Phase Matched Specifications

[xmutantson]

Hi,

I was wondering what the phase matched cable specs are because I need to make my own with much longer cables. I primarily work in VHF (2 meter ham band) and the length of the included coax is a constraint, as I am trying to make a spacing of greater than 50cm radius. All my coax exits through a window on one side of the car, and the kraken is already mounted in the car very close to this window.

Since phase matched cables from the leading names are PROHIBITIVELY expensive for the lengths i will need (15+ feet) I am thinking of getting a VNA and creating phase matched cables. I just need to know what will produce a result that is “good enough” if that makes sense. By the antenna spreadsheet, I should get a resolution better than 15 degrees, and I don’t want to compromise this by more than a couple of degrees by poorly matched coaxial cable.

What would be a really good trick is if the kraken itself with it’s phase coherent channels could be used to assist in the construction of phase matched cable sets, but as other tools exist that probably do this better, I’m willing to obtain them.

[krakenrf_carl]

The 2m band isn’t very sensitive to coax length differences. If you can get a precision within 1-2 cm you will be fine. Using a VNA to measure cable length or phase directly should yield you good results.

[JohnnyT]

I had the same challenge and this folding tray solution works out well for me. Here is my setup for a 17 inch radius covering the 2m band. Parts used:

• Tray
• High strength velcro for the KrakenSDR and pi4.
• Wire loom sleeve and zip ties
• Cable tie magnets
• Labels for the antenna end of cables

[krakenrf_carl]

Nice, that looks like a really neat setup!

One caution, those roof rails could possibly refract or partially block the incoming wave from some angles, especially if they are metal. Not sure if it will have a huge effect, or only minor.

[JohnnyT]

Thanks for the tip. I did notice the occasional random lobes when the signal to the side. Not enough to prevent a lock, but it did bounce around some.

[GTG]

Thanks for the inspiration for the head rest mount.
I ended up using a $7 piece of Kydex. A couple of 1/2" holes for the head rest posts holds it all up.
Printed the KrakenSDR mount someone made on Thingiverse and attached it to the kydex.

[KrakenRF]

This is nice. I’m jealous.