[amsat-bb] Re: Bob's Message

[Edward Cole]

At 03:34 PM 12/17/2007, Tony Langdon wrote:
>At 10:05 AM 12/18/2007, Nate Duehr wrote:
>
> >To keep the post on-topic, 100W and a single Yagi for moon-bounce!
> >
> >I remember reading about the Amateurs lucky enough to be able to work
> >moon-bounce prior to the advent of the PC-as-analyzer type technology...
> >Folks used enormous ERP and huge antenna arrays to work moon-bounce via
> >CW, before these recent advancements.  Now anyone with a tri-pod in a
> >backyard and a "brick" amplifier on 2m can work the moon, from what I've
> >been reading online.  It's probably time I give it a try, but I haven't yet.
> >
> >Amazing stuff.  Lots of neat work going on in the digital modes these days.
>
>Hmm, you give me hope I might be able to work moonbounce on 2m. :)  I
>have the power and the all mode radio, just have to dust off the
>antenna and setup the PC. :)
>
>73 de VK3JED
>http://vkradio.com

Realities of digital EME:

Yes, a single yagi can make contacts via eme.
You need a reasonably good computer with a soundcard interface to 
your radio (PSK-31 types work).
You need a RS-232 interface to your radio's PTT (and CW key for 
CW).  This can be as simple as some 2N2222's or better done with 
opto-isolated transistors.  Most computer grounds are incompatible 
with your radio gnd, so keep them separated.

When running a single yagi with low power (for eme) like 100-400w.  I 
will likely take a four yagi station to receive you.  You can be 
heard quite well if you run 1000w and a single yagi, but you will not 
find receiving a station similar to you, very easy.  This is because 
your receiving gain is inadequate.
Single yagis MUST have the preamp located at the antenna to hear anything.

I run 4 yagis but only 185w in the shack.  125w makes it to the 
array.  Single-yagi stations can be worked but it is very difficult 
taking sometimes several hour+ attempts to accomplish.  On the other 
hand I can copy a single yagi station quite well.

So if you can only get one yagi up, get the biggest you can handle 
(Cushcraft 13B2 is the very minimum).  And try to get more power so 
that more stations can be worked.  Eight yagi or more stations can be 
worked pretty regular by a single yagi station.

The goal is to achieve a minimum of 16 kW EIRP.

I have worked 115 stations on eme most using JT65.  Soon I will have 
a 8877 PA so my power will increase from 16.8 kW EIRP to about 65-70 kW.
Don't be put off by what I have said, though.  EME is within reach of 
any AO-10/13/40 equipped station.

Oh and yes the CW standard station is four yagis with 19-20 dBi array 
gain and 1000w.


73,
Ed - KL7UW
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  BP40IQ   50-MHz - 10-GHz   www.kl7uw.com
144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w
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