"Dave Shrader" wrote -
Seriously, I wonder if any readers recall the details of measuring and
plotting based on the GR Slotted Line?

-------------------------------------------------------

What's 'GR' ? Never heard of it.

Never-to-be-forgotten, I first measured SWR on a laboratory bench slotted
line in the town of Stockport near Manchester around February 1944. V1's and
V2's, Hitler's secret weapons, were falling on London and S.E. England. The
1000-bomber raids by the RAF on German towns and cities, the fire storms
directed by Air Marshal Bomber Harris, were building up with an ever
increasing ferocious intensity. One night 110 heavy bombers failed to return
to base. The death toll in Europe and Russia had already passed the 15
million mark.

I remember it was raining at the time. It always rains in Manchester.

There were two simple relative voltage measurements spaced 1/4-wavelengths
apart. Values of Zo, Zg, Zt and Gamma were quite irrelevant. The only
mathematical equation was SWR = V1/V2. And that's all there was to it!

So began my radio education.
----
Reg, G4FGQ

Reg

Did General radio ever make a slotted line?



"Reg Edwards" wrote in message
...

"Dave Shrader" wrote -
Seriously, I wonder if any readers recall the details of measuring and
plotting based on the GR Slotted Line?

-------------------------------------------------------

What's 'GR' ? Never heard of it.

Never-to-be-forgotten, I first measured SWR on a laboratory bench slotted
line in the town of Stockport near Manchester around February 1944. V1's
and
V2's, Hitler's secret weapons, were falling on London and S.E. England.
The
1000-bomber raids by the RAF on German towns and cities, the fire storms
directed by Air Marshal Bomber Harris, were building up with an ever
increasing ferocious intensity. One night 110 heavy bombers failed to
return
to base. The death toll in Europe and Russia had already passed the 15
million mark.

I remember it was raining at the time. It always rains in Manchester.

There were two simple relative voltage measurements spaced 1/4-wavelengths
apart. Values of Zo, Zg, Zt and Gamma were quite irrelevant. The only
mathematical equation was SWR = V1/V2. And that's all there was to it!

So began my radio education.
----
Reg, G4FGQ

Reg Edwards wrote:
"Dave Shrader" wrote -

Seriously, I wonder if any readers recall the details of measuring and
plotting based on the GR Slotted Line?


-------------------------------------------------------

What's 'GR' ? Never heard of it.

I mentioned General Radio earlier in the post. General Radio AKA GR.

Sorry for the confusion.

Dave

You made a comment about the details of calculating load impedance using a
slotted line. I'm curious to know if anyone has built a slotted line at
home. It would be interesting to me to have a slotted line for about
125MHz.

It seems that if you could measure the voltage mins along a line
terminated by the load to be evaluated and the location of the min with a
short ckt to replace that load. That reading, together with the Vmax/Vmin
could get you close to the load impedance with a Smith Chart (I think)

Jerry




"Dave Shrader" wrote in message
news:fxzdc.143$cD2.12959@attbi_s51...
Reg Edwards wrote:

Richard Clark,

I fully support your "All antennas have zero gain" campaign.

IMO applying the word 'Gain' to an antenna is misuse of the word 'gain'.

Beam forming antennas do concentrate the RF energy into an angle less
than 2*Pi steradians [Hemisphere] but the total energy concentrated is
still the power applied to the antenna minus losses. The far field from
a beam forming antenna is more intense than from an isotropic antenna.

Maybe the better term is to quote the solid angle at the 1/2 power
points in the E and H plane as a figure of merit. Example: antenna A has
a 1/2 power beam width of 2500 square degrees while antenna B has a 1/2
power beam width of 1800 square degrees.


Why not join the "There's no such thing as an SWR meter" campaign?
----
Reg, G4FGQ



Ah! But there are techniques for measuring TRUE VSWR!! [Not my little
Daiwa 101C or even the trusty Bird.]

Nope, I used to measure TRUE VSWR [in 1958] using a General Radio
Slotted Line with moveable probe!! I've forgotten the plotting details
but the answer came from plotting the response over 1/4 wavelength on a
SMITH Chart. Ain't cheap but it was accurate.

Seriously, I wonder if any readers recall the details of measuring and
plotting based on the GR Slotted Line?

Next question: where do I get a 160 meter 1/2 wavelength 50 ohm slotted
line?

Jerry Martes wrote:
I'm curious to know if anyone has built a slotted line at home.

Jerry, if you use balanced feedline, you don't need a slotted
line. You can just use an inductive pickup loop with a 1N34A
diode rectifier circuit. Whatever you read on your DC voltmeter
as maximum and minimum values will yield the SWR. That's another
advantage of ladder-line.
--
73, Cecil, W5DXP



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Bill

How does a person measure the gain of an antenna?

Jerry


"Bill Turner" wrote in message
...
On Fri, 09 Apr 2004 19:15:05 GMT, Dave Shrader
wrote:


So, the correct gain terminology must speak in terms of resulting
PATTERN not the antenna.

Ok, but the pattern is created by the antenna. If the pattern has gain,
most of us would think of the antenna having gain.


'Antenna gain' is both loose and incorrect language notwithstanding
advertising and marketing claims.

If enough people use a term incorrectly, it becomes correct, like it or
not. The word "lite" as in "lite beer" did not exist a couple of
decades ago. Some advertiser decided to use it in place of "light" and
despite opposition from linguistic purists, it is now correct. "Antenna
gain" may not be correct in the eyes of a purist, but if the masses use
it and know what it means...

--
Bill, W6WRT
QSLs via LoTW

"Bill Turner" wrote in message
...
On Sat, 10 Apr 2004 13:40:51 GMT, "Jerry Martes"
wrote:

Bill

How does a person measure the gain of an antenna?

Jerry

__________________________________________________ _______

Carefully, I would hope.

--
Bill, W6WRT
QSLs via LoTW

I'll be carefull if you'll tell me how to do it.

Jerry

On Sat, 10 Apr 2004 08:37:09 -0700, Bill Turner
wrote:
Bill

How does a person measure the gain of an antenna?

Jerry

Carefully, I would hope.

Hi Bill,

Your response hardly carries the water for an argument supporting gain
being commonly distinct from directivity.

To answer Jerry's question (he probably already knows how) requires
the total integration of all power emitted by the radiator - not an
easy task (as would confirm Bill's sparse reply) and then measuring
power emitted within small volumes (solid angles of sub-radian
dimension) to compare against the whole.

The most distinctive point to observe about this "gain" is that almost
all the power radiated is lost - "almost" being a patronizing term. A
simple thought problem will reveal this sad fate.

Let us presume you are transmitting 100W with 100% efficiency. Now,
lets further presume that the entire population of the planet is
monitoring you with S-9 readability. That is (let's be generous), 10
Billion receivers. What is the net result of this massive
communication in system efficiency?
0.5%

The antenna in the most perfect of circumstances exhibits an absolute
loss of 99.5W and I could easily bet no one here even pretends to
approach 0.000001% of this.

Now, tell me about GAIN. :-)

73's
Richard Clark, KB7QHC

Jerry Martes wrote:
How does a person measure the gain of an antenna?

For 75m mobile antenna shootouts, we have measured the field
strength of the ground wave in the far field compared to
a reference antenna.
--
73, Cecil, W5DXP



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Jerry Martes wrote:

Bill

How does a person measure the gain of an antenna?

Jerry


In the olden days, 1985, on an outdoor range, we would calculate the
gain from measuring the 1/2 power points on an antenna range at 1000
wavelengths minimum between antennas and find the 1/2 power [-3 dB]
angles in the horizontal and vertical planes. [Note C-Band and S-Band]

Knowing the angles the 'Gain' is calculated by dividing 41259 by the
product of the horizontal and vertical angles corresponding to the 1/2
power point. [Note: 41259 is the surface of the sphere measured in
square steradians.]

On the indoor anechoic chamber we measured the input power at the feed
point through a -10 dB splitter and the radiated power density at a
target point in the far wall. Then ran the basic calculation.
[Classified Military Program]

Aligning those 12 foot diameter dishes inside the anechoic chamber was
'fun'.

Even after managing two antenna ranges and being party to 'antenna gain'
measurements for more than 10 years of my professional life, I still
have fun touting that antennas have 'No Gain'.