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Re: Harmonics and Relay Replacement
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Gordon Gibby
¿ªÔÆÌåÓý?Evan, the design is a compromise that has deficiencies that were not originally well recognized.? ?Thanks to some persistent work by some members (I forget all their names but one reallly worked hard at it!)? the dificiencies were recognized.? ?
45 odd years ago my first rig, a Heathkit, had deficiencies.? ?I knew almost nothing, but in the ensuing 6 months I learned a ton of electronics to stop those darned key clicks.? ?And the rig went back and forth to Benton Harbor, which was FAR slower and
more difficult for me than buying something from India? or China is today.? FAR slower.? ?
We all bought this innovative, stripped down, dirt cheap rig from a nearly 3rd world county, amazed at the accomplishment of the designer.? ?I certainly did not expect it to be a Flex.
SO MANY solutions have been published and TESTED? (allison being one of the most prominent teachers in that regard) that it is simply no longer able for me to keep up with them!!!? Pick the one you like that you find proof for.? ?I made extremely simple
measurements using a dummy load and a resistive divider and a secondary communications receiver that indicated an $11 solution with an outboard partial relay box solved the issue of harmonics.? Had I used coax cable, probably would have worked even better!?
Others made even better solutions.? Raj and others have made huge inroads on the spur issue.??
This is a chance for LEARNING and I and many others have profited GREATLY from it.? ?I'm off learning duplexers now, but one should not pass up the opportunity this little gem provides.? ??
Mine has done WINLINK, and ALE, two fascinating techniques I needed it for at the time.? ?It does PSK, WINMOR, ARDOP and would probably even do PACTOR if I conneccted up m pactor modem to it.? ?Just don't overdrive it!? ?I learned how to program for an Arduino
from this little gem and learned the IDE from it.? ?I then built my own Raduino board and started building a SWR system and then tried to build an antenna analyzer --- and learned the difficulites of resistive bridges and how i really needed to understand
some of that better.? ?How much did i pay for all this education?? ?One uBitx.? ?pretty cheap education, huh?? ?The first reading i did on this blog -- ilearned more about mixers than I had ever known in my life.??
You know how much they charged me for that education?? Zero.
you can look at life from up or down, but there are ways to come out on top if you wish.? ?
Cheers! Gordon Gibby
From: [email protected] <[email protected]> on behalf of Evan Hand <elhandjr@...>
Sent: Saturday, December 29, 2018 8:13 PM To: [email protected] Subject: Re: [BITX20] Harmonics and Relay Replacement ?
OK, I have been following all of the ubitx threads since September, and still do not know what I must do, definitively, to insure that my rig is compliant.? I thought that I had that from this thread, however Ashhar and Raj had different solutions to the
spur issues, with agreement on the relay replacement for harmonics.? On Ubitx.net, Raj's solution is the one given for the spurs.? On the last email go round with? Raj, I was informed that there is still a possible IMD that does not yet have a solution, though
it can be imporved with different biasing and or transistor replacement.
I had planned to run it into a linear, however that is off the table until I know that the spurs and harmonics are not an issue. 10 watts for me (antenna limited by home owners association) is not going to cut it.? I have tried to make contacts on 40m SSB with limited success.? The current antenna is an OCFD in my attic.? SWR is OK, however I am sure that the effectiveness is limited by the location.? No real choice, as cannot mount it outside (VERY new neighborhood with only young trees, no place to hide). With the above, my options now become: 1 - dump in the trash and buy a "real" rig (building/solving technical issues is my main reason getting back into the hobby, so not a real option) 2 - Acquire all the tools and skills to insure that the fix really works. (biggest being a SA - $1200+) Since the most fun of the hobby for me is the building and problem solving, I will be going down option 2.? However if you look at the cost of the SA compared to an Icom IC-7300 (the one I have been looking at) I would be better off from a financial point to just buy the better rig, even this far into the parts acquisition. . My point for making this long texted response is that I am not in the norm for the majority of people that would be purchasing this rig as a means to get into the hobby.? Most are bought as an alternative to the high cost rigs because they are on a paper boy budget (do they still have young people doing paper routes?). What they need is the definitive solution that IF they apply it, then they can be assured it will be legal.? Saying that it is their rig and they need to insure compliance through testing is not possible for them.? If that is the case for HF Signals, then Ashhar REALLY needs to warn that full testing equipment AND experience are required OR that it can only be built and put on the air under the supervision of someone that can provide that service (club builds with all fixes included that have been tested by the "Elmer" of the club). I thought that there was enough testing and verification that we had solutions to the problems.? If that is the case, then HF Signals needs to publish them, on their web page, as the solution that has been verified to fix the issues.? As the provider of the rig they should have the test equipment and sample size to verify the solution.? What I am asking is that HF Signals steps up to owning the problem and publish how to fix it, including a way to verify.? That or change the advertising to indicate that it is not a complete solution. I will apologize now for the rant.? If I get enough emails or comments complaining I will drop off of the board and go my own way. Evan AC9TU |