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-   -   4NEC2? (https://www.radiobanter.com/antenna/264174-4nec2.html)

Jeff Liebermann[_2_] October 15th 18 02:20 AM

4NEC2?
 
On Sun, 14 Oct 2018 11:12:14 -0700, Jeff Liebermann
wrote:
(...)
However, if you plan to do more than that, some test equipment might
be useful.


Since you prefer a minimalist approach to test equipment, as an
alternative to your light bulb, may I suggest a return loss bridge:
https://www.google.com/search?q=return+loss+bridge&tbm=isch
Note that there are several basic designs and configurations but all
are fairly simple and easy to construct. Note that these are NOT the
same as directional couplers.

You can purchase them on eBay:
https://www.ebay.com/sch/i.html?_nkw=return+loss+bridge

There are tutorials on YouTube:
https://www.youtube.com/results?search_query=return+loss+bridge

I have three of these made by Texscan:
https://www.qsl.net/n9zia/wireless/rtrn_loss-pics.html
https://www.qsl.net/n9zia/rlb/texscan.png

and a few that I've built for microwave frequencies:
http://pe2er.nl/wifiswr/

and one for HF:
http://www.dicks-website.eu/return%20loss%20bridge_part1/part1.html
http://www.dicks-website.eu/return%20loss%20bridge_part2/part2.html
http://www.dicks-website.eu/return%20loss%20bridge_part2/part3.html
http://www.dicks-website.eu/return%20loss%20bridge_part2/part4.html
http://www.dicks-website.eu/return%20loss%20bridge_part5/part5.html

A return loss bridge is similar to a VNA except that it does not
produce numbers for the real (resistive) and imaginary (reactive)
components of the antenna impedance. It just produces the return loss
compared to a reference termination resistor, which can then be
translated into the VSWR.

To use it, you need a minimum of an RF signal generator and a
voltmeter or oscilloscope. I prefer to sweep the frequency range of
interest, so I use an RF sweep generator, and display the result on an
oscilloscope. With this arrangement, you can tune your antenna
without requiring a light bulb.


--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

brian October 15th 18 04:49 AM

4NEC2?
 
In message , Gareth's Downstairs Computer
writes
On 14/10/2018 20:30, brian wrote:
In message , Gareth's Downstairs Computer
writes
Whereas such antenna predictors seem to feature in amateur usage,
does anyone, anywhere, in the world of amateur radio have an
understanding of the underlying principles involved in
predicting the performance of antennae, or have we all,
regrettably, become indistinguishable from
consumerist CBers or beginner licensees?

4NEC2 and EZNEC are* just a fancy front and back ends for NEC2 (and
NEC4) Engines.
Program description is here :-

https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA956129.
xhtml.


Thanks for the heads up, Brian, but a quick glance suggests that some
revision might be necessary of my 3rd year uni textbook, "Fields and
Waves in Communications Electronics" by Ramo, Whinnery and Van Duzer.

ISTR it to be an excellent book explaining complicated things in words
of one syllable, but 46 years down the line, I might have a more
romantic memory of it in reality :-)



I've got mine here. We used to call it Ramo Whinnery and Bamboozle. From
the inscription in the fly leaf, it looks like I used it in 3rd year
too. Mine has one of the equations printed upside down, which threw me a
bit.

Brian



--
Brian Howie

Gareth's Downstairs Computer October 15th 18 06:00 AM

4NEC2?
 
On 14/10/2018 23:14, Ralph Mowery wrote:

I think the tests have gotten away from the technical part of ham radio
and are now geared more to the operating practices.


It is never too late to correct such an egregious mistake, for
operating as such is CB Radio whereas Amateur / Ham Radio is a
whole-life technical pursuit.


Gareth's Downstairs Computer October 15th 18 06:03 AM

4NEC2?
 
On 15/10/2018 04:49, brian wrote:
In message , Gareth's Downstairs Computer
writes
On 14/10/2018 20:30, brian wrote:
In message , Gareth's Downstairs Computer
writes
Whereas such antenna predictors seem to feature in amateur usage,
does anyone, anywhere, in the world of amateur radio have an
understanding of the underlying principles involved in
predicting the performance of antennae, or have we all,
regrettably, become indistinguishable from
consumerist CBers or beginner licensees?

*4NEC2 and EZNEC are* just a fancy front and back ends for NEC2 (and
NEC4) Engines.
*Program description is here :-

https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA956129.

xhtml.


Thanks for the heads up, Brian, but a quick glance suggests that some
revision might be necessary of my 3rd year uni textbook, "Fields and
Waves in Communications Electronics" by Ramo, Whinnery and Van Duzer.

ISTR it to be an excellent book explaining complicated things in words
of one syllable, but 46 years down the line, I might have a more
romantic memory of it in reality* :-)



I've got mine here. We used to call it Ramo Whinnery and Bamboozle. From
the inscription in the fly leaf, it looks like I used it in 3rd year
too. Mine has one of the equations printed upside down, which threw me a
bit.


Simon Ramo is an undoubted expert in that "field", but probably deals
only in that area. Much more difficult for we polymaths who must have a
working knowledge of so many more subjects, eg, the low level
programming of computers.



Jim GM4DHJ ...[_2_] October 15th 18 07:26 AM

4NEC2?
 

"Jeff" wrote in message ...

I wired up a neg ground rev counter to my pos earth 1963 mini in 1969 by
insulating the live case of the rev counter and earthing the live
terminal...worked well .....



Most of us just reversed the battery etc. and flashed the dynamo.

Jeff


I didn't ....



Jim GM4DHJ ...[_2_] October 15th 18 07:29 AM

4NEC2?
 

"Gareth's Downstairs Computer"
wrote in message
...
On 14/10/2018 23:14, Ralph Mowery wrote:

I think the tests have gotten away from the technical part of ham radio
and are now geared more to the operating practices.


It is never too late to correct such an egregious mistake, for
operating as such is CB Radio whereas Amateur / Ham Radio is a
whole-life technical pursuit.


I have been persuing an HRO500 since the 60's ..........



Bernie[_5_] October 15th 18 08:20 AM

4NEC2?
 
On Sun, 14 Oct 2018 23:55:27 -0700 (PDT)
Jeefaw K Effkay wrote:

On Sunday, October 14, 2018 at 11:01:15 PM UTC+1, Ralph Mowery wrote:
In article , lid
says...

On Sun, 14 Oct 2018 12:04:52 -0700 (PDT)
Jeefaw K Effkay wrote:

On Sunday, October 14, 2018 at 7:33:10 PM UTC+1, Jeff Liebermann
wrote:

It might help to understand why some bands use LSB while
others USB. In the early daze of sideband radio, the common
IF frequency was 9MHz. The radios had only one sideband
filter. With one filter, it was cheaper and easier to mix
and up convert in the transmitter. So, to save the cost of
adding a second filter, the bands below 9MHz were designated
as LSB and the band above 9MHz became USB. Eventually, radios
were built with two sideband filters, and this was no longer
important. As usual, the legacy technology remained in place
to haunt the survivors to this day.

I've seen this explanation before, but it doesn't make sense.

A 9MHz USB signal mixed with a 5.0 to 5.5MHz VFO will produce
mixing products in the 80m and 20m bands - but both will be
upper sideband.

When the 9 MHz is mixed with the 5 mhz the 20 meter signal is upper
sideband. The 80 meter signal is inverted and becomes the lower
sideband NOT usb.


Consider a 2 tone signal at the 9MHz USB IF, comprising 900Hz and
1300Hz tones.

The components will be 9.0009 and 9.0013

Subtract the VFO at 5.5MHz:

9.0009 - 5.5 = 3.50009
9.0013 - 5.5 = 3.50013

Nothing has been inverted. The 80m signal is still upper sideband.


GB3BERNIE

Ralph is posting from rec.radio.amateur.antenna and google groups
strips the crosspost - without a repeater, he's not going to answer you.




mm0fmf[_2_] October 15th 18 01:02 PM

4NEC2?
 
On 14/10/2018 20:59, Bernie wrote:
On Sun, 14 Oct 2018 20:25:28 +0100
Brian Howie wrote:

In message , Bernie
writes
On Sun, 14 Oct 2018 05:59:35 -0700 (PDT)
Jeefaw K Effkay wrote:

On Sunday, October 14, 2018 at 12:57:21 PM UTC+1, Geoff wrote:
On Sun, 14 Oct 2018 11:55:13 +0000
Spite sent a message from the other
side:
On 14/10/2018 11:44, Geoff wrote:
On Sun, 14 Oct 2018 11:39:58 +0000
Spite sent a message from the other
side:

On 14/10/2018 11:04, Geoff wrote:
On Sun, 14 Oct 2018 08:50:13 +0000
Spike lied:

On 14/10/2018 01:32, Jeff Liebermann wrote:

wrote:

Gareth once complained about a mobile CB set-up he
installed in a 4x4 couldn’t reach further than a
quarter mile. That’s all you need to know about
Gareth and radio.

He probably didn't need any antenna at 1/4 mile (400
meters).

snip interesting detection story

Stephen Thomas Cole, the PP, just after gaining his UK
Full licence by 'acing' all three exams, appeared on a UK
Amateur group asking which sideband he should use on 40m.
That's all you need to know about him and and his ability
with radio.

That sounds interesting - can you provide a link to that
post?

No. For some reason it's been deleted.

Then we only have your word that it ever exsisted. I choose
not to believe a word of it.

'It's been deleted' means it did exsist. You can't delete was
was never posted. You might ask yourself why it was deleted.
That's all you need to know about his ego and and his ability
with radio.




We only have your word for any of that. I choose not to believe
a word of it.

What STC actually asked was which sideband he should use for RTTY
on 40m.

Which is, of course, an interesting question as it's not something
that was covered in any exam, current or previous.

My $0.02 worth is that it doesn't matter, since an RTTY operator
will know that he needs to invert the received tones if he sees a
string of "46464646" instead of "RYRYRYRY"


Here's what was asked, and it wasn't posted no archive, or deleted,
or any of the other weak bull**** that Burt has bean spraying around:

"Was pottering at my radio last night, heard the scream of data
being sent and was triggered to revisit a long parked project;
getting going on RTTY!

Here's the hardware I'm using:

Yaesu FT757-GXii Serial/USB cable interface thing PowerMac G4 running
CocoaModem

I've got everything hooked up, have CocoaModem configured and
displaying a waterfall but when set to RTTY mode it's just decoding
gibberish...

Other than a couple of short spells at club days, this is my first
go at this and I have no idea what I'm doing... Any tips?"

https://groups.google.com/forum/#!or...-radio/MjriIIU
zuHA/_ityI76x0IMJ


Good old Burt.


For the record all the data modes including RTTY use upper sideband
all the way up from 136KHz . CW A1A is also upper sideband but there
can be advantages to be had by swapping to LSB to avoid
interference. F1A beacons seem to be a law unto themselves. You can
get quite good at reading inverted morse.

Amateur RTTY uses inverted tones and a different narrower shift
compared with commercial RTTY.

I don't know why your getting onto Steve about this as none of it is
the radio amateur courses or even online anywhere, unless some smarty
pants comes along and tells me it is. Ok it's in here for WSJT


It was Burt who was doing the 'getting onto' and when it wasn't going
well for him he introduced a new plotline about mysterious disappearing
posts and the character defects that could be at the root of the
disappearing posts.

I joined it to point out that the posts are still there and that Burt is
a liar and a ****ing idiot.




But Burt is an excellent troller.

Of course none of us would **** on Burt if he were on fire. Apart from
Dicky 'Rimjob' Brown. But that's because he's trying to hide the fact he
lied about his licence level.

Spike[_3_] October 15th 18 01:16 PM

4NEC2?
 
On 15/10/2018 01:20, Jeff Liebermann wrote:
On Sun, 14 Oct 2018 11:12:14 -0700, Jeff Liebermann
wrote:


Since you prefer a minimalist approach to test equipment, as an
alternative to your light bulb, may I suggest a return loss bridge:
https://www.google.com/search?q=return+loss+bridge&tbm=isch
Note that there are several basic designs and configurations but all
are fairly simple and easy to construct. Note that these are NOT the
same as directional couplers.


To use it, you need a minimum of an RF signal generator and a
voltmeter or oscilloscope. I prefer to sweep the frequency range of
interest, so I use an RF sweep generator, and display the result on an
oscilloscope. With this arrangement, you can tune your antenna
without requiring a light bulb.


So, let me get this right. By employing a return-loss bridge, an RF
signal generator, and either a voltmeter or an oscilloscope, you can get
results that a distant station can't distinguish from those obtained by
using a torch bulb?

Given your ability to estimate the performance of an antenna by looking
at it rather than employ modelling methods, I would have though you
would be sympathetic to the merits of the torch bulb approach.


--
Spike

"Nearly all men can stand adversity,
but if you want to test a man's character,
give him an internet group to manage"


Spike[_3_] October 15th 18 01:17 PM

4NEC2?
 
On 14/10/2018 22:01, Ralph Mowery wrote:
In article , lid says...


On Sun, 14 Oct 2018 12:04:52 -0700 (PDT)
Jeefaw K Effkay wrote:


On Sunday, October 14, 2018 at 7:33:10 PM UTC+1, Jeff Liebermann
wrote:


It might help to understand why some bands use LSB while others USB.
In the early daze of sideband radio, the common IF frequency was
9MHz. The radios had only one sideband filter. With one filter, it
was cheaper and easier to mix and up convert in the transmitter.
So, to save the cost of adding a second filter, the bands below
9MHz were designated as LSB and the band above 9MHz became USB.
Eventually, radios were built with two sideband filters, and this
was no longer important. As usual, the legacy technology remained
in place to haunt the survivors to this day.


I've seen this explanation before, but it doesn't make sense.


A 9MHz USB signal mixed with a 5.0 to 5.5MHz VFO will produce mixing
products in the 80m and 20m bands - but both will be upper sideband.



When the 9 MHz is mixed with the 5 mhz the 20 meter signal is upper
sideband. The 80 meter signal is inverted and becomes the lower
sideband NOT usb. Years ago when ssb was just starting out on the ham
bands this made 80 meters and 20 meters easy and inexpensive compaired
to other methods. So it was decided on by hams to use 40 metes and
lower frequencies as LSB and 20 meters and above as USB. Then the
government stepped in for the 5 and 10 MHz bands and dictated what to
use.


For other reasons most digital is in the USB mode for all bands except
for RTTY. RTTY is usually used in the LSB mode for all ham bands, but
can be used in the USB mode if the tones are inverted. The commercial
RTTY was usually inverted from the normal ham RTTY.


"Geoff" has long had a 'difficult' relationship with HF.

--
Spike

"Nearly all men can stand adversity,
but if you want to test a man's character,
give him an internet group to manage"



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