[RFI] Poor man's portable spectrum analyzer

[Dave Cole (NK7Z)]

Getting slightly off topic, this might help:

http://www.66pacific.com/calculators/small-transmitting-loop-antenna-calculator.aspx

73s and thanks,
Dave
NK7Z
https://www.nk7z.net

On 07/13/2018 10:22 AM, Charles Gallo wrote:
> On Fri, July 13, 2018 1:06 pm, David Eckhardt wrote:
>> I have never been able to display more than 8 MHz with the SDRPlays.
>> However, with the AirSpy using the SpectrumSpy application which comes
>> with a download of SDR#, I am able to display on one screen from roughly
>> 25 MHz
>> through 2 GHz.  Of course, you can display less if desired and zero in on
>> specific 'signals' when desired.  I have no connection with AirSpy other
>> than owning 3 of them.
>>
>> Dave - WØLEV
> 
> My question is not the SDR (I have one running), or even "How the heck did
> you get it running on an rPi (software etc) but...
> 
> I always see references to loop antennas, and have even seen a few links
> to plans.  They all use a variable cap to tune the resonance, but they all
> seem to use different values etc.
> Assume I'm going to a hamfest this weekend, and I'm walking around and the
> usual vendors have bins of variable caps, everything from small little
> things, to huge ones with 20-30 plates that look more like what you see in
> an amp or an antenna tuner.  They don't seem to have markings similar to
> what a fixed cap has (either XXXmfd/pdf or 103/104 - which I understand).
> How do I pick a cap, and if necessary, tweak the design of the antenna
> 
> Right now, I'm not very radio-active (need to get my replacement rotor
> installed, but I can get on 17m and 80m without that), but I like to help
> my friends with RFI.  I DO have various receivers, and even have an Arrow
> 2m beam and attenuator, but something for HF/MF isn't in my kit
> 
> 
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