Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 2 3 4 [5] 6 Next   Go Down
  Print  
Author Topic: Staions hear me, but I can't hear them  (Read 9702 times)
W5DXP
Member

Posts: 3630


WWW

Ignore
« Reply #60 on: June 15, 2013, 07:49:04 PM »

The SWR numbers on Steve's site speak for themselves.

Since Steve's SWRs were obtained using EZNEC, I wonder why they are acceptable to you while my G5RVjr SWRs using EZNEC are not acceptable? In any case, here they are from Steve's web page:

80m, 3.2:1; 40m, 4.9:1; 20m, 2.5:1

Using 75 ft. of RG-213 results in the following losses according to VK1OD's transmission line loss calculator:

80m, 0.45dB; 40m, 0.97dB; 20m, 0.75dB

0.97 dB of loss is about 20% and is about 1/6 of one S-unit.

When you asserted that 100 watts into a G5RV results in QRP radiated power levels, you are asserting 13 dB of loss in a G5RV. So exactly where is the additional 12dB of loss coming from? If you actually measured 13dB of loss, something should have been getting pretty hot.

Quote
He's not a fan of G5RV folklore either.

I also doubt that he is a fan of anti-G5RV folklore, e.g. your alleged 13dB of loss. Here's a quote from Steve's web page:

"80m, 40m, 20m, 15m, and 12m exhibit moderate VSWRs which should be within the matching range of an external tuner, and for which the losses in a short length of good-quality coax would likely be acceptable."

A G5RV is what it is and obeys the laws of physics. It is not a gift from God or the Devil's design. When properly designed and installed, it has acceptable performance on part of 80m, 40m, 20m, and 12m. It's performance may be unacceptable on the other HF bands. Invariably, when a G5RV doesn't perform well, it is because it is not designed well, not installed well, or being used by a ham who doesn't understand the characteristics of a G5RV.
« Last Edit: June 15, 2013, 07:52:18 PM by W5DXP » Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
AC2EU
Member

Posts: 415


WWW

Ignore
« Reply #61 on: June 15, 2013, 09:07:43 PM »

The SWR numbers on Steve's site speak for themselves.

Since Steve's SWRs were obtained using EZNEC, I wonder why they are acceptable to you while my G5RVjr SWRs using EZNEC are not acceptable? In any case, here they are from Steve's web page:

80m, 3.2:1; 40m, 4.9:1; 20m, 2.5:1

Using 75 ft. of RG-213 results in the following losses according to VK1OD's transmission line loss calculator:

80m, 0.45dB; 40m, 0.97dB; 20m, 0.75dB

0.97 dB of loss is about 20% and is about 1/6 of one S-unit.

When you asserted that 100 watts into a G5RV results in QRP radiated power levels, you are asserting 13 dB of loss in a G5RV. So exactly where is the additional 12dB of loss coming from? If you actually measured 13dB of loss, something should have been getting pretty hot.

Quote
He's not a fan of G5RV folklore either.

I also doubt that he is a fan of anti-G5RV folklore, e.g. your alleged 13dB of loss. Here's a quote from Steve's web page:

"80m, 40m, 20m, 15m, and 12m exhibit moderate VSWRs which should be within the matching range of an external tuner, and for which the losses in a short length of good-quality coax would likely be acceptable."

A G5RV is what it is and obeys the laws of physics. It is not a gift from God or the Devil's design. When properly designed and installed, it has acceptable performance on part of 80m, 40m, 20m, and 12m. It's performance may be unacceptable on the other HF bands. Invariably, when a G5RV doesn't perform well, it is because it is not designed well, not installed well, or being used by a ham who doesn't understand the characteristics of a G5RV.


I never "alleged" any specific loss figure, those are YOUR words! Now you sound like you want to indict me for a G5RV hate crime! OK I admit it, I think the G5RV is a hyped up magical mystery antenna. Guilty!   Roll Eyes
Look at the numbers! For some reason you want to put lipstick on this pig, for instance, you show a frequency that is OUTSIDE of the 40 meter band (7.8 MHZ). Nobody cares about 7.8 MHZ !   Shocked  Whats up with that?  Sorry, but It smacks of obfuscation. Why not be consistent and do something like show the center frequencies for each band? ( one must choose the G5RV frequencies carefully?)
Look, if you want to further tout benefits of this non resonant disaster, please start a thread about it. We are hijacking the OP's thread with this off topic stuff.  Embarrassed
Logged

KD2CJJ
Member

Posts: 369




Ignore
« Reply #62 on: June 15, 2013, 09:43:00 PM »

Unfortunately good information but nothing that is going to help you in this situation.  just remember Z = R + jX  where Z is Impedance, R is Resistance and jX is reactance.  Ideally jX = 0, R = 50 and Z = 50.  jX will tell  you where your resonance point is where it is 0.  That MUST be in the band you want to operate in.  If not then your antenna is useless and many other factors will come into play.  R is less of an issue and will vary depending on types of antennas - not all antennas are 50 Ohm by nature but all antennas will be close to resonance within the band you want to operate in. 

Also, make sue your using your analyzer at the antenna and NOT at the operating position.  You want to first get your antenna tuned... Then introduce the feed-line system.

When you get your new analyzer look for the R and X values and report back.  Also your analyzer should be able to tell  you if you have a fault/short in the line.. let us know that also. 

Question, does your balun have any lightning suppressor built into it?

Quote from: K7KBN
Quote from: KD8TZC
No, my analyzer only has Z (which I thought was found by adding reactance to known impedance of the line... so if I measure my line and I know it is 50 ohms, and lets say the Z reading is 350 ohms, then wouldn't the reactace be 300?)

No.  Think of it as a right triangle with one side 50 and hypotenuse 350.  The length of the third side is the reactance.


And that still isn't quite right.  There seems to be confusion among impedance (a complex or
vector quantity), the magnitude of impedance (which is what the analyzer reads), and the
expected values of those along a feedline.

Impedance has two components:  either resistance and reactance in rectangular coordinates, or
magnitude and phase in polar coordinates.  It's like looking at a map, where you have both
north/south and east/west dimensions.

Z is the magnitude of the reactance:  equivalent to the distance from the center of a map.
It doesn't tell you which direction you went in, or how far you are away from a particular point.
It would be more useful if we were trying to match an antenna to 0 ohms rather than 50 ohms.
But you can get a 50 ohm Z value with a perfect 50 ohm load, in case the SWR would be 1 : 1,
with perfectly reactive loads, inductive or capacitive (where the SWR is infinite), or some other
combination thereof.  There may be a few cases where Z is a useful value in antenna work,
but not as many as one might think.

The impedance on a feedline is determined by the load impedance at the far end, the
characteristic impedance of the line, and the electrical length of the line.  You can't assume
that the R value of a complex impedance is the same as the characteristic impedance of
the line:  R will vary along the line.  About the best you can say is that, if the SWR on the
line isn't 1 : 1, then at no point along the line will the (complex) impedance be equal to the
characteristic impedance of the line:  you can have the resistive component equal in some
spots along the line, but those points will have a reactive component such that the SWR is
constant along the line (except for line losses.)

So, yes, the magnitude of impedance ( Z ) is given by the Pythagorean theorem using the
R and X components of impedance, but R is usually NOT equal to the characteristic impedance
of the line.

There seems to be a wealth of rich information here, but I don't even know what I should be looking at... I apologize.  I'm just a tech, and this seem really far above my head, but I need to learn it.  Anyway you can dumb this down so this dumb Hungarian can understand it... I apologize for asking, but I didn't want to let this information that you are trying to share with me go to waste.

On a different note, I ordered a Rigexpert AA-54 yesterday that should be here on Tuesday or Wed, so hopefully I can give more information than just the Z value in a few days.
Logged

73

Mike
KD2CJJ
W5DXP
Member

Posts: 3630


WWW

Ignore
« Reply #63 on: June 15, 2013, 10:06:28 PM »

I never "alleged" any specific loss figure, ...

Here's what you alleged: "100 watts into a G5RV on most bands will probably radiate in QRP class".

QRP CW is usually a maximum of 5 watts. 100 watts in and 5 watts out is 13dB of loss or 5% efficiency. I would suggest that your implied 5% efficiency estimate is off by more than a magnitude on the bands where the G5RV performs well.
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KD8TZC
Member

Posts: 67




Ignore
« Reply #64 on: June 16, 2013, 11:24:19 AM »

VE3TTF: Holy crud... I never realized that... very strange as I have been having conversations with people on the 2M band going through this switch.

KD2CJJ & Others: Thanks for the info... I will report back once I get the analyzer.  I'll also do as you say and take the reading at the antenna first and tune first from there.

For those having the pissing match about the G5RV... can we take that someplace else as that is totally off topic from what I initially asked.  I know the G5RV is a controversial antenna system, and I'm not really interested in it here.  Yes I have one, but that is not the antenna that I am using right now and it is in storage presently.
Logged

John - KD8TZC
WH7DX
Member

Posts: 1029




Ignore
« Reply #65 on: June 16, 2013, 11:33:16 AM »

Hearing aid....   Grin
Logged
N6AJR
Member

Posts: 9912




Ignore
« Reply #66 on: June 16, 2013, 11:58:08 AM »

The original g5rv was a pretty goo antenna on 20m and would work in places on other bands. sometimes the ladder line acted as a feed line and sometimes its part of the antenna, and so on. also the MFJ switch will work on 2m and 440 , but it is not designed  to work there and you are gettings substantial loss on uhf/vhf and even some what on 6 meters.  if you are working repeaters , you will probably not notice, but on 2m ssb or cw, you will. try this, go up and run the coax straight into the  10 m dipole and shorten it up to somewhere around 8 foot per side.just fold the ends over and twist them back on the dipole. see how that works. go a step at a time and see what you  find out. work one step at a time until you find the problem, ( switch radios, switch coax, etc). also have a ham friend come over and see what he sees. some times a fresh set of eyes helps.  please keep us posted and let us know what is the problem when you find it. and sometimes the propagation seems to be "one way" so  there is always that.  are they ( the other stations ) using wires also, or do they have a big beam.  if so they will hear and tx better and you with an indoor antenna may not be able to hear them.  good luck, and ignore all the "comments" on the ability of other antennas.  there is no "magic, " its all about physics.









Logged
W5DXP
Member

Posts: 3630


WWW

Ignore
« Reply #67 on: June 16, 2013, 12:28:46 PM »

For those having the pissing match about the G5RV...

Whoever introduced the G5RV subject to this thread should be tarred and feathered. Smiley
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K0IZ
Member

Posts: 738




Ignore
« Reply #68 on: June 16, 2013, 06:32:41 PM »

I suspect that the fairly large difference between low SWR and low impedance (ie reactance) frequencies is due to one side of dipole is being affected by nearby objects more so than other side.  Thus imbalance.  Seems to me the only way to check out antenna is to attach analyzer directly to antenna, and adjust each side of antenna for some semblance of 10M resonance.  Probably need to adjust each side somewhat separately.

350 ohms reactance is quite a bit, and as someone posted earlier, your radiation might be more from feedline than antenna.  With that much reactance, your balun might be acting more as an isolator.  And a vertical (more or less) radiator has low angle of radiation.  So you get ground wave, and DX, but nothing in between.

I also doubt you have anything wrong with your radio.  You definitely have something wrong with the antenna, and having two separate problems at same time (ant and radio) is unlikely.

Now, about that G5RV .....
Logged
KG4OLW
Member

Posts: 168




Ignore
« Reply #69 on: June 17, 2013, 12:23:10 AM »

Transmit and Receive are reciprocal. That is, if you are running 100 watts and the station you are in contact with is running 100 watts the received signal power at each end of the link will be the same. You say the other fellows give you S-9 and so you should receive them S-9. It appears there is something wrong with your receiver.

Just an FYI Reciprocity is a myth:


The Reciprocal Myth

The electrical properties of any given antenna are reciprocal. For example, any gain (or lack of it) they exhibit applies equally to transmit and receive. However, in the real world, the performance between transmit and receive is not reciprocal. This is due to a variety of reasons, not the least of which is takeoff angle. Further, improperly installed HF mobile antennas may have their radiation pattern overly distorted, which exacerbates the performance difference. There are many more variables too. I mentioned SNR, and ERP above, and to it we add; atmospheric noise, propagation phenomena, and even ground losses, to name a few.

In fact, the difference between transmit and receive performance can be rather extreme; sometimes you can hear better than you can be heard, and sometimes the reverse is true. So when you make a pat statement like, I can work any station I can hear, you're kidding yourself. However, if the statement is factual, you need a better antenna and/or mounting scheme!


Source Alan: http://www.k0bg.com/myths.html
Logged
WX7G
Member

Posts: 6146




Ignore
« Reply #70 on: June 17, 2013, 05:39:49 PM »

The "myth" page you list is a questionable source of information. Here is a link to a paper that covers reciprocity with more authority.

http://www.cv.nrao.edu/course/astr534/AntennaTheory.html

Antenna reciprocity and the radiation pattern:
1. The elevation pattern, or take-off-angle, affects transmit and receive equally.
2. The azimuth pattern affects transmit and receive equally.  

For the ground wave path that is the subject of this thread there is propagation reciprocity as wells as antenna reciprocity.

« Last Edit: June 17, 2013, 06:02:44 PM by WX7G » Logged
AA4PB
Member

Posts: 12907




Ignore
« Reply #71 on: June 17, 2013, 06:35:59 PM »

"Just an FYI Reciprocity is a myth:"

No its not. Reciprocity involves the measured parameters of an antenna like forward gain, front to back ratio, radiation pattern, etc. It doesn't include the effects of things external to the antenna such as noise, etc. An antenna that has a measured gain of 3dB on transmit will also have a measured gain of 3dB on receive. Reciprocity doesn't necessarily mean that you will copy stations any better with it because it may also increase the noise level by 3dB.

« Last Edit: June 17, 2013, 06:40:56 PM by AA4PB » Logged
KD2CJJ
Member

Posts: 369




Ignore
« Reply #72 on: June 18, 2013, 06:26:04 AM »

100% agree... 

Its not a myth but a theory.  Many theories only take into account a perfect world and exclude many factors.  In a perfect world without ground losses, noise, atmospheric conditions, etc. etc. etc. reciprocity in fact would hold true. 

 
"Just an FYI Reciprocity is a myth:"

No its not. Reciprocity involves the measured parameters of an antenna like forward gain, front to back ratio, radiation pattern, etc. It doesn't include the effects of things external to the antenna such as noise, etc. An antenna that has a measured gain of 3dB on transmit will also have a measured gain of 3dB on receive. Reciprocity doesn't necessarily mean that you will copy stations any better with it because it may also increase the noise level by 3dB.


Logged

73

Mike
KD2CJJ
KD8TZC
Member

Posts: 67




Ignore
« Reply #73 on: June 19, 2013, 06:34:58 AM »

Okay, back to the original discussion.  My new analyzer (RigExperts AA-54) came yesterday and I didn't have the time to get up in the attic and take a sweep, but I did have some time to hook it up in the shack and run a sweep on the entire system.  I have Five graphs below.  The first is the SWR graph.  I also have showing in this one all the detailed specs at the 28.450MHz frequency (This is the freq that I am targeting since it is the one that our club uses for the Wed roundtable discussion).  The second graph is the Z=R+jX graph.  The third graph is the Return Loss graph (no clue what this is yet).  The fourth graph is the Z=R||+jX graph (what is the difference between this one at the previous Z graph?  I can see a difference in the plot curves, esp on the X curves which are the green lines but what does all this mean).  And lastly, the Phase Graph (no clue what this is telling me...  do I want this to be 0 degree's at my target frequency?)

I'm sure they are all useful, but to be honest, I'm not sure everything they are telling me.  Z, I sort of get (I think... I want it low, but I think there is a lot more to it than that), and SWR I also get in that I want it as close to 1:1 as possible for my center frequency.

SWR Graph: http://i879.photobucket.com/albums/ab360/perrybucsdad/HAM/2013-06-19_09-10-50_zpsffa3ca91.png
Z=R+jX graph: http://i879.photobucket.com/albums/ab360/perrybucsdad/HAM/2013-06-19_09-11-20_zps97b6b155.png
Return Loss Graph: http://i879.photobucket.com/albums/ab360/perrybucsdad/HAM/2013-06-19_09-11-38_zpsdfe1760e.png
Z=R||+jX graph: http://i879.photobucket.com/albums/ab360/perrybucsdad/HAM/2013-06-19_09-23-46_zpsf6fb3498.png
Phase Graph: http://i879.photobucket.com/albums/ab360/perrybucsdad/HAM/2013-06-19_09-24-13_zpsa4a3998e.png

From what I am seeing, I need to shorten my antenna a little (as was previously discussed).  How much though I will have to experiment with.  I think from my calculations, it was determined that I need to trim 12 inches total, but sage advice was given here to be conservative with that and try just a little bit at first.  As one of the old timers in my club told me, just fold back the antenna on itself so if I shorten it too much, I can always undo it.

I do want to get up in the attic and run a sweep on the antenna itself, but I'm not sure when I will be able to do that.  As it stands now, I doubt I will be able to get up there and adjust it, let alone take a sweep on it, until after field day. 

I do have the 10M net this evening, but I will just run it as is for now.  I know I won't have time to tinker with it tonight before the meeting.

Anyhow, any comments or suggestions pertaining to adjustment would be appreciated.

Also, if you look at the SWR graph, there is a white box with a bunch of information for the 28.450MHz frequency.  One of the attributes it has listed is the Cable Length.  Is this saying that my cable/transmission line looks this long electrically to the analyzer or is it telling me something about its resonance (or something completely different yet)?

Thanks,
Logged

John - KD8TZC
WB2WIK
Member

Posts: 20613




Ignore
« Reply #74 on: June 19, 2013, 10:30:09 AM »

The results are weird in that it appears your antenna system has secondary and terciary near resonances, which it shouldn't.  May be due to the influence of stuff nearby to it.  Normally a dipole will show resonance at 1/2-WL and then all multiples of 1/2-WL, with very high resistance at even multiples and low resistance at odd multiples.

Return loss is an inverse function of SWR.  RL = 0 = VSWR of infinity; RL = infinity = VSWR of 1.0

You can always calculate one from the other.

The "cable length" isn't a measurement on the screen, it's a calculation based on the center frequency you selected and assuming a VF of 0.66 for the transmission line.  If you change the frequency up and down you'll see that change correspondingly.

It appears your antenna is really tuned to about 25.5 MHz!  I don't know what's causing the other "dips" at about 28.95 and 31.95 MHz, but I'd guess coupling influences, or possibly transmission line influences is you don't have a good current balun at the feedpoint.
Logged
Pages: Prev 1 2 3 4 [5] 6 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!