AmateurRadio.com

There are many challenges for today’s amateur radio operators. Low sunspots and poor propagation, Covid-19 virus limiting ham club meetings and normal fraternizing of local hams, HOA’s and other limits on outside antennas are real and must be dealt with. This also limits the help of ELMERS who can help new hams to understand how to cope with these problems.

One of the biggest problems is the limitations of apartment living. Many older hams have been forced to downsize as well as younger hams who cannot afford a single family home face these challenges daily. I hope I can provide some help for this challenge.

First let us consider the type of apartment. If a first floor apartment- consider moving. Really being on a higher floor is a big help with antennas. OK, well that can be dealt with anyway. Does the apartment have a balcony? How about a screened in porch. Are the windows small, or picture window size? Is there access to the roof? Are the walls concrete, wood or full of steel? Does the apartment management allow antennas? These are valid considerations and will affect antenna choices.

Not all antennas are equal. The half-wave dipole is the basis of comparison for antennas. Mobile whip antennas for HF are usually less than 20 percent efficient. However many apartment dwellers have operated using whips installed on their balconies.

Magnetic loop antennas of 1 to 3 meter diameters have been used successfully even they are about 40 to 60 percent efficient. Larger loops of 30 to 50 feet circumference can be used multiband operation with 60 to 80 percent efficiency. Fortunate amateurs that can install an end fed antenna can see 60 to 90 percent efficiency depending on the frequency of operation.

How does efficiency factor into antenna selection? The old saying “The bigger the better” certainly applies. Assuming a 100 watt transmitter, 50 percent efficiency would indicate a 3 dB loss of received and transmitted signal. Many sources state that the receiving station would hardly notice a reduction from 100 watts to 50 watts.

It is estimated that it takes a 6 dB reduction in transmitted signal for the receiving station to notice a change. Remember that a loss also means received signal loss so it affects your reception also. However, many stations operate successfully from apartments with QRP (5 to 10 watt) transmitters. So if you have a balcony where you can install an antenna, there are several choices.

Let’s review some of the issues facing apartment dwellers. Full size antennas for HF are not viable for apartments due to space restrictions.

Apartment antenna considerations

Size

This is one of the most important considerations. Area for antennas is limited and you will want to keep as low a profile as possible. Your neighbors and landlord may not appreciate the beauty of your ham antenna. Full size antennas are surely prohibitive.

Bands

A multiband antenna is probably the first choice. Of course if you have a single band transceiver, like many QRP radios, then a monoband antenna is good.

Ease of installation

You may want the antenna to be removed when not in use. A wire antenna should not be easily viewed when installed. Wire end fed antennas require a support at the far end. If possible, get the antenna outside.

Cost

The antenna should be the best possible at the least cost.

Location

Inside the apartment means the antenna is susceptible to local manmade noise and may cause interference to TV, Stereos’ and other appliances. The building will also affect the reception and transmission of RF signals depending on the materials of building construction. Installed on balconies it should not be visually offensive to neighbors. Remember, the further away from the building the better the performance of the antenna.

What types of antennas are possible

Mobile whips installed on balcony railings with a wire counterpoise have been used with some success. These are usually monoband antennas and have limited bandwidth unless they are auto-tuned screwdriver antennas. Those are expensive. Also remember mobile antennas are often only 7 to 12 percent efficient.

Small loops are a bit more efficient but again they are expensive unless you do make your own. Good variable capacitors used for tuning are expensive. Efficient loops require large diameter or cross section conductors. They work well on the upper HF bands.

Larger loops 0.10 wave length to ¼ wave circumferences have been used both inside apartment walls and around ceilings. These loops can be 40 to 60 percent efficient compared to a halfwave dipole.

I have used a loop 15 feet top and bottom and 10 foot sides for operation on 80 and 40 meters. Using 30 feet of wire works well for 40 and 30 operations.

MFJ sells a QRP tuner that suggests these lengths loops. They also have a 100 watt loop tuner and several other loop tuners.

MFJ makes an apartment antenna which is a base coil and whip with a mounting system. They work about the same as a mobile antenna.

They also make a bracket that holds two mobile whips to make a dipole.

Wire antennas can be dipoles, loops or endfed antennas. Usually there is insufficient room for half wave dipoles, except for ten meters. Shortened dipoles are possible but as the antenna gets shorter the band width get smaller. Many experimenters have found that the dipole as short as ¼ wavelength can be efficient if the RF can be matched properly to the antenna. Coils and traps add losses to the antenna.

Of course, if allowed, half wave antennas can be installed on the roof. Or they can be installed around the ceilings or walls of a room or in an attic space. “Slinky” toys have been used to make antennas also. They can be end fed with an unun balun and matchbox or using two to make a shortened dipole. They can be strung on a plastic line, pvc pipe or telescoping fishing pole. This makes them easily hidden when not in use.

Another possibility is a shortened dipole about 44 to 50 feet long, center fed with balanced feed line or two lengths of TV coax, using the center conductors as the feed line. The shields should be connected at each end and the shack end grounded if possible.

If each half is wound around a 7 meter telescoping fishing pole the antenna can be mounted on a balcony railing, pointing away from the building. This will make a multiband antenna for 40 to 10 meters. One half can be on the pole and one half hanging vertical also. Just make sure the hanging side does not hit apartments or people below. These antennas require a matchbox to feed RF from the transmitter to the feedline. The internal antenna tuners in most modern transceivers do not have enough range to match them on all bands.

End fed wire on a telescoping fishing pole. The far end hangs down.

End fed wires are possible using a 49 :1 balun and 33 to 72 feet of antenna wire. The wire runs from the balcony or window to a tree or support away from the building. The antenna should not cross any power lines or be where people can contact the wire.

Verticals or semi-verticals can be installed on balconies. Perhaps a 15 foot aluminum tubing vertical mounted on the railing with a 15 foot wire counterpoise hanging down fed with a tuner and short coax feedline or a balanced line. This should make a good antenna for 20 to 10 meters and possibly used on 40 and 30 meters with less efficiency depending on the tuner.

This is a DIY TAKTENNA with Petlowany coils on each end making a short vertical dipole.

Antennas for stealth, limited areas or apartments are a challenge but there are many ideas available on the internet. Just allow your mind to think out-side-the-box and visualize different antenna installations.

For more info and ideas on apartment antennas I suggest this URL:
https://officinahf.jimdofree.com/antenne-hf-mf/hf-antenne-da-balcone-1/

My thanks to the many that have purchased my new book: “Basic Wire Antennas for Hams and Preppers” as shown below. Send $5.00 US to my email address via PayPal for a PDF copy. W4BWS1 at gmail. com. More info at QRZ.com/db/W4BWS. Be sure to include your email address with the PayPal order.

As Rick Barrow, K3IW writes: Dear Dr. Don, Thank you very much, I enjoyed perusing your new antenna book. After reading it the work is worth more than five bucks, but I don’t know if youngsters read much these days versus watching YouTube instructional videos.