Help with Spider Antenna

I followed this guide and made the antenna in the photos. It is significantly worse than the default dipole antenna that comes with the RTLSDR.
What did I do wrong? I know I didn’t use the “F-Connector” in the tutorial, but I soldered the wires ( not well). Does that connector do anything or is it just a wire?
Thanks.

The F-connector is separating the core wire (in the middle of the spider antenna) from the spider legs.
By the look of you pictures you have the core wire and the outer mantle (that’s where the spiderlegs are connecting to) shortened by soldering all together.
This will give a very bad reception indeed.

You should make 2 solder connections:

  • 1 Center wire of spider to center wire of the cable
  • Insulate that from the outer mantle wit some form of electrical tape.
  • 2 Outer mantle of the spider to the outer mantle of the cable connecting to it.
  • Insulate the outer mantle with some tape.

When done check if the antenna is performing better.

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@Vexinglyvex
@tomvdhorst

No connector is required at top of Quick Spider, and no wire is is required to be soldered.

The F-connectoe is used at bottom of coax to connect it to the Dongle through a “F-female to SMA-male” pigtail or adaptor.

(1) The central whip is continuation of coax core wire with all insulation & braid strippe off

Central Whip - Quick Spider

 

(2) The radials are NOT soldered. These are INSERTED between outer jacket and core insulation of coax.

After inserting and evenly positioning the radials, two black plastic ties are used to secure the radials in position.

Radials inserted - Quick Spider

Yes I know that your design doesn’t need soldering at the top. Since he omitted the F connector and by judging the pictures provided it looks he shortened the bottom part towards the dongle.

Ca you please post photo of the part where you have soldered the wires? Thanks.

 

image

 

image

As well as the comments already made, you have the radials outside the outer sleeve of the co-ax, between the insulation and the tie wrap. They should be on the inside of the outer sleeve in contact with the braid.

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Sharp eyes @LawrenceHill. That is the main reason of bad performance.
I dont know why and how I missed it.

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Awesome thanks all. I’ll attempt those changes and report back.

Any tips for inserting the wire? It’s very tight

You could try to heat it up with a blowdryer in order to soften up the outer mantle. That might enable you to slide the radials in more easily.

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That’s the “What NOT to do” photo!

I would even angle cut the insertion ends of the ground legs to remove the blunt cut end and even add some dielectric grease to the insertion points.

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Alright got em in. Performance is still quite bad though.


@tomvdhorst @abcd567

Hi,

Looking at your original image in your first post, the far left 1/3 image shows where you have cut and soldered the connection between the larger coax and the very small coax that has the SMA connector for your receiver. That type of connection with center-to-center and braid-to-braid like that is probably not ideal at all.

You would probably be better off using a longer piece of the larger coax to make the antenna. Use one that already has an F connector attached. Then just use an F to SMA adapter plug at the dongle end for a much better connection.

You probably also don’t need the RF choke it looks like you have in the same image.

For a quick and dirty test antenna, just take an old TV patch cable with F connectors on both ends, and cut off one end connector to make your antenna there. You can also cut it in the middle to make two antennas.

The F to SMA adapters are very handy. You can get a simple adapter or a short pigtail. I use both types here.

Good luck,
-Dan

First of all, as a radio amateur, my hair stands on end when I read some of the answers here :face_vomiting:

Do you have a multimeter and a VNA? These are two important tools for construction!

For a layman, I would recommend the following instructions, and it is important to stick to the dimensions!

It is extremely important to make sure that you do not cause a short circuit, which means that the braid and the inner conductor (core) must not touch!

Use RG58 cable, a PL installation socket and at least 1.5²mm copper wire.

And with a little practice and manual skill, this antenna can be built in 5 minutes.

:rofl: :see_no_evil:

1090MHz