The "copy & pasted" info (below) is the majority what's on the FB link which was placed several times earlier in this "Thread", and is being repeated here for those who don't have a FB account for the ability to view it...Eric, thank you so very much for your answer!! Very much appreciated. Also having no FB account, I would love for you to paste your infos here as I had a very hard time reading your posts. Sorry for the hassle. Despite my problems opening your pictures I read all your threads and was very impressed by your extensive knowledge and expertise.
Happy New Year
Giles
Title:
Conversion of the BLA-703 to operate for both the 10 and 11-meter bands, and also how to change / modify the "out-of-band" safety shut-down parameter (the 4-beep warning explained on page #9 of the user-manual) to what has been nicknamed as the "American-mode", for radios with less than "stellar" harmonic suppression (ie: "cranked & spanked" rigs)
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See the first (1st) attached photo of the rear, of the front-panel CPU board (central-processor-unit).
Near the bottom right of the board, you'll see where there was a VERY small "surface-mount" resistor (circled in red) of which is now removed.
Your own unit may have either the afore mentioned SMD "chip-resistor" (labeled as "000" ohm) or there may be just a small "solder-bridge" across the solder-pads.
When the 000 ohm resistor (or solder-bridge) is there, the BLA-703 will ONLY operate for the 10-meter band (as shown on page #8 of the user-manual).
Once it (the resistor or jumper) has been removed, it will now operate for both the 10 and 11-meter bands.
BUT., do NOT attempt to use the amplifier for the 12-meter band (ie: 25 Mhz), or you could cause damage to the 16 MOSFETs (and other components) contained therein.!! This is because as frequency decreases (towards the 12-meter band) the "gain" of the amplifier increases greatly, and can be seen at the bottom of page #8 in the owner's manual, in the chart named "BLA-703 gain versus frequency".
*I hope I don't have to remind anyone, that the amplifier MUST be un-plugged from the AC outlet BEFORE the above modification is done.!!
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Now., this next SUPER easy modification (of the internal "firmware") is for those folks that may have radios that are not as "RF-clean" (of transmitted harmonics) as they should be., caused by either your radio being "cranked & spanked" (as I call it), or the output LPF (low-pass-filter) circuit not being as well designed as the manufacturer should have made it.
In these cases (ie: not so perfect transmitters)., you may find that one of the six (6) internal, self-protection modes (the "4-beep" out-of-band warning mentioned on page #9 of the owner's manual) may "trip" your amplifier back into standby-mode (which can be easily "reset" by simply switching the standby / operate button between, on / off / on).
This 4-beep, out-of-band warning, shut-down condition (when using a "harmonically-rich" transmitter) will occur more often when modulating with either a steady tone, or an "auuuuuudio", or a whistle.
If this occurs a bit too often (or even when just talking "normal".?)., there is a "firmware" change which can be very easily made by the operator / user, right from the front-panel itself.!
When the Firmware is in the factory default mode, you'll know this each time the amplifier is powered-up., and is indicated by hearing one (1) long "beep" each time the unit is powered-on.
To change the internal Firmware to be less sensitive to the out-of-band (harmonic sensing), 4-beep protection-mode (which is caused by the amplifier sensing 2nd and 3rd harmonics being generated by your transmitter)., you just start off with the main power-switch off.
Then., while holding in the SSB button (nice and solid), simply flip the power rocker-switch back on, while still holding the SSB button until it's finished "booting-up".
After that's been done., each time the amplifier is powered on., instead of hearing the one (1) long beep., you'll instead hear it produce the "Morse-code" signal for the letters A and M (ie: dit-dah., dah-dah) for what's been nicknamed the "American Mode" (because most American radios have been "peaked & tweaked" by either the "dealer" or some self-proclaimed, wanna-be "tech"), or that the manufacturer of the radio did not design the transmitter's LPF (low-pass-filter) to be as good in its rejection of harmonics as a standard, FCC-approved Ham / Amateur rig.
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BTW / FYI: Even some actual / true, Ham / Amateur rigs may still produce just enough harmonic-energy to "trip" the amplifier's VERY sensitive detection circuity "threshold", and may still need this Firmware change to be made...
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BUT., even with the "American-Mode" firmware activated, if your transmitter is "cranked & spanked"., and you "hold" a tone, a whistle, or an "auuuuuudio" for more than about 1.5 seconds, it will still "trip" the out-of-band (ie: harmonic) sensing circuit.
Folks NEED to remember., that this is NOT just some "wanna-be" Ham / Amateur, linear amplifier, like virtually all other transistor / sold-state amplifiers EVER made on the market. This amplifier is an actual "FCC certified" amplifier, which has gone through 10s of thousands of $$$$$ of testing and approvals to "the powers that be", and on top of that, it was painstakingly designed and engineered to be as "bullet-proof" (electronically) as possible., within reason of course.! ;-)
This amplifier was designed "from the ground & up" to be operated with true and "clean-output" Ham / Amateur transceivers, but of course will work just GREAT with CB and Export radios, that have at least a somewhat harmonically-clean output.!
I mean., how many other "true" linear amplifiers (whether FCC certified or not) have as many as six (6) different, built-in, self-protection modes.?!?
Again., see the bottom-left corner of page #9 of the owner's manual for all the six (6) self-protection modes, and then find me a comparable amplifier., output power, dual power-supplies, build-quality (9+ pound aluminum heat-sink and 2mm thick steel housing, totaling 30 pounds.!)., with which you'd virtually have to "work at" (because of all the internal protection modes) doing your best to "blow-it-up".!
*I hope the above mini-novel was both understandable AND informative for most Folks that have actually taken the time to read this point (and to those I say THANKS.!)., as I do NOT "make a Dime" doing all this research, taking photos, labeling them, my 2-fingered typing, proof-reading, editing, (each step several times over)., and spending $$ having phone conversations to Italy, to make as sure as possible, to get my information straight.!!
I also do it because I'm quite passionate about helping others to get a better "grasp" concerning all this Radio & Electronics "stuff"., to help those who actually want to know the Truth., and for those who are humble enough to un-learn decades of "urban-legends"
Regards / 73
Eric Klein
Klein Communications
Also as KY8E
