T3FD

[NYG]

I currently use an EFHW and a multi-band dipole in an inverted V. I have the space and really want to experiment with antennas in the coming months. I keep going back to wanting to build a large broadband T3FD ( 120' - 200' in length) and a couple band specific dipoles.

Anyone have experience with a T3FD. Is it worth the effort before I start collecting components and materials?

 

[mmckenna]

I have T2FD's that we use for some HF flykits at work. They run in an NVIS configuration (center up about 15 feet, ends sloping down to just about ground level. They've worked well for that application. I've done a little bit of SWL'ing with them and they seem to work well. I have not tried them in any other configuration other than NVIS.

I have an end fed on a remote receiver at one of the high sites and it doesn't seem to work as well, but that may be entirely location related.

I don't have an HF setup at home, maybe when I retire, but the T2FD/T3FD antennas would absolutely be something I'd try.

 

[prcguy]

I once replaced a G5RV with a 190ft long T2FD and it was a little worse on 40m where I operated most but I didn't notice much difference on other bands except it didn't need a tuner where the G5RV could not operate without one. I could also operate 160m with the big T2FD although at about 20ft off the ground it was not good and no dipole on 160 would have worked at that height. The G5RV was mounted in the same location at the same height.

Not sure how a T3FD works in comparison, could be a little better match or a little more efficient but I wouldn't expect a huge difference.

 

[AK9R]

I have heard stories of the B&W terminated folded dipole antennas failing as a result of the resistor breaking down. What do the plans for the T3FD that you plan to build say about the resistor?

 

[NYG]

I have heard stories of the B&W terminated folded dipole antennas failing as a result of the resistor breaking down. What do the plans for the T3FD that you plan to build say about the resistor?

I don't have anything set in stone yet, however I'm looking for it to probably fall between 800 - 1000 OHM and able to handle ~1KW. Polomar sells them prebuilt for about $100 but I want to avoid that route for now as I learn more about the entire project and howe best to build my own. If I could find something ceramic and non-inductive that supports the requirements I'd probably get it. Most documents I've downloaded are related to two wire variants as opposed to three. But there seems to be decent information out there.

 

[NYG]

One thing I noticed when I started looking at these was that Bushcomm sells a ladder line kit to add NVIS to their antennas. If and when I do go forward with this I want to mimic that add-on kit from the start.

Bushcomm BU00625 Bushcomm OFO Wire Feeder Option and NVIS Kits | DX Engineering

Free Shipping - Bushcomm OFO Wire Feeder Option and NVIS Kits with qualifying orders of $99. Shop Ladder Line at DX Engineering.

www.dxengineering.com

 

[K6GBW]

I'm not trying to talk you out of this, but is there a reason you want to use the T3FD? The military and government use them for two reasons, the first is that they are very broad band. This allows them to change channels (yes channels because the government channelizes things for simplicity) and two for use with spread spectrum frequency hopping. The military and government usually are only using these antennas to talk 300 miles or so, so they don't care about efficiency. For hams that are usually competent enough to know how to select a frequency and use a tuner, there are much better options. I understand wanting to experiment though but just don't be surprised if you build it and it's not what you thought it would be.

 

[prcguy]

I'm not trying to talk you out of this, but is there a reason you want to use the T3FD? The military and government use them for two reasons, the first is that they are very broad band. This allows them to change channels (yes channels because the government channelizes things for simplicity) and two for use with spread spectrum frequency hopping. The military and government usually are only using these antennas to talk 300 miles or so, so they don't care about efficiency. For hams that are usually competent enough to know how to select a frequency and use a tuner, there are much better options. I understand wanting to experiment though but just don't be surprised if you build it and it's not what you thought it would be.

Yup, these antennas are lossy, around 5dB down from a resonant dipole but you have to give up something for the broad band properties. However, in most cases the loss can go unnoticed unless conditions are really bad.

 

[NYG]

I'm not trying to talk you out of this, but is there a reason you want to use the T3FD? The military and government use them for two reasons, the first is that they are very broad band. This allows them to change channels (yes channels because the government channelizes things for simplicity) and two for use with spread spectrum frequency hopping. The military and government usually are only using these antennas to talk 300 miles or so, so they don't care about efficiency. For hams that are usually competent enough to know how to select a frequency and use a tuner, there are much better options. I understand wanting to experiment though but just don't be surprised if you build it and it's not what you thought it would be.

There's definitely a lot of debate on the use/value of this type of antenna. The only way to really find out how it'll preform in my yard is to use it and tinker with it and do some comparisons. If in the end I find myself using other antennas much more often I'll lower it down and the wife can use it as a massive clothesline.

 

[K6GBW]

The only reason I say all this is because years ago I had the same idea. I thought, one antenna to rule them all! No tuning..etc. Well, it didn’t work out so hot. I’d try to talk to people about 100 miles away on 40m, a daytime shot that should have been easy, and it was a struggle. I swapped it out for a simple 40m dipole and it was like throwing a switch!

 

[G7RUX]

The T2FD and other travelling wave antennas are very useful and interesting bits of kit. They aren’t the most efficient but they are very useable. I had a 40m length one mounted flat at 35m agl and it worked really well, needed no tuner and survived horrible weather and sea spray for more than 20 years with a bit of maintenance.

Oh yes, I almost forgot. If you make it a decent folded dipole length on the lowest band you want to operate on, say 40m overall for an 80m operation, then you’ll get better performance on that band and the harmonically related ones with acceptable performance on the other Bands.