I wonder why RG213 does not show velocity factor of 0.66. The formula for calculating VF is: VF = 1/(SQRT(K)), where VF is Velocity Factor, K is dielectric constant. Polyethylene has dielectric constant of 2.3 , so this formula may give you 0.76938... , but it depends of the manufacturer and what actual material they use. It is not possible to calculate velocity factor for foam dielectric.
You inspired me to finally put together a 2 element 40m array. Have one questions on measuring the feedlines and delay line. Should the control box be inline when the measurements are taken to take in account the extra wire length inside the control box?
@@MM0OPXFieldRadio Did my best to make all connections as short as possible inside control box. Even after carful measurement of delay line and feedlines the electrical lengths did change once connected to the control box. So I went back and readjusted the lengths as needed to dial things in while connected to the control box. So far with limited use the array has exceeded my expectations this has been a fun learning project.
Tough question but probably a vertical of some kind. I once had a low to the ground 80m full size horizontal loop. It was NVIS on 80m but good for DX on 40m.
Colin, Great video... I tried the link to the calculator, and it gives a Calculator no longer in service error. Shame because that is really a useful tool. For the most part you can trust the velocity factor of good cables, but it is also frequency dependent. It is sometime good to check it with a VNA or Nano VNA if you have one available. Some of the cheap cable coming from overseas (Asia) you need to check the velocity factor they can be a good bit off. Thanks for the inspiration you provide and the work you do... Still working on the 40m 1/8 wavelength vertical array. I spoke to a broadcast engineer friend. He provided some advice and some things to be careful of in this design.
Appreciate the comments John. I've since made my own Excel calculator. If you would like a copy, send me an email. Once I finish the Moxon I will get back on to the phased verticals again.
The VF is irrelevant as I used the analyser to cut to exact length. You only use the VF to roughly cut the coax before trimming on the analyser at the check frequency.
I wonder why RG213 does not show velocity factor of 0.66. The formula for calculating VF is: VF = 1/(SQRT(K)), where VF is Velocity Factor, K is dielectric constant. Polyethylene has dielectric constant of 2.3 , so this formula may give you 0.76938... , but it depends of the manufacturer and what actual material they use. It is not possible to calculate velocity factor for foam dielectric.
Likely because its a " no name" brand. Great spot 👌
@@MM0OPXFieldRadioYeah, probably not exactly polyethylene, but some mix or something. Great video as always!
You inspired me to finally put together a 2 element 40m array. Have one questions on measuring the feedlines and delay line. Should the control box be inline when the measurements are taken to take in account the extra wire length inside the control box?
I did think about that but when you switch the length changes. Make your switch box as compact as possible and just cut coax as normal.
@@MM0OPXFieldRadio Did my best to make all connections as short as possible inside control box. Even after carful measurement of delay line and feedlines the electrical lengths did change once connected to the control box. So I went back and readjusted the lengths as needed to dial things in while connected to the control box. So far with limited use the array has exceeded my expectations this has been a fun learning project.
Great calculations but is your vision ok cause you writing in between the line .
My vision is still 20/20, my writing is just messy.
A very informative video, many thanks. Does the 90 degree minimum stay the same when the connector is added to the cut end of the cable?
More or less. Ive found it only changes a few khz. Im not too fussy on these lower half of HF frequencies.
if you could only have one HF antenna, what would it be? Wondering if there is a single antenna that will perform well for NVIS and long distance
Tough question but probably a vertical of some kind. I once had a low to the ground 80m full size horizontal loop. It was NVIS on 80m but good for DX on 40m.
Colin, Great video... I tried the link to the calculator, and it gives a Calculator no longer in service error. Shame because that is really a useful tool. For the most part you can trust the velocity factor of good cables, but it is also frequency dependent. It is sometime good to check it with a VNA or Nano VNA if you have one available. Some of the cheap cable coming from overseas (Asia) you need to check the velocity factor they can be a good bit off. Thanks for the inspiration you provide and the work you do... Still working on the 40m 1/8 wavelength vertical array. I spoke to a broadcast engineer friend. He provided some advice and some things to be careful of in this design.
Appreciate the comments John. I've since made my own Excel calculator. If you would like a copy, send me an email. Once I finish the Moxon I will get back on to the phased verticals again.
Quick question for you why would you choose a one quarter phaseline instead of a 1/8 phasing line.
I believe you get a narrower broadside pattern. With the 1/8 wave spacing it's more omnidirectional.
@@MM0OPXFieldRadio thanks for the quick reply really enjoy your videos awesome awesome awesome!
Great video. Really nice to see the math, then see it applied.
Good job Colin,definitely need an analyser for trimming the lines
VERY !! HELPFUL AND THANK YOU SO MUCH FOR SHARING YOUR WORK, BULDING A 2 ELEMENT VERT. FOR 3.825
No problem, hope it helps. Remember to cut your coax for X=0 (zero reactance) which is true resonance.
Thanks Colin, good of you to share this with us, 👍
Are you absolutely sure that the velocity factor is 0.66? Have you measured, calculated, and verified it?
The VF is irrelevant as I used the analyser to cut to exact length. You only use the VF to roughly cut the coax before trimming on the analyser at the check frequency.
yet another great video mate keep it up mate, it's much appreciated, 73's for now
Online calculator above is out of service as of this 12-26-21
I have my own one in the works for free download. I will do a video on this in the coming weeks.
You should always include the units for the values when you do calculations like this.
Noted.
Excellent Colin : )