give the newbie the full story on ELK and ARROW please
Yes folks can make contacts with Arrow and Elk antennas because it is done every day of the week . . . . that is not the argument here . . . my comments have been made to give full disclosure of the several issues which seemed to be ignored by advocats of one over the other . . .
Arrow and Elk are LINEARLY polarized antennas . . . . the 17,000 mph moving satellite is throwing off CIRCULAR polarized RF energy . . . please SUBTRACT 3 db or more of gain from your Elk or Arrow when receiving the satellite's signal . . . some still do not understand this concept and never will . . . ignorance is bliss . . . .
For years I grinned ; like I am doing now whenever I saw an 18 wheel trucker with a pair of 3 foot high verticals and a big coil of aluminum tubing at the bottom . . . . probably a good analogy . . . . yes they can make contacts for a little distance just like users of the Arrow and Elk can make contacts . . . .
yes "field tests" ( anecdotal evidence ) give you some sense of satisfaction . . . . some CB ers enjoy CB operating too . . . ignorance is bliss . . . . .working a buddy across town from his house to yours on 2 mtrs or 435 mhz is one thing because your antennas are not moving . . . . once one of them starts moving quickly ( 17,000 mph ) it all changes . . . I realize that this requires some further reading, studying and understanding . . . .you need to understand the entire story . . . . ignorance is still bliss for far too many . . .
up until about 1952 folks used monoband beams . . . . then the triband beams with traps appeared . . . degradation occurs one small step at a time . . . it is progressive too . . . now we have folks doing CW with their computers during contests and they think that they are CW ops . . . . . . note I did not say sending . . .
a couple of locals were all in a lather a few years ago when the local DX packet cluster went down . . . what are we going to do . . . I told them it really made no difference to me as I will continue to TUNE the bands for the DX . . . because that is what a DXer does . . .
the DUMMYING DOWN of hams is sad . . . of course it depends upon your base of experience . . . . if you do not know any better . . . well ignorance is bliss . . . we do need fuller disclosure to the newbie who asks a question . . . .
If somebody says : yes I know all of that but this is my compromise; that is fine . . . but folks are preaching to folks who ask questions : what should I buy ? . . . . there is another option which is being ignored . . . thus my questioning to let the newbie know that these antennas work but there should be a caveat of the compromise . . . without that caveat or understanding they think they are on the Gold Standard . . . ignorance is still bliss . . . in other areas we call it :
1) doing due diligence or 2) informed consent . . . . some folks hand over all their money to somebody else to manage . . .oh yes . .. ignorance turns from being bliss . . .to catastrophic . . . but it goes on and will continue . . .
Some folks are selling these antennas like some sell religion . . . with certainty that theirs is the one true one . . .give the newbie the FULL STORY please. . . that has been my goal for several weeks now . . . I have received many nice personal emails thanking me for my comments . . . I am not bashing ARROW or ELK just trying to give a FULL DISCLOSURE which is what should be going on not just blind advocacy for one of these over the other . . . . which is mostly what I have seen with anecdotal comments . . .
Jim W9VNE
Arrow and Elk are LINEARLY polarized antennas . . . . the 17,000 mph moving satellite is throwing off CIRCULAR polarized RF energy . . . please SUBTRACT 3 db or more of gain from your Elk or Arrow when receiving the satellite's signal . . . some still do not understand this concept and never will . . . ignorance is bliss . . . .
This is not always correct. AO-27 and SO-50 both use linear antennas for their downlink transmitters. Even with AO-51, the downlink signal is likely to be elliptical most of the time depending on squint angles. The point to take away from this is when using a handheld yagi, always try to peak the signals on both uplink and downlink by rotating the antenna. The up to ~20db of potential mismatch is more important than the gain of the antenna. All the current FM satellites use linear whips for the uplink receivers; peaking the polarity from worst case to best case is like adding a 500 watt amplifier to your 5 watt HT. To do this on transmit requires full duplex.
Here's another way to look at it. After the launch of AO-51, we heard several people say AO-27 seemed to have a stronger signal. AO-27 typically ran a 500mw downlink, and AO-51 ran similar power. Users with handheld yagis or whips who matched polarity gained 3 db on AO-27 reception as compared with AO-51 (assuming a close to circular signal from AO-51). That's the same as effectively doubling the downlink power on AO-27.
Sorry to impede anyone's bliss.
73, Drew KO4MA
We probably disagree . . . . years ago we would hear "picket fence" as the guys would call it from an FM mobile stations on two meters into the repeater . . . or simplex . . . . the point I have been attempting to make : I had not seen any comment until Andy responded to my attempt to make folks aware of CP or elliptical ( I will not split hairs ) and despite using a vertical they still generate deep fades by being linear polarized . . . that is my point give the newbie the full story . . . which has been sadly missing from the advocacy of Arrow vs. Elk . . . .
Jim W9VNE ----- Original Message ----- From: "Andrew Glasbrenner" [email protected] To: "Jim Danehy" [email protected]; [email protected] Sent: Sunday, December 28, 2008 12:15 PM Subject: Re: [amsat-bb] give the newbie the full story on ELK and ARROW please
Arrow and Elk are LINEARLY polarized antennas . . . . the 17,000 mph moving satellite is throwing off CIRCULAR polarized RF energy . . . please SUBTRACT 3 db or more of gain from your Elk or Arrow when receiving the satellite's signal . . . some still do not understand this concept and never will . . . ignorance is bliss . . . .
This is not always correct. AO-27 and SO-50 both use linear antennas for their downlink transmitters. Even with AO-51, the downlink signal is likely to be elliptical most of the time depending on squint angles. The point to take away from this is when using a handheld yagi, always try to peak the signals on both uplink and downlink by rotating the antenna. The up to ~20db of potential mismatch is more important than the gain of the antenna. All the current FM satellites use linear whips for the uplink receivers; peaking the polarity from worst case to best case is like adding a 500 watt amplifier to your 5 watt HT. To do this on transmit requires full duplex.
Here's another way to look at it. After the launch of AO-51, we heard several people say AO-27 seemed to have a stronger signal. AO-27 typically ran a 500mw downlink, and AO-51 ran similar power. Users with handheld yagis or whips who matched polarity gained 3 db on AO-27 reception as compared with AO-51 (assuming a close to circular signal from AO-51). That's the same as effectively doubling the downlink power on AO-27.
Sorry to impede anyone's bliss.
73, Drew KO4MA
As a newbie to AMSAT (but not the hobby) and not the original poster (but an owner of Arrow and Elk), thanks to ALL who have contributed to this thread. A discussion with much opportunity for learning for all, especially me.
We can conclude the following as (mostly, but not completely) the full story, based upon the threads, observations, and data/insight/experience from several hams with a gallon of experience and technical skills:
1. The Arrow and the Elk antennas "work," both on the repeater and passband birds. "Work" means the owner can make contacts at various elevations with power settings 5 watts and below, which is a common configuration of AMSAT users at this time (handheld HT, handheld antenna, rover). Many hams have this as their only option, so it will obviously be popular.
2. The Arrow and Elk antennas each have their fans, as shown by this BB and eham.net. While each person's mileage may vary, and anecdotes indicate that both work, there are many factors which may impact one operator's observations over another.
3. The Arrow and Elk antennas are compromise antennas. "Compromise" means simplicity and portability are optimized at the expense of performance. "Performance" is defined as optimum design for achieving maximum signal energy into the satellite AND maximum energy received from the satellite. It is not debatable that linear antennas will be sub-par to circularly polarized antennas as a general rule, and in many specific instances as well. (If twisting the Arrow or Elk is needed to optimize signals regardless of how easy it is, and if fading is a challenge with these antennas, then by definition they are not optimum performance antennas). What is debatable is the satisfaction of the operator based upon his/her expectations and knowledge of what is happening with the equipment. Satisfaction will be high for the informed amateur (see next point).
4. The choice of the Arrow or Elk antenna (or some other model) should be made as an informed decision. The following questions *should* be asked:
For the antenna, is it maximum Portability? Maximum Performance? Minimum Cost?
What is the transmitting/receiving equipment? Power amplifier (focus on this one last), preamp, dual receiver or dual rigs, receiver sensitivity, equipment type, etc.
What is the objective of the operator? VUCC? WAS? DX? Rag chewing? Experimental? Other VHF/UHF uses besides satellite?
What are the operator's expectations regarding performance (fading, flutter, path loss, etc.)
What is the operator's "power budget?" All items must be examined in the calculation, starting from power out of the rig to losses from connectors and feedline all the way through duplexers/diplexers/power dividers and then to the antenna. Also, things like obstructions (trees, leaves, etc) and factors like metal support masts must be considered. Finally, there is the satellite and its sensitivity and power output on the downlink. And these are *theoretical* calculations, there is also the actuality which can be determined with simple test equipment.
Once these factors are determined, then the operator "should" look at all the options. But examination of options requires some knowledge regarding propagation, antenna measurements, actual data (not only from the seller), and knowledge from those who have the experience. This information and calculations are available online and in manuals, including ARRL pubs. Does not require a EE degree, just some curiosity and an open mind.
5. For me, I don't think I will be working Europe with an Arrow or Elk antenna on AO7. Although I have worked into South America and Caribbean on AO51, I need to keep my expectations realistic.
6. For me, I will have a lot of fun with these antennas by taking them portable and demonstrating the hobby to others or tinkering.
7. For me, I would love to have a VUCC Satellite cert on my wall...esp since sunspots are at a lull right now.
8. For me, I will look further into homebrew antenna design and construction as well as higher performance antennas for these bands.
The best consumer / ham operator is an informed one.
And this is one of the elements of the Radio Amateur's creed: that the Radio Amateur is always improving his/her knowledge of the hobby and seeks to be the best he can be in terms of skill.
Again, thanks to those who took the time to share. It's a great part of this hobby.
Mark Lunday WD4ELG [email protected] http://wd4elg.net
All,
I apologize for the ignorant, dumbed-down, misguided and non-fully disclosing information I have provided - on this board and off of it - regarding what I have done working the satellites over the past 6 months given the choices I've made about assembling a station.
Jim - Did I miss your response to the direct question I asked last night about what the gain figures for the Elk ought to be - or is that question too ignorant to be worthy of an answer?
Tim - N3TL
------------- Original message from "Jim Danehy" [email protected]: --------------
Yes folks can make contacts with Arrow and Elk antennas because it is done every day of the week . . . . that is not the argument here . . . my comments have been made to give full disclosure of the several issues which seemed to be
ignored by advocats of one over the other . . . Arrow and Elk are LINEARLY polarized antennas . . . . the 17,000 mph moving satellite is throwing off CIRCULAR polarized RF energy . . . please SUBTRACT 3 db or more of gain from your Elk or Arrow when receiving the satellite's signal . . . some still do not understand this concept and never will . . . ignorance is bliss . . . . For years I grinned ; like I am doing now whenever I saw an 18 wheel trucker with a pair of 3 foot high verticals and a big coil of aluminum tubing at the bottom . . . . probably a good analogy . . . . yes they can make contacts for a little distance just like users of the Arrow and Elk can make contacts . . . .
yes "field tests" ( anecdotal evidence ) give you some sense of satisfaction . . . . some CB ers enjoy CB operating too . . . ignorance is bliss . . . . .working a buddy across town from his house to yours on 2 mtrs or 435 mhz is one thing because your antennas are not moving . . . . once one of them starts moving quickly ( 17,000 mph ) it all changes . . . I realize that this requires some further reading, studying and understanding . . . .you need to understand the entire story . . . . ignorance is still bliss for far too many . . .
up until about 1952 folks used monoband beams . . . . then the triband beams with traps appeared . . . degradation occurs one small step at a time . . . it is progressive too . . . now we have folks doing CW with their computers during contests and they think that they are CW ops . . . . . . note I did not say sending . . .
a couple of locals were all in a lather a few years ago when the local DX packet cluster went down . . . what are we going to do . . . I told them it really made no difference to me as I will continue to TUNE the bands for the DX . . . because that is what a DXer does . . .
the DUMMYING DOWN of hams is sad . . . of course it depends upon your base of experience . . . . if you do not know any better . . . well ignorance is bliss . . . we do need fuller disclosure to the newbie who asks a question . . . .
If somebody says : yes I know all of that but this is my compromise; that is fine . . . but folks are preaching to folks who ask questions : what should I buy ? . . . . there is another option which is being ignored . . . thus my questioning to let the newbie know that these antennas work but there should be a caveat of the compromise . . . without that caveat or understanding they think they are on the Gold Standard . . . ignorance is still bliss . . . in other areas we call it :
- doing due diligence or 2) informed consent . . . . some folks hand over all
their money to somebody else to manage . . .oh yes . .. ignorance turns from being bliss . . .to catastrophic . . . but it goes on and will continue . . .
Some folks are selling these antennas like some sell religion . . . with certainty that theirs is the one true one . . .give the newbie the FULL STORY please. . . that has been my goal for several weeks now . . . I have received many nice personal emails thanking me for my comments . . . I am not bashing ARROW or ELK just trying to give a FULL DISCLOSURE which is what should be going on not just blind advocacy for one of these over the other . . . . which is mostly what I have seen with anecdotal comments . . .
Jim W9VNE _______________________________________________ Sent via [email protected]. 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
http://davehouston.net/eggbeater.htm
A straight forward explanation with lengths of phasing line given for different Freqs...
DE - KD1PE DN71
Jack,
Thanks very much for posting this link.
73 and Happy New Year,
Tim - N3TL -------------- Original message from "Jack K." [email protected]: --------------
http://davehouston.net/eggbeater.htm
A straight forward explanation with lengths of phasing line given for different Freqs...
DE - KD1PE DN71
Sent via [email protected]. 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
The Elk appears to be a log periodic. Anybody tried building a pair of these, orthoganally mounted on a common boom, and phased to give circular polarisation? Is it possible to build a wideband (to cover 2 and 70) phasing harness or device even?
Jim Danehy wrote:
Arrow and Elk are LINEARLY polarized antennas . . . . the 17,000 mph moving satellite is throwing off CIRCULAR polarized RF energy . . . please SUBTRACT 3 db or more of gain from your Elk or Arrow when receiving the satellite's signal . . . some still do not understand this concept and never will . . . ignorance is bliss . . . .
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participants (6)
-
Andrew Glasbrenner -
Jack K. -
Jim Danehy -
Mark Lunday, WD4ELG -
n3tl＠bellsouth.net -
Nigel Gunn G8IFF/W8IFF