[amsat-bb] EO-80 FM Transponder Tested (noise floor?)

[Paul Stoetzer]

That is definitely true. I have terrible noise in certain directions
here in southwest Washington, DC (especially at night - the lighting
on the north fence of my apartment building puts out a hash that
completely wipes out 2m, but is OK on 70cm). The noise level doesn't
affect FM as much, though.

73,

Paul, N8HM

On Wed, Jun 17, 2015 at 12:26 PM, Robert Bruninga <bruninga at usna.edu> wrote:
> I also am a proponent ot using 2m for weak downlinks because of the 9 dB
> advantage.  But it has been pointed out to me that there is a higher
> background noise component that needs to be considered.  I have not done
> this.  My assumption is that the noise floor at 2m is maybe about 3 dB
> worse than at 70cm?
>
> So 2m still wins, but I'm not sure of what the real noise floor is.
>
> Bob, WB4aPR
>
> -----Original Message-----
> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Zach
> Leffke
> Sent: Wednesday, June 17, 2015 11:23 AM
> To: amsat-bb at amsat.org
> Subject: Re: [amsat-bb] EO-80 FM Transponder Tested
>
> Paul beat me to the punch as I was typing up my response, but I'm sending
> it anyway:
>
> Path Loss.  ->  function of lambda (wavelength) squared.
> So all other things being equal (antenna gains, power levels, range,
> etc.), you can look at the power ratio of the two.
>
> Rough calculation (going from 2m to 70cm):
> 10log[(0.70/2)^2] = -9.1 dB
> OR
> Rough calculation (going from 70cm to 2m):
> 10log[(2/0.7)^2] = +9.1 dB
>
> The thing to watch out for is antenna gains on the ground.  The arrow for
> example has more gain on 70cm (7el) than it does on 2m (3el).  So while 2m
> has a 9-ish dB improvement over 70cm in terms of path loss, the receiver
> may not see the full 9dB because of the difference in gains on the antenna
> between the two bands.
>
> Again VERY rough approximation (for demonstration purposes only):
> 3el yagi -> call it 7.5 ish dB of gain
> 7el yagi -> call it 11.5 ish dB of gain
> so, about 4 dB of LOST gain (going from 70cm to 2m using the arrow
> example).
>
> So net gain going from 70cm to 2m (all other things equal except the gains
> on the arrow antenna) 9dB - 4dB = 5dB
>
> so your typo was actually fairly close :-) for those planning to use their
> existing setup for the new birds.
>
> -Zach, KJ4QLP
>
> On 6/17/2015 10:43 AM, Andrew Koenig wrote:
>> *9dB (typo)
>>
>> On Wed, Jun 17, 2015 at 9:42 AM, Andrew Koenig <ke5gdb at gmail.com> wrote:
>>
>>> Can you explain the 6dB advantage 2m has over 70cm? I've seen it here
>>> on the amsat-bb, and in the mesh realm when comparing 2.4GHz and
>>> 5.8GHz WiFi gear, but it still hasn't "clicked."
>>>
>>> 73 de KE5GDB
>>>
>>> On Tue, Jun 16, 2015 at 6:56 PM, Paul Stoetzer <n8hm at arrl.net> wrote:
>>>
>>>> Nick,
>>>>
>>>> It should be even stronger than AO-27's 500 mW, AO-27 had a 70cm
>>>> downlink, the EO-80 downlink is on 2 meters, so EO-80's signal
>>>> should be up to 9 dB stronger than AO-27 (12 dB stronger if they run
>>>> it at 1 watt).
>>>>
>>>> 73,
>>>>
>>>> Paul, N8HM
>>>>
>>>> On Tue, Jun 16, 2015 at 7:49 PM, Nicholas Mahr
>>>> <nicholasmahr1 at gmail.com>
>>>> wrote:
>>>>> Thats very good news, Hopefully the two get activated before field
> day?
>>>> Im
>>>>> most looking forward to EO-80, It should be like AO-27 with 500Mw or
> 1W.
>>>>> Good to know both are working well and wish a long life to them.
>>>>>
>>>>> 73 KE8AKW
>>>>> _______________________________________________
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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.
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>>>> are solely those of the author, and do not reflect the official
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>>>
>>>
>>> --
>>> Andrew Koenig
>>>
>>
>>
>
>
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> _______________________________________________
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