Fara-J fabric J-pole for 2m/70cm

[KL7MJ]

I saw a video for this antenna the other day https://vfcomms.com/shop/antenna/fara-j-antenna/
I've been building and using J-poles for over 30 years, and my favorite travel antenna for 2m/70cm was a J-pole made out of 300 Ohm twinlead. This is now my favorite travel antenna for my HT.
The price listed on the website is $70, but I built one for about $20 with faraday tape and ribbon that I bought online.
So far, it works great! I definitely am able to reach repeaters that I couldn't before, and it rolls up into a tiny roll, maybe 2"x4"x1" - the RG-174 coax that I use with it is a larger bundle.
If anyone is looking for a J-pole for their go kit, this is a great idea!

Mike, KL7MJ

P.S> Here are the SWR plots for 2m and 70cm:

[DanielM6KEC]

Brilliant idea.
Thanks for the idea.

[Andrew (grayhat)]

Now that's interesting; willing to improve gain you may consider using the same approach to build a so-called "oblong loop", basically you have a rectangle with the short sides at top and bottom, the sum of the short sides length will be 1/3 Lambda and the remainder 2/3 will represent the sum of the long sides length, the impedance will be around 50 Ohm and the antenna will offer two lobes with low takeoff angle

The attached pic shows a 433MHz version, but recalculating it for 144 or other frequencies won't be a problem, to tune it just shorten the vertical sides and move the horizontal one, once done it will be ready for use, notice that it can also be built using wire and two pieces of PVC pipe, in such a case when carrying the antenna, the wire can be wound around the pipes

oblong433.jpg (63.05 KiB) Viewed 3898 times

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[Andrew (grayhat)]

Just in case, the images below shows the "oblong loop" recalculated for the 2m band, sizes are in metric units, the model is for an antenna built using teflon insulated copper wire with 1.5mm diameter, and they should be used as a coarse indication, recalculating them won't be a problem, I think

download/file.php?id=180

recloop144_01.jpg (66.71 KiB) Viewed 3834 times

the antenna is calculated for a centerband of 146MHz and the "SWR bandwidth" extends from below 144MHz to above 148MHz with a bidirectional lobe offering a gain of more than 9dBi and low takeoff angle

download/file.php?id=181

recloop144_02.jpg (40.44 KiB) Viewed 3834 times

it may probably be built using the same approach of the one used for the J-Pole but offering much higher gain, although it won't be omnidirectional like the J-Pole, but that could be an advantage, I think

[edit]

And then, the antenna was also presented here

https://qrper.com/2023/11/a-portable-ob ... -2-meters/

HTH

[KL7MJ]

I don't think that design would work with the materials I used for the fara-J - the nylon webbing is only 1 1/4 inch wide. Maybe you could run two strips of nylon from a couple of spreaders though. The faraday tape is pretty cool.

[Andrew (grayhat)]

I don't think that design would work with the materials I used for the fara-J - the nylon webbing is only 1 1/4 inch wide. Maybe you could run two strips of nylon from a couple of spreaders though. The faraday tape is pretty cool.

I think the nylon webbing could be bought with the size one wants, then it would be a matter of applying the tape, the alternative (as I wrote) would be using insulated wires and a pair of thin PVC pipes, the resulting loop antenna could be wrapped as well and would offer much higher gain than the J-Pole