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#1
December 19th 07, 02:15 AM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun IsToo Expensive
RHF wrote:
The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website : http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - - MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...e40978fdc32ac0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...7d380609eec592 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF . [D]iane, The point is to keep the feedpoint Z below the transmission line Z. You're welcome. |
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#2
December 19th 07, 02:32 AM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive
In article ,
David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website : http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - - MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...e40978fdc32ac0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...7d380609eec592 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF . [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? -- Telamon Ventura, California |
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#3
December 23rd 07, 04:36 AM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive
In article
, Telamon wrote: In article , David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website : http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - - MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...e40978fdc32ac0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...7d380609eec592 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF . [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? OK I'll answer it. None. -- Telamon Ventura, California |
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#4
December 23rd 07, 02:02 PM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun IsToo Expensive
Telamon wrote:
In article , Telamon wrote: In article , David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website : http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - - MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...e40978fdc32ac0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...7d380609eec592 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF . [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? OK I'll answer it. None. Less pinching in the midriff... There's a rule. |
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#5
December 23rd 07, 09:27 PM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive
In article ,
David wrote: Telamon wrote: In article , Telamon wrote: In article , David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website : http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - - MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...e40978fdc32ac0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...7d380609eec592 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF . [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? OK I'll answer it. None. Less pinching in the midriff... There's a rule. OK here is the rule, when you have an impedance mismatch by some ratio it does not matter which system element is higher or lower so for example if the coax transmission line is 50 ohms and the antenna impedance is 25 or 75 ohms the result is the same amount of reflected power. 25 ohms and 75 ohms are equivalent in this regard. One is not a better situation than the other. Take an extreme case of this where you have either a short or the coax is open with nothing connected on that end. In either case if you were to send RF power to the open or short end of the cable you would have 100% reflected power. The returned phase of the that power would be 90 degrees different though. This is different situation then DC current where the open and short would have very different consequences. -- Telamon Ventura, California |
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#6
December 24th 07, 01:37 AM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is TooExpensive
On Dec 23, 1:27*pm, Telamon
wrote: In article , *David wrote: Telamon wrote: In article , *Telamon wrote: In article , *David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website :http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - *- MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...e40978fdc32ac0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...7d380609eec592 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF *. [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? OK I'll answer it. None. Less pinching in the midriff... There's a rule. ? OK here is the rule, when you have an impedance mismatch ? by some ratio it does not matter which system element is ? higher or lower so for example if the coax transmission ? line is 50 ohms and the antenna impedance is 25 or 75 ohms ? the result is the same amount of reflected power. ? 25 ohms and 75 ohms are equivalent in this regard. ? One is not a better situation than the other. Telamon, Wouldn't it be the Ratios : 25 Ù Antenna to 50 Ù Coax ~ 1 : 2 50 Ù Coax to 100 Ù Antenna ~ 1 : 2 -vice- 50 Ù Coax to 75 Ù Antenna ~ 2 : 3 (1 : 1.5) ~ RHF - Take an extreme case of this where you have either a short - or the coax is open with nothing connected on that end. - In either case if you were to send RF power to the open - or short end of the cable you would have 100% reflected - power. The returned phase of the that power would be 90 - degrees different though. - - This is different situation then DC current where the open - and short would have very different consequences. - - -- - Telamon - Ventura, California |
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#7
December 24th 07, 11:13 PM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive
In article ,
David wrote: RHF wrote: On Dec 23, 1:27 pm, Telamon wrote: In article , David wrote: Telamon wrote: In article , Telamon wrote: In article , David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website :http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - - MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...7e40978fdc32ac 0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...77d380609eec59 2 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF . [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? OK I'll answer it. None. Less pinching in the midriff... There's a rule. ? OK here is the rule, when you have an impedance mismatch ? by some ratio it does not matter which system element is ? higher or lower so for example if the coax transmission ? line is 50 ohms and the antenna impedance is 25 or 75 ohms ? the result is the same amount of reflected power. ? 25 ohms and 75 ohms are equivalent in this regard. ? One is not a better situation than the other. Telamon, Wouldn't it be the Ratios : 25 Ù Antenna to 50 Ù Coax ~ 1 : 2 50 Ù Coax to 100 Ù Antenna ~ 1 : 2 -vice- 50 Ù Coax to 75 Ù Antenna ~ 2 : 3 (1 : 1.5) ~ RHF - Take an extreme case of this where you have either a short - or the coax is open with nothing connected on that end. - In either case if you were to send RF power to the open - or short end of the cable you would have 100% reflected - power. The returned phase of the that power would be 90 - degrees different though. - - This is different situation then DC current where the open - and short would have very different consequences. Low goes into high better than high goes into low. Reflected power does no harm in a receive antenna. Try using your 300 Ohm antenna with a 50 Ohm transmission line. Then try using a 50 Ohm antenna with a 300 Ohm transmission line. Which will receive better? Neither will be better. If you don't understand this look up VSWR and study that topic. Of course there is not enough power to hurt any part of a receive antenna or transmission line but it harms your reception. When it comes to RF all that matters is whether two components match and if they don't how far apart they are in impedance. It does not matter which is higher than the other; the results will be the same reflected power. It's a simple rule that applies to many a physics problem not just antennas and transmission lines such as light through a prism or light passing from air to water. -- Telamon Ventura, California |
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#8
December 25th 07, 02:47 PM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun IsToo Expensive
Telamon wrote:
In article , David wrote: RHF wrote: On Dec 23, 1:27 pm, Telamon wrote: In article , David wrote: Telamon wrote: In article , Telamon wrote: In article , David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website :http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - - MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...7e40978fdc32ac 0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...77d380609eec59 2 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF . [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? OK I'll answer it. None. Less pinching in the midriff... There's a rule. ? OK here is the rule, when you have an impedance mismatch ? by some ratio it does not matter which system element is ? higher or lower so for example if the coax transmission ? line is 50 ohms and the antenna impedance is 25 or 75 ohms ? the result is the same amount of reflected power. ? 25 ohms and 75 ohms are equivalent in this regard. ? One is not a better situation than the other. Telamon, Wouldn't it be the Ratios : 25 Ù Antenna to 50 Ù Coax ~ 1 : 2 50 Ù Coax to 100 Ù Antenna ~ 1 : 2 -vice- 50 Ù Coax to 75 Ù Antenna ~ 2 : 3 (1 : 1.5) ~ RHF - Take an extreme case of this where you have either a short - or the coax is open with nothing connected on that end. - In either case if you were to send RF power to the open - or short end of the cable you would have 100% reflected - power. The returned phase of the that power would be 90 - degrees different though. - - This is different situation then DC current where the open - and short would have very different consequences. Low goes into high better than high goes into low. Reflected power does no harm in a receive antenna. Try using your 300 Ohm antenna with a 50 Ohm transmission line. Then try using a 50 Ohm antenna with a 300 Ohm transmission line. Which will receive better? Neither will be better. If you don't understand this look up VSWR and study that topic. Of course there is not enough power to hurt any part of a receive antenna or transmission line but it harms your reception. When it comes to RF all that matters is whether two components match and if they don't how far apart they are in impedance. It does not matter which is higher than the other; the results will be the same reflected power. It's a simple rule that applies to many a physics problem not just antennas and transmission lines such as light through a prism or light passing from air to water. I am going by strictly anecdotal practical experience. If I am wrong, so be it. My Palomar MLB works a lot better (ca. 20 s units) than hooking a longwire directly to the center conductor of the cable. But there is virtually no loss if I connect the other end of the cable to the 500 Ohm input on the radio, rather than the 50 Ohm SO-239. |
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#9
December 25th 07, 03:36 PM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is TooExpensive
On Dec 25, 6:47*am, David wrote:
Telamon wrote: In article , *David wrote: RHF wrote: On Dec 23, 1:27 pm, Telamon wrote: In article , *David wrote: Telamon wrote: In article , *Telamon wrote: In article , *David wrote: RHF wrote: The Verdict {One Man's Opinion} : Magnetic Longwire Balun Is Too Expensive http://www.hard-core-dx.com/nordicdx.../magbalun.html -by- Alan Johnson -source- Hard-Cord-DX website :http://www.hard-core-dx.com/ The Most Common Antenna Type Randon Wire Antenna Problems Enter the Balun The Magnetic Longwire Balun (MLB) In the Laboratory After Four Rainy WeekEnds I also did A-B Comparisons * The Results The "Resistance" Curve for the MLB The N8KDV Transformer A-B Testing was very Revealing. * Recommenation How Essential is a Perfect Match? Based on Price and Performance The MLB Definitely Wins Originally Published in the NASWA Journal - July 1992 -by- Alan Johnson [N4LUS] Magnetic Longwire Balun (MLB) http://www.universal-radio.com/catalog/sw_ant/1484.html http://www.dolstra.nl/Z&L-amateur/AN...tems/MLB_1.JPG http://www.remeeus.eu/english/hamradio/mlb.htm http://ham.srsab.se/graphics/antennas/mlbII.jpg -by- RF Systems - MSRP Price ~ $60 Alternative "MLB" - MLB-1 Magnetic Longwire Balun http://www.palomar-engineers.com/MLB-1/mlb-1.html -by- Palomar Engineers - MSRP Price ~ $50 NOTE - While the 'N8KDV Transformer' is presently Not Available. WinRadio does offer the LWA-0130 Long Wire Antenna Adapter http://www.grove-ent.com/WR0130.html http://www.winradio.com/home/lwa.htm http://www.winradio.com/home/ax05e.htm -by- WiNRADiO - *- MSRP Price ~ $40 READ - Good Deal on 9:1 Matching Transformer http://groups.google.com/group/rec.r...7e40978fdc32ac 0 -by- William Fieldstone More WinRadio LWA-0130 Long Wire Antenna Adapter Postings http://groups.google.com/group/rec.r...77d380609eec59 2 http://groups.yahoo.com/group/Shortw...na/message/230 iane ~ RHF *. [D]iane, The point is to keep the feedpoint Z below the transmission line Z. What's the advantage of the feed-point Z being below the transmission line Z? OK I'll answer it. None. Less pinching in the midriff... There's a rule. ? OK here is the rule, when you have an impedance mismatch ? by some ratio it does not matter which system element is ? higher or lower so for example if the coax transmission ? line is 50 ohms and the antenna impedance is 25 or 75 ohms ? the result is the same amount of reflected power. ? 25 ohms and 75 ohms are equivalent in this regard. ? One is not a better situation than the other. Telamon, Wouldn't it be the Ratios : 25 Ù Antenna to 50 Ù Coax ~ 1 : 2 50 Ù Coax to 100 Ù Antenna ~ 1 : 2 -vice- 50 Ù Coax to 75 Ù Antenna ~ 2 : 3 (1 : 1.5) ~ RHF - Take an extreme case of this where you have either a short - or the coax is open with nothing connected on that end. - In either case if you were to send RF power to the open - or short end of the cable you would have 100% reflected - power. The returned phase of the that power would be 90 - degrees different though. - - This is different situation then DC current where the open - and short would have very different consequences. Low goes into high better than high goes into low. *Reflected power does no harm in a receive antenna. *Try using your 300 Ohm antenna with a 50 Ohm transmission line. *Then try using a 50 Ohm antenna with a 300 Ohm transmission line. *Which will receive better? Neither will be better. If you don't understand this look up VSWR and study that topic. Of course there is not enough power to hurt any part of a receive antenna or transmission line but it harms your reception. When it comes to RF all that matters is whether two components match and if they don't how far apart they are in impedance. It does not matter which is higher than the other; the results will be the same reflected power. It's a simple rule that applies to many a physics problem not just antennas and transmission lines such as light through a prism or light passing from air to water. - I am going by strictly anecdotal practical experience. * - If I am wrong, so be it. * - My Palomar MLB works a lot better (ca. 20 s units) than - hooking a longwire directly to the center conductor of the cable. MLB-1 Magnetic Longwire Balun -by- Palomar Engineers MLB-1 - http://www.palomar-engineers.com/MLB-1/mlb-1.html -msrp- Price ~ $50 OK - That would be having the MLB Connected with the 9-Side-Wire to the Antenna Wire and the 1-Side-SO-239 Jack to the Coax Cable; with the Coax Cable 'Grounded' at the Receiver via the SO-239 50-Ohm Antenna Input. -*But there is virtually no loss if I connect the other end of the cable to - the 500 Ohm input on the radio, rather than the 50 Ohm SO-239. I can understand how you make the Coax Cable's Pl-259 Plug -to- the Receiver's SO-239 Jack 'Connection'. -But- How do you make the Coax Cable/PL-259 Plug -to- 500-Ohm Terminals 'Connection' ? i want to know -and- a merry christmas ~ RHF |
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#10
December 26th 07, 01:25 PM
posted to rec.radio.shortwave
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The Verdict {One Man's Opinion} : Magnetic Longwire Balun IsToo Expensive
Telamon wrote:
Don't just take my word for it. Go look up VSWR and read just a few paragraphs on the subject. You work in electronics, this is important for you to understand. Search for the term index of refraction for similar concepts in physics for lightwaves, which are EM waves. Then you will get the idea behind refraction of radio waves in the upper atmosphere. Short wave radio can teach you a lot. One condition is closer to a short circuit. That's all I know. I always match impedance for maximum power transfer. I voltage match as well, when power is not so important, e.g. signal sampling. In practical usage, "receive only" is closer to sampling. I know enough about electronics to keep my sorry ass employed. |
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