[amsat-bb] Re: pre amp help..

[Edward R. Cole]

At 12:59 PM 2/16/2011, Ted wrote:
>I just sent my ARR pre amp back to ARR for repair for the 3rd time !
>
>(pretty sure I did not tx through it )
>
>What are people using for pre amps. I only see the Mirage as an alternative.
>Any other choices. I'm kind of disappointed in ARR products.
>Is there a pre amp that you can tx through preventing accidental frying?
>
>Any thoughts appreciated
>
>73, Ted, K7TRK
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Ted,

Not without relays to bypass the preamp when transmitting.  Several 
outfits make preamps with RF detect and internal relays but be 
careful not to exceed their RF power ratings.  ARR make a fine preamp 
and I have used them for years.  The mgf-1302 is the standard device 
in them but have become scarce (hard to find).  Not sure what ARR is 
using as a substitute, but you could stock up on a handful and do 
your own repairs.

I have been the beneficiary of a couple dozen H-J Fets (NE334S01) 
that drop into the ARR and have half the NF (typ. 0.24 dBNF). They 
are smaller devices so a bit harder to handle.  I just installed one 
in an old P144VDG ARR preamp and had only to substitute the 100-ohm 
resistor with a 270-ohm to supply Vds=2.4v (mgf-1302 take Vds=4v).

I will be installing it on my 2m-eme array in a couple days and will 
see how it plays.



73, Ed - KL7UW, WD2XSH/45
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