It is a common solution to put a 160 meter band pass filter on the SWR meter and it will work. I had to do this on both 160 meters and 80 meters at A73A. The high power AM station was miles away. Tree N6TR On Fri, Nov 2, 2012 at 3:22 PM, HAROLD SMITH JR w0ri...@sbcglobal.netwrote: MFJ makes a filter for their Antenna analysers. I am sure that if it does not work for you, you can get your monies back. 73..Price W0RI I have the same problem with a 50KW FM station a couple of miles away affecting my Palstar ZM-30. It is useable on the rig side of an antenna tuning unit, but most of my antennas are self resonate therefore the FM broadcast RF rides right into the bridge making it mostly worthless when directly attached to any antenna such as a dipole, vertical, yagi, etc. Sometimes I can get a useable reading if I turn the antenna 90 to the broadcast tower, but that only works with the rotatable antennas. Experiments with filtering using small value caps, small pi networks, a series FM trap, or ferrites have been unsuccessful. Any filter I put in front of the analyzer influences the reading substantially. BTW... this broadcast station also comes in on my frequency counter too, with no antenna attached. Please let the group know if any of you have come up with a transparent at ham frequencies inline filter. 73 Lloyd - N9LB -Original Message- From: Topband [mailto:topband-boun...@contesting.com]On Behalf Of Tom Boucher Sent: Friday, November 02, 2012 4:21 PM To: 160 reflector Subject: Topband: Antenna analysers in close proximity to BC station. A ham friend asked me to design a matching network for his 160 metre end fed quarter wave, so I asked him to provide an impedance reading using his MFJ-259B. I would then use the Berkley site ( http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch. htmlhttp://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.html) to provide the necessary values for an 'L' network, as I have done many times at my own station. The readings he provided were total nonsense and quite erratic, so we concluded his MFJ-259B was dead. He assured me that he always does a static discharge before connecting the MFJ. So I paid him a visit, taking along my Palstar Antenna analyser thing, which has always performed well at home, and what-do-you-know, the readings on that were also erratic, total nonsense and it behaved in a way I have never seen before. Than someone suggested the problem may be due to a 50Kw BC station on 909 KHz, situated less than 5 miles away, causing both antenna analysers to misbehave. We ended up with a good old-fashioned link coupled parallel tuned circuit with the antenna tapped a few turns up from the ground end. This works fine but he is power limited due to arcing across the tuning capacitor. So we would ideally like to revert to the 'L' network plan, but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? 73 Tom G3OLB ___ Topband reflector - topband@contesting.com No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.930 / Virus Database: 2441.1.1/5369 - Release Date: 11/02/12 02:34:00 ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Antenna analysers in close proximity to BC station.
MFJ sells a filter for that but I dont know how well it works around serious BCB RF; 10KW at the high end of the band in 2 directions in about 7-8 miles doesnt bother my unfiltered 259B nor do the FM and UHF TV sites about 2 miles away. Carl KM1H - Original Message - From: Chris G3SVL ch...@g3svl.com To: Tom Boucher t...@telemetry.demon.co.uk; 160 reflector topband@contesting.com Sent: Friday, November 02, 2012 6:42 PM Subject: Re: Topband: Antenna analysers in close proximity to BC station. At 21:21 02/11/2012, Tom Boucher wrote: .. but how to use the antenna analyser in the presence of a high BC station field. Anyone any ideas? Hi Tom, I have 2.4KW of MW BC transmitter 300m from the base of my 160m antenna, so I know the problem. I've found an ICE BC filter to be pretty good - but I've only ever used it to tweak a matching system, not to take absolute readings. I've used a loaned N8LP LP100A and that worked fine - but of course that's an entirely different measurement system. 73 Chris, G3SVL ___ Topband reflector - topband@contesting.com - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1427 / Virus Database: 2441/5369 - Release Date: 11/02/12 ___ Topband reflector - topband@contesting.com
