开云体育

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

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