Greetings. I am inspired, kindly let me now, where can I get total Kit of
Minima in India?.. 73. This is VU2VIZ
On Thu, Mar 30, 2017 at 10:36 AM, FreeLists Mailing List Manager <
ecartis@xxxxxxxxxxxxx> wrote:
minima Digest Wed, 29 Mar 2017 Volume: 04 Issue: 005
In This Issue:
[minima] Fwd: Finally getting around to building my
Minima..
[minima] Re: Fwd: Finally getting around to building my
Mini
[minima] Re: Fwd: Finally getting around to building my
Mini
----------------------------------------------------------------------
Date: Wed, 29 Mar 2017 20:42:48 -0400
From: Mark Pilant <mark@xxxxxxxxx>
Subject: [minima] Fwd: Finally getting around to building my Minima...
Well, it seems to be quiet around here.. :-)
I've finally managed to make some time to build my own Minima. My plan
is to make is as a series of modules so I can try out different some of
the various suggestions posted here. Plus, I got a good deal on a bunch
of RG-174 and SMA connectors :-)
One thing which delayed things a bit was wanting (and to a lesser extent
needing) to build a scalar network analyzer to check out the various
modules. I built my own (hardware and software) before I found out about
the PHSNA. Oh well, timing is everything :-) One thing I added early on
was a color TFT display to be able to see all the "pretty" graphs :-P
So with the SNA built...
I was able to sort through my pile of crystals and build the crystal
filter. It worked out pretty well. It has a 2.555KHz bandwidth, centered
on 19.994MHz.
Next was the front-end filters. After a bit of a learning curve winding
toroids, I was able to get the filters constructed. I used my SNA to
check out the actual filters before wiring up the relays; to make sure
they actually worked as expected. I need to adjust the 15MHz LP filter
as it is falling off a bit too soon.
After I completed the circuit, I encountered one "big" problem. When the
30MHz LP/20MHz notch filter was used, the shape looked OK, but the signal
was about 40dB lower than it should have been. After some careful poking
around with my scope, I found the problem. The relay I mounted on a
18-pin DIP "MePAD" (cut down to 10 pins) had a very marginal trace between
the pin contact and the solder pad (to connect to the pin). A little
solder "bridge" cured this problem and the signal was right at the expected
level.
The other "problem" I need to fix is what appears to be a shorted relay
driver transistor. When I hook up +12VDC, the relays engage; regardless
of the voltage on the base of Q23 (float, ground, or +3-5VDC). I don't
expect this to be too hard to fix.
It turns out I was right. There was a shorted bypass cap, from Q23's
collector to ground. Replacing it with a good bypass cap fixed the
problem.
Next up is the mixer. I'm going to start with the dual FET design, but
because everything is modular, I expect I'll try some other mixer designs
as well.
That's it for now.
73
- Mark N1VQW
------------------------------
From: Mike Malone <kd5kxf@xxxxxxxxx>
Date: Wed, 29 Mar 2017 21:28:57 -0500
Subject: [minima] Re: Fwd: Finally getting around to building my Minima...
That is way cool Mark. We made some boards and I am building some with
friends right after fishing season.
On Wednesday, March 29, 2017, Mark Pilant <mark@xxxxxxxxx> wrote:
Well, it seems to be quiet around here.. :-)centered
I've finally managed to make some time to build my own Minima. My plan
is to make is as a series of modules so I can try out different some of
the various suggestions posted here. Plus, I got a good deal on a bunch
of RG-174 and SMA connectors :-)
One thing which delayed things a bit was wanting (and to a lesser extent
needing) to build a scalar network analyzer to check out the various
modules. I built my own (hardware and software) before I found out about
the PHSNA. Oh well, timing is everything :-) One thing I added early on
was a color TFT display to be able to see all the "pretty" graphs :-P
So with the SNA built...
I was able to sort through my pile of crystals and build the crystal
filter. It worked out pretty well. It has a 2.555KHz bandwidth,
on 19.994MHz.between
Next was the front-end filters. After a bit of a learning curve winding
toroids, I was able to get the filters constructed. I used my SNA to
check out the actual filters before wiring up the relays; to make sure
they actually worked as expected. I need to adjust the 15MHz LP filter
as it is falling off a bit too soon.
After I completed the circuit, I encountered one "big" problem. When the
30MHz LP/20MHz notch filter was used, the shape looked OK, but the signal
was about 40dB lower than it should have been. After some careful poking
around with my scope, I found the problem. The relay I mounted on a
18-pin DIP "MePAD" (cut down to 10 pins) had a very marginal trace
the pin contact and the solder pad (to connect to the pin). A littleexpected
solder "bridge" cured this problem and the signal was right at the
level.
The other "problem" I need to fix is what appears to be a shorted relay
driver transistor. When I hook up +12VDC, the relays engage; regardless
of the voltage on the base of Q23 (float, ground, or +3-5VDC). I don't
expect this to be too hard to fix.
It turns out I was right. There was a shorted bypass cap, from Q23's
collector to ground. Replacing it with a good bypass cap fixed the
problem.
Next up is the mixer. I'm going to start with the dual FET design, but
because everything is modular, I expect I'll try some other mixer designs
as well.
That's it for now.
73
- Mark N1VQW
------------------------------
Date: Thu, 30 Mar 2017 03:16:06 +0000 (UTC)
From: "Jerry Gaffke" <dmarc-noreply@xxxxxxxxxxxxx> (Redacted sender
"jgaffke"
Subject: [minima] Re: Fwd: Finally getting around to building my Minima...
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.. :-)
I've finally managed to make some time to build my own
Minima. My plan
is to make is as a series of modules so I can try out
different some of
the various suggestions posted here. Plus, I got a
good deal on a bunch
of RG-174 and SMA connectors :-)
One thing which delayed things a bit was wanting (and to a
lesser extent
needing) to build a scalar network analyzer to check out the
various
modules. I built my own (hardware and software) before
I found out about
the PHSNA. Oh well, timing is everything :-) One
thing I added early on
was a color TFT display to be able to see all the "pretty"
graphs :-P
So with the SNA built...
I was able to sort through my pile of crystals and build the
crystal
filter. It worked out pretty well. It has a
2.555KHz bandwidth, centered
on 19.994MHz.
Next was the front-end filters. After a bit of a
learning curve winding
toroids, I was able to get the filters constructed. I
used my SNA to
check out the actual filters before wiring up the relays; to
make sure
they actually worked as expected. I need to adjust the
15MHz LP filter
as it is falling off a bit too soon.
After I completed the circuit, I encountered one "big"
problem. When the
30MHz LP/20MHz notch filter was used, the shape looked OK,
but the signal
was about 40dB lower than it should have been. After
some careful poking
around with my scope, I found the problem. The relay I
mounted on a
18-pin DIP "MePAD" (cut down to 10 pins) had a very marginal
trace between
the pin contact and the solder pad (to connect to the
pin). A little
solder "bridge" cured this problem and the signal was right
at the expected
level.
The other "problem" I need to fix is what appears to be a
shorted relay
driver transistor. When I hook up +12VDC, the relays
engage; regardless
of the voltage on the base of Q23 (float, ground, or
+3-5VDC). I don't
expect this to be too hard to fix.
It turns out I was right. There was a shorted bypass
cap, from Q23's
collector to ground. Replacing it with a good bypass
cap fixed the
problem.
Next up is the mixer. I'm going to start with the dual
FET design, but
because everything is modular, I expect I'll try some other
mixer designs
as well.
That's it for now.
73
- Mark N1VQW
------------------------------
End of minima Digest V4 #5
**************************
