A Well Behaved Multi-Band Attic Aerial

Hello Fellow OM’s. I have been a ham since 1982 and have always operated out of apartments, condominiums and for the last 10 years, a single family home in a development with a very small back yard (with the obligatory sky high New Jersey property taxes!.) Over this time I have experimented many, many times with all sorts of antenna arrangements to get the best signal I could out to the ether. Such designs include:

-Rain Gutter end fed against radial wires

-Vertical loop antenna in a 23 ft. tall tree

-Cushcraft R5 vertical

-Attic dipoles fed numerous ways

-Magnetic Loop

I have written up some of my experiences with the above antennas in the past with some nice responses, with the hope any antenna restricted op may find some useful information for their own antenna installation. EHAM and the Internet are just FANTASTIC sources of information and ideas for antenna experimenting and I feel obligated to throw my 0.02 cents in as well.

Over the last year in particular I have experimented with building my own Baluns/Unun’s/ATU’s to feed both balanced and unbalanced antenna’s, with mixed results. Antenna Tuners such as parallel LC and Link-Coupled, built on some scrap wood in my garage have been tried, all in an effort to find that best arrangement of antenna and feed that permits GOOD multi-band operation. All this research and building has been lots of fun and quite educational!

As all these antennas are in close proximity to my operating position in my basement, RFI has been an issue. RF chokes from Radio Shack have been installed on all my computers, the family computers, the HDTV and the Home Theatre System. A 2.25” diam. Ferrite toroid proved the best RFI eliminator for my WiFi Router, located just 5 feet from my Transceiver in the basement. Wrapping the CAT5 cable between the Cable Modem and the wireless router around that toroid, really eliminated 90% of my RFI problems.

After all this work (and odd looks from my XYL and Harmonics!), one antenna arrangement has proven time and time again, to receive and transmit my pea whistle RF better than any other. Some have come close, but when JA’s are coming in over the pole, or Asiatic Russians are on the air on 20 metres, one antenna keeps pulling those signals in and keeps making the contact.

My present house is located on top of a small mountain in northwest NJ, overlooking a valley to my south/west. It’s a 2 story stick built home, roof apex at 27 feet. When I first moved in here in 2000, I immediately installed my G5RV Jr. dipole up there, knowing I may have to deal with HOA/neighbors who may not be antenna friendly. Fed with 50 ft. of RG8 coax, it worked/tuned well on 10/20/40 meters, a bit spotty on the other bands. It is too long to fit directly end to end so about 10 feet of each end is bent to follow the attic walls. From above would look like a Z. The attic is filled with insulation and wiring of course, along with my house Furnace! It’s tough to work up there so whatever changes I do make to that antenna, they better work!

In the past 6-8 months I have re-arranged the feed to that 52 ft. flat-top to improve multi-band operation. I have then done A-B comparisons to a Hustler BTV antenna ground mounted over 40 radials in my back yard. The vertical is about 15 feet back from my house, mounted to the kids play set with 40 radial wires. Time and again on 15/17/20/30 meters the Attic Dipole out performs the ground mounted vertical. What do I mean by out performs?

It means a DX signal is louder in my headphones and I can call the station and work them without much effort...thats what I mean…

I have operated in contests on 15/20 metres where JA’s would come in over the North Pole and barely perceptible on the vertical. But on the attic wire they were easy copy, and I would call them and get a report on the first try. I was needless to say quite surprised at that this past CQWW CW contest. The same applies to Asiatic Russion ops who come in late at nite on 20 metres, much easier to hear/work them on the attic wire.

I recently put in a QRP effort with the balanced fed attic dipole in the IARU HF Championship and worked EU - DX on all bands including 40 meteres (80M don’t work on this antenna BTW), and also logged a HI station on 15/20/40 meters. All with 5 watts…worked about 138 stations overall, plenty of 40 metre super stations heard my 5 watts in Europe.

RFI is non-existent with this balanced fed antenna. I would get RFI with some antenna arrangements, particularly on 17 metres BUT with the balanced fed wire, no such worries, no RFI issues at all in fact with any of the home appliances. Though obviously I pick up quite a bit of EMI but still, signals come in above the noise level no problem when bands are open.

So, how is this configured? Well any antenna is a “SYSTEM” and this system consists of 3 parts:

Fig. 1 Parallel LC Tuner with input 1:1 Choke
**Note: Coils built via K0FF article on eHam.net

Fig. 2 Feedline thru basement window

Fig. 3 Back of house to attic

Fig. 4 Attic shot, some metal and one wire leg

Fig. 5 Attic shot, can’t see it but center of dipole up there
Notice my furnace right near by!

I make no pretense this is some new, earth shattering antenna concept. It’s merely a compilation of my practical, real work operating experience with a number of popular restricted space antenna designs. Comparisons at my QTH keep confirming that this balanced fed antenna is superior to any nearby vertical antenna over a decent ground plane, or a vertical 20 metre loop antenna outside in my little 23 ft. tree, for bands 10-40 metres. Although a 20 metre magnetic loop I recently built has superior receiving capabilities, its TX qualities can’t nearly compare to this attic wire.

For the record, I have similar attic antenna results at 2 other QTH’s that were not on top of any elevated ground. I remember well my first 40 metre QSO into the Indian Ocean when I got my Extra Ticket back in 1995, a 3B8 station heard my signal, on a 52 ft. dipole fed with ladder line in my old condo attic.

Now, for 80 Metre operation my 6BTV using a 40 metre resonator and DX Engineering Cap Hat rods is the way to go!! But that’s another story.

I figured new hams who are stuck in situations where no outside antenna of any type are allowed, can have confidence an attic mounted balanced dipole will make plenty, and I mean plenty of exciting and rewarding contacts.

73 Gang

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