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VU3CER's HF Balcony-Antenna-System

VU3CER's 'HF Balcony Antenna System' is a Portable, Reproducible, 100% resonant, Simple, Stealth, Take + Erect Anywhere Antenna System. This Antenna System is built around an efficient, resonant, robust, convenient, and easy 49:1 EFHW (End-Fed Half-Wave) antenna at the core.

Supported bands: 40-20-17-15-10. No tuner required.

Motivation: The year is 2022, and property prices have risen to insane levels - new-generation HAMs with modest family backgrounds can't afford independent large row houses (bungalows) to install 128-element 180m (and all-band) beam antennas on. Furthermore, HOA / apartment societies (where many new-generation HAMs live) typically don't allow free access to the terrace. What can an enthusiastic HAM do in such circumstances?

Are you a new HAM trying to debug your equipment, and get on air within one day? We strongly recommend using the extremely popular and always-on FT8 digital mode for these purposes. Checkout the following URLs and projects as well.

Note: Please follow all safety precautions as always! Heights are DANGEROUS!

Big Picture Idea

Note 2: The screenshots folder contains the QSO reports.

Update (15-May-2022): The 'HF Balcony Antenna System' also works great as a simple 'Window Antenna System' (WAS). I simply flung the wire outside the window - no fishing pole or supports needed.

Jaipur RX (May-2022):

Jaipur RX

TX spread on the 17m band.

Proof of the pudding 0

Proof of the pudding 1

JP QSO.

Proof of the pudding 2

Note 3: The RX performance is Good Enough (TM) even on a First-Floor's Balcony.

Proof of the pudding 3

Some action on the 15m band as well ;)

Proof of the pudding 4

A WIP photo of the 49:1 transformer.

49:1 Transformer

SWR for 20m band.

SWR 20m band

Choosing a capacitor according to wattage (https://www.sotabeams.co.uk/efhw/):

Capacitor Choose

BOM

The total cost of this antenna system is ~1600 INR or less.

  • 10 meters RG-58 or HLF-200 with PL-239 connectors (10 meters is required even when 50 cms is enough!). For ensuring capacitive ground coupling! - 350 INR

    • BNC-Male to SO-239 adapter - 50 INR (required for IC-705)

    • https://www.rfconnector.in/ has the best quality + prices for all-things-RF. Do mention that VU3CER (Dhiru) sent you.

  • Caperlan First Fish 500 - 5m telescopic fishing pole - 650 INR from Decathlon.

  • Small PVC piece (~1m 1.25" SCH-40) to support the fishing pole [Optional] - Free from a local hardware shop with some communication skills ;)

  • Finolex / Polycab 0.75 sq. mm. PVC coated wire - ~10m meters (for 20m band, half-wave length) - don't cut the wire for fine-tuning - just roll the wire end in tight circles as needed. Yellow wire is more fun than Black - ~100 INR.

    Feel free to use 1 sq. mm. or thicker cables with due care.

  • 49:1 EFHW Transformer (FT140-43 core from Semikart + 19 or 20 SWG Winding Wire from Project Point + 100pF 3kV (or 2 kV) ceramic capacitor from Orbit Electronics) - ~150 INR

    Transformer parameters: 2 primary and 14 secondary turns with crossover wire - for 20m and up.

  • Enclosure: 'CircuitX Plastic Enclosure - Medium (PEM02)'. https://www.probots.co.in/plastic-enclosure-medium-pem02.html. 8.2 cm x 5.8 cm x 2.7 cm - 50 INR only

  • [Optional] IP65 Box - ~80x82x55 size works fine - smaller size is easily possible too. Bhadra Enclosures - BE-885 AS model - For outdoor use - ~200 INR

  • Misc hardware: Eyelet hook (M6 to M8 size works, other sizes are fine too) + double-screws + double-washers, Wing nut + washers + screws, SO-239 chassis mount connector - ~200 INR.

    • 0.75" round clamp with rubber cushion [Optional] - This can be useful for resting the fishing pole on the outer PVC pipe easily.

    • Bohri Ali (Pune): 'Ramanlal & Sons' + Burhan Hardware + 'Premier Hardware'.

    • Get from your local hardware market.

    Note: A regular lanyard cable works fine with the 'CircuitX Plastic Enclosure - Medium (PEM02)' enclosure.

  • Coax Common Mode Chokes (1:1). OPTIONAL (strongly depends on your operating conditions and setup)

  • Special DIY chippa for attaching and guiding the wire through the fishing pole - Make from waste plastic lid or something

  • Duct tape + plastic "packing wire" spool - required as always

  • For multi-band tuning, use a twist tie - details below ;)

  • For 40m operations, a DIY 34µH loading coil is required. See the References for details.

Note: See the images folder for sample BOM photos.

Tips

  • Raise the pole up at 45 degrees (or more) and drop down the remaining cable portion (if any) from the end of the pole.

  • The wire "exits" the 49:1 transformer, climbs up the fishing pole, and then drops down at the end of the fishing pole.

  • Don't worry about getting the exact parts (except the FT140-43 or larger 43-mix toroid), use what you have and feel free to modify this antenna system as per your requirements.

  • For making a QRO EFHW transformer, see the References section.

    BOM: 2 x FT240-43 toroids, 100pF 15kV (blue) ceramic capacitor, 10x10 cms box, 16 SWG enamelled copper wire (winding wire).

  • We recommend using NanoVNA to tune the antenna.

Observations

  • Tuning the antenna is trivial - few minutes + rough guesswork are more than enough.

  • SWR is not affected easily by surroundings.

  • No tuner is required nor recommended - resonant antennas rock!

  • The same antenna works fine for 17m, 15m, and other bands by adjusting the wire length. Don't cut the 10m wire (for the 20-meter band). Just roll the dangling end into tight small circles (using a twist tie) and get the antenna system to tune on 17m and 15m without problems.

    This no-compromise manually tuned multi-band antenna system gets your butt exercised as well :D

  • Pretty broadband even with 0.75 sq. mm. wire (~500 kHz with < 2.0 SWR) - this one is hard to explain, but I am not complaining.

  • TX efficiency is ~80%.

  • No problem of common-mode currents usually! This is where the 10-meter coax on the ground (aka "the floor") helps with.

  • SWR can be 1.04 even under non-ideal conditions. Don't be surprised by it.

  • This antenna system works fine with IC-705, and uBitx (well, no surprises here).

  • If your balcony is on the 25th floor, don't be surprised if you get DXCC within a week ;)

  • The same antenna design becomes a remote terrace multi-band antenna when used with 63-to-66 feet of wire. See the References for details.

  • Note: This proven antenna design is sold commercially by multiple vendors. It is NOT something new/novel (which is actually great!).

Comparison against Magnetic Loop

  • The VU3CER HF Balcony-Antenna-System can gain free space! - a magloop in a typical apartment balcony cannot do this.

  • We are able to achieve awesome SWR values (by gaining free space essentially). A magloop has a high (TX) SWR in typical, constricted (3 x 12 feet) apartment balconies.

    A perfect 1.01 SWR magloop may become 3+ SWR magloop in constricted spaces - well nothing new here.

    Buying a tuner for your magloop is not a solution - switch to VU3CER HF Balcony-Antenna-System instead ;)

  • TX efficiency of this system is way higher (on 20-17-15) than that of typical commercial magloops (AlexLoop, Chameleon offerings).

  • This antenna system can handle QRO levels of power (see References) - a typical commercial magloop (even costing 450 to 600 USD) can't do this.

  • Commercial and even homebrew magloops can be expensive - our antenna system is dirt cheap in comparison.

  • The constantly required manual tuning (required even within a single band) process for magloops becomes exhausting pretty quickly. They are known to have poor bandwidth on common HF bands.

    The VU3CER HF Balcony-Antenna-System has ~500 kHz bandwidth with < 2.0 SWR on the 20m band.

I have the Chameleon MagLoop(s) and some other ones as well - they were tested in the same balcony. I have lost interest in, and the love for magloops after testing the VU3CER HF Balcony-Antenna-System ;)

I wonder how a VHF magloop will work out... (aka a future project for fun).

FAQ

  • What can I do if my housing society (AKA housing complex) doesn't allow 'hanging' a fishing pole?

    You have various options:

    • Operate late at night - less chance of getting your antenna spotted.

    • Use a YouLoop / Magloop for RX - There are multiple ways to enjoy the amateur radio hobby - flexibility, and adaptability are biggest personal assets ;)

    • Operate from the field (SOTA + POTA). Also, operate from the field even if you have a 128-element all-band Yagi antenna at home - it's fun!

    • Icom AH-4 tuner with 7m+ of "random" wire might work better for you!?

    • Yaesu ATAS-120A Auto Active Tuning Antenna (only 1.6m long!) works decently enough if your balcony has the height advantage (like it is on the 30th floor).

    • On large balconies (with depth available), a RX/TX magloop could be a decent option. QRO magloops can be expensive though.

    • WebSDRs can be fun too for RX purposes - give them a try!

      http://websdr.org/ and http://kiwisdr.com/ are some good places to start.

    • VU2ASH's Indoor EFHW with only a few feet of wire going outside and around the balcony is another viable option.

      This antenna is currently being tested by VU2ASH (Ashok Joshi Sir).

    • VU2BGS has successfully used indoor dipole antennas in Indian hotels (which have the usual cement + steel based construction)!

    • Change your housing society ;(

References

Note: Construction of the EFHW transformer takes < 30 minutes. 'Installing' it takes less than 10 minutes. As usual, visualize the whole process in your head beforehand for 100% success.

Product URLs

Note: Select Element14 as the vendor in Semikart. We get pretty awesome prices in India for these two toroids. Also, Element14's packaging is quite perfect. Tip: Grow your Semikart cart over time to save (amortize) on the shipping costs (flat 250 INR). The delivery time from Element14 can often be under a week for Indian customers.

Note 2: Contrary to the popular pessimistic beliefs, toroids are easily available in India at pretty nice prices. Don't buy into these shared values of pessimism and defeatism - enjoy the hobby with a positive, resourceful mindset!