<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body><div>I want one of the ant analyzer kits. If you come up with the kit, I'll provide addy, K5KBV, ED</div><div><br></div><div><br></div><div><br></div><div id="composer_signature"><div style="font-size:85%;color:#575757" dir="auto">Sent from my Samsung Galaxy smartphone.</div></div><div><br></div><div style="font-size:100%;color:#000000"><!-- originalMessage --><div>-------- Original message --------</div><div>From: hfsig-request@lists.tapr.org </div><div>Date: 3/24/19 11:00 AM (GMT-06:00) </div><div>To: hfsig@lists.tapr.org </div><div>Subject: hfsig Digest, Vol 40, Issue 3 </div><div><br></div></div>Send hfsig mailing list submissions to<br> hfsig@lists.tapr.org<br><br>To subscribe or unsubscribe via the World Wide Web, visit<br> http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org<br>or, via email, send a message with subject or body 'help' to<br> hfsig-request@lists.tapr.org<br><br>You can reach the person managing the list at<br> hfsig-owner@lists.tapr.org<br><br>When replying, please edit your Subject line so it is more specific<br>than "Re: Contents of hfsig digest..."<br><br><br>Today's Topics:<br><br> 1. Re: 20m WSPR shield for Raspberry Pi (John, W9DDD)<br><br><br>----------------------------------------------------------------------<br><br>Message: 1<br>Date: Sat, 23 Mar 2019 14:29:53 -0500<br>From: "John, W9DDD" <w9ddd@tapr.org><br>To: hfsig@lists.tapr.org<br>Subject: Re: [hfsig] 20m WSPR shield for Raspberry Pi<br>Message-ID: <dcfdb486-6eca-e59e-d85a-6dead1b8e325@tapr.org><br>Content-Type: text/plain; charset=windows-1252; format=flowed<br><br>I want one of those antenna analyzer kits.<br><br>John, W9DDD<br><br>On 3/23/2019 2:23 PM, Bruce Raymond wrote:<br>> Hi Keith,<br>> <br>> You've obviously picked the ultimate in terms of getting rid of hum - <br>> using a battery (I didn't read the original post carefully enough). <br>> You've hit on all of the fixes I can think of.<br>> <br>> 120 Hz implies full wave rectification of 60 Hz. Unfortunately, 60 Hz is <br>> all around us, so that doesn't help much. Another relatively obvious <br>> thing is to question the test equipment, although that's a real long <br>> shot. I don't see how you get mixing products from a spec an or a scope. <br>> I suppose an easy test for that would be to look at a known clean <br>> signal, like from a signal generator, and look for mixing products. This <br>> whole direction seems like a real long shot.<br>> <br>> You've got more power coming out of the transmitter than we would <br>> expect. That probably means that the MOSFET bias voltage is fairly high <br>> relative to its threshold voltage, so the bias current and gain are <br>> high. It's possible that you're generating much stronger harmonic <br>> components from the MOSFET than you otherwise would, raising the <br>> harmonic content of the output.<br>> <br>> OTOH, 30 dB down means ~3% of the amplitude relative to the carrier. I <br>> doubt this would have any impact on a WSPR receiver's ability to decode <br>> the signal.<br>> <br>> <br>> I originally put together a 30m WSPR transmitter kit. I sent ~45 of the <br>> kits to John/TAPR. These are sold out. I redesigned the unit to use <br>> surface mount parts and had 200 units assembled and tested, and <br>> delivered to John. There should be plenty of these units available.<br>> <br>> 73 Bruce<br>> <br>> P.S. I'm working on an idea for an automatic antenna analyzer kit for <br>> HF. It will scan a range of frequencies and find the resonant point and <br>> VSWR at resonance (actually min VSWR, not necessarily resonance), and <br>> 2:1 VSWR bandwidth. This will be a kit with no surface mount parts and <br>> no case, but will have mounting holes so you can mount it in your choice <br>> of cases. It will probably sell in the ~70 range. Does this sound like a <br>> worthwhile project?<br>> <br>> <br>> <br>> Keith Wilson wrote on 3/23/2019 1:02 PM:<br>>> Hi Bruce, and thanks for the generous response!<br>>><br>>> My power measurement was made with a good 50 ohm load so maybe I have <br>>> a nice hot MOSFET!<br>>><br>>> As mentioned in my previous email, the testing was with a USB power <br>>> bank battery, and I still have the 120 Hz apparent mixing products.? I <br>>> tried a separate antenna (my SOTA antenna) so I was not attached to <br>>> the station ground.? (My station ground is bonded to the household <br>>> power ground) So I shouldn't have any way for 60 Hz power to get into <br>>> the Pi or USB battery.? Still puzzled by the presence of these <br>>> apparent mixing products.? Because they are down 30 dB, I probably <br>>> won't get double decodes by receiving stations.<br>>><br>>> Last question, TAPR is out of the 30 m boards.? Are they still available?<br>>><br>>> 73,<br>>> Keith - KE4TH<br>>><br>>> On Fri, Mar 22, 2019 at 9:14 PM Bruce Raymond <bruce@raymondtech.net <br>>> <mailto:bruce@raymondtech.net>> wrote:<br>>><br>>> Hi Keith,<br>>><br>>> I have to agree with Bryan (well, I suppose I don't *really* have<br>>> to agree with him, I just want to :-). The 20m transmitter is<br>>> Zoltan's design, but very similar to my 30m transmitter. The final<br>>> is an MMBF170 powered by 5 volts.<br>>><br>>> 1. The power output is approximated by the formula?? P = V^2/2*RL.<br>>> The power supply is roughly 5 volts and assuming a 50 ohm load<br>>> (RL), P = 5^2/(2 * 50) = 0.25 watts.<br>>><br>>> It's reasonable to expect some losses and the safest way to list<br>>> the output power is to say you'll get at least 200 mW. Also, if<br>>> the supply voltage is higher than 5 volts then you'll get more<br>>> power. It's unlikely that it would be *that* much higher; it would<br>>> take 6? volts to give 360 mW. Another possibility is that your<br>>> antenna impedance is less than 50 ohms. If your antenna impedance<br>>> is, say, 35 ohms, then P = 5^2/(2 * 35) = 360 mW. The last (and<br>>> most probable) thought is that the MOSFET in your transmitter is<br>>> hotter than typical and gets driven harder, producing more output.<br>>> I've played with this on the 30m transmitter and have gotten power<br>>> outputs in this range by biasing the MOSFET on more. The threshold<br>>> voltage for a MMBF170 MOSFET is between 0.8 and 3.0 volts with 2.1<br>>> volts being a typical value. The 20m transmitter has a voltage<br>>> divider putting 2.3 volts on the gate. If your MOSFET is fairly<br>>> hot then it would be biased on more and likely put out more<br>>> output. The end result is *yes* the output is real. => Watch for<br>>> the MOSFET getting hot. If it does, you might want to add a heat<br>>> sink or change the gate bias resistor (R2) from 1.2K to something<br>>> larger, say 1.5K. <=<br>>><br>>> 2. Power supplies - in the words of Socrates, suffering an<br>>> learning are two names for the same experience (I don't know that<br>>> Socrates actually said that, but I like to say he did). I have<br>>> learned through hard experience that inadequate power supplies<br>>> cause a whole bunch of problems, and they're usually very<br>>> difficult to troubleshoot because the problems are either<br>>> intermittent or just not something I'd normally suspect of a power<br>>> supply. The power supplies normally used for the Raspberry Pi are<br>>> usually marginally adequate. I'm very impressed with the job the<br>>> designers of the Pi did, but they cheaped out on the power supply<br>>> filter on the board (electrolytic capacitor).<br>>><br>>> Now we compound the problem with trying to run a transmitter off<br>>> of the same power supply in addition to running the Pi. This<br>>> doesn't help things. In the beginning I bought a bunch of cheap<br>>> 5V/2A power supplies from China that worked with my Pi/30m<br>>> transmitters. I had a bunch of weird problems, such as the<br>>> software getting corrupted during normal operation. At first I<br>>> thought the problem was cheap SD cards or some problem with the<br>>> operating system/software. I now believe the problem was power<br>>> supply glitches causing the Pi to get confused and do bad stuff. I<br>>> switched to bigger power supplies and my problems disappeared.<br>>><br>>> My recommendation is to get a 5V/3A power supply and make your<br>>> measurements again. 120 Hz sidebands sounds like AC bleeding<br>>> through the power supply, even if it seems that the power coming<br>>> off the supply is clean. It could also be some sort of interaction<br>>> between your antenna ground and your power supply ground. You<br>>> might try a different power supply and/or an isolation transformer<br>>> for a test. This might be similar to hum problems direct<br>>> conversion receivers have that are associated with grounding.<br>>><br>>> 73 Bruce Raymond/ND8I<br>>><br>>><br>>><br>>> Bryan Corkran wrote on 3/22/2019 4:22 PM:<br>>>> I had a lot of trouble with power, in the end I bought the<br>>>> ?official? 2.5 amp adapter and had no trouble after that.<br>>>> Keith is right the shield is designed for the V1 board hence the<br>>>> little slot in the middle for the display port. I had problems<br>>>> with the shield fouling on the heat sink I?d added on a 3b board<br>>>> so I used a GPIO extender to raise it a small amount.<br>>>><br>>>> Bryan, VK3KEZ<br>>>><br>>>> On 23 Mar 2019, at 5:36 am, Keith Wilson<br>>>> <keith.wilson.pcs@gmail.com <mailto:keith.wilson.pcs@gmail.com>><br>>>> wrote:<br>>>><br>>>>> I have the 20m WSPR shield working on a new Raspberry Pi 3 B+. <br>>>>> I see apparent mixing products in the output, 120 Hz away from<br>>>>> fundamental, when using a USB power bank to power the Pi.? Since<br>>>>> these are not coming from a switching power supply, where are<br>>>>> they coming from?? These products start at about 30 dB below the<br>>>>> fundamental.<br>>>>><br>>>>> Also, with a scope I measure the voltage output at 12V peak to<br>>>>> peak into quality 50 ohm dummy load.? This is 0.36W, higher than<br>>>>> the 20dBm (0.10W) specified.? Is this too good to be true?<br>>>>><br>>>>> Note the shield was not designed for the Raspberry Pi 3 B+ so it<br>>>>> can't be fully inserted on the 40 pin GPIO plug, but seems<br>>>>> stable enough partially inserted.? Getting WSPR reports from<br>>>>> across the USA and occasional overseas reports too.<br>>>>><br>>>>> Keith - KE4TH<br>>>>><br>>>>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon><br>>>>> Virus-free. www.avast.com<br>>>>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link><br>>>>><br>>>>><br>>>>> _______________________________________________<br>>>>> hfsig mailing list<br>>>>> hfsig@lists.tapr.org <mailto:hfsig@lists.tapr.org><br>>>>> http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org<br>>>><br>>>><br>>>> _______________________________________________<br>>>> hfsig mailing list<br>>>> hfsig@lists.tapr.org <mailto:hfsig@lists.tapr.org><br>>>> http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org<br>>><br>>> _______________________________________________<br>>> hfsig mailing list<br>>> hfsig@lists.tapr.org <mailto:hfsig@lists.tapr.org><br>>> http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org<br>>><br>> <br>> <br>> <br>> _______________________________________________<br>> hfsig mailing list<br>> hfsig@lists.tapr.org<br>> http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org<br>> <br><br><br><br>------------------------------<br><br>Subject: Digest Footer<br><br>_______________________________________________<br>hfsig mailing list<br>hfsig@lists.tapr.org<br>http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org<br><br><br>------------------------------<br><br>End of hfsig Digest, Vol 40, Issue 3<br>************************************<br></body></html>