Balcony antenna

[Andrew (grayhat)]

Here's an antenna for the apartment dwellers, all one needs to install it is a balcony, the antenna is shown here



as you can see it's a loop, the antenna is made using thin insulated wire (1.5mm / AWG #14), at the center of the bottom side there's a small waterproof junction box hosting a NooElec 9:1 BalUn which then is connected to the coax going to the receiver, at the center of the top side there's a 1.5 KOhm resistor, the latter allows to flatten the impedance curve so allowing the antenna to offer a good match from a few KHz up to several MHz (at least up to VHF), the wire is suspended using some thin ropes or nylon tiers and, choosing a "neutral" color, the antenna will become almost invisible

Sure, it's not the best antenna in the world, but it may be a good alternative to an indoor antenna

HTH

[Omega-TI]

I'm going to build this one in the spring when the weather gets better due to the HOA's in my retirement complex. I mainly plan to use this from the 5-30 shortwave bands. So how long is too long for the wire length? I figure most of my listening will be in the 31 meter band.

[Egil - LA2PJ]

Forty years ago I lived for a year in a small flat on the third floor of a house with restrictions on antennas etc. So I made a similar loop antenna using 3mm copper wire. The circumference was about 9 meters, and I used a resistor of 1 kOhm. Antenna could not be seen from the ground unless you knew it was there, and was a very good receiving antenna. So for people living in such places I strongly reccomend it.

73'
Egil - LA2PJ

[Andrew (grayhat)]

I'm going to build this one in the spring when the weather gets better due to the HOA's in my retirement complex. I mainly plan to use this from the 5-30 shortwave bands. So how long is too long for the wire length? I figure most of my listening will be in the 31 meter band.

There's no "too long", the longer, the better performances you'll get on the lower frequencies, other than that the antenna impedance curve is almost "flat" due to the loading resistor, if you make it using insulated wire and choose some "neutral" color it will be almost invisible, at the top use a small box/enclosure hosting a "chock block" connector to host the resistor and at bottom another small box/enclosure to host the balun, willing to further hide the antenna, you may consider applying some artificial (plastic) climbing plant to the wire, in such a case, ensure those don't have any metal inside and consider that with rain/mist they may cause some issues to the antenna reception

As for the antenna pattern, it depends from the overall antenna perimeter (length), in general at low frequencies (say up to around 7MHz) it will be almost omnidirectional, going up in frequency it will have two main lobes perpendicular to the loop plane (that is toward front/back), going further up to V/UHF the lobes will be parallel to the loop (toward left/right), the gain will depend from the loop perimeter too, in general it will raise going up in frequency, but the performance should be more than acceptable w/o the need to use a preamp, the preamp may be only useful at the lowest frequencies

HTH and by the way, if/when you'll go on and build it, please come back and report how it worked for you !

[edit]

even if you'll be going to put the antenna together next spring, you may start collecting the needed bits and pieces, in particular the "NooElec BalUn 9:1 v2" https://www.nooelec.com/store/balun-one ... bones.html which is a nice one, stay away from chinese 9:1 since they're far than good; as for the resistor, ideally you'll want a non-inductive one, but a regular 1/4W, 1K5 resistor will be an acceptable compromise, as for the insulated wire, small enclosures, nylon cable ties and so on... those may be easily sourced locally at most home improvement stores

[Omega-TI]

Thanks for the reply and the very useful information!

I feel the same way about enclosing the resistor. In fact I'm going to go on the hunt for a .STL file for that purpose. I'm hoping to find something that I can feed the wires through on each side of the resistor to pick up the strain, and then be screwed to the back side of the eaves, with a cover to snap over that. That will give it a nice clean and tidy appearance.

Thanks for the heads up on the balun as well.

You bet, I'll be more than happy to come back and give a write up, complete with photos.

[Omega-TI]

I already found an enclosure for the balun you recommended.
https://www.thingiverse.com/thing:2152913

[Andrew (grayhat)]

I already found an enclosure for the balun you recommended.
https://www.thingiverse.com/thing:2152913

That enclosure isn't waterproof, you should use a waterproof enclosure for the termination resistor and for the balun, as for the latter don't connect the antenna wire directly to the balun, instead place the balun and a "chock block" inside the enclosure, connect the balun to the chock block with short wires and then connect the antenna wires to the chock block, so the balun won't be subject to strain from the antenna

[Omega-TI]

I already found an enclosure for the balun you recommended.
https://www.thingiverse.com/thing:2152913

That enclosure isn't waterproof, you should use a waterproof enclosure for the termination resistor and for the balun, as for the latter don't connect the antenna wire directly to the balun, instead place the balun and a "chock block" inside the enclosure, connect the balun to the chock block with short wires and then connect the antenna wires to the chock block, so the balun won't be subject to strain from the antenna

What do you think of this one? https://www.nooelec.com/store/balun-one-nine-v2.html It's only a couple of bucks more and is (for the most part) already enclosed. It could easily be attached with a 3M Command Strip.

These eye hooks look pretty good for the wire as well..

Eye Hooks.JPG (18.02 KiB) Viewed 2382 times

[Andrew (grayhat)]

The "enclosed" version of the NooElec v2 isn't waterproof, either, and weather/mist/rain will quickly damage the little balun, you want something like this (just an example)

https://www.amazon.com/LeMotech-Dustpro ... B075DHRJHZ

the box doesn't need to be big, since it will just host the balun and the chock block or (the other box) just the resistor(s), as for the eye hook, it's ok, but don't pass the wire inside the eyelet, suspend the wire using a loop made with nylon cable ties, antennas don't like metallic objects

A question, do you have an approx idea of the available size for the antenna (width, height) ? Subtract some inches from all sides to give the wires some clearance from walls and other obtacles

[Omega-TI]

"... suspend the wire using a loop made with nylon cable ties, antennas don't like metallic objects "

Yeah, but I'm trying to be as stealthy as possible. I think I'll go with a few 3D printed eyelets printed in the same color as the building.

Eyelet.jpeg (23.63 KiB) Viewed 2329 times