Is resonance really where you get best antenna performance?

[Marconi]

Thanks Jeff, it is the little more recent things I tend to forget.

I spent over a month in the hospital, and as it turned out all I needed was a heart valve replacement. I was really sick though. Don't remember much during that time and the hospital is no fun. When I finally had the operation, I was out in two days, and it was like I was leavening a prision.

The Hospitals were all claiming I had Covid 19 at the time so they could up the bill over $100,000 from 5 different hospitals. They moved me around to get closer to specialists I needed.

The new heart valve probably saved my life. I was told it was 70% blocked and 35% too small...and that was likely due to HBP and Diabetes for many years.

Thank you for the help, I will be calling on you soon.

I have been working on getting my modeling skills back, but I can't do much about the short memory slumps and for sure when I get tired-out and go to sleep. This happens allot and is a bigtime symptom with Covid19 patients. I still feel like I had Covid.

Eddie

Is the list of members on the site sill available?
So far, all the files I've posted only one has worked. That was one I found already in the folder and sent to you. I know that is just me.

I have forgotten how I put PDF files on my computer using my printer and then calling them up to paste them to my posts.

I haven't had any success with using Search either.

 

[The DB]

DB, when you two discussed the location dimension for the length of wire from the tip of the radiator down to the top of the capacitor was there any consideration made for the overall length of the radiator wire or the rings settings?

I don't recall what specifically I used for the overall length, and I don't recall where I got it from, I want to say the imax exposed article that has been floating around the web since long before that, but am not sure.

The reason for the question is because in my tweaking my model including matching the antenna to a perfect match, I also found the length by % of the radiator wire to the capacitor is probably more important to know...rather than just the physical length in inches.

I think I would disagree with this, as its not the % of overall length that seems to matter, but where the capacitor is when it comes to the antenna's voltage/current distribution.

Its been a while but I recall the location being very specific, to the point that I first thought it was odd, move the capacitor to far away from this point in either direction and I couldn't get it to work, even when adjusting the values of the capacitor. Even the value of the capacor, within reason, didn't seem to have nearly as much of an effect as the location of said capacitor.

The important part (again pulling from memory from what, six years ago?) is to get the capacitor in the right place on the voltage and current curves, which would be measured from the tip.

For example, you gave us a capacitor location in inches and in that case the length down from the tip to the top of capacitor would vary the tuning results depending on the overall length of the overall wire was. I see why adjusting the rings might be problematic in real practice.

I want to say that the models from back then showed a feed point impedance that I would expect to see on an end fed half wavelength antenna, so a matching circuit that is either the same or similar to the a99's matching circuit should essentially have a similar effect, at least within reason, which is why I think they included said capacitor in the first place, although this is just speculation on my part.

I hope this makes sense. I'm still having problems with Covid 19 type symptoms, and I'm trying to cope with too many ministrokes in my brain that dimmish my short-term memory.

I was wondering what happened in your absence. Take care. I've had covid myself recently, a mild case of Omnicron, and it was still rough for at least a few days, I can't imagine how bad it would be if I had a severe case...

On the plus side, when it comes to your modeling, I believe I read somewhere recently that the EZnec program was going to end development this year sometime and go completely free, even for the pricier versions out there, so look into that. Development is also going to be ending soon on the 4nec2 software that I use as well...


The DB

 

[Riverman]

I spent over a month in the hospital.

Bless your heart, Eddie.
So glad that’s over.
We’re all hoping you continue to get better.

 

[AudioShockwav]

Thanks Jeff, it is the little more recent things I tend to forget.

I spent over a month in the hospital, and as it turned out all I needed was a heart valve replacement. I was really sick though. Don't remember much during that time and the hospital is no fun. When I finally had the operation, I was out in two days, and it was like I was leavening a prision.

The Hospitals were all claiming I had Covid 19 at the time so they could up the bill over $100,000 from 5 different hospitals. They moved me around to get closer to specialists I needed.

The new heart valve probably saved my life. I was told it was 70% blocked and 35% too small...and that was likely due to HBP and Diabetes for many years.

Thank you for the help, I will be calling on you soon.

I have been working on getting my modeling skills back, but I can't do much about the short memory slumps and for sure when I get tired-out and go to sleep. This happens allot and is a bigtime symptom with Covid19 patients. I still feel like I had Covid.

Eddie

Is the list of members on the site sill available?
So far, all the files I've posted only one has worked. That was one I found already in the folder and sent to you. I know that is just me.

I have forgotten how I put PDF files on my computer using my printer and then calling them up to paste them to my posts.

I haven't had any success with using Search either.

I will send you a PM.

73
Jeff

 

[Marconi]

I was wondering what happened in your absence. Take care. I've had covid myself recently, a mild case of Omnicron, and it was still rough for at least a few days, I can't imagine how bad it would be if I had a severe case...

as for me and Covid, I had some lung congestion, but my heart, kidneys, and liver could have killed me if the lungs we not in fair shape. I was lucky and never got as far as the ICU. I was released after 5 days. That said I still have several of the symptoms.

I also had to have a heart valve replaced a couple of months later.

Thanks for the response DB.

I will post a couple of Imax models as soon as I can figure out the use of PDF files.

Thanks again.

Bless your heart, Eddie.
So glad that’s over.
We’re all hoping you continue to get better.

Thank you Riverman.

How is you Dog? Fine I hope.

 

[Riverman]

Thank you Riverman.

How is you Dog? Fine I hope.

Sent you a PM.

 

[Rick330man]

I have a rig that I set up when I stay out on my boat. It consists of a 102" Radio Shack stainless steel whip for my vertical radiator. It goes into a rail mount. I then connect a 102" piece of 1/4" hollow aluminum for a counterpoise. My Rig Expert analyzer tells me that resonance is at 27.501. My lowest SWR is 1.02:1 at 27.465. When you're hanging out on 27.385 LSB any further efficiencies to be gained by additional time spent tweaking would hardly be noticed. Add that to being over the water and I'm having no problems talking locally or shooting skip all over the U.S.

 

[Handy Andy]

​

Shh...you're cooking the fish...

 

[hotrod]

just ac question ..in my moble setup wilson 5k mag mount .. i get a reading of R=40-45 and x=0 swr of 1.2 -1.3 ...if i try to improve R then my x rises ..should i let it be

 

[ForestRunner98]

just ac question ..in my moble setup wilson 5k mag mount .. i get a reading of R=40-45 and x=0 swr of 1.2 -1.3 ...if i try to improve R then my x rises ..should i let it be

I would leave it. That’s almost on the money. Different things can affect your readings, even the connectors. How does it RX and DX? If it’s working well then its just splitting hairs.

Just my $.02 and what I have been chasing. Similar numbers and my radio/antenna DX’s like a mofo…not that “Mofo” but like a mutha!!!

 

[Handy Andy]

The shorter antenna designs - read this as less than 1/4 wavelength or like the 5K is shorter than a 102" whip - the "R" value changes - goes lower - when the antenna is shorter than it should be.

• - it then has to add length by using inductance (coil wind) to restore that "X" value
• - but it cannot compensate of bring the R-value back up to 50Ω
• - to make the SWR Impedance closer to 50Ω the XL is added
  • - but adding that extra wire cannot bring back R except for being what the antenna "appears as" to the system - an antenna with a Lower R - which means it's offset by winds of wire to balance out Z to be closer to 50Ω
• Your R value even though the antenna is shorter - helps to reduce the needs of the antenna having to REQUIRE extra wire because it can't make up the difference in height "Big R versus Little R ". - which helps reduce the dependence of Z (Impedance) requiring XL and XC having to make up the difference (your Conjugate used by the antenna)

Just leave it be. LOW SWR to the radio seems to be more important that to attempt to re-work values for an antenna design - you're better off to design your own antenna in various lengths and see R as different - it can even change by location on the vehicle itself - be ready.

 

[Alexis Mercado]

You can skip coax from measurement by using 180° coax or use measurement device can treat coax as transparent.
Mike

How you calculate that ?

 

[sp5it]

Half of the wavelength * velocity factor.
But... Velocity factor depends on frequency, so best way is to use SWR meter and transmitter to get precise length. (Or VNA)
Want me to elaborate how to do that empirically?
Mike

 

[Alexis Mercado]

Half of the wavelength * velocity factor.
But... Velocity factor depends on frequency, so best way is to use SWR meter and transmitter to get precise length. (Or VNA)
Want me to elaborate how to do that empirically?
Mike

Ok. With a half wave length coax taking into consideration velocity factor. Thanks.

 

[sp5it]

To do it precisely you do it:

Measuring Quarter Wave Coax Stubs using MFJ Analyzer

The MFJ Analyzer products make easy work of tuning a coaxial quarter wave stub.

www.hamradio.me

For example: you need 180°coax for 27.200
You measure quarter wave stub for 13.600 and it makes 1/2 for 27.200