Re: [Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread Fred Jensen 
Not sure where he got the "chief use" from, all the T2FD's I've ever 
seen [and can remember] were transmit/receive, usually using KWM-2A's.  
But, yes, the amount of power dissipated in the termination depends on 
the frequency vs the overall length. We used them in the 60's in SE Asia 
and our maint depot guys would adjust the length so that the lowest loss 
areas were around our assigned frequencies which were generally in the 
2.5 to 10 MHz range, usually two of them [day/night], sometimes a third.


Same situation with the large V-beams and Rhombics in commercial 
servicewhich accounts for the land area occupied by a commercial MF/HF 
TX site: One V-beam does not fit all frequencies.


TheT2FD's sure beat a fan dipole since, once on the ground, we had way 
more important things to do than adjust antennas. [:-)


73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 8/13/2017 2:41 PM, Roger D Johnson wrote:
Cebik, W4RNL, modeled two versions of the T2FT. One 165ft long and the 
other 100ft.

Here is what he said about these antennas:

Terminator Resistor Losses
Although transmitting uses have been made of the T2FD, its chief use 
appears to be as a short wave reception antenna. In this application, 
the excess available receiver gain can largely make up for losses 
incurred in the terminating resistor.


The losses in the terminating resistor are considerable, ranging from 
nearly half power to amounts in excess of 90% of the available RF 
power. The pattern of losses is not a simple smooth curve, but varies 
throughout the operating range of the antenna. The following graph 
plots the losses in terms of dB. For reference, a 3 dB power loss 
represents half the power being dissipated in the resistor. Higher 
values indicate more of the power being dissipated rather than being 
radiated (or transferred to the receiver).


73, Roger


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[Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread Roger D Johnson 

Cebik, W4RNL, modeled two versions of the T2FT. One 165ft long and the other 
100ft.
Here is what he said about these antennas:

Terminator Resistor Losses
Although transmitting uses have been made of the T2FD, its chief use appears to 
be as a short wave reception antenna. In this application, the excess available 
receiver gain can largely make up for losses incurred in the terminating resistor.


The losses in the terminating resistor are considerable, ranging from nearly 
half power to amounts in excess of 90% of the available RF power. The pattern of 
losses is not a simple smooth curve, but varies throughout the operating range 
of the antenna. The following graph plots the losses in terms of dB. For 
reference, a 3 dB power loss represents half the power being dissipated in the 
resistor. Higher values indicate more of the power being dissipated rather than 
being radiated (or transferred to the receiver).


73, Roger


On 8/13/2017 3:36 PM, Fred Jensen wrote:

Ummm ... let's be truthful here.  The B folded dipole can be found in radio catalogs from 
the 50's.  We all knew [I was a kid with a new license then and even I knew] that the doohicky at 
the center of the top wire was a 400 or so ohm non-inductive resistor, and half the power [3 dB] 
heated it up.  There was no subterfuge and B wasn't "conning" anyone, it was very 
clear in the specification sheet.  300 ohms at the feed point, hams often fed them with 300 ohm 
TV twinlead of the day to a balanced link coupled to the final tank circuit.  A 4:1 transformer 
netted 75 ohms which nicely matched that twinlead too.







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Re: [Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread n4xy 


I have an NOS stainless steel version of the 160M B antenna that I bought 20 
or 30 years ago. Now I can't put it up because I don't want to interfere with 
the pattern of my HyGain HyTower. If anyone is interested in it, just send me 
an email. It will not be inexpensive. Thanks. 


Sent from my Verizon, Samsung Galaxy smartphone

 Original message 
From: Barry <k3...@comcast.net> 
Date: 8/13/17  4:59 PM  (GMT-05:00) 
To: Dave Heil <k...@frontiernet.net>, elecraft@mailman.qth.net 
Subject: Re: [Elecraft] B Folded Dipole over an Armory 

Dave,
 They are used by a greater number than just state. The military, 
all, are using HF ALE. It's used because, you are correct about 
operators, a link can be set up by just IDing with whom you wish to 
talk. The radios run up and down the spectrum until they find each other 
and can make a solid linkup. No antenna is flat across that much 
spectrum, so in recent times, the T2FD has been employed. It seems 
auto-tuners don't keep up with the sounding rate from some of these 
radios. It was interesting to me to see the magnificent antenna field at 
Rockwell-Collins in Iowa augmented with a T2FD so that they could do 
work with their ALE radios. Harris Corp. does the same.

73,
Barry
K3NDM

-- Original Message --
From: "Dave Heil" <k...@frontiernet.net>
To: elecraft@mailman.qth.net
Sent: 8/13/2017 4:03:25 PM
Subject: Re: [Elecraft] B Folded Dipole over an Armory

>The U.S. Department of State uses many of these B folded dipoles in 
>Africa and other nations with HF transceivers meant to be used by those 
>with little or no radio operations experience.  All the user needs do 
>is consult a list of places and frequencies (which are all programmed 
>into memory), key the microphone and talk.  These antennas weren't made 
>to work DX and neither were the transceivers.  Any easy way to make up 
>for the inefficiency is to switch on one of the 500 or 1000 matching 
>amplifiers, none of which requires manual band switching or tuning up.
>
>Dave K8MN
>
>On 13-Aug-17 19:36, Fred Jensen wrote:
>>Ummm ... let's be truthful here.  The B folded dipole can be found 
>>in radio catalogs from the 50's.  We all knew [I was a kid with a new 
>>license then and even I knew] that the doohicky at the center of the 
>>top wire was a 400 or so ohm non-inductive resistor, and half the 
>>power [3 dB] heated it up...
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Re: [Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread Roger D Johnson 

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Re: [Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread Barry 

Dave,
They are used by a greater number than just state. The military, 
all, are using HF ALE. It's used because, you are correct about 
operators, a link can be set up by just IDing with whom you wish to 
talk. The radios run up and down the spectrum until they find each other 
and can make a solid linkup. No antenna is flat across that much 
spectrum, so in recent times, the T2FD has been employed. It seems 
auto-tuners don't keep up with the sounding rate from some of these 
radios. It was interesting to me to see the magnificent antenna field at 
Rockwell-Collins in Iowa augmented with a T2FD so that they could do 
work with their ALE radios. Harris Corp. does the same.


73,
Barry
K3NDM

-- Original Message --
From: "Dave Heil" <k...@frontiernet.net>
To: elecraft@mailman.qth.net
Sent: 8/13/2017 4:03:25 PM
Subject: Re: [Elecraft] B Folded Dipole over an Armory

The U.S. Department of State uses many of these B folded dipoles in 
Africa and other nations with HF transceivers meant to be used by those 
with little or no radio operations experience.  All the user needs do 
is consult a list of places and frequencies (which are all programmed 
into memory), key the microphone and talk.  These antennas weren't made 
to work DX and neither were the transceivers.  Any easy way to make up 
for the inefficiency is to switch on one of the 500 or 1000 matching 
amplifiers, none of which requires manual band switching or tuning up.


Dave K8MN

On 13-Aug-17 19:36, Fred Jensen wrote:
Ummm ... let's be truthful here.  The B folded dipole can be found 
in radio catalogs from the 50's.  We all knew [I was a kid with a new 
license then and even I knew] that the doohicky at the center of the 
top wire was a 400 or so ohm non-inductive resistor, and half the 
power [3 dB] heated it up...

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Re: [Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread Dave Heil 
The U.S. Department of State uses many of these B folded dipoles in 
Africa and other nations with HF transceivers meant to be used by those 
with little or no radio operations experience.  All the user needs do is 
consult a list of places and frequencies (which are all programmed into 
memory), key the microphone and talk.  These antennas weren't made to 
work DX and neither were the transceivers.  Any easy way to make up for 
the inefficiency is to switch on one of the 500 or 1000 matching 
amplifiers, none of which requires manual band switching or tuning up.


Dave K8MN

On 13-Aug-17 19:36, Fred Jensen wrote:
Ummm ... let's be truthful here.  The B folded dipole can be found in 
radio catalogs from the 50's.  We all knew [I was a kid with a new 
license then and even I knew] that the doohicky at the center of the top 
wire was a 400 or so ohm non-inductive resistor, and half the power [3 
dB] heated it up...  

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Re: [Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread Ken G Kopp 
Skip's /K6DGW is totally correct 

73!

K0PP

On Sun, Aug 13, 2017 at 1:36 PM, Fred Jensen  wrote:

> Ummm ... let's be truthful here.  The B folded dipole can be found in
> radio catalogs from the 50's.  We all knew [I was a kid with a new license
> then and even I knew] that the doohicky at the center of the top wire was a
> 400 or so ohm non-inductive resistor, and half the power [3 dB] heated it
> up.  There was no subterfuge and B wasn't "conning" anyone, it was very
> clear in the specification sheet.  300 ohms at the feed point, hams often
> fed them with 300 ohm TV twinlead of the day to a balanced link coupled to
> the final tank circuit.  A 4:1 transformer netted 75 ohms which nicely
> matched that twinlead too.
>
> Nor did the Nat'l Guard get conned, they had a specific need for an MF/HF
> antenna that was light, easy for a couple of troops to erect, and very
> broadband ... their operating frequencies are [were] sort of day/night
> separated, rarely if ever harmonically related, and required ranges were in
> the several hundred miles or so miles.  It was a great antenna for a
> specific purpose which is why you see [or saw] them at many military
> installations, some of which were Nat'l Guard Armories.
>
> For 10 months in high school, I worked coastal marine from So California.
> Very large V-Beams on 200 ft towers with two terminating resistors at the
> ends.  Moderately broad patterns into the Pacific, very little off the
> backs [not many ships back there]. 5 KW from the TX, 2.5 KW into the
> resistors, 2.5 KW to all the ships at sea.  Great antenna for the purpose.
>
> As with all things in Engineering, antenna choice is a basket of
> trade-offs.  The Nat'l Guard rarely tries to work DX.  Broadband however
> was near the top of their list.
>
> Incidentally, the "T2FD" [TTFD] acronym arose from the "Tilted Terminated
> Folded Dipole" developed by the US Navy during WW2, designed to have one
> end hoisted on a ship's mast and the other anchored near the deck.  Lowered
> the elevation angle of the main lobe, something important to them.  Hams
> associated it with someone's call which I can't remember at this point.
>
> 73,
>
> Fred ("Skip") K6DGW
> Sparks NV USA
> Washoe County DM09dn
>
> On 8/13/2017 10:28 AM, Ken G Kopp wrote:
>
>> The antenna Jim's is referring to (below) is ... I believe ... better
>> known
>> as
>> a "T2FD".  In a case of conning the unknowing B & W ... and maybe even
>> themselves ... sold hundreds of them to the Army National Guard.  You see
>> them hanging above every armory here in MT.
>>
>>
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[Elecraft] B Folded Dipole over an Armory

2017-08-13 Thread Fred Jensen 
Ummm ... let's be truthful here.  The B folded dipole can be found in 
radio catalogs from the 50's.  We all knew [I was a kid with a new 
license then and even I knew] that the doohicky at the center of the top 
wire was a 400 or so ohm non-inductive resistor, and half the power [3 
dB] heated it up.  There was no subterfuge and B wasn't "conning" 
anyone, it was very clear in the specification sheet.  300 ohms at the 
feed point, hams often fed them with 300 ohm TV twinlead of the day to a 
balanced link coupled to the final tank circuit.  A 4:1 transformer 
netted 75 ohms which nicely matched that twinlead too.


Nor did the Nat'l Guard get conned, they had a specific need for an 
MF/HF antenna that was light, easy for a couple of troops to erect, and 
very broadband ... their operating frequencies are [were] sort of 
day/night separated, rarely if ever harmonically related, and required 
ranges were in the several hundred miles or so miles.  It was a great 
antenna for a specific purpose which is why you see [or saw] them at 
many military installations, some of which were Nat'l Guard Armories.


For 10 months in high school, I worked coastal marine from So 
California.  Very large V-Beams on 200 ft towers with two terminating 
resistors at the ends.  Moderately broad patterns into the Pacific, very 
little off the backs [not many ships back there]. 5 KW from the TX, 2.5 
KW into the resistors, 2.5 KW to all the ships at sea.  Great antenna 
for the purpose.


As with all things in Engineering, antenna choice is a basket of 
trade-offs.  The Nat'l Guard rarely tries to work DX.  Broadband however 
was near the top of their list.


Incidentally, the "T2FD" [TTFD] acronym arose from the "Tilted 
Terminated Folded Dipole" developed by the US Navy during WW2, designed 
to have one end hoisted on a ship's mast and the other anchored near the 
deck.  Lowered the elevation angle of the main lobe, something important 
to them.  Hams associated it with someone's call which I can't remember 
at this point.


73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 8/13/2017 10:28 AM, Ken G Kopp wrote:

The antenna Jim's is referring to (below) is ... I believe ... better known
as
a "T2FD".  In a case of conning the unknowing B & W ... and maybe even
themselves ... sold hundreds of them to the Army National Guard.  You see
them hanging above every armory here in MT.



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