Steve and all I believe simply lengthing a helix will reach a point of diminishing returns. It would be better to stack a couple or even four twenty or so turn turn helix antennas (from VE3NPC). You could with proper phasing generate a CP signal from a couple of loopers. I just haven't heard of anyone doing that, though it looks good on paper. 73 Bob W7LRD Seattle
-------------- Original message -------------- From: Steve Raas sraas@optonline.net
In reading much of the discussion that has hit the BB lately in regards to antennas I figured Ide toss in my questions to the group.
In trying to figure out which style antenna is going to suit my needs best I have a few questions.
#1 Is a linear polarized antenna less efficient than a RHCP antenna when trying to receive or transmit to a rhcp signal / receiver?
#2 If yes.. in theory how much?
#3 In looking @ pre-built helix options for 1.2g I have found the DSH23-12 which is a 23 cm RHCP 12 turn helix 14.5 dBic gain in a machined radome for best weather protection. 1.2-1.3 GHz bandwidth. 50 ohm feed wit h N (f) connector on 8" backplane. All stainless hardware; Designed for PHASE 3D uplink operation. Wide bandwidth actually covers from 900 - 1600 MHz ( copied verbatium from the www.directivesystems.com website. In looking at the specs of this helix, it seems it may not have the desired gain for P3E or others. In 'theroy' is it possible to make a 24 turn helix , and if so would I be correct in thinking that double the turns would provide at or near 3.0 db of additional gain?
#4 If yes to question 3 would this antenna be @ or near double the physical length?
In a email I sent to Dave @ Directive he told me that the loopers he has can be arranged for vert/linear or horizontal polarization, so I do think that a looper although a great antenna may not be the best single antenna solution for 1.2 Uplin k.
Thoughts, Ideas & comments please.
-Steve Raas
N2JDQ
FN20vg
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
You loose 3 dB linear to circular, circular to circular of the same rotation is best for satellite work eliminating fading during rotational shift and multipath. I agree about diminishing returns on a Helix. I have phased two for linear polorization ( counter rotating 1.2 GHz). The BBQ grill is a simple solution, 18 dBi 1.2 and 24 dBi 2.4 with a small form factor, I use it portable and it fits in my car. If you have room for a 12' boom why not a 10' TVRO dish? You could go portable with a Semi Truck!
Art ----- Original Message ----- From: w7lrd@comcast.net To: "Steve Raas" sraas@optonline.net; amsat-bb@amsat.org Sent: Monday, May 07, 2007 9:13 PM Subject: [amsat-bb] Re: Helix vs. loopers
Steve and all I believe simply lengthing a helix will reach a point of diminishing returns. It would be better to stack a couple or even four twenty or so turn turn helix antennas (from VE3NPC). You could with proper phasing generate a CP signal from a couple of loopers. I just haven't heard of anyone doing that, though it looks good on paper. 73 Bob W7LRD Seattle
-------------- Original message -------------- From: Steve Raas sraas@optonline.net
In reading much of the discussion that has hit the BB lately in regards to antennas I figured Ide toss in my questions to the group.
In trying to figure out which style antenna is going to suit my needs best I have a few questions.
#1 Is a linear polarized antenna less efficient than a RHCP antenna when trying to receive or transmit to a rhcp signal / receiver?
#2 If yes.. in theory how much?
#3 In looking @ pre-built helix options for 1.2g I have found the DSH23-12 which is a 23 cm RHCP 12 turn helix 14.5 dBic gain in a machined radome for best weather protection. 1.2-1.3 GHz bandwidth. 50 ohm feed wit h N (f) connector on 8" backplane. All stainless hardware; Designed for PHASE 3D uplink operation. Wide bandwidth actually covers from 900 - 1600 MHz ( copied verbatium from the www.directivesystems.com website. In looking at the specs of this helix, it seems it may not have the desired gain for P3E or others. In 'theroy' is it possible to make a 24 turn helix , and if so would I be correct in thinking that double the turns would provide at or near 3.0 db of additional gain?
#4 If yes to question 3 would this antenna be @ or near double the physical length?
In a email I sent to Dave @ Directive he told me that the loopers he has can be arranged for vert/linear or horizontal polarization, so I do think that a looper although a great antenna may not be the best single antenna solution for 1.2 Uplin k.
Thoughts, Ideas & comments please.
-Steve Raas
N2JDQ
FN20vg
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Helix antennas can be constructed to provide usefull gain with up to 40 turns if designed with a circumference of one wavelength and a pitch angle of 12.5 degrees. In my direct experimental comparison measurements outlined in the May/June 2006 AMSAT Journal the max gain formulas used on various web sites and amateur publications, for as yet some undetermined reason, do not provide the predicted gain, but had less gain and increased side lobes. The longer the antenna the greater the deviation from that predicted.
As stated previously feed line losses are a big problem for many hams at 1.2 GHz. My array (VE3NPC) is fed with 5 ft of RG/8U in the shack, 35 feet of 1/2 in hard line and another 5 feet of flexible RG/8U at the antenna.
I have 10 watts from my FT-736 and have never measured what it is at the antenna. It perfomed very well on AO-40 where I logged 832 SSB QSO's in mode L/S.
For helix design dimensions go to http://www.rac.ca and select calculators, helix antennas and then Kraus. (not Emerson as those max gain dimensions result in a poorly performing antenna).
Clare VE3NPC
----- Original Message ----- From: "kc6uqh" kc6uqh@cox.net To: w7lrd@comcast.net; "Steve Raas" sraas@optonline.net; amsat-bb@amsat.org Sent: Tuesday, May 08, 2007 12:46 AM Subject: [amsat-bb] Re: Helix vs. loopers
You loose 3 dB linear to circular, circular to circular of the same rotation is best for satellite work eliminating fading during rotational shift and multipath. I agree about diminishing returns on a Helix. I have phased two for linear polorization ( counter rotating 1.2 GHz). The BBQ grill is a simple solution, 18 dBi 1.2 and 24 dBi 2.4 with a small form factor, I use it portable and it fits in my car. If you have room for a 12' boom why not a 10' TVRO dish? You could go portable with a Semi Truck!
Art ----- Original Message ----- From: w7lrd@comcast.net To: "Steve Raas" sraas@optonline.net; amsat-bb@amsat.org Sent: Monday, May 07, 2007 9:13 PM Subject: [amsat-bb] Re: Helix vs. loopers
Steve and all I believe simply lengthing a helix will reach a point of diminishing returns. It would be better to stack a couple or even four twenty or so turn turn helix antennas (from VE3NPC). You could with proper phasing generate a CP signal from a couple of loopers. I just haven't heard of anyone doing that, though it looks good on paper. 73 Bob W7LRD Seattle
-------------- Original message -------------- From: Steve Raas sraas@optonline.net
In reading much of the discussion that has hit the BB lately in regards to antennas I figured Ide toss in my questions to the group.
In trying to figure out which style antenna is going to suit my needs best I have a few questions.
#1 Is a linear polarized antenna less efficient than a RHCP antenna when trying to receive or transmit to a rhcp signal / receiver?
#2 If yes.. in theory how much?
#3 In looking @ pre-built helix options for 1.2g I have found the DSH23-12 which is a 23 cm RHCP 12 turn helix 14.5 dBic gain in a machined radome for best weather protection. 1.2-1.3 GHz bandwidth. 50 ohm feed wit h N (f) connector on 8" backplane. All stainless hardware; Designed for PHASE 3D uplink operation. Wide bandwidth actually covers from 900 - 1600 MHz ( copied verbatium from the www.directivesystems.com website. In looking at the specs of this helix, it seems it may not have the desired gain for P3E or others. In 'theroy' is it possible to make a 24 turn helix , and if so would I be correct in thinking that double the turns would provide at or near 3.0 db of additional gain?
#4 If yes to question 3 would this antenna be @ or near double the physical length?
In a email I sent to Dave @ Directive he told me that the loopers he has can be arranged for vert/linear or horizontal polarization, so I do think that a looper although a great antenna may not be the best single antenna solution for 1.2 Uplin k.
Thoughts, Ideas & comments please.
-Steve Raas
I have found that the support material has an effect on heilxes over 10T. A 40 turn helix can be a challenge to support, and winding it on solid PVC pipe will have a considerable effect on the gain of long Helixes. Plastic charaterstics at microwave frequencies must be considered and if it slows the wave the helix will loose its focus. Support rods help, but make for a flimsy antenna. Best to phase shorter ones for a robust antenna.
Art, KC6UQH ----- Original Message ----- From: "Clare Fowler" lcfowler@magma.ca To: "amsat-bb" amsat-bb@amsat.org Sent: Tuesday, May 08, 2007 5:52 PM Subject: [amsat-bb] Re: Helix vs. loopers
Helix antennas can be constructed to provide usefull gain with up to 40 turns if designed with a circumference of one wavelength and a pitch angle of 12.5 degrees. In my direct experimental comparison measurements outlined in the May/June 2006 AMSAT Journal the max gain formulas used on various web sites and amateur publications, for as yet some undetermined reason, do not provide the predicted gain, but had less gain and increased side lobes. The longer the antenna the greater the deviation from that predicted.
As stated previously feed line losses are a big problem for many hams at 1.2 GHz. My array (VE3NPC) is fed with 5 ft of RG/8U in the shack, 35 feet of 1/2 in hard line and another 5 feet of flexible RG/8U at the antenna.
I have 10 watts from my FT-736 and have never measured what it is at the antenna. It perfomed very well on AO-40 where I logged 832 SSB QSO's in mode L/S.
For helix design dimensions go to http://www.rac.ca and select calculators, helix antennas and then Kraus. (not Emerson as those max gain dimensions result in a poorly performing antenna).
Clare VE3NPC
----- Original Message ----- From: "kc6uqh" kc6uqh@cox.net To: w7lrd@comcast.net; "Steve Raas" sraas@optonline.net; amsat-bb@amsat.org Sent: Tuesday, May 08, 2007 12:46 AM Subject: [amsat-bb] Re: Helix vs. loopers
You loose 3 dB linear to circular, circular to circular of the same rotation is best for satellite work eliminating fading during rotational shift and multipath. I agree about diminishing returns on a Helix. I have phased two for linear polorization ( counter rotating 1.2 GHz). The BBQ grill is a simple solution, 18 dBi 1.2 and 24 dBi 2.4 with a small form factor, I use it portable and it fits in my car. If you have room for a 12' boom why not a 10' TVRO dish? You could go portable with a Semi Truck!
Art ----- Original Message ----- From: w7lrd@comcast.net To: "Steve Raas" sraas@optonline.net; amsat-bb@amsat.org Sent: Monday, May 07, 2007 9:13 PM Subject: [amsat-bb] Re: Helix vs. loopers
Steve and all I believe simply lengthing a helix will reach a point of diminishing returns. It would be better to stack a couple or even four twenty or so turn turn helix antennas (from VE3NPC). You could with proper phasing generate a CP signal from a couple of loopers. I just haven't heard of anyone doing that, though it looks good on paper. 73 Bob W7LRD Seattle
-------------- Original message -------------- From: Steve Raas sraas@optonline.net
In reading much of the discussion that has hit the BB lately in regards to antennas I figured Ide toss in my questions to the group.
In trying to figure out which style antenna is going to suit my needs best I have a few questions.
#1 Is a linear polarized antenna less efficient than a RHCP antenna when trying to receive or transmit to a rhcp signal / receiver?
#2 If yes.. in theory how much?
#3 In looking @ pre-built helix options for 1.2g I have found the DSH23-12 which is a 23 cm RHCP 12 turn helix 14.5 dBic gain in a machined radome for best weather protection. 1.2-1.3 GHz bandwidth. 50 ohm feed wit h N (f) connector on 8" backplane. All stainless hardware; Designed for PHASE 3D uplink operation. Wide bandwidth actually covers from 900 - 1600 MHz ( copied verbatium from the www.directivesystems.com website. In looking at the specs of this helix, it seems it may not have the desired gain for P3E or others. In 'theroy' is it possible to make a 24 turn helix , and if so would I be correct in thinking that double the turns would provide at or near 3.0 db of additional gain?
#4 If yes to question 3 would this antenna be @ or near double the physical length?
In a email I sent to Dave @ Directive he told me that the loopers he has can be arranged for vert/linear or horizontal polarization, so I do think that a looper although a great antenna may not be the best single antenna solution for 1.2 Uplin k.
Thoughts, Ideas & comments please.
-Steve Raas
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "kc6uqh" kc6uqh@cox.net To: "Clare Fowler" lcfowler@magma.ca; "amsat-bb" amsat-bb@amsat.org Sent: Wednesday, May 09, 2007 1:51 AM Subject: [amsat-bb] Re: Helix vs. loopers
I have found that the support material has an effect on heilxes over 10T. A 40 turn helix can be a challenge to support, and winding it on solid PVC pipe will have a considerable effect on the gain of long Helixes. Plastic charaterstics at microwave frequencies must be considered and if it slows the wave the helix will loose its focus. Support rods help, but make for a flimsy antenna. Best to phase shorter ones for a robust antenna.
My direct comparison measurements showed no difference in gain or pattern between a 13 turn helix of 1 wavelength in circumference and a pitch angle of 12.5 degrees using either a 1/2 x 3/16 in fibre glass stake, a 1/2 inch aluminum tube or 25 mm PVC pipe boom at 2.4 GHz. However I never tested longer ones using PVC where it could well start to have an effect.
I personnaly would not use PVC due to its weight. I like to keep things as light as possible and use aluminum wire, and fiber glass stakes. These 5 foot long stakes can be coupled together to make a a 10 foot boom. It seems flimsy and does blow around a bit in the wind but they are very strong and I have never had one break, in over 10 years of use, even in the ice storm.
An aluminum tube down the center has little or no effect so you could use a round or square one for a long boom.
The merrits of a long boom or 2 or 4 short ones has some trade offs. You get increased losses with connectors and cables and power combiner for an array. You have to ensure that the signals from each antenna combine exactly in phase. However the gain starts to fall off over about 30 turns. So about 40 turns is the trade off point. You have less mounting hardware for longer ants but it is less robust.
Clare VE3NPC
Art, KC6UQH ----- Original Message ----- From: "Clare Fowler" lcfowler@magma.ca To: "amsat-bb" amsat-bb@amsat.org Sent: Tuesday, May 08, 2007 5:52 PM Subject: [amsat-bb] Re: Helix vs. loopers
Helix antennas can be constructed to provide usefull gain with up to 40 turns if designed with a circumference of one wavelength and a pitch angle of 12.5 degrees. In my direct experimental comparison measurements outlined in the May/June 2006 AMSAT Journal the max gain formulas used on various web sites and amateur publications, for as yet some undetermined reason, do not provide the predicted gain, but had less gain and increased side lobes. The longer the antenna the greater the deviation from that predicted.
As stated previously feed line losses are a big problem for many hams at 1.2 GHz. My array (VE3NPC) is fed with 5 ft of RG/8U in the shack, 35 feet of 1/2 in hard line and another 5 feet of flexible RG/8U at the antenna.
I have 10 watts from my FT-736 and have never measured what it is at the antenna. It perfomed very well on AO-40 where I logged 832 SSB QSO's in mode L/S.
For helix design dimensions go to http://www.rac.ca and select calculators, helix antennas and then Kraus. (not Emerson as those max gain dimensions result in a poorly performing antenna).
Clare VE3NPC
Hi all:
At 07:24 PM 5/9/2007, Clare Fowler wrote:
----- Original Message ----- From: "kc6uqh" kc6uqh@cox.net
I have found that the support material has an effect on heilxes over 10T. A 40 turn helix can be a challenge to support, and winding it on solid PVC pipe will have a considerable effect on the gain of long Helixes. Plastic charaterstics at microwave frequencies must be considered and if it slows the wave the helix will loose its focus. Support rods help, but make for a flimsy antenna. Best to phase shorter ones for a robust antenna.
I have use a card of 1/2-inch plywood to support #10 copper windings (1296-MHz dish feed). I have used a 5/16-inch diam bolt with PVC tubing slipped over to insulate copper winding (2400-MHz dish feed helix). I used a 1-1/4 inch diam. wooden closet pole with wooden dowel posts for a 23-turn helix on 437-MHz (the painted pole broke after a couple years in the wx - not recommended).
The merrits of a long boom or 2 or 4 short ones has some trade offs. You get increased losses with connectors and cables and power combiner for an array. You have to ensure that the signals from each antenna combine exactly in phase.
Not that hard but all coax lines must be equal length. Stacking four will net about 5.5 dB over one as about 0.5 dB is lost in the 4-way divider and lines. Stacking more than four is probably counterproductive (use a dish instead) above 432-MHz.
However the gain starts to fall off over about 30 turns.
I have seen that 25-turns is about max length. Reason is that RF current is dissipated along the length of the helix as you go further from the feed point. This is due to radiation and ohmic losses in the helix. I was never happy with my Rx performance on 437 compared to a 21-element x-yagi in circular pol. What I use currently is the M2-436CP42 (16.5 dBdc) 18-foot boom.
73, Ed - KL7UW ====================================== BP40IQ 50-MHz - 10-GHz www.kl7uw.com 144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w DUBUS Magazine USA Rep dubususa@hotmail.com ======================================
participants (4)
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Clare Fowler -
Edward Cole -
kc6uqh -
w7lrd＠comcast.net