Cage Dipoles

[w8fax]

Some years back I made an injection mold for a ham that were designed for caged dipoles. It was his design, but I machined it in my tool and die shop. It produced a round disc about 5 inches or so in diameter. Ir had a hole in the middle and was about 3/8 or 1/2 inch thick. It had notches and/or slits in the outer diameter that would hold the wire pretty securely. The mold had an insert so that either 4 or 6 wires could be used. I lost track of that feller years ago, and never did find out if he was successful. Anyway, all that aside, I am thinking of machining up a few of these "spreaders" and trying to build a dipole. First off tho', I would be interested in hearing from anyone who has tried a cage. Is there more benefit other than bandwidth?? Here, ice is not often a problem, but I can see that one of these things iced up would surely test rope and wire. Anybody??? Thanks...Al/W8FAX

[WA3VJB]

Al I wonder if I might sign up for a few of those spreaders.

Been thinking along the same lines -- 4 wire doublet -- to try to cover "down low" on 80m as well as the usual haunt.

Have to load some figures into antenna modelling software to check the benefit ratio, but it's worth messing with.

http://www.smeter.net/antennas/wire-cage-dipole.php


http://amfone.net/Amforum/index.php?topic=9308.0

[W2PFY]

The only person I know running one of those antennas is Gary WA1OXT. He does very well with it.

[W2VW]

Al I wonder if I might sign up for a few of those spreaders.

Been thinking along the same lines -- 4 wire doublet -- to try to cover "down low" on 80m as well as the usual haunt.

Have to load some figures into antenna modelling software to check the benefit ratio, but it's worth messing with.

http://www.smeter.net/antennas/wire-cage-dipole.php


http://amfone.net/Amforum/index.php?topic=9308.0

If you are still running that 1/2" Foamflex for feedline simply dip that hollow state final to normal rated current and forget about goofy SWR lowering schemes.

[Steve - K4HX]

Dave nailed it. My dipole is cut for about 3800. I've used it at 3615 kHz with no problems. Is there some extra loss in the coax? Yes, but not enough to worry about and I'm only using RG213 - about  a whopping 0.3 dB. With lower loss coax it would be even less. If you are using 1/2" 75 Ohm hardline on a dipole cut for around 3800 kHz, the additional loss would only be about 0.25 dB at 3500 kHz. The additional loss at 3900 kHz would be on the order of a tenth of a dB. None of these are worth worrying about.

[WA3VJB]

But, but, more wire = better.

Well it's easy to talk me into not doing anything and then I have more time to be ON the radio rather than Robbin' Hoodin' it with the bow/arrow.

Or anything more elaborate.

[KM1H]

Ive yet to see a 80M cage ony 5-6" in diameter cover the full band.

I tried it in the 80's with phased verticals and wound up going with a 6 wire 12" diameter cage that worked great.

At that time I had to worry about VSWR as the CE-100V and NCL-2000 were both quite fussy, the latter just had a 3 section BCB type variable as the Load cap and blew it out some years earlier with a dipole and trying to contest and DX on both modes. Bought a MN-2000 tuner that National bought to evaluate with thoughts of making one.

If I was going to go thru the hassle of erecting such a heavy antenna Id try a T2FD as originally designed by the USN in the late 40's and not the garbage sold today. Only one support needed and about 110' long for 80-10M using 3 MHz as the low end.

[W3RSW]

And did it have that "magic" jug in the top middle and run less than 3:1 swr on all bands? Heh, heh.

[flintstone mop]

A side note:
There was an interesting article in QST about a dipole that can cover the entire 80M band.
It wasn't magic match or gimmicks. I thought it looked interesting. I would have to get atop my utility pole and mount another dipole bracket to accommodate another wire antenna.
MARCH QST has the article pg34.
Fred

[KM1H]

And did it have that "magic" jug in the top middle and run less than 3:1 swr on all bands? Heh, heh.

Well, there is a resistor there but it wasnt the dummy load of the recent commercial ham versions or the 20dB attenuation quoted by one well known "expert in everything". Try one before saying they dont work.

Hint: make it longer than the lowest TX frequency wanted and pay attention to the wire spacing and the formulas.

[Steve - K4HX]

I've used a 180 foot long version from B&W. It's OK. Nothing magical and about like a dipole at the same height but several dB down on TX. I don't see building one as being worth the effort. There are too many better options. But, if you can only put up one antenna, have to use coax and want all or nearly all HF bands, it's about the only way to do it. B&W sells it for a mere $1150.

[W3RSW]

Right Steve, was typing this as you responded.
It's 6 db down from a normal half wave at best. B&W duplicated it exactly with a lesser wire guage perhaps.

Recent QST article about it too.  Simple trade-off between ease of tune up for soldiers vs. antenna gain over a large band of frequencies.

Several threads mention this well hashed antenna.

[K1JJ]

If we choose to use coax and want to cover the entire 80 - 75M band, why not use a few fan legs?  Put up a set of legs for 3.875,  3.750  and 3.550 all tied to the same coax feedpoint.

It will need some pruning due to interaction, but should give a low swr on our favorite freqs of choice.


I've never actually tried it myself.    Has anyone tried- or modeled it?

T

** Late breaking JJ news:     My class E rig blew up yesterday.  Big time. It's toast, never to run again.  It also "somehow" took out the driver in my FT-1000D and my 1 watt ZLH-3A lab amp....  sigh.

[flintstone mop]

If we choose to use coax and want to cover the entire 80 - 75M band, why not use a few fan legs?  Put up a set of legs for 3.875,  3.750  and 3.550 all tied to the same coax feedpoint.

It will need some pruning due to interaction, but should give a low swr on our favorite freqs of choice.


I've never actually tried it myself.    Has anyone tried- or modeled it?

T

** Late breaking JJ news:     My class E rig blew up yesterday.  Big time. It's toast, never to run again.  It also "somehow" took out the driver in my FT-1000D and my 1 watt ZLH-3A lab amp....  sigh.

That's cuz you never gave IT a name....

[Todd, KA1KAQ]

** Late breaking JJ news:     My class E rig blew up yesterday.  Big time. It's toast, never to run again.  It also "somehow" took out the driver in my FT-1000D and my 1 watt ZLH-3A lab amp....  sigh.

WHAT??!? How can this be?? I thought one of the huge benefits to Class E rigs was that they didn't blow up? What's the world coming to?? 

(It was Fabio, in a fit of jealous rage)

I've always wanted to try a cage dipole or one of those old 4 wire folded(?) aerials from the 1920s with the big spreader at each end as seen on the early handbooks, hung from two masts. Just for the old buzzard look. I'm guessing there's a reason these configurations fell from favor.

[K1JJ]

Yep, Rico Suave is RIP.  There was so much popping and smoking that I didn't even try to troubleshoot it. It was the RF deck.  

I found a blown micro resistor on the FT-1000D driver board and repaired it FB.  The ZHL-3A lab amp has all its MosFet stages shorted. Hope the waranty is good... :-)

I'm now designing up a new all-tube PDM transmitter. Still have the big pdm coils from the old 4X1 PDM rig.


Cage Dipole:

Maybe the reason for the fade from fame is cuz  a full blown cage dipole can get VERY heavy - especially with ice loading.  I had one up and the pull was unreal.  Add in all the spacing insulators covered in ice along with six dipole wires...  We are talking hundreds of pounds of pull, especially if not supported in the middle.


T

[W1RKW]

Bummer on the rig Tom. Must have been a heck of a fireworks show.  FWIW, I blew up an O'scope yesterday when I fired up the 813 rig for the first time in a year. Not sure why it let go. It arced and sizzled and let out a huge cloud of smoke and set off a smoke detector.  Remember that high end audio company called SAE?  SAE stand for Smokes And Explodes.

I've thought about doing what you mentioned about varying lengths cut to the 75m band to broaden SWR.  I read somewhere many years ago about a ham who did just that and was able to get a more flattened SWR.  He ran co-ass. If I remember right he had 4 lengths all within  18 inches give or take a few inches of each other. Don't remember the dimensions. If I can find the write-up I'll post it.  Just have to remember where I found it. 

[W2VW]

If we choose to use coax and want to cover the entire 80 - 75M band

Small tuning unit on tower at or near feedpoint. Use cordless drill to drive variable components. make it interesting and don't bother with any position indicators.

The alternative is to put lots of wind load in the air.

Might be necessary in the 20s on the broadcast band to get those sidebands radiated but certainly not on 77.5 metres.

[KM1H]

I've used a 180 foot long version from B&W. It's OK. Nothing magical and about like a dipole at the same height but several dB down on TX. I don't see building one as being worth the effort. There are too many better options. But, if you can only put up one antenna, have to use coax and want all or nearly all HF bands, it's about the only way to do it. B&W sells it for a mere $1150.

At what frequency is it down "several dB"? It doesnt surprise me anyway since B$W has modified the original design and also uses stainless steel wire. It is not a true T2FD and the patent write-up containes a lot of drivel.

After using or just testing several B$W "baluns" and other items with ferrite when I was a distributor for them, I decided that old Elmer didnt have a clue.

Several threads mention this well hashed antenna.

And not one Ive found has built according to the T2FD design. Sounds like a real bunch of "amateurs" to me. Next you know everyone will be afraid to actually build things but will just repeat what they have read on the wunnerful World Wide Web of poor info.

Anyone have a big 600 Ohm non inductive resistor, 500W or more? I have a never used 450 Ohm 750W Carborundum to swap.

[KM1H]

If we choose to use coax and want to cover the entire 80 - 75M band, why not use a few fan legs?  Put up a set of legs for 3.875,  3.750  and 3.550 all tied to the same coax feedpoint.

It will need some pruning due to interaction, but should give a low swr on our favorite freqs of choice.

The inverted V on my 180' tower has wires for 160, 80 and 75. On 80 and 75 each is about 150 KHz wide between the 2:1 points. Since there is no intelligent life above 3900 it does well and the rigs plus amps load fine where it is higher such as 3885. Both wires are cut for the DX portions and 160 is at 1870 but I can load it all the way over the band. Coax fed of course.

[Steve - K4HX]

80 and 40 meters. Reports on 160 meters were closer to 10 db down. I think that's a bit on the high side and were probably more like 6 dB, at worst.

If someone was using the crappy brown stuff and a marginal tuner, the B&W antenna might not have anymore loss on some bands.

I've used a 180 foot long version from B&W. It's OK. Nothing magical and about like a dipole at the same height but several dB down on TX. I don't see building one as being worth the effort. There are too many better options. But, if you can only put up one antenna, have to use coax and want all or nearly all HF bands, it's about the only way to do it. B&W sells it for a mere $1150.

At what frequency is it down "several dB"? It doesnt surprise me anyway since B$W has modified the original design and also uses stainless steel wire. It is not a true T2FD and the patent write-up containes a lot of drivel.

After using or just testing several B$W "baluns" and other items with ferrite when I was a distributor for them, I decided that old Elmer didnt have a clue.

Several threads mention this well hashed antenna.

And not one Ive found has built according to the T2FD design. Sounds like a real bunch of "amateurs" to me. Next you know everyone will be afraid to actually build things but will just repeat what they have read on the wunnerful World Wide Web of poor info.

Anyone have a big 600 Ohm non inductive resistor, 500W or more? I have a never used 450 Ohm 750W Carborundum to swap.

[kb3ouk]

Yep, Rico Suave is RIP.  There was so much popping and smoking that I didn't even try to troubleshoot it. It was the RF deck.  

Get any pictures? Sure would be the start of a good crapout thread.