[amsat-bb] Homebrew Up-Dated Eggbeater Antenna (correction)

Wed Mar 16 14:30:23 UTC 2016

There are several listings on ebay.... RG-62  Belden 9269

73 Matt
W5LL

On 3/15/2016 3:45 PM, Joe wrote:
> Main problem seems to be the 93 ohm coax,,,
>
> anyone got a short piece?
>
> Joe WB9SBD
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 3/15/2016 3:11 PM, Robert Bruninga wrote:
>> Although my comments are true, I had not looked at the "updated" web 
>> page:
>> http://wb5rmg.somenet.net/k5oe/Eggbeater_2.html
>>
>> It appears he addressed all those issues and has an eggbeater design 
>> that
>> does address those same issues.  If that works, then that is the same 
>> thing
>> I was talking about and seems to be a good approach.  I'd love to see a
>> cookoff between the two antennas.  Bob...
>>
>> -----Original Message-----
>> From: Robert Bruninga [mailto:bruninga at usna.edu]
>> Sent: Tuesday, March 15, 2016 1:32 PM
>> Subject: RE: [amsat-bb] Homebrew Up-Dated Eggbeater Antenna
>>
>> My 2 cents:
>>
>> The problem with Eggbeaters is that their design goal (omni coverage) 
>> sounds
>> good but also means, by definition, equally poor in all directions.
>> There is no such thing as "gain" for an omni.  The closer its gain
>> approaches 3D omni, in all directions, then the closer its gain 
>> approaches
>> 0 dBi.  Of course, placed over a ground plane, then they can achieve 3
>> dBi...
>>
>> Now, on the other hand, satellites are nowhere near omni located.  
>> They are
>> 10dB or more farther away on the horizon than when they are overhead.
>> So you don't need as much gain at all overhead as you need on the 
>> horizon.
>>
>> Further, satellites spend more than 70% of all pass times below 22 
>> degrees!
>> (where they are weak) and only 5% of their time above 45 degrees 
>> where they
>> are 10 dB stronger.
>>
>> The last thing then that you need for "omni" coverage for a non-pointing
>> antenna, then, is gain that is UP (where the satellite is 10 times
>> stronger).
>>
>> See the scale drawings of a LEO pass: http://aprs.org/LEO-tracking.html
>>
>> BUT on the other hand, most cubesats simply do not have the power to 
>> close
>> the link to an OMNI antenna when it is on the horizon.  It just cannot
>> happen due to the distance and the omni only being at best 3 dB gain.
>>
>> So the BEST "omni" in my opinion is a 19" whip over a large metal ground
>> plane.  Not only does it provide 5 dBi gain above 15 degrees or so on 
>> VHF,
>> it also provides almost 7 dBi gain on UHF above about 30 degrees 
>> where it
>> acts as a 3/4 wave vertical..
>>
>> Yes, it has a null overhead, but the satellite is 10 times stronger 
>> then.
>> And the satleilte is only in that null less than 2% of all pass times.
>>
>> So the 19" vertical gives good gain from above the horizon in all 
>> directions
>> and sacrificaes some gain overhead wehre it is not needed.  And no omni
>> antenna is going to  hear these weak satellites all the way down on the
>> horizon where they are 10 times weaker.
>>
>> And a 19.25" vertical piece of wire over some chicken wire is pretty 
>> easy to
>> construct, AND it does not need to be on the top of a tower, since it 
>> cannot
>> hear to the horizon anyway.  So jjust put it where it can see most of 
>> the
>> sky above abouit 15 degrees and you will hear about all you can on an 
>> Omni.
>> And it is not bad...
>>
>> The value of a true circular hemispherical antenna is only when the 
>> satelile
>> is strong (ISS) and it can be heard even on the horizon.  Then the 
>> circula
>> hemispherical antenna has the advantage of fewer nulls in its 
>> pattern.  But
>> you give up gain where it is most needed to get that.
>>
>> And a low noise preamp is essential...
>>
>> Just my 2 cents...
>> Bob, WB4APR
>>
>> -----Original Message-----
>> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Paul
>> Stoetzer
>> Sent: Tuesday, March 15, 2016 1:12 PM
>> To: jim at k6ccc.org
>> Cc: amsat-bb at amsat.org
>> Subject: Re: [amsat-bb] Homebrew Up-Dated Eggbeater Antenna
>>
>> Jim,
>>
>> The key words here are "noise floor." Omnidirectional antennas can 
>> work for
>> satellites when you have a low noise floor and short runs of very 
>> good coax
>> (and/or a preamp).
>>
>> As an example, I've listened for SO-50 a couple of times from here in
>> Washington, DC with my Baofeng UV-3R+ and Nagoya NA-774 telescopic 
>> whip. I
>> can hear the satellite a bit, but still quite nosily, above 45 degrees.
>> Back in August, I was in a field in the middle of nowhere and heard 
>> it very
>> well from 5-7 degrees above the horizon.
>>
>> Another example is that some people report decent telemetry success from
>> AO-73 (when in high power mode) using nothing more than 1/4 wave whip.
>> I've never been able to decode a single packet with that type of 
>> setup here
>> in the city.
>>
>> Most people live somewhere between the two extremes I've presented 
>> here of
>> "field in the middle of nowhere" and "apartment building in a major 
>> urban
>> center" so your mileage may vary. Just keep in mind that in any 
>> receiving
>> system, you are looking for an optimal signal to noise ratio. If you 
>> have no
>> noise, you don't need much signal and omnidirectional antennas might 
>> work
>> fine. If you have a ton of noise, you are going to need a lot of 
>> signal from
>> the satellite, which means a beam with decent gain.
>>
>> 73,
>>
>> Paul, N8HM
>>
>> On Tue, Mar 15, 2016 at 12:46 PM, Jim Walls <jim at k6ccc.org> wrote:
>>> I built one about a decade or so ago and was grossly underwhelmed with
>> it.
>>> I built it to use for a sat igate.  I was able to decode maybe one or
>>> two packets per day.  Everything else was lost in the noise floor..
>>> Only had about 20 feet of RG-214 cable to the receiver.
>>>
>>>   Jim - K6CCC
>>>
>>>
>>>
>>>
>>>
>>> ----------------------------------------
>>>   From: "Joe" <nss at mwt.net>
>>> Sent: Tuesday, March 15, 2016 9:37 AM
>>> To: "amsat-bb at amsat org" <amsat-bb at amsat.org>
>>> Subject: [amsat-bb] Homebrew Up-Dated Eggbeater Antenna Has anyone
>>> built this antenna, and what are your opinions? Meet all the claims
>>> being made?
>>>
>>> http://wb5rmg.somenet.net/k5oe/Eggbeater_2.html
>>>
>>> Joe WB9SBD
>>> -- 
>>> Sig
>>> The Original Rolling Ball Clock
>>> Idle Tyme
>>> Idle-Tyme.com
>>> http://www.idle-tyme.com
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>>>
>>> _______________________________________________
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>> _______________________________________________
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>> interested persons worldwide without requiring membership. Opinions
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>> views of AMSAT-NA.
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>> _______________________________________________
>> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
>> to all interested persons worldwide without requiring membership. 
>> Opinions expressed
>> are solely those of the author, and do not reflect the official views 
>> of AMSAT-NA.
>> Not an AMSAT-NA member? Join now to support the amateur satellite 
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>>
>
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. 
> Opinions expressed
> are solely those of the author, and do not reflect the official views 
> of AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite 
> program!
> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>
>