Tag Archives: Grayhat

From the CIA Archives: An HF Spaced Loop Antenna for Direction Finding

Many thanks to SWLing Post contributor, Grayhat, who shares the following:

I stumbled upon a document I found in the “CIA reading room”:

https://www.cia.gov/library/readingroom/docs/CIA-RDP76-00451R000200010013-1.pdf

In short, the document, titled “HF SPACED LOOP ANTENNA” and dating back to 1967, describes the design of a “direction finding” antenna used to find an HF transmitter. The document describes a number of setups tried during initial experimentation and then explains the reasons for the selection of what’s called a “Coaxial spaced loop in vertical opposition”, basically two vertical loops connected in anti-phase; the document describes in detail the loop and some circuitry used with it, but the most interesting section is the one which deals with radiation lobes. if you look at that you’ll suddenly realize using such a configuration, the resulting antenna acts as a huge dipole with extremely deep nulls !!

Fascinating! Thank you, Grayhat.

And, honestly, there’s enough material in that CIA document to please the most demanding of antenna nerds! Most impressive. I’m curious if anyone has ever built one of these. If so, please comment with your experience!

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Commercial circuit simulator, Micro-Cap 12, now a free download

Many thanks to SWLing Post contributor, Grayhat, who writes:

Maybe it’s old news for you, I just discovered it and thought you may
be interested, the commercial circuit simulator “Micro-Cap 12” which
was sold at around $4,500 for each license is now *free*, I found the
information here along with some further details:

https://hackaday.com/2020/01/08/commercial-circuit-simulator-goes-free/

The decision of releasing it as freeware seems to be related to the
fact that the company selling it (Spectrum Software) closed (not sure
for the reasons); anyhow, since the site or the download link may
disappear in some time, I think it would be a good idea to pick a copy
of the software, the full CD image including the program, libraries and
everything else can be downloaded from this page

http://www.spectrum-soft.com/download/download.shtm

Thank you for the tip! I agree with you about grabbing a full install of the application while you can!

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The NooElec Balun 1:9 v2

Many thanks to SWLing Post contributor, Grayhat, who writes:

Hi Thomas, was about to write you about some infos related to the NooElec balun when found that they now offer a v2 model:

https://www.nooelec.com/store/balun-one-nine-v2-barebones.html

The new balun has the same schematic as the previous one:

But it is slightly bigger, has a better connector for the antenna wires and (according to NooElec) uses a transformer which allows the tiny balun to work more efficiently from 0 to around 70 MHz (check out the charts found in the downloads section of this link).

The transformer used, judging from the pics, is a CoilCraft WB9-1, whose data can be found here:

https://www.coilcraft.com/wb_th.cfm

As I wrote the reason for this was the fact that a friend of mine reported that he used the (v1) balun with a Loop On Ground (LoG) Antenna !

If you look at the schematic (above) you’ll notice that there’s a “jumper” labeled R1 (zero Ohm resistor). That tiny detail is important, see, leaving the balun as is, it will work fine with a longwire, one just connects contact #1 to the antenna and #2 to a counterpoise or ground system and there he goes, BUT there’s another way to use the balun, that is, CUT the “jumper” (ok, resistor) labeled “R1”. If you cut it, the balun will become a 9:1 isolation transformer and with such a modification will work just fine with the KK5JY “LoG”
antenna: http://www.kk5jy.net/LoG/

According to what my friend reported, the balun works just fine, and although probably the ferrite core used in the V1 isn’t up to par with the original one used by KK5JY, the difference isn’t so huge.

Oh, and I also suspect that the modified balun may work fine with the KK5JY simpler passive loop http://www.kk5jy.net/rx-loop/ which may be a nice antenna for restricted spaces!

I think it may be of interest to people not knowing/willing to wind their own baluns, at that point one may just need an enclosure to protect the balun and putting up a receive antenna will be as easy as 1-2-3.

Thank you for sharing this! Readers: Grayhat has been encouraging me to deploy a LoG antenna at my home and I do plan to do so in the coming months. Please comment if you use a LoG similar to the KK5JY model and what your results have been.

Thank you again for the tip, Grayhat!

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Tips on receiving Lightsail 2 telemetry and CW ID

Many thanks to SWLing Post contributor, Grayhat, who shares the following update to our post regarding the Lightsail 2:

Some updates about the micro-satellite; first of all, sounds like it may be possible to receive the satellite CW beacon and FSK telemetry data using an SDR and a 70cm Yagi antenna, at least according to what is reported at the RTL-SDR website:

Solar Sail Satellite Lightsail-2 Now Transmitting Morse Code Beacon

Click here to read.

By the way, one will also need to be between 42° and -42° latitude to have some hope to pick up the satellite signal; also, the satellite now got a different NORAD ID (44339) so the N2YO tracking URL is now:

https://www.n2yo.com/?s=44339

The above may be useful to track the satellite and know when to attempt receiving its signals, other than that, the mission is proceeding well and the “mission dashboard” is now active:

http://www.planetary.org/explore/projects/lightsail-solar-sailing/lightsail-mission-control.html

The only missing bit for hams willing to track the satellite status is a piece of software to decode the telemetry data, whose format is publicly available:

https://planetary.s3.amazonaws.com/projects/lightsail/manuals/ls2-beacon-info-v01.txt

Also, given that, once the satellite will deploy the solar sail, its orbit will change, I think that it would be a good idea attempting to receive it now, since later on, it may become more difficult.

Thank you sharing these tips, Grayhat. I will attempt to receive the CW signal from Lightsail 2. I do miss one crucial element: the 70cm yagi. I’m willing to bet I know a local radio friend that has one, though!

If you successfully receive the CW ID or telemetry data from Lightsail 2, please comment and share your results here. A video or audio recording would be wonderful!

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