Well, I measured a 6dB improvement.
- SPECAN: SDR-IQ
- TAP: VK5HW (50dB)
- ATT: 20dB
- PWR: 1000W
- ANT: Dummy Load (VSWR 1.08:1)
- Software: SpectraVue V.3.44 Beta 0
Hello and welcome from Australia, or as it's friends like to call it "OZ". Here you'll find a few things I tinker with in my spare time (not that I have much of that), I hope you'll find some of the text informative. 73 Hauke
A quick update on my IM measurements for the ICOM IC-7610 with the new Version (V1.42). This Version is the third installment for the '7610 and this one has the I&Q output fixed. I've not tested this but I believe that quite a few forum members have done so and are over the moon.
Here are a few IM measurements I made after the Firmware upgrade.
Well it was only a matter of time (a long time though) that one of the big three Amateur Radio Suppliers would follow the ANAN "PureSignal" crase.
So what is this Digital Pre-Distortion or DPD for short anyway.
Well, a tiny winey bit of techo talk first.
Every radio has an RF amplifier. This is a component which does add to the performance, and as such to the communication distance of the radio. Sometimes we use an external amplifiers to increase the performance of our radio and even though we call our amplifiers "Linear-amplifier", the RF amplifiers is quite a non-linear device. This nonlinearity creates spectral growth (IM) which leads to interference of adjacent channels.
Please note that the above is a very, and I really mean a very simplified view.
DPD is a technique to linearise an amplifier, which is basically a mechanism to improve the cleanliness of one's transmission, i.e. to reduce the spectral growth, also known as intermodulation (IM) products.
If you like to get a better understanding of DPD, checkout this description, an excellent read.
To enable DPD on the IC-7610 we need to update the Firmware of the radio to the latest firmware version, Ver. 1.40 available from ICOM Japan.
And before we go any further I'll answer the most important question first!
"So is it working?"
Yes!
To show you the difference between DPD and non-DPD I've created a few screenshots using 100W into a RF Dummy Load and using my SDR-IQ as a Spectrum Analyser. The transmitted output power of the radio has been set to 100W for these tests.
Pictures 1 and 2 are using a two tone signal recorded and installed onto the IC-7610 TX Voice memories.
So by cleaning up the signal to feed your amplifier you will gain lots of brownie points within the community.
The next step is to run the adjustments per band you'd like to operate and use DPD on.
Update: