Ham Radio - A 6 meter cage dipole using window line.

Ham Radio - A 6 meter cage dipole using window line.

 

I dont understand the purpose of the cage if it is only used at the lower 400 kHz of the band which includes all the common modes in use. FM is way up the band and in its own world.

My own 6M antennas have always been home brew including long boom yagis with at least a 500 kHz 2:1 VSWR bandwidth and the radios and amps are quite happy with it.

Carl

 

A solution looking for the problem.

 

I watched the video and thought if was interesting, he demonstrated that the cage dipole in this case did indeed have a broader bandwidth and would cover most, if not the whole band. His single wire dipole covered 2.6 MHz with a low SWR of 1.54, and the "cage" covered 4.6 MHz with the lowest SWR at 1.42. He was explicit about why he didn't personally retune it (has he was really only working the lower portion). Unless I'm missing something, the guy made a video explaining a concept, with examples, that he tested with a VNA as a demonstration. I'm new, maybe teaching people about RF concepts is out of vogue?

 

Thanks a lot for the video James! I found it very interesting and helpful. I am new to the hobby and I have been searching for homebrew/diy videos just like this. Great job explaining everything and showing exactly what you did. I really hope you do more videos like this and I am now following your blog too.

 

There is no need for a snotty comment, especially from a newbie who is totally unfamiliar with the item in discussion.
Ive nothing against new hams either, Ive mentored many over the decades.

Personally I just dont see the needs for repetitive YT videos when a Google will already provide far more info going back to the beginnings of radio.

Plus what wasnt mentioned is that the VSWR will change dramatically when wet, snow, and ice covered. I hope some dont blow their TX finals by not realizing this.

And yes Ive used the cage on 80 and 40M in the past to cover the CW and SSB/AM portions of the band.

Carl
Ham since 1955

 

Agreed, I should have left my editorial comment out of my reply. Although in fairness, you don't know what I may, or may not know about cage dipoles (not that it's relevant).

 

Cage dipole ABSOLUTELY had increased bandwidth compared to a single wire dipole. Well demonstrated in the video.
Hopefully, however, viewers don't get the impression that the increased bandwidth is useful on 6 meters where the activity is scrunched right around the low end and a simple dipole has way, way more bandwidth than needed.
The only ham bands that suffer from limited bandwidth of a single wire dipole are 160 and 80 meters. On those bands a cage can be useful if you can tolerate the weight and other physical difficulties in keeping it up.

 

The authors point was that the "Cage" dipole variant increases overall performance of a single wire dipole. In which he proves out with the tests he performed against a single wire dipole. More or less...

The take away point of the the cage dipole is that it generally nets you 1.7 times more bandwidth than the single wire dipole.

As my thoughts on the deployment of the cage dipole using window line. I totally dislike the idea. The added weight of the wire insulation is uncalled for and serves as a extra wind load.
There are better ways to deploy a cage dipole variant.

I guess though that for the experimental version displayed and intended build use for the author that stated that he is engaged in a perpetual camping trip. It serves up something. I could see that the man handling repeatedly might in this form of construction tend to be easier than perfect examples of the cage that I have witnessed being considered and constructed.


RRK

 

A rather complicated solution, too.

It seems to me that a very similar result could be had using 1/2 inch aluminum tubing, copper pipe, or even EMT conduit. A single 10 foot piece of tubing would provide more than enough material. A center insulator could be fabricated from PVC plumbing fixtures or a scrap of Corian or similar countertop material.

 

True....but his comparison was #18 wire!

In this particular case.

"Cage" dipoles are simply a way of getting the bandwidth of a thicker conductor with less material. For 6 meters thus isn't really an issue; a very similar result could be had with tubing that would result in a self-supporting antenna. Where "cages" make sense is on the lower HF bands. For example, a cage of about 3 feet diameter will give under 2:1 SWR over all 500 kHz of 80/75 meters, while a single wire might give 200 kHz SWR bandwidth if you're lucky. That's an improvement of 2.5 times or better.

Such as....tubing!

It's another example of how Amateur Radio antennas are much more about mechanical and material design than electrical design.

Exactly.

Of course there's also the use-what-ya-got factor too.

It should be remembered that another way to get more antenna bandwidth is resistive loading. The tradeoff is loss of efficiency. Maxcomm Matcher, anyone?

73 de Jim, N2EY

 

Perhaps, but being lightweight and durable for repeated man handling, I believe was the author's goal, where it was to be stored also I believe was considered.

I have to still scratch my head on the whole of this. I have my
6mtr rig attached to a dipole made of aluminum tape. Attached to a Fiberglass roof. Which is then attached to a LDG Z-100 plus
tuner and even more antenna like 2 or 3 ele Yagi, doesn't seem to be magical ingredient for convincing others that if you simply call CQ and burp alot into the microphone that they could end up with more station statistics than a boring day testing the vswr bandwidth and hoping that they will hear others doing the same thing.

So it's time to feed the fish again. And watch the 6m fish finder
and cross our fingers someone will actually want to use this apparatus for real...

Nope, that failed again. I will try driving another 500mi. And repeat the experiment.


RRK

 

That YT version is not even close to being called a cage, all it is is a pair of very close spaced parallel wires with its own set of problems as already mentioned.

A full size in the clear 80M dipole has a 2:1 VSWR bandwidth of ~ 150 kHz according to most reports Ive read from acknowledged experts who actually made the tests and are not just keyboard experts. Height above ground and surrounding objects can be modifiers. Expect half of that BW for 160 and double for 40.

Not wishing to deal with such a clumsy real cage structure for those bands I used a pair of dipoles, in a fan for both bands as inverted V's. Trimmed to my satisfaction they covered 3500 to 3900 kHz with the classic figure W 2:1 VSWR pattern which was fine as I rarely hear anything intelligent above 3900 plus my amp and rig can easily handle that slightly higher VSWR when needed.

I did similar for 160 using the same feed and the high end of the band VSWR was again manageable without having to waste money on a high power external tuner. My amps are tube type of course AND I dont forsee any SS amp in my future The complete antenna covers all the CW, SSB DX and casual QSO's with ease plus AM wherever it shows up. It also covers FT8, RTTY, etc frequencies which I dont bother with.

The highest VSWR on those bands adds almost no additional loss to the coax feed line and is completely ignored.

Carl

 

http://ocarc.us/docs/antennas/801203~1.PDF

free download.

This QST article from 1980 explains cage dipole principles. It shows how to estimate the 'equivalent diameter" effect of different numbers of elements up to six wires.

An article worth keeping in your files.