[Lowfer] modified Amrad active antenna details?

[jrusgrove at comcast.net]

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





>> Hi Jay,
>> Last week I asked about details for the "modified Amrad e-probe" as mentioned on your VLF list. 
>> Someone else chimed in too, saying he'd like details also. I guess you missed those messages, or 
>> maybe I missed your reply, if given!
>> It would be nice if you'd reply to the lowfer list with those details (again?), and/or maybe put 
>> something on your webpage about what those mods are.
>> 73,
>> Steve