[Lowfer] modified Amrad active antenna details?

[Steve Ratzlaff]

Thanks, Jay,
Much appreciated.
73,
Steve

----- Original Message ----- 
From: <jrusgrove at comcast.net>
To: <lowfer at mailman.qth.net>; <steveratz at wildblue.net>
Sent: Monday, December 06, 2010 3:12 PM
Subject: Re: modified Amrad active antenna details?


> Steve
>
> Sorry for the delay ... got sidetracked with other projects.
>
> Well, like most things around here it's a work in progress. Here's the 
> latest iteration.
>
> 1)  replaced CP-666 with two J-310 in parallel - performance only several 
> dB short of CP-666 (looking for most recent IP2 and IP3 performance but 
> can't find it at the moment)
>
> 2) replace xfmr T1 with 38T bifilar FT-50-75 to better low frequency 
> response
>
> 3) replace resistor R2 with 22M resistor to better low frequency response
>
> 4) eliminate ferrite bead FB1
>
> 5) replace NE2 with gas discharge tube
>
> 6) power from solar panel / battery located at base of supporting 10' 
> mast - feed via transformer isolated dc injector
>
> 7) enclose preamplifier in shielded box - to eliminate interference from 
> 5kw FM broadcast station ~2000' away
>
> 8) use common mode choke (16T RG-58 FT-240-77) directly under shielded e 
> probe enclosure - to eliminate interference from 5kw FM broadcast station 
> ~2000' away
>
> If one isn't interested in sub 10 kHz performance or doesn't have a 
> broadcast station close by most of these mods aren't relevant. The solar 
> power / battery is the only way (at least at this location) to completely 
> eliminate power line related crud. An additional isolation transformer is 
> used before the feedline enters the shack. A preamplifier is used ahead of 
> the Delta 44 sound card to reduce it's noise figure. That's the setup at 
> the moment.
>
> Jay