Re: Topband: Still in search of resonance - Detailed Observations and Calculations
Hi, Carl I did a bit of further investigation and work on your problem. I think you are done, as follows: 1.0 Just tap the Skyneedle at 90' and tune out the series inductive reactance with a variable capacitor, leaving you with 68 ohms real at the bottom of your drop wire. Great match! VSWR on 50 ohm feed cable of 1.4:1. 2.0 Now, let's assume you have 250 feet of Belden 8237 (RG-8) feeding the bottom of the drop wire. Losses are as follows: Top of Form Set Parameters as Desired Line Type: Line Length: Feet Meters Frequency: MHz Load SWR: : 1 Power In: W Bottom of Form Top of Form Results Matched Loss: dB SWR Loss: dB Total Loss: dB Power Out: W Bottom of Form Note that the excess loss due to the SWR on the cable is 0.029 dB, out of a total loss in 250 of RG-8 of 0.606 dB Note the flat-loss or matched loss of the cable (at 1:1 VSWR) is 0.577 dB. So theres no real point in struggling to get to exactly 50 ohms real at the bottom of your drop-wire to recover 0.029 dB of loss in 250 of cable! Your 68 ohms is just fine! Just match tle line at the transmitter end and accept the modest 1.4:1 VSWR at the load end. As you observed, when tapped at 90 the tower heard very well and you made some contacts with your FT-1000D barefoot. So, it surely appears that you have a very good, well-matched antenna when you tap at 90 and tune out the series inductance of the gamma match in the normal way using a series capacitor. Just tune for X=0 at th bottom of the drop wire, connect the feedline and match the feedline at the transmitter and enjoy!! Of course, with a tower that tall, you probably want a spark gap and/or a gas-tube at the feed-point and sopme sortof static bleed to defend agains static charge and lightning! GL! Have fun! 73. Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D
Re: Topband: Still in search of resonance - Detailed Observations and Calculations
Sorry, Carl! My loss tables didn't translate from HTML to the reflector. I'll re-build the tables manually and re-send this message! Sorry! Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Charlie Cunningham Sent: Saturday, February 15, 2014 11:35 AM To: 'Carl Braun'; '160' Subject: Re: Topband: Still in search of resonance - Detailed Observations and Calculations Hi, Carl I did a bit of further investigation and work on your problem. I think you are done, as follows: 1.0 Just tap the Skyneedle at 90' and tune out the series inductive reactance with a variable capacitor, leaving you with 68 ohms real at the bottom of your drop wire. Great match! VSWR on 50 ohm feed cable of 1.4:1. 2.0 Now, let's assume you have 250 feet of Belden 8237 (RG-8) feeding the bottom of the drop wire. Losses are as follows: Top of Form Set Parameters as Desired Line Type: Line Length: Feet Meters Frequency: MHz Load SWR: : 1 Power In: W Bottom of Form Top of Form Results Matched Loss: dB SWR Loss: dB Total Loss: dB Power Out: W Bottom of Form Note that the excess loss due to the SWR on the cable is 0.029 dB, out of a total loss in 250 of RG-8 of 0.606 dB Note the flat-loss or matched loss of the cable (at 1:1 VSWR) is 0.577 dB. So theres no real point in struggling to get to exactly 50 ohms real at the bottom of your drop-wire to recover 0.029 dB of loss in 250 of cable! Your 68 ohms is just fine! Just match tle line at the transmitter end and accept the modest 1.4:1 VSWR at the load end. As you observed, when tapped at 90 the tower heard very well and you made some contacts with your FT-1000D barefoot. So, it surely appears that you have a very good, well-matched antenna when you tap at 90 and tune out the series inductance of the gamma match in the normal way using a series capacitor. Just tune for X=0 at th bottom of the drop wire, connect the feedline and match the feedline at the transmitter and enjoy!! Of course, with a tower that tall, you probably want a spark gap and/or a gas-tube at the feed-point and sopme sortof static bleed to defend agains static charge and lightning! GL! Have fun! 73. Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band
Re: Topband: Still in search of resonance - Detailed Observations and Calculations
Hi, Jim Well, Maxwell's W2DU balu ns are ferrite sleeve baluns and you can get those that go down to 160m. It's a matter of choosine the right ferrite for the frequenc;y range of interest, and using enough ferrite to build p the common-mode impedance! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Charlie Cunningham Sent: Saturday, February 15, 2014 11:45 AM To: 'Carl Braun'; '160' Subject: Re: Topband: Still in search of resonance - Detailed Observations and Calculations Sorry, Carl! My loss tables didn't translate from HTML to the reflector. I'll re-build the tables manually and re-send this message! Sorry! Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Charlie Cunningham Sent: Saturday, February 15, 2014 11:35 AM To: 'Carl Braun'; '160' Subject: Re: Topband: Still in search of resonance - Detailed Observations and Calculations Hi, Carl I did a bit of further investigation and work on your problem. I think you are done, as follows: 1.0 Just tap the Skyneedle at 90' and tune out the series inductive reactance with a variable capacitor, leaving you with 68 ohms real at the bottom of your drop wire. Great match! VSWR on 50 ohm feed cable of 1.4:1. 2.0 Now, let's assume you have 250 feet of Belden 8237 (RG-8) feeding the bottom of the drop wire. Losses are as follows: Top of Form Set Parameters as Desired Line Type: Line Length: Feet Meters Frequency: MHz Load SWR: : 1 Power In: W Bottom of Form Top of Form Results Matched Loss: dB SWR Loss: dB Total Loss: dB Power Out: W Bottom of Form Note that the excess loss due to the SWR on the cable is 0.029 dB, out of a total loss in 250 of RG-8 of 0.606 dB Note the flat-loss or matched loss of the cable (at 1:1 VSWR) is 0.577 dB. So theres no real point in struggling to get to exactly 50 ohms real at the bottom of your drop-wire to recover 0.029 dB of loss in 250 of cable! Your 68 ohms is just fine! Just match tle line at the transmitter end and accept the modest 1.4:1 VSWR at the load end. As you observed, when tapped at 90 the tower heard very well and you made some contacts with your FT-1000D barefoot. So, it surely appears that you have a very good, well-matched antenna when you tap at 90 and tune out the series inductance of the gamma match in the normal way using a series capacitor. Just tune for X=0 at th bottom of the drop wire, connect the feedline and match the feedline at the transmitter and enjoy!! Of course, with a tower that tall, you probably want a spark gap and/or a gas-tube at the feed-point and sopme sortof static bleed to defend agains static charge and lightning! GL! Have fun! 73. Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36
Re: Topband: Still in search of resonance - Detailed Observations and Calculations
Charlie Thank you for your work and insight. It appears I've I may have provided some incorrect info. When I tapped the tower at 90' I used the 160pf variable cap to get down to the 68 ohm impedance measurement and, yes, it heard well with what appeared to be a peak at approx 1770kc I never transmitted there. I've only transmitted with the system when I had a tap at 46' where I saw 24 ohms and X=0 with the variable. Ap on series. Then I installed a 22 to 50 ohm Unun and made the contacts to east coast stations. I believe I have plenty of capacitance on hand if I tap the tower at 90' but given the 68 ohm reading at 90' with the variable cap and the 24 ohm reading at 46' with the variable cap don't you think the best bet would be my 67' tap point? Even if it's still a bit low in resistance at that point i could add a bit of parallel C in conjunction with the series C to bring the antenna to 50 ohms+j0? Please advise and thank you for the most enjoyable technical conversation. Carl AG6X Sent from my iPhone On Feb 15, 2014, at 9:14 AM, Charlie Cunningham charlie-cunning...@nc.rr.commailto:charlie-cunning...@nc.rr.com wrote: Well, here it is with the re-built loss table, Carl 73, Charlie, K4OTV From: Charlie Cunningham [mailto:charlie-cunning...@nc.rr.com] Sent: Saturday, February 15, 2014 11:35 AM To: 'Carl Braun'; '160' Subject: RE: Topband: Still in search of resonance - Detailed Observations and Calculations Hi, Carl I did a bit of further investigation and work on your problem. I think you are done, as follows: 1.0 Just tap the Skyneedle at 90' and tune out the series inductive reactance with a variable capacitor, leaving you with 68 ohms real at the bottom of your drop wire. Great match! VSWR on 50 ohm feed cable of 1.4:1. 2.0 Now, let's assume you have 250 feet of Belden 8237 (RG-8) feeding the bottom of the drop wire. Losses are as follows: Line/Load Line type:Belden 8237 RG8 Line length 250’ Frequency 1.8 MHz Load SWR1.4:1 Power In 100W Results: Matched Loss: 0.577 dB SWR Loss 0.029 dB Total Loss0.606 dB Power Out 86.982 W Note that the excess loss due to the SWR on the cable is 0.029 dB, out of a total loss in 250’ of RG-8 of 0.606 dB Note the “flat-loss” or “matched loss” of the cable (at 1:1 VSWR) is 0.577 dB. So there’s no real point in struggling to get to exactly 50 ohms real at the bottom of your drop-wire to recover 0.029 dB of loss in 250’ of cable! Your 68 ohms is just fine! Just match tle line at the transmitter end and accept the modest 1.4:1 VSWR at the load end. As you observed, when tapped at 90’ the tower “heard” very well and you made some contacts with your FT-1000D barefoot. So, it surely appears that you have a very good, well-matched antenna when you “tap” at 90’ and tune out the series inductance of the gamma match in the normal way using a series capacitor. Just tune for X=0 at th bottom of the drop wire, connect the feedline and match the feedline at the transmitter and enjoy!! Of course, with a tower that tall, you probably want a “spark gap” and/or a gas-tube at the feed-point and sopme sortof static bleed to defend agains static charge and lightning! GL! Have fun! 73. Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial
Re: Topband: Still in search of resonance - Detailed Observations and Calculations
Charlie FYI. I'm using 60' to 70' of LMR400 from my panel at the base of the needle to the shack. No long runs here. Carl AG6X Sent from my iPhone On Feb 15, 2014, at 9:14 AM, Charlie Cunningham charlie-cunning...@nc.rr.commailto:charlie-cunning...@nc.rr.com wrote: Well, here it is with the re-built loss table, Carl 73, Charlie, K4OTV From: Charlie Cunningham [mailto:charlie-cunning...@nc.rr.com] Sent: Saturday, February 15, 2014 11:35 AM To: 'Carl Braun'; '160' Subject: RE: Topband: Still in search of resonance - Detailed Observations and Calculations Hi, Carl I did a bit of further investigation and work on your problem. I think you are done, as follows: 1.0 Just tap the Skyneedle at 90' and tune out the series inductive reactance with a variable capacitor, leaving you with 68 ohms real at the bottom of your drop wire. Great match! VSWR on 50 ohm feed cable of 1.4:1. 2.0 Now, let's assume you have 250 feet of Belden 8237 (RG-8) feeding the bottom of the drop wire. Losses are as follows: Line/Load Line type:Belden 8237 RG8 Line length 250’ Frequency 1.8 MHz Load SWR1.4:1 Power In 100W Results: Matched Loss: 0.577 dB SWR Loss 0.029 dB Total Loss0.606 dB Power Out 86.982 W Note that the excess loss due to the SWR on the cable is 0.029 dB, out of a total loss in 250’ of RG-8 of 0.606 dB Note the “flat-loss” or “matched loss” of the cable (at 1:1 VSWR) is 0.577 dB. So there’s no real point in struggling to get to exactly 50 ohms real at the bottom of your drop-wire to recover 0.029 dB of loss in 250’ of cable! Your 68 ohms is just fine! Just match tle line at the transmitter end and accept the modest 1.4:1 VSWR at the load end. As you observed, when tapped at 90’ the tower “heard” very well and you made some contacts with your FT-1000D barefoot. So, it surely appears that you have a very good, well-matched antenna when you “tap” at 90’ and tune out the series inductance of the gamma match in the normal way using a series capacitor. Just tune for X=0 at th bottom of the drop wire, connect the feedline and match the feedline at the transmitter and enjoy!! Of course, with a tower that tall, you probably want a “spark gap” and/or a gas-tube at the feed-point and sopme sortof static bleed to defend agains static charge and lightning! GL! Have fun! 73. Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find
Re: Topband: Still in search of resonance - Detailed Observations and Calculations
Thanks, Carl! Well, if you' heard a RX peak at 1770 KHz, it seems that you are awfully close! Just needs a little careful tweaking I would think. (I ass'ume that you are probably shootinf for something around 1830 KHz. BTW - the higher you tap on the tower, the smaller the series capacitor needs to be, since the increasing series inductive reactance will require increasing capacitive reactance (lower C) to cancel it, so it sounds like you can use the 160 pF capacitor for your series tuning C. I haven't used my MFJ 259 in a while, so I would need to get it out and review its operation but when you tuned down to 68 ohms impedance whtn tapped at 90', I expect that's where the impedance became pure real at 68 ohms. As an additional check you can drive the gamma wire with a little power from your TX or the MFJ and tune the series capacitor for minimum SWR. Sounds like it should come in around 1.4. If it does, you're done. Just bolt everything down and enjoy. Clearly, if the 46' tap pointis showing24 ohms real that's way too low on the tower for your tap point! It sound like90]isprobably the point you want! GL, Carl! Have fun! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Saturday, February 15, 2014 3:11 PM To: Charlie Cunningham Cc: topband@contesting.com Subject: Re: Topband: Still in search of resonance - Detailed Observations and Calculations Charlie Thank you for your work and insight. It appears I've I may have provided some incorrect info. When I tapped the tower at 90' I used the 160pf variable cap to get down to the 68 ohm impedance measurement and, yes, it heard well with what appeared to be a peak at approx 1770kc I never transmitted there. I've only transmitted with the system when I had a tap at 46' where I saw 24 ohms and X=0 with the variable. Ap on series. Then I installed a 22 to 50 ohm Unun and made the contacts to east coast stations. I believe I have plenty of capacitance on hand if I tap the tower at 90' but given the 68 ohm reading at 90' with the variable cap and the 24 ohm reading at 46' with the variable cap don't you think the best bet would be my 67' tap point? Even if it's still a bit low in resistance at that point i could add a bit of parallel C in conjunction with the series C to bring the antenna to 50 ohms+j0? Please advise and thank you for the most enjoyable technical conversation. Carl AG6X Sent from my iPhone On Feb 15, 2014, at 9:14 AM, Charlie Cunningham charlie-cunning...@nc.rr.commailto:charlie-cunning...@nc.rr.com wrote: Well, here it is with the re-built loss table, Carl 73, Charlie, K4OTV From: Charlie Cunningham [mailto:charlie-cunning...@nc.rr.com] Sent: Saturday, February 15, 2014 11:35 AM To: 'Carl Braun'; '160' Subject: RE: Topband: Still in search of resonance - Detailed Observations and Calculations Hi, Carl I did a bit of further investigation and work on your problem. I think you are done, as follows: 1.0 Just tap the Skyneedle at 90' and tune out the series inductive reactance with a variable capacitor, leaving you with 68 ohms real at the bottom of your drop wire. Great match! VSWR on 50 ohm feed cable of 1.4:1. 2.0 Now, let's assume you have 250 feet of Belden 8237 (RG-8) feeding the bottom of the drop wire. Losses are as follows: Line/Load Line type:Belden 8237 RG8 Line length 250 Frequency 1.8 MHz Load SWR1.4:1 Power In 100W Results: Matched Loss: 0.577 dB SWR Loss 0.029 dB Total Loss0.606 dB Power Out 86.982 W Note that the excess loss due to the SWR on the cable is 0.029 dB, out of a total loss in 250 of RG-8 of 0.606 dB Note the flat-loss or matched loss of the cable (at 1:1 VSWR) is 0.577 dB. So theres no real point in struggling to get to exactly 50 ohms real at the bottom of your drop-wire to recover 0.029 dB of loss in 250 of cable! Your 68 ohms is just fine! Just match tle line at the transmitter end and accept the modest 1.4:1 VSWR at the load end. As you observed, when tapped at 90 the tower heard very well and you made some contacts with your FT-1000D barefoot. So, it surely appears that you have a very good, well-matched antenna when you tap at 90 and tune out the series inductance of the gamma match in the normal way using a series capacitor. Just tune for X=0 at th bottom of the drop wire, connect the feedline and match the feedline at the transmitter and enjoy!! Of course, with a tower that tall, you probably want a spark gap and/or a gas-tube at the feed-point and sopme sortof static bleed to defend agains static charge and lightning! GL! Have fun! 73. Charlie, K4OTV
Re: Topband: Still in search of resonance
Tom After reading your post yesterday I had a dream that I woke up and saw one of those flying monkeys on top of my tower laughing and sawing away. Carl AG6X -Original Message- From: Tom W8JI [mailto:w...@w8ji.com] Sent: Friday, February 14, 2014 6:02 PM To: Carl Braun; '160' Subject: Re: Topband: Still in search of resonance Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Hee! -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Saturday, February 15, 2014 3:53 PM To: Tom W8JI; '160' Subject: Re: Topband: Still in search of resonance Tom After reading your post yesterday I had a dream that I woke up and saw one of those flying monkeys on top of my tower laughing and sawing away. Carl AG6X -Original Message- From: Tom W8JI [mailto:w...@w8ji.com] Sent: Friday, February 14, 2014 6:02 PM To: Carl Braun; '160' Subject: Re: Topband: Still in search of resonance Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Still in search of resonance
List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Sorry Carl, I hit the send button before responding..Now. I believe that first #14 wire is a bit small. I do not believe that you will find a 50ohmZ and X=0 point. I have 80ft of Rohn 45G with a Telrex 20M546 at 80ft, 3el on 15 at 90 and 3el on 10 at 100ft. I shunt feed the tower for 160 with a tap at 35ft using 1/2 EMT Conduit. At the end of the shunt rod I have a 500pf Vacuum Variable to the tower base and a 500pf Vacuum in series from the shunt rod to the Coax. I can and did tune the Vacuum Caps to VSWR 1:1 at 1830kHz. I did this in 1991 and it gets out very well. It hears good but my noise is over S9 with it. DXCC on 160 is 192 cmfd. 73 de Price W0RI near St. Louis List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Is the single 14AWG too thin causing goofy readings? Absolutely! Treating the Sky Needle and the #12 wire as a folded dipole and using 8 for the diameter of the tower, you have a 16:1 step-up with the single #14 wire. If you made a cage of 4 or 6 wires with a 6 to 8 diameter, back of the envelope calculations say the impedance with the 67' tap point would be much closer to 50 Ohms *and* the bandwidth would be much wider. Even three parallel wires spaced 12 or so would have a much greater effective diameter and would reduce the step-up you see by a great deal. Of course, if all you can do is a single #14 wire, use an Omega match or an L-network to bring the impedance down to 50 Ohms. 73, ... Joe, W4TV On 2/14/2014 6:14 PM, Carl Braun wrote: List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Thanks Dean The one I'm looking at is the old heathkit with the various coil plug ins. The kit comes with a coil that goes down to 1.600. Is there another one you can recommend that may go down further? ON4UN says my tower should be close to 115 degrees others say closer to 140 degrees Thanks for your input. I agree with you wholeheartedly. Carl AG6X Sent from my iPhone On Feb 14, 2014, at 3:32 PM, dospi...@q.com dospi...@q.com wrote: Hello Carl: My suggestion is the same as the first time you were on about this. Obtain... beg borrow steal or buy a meter that will read down into the BC band. You NEED to know where it is resonant.. All the esoteric nonsense about resistance and reactance are meaningless unless you know the frequencies at which the readings are obtained! You might find the damn thing is 1:1 at 1356 kc.. At this point you are shooting in the dark in a dark room.. You may or may not have an adequate ground system, but that doesn't lessen the need to know what it is you have... and you don't. 73 GL Dean W5PJR Tijeras, NM - Original Message - From: Carl Braun carl.br...@lairdtech.com To: 160 topband@contesting.com Sent: Friday, February 14, 2014 4:14:42 PM Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
There seems to be some confusion, Carl! First of all, since the gamma match (regardless of the diameter of the gamma rod) is a shorted transmission line, less than 1/4 wavelength it WILL have series inductive reactance that you will need to tune out with a series variable capacitance. Second, I don't understand the R readings that you are reporting at various tap points with the MFJ, that come down when you apply the series C. That suggests to me that what you are reporting as R is R+jX or [R+jX], and it's coming down as you tune out the series reactance jX. If you find a tap point that results in 50 ohms real when you use the series-C to make X=0, that IS the 50 ohm tap point that you are looking for. You will NOT find a point that gives you 50 ohms real without the series C to tune out the inductive reactance, Other opinions notwithstanding, you CAN do the gamma match with 14 ga. wire, The only effect of using a thin gamma rod or gamma wire is to increase the losses a bit in the gamma, and to increase the inductance per unit length of the gamma. Finally, take care. That you don't have enough broadcast signal on the Sky needle to screw up the MFJ readings. ON additional note: In some cases guys use a shorter gamma that resultsn in a resistive real part LESS than 50 ohms. In this case only a portion of the series inductance is cancelled with the series C and theremainin inductive reactance is used in conjunction with a shunt variable C to form an L-network to match the real part UP to 50 ohms! Sounds like you are hitting all around it, Carl. Just remember that what you are searching for is R=50, and X=0, or R+jX = 50 + j0. GL! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband
Re: Topband: Still in search of resonance
Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance - BTW Resonance
Well, of course not, Tom! I need to be more precise and keep in mind the audience on this Reflector, and that you are always lurking out there in the weeds to chide and chastise me! Of course devices that are pure real over the frequency range of interest would not be resonant! I guess I was thinking of the more general case.like Carl's gamma match whose impedance would consist of a real and imaginary part, in which case I stand by my assertion. Touche! Mea culpa! -Original Message- From: Tom W8JI [mailto:w...@w8ji.com] Sent: Friday, February 14, 2014 9:10 PM To: Charlie Cunningham; 'Carl Braun'; 'Joe Subich, W4TV' Cc: topband@contesting.com Subject: Re: Topband: Still in search of resonance - BTW Resonance Subject: Re: Topband: Still in search of resonance - BTW Resonance BTW Resonance = X=0 or jX = j0 So my dummy load is resonant, and the resistors in my resistor bins are all resonant? :-) _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance - BTW - Update!
By the way, Carl, you indicated that whe you were tapped at 90', the real part was 60 ohms when you tuned ou't the series reactance with th;e series capacitor!! Gee!! That ain't a bad match!! Should result in about 1.2:1 VSWR when fed with 50 ohm cable!! Not bad at all and certainly not enough VSWR to cause any significant excess loss (over flat-loss) even on a very long run of coax feeding the gamma match!! You were essentially done at that point and you should have just stopped there and bolted everything down!! You could probably find the 50 ohm j0 tap point somewhere below 90 ' , but if those are the only four tap points that are available, then 90' is the one that you want! The 14 ga wire isn't causing goofy readings and your radial field is probably OK as well! (operator head-spacing problem??) GL - move the tap back to 90' and be done! And you can't do a gamma match to shunt feed that tower without a series-c in the gamma arm! No way! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 6:15 PM To: '160' Subject: Topband: Still in search of resonance List Some of you may have followed my efforts in trying to shunt feed my 90' Tri-Ex Skyneedle with 20 meter yagi at 93'. I'm still unable to find any sort of resonance point on the tower. To refresh everyone's memory here are the specifics: 90' Skyneedle that is 12 round at the base and 4 round at the top 13' of mast out the top 5 element Telrex 20M monobander mounted at the 93' level. No other antennas on the tower 1 ½ copper pipe as a radial ring that surrounds the concrete base that measures 4' x 8' rectangle. Three 8' ground rods are connected to the radial ring via 1 copper strap that is .125 thick. Currently I have 27 14AWG insulated wire radials. Most of the radials are 20' to 50' long with three at 90 to 120' long and four of them connected to my 40M vertical array which have 100 count radials 50' to 100' each. The tower is grounded to each ground rod via 1 copper strap .125 thick and, as mentioned above, the ground rods are connected to the radial ring with the same strap with copper clad stainless screws. When I bolted the gamma arm to the tower at the 90' height I dropped a single 14AWG wire to the ground where my FLUKE meter read ZERO ohms between the radial ring and the end of the gamma wire with no fluctuations so I'm confident that I have good continuity throughout the tower. Here are the readings that I saw on the MFJ analyzer with the gamma arm mounted at the (4) points on the tower that are available... With the gamma arm mounted at 90' and 36 spacing I saw 425 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 67' and 36 spacing I saw 380 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 46' and 36 spacing I saw 240 ohms at the end of the drop wire on the MFJ With the gamma arm mounted at 28' and 36 spacing I saw 120 ohms at the end of the drop wire on the MFJ At all of these points I was able to knock down the R with my honkin' 1050pf cap to some resonance sort of resonance at 1.825 MHz but, as most everyone has indicated, I should be able to find a 50 ohm tap somewhere on the tower. I can't find it. When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower. Is my radial field so poor that I'm seeing these goofy readings? Is the single 14AWG too thin causing goofy readings? I'm back to scratching my head. Comments from the list? Carl AG6X _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance
Tom and all Thanks for the responses. I was under the assumption that I would find a 50 ohm tap on the tower but with a lot of reactance requiring a cap that would tune out the X but leave the 50 ohm resistive value in place. I knew my tap was too low at 46' when I saw less than 50 ohms with the variable cap in place. Same thing when I tapped the tower at 90' and I saw the lowest R at 68 ohms with the 160pf only partially meshed. With all of the information presented in this thread it appears my best bet is to tap the tower at the 67' level while playing with the larger (1050pf) variable in series to see what my results are. I have never used the larger cap with the tap at 90' or 67'...only the smaller 160pf variable. More experimentation tomorrow if I don't burn out the Skyneedle motor with all the up and down. Thanks and details to follow. Carl AG6X Sent from my iPhone On Feb 14, 2014, at 6:01 PM, Tom W8JI w...@w8ji.com wrote: Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Still in search of resonance Update 2
Well, if those 4 discrete tap points are the only ones that you have available, Carl, you likely won't find one that give that gives you 50 ohms real. So the best that you can do is pick the one that falls closest to 50 ohms real when you tune out the series inductive reactance with the capacitor. Even if the 90' point gives you 68 ohms real, that's not too bad - about 1.4:1 VSWR. If the 67' tap gives you less than 50 ohms real, you could add a shunt C back to GND at the base of the tower the and readjust the series C to only cancel a portion of the inductive reactance, leaving the remainder to work against the shunt C to form an L-network to transform the real part up to 50 ohms. By alternating back and forth adjusting the series and shunt capacitors, you should be able to bring the feedpoint VSWR to 1:1. Note that whatever the tap point, if the real part of the impedance is LESS than 50 ohms, a shunt C will be required. GL, 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Braun Sent: Friday, February 14, 2014 11:52 PM To: Tom W8JI Cc: 160 Subject: Re: Topband: Still in search of resonance Tom and all Thanks for the responses. I was under the assumption that I would find a 50 ohm tap on the tower but with a lot of reactance requiring a cap that would tune out the X but leave the 50 ohm resistive value in place. I knew my tap was too low at 46' when I saw less than 50 ohms with the variable cap in place. Same thing when I tapped the tower at 90' and I saw the lowest R at 68 ohms with the 160pf only partially meshed. With all of the information presented in this thread it appears my best bet is to tap the tower at the 67' level while playing with the larger (1050pf) variable in series to see what my results are. I have never used the larger cap with the tap at 90' or 67'...only the smaller 160pf variable. More experimentation tomorrow if I don't burn out the Skyneedle motor with all the up and down. Thanks and details to follow. Carl AG6X Sent from my iPhone On Feb 14, 2014, at 6:01 PM, Tom W8JI w...@w8ji.com wrote: Hi Carl, It sounds like you are trying to find 50 ohms on the tower without any series capacitor by looking at R and X. I would not try to do that. The reactance puts you out of range on the MFJ bridge. You are down to a few bits difference between data points the PIC needs in the MFJ. Look at this below. You said: seen at the other levels too as long as I brought the R down with a variable cap. Yesterday, with the gamma arm at the 46' level (and 240 ohms on the MFJ) I was able to put the big variable inline to bring the reading to 24 ohms with a TRUE X=0. With a 22 ohm to 50 ohm UNUN, I saw 1.3:1 Vswr on the output of the UNUN. I worked a W2 in NJ and a W4 in Florida with just the 1000D. BUT...again...I'm bringing the R down with the capacitor...not finding 50 ohms anywhere on the tower Stop trying to find 50 ohms without the capacitor! Right now at 46 ft you were at 24 ohms with the capacitor. That should tell you and everyone on this reflector :-) that you are tapped too low now! Let's look at this in simple terms. Here is what you said: When I had the gamma arm mounted at the 90' level. I was able to put my baby variable 160pf inline to bring the 425 ohm impedance down to about 60 ohms and the antenna heard very well; especially on the 1700 KHz broadcast band, with a 2.4:1 Vswr. Similar results could be seen at the other levels too as long as I brought the R down with a variable cap. That is NORMAL. You will always need the capacitor. Always. The only way to eliminate the capacitor is to saw your Yagi antenna off the tower so the tower moves above 2 MHz. Then you will probably find a 50j0 tap without any capacitor. You also might use a large skirt, but why?? Just use a capacitor!!! If you are trying to eliminate the capacitor, you will have a lot of work to do. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
