Re: [Discuss-gnuradio] power amplifiers on TX

[Daniel Pocock]

On 30/12/15 22:24, Marcus Müller wrote:
> Hi Daniel,
> Cannot stress this enough:
> Don't try to do everything to the max right from the start. Sure, 100mW
> is a lot less than what can do in the licensed bands, but then again,
> not coming from an amateur background, 120W right out scare me. Please
> make sure no more than -15dBm are fed into the USRP RX. So at an output
> power of 120 W ~= 51dBm, you need isolation of at least 66dB between
> your TX antenna and the RX port of your USRP for the TX frequency. Also,
> considering you're buying a device that can potentially cover 70MHz to
> 6GHz, spending lots of money on a powerful amplifier that can but
> operate on a few MHz really sounds like an unbalanced investment. Maybe
> reduce the output power (unless you want to do moon bounce, maybe), and
> get separate filters, just to keep the option of not operating in
> 144-147MHz; your whole operational range is much smaller than the amount
> of spectrum you can control with the USRP at once.
> 
> Of you're not going to use two highly directive antennas for RX and TX
> to achieve isolation:
> You will either need an RX/TX switch (that you should definitely control
> using the USRPs GPIO pins, which can be programmed to certain states
> when transmitting, receiving or doing full duplex) to isolate RX from TX
> when transmitting, or an extremely expensive circulator-based device.
> 


As this isn't specific to ham radio, I created a dedicated page about
transceivers on the wiki, including some of your feedback:

https://gnuradio.org/redmine/projects/gnuradio/wiki/HardwareTransceiver

Can anybody else add more specific examples of RX/TX switches they have
used, cases and heatsinks for putting everything together, etc?