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Author Topic: New T2FD Antenna Construction and Performance  (Read 27130 times)

Offline Josh

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Re: New T2FD Antenna Construction and Performance
« Reply #30 on: August 06, 2019, 1951 UTC »
In the speriment it looks like 1680 is the only loser with the rest staying same or even increasing in gain.

Was just about to post some q for you too.

How does the T2FD noise floor compare to other antennae, such as your groundloop, skyloop, bev, perhaps if you have an active type. Say noise floor of each and signal level of the same signal on each ant at or close to the same time.
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Offline i_hear_you

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Re: New T2FD Antenna Construction and Performance
« Reply #31 on: August 07, 2019, 1200 UTC »
How does the T2FD noise floor compare to other antennae, such as your groundloop, skyloop, bev, perhaps if you have an active type. Say noise floor of each and signal level of the same signal on each ant at or close to the same time.

Enquiring minds want to know. I intend to raise a dedicated SWL antenna this fall along the edge of my property. The engineering and logistics of a T2FD is higher than for a dipole. Is it worth it?

Offline ChrisSmolinski

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Re: New T2FD Antenna Construction and Performance
« Reply #32 on: August 07, 2019, 1249 UTC »
How does the T2FD noise floor compare to other antennae, such as your groundloop, skyloop, bev, perhaps if you have an active type. Say noise floor of each and signal level of the same signal on each ant at or close to the same time.

I await funding for this experiment  ;D
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline ChrisSmolinski

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Re: New T2FD Antenna Construction and Performance
« Reply #33 on: August 07, 2019, 1309 UTC »
Enquiring minds want to know. I intend to raise a dedicated SWL antenna this fall along the edge of my property. The engineering and logistics of a T2FD is higher than for a dipole. Is it worth it?

My general experience with this T2FD is:

It works very well for the size. Performance is great down on MW, and up on 11 meters. If you have limited space and can only put up one fairly small footprint antenna, this may be the one. But you need to mount it nearly vertical (see below) for best results. This is good in that you don't need a lot of yard area vs a horizontal dipole. But you do need a tall tree, basically 85% of the length of the antenna assuming a 30 or 35 degree tilt from vertical. This means that in general you do not select the length of the antenna based on the band(s) of interest as with most antennas. Instead you find your tallest tree, get a rope over it, measure the length at that angle, and design your antenna appropriately.

It is not as good as a dedicated antenna for most single bands. My 43/48 meter band folded dipole wins on those bands, and nearby.

I *think* you want to mount it so that it is at about a 30 degree from vertical orientation, based on the signal plots in my previous post. I am not 100% sure the few dB of signal increase was due to the tilt, it is possible it was because the antenna was slightly higher overall. But further increasing the tilt angle *lowered* signal levels slightly, so I'd say I am 99% sure it was due to the tilt. I need to do some more experiments to see. Also this was on MW, it is possible results on HF are different. It's tricker to test on HF due to the typical fading of signals, longer measurement periods will likely be needed. But I think it's a safe bet that this is close enough to ideal.

It's not too much more difficult vs a traditional dipole. You do need twice as much wire and some spacers, I found 1" PVC worked great. And you want a 9:1 or 12:1 balun vs the usual 1:1 balun.  In one way it is *easier* than a normal dipole - you only need to get one end way up high in a tree, the other end is tied off at the ground. 

I am beginning to think two, or even four, T2FD antennas much be interesting for diversity reception. I had been considering doing this for some time using vertical antennas, but we know that traditional verticals, are, well, typically not as good (I am trying to avoid using profanity when describing vertical antennas) in the real world as theory suggests, mostly because you can rarely get a good enough ground system for them (unless your idea of fun is ripping up your yard to bury 50 or 100 or so quarter wavelength radials). But a few T2FD antennas is much easier to install. And they actually work!  :)
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Josh

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Re: New T2FD Antenna Construction and Performance
« Reply #34 on: August 07, 2019, 1816 UTC »
How does the T2FD noise floor compare to other antennae, such as your groundloop, skyloop, bev, perhaps if you have an active type. Say noise floor of each and signal level of the same signal on each ant at or close to the same time.

I await funding for this experiment  ;D

Check's in the mail.
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Offline i_hear_you

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Re: New T2FD Antenna Construction and Performance
« Reply #35 on: August 07, 2019, 1933 UTC »
I've tried using a slingshot and fishing wire to get rope up high, and it doesn't work out well for me. Do you have any advice in this regard?

Offline ChrisSmolinski

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Re: New T2FD Antenna Construction and Performance
« Reply #36 on: August 07, 2019, 1948 UTC »
I've tried using a slingshot and fishing wire to get rope up high, and it doesn't work out well for me. Do you have any advice in this regard?

That's exactly what I use, but I went with a heavier weight than what was supplied with the EZ Hang, I got some 2 oz weights from eBay, that helped with taller trees.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Josh

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Re: New T2FD Antenna Construction and Performance
« Reply #37 on: August 08, 2019, 0237 UTC »
Some HAMs swear by tennis balls in spud guns, with fishing line to start with.
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Offline JCMaxwell

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Re: New T2FD Antenna Construction and Performance
« Reply #38 on: August 08, 2019, 0446 UTC »
I bought a cheap child’s bow and arrow set and screwed a heavy nut onto the tip of the arrow. Then I tied a pull string right behind the fletchings and shot it over a limb. Then I tied the guy cord to the end of the pull string, pulled the guy cord and then attached the guy cord to the T2FD.
« Last Edit: August 08, 2019, 0457 UTC by JCMaxwell »
IC-R9000L, RSPdx, FDM-S2, IC-R30, BC125AT <- W6LVP

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Offline Pigmeat

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Re: New T2FD Antenna Construction and Performance
« Reply #39 on: August 08, 2019, 0506 UTC »
Wrist rocket, 1-2 oz. egg sinker, a good old Zebco 202 reel rewound with 60 lb. test mono, and you're in business. Stay away from sycamores, the things are killers. They're nice and tall with big branches high and in the open, but they're as hollow and punky as the trunks themselves. Quite a few people have been killed by falling branches strolling under them on windy days.
There's no way I'd try to haul a heavy antenna up one.

As far as launching antennas in trees, it takes practice. Those first few times are frustrating as it comes, as that weight you aimed at the branch in one tree goes sailing through five others to God knows where. It gets easier, but you'll still manage to screw it up now and then over the decades. Just remember to check what's downrange of where you're launching that sinker, a two oz. weight can be lethal at wrist-rocket speeds and it doesn't respect power lines. I don't think monofilament conducts electricity? I don't want to find out at my age.

Good luck, Young Edison!

Offline Stretchyman

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Re: New T2FD Antenna Construction and Performance
« Reply #40 on: August 08, 2019, 1100 UTC »
Ah ah! I'm going to use a DRONE to firstly survey the top of a very tall tree and then take a line weighted down up very high over the tree top and then land on my house roof.

Will let you know how it goes!

Str.
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Offline ChrisSmolinski

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Re: New T2FD Antenna Construction and Performance
« Reply #41 on: August 08, 2019, 1107 UTC »
Ah ah! I'm going to use a DRONE to firstly survey the top of a very tall tree and then take a line weighted down up very high over the tree top and then land on my house roof.

Will let you know how it goes!

Str.

I've considered the drone approach, let us know how it goes!
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Josh

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Re: New T2FD Antenna Construction and Performance
« Reply #42 on: August 08, 2019, 2115 UTC »
Meet the TL2V (Terminated Linear Loaded Vertical);

https://g8jnj.net/broadbandhfvertical.htm
http://www.tc2m.info/TC2M%20HF%20Vertical%20G8JNJ.pdf

More or less one half a T2FD with the other half grounded.
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Offline ChrisSmolinski

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Re: New T2FD Antenna Construction and Performance
« Reply #43 on: August 08, 2019, 2129 UTC »
Meet the TL2V (Terminated Linear Loaded Vertical);

https://g8jnj.net/broadbandhfvertical.htm
http://www.tc2m.info/TC2M%20HF%20Vertical%20G8JNJ.pdf

More or less one half a T2FD with the other half grounded.

I see it suffers from the "install a cumbersome ground radial system or suffer from poor efficiency" problem inherent with vertical antennas:

Quote
GROUND SCREEN. In order to operate in an efficient manner, this antenna (as is the case with all vertical monopole antennas) needs to be fed against an appropriately dimensioned ground screen (ground plane, radials or counterpoise wires). Ideally this would take the form of a continuously conductive metal sheet, extending out to beyond 1/4 of a wavelength at the lowest required operating frequency. However in most cases this would not be practical to implement.

Not practical. Quite the understatement  :P

Quote
The next best solution would is a series of wire spokes extending out away from the base of the antenna out to beyond 1/4 wavelength at the lowest required operating frequency. A minimum of 8 buried wires would seem to offer the best compromise between cost, effort and efficiency.

Eight quarter wavelength (minimum length) radials. Buried. Sure, let me get right on that.

Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Josh

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Re: New T2FD Antenna Construction and Performance
« Reply #44 on: August 08, 2019, 2346 UTC »
She got otherworldly hints on antenna design from astrologers, so she would know.
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