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" mailto: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-poi
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" mailto: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
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" mailto: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 wit
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&
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
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.