[Lowfer] modified Amrad E probe

[Zack Widup]

Thanks for all the info, Jay!

I have J310's in the TO-92 plastic case. Is the voltage and current in
this circuit set to the same values as the original circuit? Does the
TO-92 case sufficiently transfer the heat from the device?  I do have
a few U310's in small metal cans.

I have three AM stations in the vicinity: WDWS on 1400 kHz and WILL on
580 kHz, both about 3 miles away, and a weather/travel info station on
530 kHz about half a mile away. The weather station has never given me
problems but I have had some intermod problems in the past with one
circuit from WILL on my loop antenna.

On 12/14/10, jrusgrove at comcast.net <jrusgrove at comcast.net> wrote:
> Zack
>
>>Does this circuit use two J310's in parallel, or just one J310?
>
> One J310 will work ... or two J310 in parallel for slightly better IP2 and
> IP3 performance.
>
>> Also, the transformer in the original article was 17 bifilar turns.
>> This says "38T bifilar." Is that the same as 19 bifilar turns wound as
>> described in the original article?
>
> Twist up a length of bifilar and wind 38 turns of the bifilar on the core.
> There will be a total of
> 76 turns on the core if one were counting turns of the individual wires.
> Bifilar, trifilar,
> quadrafilar are always treated as if it were a single strand of wire for
> turns counting purposes.
>
> Note that the transformer and resistor change are to improve the low
> frequency response below 10
> kHz. If you're not interested in this frequency range there's no need to
> make those changes. The
> J310 or pair of J310s are a low cost substitutes for the CP666 FET and
> provide decent performance.
> If you live close to broadcast stations you might consider one of the e
> probes that uses an FET
> input stage followed by a push pull totem pole output.
>
> At this location I have the following broadcast stations (all line of sight)
> to contend with:
>
> WSNG 610 kHz 3 miles 1 kW
>
> WTIC 1080 kHz 11 miles 50 kW
>
> WJMJ 88.9 kHz 2000' 5 kW
>
> With either the single J310 or pair there are no noticeable IP2 or IP3
> products at this distance.
> Based on field strength measurements I'd *guess* that this e probe would be
> okay somewhat closer to
> a 50 kW station. Multiple high power stations nearby would make the IP2 /
> IP3 problem worse. This
> all assumes a 1 meter whip and that the antenna is mounted a *reasonable*
> height above ground.
> Raising the antenna increases signal strength - it is difficult at best to
> divorce the connecting
> feedline from acting as part of the antenna.
>
> Jay
>
>
>
>
>
>
>
> ----- Original Message -----
> From: "Zack Widup" <w9sz.zack at gmail.com>
> To: "Discussion of the Lowfer (US, European, &amp,UK) and MedFer bands"
> <lowfer at mailman.qth.net>
> Sent: Tuesday, December 14, 2010 1:24 AM
> Subject: Re: [Lowfer] modified Amrad E probe
>
>
>> I'm a bit confused. Does this circuit use two J310's in parallel, or
>> just one J310?
>>
>> Also, the transformer in the original article was 17 bifilar turns.
>> This says "38T bifilar." Is that the same as 19 bifilar turns wound as
>> described in the original article?
>>
>> 73, Zack W9SZ
>>
>>
>> On 12/13/10, jrusgrove at comcast.net <jrusgrove at comcast.net> wrote:
>>> Interested parties can find a schematic at
>>> http://www.w1vd.com/modifiedeprobe.pdf .
>>>
>>> Jay
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