Thank you very much!

--
Tim Keller - KE2GKB

Evan

I don't expect us all to purchase spectrum analyzers, that we might just use a few times.? I am confident that repeatable solutions will emerge for curing the spurious, that should be good enough for builders that don't have spectrum analyzer access.? Our club members are building 23 units, and eventually we should have data on most if not each of them.??

I think there is evidence around that many ubitx units have spurs on both CW and SSB.? (A table of my spurious are here somewhere).? Others have data clarifying the transmit harmonics relate to leakage within the relays.? Adding a simple small board containing 3 relays to separate the input and output function should be a high success solution - most of our builders plan to use this method (we kitted it for them).? A few may try Axicon relays - it might work depending upon the severity of their spurs.? We found an added xtal filter will cure the mixing spurs, but at least 2 of us have degraded CW output on 40m.??

Curt

In the questionable tests that I have done on my v4 with the RF Explorer and SDRPlay as a Spectrum Analyzer, I have seen that the SSB signals do not have the harmonic issues, but does have the spurs, and vice versa.? The questionable part is the accuracy of the SA results.? I have worked out the audio two tone generator and step attenuater.? I have a personal belief from measuring the clock#2 signal with an oscilloscope that the harmonic content is very high, and that is being fed to the PA stage, before there is a chance to knock it down with the low pass filters.? One of these days I plan to temporarily place a LPF on the clock#2 signal for 8mhz and test the 40 m harmonics.? My guess is that there will not then be an issue.

If the experiment does prove that the harmonics start with the clock#2, then a switched LPF in place of the current fixed LPF between the first mixer and the PA driver may be the only solution to ultimatly solve the issue for CW.

My data also points to a legal SSB rig, as long as you do not overdrive the audio and you put in the 45 mhz LPF to remove the spurs when operating above 20 m.

I have received my v5 board, however I am still not sure of the reliability of the way I am able to measure spectrum content.? A Rigol or Siglent is still a significant investment, and have a lot of convincing of others (my wife) that it is a good use of funds.? I just bought an IC-7300 this year, so not sure I can squeeze it in at this time.? This long explanation is to justify that I will not be able to do a definitive test on the v5 board.? I had also checked at my club and when asked as to what SA that they might have, they all offered the RF Explorer as what they use.

Above are my opinions, based on my observations.? ?Yours may be different.
73
Evan
AC9TU

Great point, Curt -- thank you! I've actually been thinking about adding an external relay filter board anyway.? So far I only use it for cw, so many of the ssb aspects aren't terribly important immediately .??

On my v4 I did a lot of transistor replacements etc and liked the results . Not having a spectrum analyzer I haven't been brave enough to try ssb.??

Brutus

If it were me, I would not covert a v3 to a v5.? I don't recommend replacing over a dozen crystals !??

We don't yet have any data that a v5 has lower overall spurious than v3 or v4.? I hope it should be better but the data so far isn't that encouraging (to me anyway) for the factory board (we honestly need more than one sample. have not seen ssb data).??

I think any ubitx would likely be compliant if relays on an external board were used.? Whether axicom relays solve spurious may depend upon the board.? Respecting that >90% of us don't have a spectrum analyzer, it may be more of a personal choice whether to replace relays or add a relay circuit board.? Either might be compliant or somewhat close.??

Curt

I happen to have a new in box ubitx v3 that I ordered just before the v4 came out.? ?(My v4 is up and running thanks to the folks here!)

It seems that the v5, particularly the transistor and IF changes as well as different relay scheme, offers better signal quality.

I see the list here that details the changes from v4 to v5: (/g/BITX20/wiki/uBitx-V5-Changes)?and I'm aware the v3 might (or might not) have audio issues that will need addressed.

Aside from these, are there any other changes I'll need to make in order to turn a v3 into a v5?? Also, with these changes will I still need to make the L5/L7 and axicom relay mods?? I DO plan to swap out the driver transistors, add resistors, replace a cap as described on ubitx.net.

This may be one too many questions ... but looking at the "relay board with a bunch of pots" mod for equalizing output power, since the signal level there is low, I was thinking of using a?SN74CBT3253C multiplexer/demultiplexer chip in place of the relays in that mod.? ?I got the idea by looking at the schematic for the mcHF, which uses it for filter switching.??

I'm thinking of doing that mod by doing all the other fixes first, measuring the pot setting to get 7W CW on the higher powered of each band, then making a little board with the multiplexer and 4 appropriate 1206 resistors, with the board having ground fill and attached where the pot used to be with RG174.

What do y'all think?

Here we go:?

Of course, the new low pass filter at L31,L32,C205 would cure the spur
even if we did have a 90mhz 2'd harmonic present.
Adding that filter to v3, v4 rigs is not a bad idea if planning to operate above 17m.

The better transistors in the 45mhz IF should help diminish that 90mhz 2'd harmonic of the IF
that was causing the? (45mhz - DialFreq) spur on 15m,12m,10m.

For those curious about the math (arithmetic?) regarding this spur on v3 and v4 uBitx's:
The VFO (clk2) into the D1,D2 mixer is always above the 45mhz IF, so at 28mhz the VFO is a 45+28=73mhz
If the 45mhz IF into the D1,D2 mixer also has a 2*45mhz = 90mhz 2'd harmonic, that mixes with the VFO also.
So transmitting at 28mhz, we have a spur at 90mhz-73mhz = 2*45mhz - (45mhz+28mhz) = 45mhz-28mhz = 17mhz.
This only matters on 15m, 12m, and 10m, since on the lower bands the spur is above the transmit frequency
and can be taken out by the transmit low pass filter.? ?For 20m, the spur is at 45mhz-14mhz = 31mhz.

I'd expect this spur to not be so bothersome on the v5 as it was on the v3 and v4.
When transmitting CW, CLK2 is at the operating frequency and the 45mhz IF is quiet
(CLK0 and CLK1 are shut down).? So the spur only occurs when operating SSB.

Jerry, KE7ER

There is a link to Ashhar's github page on the hfsignals.

Technical

The Raduino?The ?BITX ‘s Raduino plugs into the main ?BITX board. It is an Arduino Nano powered, small, hackable board based on the rock steady Si5351 synthesizer with a ?16×2 LCD display, 6 analog ports, three oscillators and six digital lines. It comes preloaded with , so you can add all the features you want to!

--

Dear Bob,

all previous releases, including the related instructions, can be downloaded from here:

Hope this helps.

73 Allard PE1NWL

Kevin

I imagine there is something to gain, but not necessarily full compliance. Data seems to support less coupling in the axicom relay. But also spurious performance seems to vary across boards. If a very high rejection is needed, say more than 10 or 15 dB, it might not be enough. Here I am using a daughter board to replace the input relays in my v4. I don't yet have data on my unit, but it worked nicely for another local builder here. I hope someone will kit this solution for sale, as maybe its needed for all versions,? we'll see. The other spurious problem at the 45 MHz mixer path also needs solution in prior versions,? I haven't seen any v5 data on this.

Curt

Is anything to be gained by changing the Version 5 relays to Axicom?
Many thanks and 73
Kevin VK3DAP / ZL2DAP

开云体育

Scot has one of my RaduinoX PCBs.?? So he likely has a wrong connection to get the pot to A7 on the Nano.

I have sent him board pictures and schematics to help.?? The PCB is silk-screened with the Connector # and pin 1 on all connectors.? So it is just a matter of checking his wiring and making sure A7 is what his software is expecting as Tuning input pin.

He is probably OK now?

73's

Mike, WA6ISP

I'm using Amunters BitX 40 sketch and when I power up the BitX 40 VFO reads 7.000 and I'm unable to change frequency? with the tuning pot. Any Idea what I can do?
Thanks, Scot WB7AVU

-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...

Make sure the ptt sense is wired correctly. It may be booting in tx and not showing. The rig may not be txing rf power but might be false tripped in the raduino. Make sure the tuning pot is right as well.


--
David

?N8DAH

I've tried and tried to find instructions for Version 1.20 firmware in my Bitx40.? I've had links sent to me, all ended up being for a much newer version (usually 1.28).? Lots of pressure to 'upgrade' as well...

I DO NOT WANT VERSION 1.28!!!? I AM NOT "UPGRADING"!? (I suspect that my LO frequency needs tweaking, as my radio is not as sensitive as I'd expect - you can hear a 1 (or more) uV signal, although it's rather faint.? If there are any other aspects to that firmware, I would be very interested in learning about them!)

I don't need all the bells and whistles and I don't want them.? My Bitx is going to be a simple mobile SSB? qrp rig.? No CW, no digital, just SSB.? My only complaint has been solved by a quick fix kindly linked to - eliminating "VFO Galloping".? (I never thought to describe it that way!)

Please, if anyone has instructions for version 1.20 of the software (I've got the instructions for the radio - no version 1.20 instructions in it), please post them!

Again, I want instructions for version 1.20, NOT 1.28 and I am NOT going to 'upgrade'!? (I got really irritated at all the people trying to get me to change.)

Thanks!

Bob

I'm using Amunters BitX 40 sketch and when I power up the BitX 40 VFO reads 7.000 and I'm unable to change frequency? with the tuning pot. Any Idea what I can do?
Thanks, Scot WB7AVU

Can? you provide a link to the software ?
Thanks!

Mike WA3O