Antennas for experimentation

[Grandchuck]

These antennas are interesting and are available for $2.39 plus shipping.  Amazon USA has them listed for $9.00 (Prime).

https://www.aliexpress.us/item/2255800677446691.html?spm=a2g0o.productlist.main.7.6b5c6fc9fzQ0K9&algo_pvid=1cd35da7-2dbc-44b4-bb5a-c45ec30cd8d4&algo_exp_id=1cd35da7-2dbc-44b4-bb5a-c45ec30cd8d4-3&pdp_ext_f=%7B%22sku_id%22%3A%2210000009701039767%22%7D&pdp_npi=2%40dis%21USD%212.5%212.37%21%21%21%21%21%402122457116686255270284599d0732%2110000009701039767%21sea&curPageLogUid=IdcTy0e3axNI

The first shot is the test setup using a nanoVNA V2+4.  The next one shows both sides of  the pc board and the size.  Last, the Smith Chart and the SWR are shown.

[joeqsmith]

These antennas are interesting and are available for $2.39 plus shipping.  Amazon USA has them listed for $9.00 (Prime).
...
The first shot is the test setup using a nanoVNA V2+4.  The next one shows both sides of  the pc board and the size.  Last, the Smith Chart and the SWR are shown.

That is pretty interesting.   I'll throw my ring into the hat with one I call Child's Toy.  For completeness, also shown are the Smith Chart and SWR.   Mine also make free energy from the Ether using what I call flower power.   

[joeqsmith]

Radiation pattern for Child's Toy.   While the SWR looks good it sure makes a poor radiator.   Who would have thunk. 

[joeqsmith]

My two pork & bean cans made a much better radiator....

[Geoff-AU]

I think the planar disc antenna is an unusual beast. 

My first attempt was here: https://thenack.com/2016/11/planar-disk-antenna/

I also made a little version from a 15x8cm protoboard (see attachments) that works above 600MHz

The pattern is like a dipole (imagine two very fat elements) at low frequencies and eventually becomes endfire-ish (imagine a bidirectional vivaldi) at high frequencies.  The lobes are a bit all over the place, so it's a matter of wiggling the antenna around to optimise the signal at the frequency you're trying for.

[aweatherguy]

The antenna posted by Grandchuck appears to be a variation on the well known bazooka dipole.

[Bud]

These antennas are interesting and are available for $2.39 plus shipping.  Amazon USA has them listed for $9.00 (Prime).
...
The first shot is the test setup using a nanoVNA V2+4.  The next one shows both sides of  the pc board and the size.  Last, the Smith Chart and the SWR are shown.

That is pretty interesting.   I'll throw my ring into the hat with one I call Child's Toy.  For completeness, also shown are the Smith Chart and SWR.   Mine also make free energy from the Ether using what I call flower power.

For our amuzement could you also make some fun of the modern cell phone antennas ?

[joeqsmith]

These antennas are interesting and are available for $2.39 plus shipping.  Amazon USA has them listed for $9.00 (Prime).
...
The first shot is the test setup using a nanoVNA V2+4.  The next one shows both sides of  the pc board and the size.  Last, the Smith Chart and the SWR are shown.

That is pretty interesting.   I'll throw my ring into the hat with one I call Child's Toy.  For completeness, also shown are the Smith Chart and SWR.   Mine also make free energy from the Ether using what I call flower power.

For our amuzement could you also make some fun of the modern cell phone antennas ?

This has been a serious discussion on experimental antennas.   I have never owned or had any desire to own a cell phone.  That said, I am working on a new design you may be interested in.  This is a transverse axial parallaxer, or TAP for short.  You can remember the acronym by Terrance and Phillip.

[joeqsmith]

The transverse axial parallaxer required a little bit of tuning.

Maple1 Smith Chart while adjustments were made
Maple2 SWR after adjustments
Maple3 Matching stub
Maple4 2D radiation pattern of the TAP
Maple5 3D radiation pattern "    "     "

Shows some directivity but doesn't radiate very well. 

[Geoff-AU]

I think the TAP is the first example of "antenna looks like its radiation pattern" that I've seen 

Great job

[joeqsmith]

I think the TAP is the first example of "antenna looks like its radiation pattern" that I've seen 

Great job

Countless hours of simulation and several layouts to get that just right....   

[tautech]

A J Pole is one of the simplest to make if you have some lengths of conductive rod in the workshop.
https://m0ukd.com/calculators/slim-jim-and-j-pole-calculator/

[joeqsmith]

Maybe just some wire would be even more simple?

[tautech]

Maybe just some wire would be even more simple?

Maybe but with lesser gain.

I did a 315 MHz J Pole a few years back and tuned it to better that 1.1 SWR which replaced a piece of wire jammed into the center conductor of a BNC socket.
I needed a keyfob transmitter to work reliably over 500 yds and that was achieved no problem.
The last adjustments to the J Pole to account for installation proximity effects was made while installing and measured from the end of the Coax feeder.
Wrote it up here:
https://www.eevblog.com/forum/rf-microwave/antenna-project-log/

[aweatherguy]

That's 315MHz, not 3.5MHz....right? Or did I miss something (I do that on occasion)?

[joeqsmith]

Another highly experimental antenna based on the "Slim Jim" called "Fat Bird".   Red traces showing the final result.

[joeqsmith]

Flying the bird upside down, it's more directional that I would have guessed.   

[tautech]

Flying the bird upside down, it's more directional that I would have guessed.   

That's still a good directional node just at 90 to the bird. 

A buddy that helped me on the J Pole journey instead simulated this for it as I needed omnidirectional sensitivity.

[joeqsmith]

Fat Bird 3D sweep.   

[joeqsmith]

My rotor and masts used to investigate these highly experimental antenna's radiation patterns.   

[joeqsmith]

In an attempt to replicate the nice torus shape,  I recycled Fat Bird and built a real Slim Jim.  Nothing I would consider experimental as it seems well documented.   To keep the size down, I target the 900MHz IMS band.   Using calipers and carefully measuring the lengths, when it was all done I had constructed a pile of crap.  Note my patent pending slide turning stubs used to overcome the problems.    The SWR is decent enough.

I started out running a 4 X 4 sweep (4 azimuth 4 elevations).  Antenna was mounted vertical and view is looking down towards the top of the antenna.   So we end up with a box with the lid sunk in.      Seems like a sort of doughnut.   

Next, crank up the resolution....

[tautech]

Note my patent pending slide turning stubs used to overcome the problems.

No, close up please.

I used double screw inners from electrical chocolate blocks (snap off joiners) with one fixing the feed point in position and the other screw shortened a little and a washer added to secure the feedline.
With patience this method allowed for quite fine tuning with a VNA although installation tuning is still required.

[joeqsmith]

No problem...  Shown mounted to the mast.   Adding a few more data points,  it does start to look like a doughnut. 

[tautech]

No problem...  Shown mounted to the mast.   

Ah OK you fixed the feed points and modified the Slim Jim gap. Fair enough.

[joeqsmith]

I was trimming all three which is why the solder was such a mess.  While D should have been 8mm, I am closer to 20mm.  I was told a year or so ago by a member that those three decimal places of perfect SWR are important.     Plot showing 10 deg resolution.  18X36 or 648 data points isn't something you want to take by hand.   It does appear the model you show would be proper for this type of antenna.