Re: Spurs for Dummies? #ubitx-help

Gordon Gibby <ggibby@...>

Fabulous explanation Alyson!

We may be assembling these with some technicians in our club, so we may want to get our hands on some 10 m bandpass filters, they seem easy to find.  

On Jun 8, 2018, at 15:22, ajparent1/KB1GMX <kb1gmx@...> wrote:

The below is BOLD large print to make this very clear.

For bands below 20Mhz its NOT an issue as the low pass filters catch it.

It is only a potential problem for SSB and frequencies greater than 20mhz.

NOTE: due to the way the uBTX does CW it is never an issue on any band.


The short form is when you mix two frequencies you get a third, in a perfect world.

However diode mixers are handy but they can present problems.  If any of the three
ports are mismatched (think SWR) The signal can reflect back in.  Since DBMs are
omnivorous in that any power can be input or output and if mismatched both!

What that means for lots of complex reasons you can get "spurs" or spurious outputs
that are undesired.

They also suffer from overload, to many and too strong and you get a plethora of signals.

So if you mix 45 with 73 you get 28.  We want that.  However if any of the 28 gets back into
the DBM where it originated it mixes with 45mhz and we get 17mhz. 

With those four signals you get mixtures of those like:


Those are "first order" as they do not involve harmonics.  They will be the strongest
but not always equal strength.

Both inputs can have harmonics like 90mhz and 146mhz and the 34 and 56 coming
out can have harmonics too.  If you add and subtract all the possibles you get an
increasing sea of signals some weak some stronger.  We will not cover the possibles
as the first order ones are the  most troublesome.

If the above is not clear, ask away.

The solution traditionally applied is band pass filters or if it isn't between 28 and 29.9999
the filter strongly attenuates it.  But you need a band pass filter for most every band...
uBitx take the path of below a certain frequency you only need low pass filters and
fewer of them.  And it generally works well especially for 80 though 17M...

But at 20mhz and up the low pass filter passes everything below 30mhz and if you
overdrive the rig slightly you get a spur for the tech window of 28.3 to 28.5 where
the spur is 16.5 to 16.7mhz and there is no filter for that.  What makes this worse
is some radios are very poor at 10M putting out maybe 2W so pushing the audio
to get more invites the problem to be greatly worse.  I got into this as mine was
one that would do more than 15W on 80m and with decreasing power to 1.7W on 10M.
If I forced more audio with RV1 turned all the way up I could get 4W but the 16-17mhz
spur was nearly 13 milliwatts (measured) and well out of the range of permissible. 
Also there is no setting we can safely give that absolutely assures there will
be no problem that is consistent with maximum achievable power.

The above is why the discussion began. 

As a licensed hams here in the USA (likely elsewhere) we are responsible for
signal quality and also not generating signals outside our assigned bands.

There are two solutions one is bandpass the other is high pass filter.
Either way the rig must be modified to allow those and there are side effects.
One side effect is you need extra switching not provided.  The other is any filter
as loss though it and that would further reduce power out.

This is a case where as a new tech or even extra you trade cost for skills
and the skills needed are understanding RF electronics.  There are two
solutions I can suggest, one is get your General or Extra (it worth it) the other
is hope one of us can crank out a solution you can insert into your radio
which means soldering skills and ability to do basic electronics construction.
If you have a club with technical members to help/mentor all the better.


Re: Spurs for Dummies? #ubitx-help


Thanks much.

I do have a multi z tuner kit on the way.  So can the high pass filter for 10 meters be a simple RC or LC for 27 mhz and below. Then placed in the antenna feedline?  Maybe with a toggle switch for bypass? Or am I over simplifying?

Sorry for my ignorance....I'm working on it.

Re: Noob Mic question #ubitx-help

Dexter N Muir

Old Computer motherboards :-) - and other defunct gear. Scratch, scrabble, scrounge, scrooge! The Ham mantra - and eco-friendly: recycle! continuing the mic philosophy.


Re: RF power chain mods and improvements..

Jerry Gaffke

Here's another from that list,  Ft of 360mhz, dissipates over a watt, $0.13/1000, SC-62,  in stock:

Re: KD8CEC Firmware S-Meter usage


i am using it and I do like it. Not implemented everything (not set up S Meter)  but the uBITZ is great on receive. I cannot get any RF power Going through all the checks but not turned up anything yet.
All oscillators must be working as it receives; now going to test the CW tone and MIC circuits.

Will eventually have it for digital modes and WSPR. And as I recently started Arduino I can check and learn more programming techniques.

Re: CAT Control


Thanks Guys,

I'll see if the new drivers help.

73, Dennis

Re: K5BCQ kits in BITX40 #bitx40


Kees mine show as shipped but so far haven't received anything yet.  That's why I was wondering how long the shipment takes. Doug referred to Informed Delivery bit that show only a package coming from Colorado this coming Monday. Saw that your location is in Texas so don't think that is coming from you.
I also thought you would ship them in a normal envelope .


Re: Building homebrew ubitx: Need pre-v3 schematic PDF. Also, source for 45M15 (45 MHz IF) filter?

Bo Barry <bobarr@...>

Ashhar,    I mentioned to Sunil about doing that for his nice cases. ie send me a bunch and save a bunch on postage and I could mail them from here cheaper.

Once the one I ordered comes I can determine US shipping costs to see if it's a good idea.

KD8CEC Firmware S-Meter usage

Kees T

Just curious if many people are using the KD8CEC V1.07 or V1.08 firmware with S-meter support on the Raduino  Using the simple bar graph shown on their various displays and a diode/capacitor for level sensing. 

73 Kees K5BCQ

Re: IFshift

Allen Merrell

What is your opinion of using varactors  in the crystal filter circuit to make it variable.
Allen  Merrell

Re: Different Encoder

Allen Merrell

Thanks, I have been checking around on the optical and find that the 4.7k pullup is what others are using with the Arduino as well as an interrupt routine. I see where I also need to make some pin changes to make it work properly. I am thinking of using a 2560 mega or the mega mini pro because I don't  think their is enough room left on the nano. I want to use the cec firmware on it but modify it to work with the optical encoder and also want to work on a version that will work with the CUI AMT103-V  capacitive  encoder which I think may work pretty good  also.
73's  kn4ud  
Allen  Merrell

Re: K5BCQ kits in BITX40 #bitx40

F1BFU - Fr - 79

Hi Kees

Have you receive my Paypal paiement now ?

73 QRO

Gilles de F1BFU

2018-06-08 18:21 GMT+02:00 Kees T <windy10605@...>:

I update the list every 1-2 days. You can check the status of kits being ordered and shipped at the link below. Sometimes i make several trips to the Post Office if I happen to be going that way.

73 Kees K5BCQ

Check here...


Re: IFshift


ok guys got an update on what i was trying to do. when adjusting the bfo in setup the frequency would change but not the shift on the if. but after pushing ppt button it would correct itself back to what i was listening to and the filter shifted up to the range that i wanted so the fault was me. thanks for the help


Re: IFshift


that sounds idea a good idea Allen, may do that later.  

Re: Different Encoder


I used one of the Chinese 400 ppr optical units in a 40/20/30 receiver I completed last month. I ended up skipping 12 pulses before taking action. This is roughly 32 ppr and performance is the same as when I used a Bourns EM14R0D-R20-L032N part. You will probably have to add pullup resistors to use the 400 ppr unit. I used 4.7K resistors in my receiver.

My processor was a PIC16F1719 for that receiver so I can't show  any code that would work in an Arduino environment. The PIC is running at 32 MHz and has no problem keeping up with the encoder. I do handle the encoder with an interrupt routine and the well know lookup table method. I.E., static int8_t lookup_table[] = {0,-1,1,0,1,0,0,-1,-1,0,0,1,0,1,-1,0};


Re: CAT Control

Jerry Gaffke

The Nano clone that comes mounted to the stock Raduino board
that comes with the uBitx and Bitx40 from hfsignals has a CH340 chip.

All the $3 Nano clones that folks buy to replace a fried Nano have the CH340 chip.

The original Nano board used an FTDI chip, not the CH340 chip, 
but nobody here coughs up the $20 for that board.

Your FTDI cable should have worked, if connected properly to D0 and D1 for the UART connection.
Must connect the cable's RXD to the Nano's TXD (D0), and the cable's TXD to the Nano's RXD (D1). 
Must also have a ground connection from the cable, and some way to power up the Nano (radio turned on is sufficient).

Under Windows, you need to install a CH340 driver to use the clone Nano's.
Under Linux, the needed CH340 driver is usually already there.
Under Mac OS-X, some drivers don't work, there are forum posts about this.
On a  Rasberry Pi, it can be done, my guess is the driver is already there for the typical Linux os install.


On Fri, Jun 8, 2018 at 01:36 am, Tom, wb6b wrote:
Hi Dennis,

See this post.

Hope this helps.

Re: K5BCQ kits in BITX40 #bitx40

Kees T

I update the list every 1-2 days. You can check the status of kits being ordered and shipped at the link below. Sometimes i make several trips to the Post Office if I happen to be going that way.

73 Kees K5BCQ

Check here...


Re: Spurs for Dummies? #ubitx-help

iz oos

I'll keep my summary very short: do all the mods you like but make a high pass filter to cut the frequencies below 28mhz. Adding a tuner will also help. That's all folks.

Il 08/giu/2018 16:19, <davedt1e@...> ha scritto:
I've been following the discussion on spurs, but not sure exactly what it all means in practical terms.  I'm still a tech so 10 meters is of some importance to me.  So far, it's my understanding that this effects the bands above 20 meters when mic gain mods are added. Is that correct? Specifically I'd like to know what mods I should stay away from.  I was planning to add one of the simple mods involving just a few resistors to increase mic gain.  I'd also like to do one of the simple mods to bring my 10 meter output up to 4 watts or so.  Can I still make these changes and stay in compliance.

It would be very much appreciated If someone could give a short summary of the Spurs issue for us less technical folks.



Re: IFshift

Allen Merrell

This may be dumb but could you use varactor  diodes in the filter circuit and vary the voltage to them to change the capacity in the circuit to vary the band width. The Electraft K1 uses this type of adjustable filter  routine. Years ago I copied  it and used it in a TenTec  1340 kit and it worked pretty good. 
73's  kn4ud  
Allen  Merrell

Re: RF power chain mods and improvements..

Ion Petroianu, VA3NOI

As a complete re-design of the RF low level chain I was thinking of trying BiDiAmps based on MMIC (BGA2851 seems a a good candidate as its price is low) and use BFU550AR for Q90 and 2N2222A for predriver and driver stage. Keep the IRF510 as finals.
Add a common gate, switched when needed, JFet preamp for higher bands.
I have some BGA2851 on order and I would try that first, see how it works. They are requiring 5V supply and only take about 7 mA, so the receiving power draw will also improve.
Any thoughts, reccommandations ?