Software Defined Radio (SDR) technology has started to revolutionize the way we use radio. With low cost SDR hardware and its open source software support , we can set up a high performance radio station at home even using a personal computer.
When we consider SDR as a digitizer hardware which consists of mostly digital circuits, we may have performance issues due to weak analog front-end. On the other hand, conventional radio rigs have strong channelizing input filters, including low noise amplifier, antenna protection and other signal conditioning circuits. Although we have these features in conventional radios, we do not have any software flexibility as in SDR systems. Proper combination of conventional radio front-end along with low cost SDR hardware enables us to create higher performance radio with software flexibility. This addresses us to point proper “RF tapping” panadapter with the rigs already in use.
As radio amateurs, we are using one of the world most popular radio ICOM IC-7300 in our station. This rig is very satisfiying direct sampling radio in terms of price/performance ratio. On the other hand, it has no RF output capability which is a major drawback for its uses. As you can see from online amateur radio resources, having an RF output with ICOM IC-7300 is highly demanded. Amateurs would like to use this rig with low cost popular SDRs like RTL-SDR, AirSpy, SDRplay, HackRF and softwares like HDSDR, SDRSharp, GNU Radio as well.
To meet this demand several attempts have been made by other radio amateurs and companies until now, but non of these solutions were a true panadapter and satisfying either. These were nothing but a method which only splits/switches antenna signal into two paths by sampling one path with SDR, or rerouting antenna signal path into the SDR directly. In other words, these approaches were actually antenna signal tapping rather than internal RF signal tapping. These methods have a lot of drawbacks such as not utilising any of front-end filter, LNA, antenna protection and other signal conditioning features of the rig. We should not classify these solutions as panadapters because these are just antenna signal routing methods without utilizing front-end of the rig.
As we are radio amateurs/engineers who uses ICOM IC-7300 actively, we have worked on ICOM IC-7300 internal schematics, layout and mechanical drawings in order to figure out a true panadapter solution. After heavy brainstorming, we come up with a smart, innovative and seamless way to sample RF signal of ICOM IC-7300. We believe this is the key solution for the radio amateurs who would like to use their ICOM IC-7300 with SDR.
A true panadapter should be able to get integrated into the rig easily, so that anyone can do it by their own without requiring any special skills, such as soldering, cabling, assembling, etc. We have taken following requirements as major guidelines for our design process;
1. RF tapping point should have a connector to avoid any soldering in order to prevent the rig from any damage.
2. There should be an opening on the equipment chassis to take panadapter cable out, extra drilling on the equipment is not allowed.
3. Installing the panadapter should not result any compromise in terms of functionality. For instance if you use tuner connector hole as panadapter access only, you are not able to use external tuner simultaneously.
4. Panadapter should be used with SDR simultaneously, both should be able to tune same or different frequency.
5. Equipment should work properly after panadapter is plugged. No performance degradation such as signal loss or additional noise is allowed.
6. All process should be reversible, so that user can revert the rig back to the original configuration.
All of the outlined requirements above have been met with our innovative approach. We designed, tested and verified PTRX-7300, now we are proud to announce it.