I was recently gifted a SDRPlay RSP1 (thanks again ON3HVP!) and have wanted to install an RF-tap for a long time in my FT-450.

Now, there’s a couple of ways you can do this:

• Get an extra RX antenna (duh..)
• Tap at the antenna port (but you’ll need to disconnect on TX)
• Tap at the RX circuitry
• Tap at the IF (in case you’re using an RTL-SDR which doesn’t handle HF too well..)

In our case, we’ll tap at the RX circuitry. It doesn’t see any TX power, so it’s all safe. There’s one caveat: you can’t just solder an extra wire and be done with it. If you connect an extra cable and receiver; you’ll load this stage down, causing your receiver to be less sensitive. Not something we want on HF!

Enter a great little board by G4HUP (who is sadly an SK at the time of writing…). The board Dave designed is essentially a high-impedance buffer. So it avoids loading down the RX section, while making sure it has adequate power to drive the input of the RSP1.

Seeing we want the full spectrum delivered to the RSP1 – I chose the “PAT V”-board: no filtering, straight from RX on the transceiver; to the RSP1.

Here’s how it’s all connected:

Lately I’ve been having issues where my CAT commands from Omnirig would time-out or vice-versa. (Notably the dreaded “Rig is not responding”) I had been looking high and low why or who was to blame. Factory resetting didn’t change a thing, nor did changing the serial cable. The settings in Omnirig didn’t matter – nor did serial speed. Hmm, maybe RFI is to blame? – Nope. Turns out – the issue is in the driver for the CP210x dongle! If you use the latest version (at the time of writing – v6.7.5) then you’ll experience these mishaps. (I’m betting other rigs using this chipset will be affected too!