The AM Forum

When I look at old ham station photos, I see this big and beautiful cage dipole and end feed cage antennas.
My question is why don't we use these any more?
From the little I have found on the design, they are quite broadband, and aside from being somewhat of a challange to build, look great in the air!
I understand that W1AW installed one in 2005.

Any thoughts?

73 Bruce W1UJR

(http://www.smc-comms.com/images/antennas_masts/cage.gif)

High Maintenance? If a tree takes down a leg of your single wire dipole it's inconvenient but not too time consuming or costly to fix. I'll agree they're beautiful I was thinking of something like that myself but with limbs falling left and right around here I'd spend more time fixing antennas than using them. Of course I've got to get the ones I've got repaired and a transmitter on the air!

Hi Bruce,

Without researching all of the old QST’s, I would say that the cage is not for broad-banding but for lowering the losses in the electrically short antenna, which will have a high current feed point.  In the earliest days of licensed amateur radio the frequency was 200 meters.  Most people do not have the space for a half-wave at this frequency.  The hams probably followed what the professionally-engineered low frequency stations did for high efficiency.

They usually used an antenna tuner anyway, so I don’t think that broad-banding at the resonant frequency is necessary.  I have always considered an electrically short antenna as broadband in a way, since it is short and not resonant over a large frequency range, (R – jX) !

There has been some talk about cage antennas for those with short antennas and wishing to work 160 meters.  I don’t know anyone who runs a cage dipole though.  The merits are countered by the complexity and extra wind load and icing weight.

Read our other 2 discussion topics in the Technical section (titles may not be exact):
“60’ Flat Top for 160 and 75m” by Frank KB3AHE and “160 Meter Transmission Line Study: SWR and Losses”, by Tom WA3KLR (me).

There are significant losses in the ladder line, balun, and tuners in typical systems.  These areas need attention at least as much as the antenna.

    I suspect, with the 80M fone expansion, that there will be an increase in caged dipoles, bazooka's, open wire transmission lines, magnetically coupled transmatches,
and other broadband techniques.
    I have been having an absolute ball since the Bandwarming night! I use open wire with Kilowatt MatchBox and have no problem with VSWR.
    See you all over the Big 80M Band! ;D

I'm enjoying all the chatter from the "fan" dipole fans who insist that that is the cure-all. A lot of antenna designs are gimmicks which lower the Q and yield good SWR numb-ers. Most do it by wasting power. Now we have a wide band on 75/80. Time for open wire line and a good coupler. Saves a lot of time climbing too.   

I became a fan of cage antennas when I converted a single wire rhombic to a 2 wire rhombic.
It was a lot easier to tune and QSY.
John JN runs a 2 wire dipole. It doesn't have to be a cage just make multiple conductors.

I remember there was a nice cage on the roof of the russian embassy in DC. The commie lomo driver gave me a weird look when I was checking it out years ago. I had to stand in the middle of the driveway to get a good look at it.

Yep, I run a fan dipole fed with openwire.  I had a ton of wire and I thought the strategy of making the antenna conductors as large as possible to broaden out the thing was enticing so I did it.  I am by no means a vocal proponent of this antenna, as I don't know how effective it is compared to a normal flat top, but it works well for me.  I think the fan prolly does make a difference when I load it up on 160 with all that antenner current.  But who knows.

Dave, where is this discussion with the rabid fan dipole foamers?

QRZ.com

One day I was sitting in my Lab and the RF master walked in and asked us if we wanted to work on a little science project. He needed a 1 MHz antenna less than 2 feet high with the best possible efficiency. We set up a little range with a generator and tX ant so we could measure relative signals coming out of the RX ant. First we mounted a 2 foot rod to a box with a BNC and measured the signal strength. Then we wound an auto transformer to match the antenna to the coax. Result more signal. Next we placed a second vertical rod near the first. Yup signal came up. Last we did a 4 rod cage and again the signal came up even more.
The results were very convincing and gave us something to do that day. Old Hank scooped it up and was very happy with the performance.

Has it degenerated into a code/no-code debate, replete with accusations against others being CBers, etc?

If it hasn't, it most likely will in a couple of days.

I have used a "Three Wire Dipole" which is a form of the cage dipole concept....only uses 3 spaced wires that are shorted at the ends.  This antenna is found in many of the old handbooks.  I have found that it appears to be an extremely effective radiator and certainly operates over a wider bandwidth than a conventional dipole.  I use big open wire feeders (6" spacing) running directly down to a remote antenna coupler that is directly below the center of the antenna.  I then run coax from the tuner back to the shack.  There are probably a number of reasons why this antenna works well, but I have found it to be much better than my simple dipole fed with 450 ohm "brown line".

I don't know if the increased "capture area" is a contributing factor, however, I consistently get better reports with the larger antenna.  Now....as far as what I have seen in print regarding the theory....the primary reason for utilizing this type of antenna is increased bandwidth capability due to the effective larger size (cross section) of the elements.  I make no special claims...I am no antenna expert...and your mileage may vary....but mine works good.  Strictly from my empirical observations and actual on-the-air reports, I think it is a good way to go.   :)

73,  Jack, W9GT 

Of all the broad-banding techniques out there, the fat dipole idea is the oldest and the most proven. It doesn't achieve the wider bandwidth through any loss (other than the tiny amount from the additional conductors), like many others do (e.g. bazooka). Tons of empirical measurements have shown fat radiators to be more broadband than skinny ones, both for dipoles and verticals. A cage is just one way to produce a fatter radiator.

The old buzzard antennas Bruce is talking about may not have even been dipoles. The cage on top was just top loading for a vertical T radiator, often worked against a raised ground counterpoise system. These were high capacity antenna systems that worked well with spark transmitters. When tuned properly, the antenna systems and the tx coupler would form a fairly sharp bandpass filter. This would keep the spark signal from being hundreds of kc wide. If you want all the details, talk to Bob, W2ZM. Or get some old QSTs and read. It's fun.

I currently have a coax fed dipole cut for about 3815. I can span from 3700 to 3900 (maybe higher, never tried) without any problems. I think I get about 15-20 watts reflected in the 3700 range. But the TX system tuned up OK with no arcing. Since I don't have a very long run of coax, the small amount of reflected power doesn't appear to cause much loss.

Calculations show that even with a 4:1 SWR at 3.7 MHz, only about 0.8 dB loss (including the additional mismatch loss) is incurred with 100 feet of RG-213 cable. To put this into perspective, even with a perfect match, 0.36 dB loss would be incurred in the coax. So an addition half a dB is not enough for ME to worry about.

That said, an open-wire fed system with a tuner seems to offer the most flexibility. And if your TX system needs to see something very close to 50 Ohms to be happy, then this approach is probably required.

For now, run what ya brung and see how it works and where all the activity shakes out. Down the road, a new or different antenna system may be preferred.

Jack's three wire approach seems like an easy way to get some "fat" dipole enhancements without the mechanical complications of a full up cage. JN's two wire fan is similar. And with a pretty simple four way spreader at each end, two more wires could be added, and a cage would be had. The extra weight of the wire seems to be the detractor.

I guess getting back to the title of the thread, "Why Don't We Use Cage Dipoles Any More?", by far the biggest caveat is created by its advantage. The fact that you are using radiators that are large make it a greater target for high winds, icing, and the like. If you live in a (part) of the country that is neutral weather wise, I think it would be the ticket for broad bandwidth. However, in the sometimes not so great North-east, curtailing your operation due to ice build-up and spending effort re-stringing, repairing, elements can make it a real deterrent.

U nailed it Mikey!

I would think multiple support ropes, one for each wire would get around the ice load.