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More VXO stuff
7
Forgot. Note, in the SST, Wayne went with molded inductors. When NorCal did this (and Doug can verify) I'll bet that molded inductors were much cheaper than toroids. They do heat up as a side note. I reserve the right to go with toroids to get the optimum range. In the 1W and 5W, Diz went with toroids. He had the world supply of them. Look at the inventory at KitsAndParts.com that Mike has on hand. I just placed a significant order for ones that I need and want to use. The rigs used toroid inductors because you can wind to the optimal inductance value you need for maximum tuning range you can get out of the crystal critters. Less heating with larger surface area for heat dissipation using largest wire you can wind and get the turns you need. OK. I carry on too much. I know. -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Antenna Change Experiment[long again]
Been on 17m for 6.5 weeks now and you can see my results thus far in the signature block. Using a QRP-Labs QCX-mini at 4.2W with a one element beam (sounds better than a dual hamstick dipole) at 4m. Night before last was the most fun. Was about 10:45pm local. Saw that a ZL2 was calling CQ and spotted in UT. Fired up the rig and I could just barely hear him in the noise level. So, called and he came back to me with a 339, but it counts. Both A- and K-indices were relatively high, but adventure is just doing it. Thought I'd switch for the next 6.5 weeks to the red Chinese vertical that was discussed a month or so ago. Here is a mod that I HIGHLY recommend. Go to HomeDepot for 3 M10 lock washers. You find them the hardware section in a bag of 3 for a little over $2. Or, you might have them in your hardware can/jar for loose stuff. Put one between the whip and the red critter (center conductor connected). Put the other two between the radial lug and the red module and the radial lug and the spike. Previously I wondered if I hadn't loosened the spike and radial contact in twisting the spike into the ground and I find that the lock washers reduce the chance of doing it again. Not completely, but most likely if you take care in the field or yard. Report in 1.5 months. On the side. I dare you guys with your 40m and/or 20m SSTs to work a contact during this weekend CQ WW WPX contest. Sunday afternoon is a better chance when they have worked everybody else. I can't but I'm shooting for next year. -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Crystal Searching[long]
2
This is not an easy answer. It is mathematically, but there are some variances between manufacturers and quality control. Let me explain. The series resonant frequency of the crystal is determined by L_1 and C_1, the motional parameters due to the physics. In a VXO, we are interested in just how far we can "pull" the frequency of operation, say delta_f. We can approximate this value by the formula: (Colpitts oscillator is typical) delta_f ~= 0.5*(L_ext/L_1 - C_1/C_ext). L_1 and C_1 we can't do anything about. It comes with the crystal as it is manufactured. In both the SST and 1W transceivers, look at the schematics. What do you see in series with the crystal. Yep. An inductor, let's call that L_ext and a variable cap C_ext. L_ext is fixed. As you vary C_ext, you shift the frequency. At first you say, well heck let's make L_ext large and C_ext large. Several things happen. You can't shift far (L is fixed) and L_ext swamps the capacitance change. A bad side effect is that the oscillator stability goes to heck in a hand basket. This leads up the answer for the question. I have to take the different frequencies, different varactor diodes, different molded inductors and transistors (2N3904, 2N4401, or even a JFET) and see what gives the greatest range for each band, greatest output and if that is good at the output of the mixer, least drift, .... You see the problem, but I have the fixture set up on a Manhattan layout. As soon as I get the crystals off the boat, I will do the experiments and report to the group. In the meantime, maybe some of the group can also give their results from previous builds and lab work. Look at the frequency range of the specs of every rig that uses a VXO. This may help you see just how much you can in tunable range of the VXO. Get out the G3UUR and measure the L and C values. R_1 of the crystal is also at play in the range of frequency pull you can get and a large R_1 will get you drift due to heating. Since we are getting these things from China, there may be a spec sheet that gives some ranges, but crystal axis cutting and accuracy causes some variance between batches. That's why you buy crystals in bulk. They come from the same batch and setup and you are more likely to get a close match more easily. We used to see a date code, but with the HC-49/S, there is no room and the new crystals rarely show a batch code like transistors. BTW, the HC-49/S and the HC-49/U should have almost the same L_1 and C_1 values. Go to K8IQYs home page and go to the crystal page values he has measured. <https://www.k8iqy.com/miscellaneous/XtalParms/xtal_parameters.htm> L_m and C_m are the L_1 and C_1 variables used in the formula. You will see both sets of variables spread across the Internet. L_m and C_m are the ones used by the industry. I'll make up a table and put it on the web for my results to add to the body of knowledge to be found on crystals. Maybe W7ZOI has some values also on the web. If the circuit capacitance across the crystal matches the C_o value, then the circuit should resonant at the frequency marked on the crystal in parallel mode. This is just the tip of the iceberg..... FYI -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Colpitts Details: Do You Like Math?
2
<https://archive.org/details/introductory.electronic.devices.and.circuits.6th-robert.t.paynter/page/763/mode/2up> Most Colpitts designs I see hams use have the capacitor divider network with two equal values. It's just fine. In the SST, Wayne chose to keep C19 and C20 fixed and equal for all bands. In the 1W and 5W transceivers, Diz chose to have some values of C15 and C16 to be different on some bands and the same on others. I am assuming that he did significant experimentation on the values. Also note, C_x in the 1W schematic between the crystal and the inductor. Diz found this to sometimes extend the tuning range and sometimes it caused the circuit to fail to oscillate. Again, my plan is to try this scheme out on the SST to see if there are any possible gains. That's the end of this series of posts. I hope. The book above is a good one for some detailed electronics. -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Crystal Searching
2
Gang, For those that haven't stocked up over the years on crystal deals or renewing their stock like I am, here is a list for you to go through at your time of choice. If you are interested, I'd recommend you do so rapidly as the climate is a changing. See the 4.032 and 10.000 vendor and what I got before things changed. Presented here to save you time that I spent on searching the web and I just got the tip of the iceberg. Share if you have better deals. ------------------------ <https://www.ebay.com/itm/393816488432> o about $0.64 per critter for 10 with free S&H o I've ordered here and was happy and you get them quick. <https://www.ebay.com/itm/166477846005> o I got my 4.032 and 10.000MHz here when it was free shipping! But, the $50 S&H is ridiculous now. He did it after the trade wars started. List of vendors I've ordered from and some are on the boat as we speak. I'll come back with reports when I receive them, but I show them here as a current status in case the vendor later decides to change things for the worse. This list is for the small gamblers among us. I went out on the limb on this one. I'm not responsible for being the village idiot. <https://www.aliexpress.us/item/3256807441959330.html> 14.318MHz <https://www.aliexpress.us/item/3256806107320730.html> 15 freq options <https://www.aliexpress.us/item/3256806684489012.html> 10 freq options <https://www.aliexpress.us/item/3256805353383825.html> a bunch! <https://www.aliexpress.us/item/2251801854466699.html> options And while I'm wasting your time, take a look at how much quartz is being manufactured. Quartz crystals are used in more places than you think about. Enjoy. I know that I do for this one. Things start at 3:00 or so on the factory floor. <https://www.youtube.com/watch?v=lzHqhNoyx2o> -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Is there an easy way to test sa612 smd chips
10
Is there an easy way to test smd soic8 packaged sa612 chips? Doug
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QRP power measurement and AA7FO lab and web report[long]
2
QRP Power: See <https://qrpguys.com/12w-dummy-load-power-meter> manual for how it is done with a dummy load. Unfortunately QRPGuys are shut down for a month due to traveling on vacation. The power formula on the PCB is very very easy to derive and easy to compute on your phone calculator. $20 is pretty cheap for thing IMHO. I'd like them to change the pin out to allow a two pin Arduino cable to be used with the center pin on the board going to ground. Makes it easier for me, and I like easy. AA7FO Web Page: Because of the security notice threat that was coming up on my old web page, I have moved it. <https://www.qsl.net/aa7fo> Note that I have revived some of my legacy writings on Manhattan construction, 1W and 5W building guides for those of you still hoarding the unbuilt kits in secret storage locations. The money I save I'll donate to qsl.net to keep them going. Not a friend of money for nothing and chicks for free, as the song goes. I'm trying to get time to get back to writing, but its more fun to build and operate. I'll let you know how my combo of 10.000MHz(VXO) and 4.032MHz(IF) work out. I'll measure the MDS with the old S1-S9 generator from NorCal and report back first thing. You still have yours? Battery check. AA7FO YouTube Status: Lost use of my video camera after 20 years of faithful service, so if you are a vlogger, let me know offline (I'm sure this group isn't interested in how to do it) what a good deal is. Too many options on amazon.com. Want one with macro capability for the closeups of boards etc. Manhattan Build: Awaiting QRPMe pads to get the SST build going. FYI. If you look at the crystals needed, some are very hard to find. But, look at the 1W frequencies in the retired kits on kitsandparts.com for easy frequency combos to find on ebay and aliexpress for less than a quarter a piece in quantities of 10 with free shipping. Search the isles for what you need. 40m is the tough combo. Experimental Venture: Someone in this group can open source a technique for using the cheap Si5351 module to replace the VXO and allow us to use any on hand crystals for the IF we want with the usual caveats on birdies. May already be available from unknown source previously written up. FYI dit dit -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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2SC2078 again
The Las Vegas seller of the good 2SC2078 I've tested shows 25 available again, if anyone has not yet stocked up on them--and the price is the same $2.10 each. :) https://www.ebay.com/itm/286579232689 73, Steve AA7U
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Will someone who has a Wilderness SST please do some measurements for me. I need the measurements of the case, L x W x H, and the measurements of the board, L x W. Thank you in advance. Doug, KI6DS.
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soldersmoke DCR and rabbit holes
2
After rebuilding the DBM and adding better grounds between the circuit boards, I finally put the soldersmoke DCR to the test tonight. No joy. Puzzlement and head scratching. It worked on the bench. Very quiet when I moved it over to the radio table. A little too quiet. What gives? Ahh... maybe the cable from the coax switch to the DCR? Yup. Replaced cable. The tuning is a touchy and the oscillator is a bit drifty but I listened to CW and FT8 and old guys talking about surgery gone wrong and so can declare success. It was nice to build something from scratch and my parts bin. Haven't done that in a while. What was even better was all the hours diving into rabbit holes... do I really understand how a double balanced mixer works? or the diplexer? and why is it called a diplexer? what happens if I tune the BPF while it is attached to to the DBM? how would I add a band spreader to the PTO? What if I move some of the gain from the audio amp to between the BPF and the DBM? And so on. I am back to digging into mcclaning's "radio receiver design" and SSDRA and breadboarding circuits so I can poke at them with an oscilloscope. I am looking at building a better DCR a little more carefully than I built this one. Been a fun couple of weeks. Highly recommend it as a past time. 73 Bill K7WXW
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PCBWay current pricing for 10 boards
I thought that I would try to get 10 boards from PCBWay and see what the current political environment was going to cost me. The boards are under the 100x100mm area. In fact, 97x65mm in size. I ordered 10 1W boards and got a price of $21.14 USD and am told that did include any tariffs. I'll report back in a week if the boards make it through the port of LA or WA. I took the $6.25 or so shipping as I'm not in a hurry. I have a 12m serial #903 kit to build, but I want to do some other bands. Had most of them and gave them all away like the village idiot that I am. :-) I know that there is not enough demand for Mike to bring the kit back after 1,000s were sold already. He does have some 5W blank PCBs available. How many of you still have a 1W to build? How long are you going to wait? The challenge has been made to get 'er done. Are you using the one(s) that you built? The sunspots aren't going to get any better for another 10 or so years. Now I have to place a serious order with Mike at KitsAndParts. :-) Toroids here and toroids there..... FYI and thanks for listening, -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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While I have built several kits - a couple of keyers, Genesis G59 transceiver (hardest kit), SoftRock Rx/Tx, OHR SWR meter and dummy load (by far the easiest ;) ), I'm not sure where to start with Manhattan-style building. I saw Chuck's post recently and it reminded me I had looked at Dave's scratch-built SST20 and really like the build. I'm not sure if something like that is too hard for my first project or not... I'm not even sure from where I should source copper-clad boards, enclosures, etc. None of the hams I know locally are even remotely interested in stuff like this but I tend to gravitate towards things others avoid. No one around me is interested in QRP at all unless it's just across town / county so I don't really have anyone locally to whom I can ask questions. I'd like to take up Chuck's challenge and build an SST from scratch for 40m incorporating all the changes on JN3DMJ's page. Where or with what is the recommended starting point for building something using Manhattan-style? Regards, Joel, W4JBB
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Since I was going to test and optimize the VXO circuit for the 3 bands, I decided that the best way to do so is to use the Solderless Breadboard. Couldn't find the small one, so here is photo of the large one. Now how many of you have built a Colpitts Crystal Oscillator and looked at the output? I have and I knew ahead of time and have planned for increased filtering. Dave, AA7EE, and others brought up the topic. With the FCC harmonic restrictions, the old stuff won't be legal anymore. Might be project to fix legacy rigs in the closet. The 18.000MHz crystal (ECS) shown here and the circuit using the JH1PJL values gives one of the most ugly waveforms you'll ever see. :-) But, I just used the only 18.000MHz crystal in my stock to see how much range I'd get for later comparison with the 10.000MHz crystal (which I know I have 10 in stock hidden somewhere). Got 23KHz movement using a MV109 (didn't see my MV209 anywhere). Have other varactor diodes to experiment with also and going with the best one for stability and range of tuning. This is just the start and it will take a week, most likely. Stay tuned. Gotta fine tune each band. Getting about 300mV peak on the 18MHz crystal without fine tuning. I'm working through the transmitter chain to make sure we get 2W on each band. This is not a 5W rig. -----------other news items------------ 1. I have two graduate students in China that I am working with in radiative transfer physics on research I did 40 years ago. Everyone in the field at the time has retired and these two wanted to see if they could get some help for their research projects. Gladly. So it's taking some of my cycles. 2. I went ahead and put in an order for the QRPMe squares and we'll see how my layouts look when I get started on the SST. 3. I'm trying to get qlog installed on linux, but the instructions to add the repository and install seem to be broken. So, if you have this done, let me know offline. I want to get my contacts on LotW and qrz.com to confirm Qs for WAS later on. I think I've worked all the regulars on 17m and just have to wait for the stragglers to come along from the other states. :-) FYI dit dit -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Gang, Here is photo of my final SolderSmoke DC Receiver challenge project. I'll do a video sometime in the next few days for proof of life. The camera is giving me problems again. Time for a new one. ------------ Manhattan Projects. 1. The KD1JV all transistor project is on hold. I have built one and it has a problem with the high gain in the audio amp causing it to oscillate when the audio is turned up. If you want an oscillator, build an amplifier. The Hendricks Kits version, called the NADC (Nearly All Discrete Components) version used an LM386 for the audio and NE602/NE612s for the mixers. Maybe I should have payed attention. 2. The ADC is too complex for starters, so let's do the following. 20 years ago I was going to do the following, but never got round to it. Now is the time. Someone sent me the schematic as a suggestion that we do this one for the group, but I had one already from the original web site, which has disappeared and the WayBack machine has broken links. So I sent a copy to VA3IUL to put online. <https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/Modified_SST_CW_TRX_AA7FO.gif> I have asked him to put JH1PJL's call for the listing, so this link will break shortly and just replace my call with JH1PJL. This will save space on the groups file space to allow for later expansion. Now you don't have to find a video amp (LT1252) for an arm and a leg. I am going for 20m first. Go to <https://www.ebay.com/itm/374551304823> and start with the "Seller's other items" link and look at all the crystals available. I'm going with 10.000MHz for the VXO and 4.032MHz for the IF. This will start me out around 14.032MHz on 20m. N6KR went with [40m: 4.000 and 11.046MHz], [30m: 4.194 and 14.318MHz] and [20m: 3.932 and 18.000MHz] for the crystal pairs. 'seattleaccessaries' vendor does not have 11.046 or 3.932MHz and I haven't found anyone else that does either on ebay. I bought all my crystals from <https://www.ebay.com/itm/166477846005> for free shipping, but with the trade wars he jacked up shipping to $50 USD and you and I are not ordering with that in place. So, I need at least 10 volunteers to build a critter with the band of your choice. You work out the crystal combos. 30m will work as is and I have the 20m crystals worked out. Just need a combo for 40m and left as an exercise for the student(s). Q3 will be a 2N3904 and I'm using a 2SC2706 for the PA. Have to work through all the L/C combos for each band. Another exercise. Change LPF to meet current FCC specs. I'm waiting until after this weekend and I'll cave in and order some QRPMe pads. Rex is busy at FDIM and Dayton this weekend. Then I plan on copying the AA7EE layout for his SST. No reason for me or anyone else to reinvent the wheel and let's go for the chrome ones. <https://aa7ee.wordpress.com/2016/09/09/a-scratch-build-of-n6kr-and-wilderness-radios-sst-for-20m/> This will be like copying NA5Ns layout for the HP signal generator of old. I'll be using the KitsAndParts 1W keyer that Diz, W8DIZ<sk>, did. But, you can use any 8-pin chip that you have or can find to use or go without the keyer if you have an old external critter you like. <https://kitsandparts.com/keyer/> and you can order from Mike and get one for $5 plus S&H. I don't know if I still have a K1EL K9 chip laying around. OK. That's a first pass outline of the SST Manhattan Project. Clear off the bench and get out the pen and paper and get to work. This isn't going to be too hard, but it should be a challenge to us all. Not failure, but low aim is crime. First one across the finish line wins. Progess reports appreciated. I'm also going for a 9cm x 9cm form factor and homebrew enclosure, since I just bought a shear and brake for the bench. FYI es tnx, -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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SST Manhattan Project: #001 - Schematics
Here is another opportunity for you to teach something that you may know. How do you draw schematics. We've seen hand drawn schematics from several sources on topics here. It helps a lot. I know a number of you have your favorite software. Take my diagram and reproduce it and show us how you did it. If you have the time and are willing to do so. Of course, there is a few thousand YouTube videos on topics that you and I are interested in. You might talk me out of using my program in the future. My schematics are done with a program I started in 1975. It was written in FORTRAN on an IBM 360/50 and generated a tape that was taken to a PDP 11/20 and used to drive a Calcomp flatbed plotter to draw with a pen. When I used SGI graphics systems I rewrote the program in C and generated PS and PDF pages to print on Apple printers at the time. The image I posted is from the current program and the PDF file was displayed on a 1080p monitor and screen captured using screenshot on a debian LINUX system and generates a .png image for transfer to the group at large. It sounds complicated, but I assure it is pretty easy after you do it a couple of times. FYI -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Gang, Keep it simple for all. No reason to over think this project. IMHO. <https://archive.org/details/sst_manual_042217> is the original Wilderness Radio SST Manual. You need this for getting the band specific component values, if you can find the crystals. You probably want to go with the JH1PJL schematic posted earlier in related threads for a build as it eliminates the LT1252 video amp which is relatively expensive and very very hard to find. <https://www.aa7fo.com/manhattan.pdf> is a short tutorial I wrote up a long time ago and needs some updates, but should hopefully get you started in the right direction. Instead of looking around for another project, how about just doing the VXO? It's simple, easy to layout and educational. JFETs have become relative expensive compared to the $0.01 to $0.02 BJT 2N3904 or similar NPN transistor. For these reason, I have chosen to go with a 2N3904 for the heart of the VXO. LAB: Build the JH1PJL version or mine or yours. Show results from any measurements and photo or your layout. Attached is schematic for a revised VXO that I am going to use and you and others may feel free to change as you see fit. I'd like some expert to build up the JH1PJL JFET VXO and let's compare output levels and frequency tuning range. I have not labeled anything as this part is band dependent. I'm shooting for 20m using 10MHz VXO, so I'm guessing part values (from left to right as): [subject to change] 50K variable 100nF cap 100K BB910 varactor diode (about same as MV209 and easier to find) 22uH 10.000MHz crystal 47K (x2) resistors 68pF (x2) mono caps 470ohm resistor 2N3904 NPN transistor 470ohm resistor 2pF or so output cap On the subject of tuning range. The first question I always get on any VFO is the tuning range limits. So, let me ask you this rhetorical question. Does it really really matter? What about the days when we were crystal controlled and you couldn't move at all except by changing the crystal? How bout the Rockmite and 49er xcvrs? Stuck on one frequency, but still you had fun. The node, between L and X, is for an optional 10pF C0G cap for possible extended tuning range. Depending upon just how much test equipment you have, you can do some interesting tests on stability, frequency range and output. The most simple piece of test equipment for this is a general coverage receiver with a S-meter if possible. I leave it to your imagination for tests to do. 1. Look at EMRFD, chapter 4 on VXOs. 2. What is the output curve over the tuning range? 3. Any drift issues? 4. Waveform of output into different load values? 5. Tuning range using different types of diodes for tuning? ... -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY,WV MA,OH,OR,RI,MT,WY,WA,MI DXCC W,VE,JA,PY,ZL,TX9
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Does anyone have an SST for sale?
I am interested in buying an SST Qrp Transceiver. Do you have one for sale? If you do please send private message to me, Doug Hendricks, KI6DS Email address Ki6ds1[@]gmail.com Remove [@] and replace with @ Doug
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Thanks to Doug for reminding me I forgot to put the watts in. Looking at the watts, it doesn't seem like much change between transistors, does it. Voltage gives a much finer resolution if one wants to nitpick. :) On 5/16/2025 12:44 PM, Steve Ratzlaff wrote:
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NC40A PA transistor test (10 each of 3 types tested)
3
I tested 10 each of the three transistors currently available--2SC5706, 2SD822, 2SC2078 (from Las Vegas seller). (It takes about 5 minutes per transistor....) I used the same NC40A test fixture and 12.8VDC as before and the first transistor was same as before, note the AWG setting and output level is slightly different from yesterday. I kept the same AWG setting but noted the output level--this is quicker to do for multiple transistors. Steve AA7U 2SC5706 (from kitsandparts.com) 1. -5.0 dBm in for all, 28.5 Vpp out 2. 28.5 Vpp 3. 28.5 Vpp 4. 28.1 Vpp 5. 29.9 Vpp 6. 27.5 Vpp 7. 27.6 Vpp 8. 29.6 Vpp 9. 28.9 Vpp 10. 28.0 Vpp 2SD822 (from Tayda) 1. -1.5 dBm in for all, 28.6 Vpp 2. 28.6 Vpp 3. 28.9 Vpp 4. 28.1 Vpp 5. 28.0 Vpp 6. 28.8 Vpp 7. 28.0 Vpp 8. 28.3 Vpp 9. 28.7 Vpp 10. 28.5 Vpp 2SC2078 (from eBay Las Vegas seller) 1. -3.2 dBm in for all, 28.4 Vpp 2. 28.8 Vpp 3. 28.4 Vpp 4. 28.9 Vpp 5. 28.5 Vpp 6. 28.7 Vpp 7. 28.7 Vpp 8. 28.2 Vpp 9. 28.6 Vpp 10. 28.3 Vpp On 5/16/2025 6:17 AM, Michael Maiorana via groups.io wrote:
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Here are some output PA transistors I tested in the 7 MHz NC40A buffer, driver, PA circuit, with the function generator adjusted to give 2 watts output (28.3 Vpp) across the 50 ohm dummy load; power supply set to 12.8 VDC. My function generator can show the level in dBm but many do not so I've included the mVpp value too. I've listed the results in lowest drive level (better) to highest (poorer). The BSC 2N3553 is an eBay find from BSC--Boca Semiconductor Corp in Florida--I've tested several eBay 2N3553s and this is the only one I've found that compares well with the genuine old Motorola 2N3553 I have. https://www.ebay.com/itm/132285529329. If I left out your favorite 1.5-2W PA transistor, let me know and if I have it I'll test it too. Schematic of the test circuit attached. I didn't install the output zener diode since this is a bench test with 50 ohm dummy load and won't see an antenna. 73, Steve AA7U 1. Motorola 2N3553 -6.5 dBm 299 mVpp (old genuine Motorola transistor) 2. 2SC2314 -6.1 dBm 313 mVpp (old genuine CB driver transistor) 3. BSC 2N3553 -5.6 dBm 332 mVpp (from eBay seller Boca Semi) 4. 2SC5706 -4.8 dBm 364 mVpp (from kitsandparts.com) 5. 2SC2028/2 -4.6 dBm 372 mVpp (old genuine CB driver transistor) 6. 2SC5739 -3.5 dBm 423 mVpp (genuine, not from eBay or Amazon) 7. 2SC2078 -3.0 dBm 448 mVpp (from eBay Las Vegas seller I've mentioned before--Chinese transistor) 8. 2SD882 -1.2 dBm 551 mVpp (from Taydaelectronics.com) 9. Central Semi 2N5109 -0.5 dBm 597 mVpp (genuine Central Semi transistor) 9. Central Semi 2N2219A -0.5 dBm 597 mVpp (genuine Central Semi transistor) 10. 2SC2078 -0.3 dBm 611 mVpp (from Dan's Small Parts and Kits) 11. 2SC2078 +6.1 dBm 1.277 Vpp (from ME 40M kit)
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Sat 8:39am
Sat 8:39am