# [amsat-bb] EO-80 FM Transponder Tested

Zach Leffke zleffke at vt.edu
Wed Jun 17 15:23:18 UTC 2015

```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
>>>> _______________________________________________
>>>> 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
>>> _______________________________________________
>>> 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
>>>
>>
>>
>> --
>> Andrew Koenig
>>
>
>

```