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

Wed Mar 16 00:33:17 UTC 2016

This may not be a lot of help but you want RG-62.  You can buy it by the foot but I do not have any,  I used mine up working on the WRAPS rotor.  RG-62 uses an RG-59 connector.
DougK9DLP

      From: Joe <nss at mwt.net>
 To: amsat-bb at amsat.org 
 Sent: Tuesday, March 15, 2016 3:45 PM
 Subject: Re: [amsat-bb] Homebrew Up-Dated Eggbeater Antenna (correction)

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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> to all interested persons worldwide without requiring membership. Opinions expressed
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>

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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