I opted to start with a Flex-1500 SDR radio with outboard transverters and amplifiers. This kept the cost down and after using a Flex-3000 at home as my main HF radio for many years there was no way I was going back to playing "radio blind-man's bluff" with old-school knobs and buttons again. It's a shame that as of this writing Flex has ended production of the 1500 but it had a nice 12-year run and I expect it will hold its value for quite some time.
The little Flex has a low-power IF port specifically for driving transverters and software support which makes it easy to add other bands. I found that UT5JCW sells a nice lineup of low-cost transverters. They fit nicely with my 'low-cost' requirement and I ordered up one each of his 144-28 and 432-28 transverter boards. Since the transverter boards would be doing all the heavy-lifting as far as gain and front-end filtering goes, I was able to meet my 'full-duplex' requirement simply by adding a little RTL-SDR USB dongle as a sub-receiver. A toggle switch and a couple of relays to handle the 28MHz IF switching, a few LEDs, a little box to stuff it all into and I'm almost ready to go.
|With the internal shielding in place and the RTL-SDR dongle connected.|
|The finished product strapped onto the Flex in the portable station.|