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.
- f
On Sun, Apr 2, 2017 at 12:34 PM, Will Kimber <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 only?
Cheers,
Will
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 oscillator
spur.
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 pf gang.
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 the backend.
- f
On Fri, Mar 31, 2017 at 9:39 AM, Robert Toegel <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.
Bob WA2EGP
On Thu, Mar 30, 2017 at 1:46 PM Jerry Gaffke <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
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 http://www.phonestack.com/farhan/ubitx/ubitx.html
the issue is actually one of leakage through the KISS mixer of the local
oscillator.
Jerry, KE7ER
--------------------------------------------
On Wed, 3/29/17, Jerry Gaffke <jgaffke@xxxxxxxxx> wrote:
Subject: Re: [minima] Fwd: Finally getting around to building my
Minima...
To: 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
HF_1: //www.freelists.org/post/minima/Updated-HF1 in Feb
of 2016.
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
HF_1: http://www.phonestack.com/farhan/ubitx/ubitx.html
If I were scratch building today, I'd look first at the
uBitx
The uBitx may (or may not) eventually come out as a built
board from hfsigs.com
Jerry, KE7ER
--------------------------------------------
On Wed, 3/29/17, Mark Pilant <mark@xxxxxxxxx>
wrote:
Subject: [minima] Fwd: Finally getting around to building
my Minima...
To: "minima@xxxxxxxxxxxxx"
<minima@xxxxxxxxxxxxx>
Date: Wednesday, March 29, 2017, 5:42 PM
Well, it seems to be quiet around
here.. :-)
