I disagree on the mixer comments. If the toroids are mounted standing up, the
whole mixer should fit in very close to the SBL footprint.
Any ‘5351 circuits you’ve seen with baluns are wasting space and money; they’re
un-necessary. There is little engineering necessary to use it except careful RF
layout. However putting the tiny Si5351, which has fine pitch SMD pins, on the
main board would deter most casual builders. It should be a daughter board,
which leaves open the option for other synthesizers.
Joe
From: Ben Aupperlee
Sent: Wednesday, June 01, 2016 3:06 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: looking for HF1
Hi Joe,
The SBL mixer takes less then 1 by 2cm space where the homebrew will do with 6
to 8 cm², and so the solution with space for both cases takes 6 to 8. And my
idea was first to reduce the size of the board.
Using the si5351 requires carefull engenering, so lets do this. I guess this
means using 3 baluns close to the chip and coax cables to the mixers, and some
load resistors to match impedances. However, can this chip drive diode ring
mixers ? It would solve the adressing problems and the space problems
And what for the SMD. If special taskforce will manufacturer those smd
amplifiers, the rest on the motherboard can be wired parts. There are not many
candidates left for SMD, so this should be no problem.
In the mean time I will draw the schematic to use mixer and amplifier modules
and the si5351 chip. This wil result in a lot smaller drawing.
Regards Ben (in Turkije)
-------- Origineel bericht --------
Van:Joe Rocci
Verzonden:Wed, 01 Jun 2016 21:00:44 +0300
Aan:minima@xxxxxxxxxxxxx
Onderwerp:[minima] Re: looking for HF1
Ben
I’m not suggesting that the mixer is a separate module. I’m suggesting laying
out the main PCB so an SBL mixer or the homebrew mixer could occupy the same
board space; you build one or the other.
The Si5351 crosstalk is largely dependent on the board layout; I haven’t seen a
board yet that treats that properly. You can get it down in the 70-80 dB range
with careful design, but there’s a residual amount in the chip that will always
be there and it will be a function of the signal frequencies. Unless you’re
building a contest-grade radio, I don’t think this has to be a show stopper.
I still don’t think an SMD incarnation would fly well with a broad audience,
but I’m personally pretty agnostic on that.
From: Ben Aupperlee
Sent: Wednesday, June 01, 2016 1:49 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: looking for HF1
Hi Joe,
Acedamic or not, i thank you for your input. Designing anything meaning making
a lot of compromises, and it start with knowing all the pro's and con's.
A PCB using AND the handmade mixer AND the prefab one taking more realestate on
the PCB thaN less, and the idea was getting the PCB smaller.
Using 3 coax wires to land the mixer signal does make the PCB a lot smaller,
but it shifts the problem to another PCB. Additional we create a new problem as
coax lines are prone to problems, like broken inner cores and ground shortages,
but, if this is the choosen solution, it solves the size problems.
If we will use prefab amplifiers with SM devices, made by a special taskforce,
nobody would need to touch the SM devices. The main PCB would be using 400V
capacitors, Xtals and 6mm coils, but there are almost no places for SM left, so
this cannot be a problem.
And about the si5351, if somebody would find a solution for the crosstalk, it
would solve the adressing problems on the bus.
Regards Ben PA9B (in Turkije)
-------- Origineel bericht --------
Van:Joe Rocci
Verzonden:Wed, 01 Jun 2016 20:09:05 +0300
Aan:minima@xxxxxxxxxxxxx
Onderwerp:[minima] Re: looking for HF1
Ben
I’m not currently building this, so my thoughts might be somewhat academic.
However, I suggest drawing the schematic and laying out the main board so both
options are available; ie, packaged mixer vs discrete mixer and on-board xtal
oscillator vs Sixxxx. Here, Sixxxx means Si570 or Si5351, whichever is
preferred. The ‘5351 has the advantage of 3 oscillators in one package and the
disadvantage of numerous crosstalk spurious and higher phase noise. However, if
you just provide inputs for external synthesizers, this could be an external
board option. I’m personally fine (actually happy) with SMD parts, but I think
the broader population of builders would prefer leaded components.
Joe
W3JDR
From: Ben Aupperlee
Sent: Wednesday, June 01, 2016 12:37 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: looking for HF1
Hello Ashhar,
I have redrawn the analog part of the schematic of the HF1 (using paint.exe),
and as there was a very clear and strict copy right notice, i am sending you
this drawing so you could see your own text and answere two questions, first
what is that diode on top of amp 1 doing there, and second, L9, I presume it to
be around 250 to 300nH.
Furthere, there is a discussion about some changes in the population of the
board, here my point of view in temp.HTM
REGARDS Ben PA9B (in Turkije)
