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David Nessl

Feb 22, 2022, 3:56:09 PM2/22/22
to Radioberry
Does anyone actually use the transmitting capabilities of the Radioberry, or does everyone just transmit via a separate transceiver?  (For example, FT8 by connecting audio & CAT & maybe PTT cabIes from PC to the transceiver.)  I have a General Class license but I don't yet have an HF transceiver, so I'm trying to figure out the best way to transmit using my Radioberry.  Since no one appears to have any stock of the "official" Radioberry Pre-amp board, I have considered buying a cheap external pre-amp (like to boost the TX output of the Radioberry to a couple watts, and then feed that into a band-filtered PA (like

But from what I've read, the Radioberry is using the internal pre-amp inside the AD9866 -- if true (please let me know if I'm wrong or if I can turn it off) it appears to present two problems:
(a) It generates upwards of 60mw (theoretically 100mw), which is way too much power for the cheap pre-amps I've been looking at; and 
(b) It is reported to generate a dirty signal (not just harmonics) with nearby artifact signals.  (Apparently the signal is clean when not using the internal pre-amp.) 

So what are people doing to transmit directly from a Radioberry, or am I tilting at windmills? 


Peter Hiltz

Feb 22, 2022, 4:09:00 PM2/22/22
to David Nessl, Radioberry

I can speak to my research and experience but take my thoughts with a grain of salt.

I've transmitted wspr from my Radioberry with good results.  Note that I had to build a little TR board/hat to do that.  I've tried voice, psk31, and ft8 so far with no success, however, I have a QRP labs amp that I need to assemble and incorporate in.  I'm happy to schedule qso attempts.  Though I'm awaiting the incorporation of the keyer's fix into the pihpsdr baseline, with help I have cw working so can do that, though my cw is rough.

The preamp is on the receive side, not the transmit.  The radioberry generates up to 150 mW according to the internet and I've heard rumor of the need for a filter board.  I don't have any information about the cleanliness of the signal, but sans amp, it should be calculateable from the knowledge of the number of bits in DAC, 12 I believe.


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Monitoring 146.52 MHz & the CCARC UHF Repeater   put //WL2K R/ in the subject line

Ronald Nicholson

Feb 22, 2022, 4:34:15 PM2/22/22
to Radioberry
I've transmitted FT8 from my Radioberry into a dummy load, and it worked (e.g. the signal was picked up and decoded by my nearby HL2).

The AD9866 in the Radioberry is capable of 15 different output drive levels, over a 7 dB range.  And an attenuator can be used to reduce the output level, if needed to match the input requirements of some external amp.  It might be somewhat possible to clean up the DAC output by noise shaping the output and using adaptive pre-distortion algorithms.  The Radioberry PCB already includes is an anti-aliasing low-pass filter on the DAC output, but lower bands will likely require more low-pass filtering.  Someone with a spectrum analyzer should check.



Feb 25, 2022, 5:50:15 AM2/25/22
to Radioberry
Hi I also use the radioberry for transmitting. 
I use a set of bandpassfilters for input and output and a small 2x RD16HFF  power amplifier.



David Nessl

Mar 10, 2022, 2:44:23 PM3/10/22
to Radioberry

Thanks for everyone's replies.  I have ordered a cheap 3W amp and a 45W amp that has bandpass filters for each band (to handle harmonics).   I'm still waiting on some attenuators so I can use my TinySA spectrum/signal analyzer to see how clean the radioberry's TX signal is.   This leaves me with two questions:

(1) Most importantly, how do I share one antenna with the separate RF connections for RX and TX on the radioberry, given an external amp?  Do I need an external RF switch (that uses relays) between the radioberry and the amp (which I assume would switch based on a PTT/TX signal from one of the GPIO pins)?  Please let me know how you handled this.  Thanks.  

(2) Less important:  The radioberry's AD9866 has an internal TX amp that produces up to 150 mW so I assume it's enabled by default, but supposedly it can be disabled in software, tho I don't know if that means the firmware or in driver code on the radioberry.  I've been using piHPSDR (compiled for my Ubuntu x86_64 desktop) because piHPSDR seems to be the SDR app that has the best support for radioberry (please correct me if I'm wrong).  Question:  Are there settings in piHPSDR I'm not seeing that control the use of that internal TX amp?  

David W1DRN

Gopakumar K

Mar 11, 2022, 4:02:22 AM3/11/22
to Radioberry
I have been using radioberry  in HF for the past couple of months. I use CW, SSB,FT8 etc and working wonderfully . CQRlog installed in the  same raspberrypi  takes care of the logging requirements.  I  have MRF300 amplifier which is capable to  deliver 600W.. few links attached herewith .. My experiments with radioberry.

Thanks to Johan for the wonderful piece of  electronics ...

transmitting video below

Radioberry remote operation ... myown way  not the new one johan introduced.  I have installed it and , I have to make it working...

I can share any info you want from me..


Mar 11, 2022, 9:49:34 AM3/11/22
to David Nessl, Radioberry
Transmitting works quite well with the radioberry. I build a pcb with bandfilters using as169 rf GaAs IC switches which also switches between tx and rx using I2C.
I am not using piHPSDR but build my own software, but I think piHPSDR can also send I2C commands to switch a relay or so.

Op do 10 mrt. 2022 om 20:44 schreef David Nessl <>:
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David Nessl

Mar 27, 2022, 5:35:00 PM3/27/22
to Radioberry
So I've bought an RF switch module
and an amplifier.  Now I need to find a control line that indicates we're in TX mode and which I can use to tell my new RF switch to toggle between the RX and the TX SMA ports.  I've crawled thru the RB git repo's doco and code, but I don't see an obvious answer.  I'm hoping that I could see it on a GPIO line, but when watching the GPIO lines using piscope I don't see a GPIO line that changes when WSJT-X/FT8 goes into transmit mode (but I do see the RF signal in the panadapter display in pihpsdr).  I was hoping to be able to avoid having to solder a line onto the radioberry board as my soldering skills aren't that great.  Anyway, can anyone point me at where I get a signal that it's in TX mode?  Thanks.

-david W1DRN

Kristofer Danner

Mar 28, 2022, 10:13:29 PM3/28/22
to Radioberry
David, the I/O is detailed on the wiki, INTTR and EXTTR will both switch on TX. You should add some minor circuitry for this rather than trying to switch directly via the FPGA, this circuitry can be found in the Radioberry preamp schematic.


Joseph Teichman

Mar 31, 2022, 10:35:37 AM3/31/22
to Kristofer Danner, Radioberry
Hi, I'm in the same position as David and I got one of these H349 RF switch modules. Checking the datasheet, it shows that the max switch current is 30 microamperes. So I thought that considering how low the required current is, would it not be safe to switch directly from the FPGA? But then I realized that the problem is that the FPGA operating voltage is much lower than the switching voltage of the H349, which needs to go near its supply voltage at ~5v to go high. 

Clinton Nichols

Jul 7, 2022, 2:58:11 PM7/7/22
to Radioberry
Hi, David,

Can you share whether you had success with the solution you were attempting in this thread?  I have similar needs and questions, yet there is little information available on the Internet save for this thread.

My specific need is to get a VARA HF connection to a nearby site and if I can do that with my radioberry rather than purchase a radio then I'd like to do that.

Thank You!

David Nessl

Jul 7, 2022, 4:14:07 PM7/7/22
to Radioberry
Hi Clinton,
Sorry, I got side-tracked by life and my recent acquisition of a new toy, namely a (tr)uSDX QRP transceiver :-)  

I'm a software engineer and not an electrical engineer, so I don't have the knowledge to design circuits like some of the posters suggested.  What I did do is identify some cheap standalone modules that I'm hoping I can chain together to do what's needed, namely:  

Opto-isolator (connects from PTT and GND pins on the Radioberry 20-pin socket; output controls the RF Switch):  

I also obtained a socket for the 20-pin connector on the Radioberry, which I soldered into the Radioberry so I can use standard single-line jumper cables for PTT and GND:

RF Switch (shares an antenna by switching an antenna between the Radioberry's RX and TX SMA jacks): 

3W RF Power Amp (to get more than 150 mW output, i.e. enough to drive QRP or a larger RF Power Amp):
Based on some dB tables and a look with a TinySA, I think I will need a 20dB attenuator between the TX output of the Radioberry and this 3W PA.  

I have not hooked these up yet so I have no idea if it will all work.  My intent is to feed the output of the 3W RF Power Amp into a 45W PA that I already own; of course I'd also want to control the 45W amp from the same PTT signal coming out of the opto-isolator.  

If you decide to try this, let me know how it goes.  This project got pushed to the back burner for some other projects, but I still really want to make work because the Radioberry is still one of the best HF SDR receivers I've found.  My intent is to return to this project within the next month, and if I do get it to work I am going to post my experience in this group.  

BTW, Plan-B is to use an MFJ-1708B-SDRs (RF SENSING T/R SWITCH) that I already have, using my (tr)uSDX as the transmitter and the Radioberry as only a receiver.  

-david  (W1DRN)
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