Mobile DF with 2 Arrays switched


I am working on putting together a Kraken Mobile DF for VHF (121.5-243MHz) and UHF (380-512MHz).

The plan is to have 2 arrays drilled into roof. VHF at the front and UHF at the rear. They would be switched via 12V relays either manually or via Kraken software.

Since the radius of the UCA is set in the admin section, this is problematic to adjust in the field.

Is there a way to update the user app to allow for macros or channels that automatically adjust the antenna spacing in software and switch the relays accordingly?

Jim K

What sort of relays would you use here?

We don’t have any way to change the settings between presets at the moment, but we are looking into implementing this.

If you’re a programmer a simple way might be to write a quick program that directly edits the settings.json file with your two preset settings.

I built a switch (array) for a similar purpose (vhf&uhf vs. 750&up) using inexpensive sma rf pcb switches with 5v control found on amazom. The prototype seemed to work fine but never came up with a good way to package them for mobile use. Control is done with a local switch or remotely with a pi zero 2w and a simple web page (like the many control-an-led examples) over wifi. I also use it to turn the ksdr and doa pi on/off.

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Hi all,

I am using 5 of the Ducommun technologies model 2SE1T11JB.

They are 12VDC, 250ma and good up to 26Ghz. These have a failsafe of position 2 when not energized.
Plan is to mount the whole set to a 9x20" piece of plywood and install in the cargo compartment behind the rear 3rd row seat in a Ford Expedition.



I have been testing the Kraken mobile with great success. After measuring what seemed like 16 times, before drilling, the VHF array is working well within expected specs.

I do have a question about overload from LMR radios in the vehicle. The VHF APX radio will cause the kraken board to lock up when running 50 watts. But, not when running low power at 15 watts.

UCA is at the front and VHF LMR antennas are mounted aft at the very back of the roofline.

Is there a trick to help the kracken put up with this scenario?

I have some inline 10DB attenuators on order as a first thought…

Jim K

First, be very careful when broadcasting near the Kraken, it’s not designed to have something broadcasting right next to it, and that could destroy the board. The max input power allowed is +10dBm.

If you want to run a TX next to the Kraken you’ll need to look at some sort of switching mechanism, that can be used to disconnect or ground the antennas during a transmission.

If you add attenuators, then you’re reducing the Kraken’s ability to detect weaker signals.

Thanks Carl.

I have ordered another set of relays to switch to a load under ptt.

Fortunately we have two APX radios installed. VHF and 7/800MHz.

The APX should have a vip output setting to drive a relay when PTT is in use. I’ll dig around in the APX software and figure that out.

More to follow with pix.

Jim K

Much better solution than mine, thanks for sharing!