Re: Tuner? Well Sure!

Ashhar Farhan

Hfsignals is an enterprise model that is radical. Instead of building more into hfsignala, i would encourage members to try something similar in their own countries and neighbourhoods. Ham radio is small enough a market to not attract big players.
 Low volume, low cost production units are easily organized with small communities. There are smd pick and place machines like th T220 available for a few thousand dollars. Mouser and digikey ship any amount of compoments from around the world for a few dollars. Makers, homebrewers need to grasp this moment and create value.
So, take the plunge!
Have a great 2018, all. Here is hoping for a better world, f.

On 30 Dec 2017 9:04 pm, "Lawrence Galea" <9h1avlaw@...> wrote:
You can count me in.
A 160M addition would encourage more operators to try this band which is also my favourite.

While at it, would it be possible to include 630M? 
Although I am not sure that the μbitx could be persuaded to tx down there with an additional LPF/BPF it would make more operators try the band.

Couple of quotes from emails.

"I actually changed the lowest frequency to 100000L. I want to see if 2200M will work, also. My antenna will never tune to these frequencies, but I want to see if I can hear anything.... KG5PRT"

"Group, With a filter front end and a small preamp I was able to hear a NDB beacon at 209.00KHz with my Ubitx. the readout read something like 2.09.059...this was a stock UBitx...Hope this helps! Mike WA3O "

So it may be feasible.

Thanks and regards

On Sat, Dec 30, 2017 at 9:30 AM, K9HZ <bill@...> wrote:

MFJ.  Huh. Glad to see them using science for a change.


I’m a little old school when it comes to RF design, and particularly with matching circuits like a tuner.  The best tuners I’ve ever owned were military tuners… specifically the old Collins 601 and the Harris RF-2601 devices.  If you are a study of these devices you know that the control circuits for the tuners operated essentially transform space with phase and amplitude information to effectively minimize SWR by determining the right transform to make the input see a purely resistive load.  Is that hard to do?  Nope.  You just have to think in a different coordinate system.  Rather than go into several pages of background here, for those interested… there is a wonderful and complete chapter on this very subject in Sabin & Schoenike’s book “Single Sideband Systems and Circuits”, Chapter 16.  This book is a must for the serious RF designer.  You can get it off Amazon.  Other chapters in the book will answer questions like why you don’t see grounded gate power amplifiers (a recent topic here), and why the very best IMD and linearity in an RF amplifier comes from a tube design in grounded screen configuration (common in broadcast transmitters… the cathode is at minus screen potential!).  Yikes!


I’ll put together a paper on the various loads the tuner will match once I have all of the calculations done.  Off the top of my head, it should match real impedances of 2ohms-10Kohms and reactances of +/-8Kohms.  I’ve configured the capacitor bank to sit on either side of the inductor to complete the entire transform space (read that work for those really low impedance antennas that are usually not covered by antenna tuners).


The hardware for me is a breeze… what is not so easy for me is figuring out the Raduino side… for display and setting… like Power, SWR, Bypass, frequency for memories, etc.  I may just build in all these things and ask someone else who is more familiar with the uBITx code to help out.  I have decided to make the tuner an I2C device though…so that should help with the communications.  I originally was gonna use RS232 (makes it work with a lot of other radios then too… and even stand-alone) I2C is better for integration.


I should have the hardware drawings dome tomorrow…



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email:  bill@...


From: [] On Behalf Of Gordon Gibby
Sent: Friday, December 29, 2017 6:37 PM
Subject: Re: [BITX20] Tuner? Well Sure!


If you guys can come up with something that works, it might provide a chance for Asher to provide employment for many many more people.


Remember the most recent MFJ products measure impedance and use smith chart type calculations to predict the solution in jump to it quicker.   



But that is not at all beyond the capabilities of many on this forum.


Sent from my iPhone

On Dec 29, 2017, at 19:25, bill richardson <ng1p.bill@...> wrote:

I have been wondering about an internal tuner for my uBitx and/or my BITX40’s. This sounds great please count me in on one.. love to see enough inductance to work on 160m also maybe a mod a future design.

thanks Bill ng1p

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