Spacing Calc Help

Discuss KerberosSDR - 4x Coherent RTL-SDR
k2gc
Posts: 15
Joined: Sun Jan 19, 2020 5:58 am

Spacing Calc Help

Trying to figure out how to do the calculation's properly.

my target frequency 144.510

I need to understand what distance apart the antennas should be .

I am not following the calculations properly, but if someone could walk through them using my desired frequency it might help. Once i see it once with real #'s, it will make sense for me....

Thanks
Mike

ckoval7
Posts: 28
Joined: Fri Sep 27, 2019 8:54 pm

Re: Spacing Calc Help

Ideally you want about 1/3 the wavelength.
Wavelength = 300/MHz
In your case 300/144.51 MHz = 2.08m
Then just do wavelength/3
So 2.08/3 = 0.693m
You then make a square where each side is 0.7m.

The current Quickstart guide is a little outdated with having to do more calculations manually. The latest KSDR software allows you to enter your element spacing in meters and the rest happens in the background.

The antenna array will be able to handle a pretty wide range of frequencies at a fixed spacing as long as the spacing between the elements doesn't exceed 1/2 wavelength or fall below 1/10 wavelength. You could build an array for VHF and an array for UHF.

k2gc
Posts: 15
Joined: Sun Jan 19, 2020 5:58 am

Re: Spacing Calc Help

Ok, I think I was on the right track.

But, what is the number I put into the Android software then? is that also my .7? or would that be .33?

Also, I am not sure I spaced my antennas correct. Good news, I have adjustments (hard to see in the pic, but I can move the antennas in and out in 1" increments)

I have them spaced based on the red line, but I am assuming now, I need to set them to the yellow line? If that is the case, i am not sure I made my mounting set up big enough.

BUT. I suspect I can put them at the furthest point, and back my calculation back the other way to get the spacing factor I used?
antenna array.jpg (59.04 KiB) Viewed 1543 times

ckoval7
Posts: 28
Joined: Fri Sep 27, 2019 8:54 pm

Re: Spacing Calc Help

Space it based on the yellow line and just put that measurement into the software. If it's more than 0.2m, you'll get good readings, assuming your cable lengths all match perfectly.

k2gc
Posts: 15
Joined: Sun Jan 19, 2020 5:58 am

Re: Spacing Calc Help

Ok. so measure the yellow line, and that goes in the software (obviously in meters)

Cable lengths are all within 1-2" of each other. they were all brand new mounts with cables on them. I am just not sure how accurate my friend was when he stripped the end and put the PL259's on for me last night (his job is in the radio world, so if he is available I make him put the ends on - much quicker LOL)

k2gc
Posts: 15
Joined: Sun Jan 19, 2020 5:58 am

Re: Spacing Calc Help

After watching a couple of the videos, i need to clarify.

My yellow line - that measurement is what I put in for the spacing factor???

I got the impression it would be the .33?

I worry I have the wrong # entered, and that is part of my issue getting an accurate track.

k2gc
Posts: 15
Joined: Sun Jan 19, 2020 5:58 am

Re: Spacing Calc Help

Oh - i see the note in the startup guide saying it was changed in the latest version.... Oops.

theodeurne
Posts: 5
Joined: Sat Jul 27, 2019 8:16 am

Re: Spacing Calc Help

k2gc wrote:
Mon Jan 20, 2020 5:26 pm
Ok, I think I was on the right track.

But, what is the number I put into the Android software then? is that also my .7? or would that be .33?

Also, I am not sure I spaced my antennas correct. Good news, I have adjustments (hard to see in the pic, but I can move the antennas in and out in 1" increments)

I have them spaced based on the red line, but I am assuming now, I need to set them to the yellow line? If that is the case, i am not sure I made my mounting set up big enough.

BUT. I suspect I can put them at the furthest point, and back my calculation back the other way to get the spacing factor I used?

antenna array.jpg

Nice setup i have also two Array build, one my self and the black one by PA8W.

and

RDF_Guy12
Posts: 1
Joined: Thu Apr 02, 2020 11:33 am

Re: Spacing Calc Help

ckoval7 wrote:
Mon Jan 20, 2020 6:32 pm
Space it based on the yellow line and just put that measurement into the software. If it's more than 0.2m, you'll get good readings, assuming your cable lengths all match perfectly.
Please clarify the "If it's more than 0.2m, you'll get good readings" part of the post. I haven't seen that measurement limitation in any of the notes.

ckoval7
Posts: 28
Joined: Fri Sep 27, 2019 8:54 pm

Re: Spacing Calc Help

RDF_Guy12 wrote:
Thu Apr 02, 2020 10:58 pm
ckoval7 wrote:
Mon Jan 20, 2020 6:32 pm
Space it based on the yellow line and just put that measurement into the software. If it's more than 0.2m, you'll get good readings, assuming your cable lengths all match perfectly.
Please clarify the "If it's more than 0.2m, you'll get good readings" part of the post. I haven't seen that measurement limitation in any of the notes.
They're interested in DFing a frequency with a wavelength of about 2m. The circular array will work with 1/10 to 1/2 wavelength element spacing.