Re: [Discuss-gnuradio] Tuning in VLF with a sound card

On 05/15/2019 05:45 PM, Glen I Langston wrote:
> Hi Marcus,
>
> That's great. What could you hear/detect with the 90 kHz bandwidth?
>
> Glen
I used it strictly for SIDs in the VLF band up to 40kHz or so...

I had a loop antenna, about 1.2m diameter, and about 10 windings of
#20ga wire. No tuning capacitor.

>> On May 15, 2019, at 5:28 PM, Marcus D. Leech <patchvonbraun@gmail.com> wrote:
>>
>> On 05/15/2019 03:23 PM, Brad Hein wrote:
>>> Great suggestion thank you! This also gives me new topics to read up on as I am still a VLF amateur.
>>>
>>> [Sent from mobile device]
>> I used a Berhringer "mini-MIC" microphone amplifier, which has a balanced, XLR, input, and has bandwidth out to
>> about 90kHz. Worked a champ. Not as cheap as a DIY op-amp+transformer approach, but more convenient,
>> to be sure.
>>
>>
>>> On Wed, May 15, 2019, 1:20 PM John Coppens <john@jcoppens.com wrote:
>>> On Thu, 2 May 2019 16:22:24 -0400
>>> Brad Hein <linuxbrad@gmail.com> wrote:
>>>
>>>> I took a Raspberry Pi and attached a 48KHz USB sound card, with a big
>>>> magnetic loop antenna fed into the mic.
>>> Just a suggestion: If you have a loop antenna, which is a symmetrical antenna,
>>> and couple it to an asymmetrical input (MIC), you will make the antenna
>>> more sensitive to static noise. I'd suggest you use either a transformer or
>>> an 'instrumentation amplifier' with an operational amplifier to convert
>>> the signal from the antenna to asymmetrical signal.
>>>
>>> A transformer would be easiest to install at the base of the antenna (no
>>> need for a supply). The op-amp amplifier would cover a larger bandwidth.
>>> (it would also offer some protection for your computer).
>>>
>>> John
>>>
>>>
>>>
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