[hfsig] Antenna analyzer kit

Sun Mar 24 13:07:15 EDT 2019

Reference mention of analyzer project lit, I'd be interested in obtaining  one.73,Ed K5KBVSent from my Samsung Galaxy smartphone.
-------- Original message --------From: hfsig-request at lists.tapr.org Date: 3/24/19  11:31 AM  (GMT-06:00) To: hfsig at lists.tapr.org Subject: hfsig Digest, Vol 40, Issue 4 Send hfsig mailing list submissions to	hfsig at lists.tapr.orgTo subscribe or unsubscribe via the World Wide Web, visit	http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.orgor, via email, send a message with subject or body 'help' to	hfsig-request at lists.tapr.orgYou can reach the person managing the list at	hfsig-owner at lists.tapr.orgWhen replying, please edit your Subject line so it is more specificthan "Re: Contents of hfsig digest..."Today's Topics:   1. Re: hfsig Digest, Vol 40, Issue 3 (supertech0491)----------------------------------------------------------------------Message: 1Date: Sun, 24 Mar 2019 11:29:56 -0500From: supertech0491 <supertech0491 at yahoo.com>To: hfsig at lists.tapr.orgSubject: Re: [hfsig] hfsig Digest, Vol 40, Issue 3Message-ID:	<mailman.36.1553445075.809.hfsig_lists.tapr.org at lists.tapr.org>Content-Type: text/plain; charset="utf-8"I want one of the ant analyzer kits. If you come up with the kit, I'll provide addy, K5KBV, EDSent from my Samsung Galaxy smartphone.-------- Original message --------From: hfsig-request at lists.tapr.org Date: 3/24/19  11:00 AM  (GMT-06:00) To: hfsig at lists.tapr.org Subject: hfsig Digest, Vol 40, Issue 3 Send hfsig mailing list submissions to	hfsig at lists.tapr.orgTo subscribe or unsubscribe via the World Wide Web, visit	http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.orgor, via email, send a message with subject or body 'help' to	hfsig-request at lists.tapr.orgYou can reach the person managing the list at	hfsig-owner at lists.tapr.orgWhen replying, please edit your Subject line so it is more specificthan "Re: Contents of hfsig digest..."Today's Topics:?? 1. Re: 20m WSPR shield for Raspberry Pi (John, W9DDD)----------------------------------------------------------------------Message: 1Date: Sat, 23 Mar 2019 14:29:53 -0500From: "John, W9DDD" <w9ddd at tapr.org>To: hfsig at lists.tapr.orgSubject: Re: [hfsig] 20m WSPR shield for Raspberry PiMessage-ID: <dcfdb486-6eca-e59e-d85a-6dead1b8e325 at tapr.org>Content-Type: text/plain; charset=windows-1252; format=flowedI want one of those antenna analyzer kits.John, W9DDDOn 3/23/2019 2:23 PM, Bruce Raymond wrote:> Hi Keith,> > You've obviously picked the ultimate in terms of getting rid of hum - > using a battery (I didn't read the original post carefully enough). > You've hit on all of the fixes I can think of.> > 120 Hz implies full wave rectification of 60 Hz. Unfortunately, 60 Hz is > all around us, so that doesn't help much. Another relatively obvious > thing is to question the test equipment, although that's a real long > shot. I don't see how you get mixing products from a spec an or a scope. > I suppose an easy test for that would be to look at a known clean > signal, like from a signal generator, and look for mixing products. This > whole direction seems like a real long shot.> > You've got more power coming out of the transmitter than we would > expect. That probably means that the MOSFET bias voltage is fairly high > relative to its threshold voltage, so the bias current and gain are > high. It's possible that you're generating much stronger harmonic > components from the MOSFET than you otherwise would, raising the > harmonic content of the output.> > OTOH, 30 dB down means ~3% of the amplitude relative to the carrier. I > doubt this would have any impact on a WSPR receiver's ability to decode > the signal.> > > I originally put together a 30m WSPR transmitter kit. I sent ~45 of the > kits to John/TAPR. These are sold out. I redesigned the unit to use > surface mount parts and had 200 units assembled and tested, and > delivered to John. There should be plenty of these units available.> > 73 Bruce> > P.S. I'm working on an idea for an automatic antenna analyzer kit for > HF. It will scan a range of frequencies and find the resonant point and > VSWR at resonance (actually min VSWR, not necessarily resonance), and > 2:1 VSWR bandwidth. This will be a kit with no surface mount parts and > no case, but will have mounting holes so you can mount it in your choice > of cases. It will probably sell in the ~70 range. Does this sound like a > worthwhile project?> > > > Keith Wilson wrote on 3/23/2019 1:02 PM:>> Hi Bruce, and thanks for the generous response!>>>> My power measurement was made with a good 50 ohm load so maybe I have >> a nice hot MOSFET!>>>> As mentioned in my previous email, the testing was with a USB power >> bank battery, and I still have the 120 Hz apparent mixing products.? I >> tried a separate antenna (my SOTA antenna) so I was not attached to >> the station ground.? (My station ground is bonded to the household >> power ground) So I shouldn't have any way for 60 Hz power to get into >> the Pi or USB battery.? Still puzzled by the presence of these >> apparent mixing products.? Because they are down 30 dB, I probably >> won't get double decodes by receiving stations.>>>> Last question, TAPR is out of the 30 m boards.? Are they still available?>>>> 73,>> Keith - KE4TH>>>> On Fri, Mar 22, 2019 at 9:14 PM Bruce Raymond <bruce at raymondtech.net >> <mailto:bruce at raymondtech.net>> wrote:>>>>???? Hi Keith,>>>>???? I have to agree with Bryan (well, I suppose I don't *really* have>>???? to agree with him, I just want to :-). The 20m transmitter is>>???? Zoltan's design, but very similar to my 30m transmitter. The final>>???? is an MMBF170 powered by 5 volts.>>>>???? 1. The power output is approximated by the formula?? P = V^2/2*RL.>>???? The power supply is roughly 5 volts and assuming a 50 ohm load>>???? (RL), P = 5^2/(2 * 50) = 0.25 watts.>>>>???? It's reasonable to expect some losses and the safest way to list>>???? the output power is to say you'll get at least 200 mW. Also, if>>???? the supply voltage is higher than 5 volts then you'll get more>>???? power. It's unlikely that it would be *that* much higher; it would>>???? take 6? volts to give 360 mW. Another possibility is that your>>???? antenna impedance is less than 50 ohms. If your antenna impedance>>???? is, say, 35 ohms, then P = 5^2/(2 * 35) = 360 mW. The last (and>>???? most probable) thought is that the MOSFET in your transmitter is>>???? hotter than typical and gets driven harder, producing more output.>>???? I've played with this on the 30m transmitter and have gotten power>>???? outputs in this range by biasing the MOSFET on more. The threshold>>???? voltage for a MMBF170 MOSFET is between 0.8 and 3.0 volts with 2.1>>???? volts being a typical value. The 20m transmitter has a voltage>>???? divider putting 2.3 volts on the gate. If your MOSFET is fairly>>???? hot then it would be biased on more and likely put out more>>???? output. The end result is *yes* the output is real. => Watch for>>???? the MOSFET getting hot. If it does, you might want to add a heat>>???? sink or change the gate bias resistor (R2) from 1.2K to something>>???? larger, say 1.5K. <=>>>>???? 2. Power supplies - in the words of Socrates, suffering an>>???? learning are two names for the same experience (I don't know that>>???? Socrates actually said that, but I like to say he did). I have>>???? learned through hard experience that inadequate power supplies>>???? cause a whole bunch of problems, and they're usually very>>???? difficult to troubleshoot because the problems are either>>???? intermittent or just not something I'd normally suspect of a power>>???? supply. The power supplies normally used for the Raspberry Pi are>>???? usually marginally adequate. I'm very impressed with the job the>>???? designers of the Pi did, but they cheaped out on the power supply>>???? filter on the board (electrolytic capacitor).>>>>???? Now we compound the problem with trying to run a transmitter off>>???? of the same power supply in addition to running the Pi. This>>???? doesn't help things. In the beginning I bought a bunch of cheap>>???? 5V/2A power supplies from China that worked with my Pi/30m>>???? transmitters. I had a bunch of weird problems, such as the>>???? software getting corrupted during normal operation. At first I>>???? thought the problem was cheap SD cards or some problem with the>>???? operating system/software. I now believe the problem was power>>???? supply glitches causing the Pi to get confused and do bad stuff. I>>???? switched to bigger power supplies and my problems disappeared.>>>>???? My recommendation is to get a 5V/3A power supply and make your>>???? measurements again. 120 Hz sidebands sounds like AC bleeding>>???? through the power supply, even if it seems that the power coming>>???? off the supply is clean. It could also be some sort of interaction>>???? between your antenna ground and your power supply ground. You>>???? might try a different power supply and/or an isolation transformer>>???? for a test. This might be similar to hum problems direct>>???? conversion receivers have that are associated with grounding.>>>>???? 73 Bruce Raymond/ND8I>>>>>>>>???? Bryan Corkran wrote on 3/22/2019 4:22 PM:>>>???? I had a lot of trouble with power, in the end I bought the>>>???? ?official? 2.5 amp adapter and had no trouble after that.>>>???? Keith is right the shield is designed for the V1 board hence the>>>???? little slot in the middle for the display port. I had problems>>>???? with the shield fouling on the heat sink I?d added on a 3b board>>>???? so I used a GPIO extender to raise it a small amount.>>>>>>???? Bryan, VK3KEZ>>>>>>???? On 23 Mar 2019, at 5:36 am, Keith Wilson>>>???? <keith.wilson.pcs at gmail.com <mailto:keith.wilson.pcs at gmail.com>>>>>???? wrote:>>>>>>>???? I have the 20m WSPR shield working on a new Raspberry Pi 3 B+. >>>>???? I see apparent mixing products in the output, 120 Hz away from>>>>???? fundamental, when using a USB power bank to power the Pi.? Since>>>>???? these are not coming from a switching power supply, where are>>>>???? they coming from?? These products start at about 30 dB below the>>>>???? fundamental.>>>>>>>>???? Also, with a scope I measure the voltage output at 12V peak to>>>>???? peak into quality 50 ohm dummy load.? This is 0.36W, higher than>>>>???? the 20dBm (0.10W) specified.? Is this too good to be true?>>>>>>>>???? Note the shield was not designed for the Raspberry Pi 3 B+ so it>>>>???? can't be fully inserted on the 40 pin GPIO plug, but seems>>>>???? stable enough partially inserted.? Getting WSPR reports from>>>>???? across the USA and occasional overseas reports too.>>>>>>>>???? Keith - KE4TH>>>>>>>>???? <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>>>>>???? 	Virus-free. www.avast.com>>>>???? <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>>>>>>>>>>>>>???? _______________________________________________>>>>???? hfsig mailing list>>>>???? hfsig at lists.tapr.org <mailto:hfsig at lists.tapr.org>>>>>???? http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org>>>>>>>>>???? _______________________________________________>>>???? hfsig mailing list>>>???? hfsig at lists.tapr.org <mailto:hfsig at lists.tapr.org>>>>???? http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org>>>>???? _______________________________________________>>???? hfsig mailing list>>???? hfsig at lists.tapr.org <mailto:hfsig at lists.tapr.org>>>???? http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org>>> > > > _______________________________________________> hfsig mailing list> hfsig at lists.tapr.org> http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org> ------------------------------Subject: Digest Footer_______________________________________________hfsig mailing listhfsig at lists.tapr.orghttp://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org------------------------------End of hfsig Digest, Vol 40, Issue 3************************************-------------- next part --------------An HTML attachment was scrubbed...URL: <http://lists.tapr.org/pipermail/hfsig_lists.tapr.org/attachments/20190324/220630da/attachment.html>------------------------------Subject: Digest Footer_______________________________________________hfsig mailing listhfsig at lists.tapr.orghttp://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org------------------------------End of hfsig Digest, Vol 40, Issue 4************************************
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