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The ZS6BVR “End-fed” “SlimJim” as receiving Antenna for the SDR Receiver

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This antenna is designed to give you 3dB gain over a dipole and its omni-directional  for use with your SDR receiver

Its so easy to make antennas with different lengths

I used Banana sockets so you can make many antennas of different lengths for the different bands giving you gain as well as a frequency range

This antenna consists of two wires: a long one connected to the Black Banana socket
and a short one in front of that connected to the red Banana socket

The Slim Jim is a variation of the JPole antenna and my designed is the “End-Fed variation” of that.

To calculate the lengths we will give you a link below

I bought the Banana Plugs and sockets and ribbon cable at an Electroning shop the rest of the parts from Builders warehouse in prepacked “Ellies TV cables and connectors” bags

We will make the antenna
Step 1 terminate your ribbon cable with a pair of Red and Black Banana Plugs

Step 2 At a quater wavelength above the Red Banana Plug  (Length C in Calculator) cut a piece of the “Red line” to make a gap (Length E in Calculator)

Step 3 make the total length of the ribbon cable from the bottom of the Black Banana plug  (Length A in Calculator) and join the “Red line” to the “Black line” at the top:


Do not do this step until you have completed the housing you may need to add the length

We will make the antenna housing
Step 4 Drill two holes on the top of the box one nearest to you put the Black Banana socket the other place the red Banana socket

Step 5 Drill a hole on the side of the box nearest to you and mount the Coax Female-Female Barrel connector


Step 6 Make a cable with Coax Plug on one side  and  to the banana sockets on the other side The inner conductor is soldered to the red banana socket
the outer shield is crimped to the black banana socket  
Step 7 connect a “Ellies” cable from the coax socket to input of the SDR receiver

I have a space in the middle of the box for a wooden dowel  to act a support for hanging you antennas on it

The way I have made this box,  you can build other types of antennas to plug on this box

The M0UKD Slim Jim Antenna Calculator:
http://www.m0ukd.com/Calculators/Slim_Jim/   (Dont worry that they short the bottom of the antenna its because they are using a tuning stub for transmitter matching and we are connecting to it as “End fed”)

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Round 2 of 3d printer builds kicks off today

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Peter has been working day and night to prepare for round 2 of the 3d printer builds.  The first round saw most people completing PrintrBots and it seems that the Ecksbot has found some favour in this round.  There is also a couple of custom builts and hackers were given these four options when enrolling:

1.  Printrbot kit + course (same as first run but with version 2.0 parts.  All printed) – price will be a bit higher, as we are not going to do casting again.

2.  Prusa Mendel / Ecksbot kits + course:  A bigger, more mature printer – with hotbed, support for ABS or PLA printing, and a sturdier frame which should yield faster and higher quality prints.

3.  A bare-bones-kit option with Course/Consulting:  A full set of motors, extruder, hotend, electronics, belts, pulleys (upgrade to leadscrew at own cost) with consulting/training provided to help you design and build your own printer.

4.  A bare-bones-kit only:  No training, no advice, just parts:   Ideal if you have a bot and want to replica – gives you a chance to join the bulk-buy discounts.

In the end most people went with either 2 or 4, with some really interesting designs happening in the last category.

So, today is the start of the new builds and people posting on the list that it feels like christmas!  Peter posted some photos of the packaging and parts – all lined up and ready to be assembled – ready, set ….

 

 

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RTLSDR

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We ordered these Videomate U620F through PC Palace (ask for Pierre) in a group buy – 16 units for R180 per unit.

Inexpensive analog FM tuner stick

In order to receive Tuks FM 107.2 MHz using gnuradio, I followed these steps:

  1. Installed gnuradio using this script: wget http://www.sbrac.org/files/build-gnuradio && chmod a+x ./build-gnuradio && ./build-gnuradio
  2. Then followed the instructions here: http://sdr.osmocom.org/trac/wiki/rtl-sdr
  3. And finally downloaded multimode RX from here: https://www.cgran.org/browser/projects/multimode/trunk

When I connect the tuner stick, I get these messages in dmesg:

[ 7949.960326] usb 2-2: new high-speed USB device number 4 using ehci_hcd
[ 7950.105514] usb 2-2: New USB device found, idVendor=185b, idProduct=0620
[ 7950.105525] usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 7950.105532] usb 2-2: Product: VMU6xx
[ 7950.105539] usb 2-2: Manufacturer: Compro
[ 7950.105545] usb 2-2: SerialNumber: 0020

and lsusb gives me

Bus 002 Device 004: ID 185b:0620 Compro

Now running multimode.py, I changed the following settings to look like this:

  • The frequency to 107.2 (Tuks FM)
  • AGC is on – automatic gain control
  • Mode is WFM (80kHz)
  • Mute Threshold -41.6 (as desired)
  • Volume – pump it up!

Here is a screenshot of these settings:

Multimode.py tuned and listening to 107.2 MHz FM

Important you have to connect the antenna!

To get started here is some resources:

Videomate group buy

 

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