T2FD HF Antenna

[rinkerk]

Hello group,
I'm planning on building another wire antenna to play with.
I've seen alot of plans for this type and read alot of disagreements amongst SWLes and Hams alike.
Some say the "terminating resistor" between the upper element is essential for both TX & RX.
Others ( including commercially built T2FD's) dont use the resistor.
Then theres the question of lenght , baluns, spacing of elements and type/guage of wire to use.
Has anyone here actually built and used a T2FD desighn for a broadband HF antenna?
I know it's popular with people located in more populated areas where space and QRN is a big issue. Fortunately I live in an area that has moderate to liitle QRN at this time.
But thats going to change soon with encroaching development.
My Grandfather ( a silent key ) would roll over in his grave if I spent 300 bucks for a wire antenna.
Again this antenna would be for receive only. What's so dang special about this desighn that folks would spend $300-400 for?
( Warren, your more than welcome to chiime in on this. )
Cheers,
Kevin

 

[Arcticpeak]

This link will probably be of interest:

Notes on the Terminated Wide-Band "Folded Dipole"
http://www.cebik.com/wire/wbfd.html

 

[kb2vxa]

Hi ringkitk and readers,

Consider me chimed. (;->) Don't think "wideband" means multi-band, it's simply an antenna that has a shallower and broader SWR curve over a single band, rather unimportant when receiving. No matter how you lay it out, it amounts to a terminated loop, depending on design specifics it may also be unterminated. It's easy enough to build in it's many variations (and I mean MANY which makes a specific answer impossible) so with about $40 worth of parts you can save big bucks those with more money than brains dump down the toilet. I suggest moving to www.qrz.com since there are several threads archived discussing this and I have seen diagrams as well, just search them out and ask some questions.

Oh, that is if you can get their attention, they've got another war going with Hamsexy. (;->)

Oh, if you want to freak out your neighbors, put up a cage dipole. What's that? Oh, go look at some pictures of WW1 and WW2 warships. BTW, the Titanic had a Marconi T, another wideband antenna.

 

[jhooten]

Try to find a 600-900 ohm non-inductive resistor with a power rating equal to 60% of your transmitter's output. The are out there but they ain't cheap.

Then you need a 12to18(depending on the value of the resistor):1 balun cabable of handleing 120% of your transmitter's out put power.

And then the wire, spacers, rope, misc. small parts, and your time to locate all the above and put it all togeather.

The B&W produced versions are well constructed and a good value.

Just remember for transmitting half of your power is consummed in the resistor and not radiated.

 

[specman]

I've built one of these for SWL use. I tried the design with and without the resistor, and in my case the resistor made quite a difference.

Performance-wise I found this antenna to be excellent compared to a random wire, but you really need to get the "tilt" part right to see any benefit. In my case I was able to get an angle of about 30 degrees; when I strung up the unit as a flat top it didn't do much better than the wire. Plan for attaching one end on something high; the other end can be relatively low (I have mine strung between a tree and an 8' fence post).

I built mine from plans in a Monitoring Times article a few years back (or was it Pop Comm...) but there's plans all over the place for these. I used bare 14ga stranded wire and made the spacers/terminated resistor support/balun support from lexan. The balun was also homemade (no need for expensive transmitter type baluns for this).

Go for it! Cheap to build and performs quite well.

 

[rinkerk]

Thanks group for all your comments on this desighn,
Once we got it up in the air about 60' we could see little differnce in S/N Ratio.
I'm kinda thinking that a simple G5RV type dipole would work better and with out the extra weight.
This was an experiment into terminated folded dipoles.
The results were OK but we are thinking now that this type is no more " broad banded " ( with lesss noise ) than a simple G5RV desighn.
Anyway, We still experiment with this desighn. ( but not too impressed at this time )
Although certain receivers seem to favor this type, our experience to date still gives the same if not better rsults using a simple " longwire antenna tuner" et al; MFJ etc...........
Cheers,
Kevin

 

[BryanTheRed]

try the antenna forum!

 

[kb2vxa]

Hi Ringkirk and all,

The G5RV is simply a harmonic dipole with a twist, a matching section for 15M, the non-harmonic related band. It works reasonably well without a tuner, as well as any dipole, but a tuner still helps at the band edges where the SWR sharply rises. Somehow you and others haven't understood the difference between wide band and multi band as I have previously explained.

"try the antenna forum!"
Yeah, and get even MORE confused. No offense guys, but I have seen more misinformation there than you can shake the proverbial stick at. That's why I always suggest to do your own homework, study up on the basics of radio and antenna theory rather than paying TOO much attention to the myriad of personal opinions, mostly uninformed or misinformed. You WILL find sound advice on occasion but here you're barking up the wrong tree for the most part if you're really serious about radio communications rather than a casual hobbyist.

For what it's worth, THIS forum being devoted to HF is where you'll find more specific information than the antenna forum. There you'll find discussions about different antennas altogether, none of them having anything to do with HF.

 

[specman]

Uhmm, ya.

In any case Kevin, I'll have to agree that the G5RV may not entirely be suited for your purposes for the reasons previously mentioned. A lot of people also don't realize that the twin-lead "feedline" is a critical part of that antenna as well, and needs to be positioned as per the instructions.

If you have a tuner you can make the G5RV work for you; but I suspect using a tuner with a basic dipole at 60' or even a random wire may work just as well for your needs without the added expense.