# [amsat-bb] Re: Arecibo on 432 MHz Moon Bounce (some calculations)

Nigel Gunn G8IFF/W8IFF nigel at ngunn.net
Wed Apr 21 05:00:02 PDT 2010

```The anomoly you see is because the 60dB gain given is dBi and the "real" gain used to calculate the power is dBd (gain
referenced to a dipole and not isotropic). The difference is around 2.4dB.

On 21-Apr-10 11:46, Fabio Azzarello wrote:
> Hello,
> thanks for the reply, but now I have another question.
> I'm not good enough with those numbers!
>
> If the calculated ERP is about 243 MW... which derives from changing from
> dBi to dBd (60dBi - 2.14),
> the part I don't understand is:
>
> "*Since the given ERP is 243,902,443 Million Watts (see below)
> and since 60 dB is equivalent to 1000000 (one Million) time in
> power it comes out that the power reaching the feed of the dish is:
> 243902443 / 1000000 = 243 watt
>
> The rest of the power 400-243 = 157 watt is lost in the feed line.*"
>
> How do they have feeder losses?
>
> 73s
> Fabio
> iw8qku
>
>
>
> On Wed, Apr 21, 2010 at 8:45 AM, Mateusz<sq7dqx at poczta.onet.pl>  wrote:
>
>>
>> 60dBi is abt 57dB
>> It means 10exp5,7
>> ERP was 400x10exp5,7 W
>>
>> ----- Original Message ----- From: "Fabio A"<iw8qku at amsat.org>
>> To:<AMSAT-BB at amsat.org>
>> Sent: Tuesday, April 20, 2010 8:26 PM
>> Subject: [amsat-bb] Re: Arecibo on 432 MHz Moon Bounce (some calculations)
>>
>>
>>   Hello all,
>>> just a curiosity, how did you found that the ERP is "... 243,902,443
>>> Million
>>> Watts".
>>>
>>> Thanks
>>>
>>> 73s
>>> Fabio
>>> iw8qku
>>>
>>> ----- Original Message -----
>>> From: "MM"<ka1rrw at yahoo.com>
>>> To:<amsat-bb at amsat.org>
>>> Sent: Wednesday, April 07, 2010 3:06 PM
>>> Subject: [amsat-bb] Arecibo on 432 MHz Moon Bounce
>>>
>>>
>>>   Hi all:
>>>> Here is a EME event you cant miss.
>>>> Dust off your CW key, its time for Satellite, QRP EME.
>>>>
>>>> The 1,000 foot dish has 60 dBi on 432 mc and 400 watts.
>>>> That comes out to be approximately 243,902,443 Million Watts ERP.
>>>>
>>>> enjoy
>>>>
>>>> wf1f
>>>> www.marexgm.org
>>>>
>>>> (thanks to KB1MGI for passing on this data)
>>>> ... snip ...
>>>>
>>>
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--
Nigel A. Gunn,  1865 El Camino Drive, Xenia, OH 45385-1115, USA.  tel +1 937 825 5032
Amateur Radio G8IFF W8IFF (was KC8NHF),  e-mail nigel at ngunn.net       www  http://www.ngunn.net
Member of  ARRL, GQRP #11396, QRPARCI #11644, SOC #548,  Flying Pigs QRP Club International #385,
Dayton ARA #2128, AMSAT-NA LM-1691,  AMSAT-UK 0182, MKARS,  ALC, GCARES, XWARN.

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