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Here is what I did with my BITX40. Installed an 8 pin microphone jack and use the mic from IC7300. It works good.

Denis, WB8SKP

On the uBitx website, there is a great explanation of how to use the amplifier board for uBitx by John, WK2ETA.?
--
72 and God bless
KD4EPG

I used to use a signal generator (analog), frequency counter, and a diode load
so adding even a digital oscillator DDS or NCO was a giant step forward in
making basic measurements.

If a SA at ~1500$US is out of reach the lowly 9850 DDS and arduino plus a
RF power sensor (8307 or one of the many others) will allow many of the
same measurements at a fraction of the cost in exchange for time to plot
the points.

It is also possible to use the above to plot to a graphic display?
by taking the power sensor output to the analog input of the arduino
allowing graphic display of the results.?

The 5351 is good but the square wave output will mess you up for many
measurements due to the rich harmonic output.? Two common measurements
are SWR and filter bandwidth/cutoff are hard to do with harmonics present.

Allison

Thanks Bill,

I, as many others enjoyed assembling the bitx40 and the ubitx, for my purposes, dragging around a bag full of outboard filters and other accessories will not work. Perhaps to some degree I am spoiled by having access to high end gear, but I am aware that it’s not prudent to compare a Harris to a ubitx. I wish not to besmirch Harris by putting the ubitx in the same sentence.

my understanding is the bitx was designed and built as a kit for those that wish to assemble, experiment, dabble in Arduino sketches etc, and by the number that have been sold obviously has a large following.
There is a need for a simple solid rig that doesn’t require a lot of fiddling about, and is reasonably priced and meets regulatory criteria.

There should be some warning or reminder that if you plan on doing any modifying or hacking that you should ensure that you don’t produce any transmitted products that may interfere with other services, especially any that might fall in the spectrum allocated to government agencies and services, as well as commercial, and international interests. You might get away with it in the ham bands but you certainly won’t if you cause superfluous transmissions in other spectrum allocations.

Buy filters, there are some great little devices available at QRP LABS.

Cheers and 73

WRS

IF THE PROCESS IS FLAWED, THE OUTCOME MOST SURELY WILL BE FLAWED

Allison

The 20 dB figure was for the filter assembly as a whole and not just for a discrete filter. Since that post I have cleaned up the measurement and reposted filter sweeps in situ as well as a measurement of the relay itself. Those updated measurements are posted.?

I am very sure the filter itself is more than adequate even with the high harmonic content CW. It is the relays and surrounding circuitry that allow the crosstalk.?

WA8TOD

Gordon,

The Rigol DSA815T I bought one to back up my HP8568B because the HP does not
have?a tracking generator and finding a working one was approaching the price of a Rigol.
While I still prefer the HP the Rigol does work well has modern interefaces for remote
control and screen capture/storage.? Being an easy 60 pounds lighter?is portable.?
I've even run it on a small 200W inverter and 33ah battery in the field (it uses maybe
50W).

The tracking generator that was the desired feature and it makes the instrument
a good second place for things I'd want a PNA like the Agilent 8357A?for.? That
is things like? SWR analysis, 1 and 2 port network analysis.?

The tracking generator is worth the cost difference.
That's a lot of capability in a small box.

When you consider that many hams spend 1000-2000 for a mid range radio
and more the 1560$ (via amazon) was a reasonable ham purchase and a
dirt cheap?professional one.

Allison

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I am certainly not an expert but stand taller when I am on the shoulders of others!? Recently trying to find out how to "expand" the display to make use of my 4.2" I believe I may have your answer.? With your current file loaded into the Nextion Editor select the Device ID tab on the top.? That will pull up the list of devices supported, most likely with your highlighted as well as the Basic and Enhanced buttons.? On the left side you will see DISPLAY.? Click on that and you can select one of the four possible orientations.? Close that menu and back at the top find the Compile button, click that.? Then in the very top menu select File, Open Build Folder and you will find the edited .tft file to install in your display.? Hope you find this correct, let me know.

REALLY wish this reflector allowed editing of posts!!!!

I meant to add that the 2.7K resistors are pulled up to the 3.3 Volt rail out of the NANO, not to the 5 Volt rail which keeps the SDA and SCL signals to 3 volts or less and they provide a stiff enough pull up that any overshoots don't exceed the 3.6Volt MAX spec for the Si5351a.? If this weren't the case MANY of the factory Raduinos (over 5000 of them out there since the beginning) would be toast so this is not a worry.

Jim, W0EB

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yup --- agreed.? ?Need to have a pair of hemostats or something to protect the center insulation.? ?But somehow I did it as a teenager causue heathkit used those a lot.? ?

we seem to have a lot of hams today who aren't even up to the level of heathkit assemblers, and it is good to improve onthat!!!!

this forum has taught me a ton...

I saw the price of a Rigol 700....I might be able to swing it....? ?the 800 's seem to have the tracking generator but then the price is $500 higher..... is it worth it?? ? Or can I somehow use a si5351 below 100 MHz?

I am getting a little unit that is supposed to let me tune duplexers ($100 cheapie system from china)

gordon

Glen, concerned about your logic level translator implementation w.r.t. I2C bus.? This is an open drain bus.? Nothing should be actively driven High.? The high state is handled by pull-up resistors.? Pull-up to 3.3V from Si5351 supply.? ?If one part is actively driving HIGH and another part on the bus drives LOW, there is bus contention with high currents on the I/Os which could lead to part destruction.??

Rgds,
Gary

Not really necessary to use a level translator here.? 2.7K pull up resistors instead of higher value ones keep the I2C bus signals out of the NANO to under the 3.6V max in the 5351's spec sheet by a bit.? Keeps signals AND overshoots to 3 volts or under so completely safe.? It's the same way the factory original Raduino did it and there are thousands of them out there with no (or very few failures) due to 5351 problems not created by bad chips in the first place.

Jim

Warren,

Since I've sliced the board up its easy for me to sweep the filters (not modified) from the
point of PA injection to the output connector.? I'll set it up and post the result later.

However while on first glance 20 db doesn't sound right, i? don't expect more than 40db
which is still low. To pass it has to be better than it is.

However I have tried a low pass filter (5element)? at the t2 out out instead of the 30mhz and it was?
effective reducing the 3rd and 5th harmonics of 3.5mhz by 30db,? ?So cleanup before the?
power amp is still a good course to take.

Allison

Glenn,

Yes that one of many.? Your pointing out the specifics of the general issue of board layout.

For example if the indicated line was moved to the area more centered and had
ground copper on both sides its not an issue.

Allison

Gordon,

I have a 1k spool of it...? Doesn't mean I expect others less experienced to find it easy.
For some it might be the first time.??

Allison

Glenn,
Good catch!

Hi Walt,

I will attach to this thread along about here. There is a lot of tail chasing and obvious disappointment among uBitx owners. I admit that I have felt some discouragement, too. But practical remedies are contained in the fog being spewed.

In the "good olde dayes" outboard filters were added between a (naughty)transmitter and the antenna. That approach can help a receiver as well. That was before we had CAT or even computers to support CAT. My approach won't support Cat. Or will it?

When there are several pieces of gear working as the ham station and each has it's own bandswitch we quickly get into the habit of checking all those bandswitches whenever we change bands. Newfangled hams don't have this experience and maybe are not even aware of the possibilities. I will be building the needed filters - bandpass models because of the uBitx sins - and adding them into the lashup immediately after the antenna terminal on the uBitx. Next will be the SWR bridge and tuner to the antenna so that the 50 ohm filter is assured of a 50 ohm load. That renders the uBitx impractical for some kinds of field operation. Too many googaws in the kit to drag up a steep hill or out into the forest. The local park might not be quite so bad. If the people who are working on mods for the radio get a good solution then I will probably make those modifications to mine. Meanwhile I am going to use it with external filters.

And now back to computer control of the station with those bandswitched filters living outside the radio. The VFO and Raduino are NOT going to accommodate that. But that is not where CAT originates. Make your Willie Gates special computer change the bands in your external filter for you while it is changing the bands in your uBitx. I see a lot of bragging about computer skills. So just do it. The old mechanical bandswitches still work for me:)

I hope this helps some people get past the disappointment and enjoy their radios on the air - free of worries over regulatory issues or being *bad* neighbors. As for me - I have already used my uBitx GQ receiver to help me troubleshoot another broken radio so I am keeping it:) And using it on the air.

Spectrum analyzers are great for quickly making graphical plots and even drawing them 'on-the-fly'. The same measurements can be made by plodding through a series of measurement steps and putting the results on graph paper (or in a PC spread sheet). It takes longer but most of us are NOT manufacturing radios or working on other folks' gear for pay. So the time required is much less critical.

Good luck and 73,

Bill KU8H

--
bark less - wag more

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Another physical alteration that might be performed is merely to wire TWO different relays into each of the existing FOUR relay spots --- thus mechanically separating the two halves of the relays that do the jobs.??

This could be done with four little "daughter boards" with pins sticking out to contact the necessary holes on the original board, and TWO relays wired up above.? ? Messy, but it might provide the needed separation.? If needed, a metalic SHIELD could extend downward between the "halves" of the wiring.

By putting them at alternating heights, one might actually work within the existing lateral dimensions.? ?

And I'm sure several of you will come up with alternate solutions to key a completely separate 4 relays placed instead?on the FAR END??so that the switching can also be divided up among more relays.?

If warren is correct, then splitting the relay function may make a very significant improvement in the harmonics output (but not the spurs for the higher bands).? ?

This will lead to better designs for future ubitx's!? ?

Since I basically only use 4 bands (80/40/30/20) I might only need modify a smaller amount of the board realestate.??

Gordon

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warren, very nice work to answer a very crucial question....

so it's time to see if the relay can be

a) altered so as to be improved? (move wires, add shielding, to existing relay type)

b) replaced in some easy fashion (different device, or even?"replace" it by adding additional circuitry to move half the function to a different physical location)

Also reasonable to consider

c) given that there are FOUR relays, how can one cleverly reroute physical signals (board changes) and software changes so as to get X bands working, where none of the inputs pass near the outputs on a single relay???

In other words, for(c) you can reroute signals somehow and achieve at least TWO working bands, and possibly MORE by being more clever than I generally am....can someone see how to get THREE or FOUR signal paths working?? ?

Adding a manual switch of some sort would certainly also be a possibility!? ?

But MY goal this week is to give a nice tutorial to our ARES group on how to load up the IDE, and how to capture software upgrades to bitx-type products and load them onto these little critters, and a tiny bit of how to alter the code yourself as well......in preparation for our beginnning to "build" these devices on August 18th.

Cheers,

gordon

There is unfortunately not good news for a quick fix by changing lead layout on the board. It appears that a substantial portion of the input/output crosstalk in the filter bank is caused by having both the input and output of each filter routed through the same relay.

Attached is the level of crosstalk between to sets of closed contacts inside one relay. I removed K3 from my board and connected leads to it and then to the S/A - TG combination. The attenuation at critical harmonic frequencies for 80 and 40 meters are shown in the table. The numbers shown are for one relay. Since the 80 meter signal is routed though 3 relays it can be assumed that the crosstalk due to the relays alone is 4.7 dB worse for that band. For 40/30 meters the signal goes through two relays and would be 3 dB worse than the table numbers.

Bottom line: if all crosstalk due to board layout and lead length is eliminated, there is still an unacceptable level of input/output coupling caused by sharing of relays between input and output to make this filter bank design acceptable.

?