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Timothy Fidler
On Sun, Sep 16, 2018 at 12:07 AM, notlarc senrab wrote:
7.033. Mhz300/ 7.033 Mhz? ?x 0.95? x? .25 = 10.13 m each side of dipole. = 33.23 ft ; you say 40 ft? x 2? There is no chance that the forty foot antenna (as a dipole)? is resonant or presenting anything like 50/75 ohms impedance to the receiver cct? .? Sounds like you have no impedance match of any type in place.? I would suggest? a completely half arsed antenna installation? and no knowledge of RF at all (have you consulted the ARRL Handbook ?) and the TCVR does work,? but you have failed it by a rubbish installation job.? It is not a pocket radio with a whip antenna you know. ? Did you lead in with RG58 U? Coax or similar? DEFINITELY NOT RG59 ?? ,? it sounds not.? you might have? a prayer if you did a lead in with figure 8 wire this bad practice but often it has a Z of? 85 ohms or so.? I do have a feeling I am answering/helping a Troll enquiry here... |
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Re: Searching for IMD
¿ªÔÆÌåÓýAllison, at the beginning of my professional career 38 years ago I learned that to sketch level diagrammes will help a lot to understand the requirements of individual stages concerning gain, outputpower and even give some insight in IMD/ P1dB. A visiual display gives more information as jsut "bare numbers". So I just sketeched such a block diagramme with the power levels in between, see the attachment. From this point of view only the first stage can be critical in
respect of gain-- although a MMIC - (or its equivalent using
discrete components can do ?) can easily get this gain at "LF".? Henning Weddig DK5LV
Am 16.09.2018 um 02:13 schrieb
ajparent1/KB1GMX:
Iz oos, |
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ubitx V4. 3? ?random wire 2 leads in tree 40 feet long on second floor 60 feet up from ground cw very weak can heard one station not the other. What could I have done wrong, rechecked wiring. Only error on Mike original schematic was an error, Received message could understand it, where do I go from location United States VA. Any help greatly appreciated 73 On Sun, Sep 16, 2018, 2:54 AM Mike Woods <mhwoods@...> wrote:
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¿ªÔÆÌåÓýOM
You will need to give more details to get assistance.? For example: 1??? Which board v3, v4? 2??? What antenna are you using?? You will need a decent antenna to hear anything on any HF transceiver e.g. a dipole antenna, or end-fed halfwave, etc. 3??? What firmware are you using? 4??? What do you mean by weak CW? 5?? Where do you live??? Note that in some parts of the world (e.g. VK/ZL), in this part of the sunspot cycle, you won't hear anything except noise most of the time on any frequency except for the broadcast band (below 1.6MHz) ... Mike ZL1AXG On 16/09/18 6:37 PM, notlarc senrab wrote:
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No not from eBay aduino replacement board .? On Sun, Sep 16, 2018, 2:01 AM Praba Karan <vu3dxr@...> wrote:
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uBitx from eBay?? On Sun, Sep 16, 2018, 10:22 AM <snotlarc@...> wrote: Hi I purchased my unit in July same problem , order both board s off from eBay . my cw is week. Yesterday thought I heard cb or cordless phone , tried everything except flashing again. I'm no going to eat $139 for a device that never worked. checked all boards I never could receive we've on any frequency, only faint cw 7.033.150. any one any suggestions. 73 VE |
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Hi I purchased my unit in July same problem , order both board s off from eBay . my cw is week. Yesterday thought I heard cb or cordless phone , tried everything except flashing again. I'm no going to eat $139 for a device that never worked. checked all boards I never could receive we've on any frequency, only faint cw 7.033.150. any one any suggestions. 73 VE
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Re: 2N2222A vs 2N3904 sourcing
For Pete and repete:
Known problems and this was as of mid June.? IF your not aware of this log in to the form web version and read. History is amazing and repeated, repeated, repeated, repeated, repeated, repeated, repeated, repeated, repeated, repeated, repeated. Amplifier power vs frequency is poor. IMD extremely poor for power over 2W. Output Low pass filters, they don't. board layout. Spurs, unwanted and unfiltered mix products that show above 20mhz. Band pass filter after the mixers not existant.?? Carrier leakage that is not related to modulator or 12mhz filter.? Again board layout. Nothing new here. |
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Re: uBitx v4 new socket
Jack Purdum
We still have some clean up to do on the code for our JackAl board on the ?BITX, but here's a sneak peek. (Please keep this under your hat until we release it...it's not ready for prime time yet.)
? Jack, W8TEE
On Saturday, September 15, 2018, 10:29:24 PM EDT, Curt via Groups.Io <wb8yyy@...> wrote:
Jack See messages from July 6. Principle mod seems to he replacing audio IC amplifier with a discrete version. Just learning myself as our club is about to order boards. Curt |
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Re: 2N2222A vs 2N3904 sourcing
On Sat, Sep 15, 2018 at 04:56 PM, Tom, wb6b wrote:
That is a handy summation of the gains needed. If switching the pre-driver to a mosfet (or better bipolar transistors, if they provide the same gain advantage) could provide enough additional gain to relax the gain needed in the previous stages, then there would be room to tailor the gain (lower it at the lower frequencies).<<<> How about making the gain flat as in the same at 3 as at 30. using real devices that have decent gain... ?I've been though this so many times and 98% are either trolls,? stupid, or not paying attention. Pick one. >>>Before the design change of passing the TX signal through an additional 45Mhz filter that may have been possible. The 45mhz added filter has minimal effect on output power as its before the last mixer.? It may clean up some crap or its just 4-6db of attenuation keeping the mixer out of overdrive. >>With the additional filter and the newly discovered IMD issues, more gain headroom may be needed than the gain than can be had by improving the pre-driver.? Neither are new.? It was always believed to be poor only we have test data confirming. WIKI RTFM!? if its not there yet put it there there are only few thousand postings since May 2018 about all of this.?? Allison |
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Re: 2N2222A vs 2N3904 sourcing
Tom,
You keep missing that with 4 stages they have to provide the gain at 30mhz.? Its built with 3904s and they just can't do that. What the 40M bitx does is not relevant.? Why because it does it at 40M. The Ubitx does closer to 8-10W at 40M.? Proves not one thing.? Save for at 80, 40 and maybe even 30M its ok but higher it is really poor. Also the uBitx IMD is horrific above 2W.? So there more bad than that. Simple English its broke, and the broke is not simple. Allison |
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Re: Searching for IMD
I measured the OIP3 of the uBITX Bi-amp stage I proto built and the Hayward version, both at 45MHz using the 1dB gain drop method.
uBITX:? +20.83dB OIP3 Hayward: +20dB OIP3 Haywards Paper measures it at +22.3dB at 10MHz using the 2 x sig gen 'normal' method.? I used the rule of thumb +15dB'. (Some use +16) So, I also measured Haywards version at 10MHz to confirm.?? result +22.9dB OIP3 Pretty darn close!?? Not sure where this actually leads to though............ Glenn vk3pe |
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Re: Searching for IMD
Iz oos,
I was thinking whether a MMIC up to 10dbm and an RD06HHF as driver like in the 10w qrp-pa-2008 might make sense Whats that going to fix?? The transformers need to be reworked, the prior stages in the amp are are poor.? And a MMIC at 10dbm is near compression unless you get something ERA5 but then at 75 ma you only get 20db of gain. Think this out.? To get from the mixer to the antenna you need 60db of power gain total! Now if you used RD16hhf you get maybe 16db of gain more like 13 with feedback so the gain is flatter. For 1/10th the cost the IRF510 can do that.? Either way 13DB. So you need 47 db of gain call it 48 as a round number. Your going to get that from three stages. NOTE: The last stage must supply more than 500mw from 3-30mhz.? [likely gain at that power under 13db] The stage before that will have to supply maybe 70 (max) milliwatts. [likely best gain at that power maybe 15db] The stage before that at most 3-4 milliwatts. [gains of 20db possible at low power] Getting high gain at low power is easier.? Hard at higher power.? Its bad to run at max gain as then the results are variable from unit to unit. FYI most all fets will produce a lot of gain down at 3mhz, that's not the problem, its getting the same {or close} gain from 3 to 30Mhz. I've repeated this more than a few times in the past two days. All I hear is what about this fix. Go look in the wiki, its spelled out.? Don't like it do the research and think system level. And please do not bring up a monoband radio that may or may not perform well as its not relevant or even meaningful.? Its a monoband it does not not have to work at any other frequency and every time I look its clear it will not work in a 3-30 case. Allison |
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Re: 2N2222A vs 2N3904 sourcing
Hi Allison,
That is a handy summation of the gains needed. If switching the pre-driver to a mosfet (or better bipolar transistors, if they provide the same gain advantage) could provide enough additional gain to relax the gain needed in the previous stages, then there would be room to tailor the gain (lower it at the lower frequencies). Before the design change of passing the TX signal through an additional 45Mhz filter that may have been possible. With the additional filter and the newly discovered IMD issues, more gain headroom may be needed than the gain than can be had by improving the pre-driver.? Tom, wb6b |
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Re: Searching for IMD
Warren,
I understand it will fix getting a cleaner source and levels out of the IF. You still can drive the mixers harder than compression at which things get nasty with spurs and all. Hows that going to fix the power amp gain fade of 10-11 db from 3 to 30Mhz? The power amp is still tepid at best and suffers badly. Allison |
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Re: Searching for IMD
Warren Allgyer
That is not quite correct Iz. My plan is to replace the entire three transistor amplifier, taking the current input from C20 and delivering the MMIC output to C22. The MMIC I tested and published earlier in this thread is rated at +4 dBm out with 23 dB of gain and it produced excellent IMD with a little over 4 watts out. The MMICs on order are rated at +13.5 dBm out and the same 23 dB of gain. If they live up to specifications they will have more than enough output to drive the PA chain. Only testing will tell for sure.
WA8TOD |
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