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Re: Chinese Linear R.I.P.
Hi Doug - no offense intended. QRP is fun. That's what ham radio is for - for me, anyway. Fun. But it's no fun when people don't hear you. And at my QTH, with my antenna, people mostly just don't hear me with 2 watts.
Also, I'm a ragchewer, not a QSO collector. 599-599-tnx QSO 73, not for me. And the instant somebody exits a QSO because they couldn't hear me, my hand goes for the power button. However, if you don'tDoug, that's just unkind. Shame on you. Actually, I have a perfectly functional TS-590S on my desk, and an Alpha 78. And an IC706MKII in the closet. And a 30L-1 in the shed. And a bank balance that would let me drop $12K on an ultimate whiz-bang ham station without even sneezing. But what would be the fun in that? - Jerry KF6VB -- |
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Re: Chinese Linear R.I.P.
¿ªÔÆÌåÓýDiscussion of amplifiers of modest size (50-100w) is pretty common across several large QRP mail reflectors I subscribe to, it came across here as little more than a playful jab.As I recall, Ashar specifically designed the uBitx to allow the finals to operate off a higher voltage to increase RF output (25W+?). Ken, N2VIP On Jun 8, 2021, at 19:25, Doug W <dougwilner@...> wrote:
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Re: Chinese Linear R.I.P.
On 2021-06-08 16:22, Terry VK5TM wrote:
*** Doubt it. That package is used only for dual RF devices. But theOn Wed, Jun 9, 2021 at 06:41 AM, jerry@... wrote:.....I see theI wouldn't bet on that, a large percentage of 'RF Transistors/FETs' device could be used/surplus, or failed-QC. And the amp I'm looking at uses a device that's characterized at 850MHz. The fact is, one proper HF LDMOS device costs more than an entire Chinese kit. - Jerry -- |
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Re: Chinese Linear R.I.P.
On Tue, Jun 8, 2021 at 04:11 PM, jerry@... wrote:
to boost a QRP rig into usefulnessI am assuming your intention was not to insult the 7,101 other members of this list that find QRP very useful.? However, if you don't like your QRP gear you could probably sell it and added to the money a 100w amp would cost buy a decent used 100w rig. ? -- |
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Re: Chinese Linear R.I.P.
Jerry I used to recommend that you set the bias pots for minimum current and then slowly increase one pot to increase the idling current by 100 ma, then increase bias on the other MOSFET until it increases by another 100 ma.? Now I am not so sure.? The device datasheet is probably your friend.? Calculate the load-line and find a current that is within dissipation limits and in a linear part of the load-line.? Gate capacitance (Ciss) should be the lowest capacitance device, usually IRF510, not IRF520 or IRF530. Arv _._ All, |
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Re: Specan Revisited
Farhan and Chris,
With the GALI-6+ still in place (it's U2, after the first mixer), adding a 6 dB attenuator between the generator and Specan caused the distortion product to fall 17.9 dB.? But the tone level only dropped 0.8 dB.? I could see some harmonic distortion in the IF amplifier output with a scope, suggesting significant non-linearity in the signal chain. Then completely removed the U2 GALI-6+ (and re-calibrated the firmware power meter constants).? There was already a 6 dB pad after the first mixer, so took the LO module output from that pad.? Results are shown below and are much improved.? With the generator directly connected to the Specan, the IIP3 is now -20 + 68/2 = 14 dBm (I think?).? When a 6 dB attenuator is inserted at the Specan input, the measured tones fall 5 dB and the distortion products fall below the noise floor. This seems to vindicate the two-tone generator though don't have enough dynamic range for the 6 dB attenuator test.? This seems like usable performance, though I may search for a replacement for the MAV/GALI to improve the noise figure. Thank you for your help, -- David KV4FP |
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Chinese Linear R.I.P.
All,
So I set up a test station in the garage, and was trying out the Chinese linear again. The uBITX was feeding the linear in CW mode, and I was giving it toots with the mike switch. The linear was plugged into the LPF, and the LPF into a 30dB 20W Narda attenuator. The Narda was plugged into a cheap step attenuator, and the step attenuator into a tinySA. Yup, the 3rd harmonic still really high. Let's try another band... All of a sudden, the power supply started buzzing louder, and the uBITX screen went blank. Oh, no did I burn out the uBITX? Nope, it was the linear. Almost a dead short across the supply pins. It sucked all 35A out of the Astron power supply and wanted more. I'm guessing that one of the final transistors let out the magic smoke. So people - what's the class act in 100W ( or so ) final amps to boost a QRP rig into usefulness? I see the same Chinese vendors have kits that use an actual RF FET - instead of a switching FET. - Jerry KF6VB |
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Re: RF power transistor all gone
I¡¯m sure you don¡¯t have a surplus?board with a 2SC3102 Mitsubishi transistor on it, do you? ?I want to get my Yaesu 857 running on VHF and UHF again and need to roll up my sleeves and get some parts and start soldering.
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On Tuesday, June 8, 2021, 12:47 PM, John Cunliffe W7ZQ <n2nep@...> wrote:
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Re: RF power transistor all gone
John Cunliffe W7ZQ
Wow I probably could have a hundred of those and still would not be able to satisfy the need.
They are all spoken for. That said though, I have plenty of other devices, mostly 50V or some 28V devices. They are used though and some are on circuit boards you can remove using a hot air gun. If anyone is looking to build their own amps let me know I might be able to help with a device or two. I had a couple of people asking me where the devices are from and how come I give them away. The new devices like those 30 are left overs found somewhere in a corner of analog transmitter buildings that are being torn down. I rescue those and any power amplifiers, test equipment, cables or other items that might be usable to hams? before they are thrown into the trash or going to be recycled / destroyed. I give all test equipment (power meters, scopes,analyzers) away to the local Ham radio or hacker community. I give away VHF and UHF final amplifiers to the local community or take them apart for parts if they are not usable like water cooled units.The "used" transistors come from that environment I test those before giving them away. Lastly, I give the items away because by corporate rules I can't make any profit of them. All those who have send me requests, I will put them into the mail probably by this weekend and I will include instructions on how to pay for shipping. Please do not pay more than the actual postage on the package. John |
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Re: TSW Teensy 4.1 based Raduino KIT still available
Comments on the TSW kit - it gives the uBITX IMHO a much superior UI
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to the original. The *hard* part is already soldered ( the SI5351a oscillator chip ). And the support from Jim is excellent. Mine did have a problem with tuning ticks. But it turned out to be the fault of the original display card ( which was not from Jim ). A new display card from Hiletgo/Amazon cured it. I'm told that I was the only person to report the ticks problem. The Teensy has a far superior CPU to the original Nano. Unfortunately, it also costs a lot more. - Jerry KF6VB On 2021-06-08 04:41, Jim Sheldon wrote:
FYI, TSW's Teensy 4.1 based Raduino for the V6 uBITX is still |
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Re: TSW Teensy 4.1 based Raduino KIT still available
I appreciate y'all coming up with this backup supply of compatible Raduinos.? ?I'm sure it has helped many people. Gordon KX4Z On Tue, Jun 8, 2021 at 7:41 AM Jim Sheldon <w0eb@...> wrote: FYI, TSW's Teensy 4.1 based Raduino for the V6 uBITX is still available and being shipped.? Even though PJRC.com is temporarily out of stock with Their Teensy 4.1's, is showing that they still have 355 of them IN STOCK as of this morning (6/8/2021 @ 06:30 CDT) and roughly the same price as PJRC advertises. |
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TSW Teensy 4.1 based Raduino KIT still available
FYI, TSW's Teensy 4.1 based Raduino for the V6 uBITX is still available and being shipped.? Even though PJRC.com is temporarily out of stock with Their Teensy 4.1's, is showing that they still have 355 of them IN STOCK as of this morning (6/8/2021 @ 06:30 CDT) and roughly the same price as PJRC advertises.
Check out our website for further information on the T4.1 Raduino kit (kit only - this is NOT available in a factory built version) and it comes less the display and Teensy 4.1. Thanks for looking, Jim, W0EB TSW Project Coordinator |
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Re: Tx current draw
Evan, no problem. Just enjoy your ride. I gave up my bike a while ago as it was getting too dangerous out there with the idiots on their cell phones and high on some junk. Be safe. Barry On Tue, Jun 8, 2021, 1:16 AM Evan Hand <elhandjr@...> wrote:
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Re: Tx current draw
Barry, There is a voltage chart in the files section of this group for a v4. The circuits are the same as the v6 for the sections from Q90 on through the finals. ?Search for Raj¡¯s spreadsheet using his call sign - vu2zap.? I will check tomorrow when I am back at my shack.? 73 |
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Re: RF power transistor
On 2021-06-07 19:40, John Cunliffe W7ZQ wrote:
Gents,Hi John, I'll take one. Paypal you the shipping? - Jerry KF6VB p.s. Are those Chinese kits that use the similar device any good? Are they better than the ones that use the two 530 fets? |
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RF power transistor
John Cunliffe W7ZQ
Gents,
I cleaned out an old transmitter building that will be demolished later this week One of the items I have and will be available to the group for shipping cost are Transistors ACDN301M. It is a 100W UHF transistor that can do 100+ watts on HF. It is in a Gemini package. If someone wants to try their hands on a nice 100+ watt amplifier let me know and I ship you one..domestic only please one per person please. I have 30 of them first come first serve by e-mail time stamp.? https://www.digchip.com/datasheets/parts/datasheet/009/ACDN301-pdf.php John. |
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Re: Specan Revisited
David, It is also possible that the IMD is being generated in the two tone generator! To know this, insert an attenuator pad between the generator and the specan. You should see the imd go down by twice the attenator value (3db of imd down for each db of attenuation). I discovered this problem with my early two tone generators.? On Tue 8 Jun, 2021, 7:12 AM Ashhar Farhan via , <farhanbox=[email protected]> wrote:
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Jim Sheldon
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