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Re: 60 Meter homebrew rig IF frequencies
Hi Ryan,
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A couple of issues:
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1. 455 kHz doesn't lend itself well to? rejecting receiver images adequately. For AM BCB, it works OK, but the higher in frequency you go, the tougher it is to filter out the image frequency in your front end. Also the products (including the nearby LO)? from the TX mixer would be exceedingly difficult to filter out.
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2. Crystal filters for SSB would be next to impossible to design at 455 kHz for a umber of reasons (Lack of suitable crystals being the dominant factor) You'd have to consider mechanical filtering.
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It's got to be a superhet with a crystal filter. That's what I have as extra board blanks from the 40 meter transceiver project.? And anyway, I don't care for direct conversion or phasing SSB techniques.
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Steve
WA6ZFT
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PSSST-20 kit for sale
Hey everyone,
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I don't think I'm going to get around to building it. I was very excited about scratch building a PSSST-20 and the kit is awesome, but time constraints are causing me to be more realistic. I have a half built QMX+ on the bench that needs attention.
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Asking $120 shipped to the CONUS only.?
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If anybody is interested in a Kenwood TS-140s that mostly works but needs maintenance or something, I have one of those I want to get rid of, too. Cheap.
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--
Ryan Flowers - W7RLF |
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60 Meter homebrew rig IF frequencies
I am thinking building a version of my single band single band 40 Meter SSB transceiver? to work on 60 meters, but have to carefully choose an IF frequency.
The current IF frequency for te 40 meter version of the rig is 12.288 MHz. Since it uses the Si5351 you have to be careful about the odd and even harmonics emitted. A. For an IF of 12288 kHz: 2x the LO will be 10400-10800 kHz 3x the LO will be 15600-16200 kHz. 4x the LO will be 28352-29152 Khz? [10 meter ham band] 5x the LO will be 35440-36440 kHz Analysis (All frequencies in kHz): 1. If I design the transceiver to tune from 5200-5400 kHz, then the LO will be in the middle of the 40 meter ham band at 7088-7288 kHz [regrettable, but livable I suppose]. 2. 3rd order product (remixing, 3*LO-tx frequency) due to non exact impedance matching in the TX mixer: Low 15600-5200 =? 10400 High: 16200-5400 = 10800. Looks good 3. Closeness of LO to band (for effective filtering) 7288-5400 = 1888. Hmmm. Mediocre. May require a higher order post mixer filter. B. For an IF of 9000 kHz: 2x the LO will be 7600 to 8000 kHz 3x the LO will be 11400-12000 kHz. 4x the LO will be 15200-16000 KHz 5x the LO will be 19000-20000 kHz Analysis (All frequencies in kHz): 1. If I design the transceiver to tune from 5200-5400 kHz, then the LO will be in the middle of the 80 meter ham band at 3800-4000 kHz [regrettable, but livable I suppose]. 2. 3rd order product (remixing, 3*LO-tx frequency) due to non exact impedance matching in the TX mixer: Low 11400-5200 = 6200 High: 12000-5400=6600 . Unacceptable, would require a very high order filter. 3. Closeness of LO to band (for effective filtering) 5400-4000 = 1400,? Poor. May require a higher order post mixer filter. -- So the choice appears to be 12288 kHz for the IF, unless someone can suggest a better IF frequency with readily available crystals. If anyone has built a 60 meter SSB transceiver, I'd like to know what IF frequency you chose and why. Steve WA6ZFT |
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Re: RF Power Transistors
Here is the schematic of the PA transistor test fixture I'm using, and a picture of it with a reference 2SC5739 installed.
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It's easy and fast to simply bend the base and collector leads out at right angles, solder the base and collector to the appropriate leads, then solder the (unbent) emitter lead to the ground plane--and easy to remove it to test another PA transistor.? I use a 12 watt QRP dummy load, such as the one qrpguys.com sell, and mine measures 50.06 ohms, so the formula (Vpp squared/400 = watts) is appropriate. 45 Vpp gives a solid 5 watts output. I set the bench supply to 12.8 VDC for the test. Note the initial power seen on the oscope is the peak value as the transistor will immediately start to heat and power will decrease--only key down as long as it takes to read the voltage on the oscope. My oscope (Siglent DSO) shows the Vpp instantly as soon as I press the "key" button switch, so I'm looking at the oscope to catch the initial peak voltage. Once you've set the RF input to give the 45 Vpp output with the reference transistor, remove the supply voltage, remove the transistor and install another transistor to compare to the reference. Of course don't change the RF input level from the setting used for the reference transistor. If you have not tried to purchase a QRP-power level RF PA transistor recently, be aware that most of them on eBay and Amazon are fake counterfeits and will not perform anywhere close to what a genuine transistor of the same type will. That includes ones such as 2N3866, 2N5109, 2SC5739, 2SC2078, 2SC2166, 2SC1969--and it doesn't matter who the seller is. All the eBay sellers from China, in my experience, their transistors are all fake counterfeits. 73, Steve AA7U On 4/28/2025 5:11 PM, Steve Ratzlaff via groups.io wrote:
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. is the item and seller. Again note that you'll probably wait quite awhile to get these. |
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Re: Charles Kitchen, N1TEV SK
Sad news.
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My first ever successful regen build was a Kitchin design. 73 de VK2HHS Henrik On 28 Apr 2025, at 20:55, Alan N8WQ via groups.io <oalanjones@...> wrote: |
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Charles Kitchen, N1TEV SK
Gang,
I first discovered Charles Kitchen when I started looking for regenerative receiver circuits many years ago. A few days ago I watched this very informative youtube video in which Mike Murphy WB2UID talked about the character of Charles "Chuck" Kitchen, N1TEV and his regenerative receiver circuits. Mike did a great job talking about his friend and co-worker's circuit design techniques. 73, Alan, N8WQ |
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Fun With BJT (Bipolar Junction Transistors) For Biz Admin Majors
Folks,
Chuck mentioned scoring a bag of 2N3904s and I similarly discovered a mess o' 2N4401s. Suspecting that there may be caches of the popular NPNs (and their matching PNPs) around, here's a sample of a series of YouTube videos for those of us who want to monkey around and perhaps learn a bit. ?
? Basic Bipolar Junction Transistor Analysis: The Common-Emitter Circuit
? https://youtu.be/unkBcz1-nLo?feature=shared ?
? Basic Bipolar Junction Transistor Analysis: The Common-Collector Circuit?
? https://youtu.be/WZcCYgiGdd8?feature=shared ?
? Basic Bipolar Junction Transistor Analysis: The Common-Base Circuit
? https://youtu.be/zBBuKWwjKq0?feature=shared ?
The three above are selected from a playlist done for Bipolar Junction Transistors. The entire playlist are of this quality and are comprised of 15 videos.
And those 15 are part of an extensive series by Ralph Gable -- a retired electronics engineer -- who has put a lot of effort into a great number of videos he titles "Electronics for the Inquisitive Experimenter" including basic electronics to construction practices, and design theory. I first stumbled on Ralph's efforts when re-learning the ins and outs of my NanoVNA and then to tinkering with filters.?
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His method of teaching is thorough, precise, and aimed at the beginner (the ersatz Biz Admin graduate) and many come with accompanying documentation a la W2AEW's videos.?I highly recommend them as a great source of learning and study.
--William, k6whp -------------------- "Cheer up, things could get worse. So I cheered up and things got worse." |
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Re: New single band superheterodyne transceiver
The IF is 12.288 MHz which works well for 40 meters because it far away from the LO and band frequencies. For LSB the LO is in the 5 MHz range.
The crystals I used for the filter are CTS MP122's: Regarding crystal filter design: yes, it is a pain.
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There are birdies, but they're mostly low level and manageable since they get covered up by atmospheric noise. 7296, and 7261 are a couple of big ones.
7168 seems? be an emission from the Raspberry pi Pico and it is modulated at ~50 Hz.
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The 26 MHz reference oscillator is a TG2016SMN 26.0000M-MCGNNM3 made by Epson. Digi-key part number SER4426CT-ND.
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No SI5351 module used here ;). The SI5351 chip is soldered down to the VFO board I designed.? The only module on the VFO board is the Raspberry Pi Pico. That has a QFN package and I don't have the equipment nor the dexterity to solder QFN's properly.
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Steve
WA6ZFT
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Re: New single band superheterodyne transceiver
I rolled my own for both the mixer and the product detector. Its a diode ring DBM.? It consists of 2 trifilar wound FT37-43's with #30 AWG magnet wire, and 4 BAT54 diodes. The first mixer has a 100 ohm balance pot to help null out the carrier when it operates as a balanced modulator. The BAT54 diodes need to be matched for forward voltage.
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There is a footprint for an ADE-1 mixer in the product detector/transmit mixer on the PCB, but I didn't use it.
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Steve
WA6ZFT
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Re: New single band superheterodyne transceiver
What is your I.F. frequency?? I'm curious because I have a similar superhet receiver using the HYCAS board and an 8 MHz I.F.? I'm currently using a Si5351a for both L.O. and BFO. It sounds pretty good but I have a lot of birdies. Do you have issues with receive birdies? My Si5351a board (Adafruit clone) has a 25 MHz crystal. One step I might take is to go with a different reference oscillator frequency. Where did your 26 MHz Si5351a come from? Do you use a module, or start with just the IC? Moving my 8 MHz I.F. would be painful because I went to a lot of trouble designing and building CW and SSB bandwidth crystals for that frequency. 73/TU, Nick, WA5BDU On Sat, Apr 26, 2025 at 12:13?PM hwstar via <steve=[email protected]> wrote:
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hwstar
Henrik Stenstrom
Alan N8WQ
k6whp
Nick Kennedy
Lex PH2LB