I also built the Minima some years ago in a receive-only version (with
the KISS mixer) as my first serious homebrew project.
The Minima receiver was awesome with very nice sound! Sensitivity was a bit compromised, but that was in comparison with a commercial direct sampling SDR and only became apparent at my remote site where there is much less man-made-noise (at home the antenna noise was always much higher than the internal noise of the Minima).
I still use the discrete audio amp circuit of the original Minima in my homebrew SDRs, because the noise is so low.
Also, I believe that LO phase noise problems are overrated in homebrewing, as we can experience when we use the Si5351 which has higher phase noise that the Si570, but nonetheless gives very nice performance (however I use it in IQ-SDRs where the phase noise is divided by 4 by the QSD).
Have fun, 73 de Frank DD4WH
Am 02.04.2017 um 11:23 schrieb Ashhar Farhan:
As receivers go, the minima receiver with the kiss mixer is the best receiver i have ever. the audio is sparkling with so little gain in the rf path. it is only in the transmit side that we have these problems.
A VCO running at 10 MHz might drip about 600 Hz in a minute, for simplicity's sake. That is about 10 Hz per second. This is easily fixed by the slow (and simple) huff and puff. A VCO at 20 MHz might drift over 2 2 KHz per minute, that is more than 30 Hz per second. This too can be fixed if the HnP sampling rate is increased to 50 Hz. the lock points are spaced out over 50 Hz, it will still be stable enough for PSK31, though not for any of the JT modes.
On Sun, Apr 2, 2017 at 12:34 PM, Will Kimber <zl1tao@xxxxxxx <mailto:zl1tao@xxxxxxx>> wrote:
Ashhar or anybody else that has tried it,
Is the KISS mixer in the minima suitable for receive only. I'm
looking at G.C. Rx only?
Would the KISS mixer be O.K for use with the uBitx, again G.C. Rx
On 03/31/2017 07:54 PM, Ashhar Farhan wrote:
It is trivial to move the IF of the uBitx to 55 Mhz. Just a turn
of two off and we will be in business.
About the Minima, there are two ways to get rid of the local
1. replace the kiss mixer with the regular H mode mixer. It takes
two transformers and an FST3253. The local oscillator will be low
enough that it gets stripped out.
2. The local oscillator goes from 22 Mhz to 34 MHz when minima
tunes from 2 MHz to 14 MHz. Between 14 Mhz and 30 MHz, instead of
the low pass filter, use a doubly tuned band-pass filter with 365
There is another better, but of course, more elaborate scheme
that you can try it. It is as follows:
1. Move the IF to 12 MHz. Use band pass filters above 7 MHz for
every band. This will give you a contest grade rig. Add linrad in
On Fri, Mar 31, 2017 at 9:39 AM, Robert Toegel
<rjtoegel@xxxxxxxxx <mailto:rjtoegel@xxxxxxxxx>> wrote:
That's where I was playing with putting a crystal across the
output of the mixer to ground so the series resonance would
"suck out" the local oscillator leakage. I noticed this
years ago when I put a crystal across the antenna input of a
receiver just to see what would happen and a station at that
frequency nearly disappeared. Pardon the pun but I had mixed
results so far.
On Thu, Mar 30, 2017 at 1:46 PM Jerry Gaffke
If anybody's thinking about building the uBitx, check
this thread: https://groups.io/g/BITX20/message/23261
Not a big hit, and I'm not aware of any other issues
being reported yet.
I previously said this about the old minima: "can have
trouble with clean transmissions due to mixer products."
As Farhan reports on
the issue is actually one of leakage through the KISS
mixer of the local oscillator.
On Wed, 3/29/17, Jerry Gaffke <jgaffke@xxxxxxxxx
Subject: Re: [minima] Fwd: Finally getting around to
building my Minima...
To: minima@xxxxxxxxxxxxx <mailto:minima@xxxxxxxxxxxxx>
Date: Wednesday, March 29, 2017, 8:16 PM
Most of the discussion is happening
now at https://groups.io/g/BITX20
Minima can work, but has a few issues regarding how
reproducible that front end filter is, also can have trouble
with clean transmissions due to mixer products.
Ashhar moved on to a double conversion scheme with the
<//www.freelists.org/post/minima/Updated-HF1> in Feb
This summer he started shipping a stuffed board along the
lines of the original Bitx design for $59: hfsigs.com
And now he has described the uBitx, which is an improved
If I were scratch building today, I'd look first at the
The uBitx may (or may not) eventually come out as a built
board from hfsigs.com <http://hfsigs.com>
On Wed, 3/29/17, Mark Pilant <mark@xxxxxxxxx
Subject: [minima] Fwd: Finally getting around to building
To: "minima@xxxxxxxxxxxxx <mailto:minima@xxxxxxxxxxxxx>"
Date: Wednesday, March 29, 2017, 5:42 PM
Well, it seems to be quiet around