A Pluto-Based SDR Radio for VHF-SHF Bands

Having discovered F1ATB's Remote SDR package for a Raspberry Pi 5 to remotely control an ADALM Pluto SDR supporting two-way radio communications with FM/SSB/CW/Data modes, it's time to think about how to build a deployable portable/field setup. (Previous post here.)

Below is a simple system drawing showing the local and remote elements of the radio.

I have a basic evaluation setup running and have "talked" to a nearby ICOM IC-705 on two-meters in both FM and SSB modes. Looking through the lab supply totes has yielded items that would be useful in a radio setup (antennas, circulators, amplifiers, filters, RF switches, cables, and more). What bands might be possible with a DIY Remote SDR Pluto Radio (PlutoX)?

Reviewing the capabilities of COTS radios like the very expensive ICOM IC-905 and the basic capabilities of a Remote SDR PlutoX system yields this summary:

X = Covers band. Blank = No Coverage or N/A. Power levels are in Watts.

A survey of on-hand parts shows that running multiple bands in a single setup might be possible. And with some luck, it also might be possible to build two PlutoX radio setups (with RF front-ends for at least a couple of the bands)! This will help for the integration and test of the radios...

The PlutoX TX power level above assumes a Mini-Circuits ZHL-1042J amplifier which supplies a minimum of +20 dBm at 1 dB compression and covers up to 4.2 GHz. Have two of these available for building into PlutoX radios. Also have other modular RF amps that might support higher power on one or more of the bands with the tradeoff that using narrow band amps will complicate the RF portions of the radio (control, filters & switching, etc.).

Antennas are expected to be one of the bigger challenges. As an example, see the IC-905 antennas and cross-bar antenna mounts shown for their demo systems. In Japan, hams run vertical polarization on bands above HF. Here in the USA, horizontal is the norm for SSB modes and vertical for FM/data. This and the question of omni-directional compared to directional antennas (with more gain) needs to be sorted through. It might be quickest to just start with a omni-directional broad-band Discone (vertical polarization) and see how it goes for the bands up to 1 GHz-ish. Have colinear verticals for the 2.4 GHz band that might also work up at 5 GHz. More testing needed.

Still have some questions on how to accomplish T/R switching and learn if full duplex is needed on any of the bands (or if cross-band duplex is beneficial). Lots to learn!

Will post again on the PlutoX concept when more information is available.