The Raspberrypi and the RTL 2832U 820T/820T2 Pan-adapter
First of all, why a pan-adapter? Most of our newer HF rigs, for many years now, have had this feature built in. In fact it s probably difficult to find a recently built HF rig anymore that doesn t incorporate this feature today! Being able to see the signal that you are listening to along with carriers above and below the frequency where you are operating on the band is like having some sense of sight in addition to the sense of hearing in the world of ham radio!
Years ago, back in the mid 60 s this is the kind of panadapter that was available. It was small in spite of the fact it used tubes! It wasn t great definition, but it worked!
It was possible back then to modify the Heathkit Model HO-13 Ham Scan to work as a pan-adapter for receivers such as the Drake R4B which also used tubes too! That s what I did! In the 80 s I modifed one
If you are like me, I happen to prefer pre-smd solid state transceivers from the 80 s, the reason being that they are relatively easy to troubleshoot and work on. You generally don t need a microscope to work on this vintage of equipment either. If you happen to have an older transceiver without a pan-adapter, what options are out there to add that capability?
With the advent of SDR, Software Defined Radio, the options abound today for panadapter choices. It s also not too difficult of a project to accomplish. Of course there are different ways to approach adding a Band- Scope to your transceiver or ham-shack. This option, uses HDSDR, with a SDRPlay 2pro. It uses a Windows 10 desktop computer to run the SDR receiver. It also takes up a significant amount of room, though it does work really well! The hardware also costs $$$!
OPTIONS That option also requires some sort of protection to the input of your receivers, including the SDR, during transmit intervals.
This is my DIY Receive protection switching I can use two transceivers plus my SDR and even a noise antenna. The disadvantage is that it doesn t follow the transceiver tuning, setup this way. I can reconfigure this SDR setup to do that and I have, but I wanted to try Small and Compact!
Here is where the Raspberrypi and the RTL 2832U 820T/820T2 DVB-T HDTV Dongles come into play. These componets are not only small and compact, they are relatively inexpensive!
NooElec NESDR SMArt - Premium RTL-SDR w/ Aluminum Enclosure, 0.5PPM TCXO $24 Original RTL2832U 820T DVB-T HDTV Dongle $8 $28 NooElec NESDR Nano 3: Tiny RTL-SDR USB Set w/ 0.5PPM TCXO
The RTL2832u DVB-T chip + 820T2 Tuner Antti Palosaari, Eric Fry and Steve M of Osmocom discovered that the raw I & Q data of the RTL 2832u chipset could be directly accessed. * This allowed this TV tuner dongle to be re-utilized as an SDR receiver, including the ability to view up to a 3.2Mhz spectrum. Today there are varieties of this dongle being produced specifically for SDR purposes instead of TV. Typical frequency range of the 820T2 Tuner is 25MHz 1700MHz *https://www.rtl-sdr.com/about-rtl-sdr/
Need access to HF below 25MHz? Ham-it-up 125MHz upconverter
$35 Raspberrypi 3 B
The Raspberrypi 3 B 4 Core ARM CPU 1.2 GHz 1Gb of embedded RAM. This little credit card sized computer is OK for what we are after here. If I wanted to also demodulate a signal at the same I would prefer something with more computing horsepower. However you can do that too with this tiny computer!
Tapping the 1 st IF DSP LPF Hi Z Buffer Amp After the 1 st Mixer Before 1 st BP (Roofing) filter
1 st IF Tap Point Yaesu FT1000D
Icom IC-751A
Icom IC-745
Hi-Z Buffer Amp These are a couple my DIY buffer amps. They are both identical parts wise.
VHF N Channel MOS FET Source Follower ~ 3pf input capacitance
Or you can buy the Hi-Z Buffer board From SDR-KITS https://www.sdr-kits.net/index.php?route=web/pages&page_id=64_64 Option: Low Pass filter OR From DX-Engineering https://www.dxengineering.com/parts/dxe-z10000u-kit
Rcv + 8 to +9Vdc Tap 1 st Mixer IF BPF Gnd Buffer output Hi Z buffer Icom IC-745
Icom IC-751A 1 st IF Tap No room in here for a board
RG-174 cable to Hi Z buffer Icom IC-751A
Output RG-174 Cable Input RG-174 Cable Hi Z buffer board Rcv +8 to +9Vdc Icom IC-751A
2.8 PiTFT Capacitive Touch
Tiny Python Panadapter At this time there is no provision for a zoom function.
7 TFT Pi Foundation Display Another 2.8 Display but it s resistive touch
Cubic SDR with RTL-SDR Support on the 7 Display again no zoom function
HDSDR supports the RTL2832u but you need a Windows computer
Play Video WQ7TPanadapter Youtube Video https://youtu.be/bx3ilqbbamm
If you would like to build your own version of this panadapter the files should be available via the CCARC web site once they are posted. There is very detailed pdf manual that covers everything: Parts lists and sourcing including the Hi-Z buffer Installation of Raspberry Pi images etc. Panadapter use Saving your own defaults to the panadapter