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ANTUINO antenna analzer CERTAIN CLARIFICATIONS REG

LAKSH MUTHU
 

HI GOOD DAY TO ALL.

    I recently purchased an ANTUNINO Antenna Analyser.

   I used it to measure the SWR of my antenna system. I erected an inverted VEE antenna system  for  40 m and 20 m bands with a common single coaxial feeder. When  I measured the SWR , the ANTUINO shows the following values.

At    7.007MHZ     SWR is 1.9

At   14.554 MHZ  SWR is 1.8

     Subsequently using the plot function of the ANTUNINO I  measured  the frequencies at which  SWRs are lowest  and the values are as below.

At  15.822MHZ  SWR      is  1.0

At   8.600 MHZ   SWR    is  1.10

At   11.900 MHZ   SWR   is 1.10.

  As such  I cannot understand when the antenna system  has been installed with calculated resonant lengths of arms corresponding to  7 MHZ and 14 MHZ bands, the SWRs are low on some other irrelevant frequencies.  Is there any error /mistake in my observation.?

   . I appreciate, any one, kindly through some light on the above and give some tips on adjusting the system to achieve minimum SWRs in 7 and 14 MHZ (preferably on 7075 MHZ and 14.175 MHZ.

   Thanks a lot in advance

                                                                          With 73

                                                                           MUTHU 

                                                                           VU2LMN

                                                                         +919443114779


Jorge Luiz Fenerich
 

      Hello Laksh, for the measurements you showed your antenna is short, try to increase 5cm at each end of the two antennas and measure again.
Jorge PY2PVT _._

Em qua., 17 de jun. de 2020 às 13:44, LAKSH MUTHU <vu2lmn@...> escreveu:

HI GOOD DAY TO ALL.

    I recently purchased an ANTUNINO Antenna Analyser.

   I used it to measure the SWR of my antenna system. I erected an inverted VEE antenna system  for  40 m and 20 m bands with a common single coaxial feeder. When  I measured the SWR , the ANTUINO shows the following values.

At    7.007MHZ     SWR is 1.9

At   14.554 MHZ  SWR is 1.8

     Subsequently using the plot function of the ANTUNINO I  measured  the frequencies at which  SWRs are lowest  and the values are as below.

At  15.822MHZ  SWR      is  1.0

At   8.600 MHZ   SWR    is  1.10

At   11.900 MHZ   SWR   is 1.10.

  As such  I cannot understand when the antenna system  has been installed with calculated resonant lengths of arms corresponding to  7 MHZ and 14 MHZ bands, the SWRs are low on some other irrelevant frequencies.  Is there any error /mistake in my observation.?

   . I appreciate, any one, kindly through some light on the above and give some tips on adjusting the system to achieve minimum SWRs in 7 and 14 MHZ (preferably on 7075 MHZ and 14.175 MHZ.

   Thanks a lot in advance

                                                                          With 73

                                                                           MUTHU 

                                                                           VU2LMN

                                                                         +919443114779




--
  73 de Jorge PY2PVT
  Campinas SP
  GG67MD

Bill Cromwell
 

Hi,

Does your analyzer tell what the R component (the resistive part) is?

SWR of less than 2:1 is of no importance to me (nor my radios). Ii have operated with SWR around 3:1 but I avoid more than that, even with tube finals. In a 50 ohm system a "perfect SWR should show you 50 ohms. resistance and no other reactance. If I accept some small SWR I want the resistive component on the higher side instead of on the lower side of 50 ohms. I am more interested in R value at my operating frequency and on a sweep I am also interested in that at the lowest SWR.

If you add to the lengths of your antenna it should lower the SWR and move the resonant frequency closer to where you operate. If you get that dip right on your operating range but the SWR is not quite perfect it will probably be very good. With dip where you report it is some effort getting it closer is worthwhile.

73,

Bill KU8H

bark less - wag more

On 6/17/20 12:44 PM, LAKSH MUTHU wrote:
HI GOOD DAY TO ALL.
I recently purchased an ANTUNINO Antenna Analyser.
I used it to measure the SWR of my antenna system. I erected an inverted VEE antenna system for 40 m and 20 m bands with a common single coaxial feeder. WhenI measured the SWR , the ANTUINO shows the following values.
*At 7.007MHZSWR is 1.9*
*At 14.554 MHZSWR is 1.8*
Subsequently using the plot function of the ANTUNINO I measured the frequencies at which SWRs are lowest and the values are as below.
*At 15.822MHZ SWRis1.0*
*At8.600 MHZSWRis 1.10*
*At11.900 MHZSWRis 1.10.*
As such I cannot understand *when the antenna system has been installed with calculated resonant lengths of arms corresponding to 7 MHZ and 14 MHZ bands, the SWRs are low on some other irrelevant frequencies.* Is there any error /mistake in my observation.?
. I appreciate, any one, kindly through some light on the above and give some tips on adjusting the system to achieve minimum SWRs in 7 and 14 MHZ (preferably on 7075 MHZ and 14.175 MHZ.
Thanks a lot in advance
With 73
MUTHU
VU2LMN
+919443114779

 

Hi Laksh,

The formula is not meant to be perfect - it only gives approximations.  If we all lived in outerspace, with nothing near our antennas, use of a formula could be quite reliable, however our antennas are near many objects which affect resonance and the value of R at resonance. 

A dipole at resonance and fed in the middle, has final value of R between about 50-100 ohm depending on height above the ground.

Resonance also change with height above ground -- the closer to ground, the more the antenna needs to be shortened.

Other metal objects nearby affect these too.

Since you have a fan dipole I think, then how close the two wires are to eachother can make a difference and aslo might lead to strange resonances.

The coax lead needs to be brought out midway between the arms -- if it gets near to one side or the other then the coax shield is more likely to become part of the antenna.

73,

Mark

 

For proper SWR readings your dipole must have a 1:1 Balun at the feed point.

The resonant length you have calculated is for plain metal (copper) wire.
Wire coated with plastic will not have the calculated length resonance.

My 40M dipole which intentionally uses plasic insulated wire is 28' on
either side. I could not accommodate 33ft..

Raj


At 17/06/2020, you wrote:

HI GOOD DAY TO ALL.

    I recently purchased an ANTUNINO Antenna Analyser.

   I used it to measure the SWR of my antenna system. I erected an inverted VEE antenna system  for  40 m and 20 m bands with a common single coaxial feeder. When  I measured the SWR , the ANTUINO shows the following values.

At    7.007MHZ     SWR is 1.9

At   14.554 MHZ  SWR is 1.8

     Subsequently using the plot function of the ANTUNINO I  measured  the frequencies at which  SWRs are lowest  and the values are as below.

At  15.822MHZ  SWR      is  1.0

At   8.600 MHZ   SWR    is  1.10

At   11.900 MHZ   SWR   is 1.10.

  As such  I cannot understand when the antenna system  has been installed with calculated resonant lengths of arms corresponding to  7 MHZ and 14 MHZ bands, the SWRs are low on some other irrelevant frequencies.  Is there any error /mistake in my observation.?

   . I appreciate, any one, kindly through some light on the above and give some tips on adjusting the system to achieve minimum SWRs in 7 and 14 MHZ (preferably on 7075 MHZ and 14.175 MHZ.

   Thanks a lot in advance

                                                                          With 73

                                                                           MUTHU 

                                                                           VU2LMN

                                                                         +919443114779

R. Tyson
 

In response to the original post....

Calculating the length of a dipole from the formula is the first stage and gives you an approximate length. It is best to cut the dipole longer than the calculated length and then trim a bit off each end until you get it to resonance.

As others have mentioned, the antenna will be affected by it's suroundings and also any bending out of shape that may be done to get it to fit into the space available.

Mounting the dipole as an inverted  V  will also affect the resonant length and the feed point impedance. The height of the antenna above ground also affects these things.

So you have it up as a inverted  V  fan dipole which appears to be cut too short to resonate where you want it. Pity as it is easier to cut bits off than to add bits to lengthen them.

You need to add wire, allow extra so you can trim it back, you don't want to keep soldering extra bits on. Do this with both the 40 and 20 metre sections ( I think that's what you originally cut it for). As it's a fan dipole start with the longest, 40M, part and slowly trim each end back until your NanoVNA shows you have it resonant where you want it to be.
Once you have the longest section trimmed then do the same with the shorter 20 metre section. There will be some interaction between the 2 fan dipoles and you should trim the longest one and only then trim the shorter one. Then check where the resonance is on both bands again.... you may need some more slight trimming due to their interaction but
chances are it may be O.K. and the job's done.

If you check the SWR it should be below 2:1, it will probably be lower but it would be O.K at that level. 1:1 SWR is very nice but anything below 2:1 will get you on the air.

Reg                        G4NFR

Peter LB0K
 

Muthu - Checking antennas can be confusing.
An antenna only achieves its theoretical impedance and size when in free space, but we don't have long enough feeders for that to ever happen.
In real life we can get a close fit to the theoretical numbers when the dipole antenna is mounted at one half wavelength above ground, whatever 'ground' is. Also at one whole wavelength above ground, about 73 ohms.
One illustration is the graph of 'impedance variation at height over ground' given in the ARRL handbooks and antenna books.
In most of our real situations these sorts of spacing are very difficult to achieve, so we compromise and probably don't get them over a 1/4 wave of 10m or 5m, as in your case. Therefore the 40m section and probably the 20m sections won't achieve anything like 73ohm maybe 50ohm, or under.
These effects pull down the resonance frequency(s) but your antenna doesn't swing on 40m, nor on 20m, indicating that it is too short on both.
As G4NFR suggests make a new one say 5-10% too long, or add on short pieces to similar lengths.

As a rough starting point a 40m dipole will need about 20.5m of wire, a 20m one will need 10m.

The chosen lengths can then be adjusted by folding back the ends and taping them to the 'active portion', while you make more measurements, this way you get a good idea of how much can be easily removed before one cuts tooooo much off. Keep the lengths symmetrical.  I leave mine with a good bit folded back so that when I move the antenna it can be easily be lengthened!
One point not yet answered it that you seem to have an extra resonance in the middle, this is probably coming from one arm of the 40m dipole and an opposite arm of the 20m dipole resonating together.
But perhaps you can't get the projected length suspended above your property, don't despair, just fold the ends down or around.
If you have to cut the ends off, making it too short again, you can use an AMU (aka ATU) to achieve a match.

Now with your analyser you have an exciting time ahead seeing more of what really happens with antennas, and remember you'll see much more of the matching TO the antenna but only a little more of the matching OUT of the antenna into the æther.

Good luck!

Jorge Luiz Fenerich
 

             Thanks for the lesson on antennas Peter, living and learning. Congratulations.
             Jorge PY2PVT _._

Em sex., 19 de jun. de 2020 às 05:10, Peter LB0K <lb0k@...> escreveu:

Muthu - Checking antennas can be confusing.
An antenna only achieves its theoretical impedance and size when in free space, but we don't have long enough feeders for that to ever happen.
In real life we can get a close fit to the theoretical numbers when the dipole antenna is mounted at one half wavelength above ground, whatever 'ground' is. Also at one whole wavelength above ground, about 73 ohms.
One illustration is the graph of 'impedance variation at height over ground' given in the ARRL handbooks and antenna books.
In most of our real situations these sorts of spacing are very difficult to achieve, so we compromise and probably don't get them over a 1/4 wave of 10m or 5m, as in your case. Therefore the 40m section and probably the 20m sections won't achieve anything like 73ohm maybe 50ohm, or under.
These effects pull down the resonance frequency(s) but your antenna doesn't swing on 40m, nor on 20m, indicating that it is too short on both.
As G4NFR suggests make a new one say 5-10% too long, or add on short pieces to similar lengths.

As a rough starting point a 40m dipole will need about 20.5m of wire, a 20m one will need 10m.

The chosen lengths can then be adjusted by folding back the ends and taping them to the 'active portion', while you make more measurements, this way you get a good idea of how much can be easily removed before one cuts tooooo much off. Keep the lengths symmetrical.  I leave mine with a good bit folded back so that when I move the antenna it can be easily be lengthened!
One point not yet answered it that you seem to have an extra resonance in the middle, this is probably coming from one arm of the 40m dipole and an opposite arm of the 20m dipole resonating together.
But perhaps you can't get the projected length suspended above your property, don't despair, just fold the ends down or around.
If you have to cut the ends off, making it too short again, you can use an AMU (aka ATU) to achieve a match.

Now with your analyser you have an exciting time ahead seeing more of what really happens with antennas, and remember you'll see much more of the matching TO the antenna but only a little more of the matching OUT of the antenna into the æther.

Good luck!



--
  73 de Jorge PY2PVT
  Campinas SP
  GG67MD

LAKSH MUTHU
 

DEAR ALL,
        Thank you all for the guiding replies.
Dear Peter, you have given a detailed elucidation. You have pointed out that the probability of an extra resonance in the middle, coming from one arm of the 40m dipole and an opposite arm of the 20m dipole resonating together.In this connection, I am to give my present observation. When I make a short test transmission in LSB mode on 40 m band, there is heavy (RF) feed back. I think this reinforces your finding of the resonating  of  opposite arms together. Am I correct? Dear Peter, Please through some light on this. . Tomorrow, I will change the lengths and position of arms and try again.
     Thanks a million once again
                        73
      MUTHU   VU2LMN

iz oos
 

I would try with a coax choke at the antenna feedpoint and then measure it with Antuino. I would not be too obsessed to find a 1:1 swr unless your transceiver lowers automatically the power output to protect its finals.


Il 20/giu/2020 16:59, "LAKSH MUTHU" <vu2lmn@...> ha scritto:
DEAR ALL,
        Thank you all for the guiding replies.
Dear Peter, you have given a detailed elucidation. You have pointed out that the probability of an extra resonance in the middle, coming from one arm of the 40m dipole and an opposite arm of the 20m dipole resonating together.In this connection, I am to give my present observation. When I make a short test transmission in LSB mode on 40 m band, there is heavy (RF) feed back. I think this reinforces your finding of the resonating  of  opposite arms together. Am I correct? Dear Peter, Please through some light on this. . Tomorrow, I will change the lengths and position of arms and try again.
     Thanks a million once again
                        73
      MUTHU   VU2LMN

Peter LB0K
 

Muthu
There are always new questions, these continue until one realises one is helping others. This is when life gets more interesting.
I omitted making any mention of current, Common Mode, chokes (aka baluns) at the feedpoint, Raj had put that forward, and so has Iz..

Without such a choke at the feedpoint the outside of the feeder coax will ALSO be part of the radiating aerial, and could be making part of an extra resonance. Certainly without such a choke you will easily get the 'RF in the shack' which you now complain of.
My solution is to this phenomenon would be to make a balun/current choke for the feedpoint, and another one for the feeder just before it enters your house or shack. These should stop the RF energy that is obviously following the cable down from the antenna, they won't stop direct radiation from the antenna.   
Another factor in clearing RF feedback is to ensure you do have a resonant load in the antenna, looking at your measurement results you appear to have a very low Q antenna, I doubt if you are radiating much energy at all.

Go back to Start!  - Remake your antenna with a current choke in the feedpoint. Make sure you trim the 40m section first, and then the 20m part.

Using a ferrite core in the current choke will allow it to cover a wider bandwidth, but at a pinch one can wind feeder cable around any magnetic material, even a mild steel bolt will make a difference. Although the most effective, Ferrite Rings are not the only
sort of possible core material.

One expects to see on 40m something like a 1.4:1 to 1.7:1 response at 7.1MHz rising to somewhere over 2:1 or 2.5:1 at the band edges. These are not catastrophic results, instead they are expected.
On 20m one should expect higher values at the band edges maybe 3:1 to 3.5.:1. In Region 1 the band is almost twice the the span of 40m.
As another has pointed out 1.1:1 or even 1:1 matches are not the be-all or end-all aims.

Off you go and experiment a lot more.
And just maybe you'll find time to make contacts on the air, I look forward to a QSO, on 20m?.

Remember to waterproof all the coax connections with vulcanising tape and then cover with black electrical tape to prevent degradation in sunlight.

Peter




Dale Parfitt
 

Hi Peter,

Thank you for the inquiry into our CW/SSB   VHF/UHF Omnidirectional antennas.

Despite 80+ hour weeks, we are running (xx) days behind- thank you for your patience.

 

Please note- we are not accepting amateur orders until likely the 3rd week of July. We have a large backorder log and milcom work. Our apologies.

Pricing is as follows:

OA-50  $119

OA-144 $84

OA-222 $79

OA-432 $79  Type N

All of the above come standard with silver/teflon SO-239.

Type N (silver/teflon) is a $5 option

 

 

Stacking Kits:

SK-50  $56

SK-144 $54

SK-222 $54

SK-432 N/A

 

Allow $17 U.P.S. shipping. On some orders, we can combine cartons to reduce freight costs. Please email us with multiple item orders so we can determine if we can save you money.

We accept PayPal to parinc1@... or send us a check.

 

If you are looking at other antennas, and we encourage you to:

Please ask the manufacturer for an azimuth plot of their antenna or at least an NEC model. Our anechoic tests:

http://www.parelectronics.com/omni-patterns.html

illustrate that the Omniangle design has the best omni pattern in the industry.

 

Also inquire into what means they have employed to reduce common mode RF on the outside of the feedline and/or the mast. If this issue is not address, then the feedline/mast  becomes  part of the antenna. The Omniangles series address these  two important issues as follows:

1. The antenna structure is isolated from the mast- so no  RF on the mast.

2. Employs a built in choke with >2K choking resistance- so no RF on the  outside of the coax.

 

PAR uses aluminum hardware (screws/lockwashers which are more expensive than stainless) in the RF critical junctions so that not only will the  antenna perform well today, but  also years down the road  because of the aluminum to aluminum contact with no galvanic corrosion as would be the case with steel screws.

Mounting hardware is of course stainless steel.

 

Regards,

 

 

Dale Parfitt BSEE/MSEE

PAR Electronics, Inc.

www.parelectronics.com

Voice: (828)743-1338

Toll Free FAX: (866)304-8479

 

 

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Peter LB0K
Sent: Sunday, June 21, 2020 3:26 AM
To: BITX20@groups.io
Subject: Re: [BITX20] ANTUINO antenna analzer CERTAIN CLARIFICATIONS REG

 

Muthu
There are always new questions, these continue until one realises one is helping others. This is when life gets more interesting.
I omitted making any mention of current, Common Mode, chokes (aka baluns) at the feedpoint, Raj had put that forward, and so has Iz..

Without such a choke at the feedpoint the outside of the feeder coax will ALSO be part of the radiating aerial, and could be making part of an extra resonance. Certainly without such a choke you will easily get the 'RF in the shack' which you now complain of.
My solution is to this phenomenon would be to make a balun/current choke for the feedpoint, and another one for the feeder just before it enters your house or shack. These should stop the RF energy that is obviously following the cable down from the antenna, they won't stop direct radiation from the antenna.   
Another factor in clearing RF feedback is to ensure you do have a resonant load in the antenna, looking at your measurement results you appear to have a very low Q antenna, I doubt if you are radiating much energy at all.

Go back to Start!  - Remake your antenna with a current choke in the feedpoint. Make sure you trim the 40m section first, and then the 20m part.

Using a ferrite core in the current choke will allow it to cover a wider bandwidth, but at a pinch one can wind feeder cable around any magnetic material, even a mild steel bolt will make a difference. Although the most effective, Ferrite Rings are not the only
sort of possible core material.

One expects to see on 40m something like a 1.4:1 to 1.7:1 response at 7.1MHz rising to somewhere over 2:1 or 2.5:1 at the band edges. These are not catastrophic results, instead they are expected.
On 20m one should expect higher values at the band edges maybe 3:1 to 3.5.:1. In Region 1 the band is almost twice the the span of 40m.
As another has pointed out 1.1:1 or even 1:1 matches are not the be-all or end-all aims.

Off you go and experiment a lot more.
And just maybe you'll find time to make contacts on the air, I look forward to a QSO, on 20m?.

Remember to waterproof all the coax connections with vulcanising tape and then cover with black electrical tape to prevent degradation in sunlight.

Peter



Dale Parfitt
 

Sorry,

My rep[ly  obviously was not meant for the ubitX group.

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Peter LB0K
Sent: Sunday, June 21, 2020 3:26 AM
To: BITX20@groups.io
Subject: Re: [BITX20] ANTUINO antenna analzer CERTAIN CLARIFICATIONS REG

 

Muthu
There are always new questions, these continue until one realises one is helping others. This is when life gets more interesting.
I omitted making any mention of current, Common Mode, chokes (aka baluns) at the feedpoint, Raj had put that forward, and so has Iz..

Without such a choke at the feedpoint the outside of the feeder coax will ALSO be part of the radiating aerial, and could be making part of an extra resonance. Certainly without such a choke you will easily get the 'RF in the shack' which you now complain of.
My solution is to this phenomenon would be to make a balun/current choke for the feedpoint, and another one for the feeder just before it enters your house or shack. These should stop the RF energy that is obviously following the cable down from the antenna, they won't stop direct radiation from the antenna.   
Another factor in clearing RF feedback is to ensure you do have a resonant load in the antenna, looking at your measurement results you appear to have a very low Q antenna, I doubt if you are radiating much energy at all.

Go back to Start!  - Remake your antenna with a current choke in the feedpoint. Make sure you trim the 40m section first, and then the 20m part.

Using a ferrite core in the current choke will allow it to cover a wider bandwidth, but at a pinch one can wind feeder cable around any magnetic material, even a mild steel bolt will make a difference. Although the most effective, Ferrite Rings are not the only
sort of possible core material.

One expects to see on 40m something like a 1.4:1 to 1.7:1 response at 7.1MHz rising to somewhere over 2:1 or 2.5:1 at the band edges. These are not catastrophic results, instead they are expected.
On 20m one should expect higher values at the band edges maybe 3:1 to 3.5.:1. In Region 1 the band is almost twice the the span of 40m.
As another has pointed out 1.1:1 or even 1:1 matches are not the be-all or end-all aims.

Off you go and experiment a lot more.
And just maybe you'll find time to make contacts on the air, I look forward to a QSO, on 20m?.

Remember to waterproof all the coax connections with vulcanising tape and then cover with black electrical tape to prevent degradation in sunlight.

Peter



Dale Parfitt
 

Hi Peter,

Although the Region 1 20M band  may be close to 2X as wide as 40M, the frequency is also 2X higher- making the percentage  bandwidth virtually the same.

 

Regards,

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Peter LB0K
Sent: Sunday, June 21, 2020 3:26 AM
To: BITX20@groups.io
Subject: Re: [BITX20] ANTUINO antenna analzer CERTAIN CLARIFICATIONS REG

 

Muthu
There are always new questions, these continue until one realises one is helping others. This is when life gets more interesting.
I omitted making any mention of current, Common Mode, chokes (aka baluns) at the feedpoint, Raj had put that forward, and so has Iz..

Without such a choke at the feedpoint the outside of the feeder coax will ALSO be part of the radiating aerial, and could be making part of an extra resonance. Certainly without such a choke you will easily get the 'RF in the shack' which you now complain of.
My solution is to this phenomenon would be to make a balun/current choke for the feedpoint, and another one for the feeder just before it enters your house or shack. These should stop the RF energy that is obviously following the cable down from the antenna, they won't stop direct radiation from the antenna.   
Another factor in clearing RF feedback is to ensure you do have a resonant load in the antenna, looking at your measurement results you appear to have a very low Q antenna, I doubt if you are radiating much energy at all.

Go back to Start!  - Remake your antenna with a current choke in the feedpoint. Make sure you trim the 40m section first, and then the 20m part.

Using a ferrite core in the current choke will allow it to cover a wider bandwidth, but at a pinch one can wind feeder cable around any magnetic material, even a mild steel bolt will make a difference. Although the most effective, Ferrite Rings are not the only
sort of possible core material.

One expects to see on 40m something like a 1.4:1 to 1.7:1 response at 7.1MHz rising to somewhere over 2:1 or 2.5:1 at the band edges. These are not catastrophic results, instead they are expected.
On 20m one should expect higher values at the band edges maybe 3:1 to 3.5.:1. In Region 1 the band is almost twice the the span of 40m.
As another has pointed out 1.1:1 or even 1:1 matches are not the be-all or end-all aims.

Off you go and experiment a lot more.
And just maybe you'll find time to make contacts on the air, I look forward to a QSO, on 20m?.

Remember to waterproof all the coax connections with vulcanising tape and then cover with black electrical tape to prevent degradation in sunlight.

Peter