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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

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:

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)

I did more tests with both transistors today, adding 30M and 20M. Same setup as before, switching to the output transformer for the 4 and 5 watt tests, but then I thought why not check at the 3 watt level with and without the transformer--in most cases the gain was a little higher with the transformer. I didn't think of doing that until the 30M test, so the 40M data doesn't have that. Neither transistor will output 5 watts but I'm again surprised the lowly 2SD822 even puts out a little more at 20M than the 2SC5706. Probably not many folks have much interest in any of this but I had fun doing the tests and it's easy to post the data. :) 73, Steve AA7U

Here are some test results I did with the 2SD882 (from Tayda), and the 2SC5706 (from kitsandparts.com) on 40M. I used 12.8 V supply, and the Norcal 40A buffer, driver and power amp circuit with a 40M LPF with two harmonic trap capacitors. The Rutledge book "Electronics of Radio" uses these circuits for several Problems for the student--he drives the circuit with a function generator so that's how I did mine--that works very well plus you can record the input level for different output wattages, and compare it with other power amp transistors. I used a J309 for the buffer and a 2N3904 for the driver; I added an extra 2N3906 keying transistor, same as used on my earlier RF Amp Test Fixture and not the Norcal keying circuit. The Norcal 40A output drives 50 ohms directly and is suited for 0-3 watts output. I also tested for 4 and 5 watts output, changing the 18 uH RF choke on the output collector to the usual 1:4 step up transformer. I've attached the schematic for all this. The bottom line is both transistors work very well as single-transistor power amplifiers at 7 MHz, both giving up to and including 5 watts output from the 12.8 VDC supply. No heat sinks were used; very briefly keying the circuit allows for this. Both transistors, being quite small with small heat sink area, immediately begin to heat at key-down and power immediately begins to drop, so I have to catch the initial peak voltage across the 50 ohm dummy load on the Siglent oscope. The Rutledge book shows how to measure power amp transistor gain, converting the base RF voltage to dBm and subtracting that from the output wattage/dBm. I checked at 2 watts, 3 watts, then changed to the output transformer and checked at 4 watts and 5 watts--doing this for both transistors. I was surprised that the 2SD882 would give 5 watts output, at least on 40M; and gain was still holding up at 5 watts for both transistors. Note the phasing dots on the driver transformer--this is important (of course also shown in the official Norcal 40A schematic, and in the Rutledge book--I just followed the schematic). I experimented with reversing the secondary phase, monitoring the output power set to 2 watts with the proper phasing, and the output decreased by 0.1 watts when the phasing was reversed. NA5N's "Data Book for Homebrewers and QRPers" also mentions this, see section around Fig. 4-7. Chuck Adams has already mentioned to the list about the 2SC5706 being used in Diz's 5 watt transceiver and separate 5 watt amplifier, both use balanced pushpull output for the 5706's and cover up to 30 MHz. Of course proper heat sinks are used. 73, Steve AA7U

I've recently been testing a 14Mc power amp circuit, comparing several output transistors for 5 watts (45 Vpp) into a measured 50 ohm dummy load. I put a scope probe on the output and adjust for 45 Vpp with bench power supply set to 12.8 volts. I've found that a good transistor will give 5 watts out at that frequency at 12.8 volts. My reference has been a genuine 2SC5739. I adjust the input power from the function generator to give 45 Vpp output with the reference, then substitute other transistors to see how they compare. For instance the 2SC2078 is a popular transistor used in many CB radios as the final transistor. I have several genuine 2078s as pulls from old CBs (all over 10 years old) found in thrift shops. Most of them have a blown output transistor, but the few that are good I save the transistors. A good 2078 will give 46 Vpp or sometimes a little more output compared to the reference 5739. If you look on eBay there are literally hundreds of sellers of the 2078--the majority of them from China. I found a US seller offering 10 of them for a reasonable price and bought them to test. Every single one was a fake counterfeit with 30-35 Vpp output at 14Mc! When I complained, I was given a full refund. Someone sent me two 2078s to test, bought from a reputable US seller that most of us have bought from. Both of these too were fake counterfeits with 30-35 Vpp output. My last purchase of 2078s was from another US seller on eBay--his ad shows testing them on a Peak meter--he tests them for beta (gain) at the low currents any of these test meters can only test at. I corresponded with the seller, saying such a test at such low currents didn't tell much, that a real test would be for output power. He responded that he could only test the way he was showing but that previous purchasers seemed to be happy with these 2078s. I bought 5 of them to test--they finally arrived today, after 12 days! He's in Las Vegas, only a day or two mail time from me in Arizona, so for unknown reasons he appears to be very slow in shipping. I immediately tested all 5 and I'm very happy to report they all passed--3 gave 46 Vpp output, the other two 45.7 and 45.6 Vpp--exceeding the reference 5739 set for 45 Vpp. So these are the first Chinese 2SC2078s I can recommend, if you're looking for a decent RF power transistor. https://www.ebay.com/itm/286038719772 is the item and seller. Again note that you'll probably wait quite awhile to get these. (Email me privately if you want to know who the other seller of the fake ones is that I tested, I don't want to give his name out publicly since I've bought many things from him over the years and this is the first time I've seen fake counterfeit parts from him. Hopefully this particular part is the only fake part he's selling--listed as 2SC2078.) 73, Steve AA7U

Good morning, all. I'm thinking about a 160M build using one of my leftover NC40A boards. I actually only need the receive side but with a bit more work can eventually get a complete transceiver. For now, I could build and test the receiver first, leaving the TX circuitry unpopulated. The mute circuit is critical as it would coexist with my QRO rig on 160 using just a LoG RX antenna. My keyer can output a PTT signal to control it. I'd need a common xtal frequency and a practical VFO tuning range to make this operable in the CW portion of the band. Has anyone tried it? Howard, n3fel