RCA All-Band Antenna

[Steve - K4HX]

In the November 1952 edition of the RCA Ham Tips there is an article, "An All-Band Antenna and Coupler" detailing an open-wire fed folded dipole system for 80/75, 40, 20 and 10 meters. A drawing from the article is attached below. I thought I would model this antenna to see what it does. The height of the top wire in the system was placed at 45 feet above ground. The results follow.

80m (3.8 MHz)

Z: 13.021 - i 55.526  TO: 90 deg  (omni)

40m (7.2 MHz)

Z: 719.940 + i 5809.200   TO: 18 deg at  90 deg az

20M (14.2 MHz)

Z: 1331.600 + i 323.650   TO: 24 deg @ 0 deg az

15M (21.2 MHz)

Z: 421.960 + i 1041.900   TO: 43 deg @ 0 deg az

10M (28.5 MHz)

Z: 486.720 + i 292.750    TO: 12 deg @ 36 deg az

The pattern break up is not bad on the higher bands. There are just two main azimuthal lobes on 40 and on 20 meters. Even on 15 meters there are only two, albeit at a higher than normally desired take-off angle. Finally, on 10 there are four major lobes. A regular 80 meter dipole would give you four major lobes and four minor lobes. The major lobes are far more narrow with a dipole than with the RCA antenna.

The patterns for each of the bands are attached. Note that on 40 meters the major lobes are turned 90 degrees from the rest of the bands (i.e. the pattern is in line with the wires instead of broadside or at right angles). The system is working like a pair of vertical here.

Another nice thing about the RCA antenna is that it's only 52 feet in length, so it's a nice options for those cramped for space.

Anyway, just something to think about for those who might be considering an 80-10 meter open-wire fed dipole system.

[W7TFO]

That is a wonderfully worthwhile antenna.

Thanks, OM

I wonder what the model would show if it were shorted at the top insulator and turned into a simple loop?

73DG

[Steve - K4HX]

Ran some sims with the thing connected as a loop.

80m (3.8 MHz)

Z: 2365.000 + i 14007.000  TO: 90 deg  (omni)

Wow! What a nasty impedance. About the same pattern but with a little more than 1 dB less gain, assuming you could match the thing.

40m (7.2 MHz)

Z: 225.180 - i 206.82   TO: 48 deg at  0 deg az

Pattern pretty similar to a dipole at about the same height. This arrangement would be better for stateside and local work and the folded better for DX.

20M (14.2 MHz)

Z: 114.890 - i 576.410   TO: 23 deg

Very similar pattern to the folded design, but with about 2 dB less gain.

15M (21.2 MHz)

Z: 439.570 - i 1048.900   TO: 18 deg @ 0 deg az

Six lobes, two major ones broadside and 4 more smaller (4 db down) of the sides. A couple dB more gain than the folded design and at a better takeoff angle.

10M (28.5 MHz)

Z: 747.160 - i 997.600    TO: 12 deg @ 36 deg az

4 big lobes, about 2 dB less gain than the folded design. But the lobes are larger and less pronounced nulls with the loop.


So, it seems for 40 and 15 meters the loop connection would be better for most instances (unless you wanted to work DX on 40 meters in directions 90 degrees to the line of the wires). Yes, the loop connection does have more lobes on 15 but the two main lobes are at a better takeoff angle. The difference between the two is about a wash on 20 and 10 meters, although the folded connection does have slightly more gain. The impedance on 40 and 20 meters is better with the loop connection and slightly better on 10 meters. The impedances are about a wash on 15 meters.

Being able to switch between the two configurations would be sweet.

[WQ9E]

Steve,

Thanks for posting this antenna info!  A friend just got back into amateur radio after a long absence and this may fit his area perfectly!  I will send him a link to this thread.

[W7TFO]

One might build the whole thing out of cheap RG-6 CATV cable;

Use the outer shields as the RF carrier instead of solid copper in the antenna and OWL, and use the center conductors as power for a suspended & sealed relay at the top to provide a switchable short.

Cheap and easy to build and source.

Maybe upsize it for 160 as well.

73DG

[Opcom]

Thank you Steve!

[W3RSW]

Looks like AHE's antenna, but I think his legs are longer than 26 ft.  ..maybe more like 40ft. Each.

Frank?

[W2PFY]

Is there a recommended spacing for the insulators at the top and for the feed line?

[Steve - K4HX]

AHE's antenna is 60 feet total length, 30 feet on a side. The spacing between the upper and lower wires is only about a foot though compared with 12 feet in the RCA design. His antenna operates very differently on 40 meters.

There is no recommeneded spacing. But given the drawing shows open-wire line, the spacing at the bottom would be about six inches. The insulator shown at the top appears to be the same size, so I would assume it's six inches. In reality, the spacing is not critical as long as no arcing or undue loss occurs with the spacer/insulator at the top.

[W2INR]

It would be interesting to see what that antenna would do with the length increased to include 160.

G

[W2PFY]

It would be interesting to see what that antenna would do with the length increased to include 160.

G

Hello Steve, could you model this to include 160? I think I want to put this up in the spring very deep into the woods at my camp. I could make my own transmission line mounted on trees using farm insulators and want to go back at least 1000 feet to possibly, keep out of one neighbors phone and radio. I'll be using # 12 insulated stranded wire throughout. Any thoughts?

[WBear2GCR]

Interesting... wonder if this would work as a phased array?

Putting two side by side would not take very much space...

Also, you could just run DC up the legs of the OWL to dump a relay, no?


                         _-_-bear

Getting the Z up a tad on 80m would be nice... wonder if dimensional changes have and effect, and how so...

[ke7trp]

Thats neat but the 12 ft spacing makes it dificult to throw this up. You would need two large supports. Maybe if you had the trees, otherwise two phone poles or two towers. You also need a robust balanced tuner. 

Franks antenna is just open wire line so that can be strung across the yard from any support. 

I would like to see the 160 info also.  Thanks steve for taking the time to model all of that.

C