Building a Longwire antenna

Having just purchased an Eton G3 radio I wanted to get into Short Wave Listening a bit more. I am generally interested in NAVTEX, DGPS signals and Numbers Stations but the internal G3 bar type antenna just wont cut it.

I initially tried to just throw up a length of wire, stretch it out across the garden and straight into the G3’s ext ant jack (which is a 3.5mm mono jack by the way).  It kinda worked and I could hear a few more stations but it also pulled in a huge amount of noise generated by the nearby houses and electrical junk.

I decided it was time to string something up on a more permanent basis and started looking at end fed longwires, baluns, ununs, magnetic loops. The budget wont stretch to a Welbrook loop just yet so I set about creating a “proper” longwire install.

Here are my parts:

Starting from the top left we have:

  1. Ex MOD Racal antenna wire
  2. 1 x SO239 panel mount socket
  3. 2 x PTFE insulators from this ebay seller –
  4. Maplin project box – YN36
  5. 2 x small stainless steel hoops – from local boat chandlers
  6. 1 x small rope pulley – from local boat chandlers
  7. Insulated binding post – you need 2 but I cut this double on in half
  8. 9:1 unun kit for this ebay seller –
  9. 30cm of black plastic irrigation tubing

I also have a 12′ x 2″ alloy pole for the far end of the wire. The end attached to the house will be mounted just underneath my existing tri band collinear.

Step 1

I cut the irrigation tube in half and threaded it onto the end of the antenna wire pulling around 1M of wire through. I then passed the wire through the end of an insulator, and bent the irrigation tubing round using 3 cable ties to hold in position.

Step 2

The 9:1 unun was easy to construct using the included directions. I didn’t use the “choc bloc” connector in the end.

I took the project box, drilled holes and fixed the 2 binding posts and the SO239 socket in the best positions. I had a bit of a play with mine before I finally drilled and fixed them.

Step 3

The unun fitted nicely into the project box and I soldered the legs to the correct terminals. Red for the antenna element, black for the ground.

Step 4

I put a small bead of silicone around the edge of the project enclosure and put the bottom on. I used a couple of cable ties to hold the two pieces together while the sealant set.

Step 5

I am mounting the unun under my existing tri band collinear. To make it easier, I removed the stub mast from the collinear. If you are following this, you can mount the unun box however you like but it works well if you can mount it direct to a mast like this.

I drilled holes in mast and attach 1 stainless steel loop and the unun box using pop rivets. (sorry for the poor images, the camera died so I had to use my phone).

Step 6

I used a cheep snap link that I found to connect the other end of the insulator to the stainless steel loop. I then cut the 1M tail of antenna wire to length and connected it to the red terminal of the unun.

Step 7

I connected the black terminal to the stub mast with another rivet and a small round crimp. Then I wrapped both binding posts with self amalgamating tape and sealed the ends with a blob of silicone.

Step 8

I assembled the mast ready to go up to the roof complete with collinear attached. I have the mast mounted on a 6″ stand off bracket on the end of the house. The shack/office is directly below.

Installed on the roof.

Step 9

I wanted to be able to raise, lower and change the tension of the longwire so I fitted the other stainless steel loop and the small pulley to the top of the 12′ alloy pole using rivets.

Step 10

The 12′ pole is mounted onto the back of the garden shed. I threaded some small rope through the pulley before I pot the pole up.

I unwound the antenna wire up to the top of the garden and cut it about 1M short of the pole. I then used the other piece of irrigation tube and connected it to another insulator the same way as the other end. I tied the insulator to the rope and pulled the antenna wire taught. I then tied off the rope to the pole bracket.

Step 11

I fed the RG58 cable back to the shack and connected it to the G3 with a home made BNC to 3.5mm adaptor cable.

The results

I am very happy with how the wire performs. I have managed to get a 66′ length in the air and it has made a huge difference. The 9:1 unun seems to be doing its job very well as I have much less noise and can hear more stations.

As a comparison, I used “The Buzzer” station. With the internal G3 antenna I can hear it just through the noise with no signal level showing. On the end fed temporary longwire connected direct to the G3 I could hear it a bit clearer but the G3 was showing around +3 of noise. The new longwire with the 9:1 unun brings it in at +6 with the G3 showing no noise.

A great improvement and a job well worth doing.

3 Replies to “Building a Longwire antenna”

  1. How did you make your 9:1unun i can only put up 38 ft of long wire

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