Magnetic Longwire Balun: weird resistance. What is normal?
spamhog
I am rebuilding my 15+ yr old longwire+MLB antenna due to broken coax
etc etc.
I checked the DC resistance between the 3 terminals of the MLB:
IN - high impedance longwire tiepost
OUT - low impedance coax center conductor
SHIELD - coax shield.
Weird results:
IN-OUT = < 2 ohm
IN-SHEILD = OUT-SHIELD = ~50 ohm (can't really notice a difference)
Inverting + and - does not change result, hence not an obvious
semiconducting corrosion cell.
AFAIK
- the circuit is just a very broadband impedance transformer
- there should be no resistor
...however I don't remember what the normal resistance might have
been.
QUESTIONS
1- what would be normal resistance values?
would near zero be reasonable?
2- guesses on what might have happened?
is 50 ohm compatible with a poor contact
3- did anybody crack it open?
suggestions for repair?
Thanks for any wisdom on this matter!
N1JPR
Wimpie
Hello,
It sounds like there is a 50 Ohms resistor between the shield
connection and the common of the autotransformer The MLB I made
myself has no resistors inside. If there was resistance, I would
expect it between the transformer and the "out" terminal, not
inbetween the transformer and ground terminal.
Did you add some small mechanical impulse to the MLB and/or shield
connection. If there is contact resistance problem, it mostly changes
after mechanical shocks. Does it mention a brand or type number?
Does it function? You can check this by putting a short piece of wire
to the 50 Ohms coaxial cable that goes to your receiver. Tune to a
station where you still can observe increase or decrease of signal
strength. Now connect the MLB to the cable and connect the piece of
wire to the input of the MLB. This should result in more signal
power.
That short piece of wire has very high impedance at HF so adding the
MLB will reduce the mismatch, hence increases output signal.
Best regards,
Wim
PA3DJS
www.tetech.nl
when using PM, remove abc first.
RHF
N1JPR - OK - What Brand ? Model ? of MLB ?
=WRT= Shortwave Radio Listener {Receive Only}
-so-called- Magnetic Longwire Baluns [MLBs]
Let's say you have a 'classic' 10-Turn Secondary
Winding Coax-Shield-to-Radio-Input that is couple
with a 30-Turn Primary Coax-Shield-to-Antenna.
* Using a Common Coax Shield Ground Point
for both Windings.
Using #24 AWG Solid Copper Wire
-note- Wire Gauge Resistance per foot #24 = 0.03 Ohms/Ft
* #14 = 0.003 Ohms/Ft
* #20 = 0.012 Ohms/Ft
* #36 = 0.4 Ohms/Ft
* #40 = 1.0 Ohm/Ft
Using a Small 1-Inch OD Ferrite Toroid "Donut" Core
with 1/2" ID and 1/2" Thick/Wide.
http://www.goldmine-elec-products.com/prodinfo.asp?number=G6683&variation=
Each Turn is about 2.4 Inches of #24 Copper Wire
* 10 Turns ~ 24 Inches ~ 2 Feet = 0.06 [~1/10th] Ohm
* 30 Turns ~ 72 Inches ~ 6 Feet = 0.18 [~1/5th] Ohm
Wire Gauge Resistance per foot #24 = 0.03 Ohms
http://www.epanorama.net/documents/wiring/wire_resistance.html
With Common Ground Un-Uns -aka- Magnetic
Longwire Baluns [MLBs] that are 'suspect'
* Simply Replace with a New MLB
* Build a New MLB from scratch
* Tear-down and re-build the old MLB into a
New MLB using the same Core -if- not damaged
{cracked or discolored}. Use New Wire and if
needed New Hardware too.
However before you suspect and replace the MLB :
1 - Check-out your Connections at the MLB
2 - Check-out your Coax Cable
3 - Checkout your Antenna Wire
4 - Checkout your Ground Wire and Ground Rod
More often then not it is the 'Connections' and a
Damaged/Broken Coax Cable where the problem
is and nothing internal to the MLB.
hope this helps - iane ~ RHF
.
.
RHF
>
> Each Turn is about 2.4 Inches of #24 Copper Wire
> * 10 Turns ~ 24 Inches ~ 2 Feet = 0.06 [~1/10th] Ohm
> * 30 Turns ~ 72 Inches ~ 6 Feet = 0.18 [~1/5th] Ohm
>
>
> With Common Ground Un-Uns -aka- Magnetic
> Longwire Baluns [MLBs] that are 'suspect'
> * Simply Replace with a New MLB
> * Build a New MLB from scratch
> * Tear-down and re-build the old MLB into a
> New MLB using the same Core -if- not damaged
> {cracked or discolored}. Use New Wire and if
> needed New Hardware too.
>
> However before you suspect and replace the MLB :
> 1 - Check-out your Connections at the MLB
> 2 - Check-out your Coax Cable
> 3 - Checkout your Antenna Wire
> 4 - Checkout your Ground Wire and Ground Rod
> More often then not it is the 'Connections' and a
> Damaged/Broken Coax Cable where the problem
> is and nothing internal to the MLB.
>
> hope this helps - iane ~ RHF
> .
> .
Follow-up . . .
Magnetic Longwire Balun : a Con or Not ?
http://www.hard-core-dx.com/nordicdx/antenna/feed/magbal1.html
.
Magnetic Longwire Balun : Not Really a Balun
http://www.hard-core-dx.com/nordicdx/antenna/feed/magbal2.html
.
Two Shortwave Listener (SWL) 10:1 Baluns
for Random Wire Antennas -by- RHF
http://www.radiobanter.com/showthread.php?t=60185
.
SWL Newbies : The Verdict - Magnetic Longwire Balun
Is Too Expensive -by- Alan Johnson
http://groups.google.com/group/rec.radio.shortwave/msg/ac6e768de54f9404
.
Here are some good LMBs :
* WinRadio LWA-0130 Long Wire Antenna Adapter
http://www.grove-ent.com/WR0130.html
* RF Systems Magnetic Longwire Balun (MLB)
http://www.universal-radio.com/catalog/sw_ant/1484.html
* Palomar MLB-1 Magnetic Longwire Balun
http://www.palomar-engineers.com/MLB-1/mlb-1.html
* Longwire Impedance Matcher [LIM]
http://www.shortwavestore.com/lim-longwire-impedance-matcher.html
* Shortwave Antenna Matching Balun
http://cgi.ebay.com.sg/Shortwave-antenna-matching-balun-/220433803177
* * 9:1 Wideband RF Transformer "Kit" for SWL Receiving
http://www.bobsamerica.com/balun.html
~ RHF
.
John Smith
What many call a balun is not, it is an RF auto-transformer; The common
schematic on the net uses a 10 turn primary with a 29-30 turn secondary;
This is an auto-transformer, but it works fine in matching an an
antenna in place of a 9:1 balun, for general SWL.
A 9:1 auto-transformer:
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=12673
A true 9:1 balun (schematic down on the page):
http://users.belgacom.net/hamradio/schemas/Magnetic%20Longwire%20Balun_MLB.htm
One importance difference you will notice, the auto-transformer has two
windings, the cold ends of the two windings running to gnd/coax-braid.
The balun has three windings, or a trifilar winding, these 3 windings
are connected in series with the 50 ohm connection across one winding,
the high impedance connection is made across all 3 windings.
Transmission Line Transformer is also used to describe some types of
baluns. Baluns are frequently wound using coax for the windings ... etc.
In the above, I have made no difference between balun and unun, there is
a difference, and most often you find ununs employed in SWL, with
monopoles--unbalanced antennas. Baluns are utilized with
dipoles--balanced antennas.
Regards,
JS
John Smith
> ...
> Thanks for any wisdom on this matter!
>
> N1JPR
I forgot to mention, the 50 ohms sounds more than "just a coincidence"
to me. I am willing to bet they worked a 50 ohm resistance in there
somewhere ... it would be very interesting to see a schematic of that
and see how they did it, and for what purpose.
It is possible, unless you can see ferrite material, toroid or bar, that
your "balun" is ripoff!
Regards,
JS
RHF
>
> One importance difference you will notice, the auto-transformer has two
> windings, the cold ends of the two windings running to gnd/coax-braid.
> The balun has three windings, or a trifilar winding, these 3 windings
> are connected in series with the 50 ohm connection across one winding,
> the high impedance connection is made across all 3 windings.
> Transmission Line Transformer is also used to describe some types of
> baluns. Baluns are frequently wound using coax for the windings ... etc.
>
> In the above, I have made no difference between balun and unun, there is
> a difference, and most often you find ununs employed in SWL, with
> monopoles--unbalanced antennas. Baluns are utilized with
> dipoles--balanced antennas.
>
> Regards,
> JS
"JS",
Shortwave Radio Listener (SWL) Antenna Baluns [UnUns]
-so-called- Magnetic Longwire Baluns [MLBs]
IIRC - Isn't the Balun [UnUn] only an Auto-Transformer
-if- The Two Windings share a Common Point ?
-or- One 'Tapped' Winding
Auto-Transformer with 'x' Common Ground Point
Ant-mmmmmmmm-x-mmm-Rx
======================= Ferrite
http://web.mclink.it/MC4868/balun/mlb.jpg
-versus-
RF Matching Transformer
Ant-mmmmmmmm-Grd
================= Ferrite
. . . Rx-mmm-Mains . . .
http://web.mclink.it/MC4868/balun/balun.jpg
Many/Most SWL Antenna Baluns [UnUns] use Two
separate Windings with a Common Ground-Point
http://www.bobsamerica.com/sitebuilder/images/balun-inst-sheet-410x570.jpg
-and- a few use Two non-connected Windings.
http://3.bp.blogspot.com/_RBvJRry5YbE/SxMCCZRQ5zI/AAAAAAAAAIM/3GMK28Sq0po/s1600/The+EWE+Antenne+Balun.png
i want to know - iane ~ RHF
.
.
Ian Jackson
<assembl...@gmail.com> writes
or a balun, the obvious way of winding it is to wind it trifilar by
filling the ring with N turns, then interwinding with a further N turns
(so the wires never cross), then finally interwinding a further N turns.
That isn't made clear in the DXzone article.
The ON6MU balun seems to be wound with purpose made trifilar wire,
rather than ordinary off-the-shelf single wire, interwound. [Or maybe
it's just wound very, very carefully!] Some Cable TV equipment used to
use ready-made wire (both bifilar and trifilar) for the windings of
their miniature wideband torroidal 'transmission line' RF transformers.
There were typically 5 turns around the ring, and they were normally
connected as 2:1 turns ratio (4:1 impedance) or 3:2 turns ratio (2.25
impedance).
Whether the transformer ends up as a balun or an unun simply depends on
how you connect the windings, and where you make the external
connections.
--
Ian
John Smith
>> ...
> Regardless of whether you use the 9:1 impedance transformer as a, 'unun'
> or a balun, the obvious way of winding it is to wind it trifilar by
> filling the ring with N turns, then interwinding with a further N turns
> (so the wires never cross), then finally interwinding a further N turns.
> That isn't made clear in the DXzone article.
>
I think the author was attempting to end up with a transmission line on
the balun with a specific characteristic impedance in mind ... I am
taking it for granted he measured the impedance of the transmission line
of twisted conductors and it benefited the frequency bandwidth of the
balun, or other characteristics, in a way which he found desirable, in
such applications the spiral turns of the conductors are usually
stipulated in "turns per inch" (TPI) ... however, he could have just
done it "because it looked kewl." lol
> The ON6MU balun seems to be wound with purpose made trifilar wire,
> rather than ordinary off-the-shelf single wire, interwound. [Or maybe
> it's just wound very, very carefully!] Some Cable TV equipment used to
> use ready-made wire (both bifilar and trifilar) for the windings of
> their miniature wideband torroidal 'transmission line' RF transformers.
> There were typically 5 turns around the ring, and they were normally
> connected as 2:1 turns ratio (4:1 impedance) or 3:2 turns ratio (2.25
> impedance).
The permeability of the ferrite/iron material of the balun will dictate
the number of turns to function correctly, mostly. If someone is
unfamiliar with how to compute this, I would suggest they follow a given
design, of course. To effectively choke off the rf flowing on the
outside of the coax, common mode, the balun must present sufficient
impedance to the flow of current, at the frequency(s) in question, of
course ... and of course, balun size/mass is determined by power
requirements (transmitting applications)--generally not even of concern
in receiving applications, and balun size ends up being dictated by
necessary turns/core-permeability.
>
> Whether the transformer ends up as a balun or an unun simply depends on
> how you connect the windings, and where you make the external connections.
Of course, you "have" to know if you want to match a balanced ant or an
unbalanced one ... baluns are both very simple and a "rabbit hole", like
everything else, it depends on how deep you want to go ...
Regards,
JS
RHF
<ianREMOVETHISjack...@g3ohx.demon.co.uk> wrote:
> In message <i61cun$aj...@news.eternal-september.org>, John Smith
> <assemblywiz...@gmail.com> writes
"IJ",
Many/most SWLers are simple DIYers
and not Ham-Techies : "KISAP"
A plain Ferrite Core "Donut" with
http://www.goldmine-elec-products.com/images/G6683B.jpg
One 30 Turn Winding on One-Side and a
Second 10 Turn Winding on the Other-Side
is Good Enough to work and simple to do.
http://www.qrp.pops.net/images/before%202008/UNUN-1.JPG
SWL Home Builder making a 9:1 UnUn
http://www.qrp.pops.net/swl-ant.asp
A more involved write-up on making your own
Impedance Matching Transformers for Receiving
Antennas at Medium and Lower Shortwave
Frequencies -circa- June /July 2003
-by- Bill Bowers, John Bryant, Nick Hall-Patch, VE7DXR
http://www.dxing.info/equipment/impedance_matching_bryant.pdf
Just "KISAP" = Keep It Simple And Practical - iane ~ RHF
.
.
John Smith
> ...
> "IJ",
>
> Many/most SWLers are simple DIYers
> and not Ham-Techies : "KISAP"
> ...
> Just "KISAP" = Keep It Simple And Practical - iane ~ RHF
> .
> .
Yes, well, "ignorance is bliss" (related to KISS), as a motto, is a
usable tool, I suppose ...
However, Ians' pointing out of some of the more "esoteric"
properties/potentials of "simple impedance matching" tools will not be
wasted on those with deeper interests, I am sure. For others,
purchasing one, off the shelf, and ready-made, would free one of having
to know how to construct one which is capable of excellent performance.
And, a simple but immediate benefit of baluns vs. transformers is quite
obvious, they are more broad-banded ... I would think the importance of
that would not be wasted, on most ...
Regards,
JS
RHF
> On 9/6/2010 5:18 AM, RHF wrote:
>
> > ...
> > "IJ",
>
> > Many/most SWLers are simple DIYers
> > and not Ham-Techies : "KISAP"
> > ...
> > Just "KISAP" = Keep It Simple And Practical - iane ~ RHF
> > .
> > .
- Yes, well, "ignorance is bliss"
- (related to KISS), as a motto,
- is a usable tool, I suppose ...
JS - Don;t like "KISS" -cause-
'Keep It Simple Stupid'
has you calling someone 'Stupid'.
That's Why the "KISAP" is better
'Keep It Simple And Practical'
has you Being Helpful by :
1 - Making It Easy to Understand
2 - Providing a Useful Way of Doing Something
JS - 'kisap' goes to motive and motivation ~ RHF
John Smith
> ...
> JS - Don;t like "KISS" -cause-
> 'Keep It Simple Stupid'
> has you calling someone 'Stupid'.
>
> That's Why the "KISAP" is better
> 'Keep It Simple And Practical'
> has you Being Helpful by :
> 1 - Making It Easy to Understand
> 2 - Providing a Useful Way of Doing Something
>
> JS - 'kisap' goes to motive and motivation ~ RHF
> .
>> ...
You must be a child ...
I come from a time when you call something what it is. We don't rename
homosexual to gay, etc. If someone is stupid, I am damn well ready to
step up and call them stupid ... call a rose by any other name, it is
still a rose ... call a turd ... well, you get it.
Regards,
JS
RHF
> On 9/6/2010 3:56 PM, RHF wrote:
>
> > ...
> > JS - Don;t like "KISS" -cause-
> > 'Keep It Simple Stupid'
> > has you calling someone 'Stupid'.
>
> > That's Why the "KISAP" is better
> > 'Keep It Simple And Practical'
> > has you Being Helpful by :
> > 1 - Making It Easy to Understand
> > 2 - Providing a Useful Way of Doing Something
>
> > JS - 'kisap' goes to motive and motivation ~ RHF
> > .
>
> >> ...
>
JS - "i" must be a 'child'
Read This Again :
JS - 'kisap' goes to motive and motivation ~ RHF
Trying To Be Helpful & Helping Others
Helping Others To Learn To Help Themselves
{Working With People To Accomplish Their Goals}
- I come from a time when you call something what it is. We don't
rename
- homosexual to gay, etc. If someone is stupid, I am damn well ready
to
- step up and call them stupid ... call a rose by any other name, it
is
- still a rose ... call a turd ... well, you get it.
-
- Regards,
- JS
JS - it sounds like you are . . .
still stuck on "17" - pal ~ RHF
.
John Smith
> ...
> JS - it sounds like you are . . .
> still stuck on "17" - pal ~ RHF
> .
I can't believe they can take my tax dollars, good money, and have the
school system turn out witless idiots ...
Regards,
JS
RHF
Magnetic Longwire SWL Antenna {Balun}
9:1 Matching Transformer "KISAP"
http://groups.google.com/group/rec.radio.shortwave/msg/900018d6b7524b37
.
and the Original Post . . .
Magnetic Longwire Balun: weird resistance. What is normal?
http://groups.google.com/group/rec.radio.shortwave/msg/e9e5c03682ab2d64
-thread-
http://groups.google.com/group/rec.radio.shortwave/browse_frm/thread/0aff4ce2a4b7b99e/e9e5c03682ab2d64?#e9e5c03682ab2d64
.
On Sep 6, 5:51 pm, John Smith <assemblywiz...@gmail.com> wrote:
> On 9/6/2010 4:58 PM, RHF wrote:
>
> > ...
- - JS - it sounds like you are . . .
- - still stuck on "17" - pal ~ RHF
- I can't believe they can take my tax dollars,
- good money, and have the school system
- turn out witless idiots ...
-
- Regards,
- JS
JS - So sorry to hear, that you 'feel'
so bad about yourself - pal ~ RHF
.
-ps- JS - Nice Personal "Ping-Pong" Game ;;-}}
-so- JS please put a 'PING' -or- a 'PONG' at the
start of the Subject Line if you want to continue.
.
.
-however- The Topic was and still is :
Magnetic Longwire SWL Antenna {Balun}
9:1 Matching Transformer "KISAP"
http://groups.google.com/group/rec.radio.shortwave/msg/900018d6b7524b37
.
and the Original Post . . .
Magnetic Longwire Balun: weird resistance. What is normal?
http://groups.google.com/group/rec.radio.shortwave/msg/e9e5c03682ab2d64
-thread-
http://groups.google.com/group/rec.radio.shortwave/browse_frm/thread/0aff4ce2a4b7b99e/e9e5c03682ab2d64?#e9e5c03682ab2d64
.
.
arthr...@webtv.net
Unfortunately- more often than we hope our hard earned (read blood)
money collected by the taxman goes to waste. From what I see the
entire educational system has become a complete farcicle. How about
sending men to Mars? That can be much more beneficial- at least it
might revive NASA and create some jobs. May be...
RHF
> On Sep 6, 8:51 pm, John Smith <assemblywiz...@gmail.com> wrote:
>
> > On 9/6/2010 4:58 PM, RHF wrote:
>
> > > ...
> > > JS - it sounds like you are . . .
> > > still stuck on "17" - pal ~ RHF
> > > .
>
> > I can't believe they can take my tax dollars, good money, and have the
> > school system turn out witless idiots ...
>
> > Regards,
> > JS
>
> Unfortunately- more often than we hope our hard earned (read blood)
> money collected by the taxman goes to waste. From what I see the
> entire educational system has become a complete farcicle.
- That can be much more beneficial- at least it
- might revive NASA and create some jobs.
- May be...
-wrt- NASA Sending Men to Mars :
How about we spend all that time and money
on 'fixing' our Education System first.
What good is it to send Men to Mars . . .
-if- The People back on Earth can't spell M-a-r-s
-and- Don't know that Mars exists or anything
about it . . .
Before We Go To 'Outer' Space : Let Us First
Fill The "Inner Space" of Our Children's Minds.
America - Teach Your Children Well
http://www.youtube.com/watch?v=az9Az6S1nus
Bless Every American Child With A Good Education
Healthy Minds & Healthy Bodies & Healthy Spirits
http://www.youtube.com/watch?v=AhR36gV6vW4
amen, Amen. and AMEN ! -efpal-
the wisdom of the ages - comes with age . . .
-alas- i am still young at heart ~ RHF©
John Smith
> .
> .
> -however- The Topic was and still is :
>
> Magnetic Longwire SWL Antenna {Balun}
> 9:1 Matching Transformer "KISAP"
> http://groups.google.com/group/rec.radio.shortwave/msg/900018d6b7524b37
> .
> and the Original Post . . .
> Magnetic Longwire Balun: weird resistance. What is normal?
> http://groups.google.com/group/rec.radio.shortwave/msg/e9e5c03682ab2d64
> -thread-
> http://groups.google.com/group/rec.radio.shortwave/browse_frm/thread/0aff4ce2a4b7b99e/e9e5c03682ab2d64?#e9e5c03682ab2d64
> .
> .
Yeah, I already dealt with that in a nice way. The original poster has
a 50 ohm resistor in a box. It happens ... if he winds one himself,
picking a good design, he will know what he has.
Regards,
JS
dave
How about a Manhattan Project for clean renewable energy? NASA benefits
the same creeps as perpetual war.
dave
cost-effective? That makes no business sense.
"You want fries with that?"
RHF
> RHF wrote:
> > On Sep 6, 8:27 pm, arthrny...@webtv.net wrote:
> >> On Sep 6, 8:51 pm, John Smith<assemblywiz...@gmail.com> wrote:
>
> >>> On 9/6/2010 4:58 PM, RHF wrote:
>
> >>>> ...
> >>>> JS - it sounds like you are . . .
> >>>> still stuck on "17" - pal ~ RHF
> >>>> .
>
> >>> I can't believe they can take my tax dollars, good money, and have the
> >>> school system turn out witless idiots ...
>
> >>> Regards,
> >>> JS
>
> >> Unfortunately- more often than we hope our hard earned (read blood)
> >> money collected by the taxman goes to waste. From what I see the
> >> entire educational system has become a complete farcicle.
> > - How about sending men to Mars?
> > - That can be much more beneficial- at least it
> > - might revive NASA and create some jobs.
> > - May be...
>
- -
- - How about we spend all that time and money
- - on 'fixing' our Education System first.
- -
- - What good is it to send Men to Mars . . .
- - -if- The People back on Earth can't spell M-a-r-s
- - -and- Don't know that Mars exists or anything
- - about it . . .
- Why train American engineers when S. Asian
- engineers are more cost-effective?
- That makes no business sense.
-
- "You want fries with that?"
Ah Dave you come from Planet Jack-in-the-Box
in the Solar System of Walmart. - wass ~ RHF
.
.
RHF
> arthrny...@webtv.net wrote:
> > On Sep 6, 8:51 pm, John Smith<assemblywiz...@gmail.com> wrote:
> > Unfortunately- more often than we hope our hard earned (read blood)
> > money collected by the taxman goes to waste. From what I see the
> > entire educational system has become a complete farcicle. How about
> > sending men to Mars? That can be much more beneficial- at least it
> > might revive NASA and create some jobs. May be...
- How about a Manhattan Project
- for clean renewable energy?
Dave - Now that is something I can get behind
and would support Raising Your Taxes for . . .
The US Department of Energy and the US EPA
should both be jointly working on a Multi-Decade
National Clean Renewable Energy Projects
http://en.wikipedia.org/wiki/EPA
http://en.wikipedia.org/wiki/United_States_Department_of_Energy
- NASA benefits the same creeps as perpetual war.
Nah - Let NASA continue to do it 'Space' Thing.
The Greats Victory in the War Against the Islam-O-Fascist
that the USA could have is American Energy Independence
from Arab Oil and Muslim Controlled Petro-Fuels.
support american energy Independence ~ RHF
.
.
m II
> The Greats Victory in the War Against the Islam-O-Fascist
> that the USA could have is American Energy Independence
> from Arab Oil and Muslim Controlled Petro-Fuels.
Kill everyone over there and *then* the oil is free for the taking,
right? How Cheney of you.
mike
dave
>
> - NASA benefits the same creeps as perpetual war.
>
> Nah - Let NASA continue to do it 'Space' Thing.
>
Can't afford people in space. Robots maybe.
John Smith
>> ...
> Kill everyone over there and *then* the oil is free for the taking,
> right? How Cheney of you.
> mike
Don't know about all that but, the only good radical mooselum is a dead
radical mooselum. My motto is, "Let them die with sharia law stuck up
their butts!" ROFLOL
Regards,
JS
RHF
- - RHF wrote:
- - The Greatest Victory in the War Against the Islam-O-Fascist
- - that the USA could have is American Energy Independence
- - from Arab Oil and Muslim Controlled Petro-Fuels.
Dang Mike [M II] ::: I {RHF} wrote :
The Greatest Victory in the War Against the Islam-O-Fascist
that the USA could have is American Energy Independence
from Arab Oil and Muslim Controlled Petro-Fuels.
The Answer My Friend Is . . .
http://www.youtube.com/watch?v=LIFxbOZezhE
Let The Sun Shine In . . .
http://www.youtube.com/watch?v=LANwIgpha7k
Let the Rain {Water} Wash Your Spirit
and Clean Your Mind . . .
http://www.youtube.com/watch?v=xwQEen51sFM
Which is All Peaceful Means* and NO War [.]
* Ecological and Sustainable Energy for the USA
from our own internal Natural Resources.
Then 'you' M II wrote :
- Kill everyone over there and *then*
- the oil is free for the taking, right?
NO M II 'you' as a Canadian may want to kill, Kill. KILL !
All the Arabs and All the Muslims in the World for what . . .
Creep 'Free' Oil : "You" are a Kill-A-Holic M II !
- How Cheney of you.
- mike
Oh M II - How Very Absurdly Canadian "You" Are !
mike - heal thyself of killing and warmongering
in the quest for oil and profit - eafpal ~ RHF
.
'eafpal' = "Eternal and Fraternal Peace and Love"
.
.
RHF
> RHF wrote:
>
- - Nah - Let NASA continue to do it 'Space' Thing.
- Can't afford people in space. Robots maybe.
Dave,
Since Apollo 17 back in 1972 all NASA has done
beyond Earth Orbit is Un-Maned 'Robotic' Space
Craft; and most agree it is 1/5th to 1/10th the Cost
and provides an equal amount of Scientific Information
Gathering and Data Collection.
Dave - Why change almost 40 years of doing it right ?
space exploration - kisap ~ RHF
.
.
m II
How long have you had this comprehension problem? Nothing you have
said has ANY bearing on what I wrote.
mike
John Smith
> ...
> NO M II 'you' as a Canadian may want to kill, Kill. KILL !
> All the Arabs and All the Muslims in the World for what . . .
> Creep 'Free' Oil : "You" are a Kill-A-Holic M II !
> ...
And, I don't know about all that ... but, I want those who are loping
thieves hands off, publicly flogging single people for having sex with
the opposite gender, stoning adulterers to death, hanging homosexuals,
etc. killed! Just consider it a coincidence that these idiots are
mooselum. I also would like those who would steal their oil locked up
in prisons and made to give it back (or the money), also ...
Regards,
JS
D. Peter Maus
You sound surprised.
>
m II
> You sound surprised.
I must have a very, very short AND faulty memory. It's not like I
didn't know any better.
It shouldn't be too difficult to refrain from engaging him as often as
I do. Contemplating Cuhulin's boobs may well be a more appropriate
pastime.
It would certainly be more intellectually rewarding.
mike
John Smith
Kewl dude ... personal problems usually are not discussed here though ...
Regards,
JS
D. Peter Maus
It's USENet. Everyone has their own style. Roy's is a bit unique.
But he's no less goofy than about half the sockpuppets and ringers
that invade the group when political opportunities are high.
Be amused. Otherwise it will drive you over the edge.
Cuhulin's boobs notwithstanding.
RHF
- Nothing you have said has ANY bearing on what I wrote.
-
- mike
M II -wrote-
"Kill everyone over there and *then* the oil is free
for the taking,right? How Cheney of you. - mike"
Killing Them Ain't The Answer [.]
-and- Cheney Ain't The Answer Either.
-also- Free Oil Ain't The Answer.
Again and Again Mike [M II] :
The Greatest Victory in the War Against the Islam-O-Fascist
that the USA could have is . . . ? ? ?
-answer- American Energy Independence from Arab Oil
and Muslim Controlled Petro-Fuels.
* don't do business with them . . .
* don't do send them our money . . .
Let them continue to live like it is the 7th Century . . .
.
spamhog
Your answers convinced me that resistances were too off from normal.
I decided to pop the MLB open, and there's what I found:
- case is made with two pipe-end caps and a pipe section completely
hidden between them
- caps are glued together only where they meet, and "top" cap slightly
glued to top end of pipe section
- no glue on the much broader facing surfaces of pipe and the upper
cap
- "bottom" cap is solidly resin glued to the internal pipe and the two
can't be separated
- top cap pops off rather easily by sticking a flat screwdriver where
the caps meet, with moderate damage
- bottom cap, where the SO239 is, is potted in resin and you can't
free the socket without destroying everything
- the top cap, where the wire tie-post is, has a small hole in which
the stainless steel is bolted and sealed with what looked like a thin
veil of resin
- the tie-post screw with nuts counter-nuts, multiple washers, can be
completely freed
- as expected, there was a small RF autotransformer potted in a resin-
filled plastic cylinder approximately 20mm dia. x 15mm lenght
- the RF transformer shows extremely low and normal resistance
- all excess resistance was due to bad contacts
--- between components of top bolt
--- between large washer and body of SO239
- I could easily clean up the top bolt
- I could not do the same to the potted bottom contacts.
To fix the bottom contact I resorted to a work-or-bust trick: massive
DC! I slammed DC from a variety of low voltage power supplies, and
resistance quickly but gradually decreased while the whole socket
warmed up. I reached the peak of about 15A at which my most powerful
PS trips sensing short. At that point the potted contact had no
measurable resistance, stopped heating, and reliably tripped the PSU
short protection.
I think there might have been moisture leaking in, and the overcurrent
must have burned out whatever corrosion results there where. I
scratched the resin and resealed the contact, left the whole thing out
in the ambient humidity, and after a couple of weeks resistance is
still nil.
I'll now bolt and glue it together and ad some more external
weatherproofing. Not perfect, but should hold up. So all things
considered, I'd say that a constipated RF Systems Magnetic Longwire
Balun with an intact transformer is repairable.
If it does not hold up and resistance rises again (hopefully in
another 15 years or so, I can recover the transformer and change the
whole outer can and SO239.
John Smith
> ...
> If it does not hold up and resistance rises again (hopefully in
> another 15 years or so, I can recover the transformer and change the
> whole outer can and SO239.
If all else this fails, and you wish to reclaim the potted core, grab a
pint of methylene chloride based paint remover. Soak the potted
assembly in a small amount in a small glass container. The resin should
fall off after a couple/few hours, unwinding, a bit of brushing and a
rinse should leave you with clean core. Count the turns as you remove
them and pay attention to the winding methods if you want to reconstruct
exactly ...
Regards,
JS
RHF
- another 15 years or so, I can recover the transformer and change the
- whole outer can and SO239.
SH,
Buy one of these "Beverage Matching Units"
and it will last 50 Years or more . . .
http://www.iceradioproducts.com/reconly.html#Beverage%20Matching
Shortwave : 180A - Isolation Unit - Freq : 1.5-30 MHz
MW & SW : 182A - Isolation Unit - Freq : 0.1-30 MHz
.
spamhog
> http://www.iceradioproducts.com/reconly.html#Beverage%20Matching
> Shortwave : 180A - Isolation Unit - Freq : 1.5-30 MHz
> MW & SW : 182A - Isolation Unit - Freq : 0.1-30 MHz
Thank you, I know those, and they seem better than the MLB, but are
too large and heavy for hanging up. The MLB is quite tiny and light.
I think in the past ICE made some versions that could be used in
transmission.
I had asked RF-Systems if their MLB could be used for transmitting,
they reiterated that the MLB is receive-only, but unofficially added
that up to 5W RF was OK and wouldn't saturate the core.
I can confirm that a random wire + MLB + coax can be tuned up via a
transmitter-side ATU and won't smoke on 5W.
spamhog
> Many/most SWLers are simple DIYers
> and not Ham-Techies : "KISAP"
> = Keep It Simple And Practical - iane ~ RHF
ha ha ha! And I'd like to add that I hadn't asked any question even
remotely related to the pros and cons of the concept of broadband
impedance matching between coax and random wire, how good this
specific RF-System MLB un-un implementation was, detailed instructions
for DIY alternatives, and the semantics of calling magnetic "balun"
something that isn't so. Such replies push (s+n)/n to unity.
Ian Jackson
<cf132157-f196-438c...@l17g2000vbf.googlegroups.com>,
spamhog <n1...@hotmail.com> writes
matcher/tuner, and good, low-loss coax, you can do away with the
transformer.
--
Ian
dave
>>
> And I can confirm that, with a transmitter-side (shack end)
> matcher/tuner, and good, low-loss coax, you can do away with the
> transformer.
All that does is match the 50 Ohm transmitter to the 50 Ohm (or less)
transmission line. It doesn't address the mismatch between the
transmission line and the antenna at all.
RHF
> Ian Jackson wrote:
>
> > And I can confirm that, with a transmitter-side (shack end)
> > matcher/tuner, and good, low-loss coax, you can do away with the
> > transformer.
- All that does is match the 50 Ohm transmitter
- to the 50 Ohm (or less) transmission line.
- It doesn't address the mismatch between the
- transmission line and the antenna at all.
Isn't there a little factors like cutting the Antenna
Wire to the 'right-length' and having the 'correct
length' of Coax Cable that contribute to a good
"Match" : At least for one SW Band ? ~ RHF
.
John Smith
>
> ...
> ha ha ha! And I'd like to add that I hadn't asked any question even
> remotely related to the pros and cons of the concept of broadband
> impedance matching between coax and random wire, how good this
> specific RF-System MLB un-un implementation was, detailed instructions
> for DIY alternatives, and the semantics of calling magnetic "balun"
> something that isn't so. Such replies push (s+n)/n to unity.
Yeah, I was too wordy, should have been, "Toss the piece of cr*p and
get/wind something decent ...
Regards,
JS
John Smith
> ...
> ha ha ha! And I'd like to add that I hadn't asked any question even
> remotely related to the pros and cons of the concept of broadband
> impedance matching between coax and random wire, how good this
> specific RF-System MLB un-un implementation was, detailed instructions
> for DIY alternatives, and the semantics of calling magnetic "balun"
> something that isn't so. Such replies push (s+n)/n to unity.
Funny, your very first post contained, "I am rebuilding my 15+ yr old
longwire+MLB antenna due to broken coax etc etc. ... "
Then, you just shoot a lot of amps though wire that was NEVER meant to
take the amps, this is obvious by the manufacturer saying not to run 5
watts though it. And, I have never ran a heavy, magnetizing current,
though a toroid to see attempting to turn my core into a magnet would
suddenly be "a good idea."
Etc., etc. But, I will agree you didn't ask ... you just did a lot of
pretty nutty stuff ... so now you have an old corroded balun which you
have exceeded current on, heated the winding and their insulating
coating to gawd knows what temp, are counting on all this making good
contact on corroded joints, etc., etc.
And then you are afraid what someone said may "sound nuts?" ROFLOL
Now, let me see if I see anything wrong with all that?
I think rebuild it properly, or buy a new one, or build a new one, etc.,
etc. are all better than what you seem to be proud of ... but hey, that
is just me ... and I admit it ...
Regards,
JS
arthr...@webtv.net
>
> - Show quoted text -
...not if the potato comes from China !!!
spamhog
> you just shoot a lot of amps though wire that was NEVER
> meant to take the amps, this is obvious by the manufacturer
> saying not to run 5 watts though it.
No, I didn't do that. I agree, it might have fried the wire or
magnetized the toroid. The problem was all between the outer shell and
the ground lug-washer on the SO239 side of the device. That contact
was not accessible as it was potted in resin. I had already removed
the magnetics. The 15A flowed only through lug-washer and the outer
conductor.
>>> Isn't there a little factors like cutting the Antenna
Wire to the 'right-length' and having the 'correct
length' of Coax Cable that contribute to a good
"Match" : At least for one SW Band ? ~ RHF <<<
The MLB is meant to give a good-enough, install-and-forget, receive-
only match between a 50 ohm line and a random wire whose Z wildly
gyrates between 30-1000 ohm in and out of the complex field. Any RF
transformer turning 50 ohm into 300 to 600 ohm is vastly superior to a
direct connection.
There are receivers that include exactly that kind of transformer
between the inputs for "50 ohm" and "600 ohm" or "wire". I have seen
such transformers working reasonably well all the way between .1 and
30MHz. The MLB is nothing special but works like that, on a 300/1
bandwidth. The Lowe 124-225-250 etc. contain such a transformer, and
work OK down to 30 (thirty) kHz, a 1000/1 bandwidth. By "working" I
just mean that a given signal from a wire antenna produces
dramatically better results when fed via the transformer than direct
to 50 ohm input. That improvement geverally jibes with the source
being hi-Z.
I've never been able to reproduce such broadband behavior in a toroid
I wound myself. The Palomar Associates MLB clone was OK but weaker on
MF-LF. The ICE ununs come in lower and higher frequency range
versions. I have no idea what the trick is in the transformers used by
Lowe and RF-Systems, but it must be very simple, e.g. a mix that
compromises by having a somewhat higher loss all over or by saturating
at low power levels [over 5W :) ], but that's just a guess. It has to
be smtg that normal 1:9 ununs made with the usual HF mixes don't do
terribly well.
As for transmission: go on a ship, and if it's old enough you might
still even see a nice chunky metal case with the leftover transformer
matching the MF or low-HF random wire to a coax, complete with anti-
flashover insulator. Every time the radio room was removed from the
wire antenna, it made economic sense to deliver the 100-1000W RF by
standard radio guide (coax) than via a special high-voltage, high-
impedance line made wire suspended inside a large copper pipe.
In the real (professional) world NOBODY in at least the last 30 years
tried to cut MF or HF antennas to resonate on a special frequency.
Broadcasting dipole arrays were ~ 2:1, MW (AM) towers (and even VHF-
UHF antennas in space applications back in the day) are roughly sized
for radiation angle requirements, not for natural resonance. A 5/8
lambda vertical is like that.
Professional broadband dipoles normally "guarantee" a SWR mismatch
under 3:1 over 2-30MHz, and I remember UHF space applications with
1:10 SWR on short coax lines that were compensated at the radio end of
short low power and low loss coax runs. In many applications antenna
mismatch is practically irrelevant as long as it does not multiply
losses in the transmission line.
It's a consideration that corresponds to the cos-phi concern in
electric power transmission. A wild mismatch may generate extra
current or voltage that will cause additional Joule loss in conductor
and dielectric. In power transmission, 50-60Hz wavelength is so large
that you don't really get localized voltage peaks and throughs due to
reflected and direct power interference patterns, but at RF you see
that too, so you get both added losses and extra insulation breakage
risk. But if the run is short, and the power is low, both losses and
overvoltages can be safely ignored, and reflection and Z mismatch can
be addressed at the radio end.
In a long coax run, the huge mismatch of a nonresonant wire to a lo-Z
coax is nontrivial, and a transformer can actually nicely cooperate
with an ATU at the other end.
Today's AUTOMATIC ATUs are now routinely placed at the antenna end.
Not needing human attention, it makes sense to move them over there,
in which case a RF transformer becomes irrelevant. Antenna-side MF
transformers on ships are a thing from the indoor manual ATU and early
automatic ATU era.
But even today, antenna side transformers are the rule in the HF
market. That's what you do to improve match between a generally-high
impedance antenna and a low impedance coax of a broadband dipole. The
few rhombics still in use either have a Z-transforming balun or an
extremely low loss and broadly Z-matched balanced HV line. Ditto for
beverages - you could just connect coax and wire, but it would be
lossy, and nobody does it.
The broadband no-transformer no-ATU alternative exists. In practice,
only the military can afford the metal masses of large HF antennas
that have no clear resonance and reasonably narrow Z range without RF
transformer [and w/o resistor... :-P ], like inverted-cone on ground
plane, double-cone dipole, discone. Also (few) hams use log-periodic
rotatables. An MIT dorm used to have a fixed LP all-wire ham antenna,
never heard of a ham using a fixed "half-LP" vertical wire curtain.
Even with such antennas I'd still leave an automatic ATU in line if
already available. And, not coincidentally, such antennas are
generally sized for >13 MHz. Below that it's mostly broadband wire &
transformer country.
>"Toss the piece of cr*p and get/wind something decent ... "
Yes, one can surely do that!
((narrower response or you tell me the simple trick for practicable
300:1 width) and/or (heavy, ground level or masthead commercial unit)
and/or ((buying toroid, casing, connectors, strain-relief, sealant)
and (winding, drilling case, installing strain relief, connectors,
soldering, sealing)))
vs.
(solder, glue, seal, use :)
spamhog
True, but not necessarily a problem. The battlefield is kept out, on
antenna and transmission line. On the radio side of the coax you do
see a function of the remote mismatch both in terms of wrong impedance
and in terms of a partly reflected wave delayed by the travel time
back and forth and with I/V out of phase due to the reactance at the
other end. What an ATU does is
1- compensating the reactive mismatch so that the power source sees a
resistive load
2- rephasing the incoming reflected wave to match the outgoing
3- providing impedance transformation at the transmitter end.
The result is maximized power transfer, and a clean load from the
p.o.v. of the transmitter, w/ minimized apparent reflection. I think 1
and 2 are mathematicaly dual to each other (please someone confirm!).
Not so sure how 3 fits in but it prolly does.
The price you pay for this is a nice mess along the transmission line,
with power being reflected back and forth in an infinite convergent
series of quickly dropping factors until radiated by the antenna, or
lost en route to heat and line radiation, while minimizing the stress
on the transmitter.
Nodes with higher current and voltage along the way also increase
Joule losses - but, again, this may be the dual of expressing the loss
due to reflection, I am not sure if there is a nonlinearity at work
here.
Having everything matched with the minimum use of concentrated L and C
is beneficial (inside the radio, in the ATU, in the transmission line,
and appended to the antenna), but if the transmisson line is very
efficient and not overly stressed (foam or air insulated, decently
sized conductors and insulator, not overheating nor breaking
insulation) a matching network close to the radio side is bearable.
Quite characteristically, as frequencies rise losses mount. Losses
along the same line at a similar mismatch may be negligible at LF,
acceptable at HF, excessive at V-UHF. This is why this is so often
done in professional applications.
In general. an antenna side matching device is better than radio side,
and no matching network is better than with, but perfection is not
always indidpensable. For example, the advantages of radiating in a
certain geometry (e.g. a Yagi, a nonresonant vertical...) or with
greater radiation resistance, may more than compensate for additional
losses due to a necessary concentrated-reactance matching device.
Ian Jackson
<7ff52d12-9d66-4082...@n7g2000vbo.googlegroups.com>,
spamhog <n1...@hotmail.com> writes
Since Dave's dismissal of my suggestion/confirmation, I started several
draft replies, but each time got bogged down in detail. However, I think
that Spamhog's posting sums up the situation pretty well.
What must be realised is that you are not using the tuner/matcher (at
the radio end of the coaxial feeder) to match into the 50 ohm Zo of the
coax, and then, as an afterthought, connecting a totally mismatched
antenna on the far end. What actually happens is that the antenna feed
impedance is transformed by the electrical length and the Zo of the
feeder (and also its loss), and the tuner/matcher (at the radio end) is
adjusted so that it matches whatever impedance is 'seen' looking into
the feeder. It matches the whole antenna system, ie the antenna plus
feeder.
Admittedly, this arrangement only works well if the feeder losses are
low. Unless the antenna is (fortunately) a good match to the feeder, the
SWR on the feeder will be high, and the losses could be much higher than
if the there was a good match at the antenna end. It follows that, to
minimize the loss, you need to use the lowest loss type of feeder you
can lay your hands on. Nice, chunky CATV trunk cable is a good choice,
if your friendly neighbourhood cable company can be persuaded donate
some to you - especially as fibre optics are rapidly replacing coax.
Note that this is certainly not the 'best' way of doing things. For
receiving, it may - or may not - work better than using a 9:1
transformer at the antenna end. Both arrangements are a compromise.
However, you can certainly transmit with this system and, from what I
understand, at considerably higher powers than you can transmit through
a 9:1 transformer. Low-loss TV coax is probably OK for 100 to 200W,
although, for really high powers, you may need to think about the
implications of high SWR, voltage breakdown, and current burn-out. Of
course, an auto-tuner at the antenna end would be the best, but they
don't work on receive-only.
--
Ian
Geoffrey S. Mendelson
> Admittedly, this arrangement only works well if the feeder losses are
> low. Unless the antenna is (fortunately) a good match to the feeder, the
> SWR on the feeder will be high, and the losses could be much higher than
> if the there was a good match at the antenna end. It follows that, to
> minimize the loss, you need to use the lowest loss type of feeder you
> can lay your hands on. Nice, chunky CATV trunk cable is a good choice,
> if your friendly neighbourhood cable company can be persuaded donate
> some to you - especially as fibre optics are rapidly replacing coax.
Decent quality RG-6 coax is easy to find at any of the home improvement
type shops, satellite TV dealers, etc. It's a lot better than the RG-59
or RG-59/U that was sold in the past.
Compression connectors are reliable, easy to use and can be bought for as
low as $12 (plus postage) a set including instalation tools. Really good
ones and really good tools sell for around $50 for a set of 50 connectors
and a tool, which are cheap enough and make a great group purchase.
You can also get BNC and RCA connectors of similar design, if you need
adaptors to your radio, and the are easier to get than "F" adaptors.
For those with Belling-Lee, aka PAL or just antenna connectors from
outside the US, you can get them at Radio Shack, Universal Radio, or
a pack of 30 for around $15 including postage from Hong Kong or the UK.
> Note that this is certainly not the 'best' way of doing things. For
> receiving, it may - or may not - work better than using a 9:1
> transformer at the antenna end. Both arrangements are a compromise.
> However, you can certainly transmit with this system and, from what I
> understand, at considerably higher powers than you can transmit through
> a 9:1 transformer. Low-loss TV coax is probably OK for 100 to 200W,
> although, for really high powers, you may need to think about the
> implications of high SWR, voltage breakdown, and current burn-out. Of
> course, an auto-tuner at the antenna end would be the best, but they
> don't work on receive-only.
The biggest confusion is what an antenna tuner does. The ones sold for ham
radio are often assumed to resonate the antenna because a transistorized
radio transmitter needs a resonant antenna.
They do that, but ONLY from the point of view of the transmitter. At the
transmitter end of the coax, the antenna, when properly tuned, APPEARS
resonant, so the transmitter does not "blow up".
In reality, it is no more resonant than it was before the tuner was used.
Too many people believe that it actually changes the antenna to be resonant.
Cor Beijersbergen posted a link in the Yahoo Shortwave-SWL-Antenna list to
a usenet posting from long ago by John Doty. Here is the link and my reply:
http://www.iw5edi.com/ham-radio/?swl-longwires,47
It's an interesting article.
There are two points I'd like to make.
The first is that the article is 14 years old.
That's important to note because he says:
"No man made or atmospheric noise is included. If they are significant,
the precision of the match becomes less critical. "
Where I am both kinds of noise are significant. To the point that I get
S9 or greater noise on those frequencies which are not dependent upon
propigation, and S9 or greater noise on propigation dependent signals
when "the band is open". In 1996 the noise was insignificant.
"The better (smaller) the noise figure, the less you have to worry about
matching. Sky Buddy owners will want to tune their antennas very
carefully."
When he wrote this, my Kenwood R-5000 was a new, high performance
receiver. There were only a few receivers in its class, e.g. the
NRD-525D, the ICOM R-70/R-71, and the Drake R8.
My R-5000 has just celebrated its 20th birthday, so I expect that low
noise figure receivers are common now.
I do know that my Sony ICF-2010 (actually older than the Kenwood) needs
a preamp/preselector (Ameco PT-3 in my case) to equal the Kenwood, my
recently aquired Drake SPR-4 (even older) is as good as or better.
So I really don't think a matching transformer will do much for me.
Geoff.
--
Geoffrey S. Mendelson N3OWJ/4X1GM
To help restaurants, as part of the "stimulus package", everyone must order
dessert. As part of the socialized health plan, you are forbidden to eat it. :-)
dave
>
> What must be realised is that you are not using the tuner/matcher (at
> the radio end of the coaxial feeder) to match into the 50 ohm Zo of the
> coax, and then, as an afterthought, connecting a totally mismatched
> antenna on the far end. What actually happens is that the antenna feed
> impedance is transformed by the electrical length and the Zo of the
> feeder (and also its loss), and the tuner/matcher (at the radio end) is
> adjusted so that it matches whatever impedance is 'seen' looking into
> the feeder. It matches the whole antenna system, ie the antenna plus
> feeder.
>
No. What do you mean by "match"?
Ian Jackson
<da...@dave.dave> writes
'output' to 50 ohms resistive at its 'input'. That way, a transmitter
feeds into a 50 ohm load - which is normally what it will be designed to
feed into.
When receiving, the same applies (although, of course, the signal is
passing through the tuner/matcher from the opposite direction). Its
'input' on transmit is its 'output' on receive, so the output (which
feeds the receiver) is 50 ohms - which is what most communications
receivers are designed to be fed from. In practice, if purely receiving,
you will normally simply twiddle the tuner/matcher for strongest signal
on the receiver (ie maximum smoke). It doesn't really matter too much
whether or not you actually achieve 50 ohms at the matcher 'output'
port.
Or have I got things wrong?
--
Ian
Ian Jackson
Mendelson <g...@mendelson.com> writes
>
>
>Decent quality RG-6 coax is easy to find at any of the home improvement
>type shops, satellite TV dealers, etc. It's a lot better than the RG-59
>or RG-59/U that was sold in the past.
>
If possible, if the coax is fairly long, I'd try and 'acquire' something
a bit less lossy than RG6 (at 50MHz, 5dB/100m, 1.5dB/100'. For cable TV,
RG11 (3.1dm/100m, 0.95dB/100') is sometimes a 'long drop' alternative to
RG6 or RG7. But you can do better than that. A Google should bring up
specs. This site gives a good selection. The CATV trunk cables look
interesting, but will usually be literally a bit 'too hard to handle'.
<http://caledonian-cables.com/product/Coaxial%20Cables/coaxial.htm>
--
Ian
Geoffrey S. Mendelson
> When receiving, the same applies (although, of course, the signal is
> passing through the tuner/matcher from the opposite direction). Its
> 'input' on transmit is its 'output' on receive, so the output (which
> feeds the receiver) is 50 ohms - which is what most communications
> receivers are designed to be fed from. In practice, if purely receiving,
> you will normally simply twiddle the tuner/matcher for strongest signal
> on the receiver (ie maximum smoke). It doesn't really matter too much
> whether or not you actually achieve 50 ohms at the matcher 'output'
> port.
It's more a question of what is 50 ohms? As in the input impedance of this
receiver is 50 ohms and performance degrades rapidly if the source impedance
is not 50 ohms, or this radio has an unbalanced input socket on the back so
we'll say it's 50 ohms but it does not really matter.
It's even more complicated by the fact that most receivers that are designed
for 50 ohm input, are not 50 ohms throughout their entire range.
Some have tunable front ends, for example my Ten-Tec 509 and 544 (both
transceivers) and my Drake SPR-4 receiver. My Kenwood units (receiver
and transceiver) do not.
The Kenwood receiver has both a coax (claimed to be 50 ohm) and separate
binding post antenna input with the binding post one having 50 ohm and 600
ohm connections.
In my experience, connecting a random wire antenna to any made no
difference, they all worked the same for the same antenna.
Using a coax feedline (and connecting it to the coax input) made a big
difference in noise, but that's due to the amount of noise produced by
me and my neighbors.
As for an antenna tuner, or external preselector, in my experience they just
shift signals up or down the s-meter scale, without changing the signal
to noise ratio. In fact, I've taken to using the antenuator on the Kenwood
to shift everything down, so I hear less noise. Signals are also weaker,
but the audio gain control compensates for that.
Obviously you can not make a general statement from that as every receiver is
different and probably so is every antenna.
I assume if you had a receiver with a less tight filtering system, or a looser
front end, it would be a boon to use a preselector, or an antenna tuner as one.
My Sony ICF-2010 really does get a performance boost using my Ameco PT-3,
which is a preselector and 18db (adjustable) gain pre-amp.
So yes, tuning your antenna tuner for "maximum smoke" would give you a louder
signal, but it may or may not give you a better one. YMMV.
Geoffrey S. Mendelson
> If possible, if the coax is fairly long, I'd try and 'acquire' something
> a bit less lossy than RG6 (at 50MHz, 5dB/100m, 1.5dB/100'.
Since this is an SWL group, a more meaningful number would be 15 mHz, and
I'm not sure that a loss of 1.5dB is going to noticable. 5dB would, but how
many people have 100m runs of coax?
Ian Jackson
Mendelson <g...@mendelson.com> writes
>Ian Jackson wrote:
>> If possible, if the coax is fairly long, I'd try and 'acquire' something
>> a bit less lossy than RG6 (at 50MHz, 5dB/100m, 1.5dB/100'.
>
>Since this is an SWL group, a more meaningful number would be 15 mHz, and
>I'm not sure that a loss of 1.5dB is going to noticable. 5dB would, but how
>many people have 100m runs of coax?
>
his salt should be able of 'translating' the loss figures from 50 to
15MHz!!
--
Ian
Ian Jackson
Mendelson <g...@mendelson.com> writes
>Ian Jackson wrote:
>> When receiving, the same applies (although, of course, the signal is
>> passing through the tuner/matcher from the opposite direction). Its
>> 'input' on transmit is its 'output' on receive, so the output (which
>> feeds the receiver) is 50 ohms - which is what most communications
>> receivers are designed to be fed from. In practice, if purely receiving,
>> you will normally simply twiddle the tuner/matcher for strongest signal
>> on the receiver (ie maximum smoke). It doesn't really matter too much
>> whether or not you actually achieve 50 ohms at the matcher 'output'
>> port.
>
>It's more a question of what is 50 ohms? As in the input impedance of this
>receiver is 50 ohms and performance degrades rapidly if the source impedance
>is not 50 ohms
'Rapidly'?
>, or this radio has an unbalanced input socket on the back so
>we'll say it's 50 ohms but it does not really matter.
>
>It's even more complicated by the fact that most receivers that are designed
>for 50 ohm input, are not 50 ohms throughout their entire range.
>
Some receivers probably don't even have a good 50 ohm input impedance in
ANY part of their tuning range.
Are you saying that there are likely to be problems when using a
tuner/matcher between an antenna and a receiver? I think that such
problems may happen, but are probably rare.
>Some have tunable front ends, for example my Ten-Tec 509 and 544 (both
>transceivers) and my Drake SPR-4 receiver. My Kenwood units (receiver
>and transceiver) do not.
>
>The Kenwood receiver has both a coax (claimed to be 50 ohm) and separate
>binding post antenna input with the binding post one having 50 ohm and 600
>ohm connections.
>
>In my experience, connecting a random wire antenna to any made no
>difference, they all worked the same for the same antenna.
>
I recall that it was the same with my old R107 WW2 receiver (made in
1943?). It has a low-impedance balanced dipole input, and a
high-impedance long wire input. With one side of the balanced input
connected to the ground/case, and a single wire antenna, you can't
really tell any difference, whichever input you use.
>Using a coax feedline (and connecting it to the coax input) made a big
>difference in noise, but that's due to the amount of noise produced by
>me and my neighbors.
>
Regrettably, such interference avoidance techniques are now essential -
even in the countryside!
>As for an antenna tuner, or external preselector, in my experience they just
>shift signals up or down the s-meter scale, without changing the signal
>to noise ratio. In fact, I've taken to using the antenuator on the Kenwood
>to shift everything down, so I hear less noise. Signals are also weaker,
>but the audio gain control compensates for that.
>
You might expect this. Even in the absence of manmade interference, at
HF, the SNR is essentially determined by the SNR of the signal coming
from the antenna. The receiver adds negligible noise (well, up to around
20MHz).
Are you running the RF gain at maximum? Apart from (usually) being
necessary to obtain the 'correct' S-meter reading, when you are actually
listening, it's a good idea to back it off as far as is necessary to
keep the AGC just working (on SSB, at least). Of course, using the front
end attenuator does allow the AGC to function flat out but, again on
SSB, even with the best of receivers, you still get the inevitable rise
of background noise during gaps in the speech (especially if the gaps
are long). I find this very unpleasant - especially on strong signals.
Somehow, the AGC time constant never seems to be correct - for my ears,
at least.
>Obviously you can not make a general statement from that as every receiver is
>different and probably so is every antenna.
>
>I assume if you had a receiver with a less tight filtering system, or a looser
>front end, it would be a boon to use a preselector, or an antenna tuner as one.
>
Some receivers are easily overloaded when fed from a good antenna
(especially if the input attenuator - if present - is switched 'out').
They are sometimes unusable unless the 'pre-input' signal is filtered.
In such cases, the primary requirement is a preselector - and not a
matcher. A 'matcher' may - or may not - be sufficiently selective to
provide sufficient filtering action. There times when it may provide
little - or no - rejection of those signals which are upsetting the
receiver (even if these are a long way from the frequency you are trying
to receive).
>My Sony ICF-2010 really does get a performance boost using my Ameco PT-3,
>which is a preselector and 18db (adjustable) gain pre-amp.
>
>So yes, tuning your antenna tuner for "maximum smoke" would give you a louder
>signal, but it may or may not give you a better one. YMMV.
>
And I'm sure that, on the odd occasion, a tuner/matcher may actually
make reception worse. If so, it is probably not what the receiver needs
- or rather, its design is not what the receiver wants. As I said, many
receivers need preselection rather than antenna system matching. Maybe
some need both.
--
Ian
Geoffrey S. Mendelson
> Are you saying that there are likely to be problems when using a
> tuner/matcher between an antenna and a receiver? I think that such
> problems may happen, but are probably rare.
If you have a tuner/matcher designed for 50 ohms and the receiver
does not have a 50 ohm impedance, it might not work. It depends upon the
receiver's ability to work with input impedances that don't match it, the
tuner's ability to match other than 50 ohm impedances and so on.
As you say, probably rare.
> I recall that it was the same with my old R107 WW2 receiver (made in
> 1943?). It has a low-impedance balanced dipole input, and a
> high-impedance long wire input. With one side of the balanced input
> connected to the ground/case, and a single wire antenna, you can't
> really tell any difference, whichever input you use.
This does not have a dipole input it has a coax jack (antenna 1) and
three binding posts (ground, 50 ohm, 600 ohm) for antenna 2.
> Regrettably, such interference avoidance techniques are now essential -
> even in the countryside!
I would not know, I have not been what could be described as out in they
countryside in years. I joke that it used to be when a new town was being
built the first thing that went up was a flagpole. Now it's a cell tower.
> You might expect this. Even in the absence of manmade interference, at
> HF, the SNR is essentially determined by the SNR of the signal coming
> from the antenna. The receiver adds negligible noise (well, up to around
> 20MHz).
Most of mine a quiet all though their range.
>
> Are you running the RF gain at maximum? Apart from (usually) being
> necessary to obtain the 'correct' S-meter reading, when you are actually
> listening, it's a good idea to back it off as far as is necessary to
> keep the AGC just working (on SSB, at least). Of course, using the front
> end attenuator does allow the AGC to function flat out but, again on
> SSB, even with the best of receivers, you still get the inevitable rise
> of background noise during gaps in the speech (especially if the gaps
> are long). I find this very unpleasant - especially on strong signals.
> Somehow, the AGC time constant never seems to be correct - for my ears,
> at least.
I've tried both. To my ears the sometimes keeping it at max but using the
antenuator works best, sometimes reducing the rf gain works best, and
sometimes both works best. It's a combination of the signals, propigation
and noise.
> Some receivers are easily overloaded when fed from a good antenna
> (especially if the input attenuator - if present - is switched 'out').
> They are sometimes unusable unless the 'pre-input' signal is filtered.
> In such cases, the primary requirement is a preselector - and not a
> matcher. A 'matcher' may - or may not - be sufficiently selective to
> provide sufficient filtering action. There times when it may provide
> little - or no - rejection of those signals which are upsetting the
> receiver (even if these are a long way from the frequency you are trying
> to receive).
I'm sure some of the cheap portables I have will do that, but the ones
that have outside antennas have good front ends.
> And I'm sure that, on the odd occasion, a tuner/matcher may actually
> make reception worse. If so, it is probably not what the receiver needs
> - or rather, its design is not what the receiver wants. As I said, many
> receivers need preselection rather than antenna system matching. Maybe
> some need both.
This comes back to the original question, how well does a 1:9 transformer
really help? The article I posted the link to says that it does in a low
noise environment with a high noise receiver. With a low noise receiver in
a high noise environment it helps less. Less was undefined and not measured
in the article.
At one time someone was selling a universal matching dipole center insulator.
It claimed to match any dipole at an swr approaching 1:1 over the HF ham/SWBC
bands and CB. It really did. Inside was a 50 ohm resistor.
I wonder how well it would perform as a random wire matching transformer?
If it would reduce my s9+ noise to s0 or s1, and proportionaly reduce
any received signals, it would. :-)
dave
> In message <4c98e12b$0$5508$bd46...@news.dslextreme.com>, dave
>>>
>>
>> No. What do you mean by "match"?
>>
> The tuner/matcher transforms whatever impedance that is connected to its
> 'output' to 50 ohms resistive at its 'input'. That way, a transmitter
> feeds into a 50 ohm load - which is normally what it will be designed to
> feed into.
>
> When receiving, the same applies (although, of course, the signal is
> passing through the tuner/matcher from the opposite direction). Its
> 'input' on transmit is its 'output' on receive, so the output (which
> feeds the receiver) is 50 ohms - which is what most communications
> receivers are designed to be fed from. In practice, if purely receiving,
> you will normally simply twiddle the tuner/matcher for strongest signal
> on the receiver (ie maximum smoke). It doesn't really matter too much
> whether or not you actually achieve 50 ohms at the matcher 'output' port.
>
> Or have I got things wrong?
You are describing a "transmatch" when used between the generator and
the transmission line. This prevents the VSWR from frying the
transmitter. It does nothing to make the antenna work any better. The
transmitter can feed 50 Ohm co-ax directly. A tuner at the far end of
the transmission line will improve radiation while matching the load to
the transmission line and back to the transmitter. The radiation
improvement may be negligible or more dramatic, depending on the type of
antenna. When receiving you don't worry about frying the transistors
(unless you have a 2001D/2010!) so you just want to make sure you don't
break the hose rule (NO Higher Z generator into Lower Z load). That is
why a 9:1 transformer works OK for receiving. If you transmit through it
the transmitter will see close to a short circuit if the antenna is
resonant.
dave
Davis RF Buryflex is da shit.
dave
> Ian Jackson wrote:
>> If possible, if the coax is fairly long, I'd try and 'acquire' something
>> a bit less lossy than RG6 (at 50MHz, 5dB/100m, 1.5dB/100'.
>
> Since this is an SWL group, a more meaningful number would be 15 mHz, and
> I'm not sure that a loss of 1.5dB is going to noticable. 5dB would, but how
> many people have 100m runs of coax?
>
> Geoff.
You'd be surprised. Even at HF, there are QRP applications where a dB or
2 makes a significant difference.
This is a DC to Daylight group.
dave
>>
> I'm simply quoting the figures (as given) as a comparison. Any SWL worth
> his salt should be able of 'translating' the loss figures from 50 to
> 15MHz!!
I'm a Dreaded No Code Amateur Extra and I have to look it up.
dave
> Are you running the RF gain at maximum? Apart from (usually) being
> necessary to obtain the 'correct' S-meter reading, when you are actually
> listening, it's a good idea to back it off as far as is necessary to
> keep the AGC just working (on SSB, at least). Of course, using the front
> end attenuator does allow the AGC to function flat out but, again on
> SSB, even with the best of receivers, you still get the inevitable rise
> of background noise during gaps in the speech (especially if the gaps
> are long). I find this very unpleasant - especially on strong signals.
> Somehow, the AGC time constant never seems to be correct - for my ears,
> at least.
>
I wouldn't consider buying a receiver for serious listening if it didn't
have the ability to turn off the AGC completely, and if it din't have an
RF gain control. You can get SSB to sound like FM. Back when GHFS was
happening you could leave it on 11176 USB 24/7 and never hear anything
between the calls except the occasional chirpsounder bloop. If you were
also listening to 8993 on another radio, you'd hear the same bloop a
half second earlier or later, give or take.
Ian Jackson
<da...@dave.dave> writes
>Ian Jackson wrote:
>> In message <4c98e12b$0$5508$bd46...@news.dslextreme.com>, dave
>
>>>>
>>>
>>> No. What do you mean by "match"?
>>>
>> The tuner/matcher transforms whatever impedance that is connected to its
>> 'output' to 50 ohms resistive at its 'input'. That way, a transmitter
>> feeds into a 50 ohm load - which is normally what it will be designed to
>> feed into.
>>
>> When receiving, the same applies (although, of course, the signal is
>> passing through the tuner/matcher from the opposite direction). Its
>> 'input' on transmit is its 'output' on receive, so the output (which
>> feeds the receiver) is 50 ohms - which is what most communications
>> receivers are designed to be fed from. In practice, if purely receiving,
>> you will normally simply twiddle the tuner/matcher for strongest signal
>> on the receiver (ie maximum smoke). It doesn't really matter too much
>> whether or not you actually achieve 50 ohms at the matcher 'output' port.
>>
>> Or have I got things wrong?
>
>You are describing a "transmatch" when used between the generator and
>the transmission line.
Of course I am.
>This prevents the VSWR from frying the transmitter.
Of course it does.
> It does nothing to make the antenna work any better.
Well, it certainly doesn't change the match of the antenna. However, it
does match the combination of antenna plus feeder.
Consider that good old-fashioned multiband antenna for the HF amateur
bands - 132' centre-fed, fed using low-loss 450 or 600 ohm twin feeder,
with a transmatch at the shack end. The antenna feed impedance will vary
greatly from band to band, and is highly unlikely to be a match for the
feeder on any of them. As a result, there will be a considerable SWR on
the feeder, and the impedance at the transmitter end will also be all
over the place. However, with a transmatch at the transmitter, this
arrangement performs very satisfactorily on all the HF amateur bands.
This is because the high impedance feeder has inherently much lower loss
than most coaxes. If you do the same thing with an endfed wire and coax,
almost certainly it isn't going to work as well - especially on the
higher HF frequencies. But it does work.
> The transmitter can feed 50 Ohm co-ax directly.
But only if the impedance looking into the 50 ohm coax is 50 ohms.
> A tuner at the far end of the transmission line will improve radiation
>while matching the load to the transmission line and back to the
>transmitter.
Of course it does. But, unless you invest in an auto-tuner, it's not
easy to adjust the far-end tuner. And, even if you invest in an
auto-tuner, it only works if you transmit first.
> The radiation improvement may be negligible or more dramatic,
>depending on the type of antenna. When receiving you don't worry about
>frying the transistors (unless you have a 2001D/2010!) so you just want
>to make sure you don't break the hose rule (NO Higher Z generator into
>Lower Z load). That is why a 9:1 transformer works OK for receiving.
Well, it's a compromise. On average, it improves the matching between
the antenna and the feeder, so it is 'a good thing'.
> If you transmit through it the transmitter will see close to a short
>circuit if the antenna is resonant.
It all depends on which resonance. If it's halfwave resonant (or
multiples), the antenna impedance will be very high (5000 ohms?) and,
even with the 9:1 step-down, the coax would still see a load of a lot
more than 50 ohms at the antenna end. If it's quarterwave resonant (or
odd multiples), the antenna feed impedance will be low (35 ohms?), and
yes, the 9:1 step-down will mean that the coax sees a very low impedance
load. But, with such mismatched conditions, the impedance back at the
transmitter/receiver end will depend on the electrical length of the
coax, its Zo, and its loss.
Using a 9:1 impedance transformer certainly isn't a prefect system. One
posting said that you could actually transmit low power through it.
However, it probably won't be very efficient - especially as ferrite
transformers do NOT like working under mismatched conditions. You have a
good chance of burning out the transformer. One the other hand, using
the equally imperfect 'tuner-in-the-shack' method, you can transmit
reasonably high power - although, if the coax is lossy, quite a bit of
your power simply heats it up.
--
Ian