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I am running the latest SW ver66.9, downloaded today. I am use the analog SWR circuits. I have good FWD-V (~1.5V) and REV-V (0.005) into the dummy load and REV-V varies as load resistance varies. In the Cal screen, Power and SWR measure "inf" and "nan". Nothing changes them. And, where should the pots, RV19 and RV27, be set? Thanks for the help. dave, n3ds

I am getting about 50mv noise out of the 20W amp in SSB with PTT engaged; no mic plugged in. I'm running version 66.9 and am all calibrated. Additionally, when PTT is engaged there is a burst of signal (about500mv) that exponentially decays in 5ms. The audio sounds pretty rough on my other radio, but wonder if that is because of such close proximity. Amplitude is affected by MIC GAIN. Any thoughts? dave, n3ds

Love this new format! Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com email: bill@...

Hello, I discovered this project last Fall and this reflector even more recently. I have been reading the discussions about "Display Noise' and"SPI issues" with much interest and since my experience is a bit different I will share it here. I have built a V12 radio with RF, Main, and Front panel boards in an AI6YM chassis, using STDVer050.2 software. I originally built the radio with a TFTM070A3-5 v4.0 (7") display and immediately noticed significant amounts of noise not normally heard from a radio with the antenna disconnected. This noise was below the level of the noise coming from my antenna on bands up through 15M, but above that the radio's internal noise was higher than antenna noise. I made a simple probe from a piece of coax by removing 1 " of the shield from the end, connected the other end to my spectrum analyzer, and probed around the inside of my T41. I discovered what I believe to be a smps in the upper right corner of the rear of the display running at about 1.15 MHz. This smps exists in both the 5" and 7" displays. The 6th harmonic of this can be heard at the bottom of 40M and the 12th harmonic at the bottom of 20M; neither can be heard with my antenna connected but are very noticeable with the antenna disconnected. I discovered very high levels of EMI radiated from the middle area of the circuit card on the back of the display. The spectrum of this EMI starts in the HF band, peaks around 160 MHz and has very significant strength in the 6M and 2M bands. I then noted that the layout of the boards in my chassis places the receive input circuitry about 2" from both the smps and the display EMI source. Not good! I then clamped my coax to the chassis such that the 1" "probe" was right next to the receive RF input circuitry. I then made a simple shield/cover for the 7" display. In doing so, I discovered a few issues with the displays. First, the pads around the four mounting holes are not connected to the circuit ground, nor are they even connected to each other. On the 7" display, the four oblong, exposed, pads across the top are connected to the circuit ground, but the four across the bottom of the board are not, nor are they connected to each other. When I then measured the noise from the probe with and without the shield in place on the 7" display there was some improvement, most noticeably on the smps noise, but the noise on the upper HF bands was still higher than the noise from the antenna. I then looked at the 5" display. All four of its exposed, oblong, pads are connected to ground. I soldered small clips (from a Harmon EMI kit) to each of those four pads and made a shield to fit in those clips (see attached picture). I had to run a short wire from each clip to the closest mounting post to tie the shield to the chassis. This provided a very significant reduction in the level of noise present at the receive input circuitry. To quantify the improvement, I measured the radio's sensitivity on each band and converted that to a receive noise figure. That can be compared to the level of noise that I measure from my antenna. This data is shown and graphed in the attached Excel file. The T41 receiver is very quiet now up through 10M. 6M is much improved, but further improvement is desired. Perhaps the cable..., perhaps moving the RF board away.... 73, John W2TX

I have Dr. Bills PA and a similar (same finals) from 60dbm shop. Both on 13V same 0dB sweep from SA. I attached the 60dBm Schematic for reference. Here is Dr. Bills with 0dB in His with -10dB in, 60dbm shop amp 0dBin

The subject of problems with the SPI interface between the T4.x & RA8875 displays comes up quite often on the Teensy forum. I would like to point out that the SPI interface is not anything that PJRC has much control over (it's baked into the processor that NXP created). I'm not defending PJRC, just suggesting that any angst should almost certainly be directed to NXP rather than PJRC. I personally am using an RA8875 display from buydisplay.com in my TeensyMIDIPolySynth (TMPS) project, & my experience with incorporating this display included some significant challenges. I initially wire-wrapped a prototype of my TMPS & everything worked like a champ. When I took the design to PCB, I transitioned through multiple (very expensive, with the PCB being 5.5" x 8.5" !!) versions of the PCB (with additional decoupling caps, with additional ground plane, with no ground plane, with two ground planes sandwiching everything else & a very large number of thru-vias stitching them closely together, with shorter SPI signal traces, with orthagonal SPI signal traces, etc.). I was very frustrated until I found a few posts on the Teensy forum suggesting placing small value resistors (50-100ohm) inline with some of the SPI signals. So, I cut traces on one of my non-working PCBs & patched in some resistors. Doing so actually resolved my specific display problems. I determined (thru experimentation & by observing the signals on my o-scope) that 100ohm resistors resulted in the cleanest SPI signals for my particular setup, so that's what the final PCB version for my TMPS successfully includes. I am using the SPI interface connected to the RA8875 display at native speeds, with no software slowdown. I have not had any RA8875 display problems of any kind since. To me, this is very counter-intuitive: how could a very sloppy wire-wrapped board work just fine, but a very clean looking PCB not allow the display to work ?? Signal ringing & signal cross-talk were the major contributors to my display failures. I know that there's some controversy with this "solution" of using inline small value resistors, but, for reference, here's a very recent Teensy forum post that visually shows the difference in the quality of the SPI signals before & after the use of inline small value resistors: https://forum.pjrc.com/index.php?threads/ra8875-teensy-4-1-again.76621/post-356579 For comparison, I'd be interested in testing one of my non-working TMPS PCBs with the K9HZ buffer chip, if that's still an available option. Mark J Culross KD5RXT P.S. As a side note (since the subject of using serial interconnects between processors has also recently been discussed), my TMPS makes use of two Teensy boards: T4.1 runs the display & manages traditional 5-pin DIN serial MIDI, USBmidi, & USBhostMIDI, while a T4.0 manages all of the audio thru a Teensy Audio Adapter. The two Teensy boards communicate over a shared 500Kbps serial port (settings flow T4.1-to-T4.0, audio/performance status flows T4.0-to-T4.1, & debug info flows both ways). The device is a 3-voice, multi-waveform, multi-modulator (selectable FM & PM), 12-poly synth, with filtering & envelope control of all generators, where all of the controls are digitally displayed as buttons & sliders on the RA8875 display, switching between & among multiple menu screens, & everything can be adjusted in real time with no degradation of the resulting sound while it is being generated, & no induced delays in the MIDI response. I am continually impressed with what a beast the T4.x actually is. MJC

I’m back for a while and working on kits again. I put a very high priority on the new Display Driver board that fixes the T41 display freeze issue and allows a nice long cable to the display. I offer a 3.3V ONLY kit and a 3.3V and 5V kit (until I run out of 3.3V kits… then I will only stock the combo 3.3V and 5V kit). I’m still writing the assembly manual for the display kits but it should be done by this afternoon. I will order the last few parts for them today… I should have them by Tuesday and will begin shipping them then. Also new to the list is the 20W Dummy Load/ 40 db attenuator tap for the calibration steps. I’ve attached the full list so you can look it over if you need something. Those boards and Kits with $0.00 are not in stock. Remember, don’t send me money, I’ll invoice you… and make SURE you include your address. All prices below are without shipping, taxes, and Paypal fee. I will be at FDIM Thursday night… and have a booth at Hamvention (Booth 4111 in Building 4) where we will have a special guest… Al Peter to show off the T41 and answer any questions. I will be selling boards and kits both places and you won’t have to pay shipping on them if you carry them away. Respond via my private email bill@... as to not clog the space here with our transactions. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

Hello everyone, I have an assembled, tested and calibrated a T41 from 4SQRP that I built as a comparison to my T41EP that I built from scratch (no kit). I wanted to see if my no kit T41 performed as well as the kit from 4SQRP (which it did!). My T41 for sale has the "built like a tank" 20 watt amplifier from K9HZ. The last firmware that I installed is T41EEE by KF6VB. Of course newer versions of firmware/software have been released which you could upgrade the T41 to. The T41 is excess to my needs and I am hoping that someone who wanted this design but missed the one-time production run from 4SQRP may be interested in buying this completed radio. Please contact me directly if interested via PM or email me to the email listed on QRZ.com. Thanks and 73, Frank K1FFJ

All: Just heard from Amazon and the updated version is now being advertised: Jack, W8TEE -- Jack, W8TEE

After totally scrubbing and rebuilding the IDE and libraries, I can compile and run everything again. However Ver66.4 and 66.9 only run at 600MHz if TCXO is defined. They both freeze if compiled with 528MHz. The Receive I&Q Cal worked quite well, except the button assignments don't agree with the directions. Compiled with: Faster with LTO, 600 MHz, Dual Serial SDTVer66.4 Memory Usage on Teensy 4.1: FLASH: code:308228, data:132408, headers:8892 free for files:7676936 RAM1: variables:194528, code:284488, padding:10424 free for local variables:34848 RAM2: variables:483744 free for malloc/new:40544 SDTVer66.9 Memory Usage on Teensy 4.1: FLASH: code:312196, data:132408, headers:9020 free for files:7672840 RAM1: variables:194784, code:288584, padding:6328 free for local variables:34592 RAM2: variables:483744 free for malloc/new:40544 -- 73 to you! 73 Bob W3RDL Virus-free.www.avast.com