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Re: RA8875 display problems with T4.x - a visual study
¿ªÔÆÌåÓýOk so it¡¯s not really a V11 radio. ? Did you measure sensitivity the same way I did?? The trouble with this measurement is that we need a standard to compare against. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Alain via groups.io
Sent: Monday, April 7, 2025 10:46 AM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] RA8875 display problems with T4.x - a visual study ? I just measured a sensitivity of -134dbm on my V11 version,but changed PCB routing, added a motherboard to minimize wiring, added a lot of regulators and decoupling capacitors, for having this result. |
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Re: RA8875 display problems with T4.x - a visual study
¿ªÔÆÌåÓýI said it¡¯s BELOW -100 db.? After that I start measuring the noise from the fluorescent lights in the room and my wife won¡¯t let me turn them off (her glass lab is in there too).? I do have a combo anechoic/ Faraday box in corner in my lab but it¡¯s in the process of getting moved to a different corner due to new flooring and paint. ? I¡¯ll get some absolute numbers once I get some of these human things settled. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Greg KF5N via groups.io
Sent: Monday, April 7, 2025 9:15 AM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] RA8875 display problems with T4.x - a visual study ? So I think what you are saying is a standard receiver sensitivity measurement which the ARRL calls "MDS" (minimum discernible signal). Receiver sensitivity is specified in dBm, which is decibels relative to 1 milliwatt (0 dBm). ? But even if I'm not confused on that, I'm still confused with the numbers, especially 100 dB for V12, which is presumably (what I think you mean) a sensitivity of -100dBm. Which is not very good at all! ? -- 73 Greg KF5N |
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Re: RA8875 display problems with T4.x - a visual study
Ken: If you're like me, you order "pairs" of mpu's "just in case"...it's saved my bacon more than once. Anyway, I'm not sure it's worth $10. If I use just the 4.1, I tie up about $65 for backups. If I use both the 4.0 and 4.1, I'd tie up $111 ($65 + $46). It would be interesting to see if there's a performance improvement, however. The other alternative that sounds interesting is to use an RP with its HDMI video capability for the display. It's plenty fast enough, but I know nothing about programming them, the IDE, or the library support. Jack, W8TEE
On Monday, April 7, 2025 at 08:39:11 AM EDT, ken WA2MZE <wa2mze@...> wrote:
Circuit and sw details on splitting the functions over two processors? Maybe one of the mcu's could be a T4.0 to save some bucks? -- Jack, W8TEE |
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Re: RA8875 display problems with T4.x - a visual study
¿ªÔÆÌåÓýFirst off, you need to have a good calibrated signal generator¡ calibrated in db (or mv so that you can convert to db) that is either variable output or you have a good/accurate variable attenuator.? I have both and I test them against each other because there is a very slight variation of about 0.5 db between them. ? I have an old Agilent N5182 and it will output a signal down to -110 db (and I can use a variable attenuator that).? ! connect the signal generator via the attenuator to the radio RF input.? Turn the radio on, set the radio and signal generator to a frequency (lets say 10.0000000 MHZ for kicks)¡ the signal generator acts like a dummy load (has adjustable impedance to match output power setting).? I start at about -150 db on CW, turn the radio volume way up in SSB (important¡ specified filter), and then start lowering the attenuation until I FIRST notice a signal.? Now you can also so this with an RMS volt meter on the speaker leads but I find I don¡¯t need to do that.? Find the point where I initially hear the signal generator and subtract 1 db.? that is the sensitivity; and the input in mv for (S+N)/N that gives 10 db. ? It's a bit black magic but as long as you are consistent (and have a reference that someone else did to calibrate your readings to) its OK.? I have several radios on Sherwoods list to use as references. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Greg KF5N via groups.io
Sent: Saturday, April 5, 2025 6:04 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] RA8875 display problems with T4.x - a visual study ? What I'm looking for is the measuring procedure including the instruments you used to get the 100 dB and 78 dB numbers. ? -- 73 Greg KF5N |
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Re: More testing on PA
¿ªÔÆÌåÓýYeah, that¡¯s what mine looks like too. ??Glad you found the issue.? ?I¡¯ve sold over 1,000 of those PA semi-kits now and I¡¯ve only had three people have issues since I started selling them.? One was a power lead reversal (YIKES)¡ Its pretty simple¡ not much to go wrong. ? One thing on my to-do list is to put together a list of test points with voltages and wave forms for all of the T41 boards¡ and my/ mine and Olivers boards and kits.? So many things to do and never enough time! ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Tim via groups.io
Sent: Sunday, April 6, 2025 3:14 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] More testing on PA ? I rewound t1,2 and 3. Tested between each rewind, tuned out T3 was culprit, easiest to wind! Not sure what it was ,I may have had a solder bridge across C25 which on revised board is right next to center tap pad. I would suggest moving that if you revise board. Seems very easy to bridge when soldering center tap windings. 100pF across primary, 7 turns on L2 (enamel wire). I may play a bit with cap across primary but it looks so much nicer now I may just leave it alone! Tim? |
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Re: More testing on PA
I rewound t1,2 and 3. Tested between each rewind, tuned out T3 was culprit, easiest to wind! Not sure what it was ,I may have had a solder bridge across C25 which on revised board is right next to center tap pad. I would suggest moving that if you revise board. Seems very easy to bridge when soldering center tap windings.
100pF across primary, 7 turns on L2 (enamel wire).
I may play a bit with cap across primary but it looks so much nicer now I may just leave it alone!
Tim?
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Boards and Kits
¿ªÔÆÌåÓýI¡¯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 ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? |
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Re: Updated book; not available on amazon uk
I don't know how long it takes for US changes to ripple through the system. I would write Amazon.UK and try to get an answer. Jack, W8TEE
On Sunday, April 6, 2025 at 12:24:14 PM EDT, Gareth Evans via groups.io <headstone255@...> wrote:
As per title -- Jack, W8TEE |
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Re: RA8875 display problems with T4.x - a visual study
¿ªÔÆÌåÓýWell there is no real absolute way its done as you probably know, you first need to determine the noise floor (for the mode) and that is usually the point at which the (S+N)/N = 3db (and of course, its bandwidth sensitive and frequency dependent).? If all you are interested in is the absolute noise floor at a frequency you can do this with a dummy load. ??Then the radio sensitivity is the point 10 db = (S+N)/N.? This is the point at which the signal is 10 db stronger than the receiver noise (Definition for voice comms and there are a couple of ways to do this¡ but most commonly with a signal generator, a good adjustable attenuator).? If you do this in CW with a narrow filter it¡¯s taken to be 3 db.? [I could write a book here but wont] ? For the two V11 and V12 radio display impact, the difference between the display handling stuff is to determine the noise floors for each¡ difference them. ?Its not completely fair but it is representative. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Greg KF5N via groups.io
Sent: Saturday, April 5, 2025 4:25 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] RA8875 display problems with T4.x - a visual study ? Hi Bill, 100 dB relative to what?? How did you measure that? ? -- 73 Greg KF5N |
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Re: Update now available
That was changed...don't know why it wasn't updated. Jack, W8TEE
On Saturday, April 5, 2025 at 03:42:45 PM EDT, K9HZ <bill@...> wrote:
?¡°The latest (V12) PCBs are available for less than $5 each on the web site (/g/SoftwareControlledHamRadio). If you wish, pre-fabricated PCBs with all SMD devices already on the board are available as a semi-kit from 4SQRP (see http://www.4sqrp.com/index.php for details).¡± ? Yikes this is outdated¡ ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Oliver KI3P via groups.io
Sent: Saturday, April 5, 2025 2:31 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] Update now available ? I think this is the correct link:
-- Jack, W8TEE |
K9HZ
jjpurdum