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....was? supposed to read? "a low pass filter above 20 METERS"? (not MHz)

cheers,? gotta go cut some grass before it pours again....

gordon

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Warren, you are right on, but you might not have seen all the posts where I did exactly what you are saying.? ?Both BEFORE the daughterboard and AFTER the daughterboard so i had proof of its effectiveness.? ?I also did some calibrations of the S-meter using BNC attenuators (which is all I have).? ?I then did the suggested measurements of today, measuring bleed-through (unmeasureable, whereas I was clearly able to measure the harmonics and able to measure their reduction by moving the input side of the relay chain OFF the board.)

Here, I'll see if I can find the posts (I'm not too used to that):

(1)Very first "before" measurements:? ?/g/BITX20/message/57840

(2)Complete baseline data:? ?/g/BITX20/message/57974?

(3)?Calibration of the S-meter and proof that the measurement setup itself didn't have bleed thru:??/g/BITX20/message/58070

? [This distinctly showed that 1 S unit in the range of 7-9 is 12 db onthat receiver on that frequency)

(4)Photos of the measurement setup:??/g/BITX20/message/58070

(5) DAta?AFTER daughterboard:? ?/g/BITX20/message/58070

What I CANNOT prove is that the receiver maintains identifical response at all frequencies (hence, is "flat")? however it is reasonable that the differnces aren't mroe than a few dB based on specifications for rigs of this price range etc.? ?

Poor man's spectrum analyzer.? ?What is problematic is the 24MHz harmonic range --- here I achieved only 6 dB reduction so there is something else going on there...maybe a series resonance in a filter or somethign I haven't thought of.? ?Every other range was dramatically reduced by the daughterboard system.? ?So for my purposes --- a low pass filter above 20 MHz and I have every digital band I need for what I need out of the radio and I don't need to use the bands where the "spurs" are a thorn.? ?

Hope that makes more sense.? ?

Cheers,

gordon

Hi Gary,

it could also be a timing issue.

At line 2327, there is a short 100ms delay:

delay(100);               // allow the voltages on the Arduino inputs to
settle for some milliseconds after power on

Perhaps the 100ms is just not enough for your radio.
You could try 200ms and see if it helps.
Simply change
delay(100);
to
delay(200);
Then recompile and upload to the Raduino.

Please let me know if this helps.

73 Allard PE1NWL

The ARRL Board of Directors has elected Howard E. Michel, WB2ITX, of Dartmouth, Massachusetts, to be ARRL's new Chief Executive Officer. He will start on October 15. Michel (rhymes with "nickel") is currently Chief Technology Officer at UBTECH Education, and Senior Vice President of UBTECH Robotics, a $5 billion Shenzhen, China, artificial intelligence and robotics company. As the Chief Technology Officer at UBTECH Education, Michel helped build this company from a startup in China to $100 million in valuation.
Full Story......


NNNN
Larry W8LM
ARRL Life Member

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Hi, I get that.? ?I but Icannot measure it at all frequencies.? I don't have a spectrum analyzer, I have a RECEIVER and I've calibrated portions of its response in order to use it as a poor-mans spectrum analyzer.? ??Presumably the blow-by?is capacitive for the most part, but not at all parts.? ?Lacking a spectrum analyzer, I measure the effective blow by at ONE frequency and then draw assumptions at others based on a model that it is primarily capacitve in nature (which has been the major point of discussion for weeks now......)

So if you know that capacitive reactance goes down by 10X when you increase the frequency by 10X, and in both cases you are feeding into a 50 ohm load.......the voltage you're going to get will go up on the order of 10X.? ??

?Thus you can make a prediction (based on the model) of what the bleed through might be at higher frequencies.? ?Or you can risk your rig by making other measurements if you don't have any other way to do it (which is me).? ?Does that make more sense?

Cheers,

gordo

Gordon

"Bleed through" or "blow by" at the operating frequency is not the issue. It is bleed through at the 5th and 7th harmonic that allows those harmonics to reach levels that are non-compliant.

WA8TOD

The cap does not need to be a 500V part even at 28V as the mosfets will self destruct
at 100V, so a 100V cap is fine so long as it can handle high RF current.

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The measurements that I made? for the daughterboard? bleed-through indicate that for the ENTIRE SYSTEM,? including the printed circuit board, connecting leads, relays, coils, coil wiring?and all the RF?wiring,? the bleed? through is almost NEGLIGIBLE. (lifted the bottom green wire in the accompanying photo and measured bleed through that had to go through ALL SIX RELAYS).??? Far, far below the pass through the filter....? down to unmeasureable on the ICOM718..whereas properly filtered harmonics? were depressed into the S5 or S6 range from 30dB overS9? fundamental (as predicted by others' measurements indicating the FILTERS had acceptable performance)??? ?Measurement performed?at 3.5? MHz.? Presumably capacitive coupling would increase related to frequency, perhaps 10 times the amount would be expected?at 30 MHz --- but that would only be 10dB more signal, perhaps reaching to S2? ?I don't want to risk my finals by doing? the experiment over and over.? ?The bleed through with a daughterboard --- even with unshielded wires --- is far far far below? the requirements to meet FCC specs.? ? (-43 dB being? somewhere around S7.5 in my tests).? ? Get the relays separated, get the things apart physically that need to NOT bleed into each other....and it isn't that difficult to fix the harmonics.? (The spurs are a different issue).? ?

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I decided to test the? little daughterboard system that I built to move the input filtering off theboard.

Everything connected:? 80 metersignal (has to go thru three relays on the board and 3 relays off the board):? S9+30 dB in my apprxoimately 70db attenuation system.

Remove the wire from the soldered-to-the-trace input to just the 80 meter LPF, lay it a couple centimeters to the side....

Signal? dropped to barely hearable and S0.

30 db for? the portion above S9? (verified with attentuators)

18 db more toget to S7.5? (verified? with attentuators)

Unknown from S7.5 to S0 but likely at? least 6db/Sunit (sincethose above7 were 12dB perS unit measured) --42 db

Total isolation at 80 meters roughly 90 dB

?at the very least (down to the verified? S7.5 point) 48 dB + whatever it takes to go from 7.5 to0??

Icom718.

So the isolation at 80 meters seems good....probably declines with frequency?

gordon