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P3 as a portable RFI bandscope?

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Jim AB3CV

P3 as a portable RFI bandscope?

I've pulled my P3 out of my setup to try and go searching for sources of
160/80m RFI.

I did a whole house shutdown today and made sure that anything which had a
battery was also shut down. That included the fire/burglar alarm system.
For the purposes of these two bands my house is "clean."

So now I need to do a walk around the area to see if I can locate the
sources.

I tried a little DC to daylight receiver with little success even with a
1ft diameter 2 turn loop for an antenna. The signals in question are too
narrow band and the receiver is too insensitive so the signals are buried
in noise.

I'm now trying to use the P3 in hopes that its signal processing and
averaging and ability to see a broader spectrum might be easier to use than
listening to a single frequency.

I tried the loop antenna directly into the P3 while powered on a battery
and it seems like I could use a bit of gain to get over the input noise of
the P3.

Have others tried this and if so what sort of preamp, antenna or other
setup was used?

Right now focused on 160 and 80m.

73

jim ab3cv
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Jim AB3CV

Re: P3 as a portable RFI bandscope?

I just realized I have an unused DXE RPA-1 which I could put in front of
the P3. Any thoughts on that?

jim ab3cv

On Sat, May 17, 2014 at 7:47 PM, Jim Miller <[hidden email]> wrote:

> I've pulled my P3 out of my setup to try and go searching for sources of
> 160/80m RFI.
>
> I did a whole house shutdown today and made sure that anything which had a
> battery was also shut down. That included the fire/burglar alarm system.
> For the purposes of these two bands my house is "clean."
>
> So now I need to do a walk around the area to see if I can locate the
> sources.
>
> I tried a little DC to daylight receiver with little success even with a
> 1ft diameter 2 turn loop for an antenna. The signals in question are too
> narrow band and the receiver is too insensitive so the signals are buried
> in noise.
>
> I'm now trying to use the P3 in hopes that its signal processing and
> averaging and ability to see a broader spectrum might be easier to use than
> listening to a single frequency.
>
> I tried the loop antenna directly into the P3 while powered on a battery
> and it seems like I could use a bit of gain to get over the input noise of
> the P3.
>
> Have others tried this and if so what sort of preamp, antenna or other
> setup was used?
>
> Right now focused on 160 and 80m.
>
> 73
>
> jim ab3cv
>
>
>

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Vic Rosenthal

Re: P3 as a portable RFI bandscope?

In reply to this post by Jim AB3CV

A reminder: Elecraft warned that the preamp in the P3 is sensitive to
static discharges, so be very careful connecting/disconnecting the P3 to
external antennas.

On 5/17/2014 4:47 PM, Jim Miller wrote:

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/

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dmb@lightstream.net

Re: P3 as a portable RFI bandscope?

In reply to this post by Jim AB3CV

Jim,

Per a previous recommendation from Elecraft, if you want to connect an
antenna directly to the input of your P3, you should put a pair of
paralleled diodes (in opposite polarity with respect to each other) across
the P3 input jack to protect the P3 from a static discharge.

I have used a small single-turn magnetic loop tuned to 40 meters to help
me isolate a noise source on 40m, and it worked very well. IMHO you really
need a proper magnetic loop which inherently has sharp and deep nulls to
be able to identify the direction from which the noise is coming. My 40
meter loop was 48" in diameter, and it worked fine without any additional
preamplification. However, for the same efficiency, an 80m loop would need
to be 8' in diameter which is a bit impractical to carry around. Although
I haven't tried it, I'm pretty sure that a 3' or 4' diameter loop tuned to
80m would still provide enough signal for the P3 and should exhibit very
sharp nulls to help you locate the noise source.

One other suggestion of an antenna that would be much smaller in size, yet
would still exhibit nulls is a small ferrite bar antenna similar to that
which is used in broadcast band (AM) radios. However, I have no experience
with that kind of receiving antenna.

Good luck w/ your noise sleuthing!

73, Dale
WA8SRA

> I just realized I have an unused DXE RPA-1 which I could put in front of
> the P3. Any thoughts on that?
>
> jim ab3cv
>
>
> On Sat, May 17, 2014 at 7:47 PM, Jim Miller <[hidden email]> wrote:
>
>> I've pulled my P3 out of my setup to try and go searching for sources of
>> 160/80m RFI.
>>
>> I did a whole house shutdown today and made sure that anything which had
>> a
>> battery was also shut down. That included the fire/burglar alarm system.
>> For the purposes of these two bands my house is "clean."
>>
>> So now I need to do a walk around the area to see if I can locate the
>> sources.
>>
>> I tried a little DC to daylight receiver with little success even with a
>> 1ft diameter 2 turn loop for an antenna. The signals in question are too
>> narrow band and the receiver is too insensitive so the signals are
>> buried
>> in noise.
>>
>> I'm now trying to use the P3 in hopes that its signal processing and
>> averaging and ability to see a broader spectrum might be easier to use
>> than
>> listening to a single frequency.
>>
>> I tried the loop antenna directly into the P3 while powered on a battery
>> and it seems like I could use a bit of gain to get over the input noise
>> of
>> the P3.
>>
>> Have others tried this and if so what sort of preamp, antenna or other
>> setup was used?
>>
>> Right now focused on 160 and 80m.
>>
>> 73
>>
>> jim ab3cv
>>
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

k5oai

Re: P3 as a portable RFI bandscope?

In reply to this post by Jim AB3CV

National RF makes a great portable unit that will work down to 1.8mhz

I have one of their units with the AA A B and C loops that cover
3.8-5mhz I see they now have a BB loop listed for 1.8-3.5mhz

Glad you brought this up I didn't know they had that new loop for
1.8-3.5mhz I'm will give them a call Monday morning.

HFDF active directional antenna system
http://www.nationalrf.com/type_hfdf_vector.htm

they also have a unit for the shack called HFDX Vector-Beam
http://www.nationalrf.com/type_hfdx_vector-beam.htm

usual disclaimer, just a satisfied customer.
--
GB & 73
K5OAI
Sam Morgan

On 5/17/2014 6:47 PM, Jim Miller wrote: