[hpsdr] Added Line-In Gain Selection of Janus/Ozy With SDR 1000

[joetorrey at cablelynx.com]

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I am going to use the control relay outputs from the "External Connector"
for selecting the "IF" gain. This will allow me to do this according to
the band used. The initial tests performed so far are very good; I figure
with the ability to do this by the band automatically will be even better;
I will even have another step in between by using the resistors in
parallel - this would give me a value lower than 1 kohm at the voltage
divider with both sets of resistors in parallel.

Joe
WD5Y


> I added the ability for selection of the Line-In gain by the selection of
> different pairs of resistors that make up voltage divider circuits at the
> Janus line-in unbalanced inputs behind the 39 kohm resistors before the
> Janus op amps. I read an article by John Eckert that he posted on HPSDR -
> 6/7/07. I used 1 kohm and 2.2 kohm resistor pairs. The selector switch
> used has two selections with center off which selects Janus mounted dpdt
> relays. This gives me the ability to select low (1 kohm), medium (2.2
> kohm) and high (off - single 39 kohm  @ normal unbalanced input)
> depending
> on the band and noise level. I tested other values and these seemed the
> best. John mentioned the use of the 1 kohm resistors in his article.
> Instead of just installing the single resistors I wanted the ability to
> choose basically the IF gain depending on the band conditions.
>
> Joe
> WD5Y
>
>
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