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Re: Expected noise results with Drake converter (no satellite.)



I put in a 5 dB NF and 20 dB gain for your Drake, 1 dB of coax loss for your
25' run and a 10 dB NF for your FT-736R and a receive bandwidth of 2500 hz.
I put in 21 dBi for your antenna, subtracting 3 dB for it being linear to
circular. If these values are anywhere near correct, the results follow:

Your MDS (minimum discernable signal) is -136.4 dBm. The strongest signal in
the passband that is graphed is -133 dBm. So you will hear this VERY STRONG
signal on 3.4 dB above your noise floor. The strongest signal permitted is 8
dB below the beacon. The beacon is at -123 dBm. The loudest station should
not exceed -131 dBm. Since your noise floor is -136.4 dBm, the loudest
signal you should be able to hear will have a signal to noise ratio of 5.4
dB.

The Beacon should be 13 dB above the noise. You will hear only the very
strongtest of signals.

This was calculated at 65,000 km, or apogee, with 0 offpointing or squint
(antenna dead on). If there is any squint, you will have even poorer
signals.

Hope this helps ya.

hasan schiers, NØAN
schiers@netins.net

----- Original Message -----
From: "Al Lawler" <alawler@us.oracle.com>
To: <amsat-bb@AMSAT.Org>
Sent: Saturday, May 19, 2001 3:52 PM
Subject: [amsat-bb] Expected noise results with Drake converter (no
satellite.)


>
>   Configuration:
>
>   Ft736r -> 25' rg6 -> Drake(With "easy mods" -> 24dbi bbq antenna
> (and no satellite in view)
>
>
>    What should I expect to hear with the above configuration
> when I power up the converter?
>
> I'm not attempting to recieve any  satellites yet,
> and understand the importance of a preamp when I do,
> but for the purposes of debugging what I have built so
> far,  should I expect to hear a change in the
> "white noise" on the 2m reciever (tuned to 144.050 or so)
> when I power up the converter?  Are there any "birdies"
> generated by the converter which I might be able to
> tune to to verify whether the converter is working or not?
>
>
>   Thanks,
>
>   -al
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

----
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