Yet another correction, I should just go back to bed:
Both the 6db and 3db pads are trying to terminate the oscillator and mixer with 50 ohms,
but the 6db pad is doing a better job of it.
This is at the expense providing half the power to the mixer that the 3db pad could.
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Show quoted text
On Tue, Dec 17, 2019 at 11:49 AM, Jerry Gaffke wrote:
Though the 6dB pad does a better job of terminating that mixer port with 50 ohms,
this prevents unwanted mixer products coming out of the local oscillator port from
reflecting back into the mixer to create additional havoc.
Either one of those pads is terminating the Si5351 with 50 ohms,
|
I think I would have gone for the power in the sine wave that's under those harmonics and divided the 0.8 Vpk by sqrt(2) to get the power of the fundamental.
FWIW and regarding appropriate loading of the Si5351, in this case regarding cross-talk, here's a tidbit I saved from the list a year ago:
September 6, 2018
Here¡¯s a bit of info from
Allison KB1GMX on cross-talk between the outputs of the Si5351a¡¯s channels
which could be an issue if you use one for BFO and one for LO or similar. A
possible cure is to drive higher than 50 ? impedances with the outputs:
I also did the measurement with higher than 50 ohm load and
got?
remarkably better result.
Hint:? drive the load using a 74LVT04 or one of the
friends of that part
or any cmos buffer.??The output is loaded with CMOS
gate and the?
CMOS inverter can be loaded heavier.
And AB7VF said: Read somewhere a test that suggested better
results with 80 ohms rather than the spec-ed 50. Jim 73, Nick - WA5BDU
On Tue, Dec 17, 2019 at 11:23 AM Michael Maiorana < zfreak@...> wrote: I'm just looking for a sanity check (please).
Square wave output from an Si5351 is 3.2V p-p unloaded. Into a 50 ohm resistive load it drops to 1.6V p-p. Average voltage of a square wave is 1/2 p-p value, so Vavg is 0.8V. Power into the resistor (assuming a pure square wave) is (0.8V)^2/50 or 12.8mw. Converting to dBm 10*(Log(12.8/1)) = 11dBm.
11dBm is more than enough to meet the 7dBm drive requirements of a diode ring mixer. However, I'm reading conflicting info on the Si5351's ability to directly drive a diode ring mixer.
Any advice or guidance will be greatly appreciated.
These little Si5351 demo boards from Ebay are amazing for the measly $3.50 that they cost. They have onboard linear LDO regulator and logic level converters so you can drive them direct from an Arduino running at 5V. 4 wires connected to an Uno and some sample code and I was making clocks in less than 10 minutes. What an age we live in!
Mike M. KU4QO
|
A couple edits are required here:
< With capacitive coupling, the Si5351 is? effectively driving your?50 ohm load into 3.3/2=1.65 volts,
> which reduces the currents by half.
> With capacitive coupling, the Si5351 is driving your?50 ohm load with a square wave centered on ground,
> which reduces the currents by half from what they would be without capacitive couplig.
< When a mixer says it wants 7 dBm, I believe that's defined as a source that can
< drive an 11 dBm sine wave into a 50 ohm resistive load,
> When a mixer says it wants 7 dBm, I believe that's defined as a source that can
> drive an 7 dBm sine wave into a 50 ohm resistive load,
Ryan's 3dB pad is probably a better choice than the 6dB pad typically used
on a diode ring mixer if the 6dB pad is not giving the mixer the required 7dBm of power.
Though the 6dB pad does a better job of terminating that mixer port with 50 ohms,
this prevents unwanted mixer products coming out of the local oscillator port from
reflecting back into the mixer to create additional havoc.
Either one of those pads is terminating the Si5351 with 50 ohms,
I've been assuming that the Si5351 is better off with an easier load.
Jerry
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Show quoted text
On Tue, Dec 17, 2019 at 10:19 AM, Jerry Gaffke wrote:
Mike,
I haven't made any such measurements, so you're ahead of me on that.
I have heard in other forums that crosstalk and perhaps other forms of distortion
creep in as the Si5351 output buffers get loaded up beyond a few ma.
With capacitive coupling, the Si5351 is? effectively driving your
50 ohm load into 3.3/2=1.65 volts, which reduces the currents by half.
So if you see 1.6v pk-pk, that's 0.8v/50ohms=16ma, which is not just too far
from the programmable 8ma max for the output buffers of AN619.
But those CMOS buffers are working awfully hard.
The datasheet says that the Si5351 has an output impedance of 50 ohms.
So the hypothetical 3.3v square wave voltage source inside the Si5351 is driving
50 ohms internal plus your 50 ohm load.? So a 1.6v square wave makes perfect sense.
I agree, if you are seeing a 1.6v pk-pk square wave into 50 ohms, then that is 11 dBm.
Some of that energy is in the harmonics, but we're in the correct ballpark.
When a mixer says it wants 7 dBm, I believe that's defined as a source that can
drive an 11 dBm sine wave into a 50 ohm resistive load, even though the non-linear
diodes will make that waveform very un-sine-like in both voltage and current.?
Whether a diode ring mixer is better off with?a square wave is perhaps up for debate,
There is only one pin for the 3.3v rail to power the output buffers on the Si5351,
so with two or three outputs loaded up like that you may get worse results.
Your results justify the uBitx approach of driving a resistive pad directly from
an Si5351, and the uBitx does seem to work well enough.? Though it has its birdies.??
Jerry, KE7ER
|
Mike,
I haven't made any such measurements, so you're ahead of me on that.
I have heard in other forums that crosstalk and perhaps other forms of distortion
creep in as the Si5351 output buffers get loaded up beyond a few ma.
With capacitive coupling, the Si5351 is? effectively driving your
50 ohm load into 3.3/2=1.65 volts, which reduces the currents by half.
So if you see 1.6v pk-pk, that's 0.8v/50ohms=16ma, which is not just too far
from the programmable 8ma max for the output buffers of AN619.
But those CMOS buffers are working awfully hard.
The datasheet says that the Si5351 has an output impedance of 50 ohms.
So the hypothetical 3.3v square wave voltage source inside the Si5351 is driving
50 ohms internal plus your 50 ohm load.? So a 1.6v square wave makes perfect sense.
I agree, if you are seeing a 1.6v pk-pk square wave into 50 ohms, then that is 11 dBm.
Some of that energy is in the harmonics, but we're in the correct ballpark.
When a mixer says it wants 7 dBm, I believe that's defined as a source that can
drive an 11 dBm sine wave into a 50 ohm resistive load, even though the non-linear
diodes will make that waveform very un-sine-like in both voltage and current.?
Whether a diode ring mixer is better off with?a square wave is perhaps up for debate,
There is only one pin for the 3.3v rail to power the output buffers on the Si5351,
so with two or three outputs loaded up like that you may get worse results.
Your results justify the uBitx approach of driving a resistive pad directly from
an Si5351, and the uBitx does seem to work well enough.? Though it has its birdies.??
Jerry, KE7ER
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Show quoted text
On Tue, Dec 17, 2019 at 09:23 AM, Michael Maiorana wrote:
I'm just looking for a sanity check (please).
?
Square wave output from an Si5351 is 3.2V p-p unloaded. Into a 50 ohm resistive load it drops to 1.6V p-p. Average voltage of a square wave is 1/2 p-p value, so Vavg is 0.8V. Power into the resistor (assuming a pure square wave) is (0.8V)^2/50 or 12.8mw. Converting to dBm 10*(Log(12.8/1)) = 11dBm.
?
11dBm is more than enough to meet the 7dBm drive requirements of a diode ring mixer. However, I'm reading conflicting info on the Si5351's ability to directly drive a diode ring mixer.
?
Any advice or guidance will be greatly appreciated.
?
These little Si5351 demo boards from Ebay are amazing for the measly $3.50 that they cost. They have onboard linear LDO regulator and logic level converters so you can drive them direct from an Arduino running at 5V. 4 wires connected to an Uno and some sample code and I was making clocks in less than 10 minutes. What an age we live in!
?
Mike M.
KU4QO
|
When building the DC40, Robin AC7LX recommended a 3db pad, and I implemented that. Works great. I wrote up my pad here:
?
There's info for doing your own using parts on hand :)?
On Tue, Dec 17, 2019 at 9:23 AM Michael Maiorana < zfreak@...> wrote: I'm just looking for a sanity check (please).
Square wave output from an Si5351 is 3.2V p-p unloaded. Into a 50 ohm resistive load it drops to 1.6V p-p. Average voltage of a square wave is 1/2 p-p value, so Vavg is 0.8V. Power into the resistor (assuming a pure square wave) is (0.8V)^2/50 or 12.8mw. Converting to dBm 10*(Log(12.8/1)) = 11dBm.
11dBm is more than enough to meet the 7dBm drive requirements of a diode ring mixer. However, I'm reading conflicting info on the Si5351's ability to directly drive a diode ring mixer.
Any advice or guidance will be greatly appreciated.
These little Si5351 demo boards from Ebay are amazing for the measly $3.50 that they cost. They have onboard linear LDO regulator and logic level converters so you can drive them direct from an Arduino running at 5V. 4 wires connected to an Uno and some sample code and I was making clocks in less than 10 minutes. What an age we live in!
Mike M. KU4QO
-- Ryan Flowers W7RLF
https://miscdotgeek.com
|
I'm just looking for a sanity check (please).
Square wave output from an Si5351 is 3.2V p-p unloaded. Into a 50 ohm resistive load it drops to 1.6V p-p. Average voltage of a square wave is 1/2 p-p value, so Vavg is 0.8V. Power into the resistor (assuming a pure square wave) is (0.8V)^2/50 or 12.8mw. Converting to dBm 10*(Log(12.8/1)) = 11dBm.
11dBm is more than enough to meet the 7dBm drive requirements of a diode ring mixer. However, I'm reading conflicting info on the Si5351's ability to directly drive a diode ring mixer.
Any advice or guidance will be greatly appreciated.
These little Si5351 demo boards from Ebay are amazing for the measly $3.50 that they cost. They have onboard linear LDO regulator and logic level converters so you can drive them direct from an Arduino running at 5V. 4 wires connected to an Uno and some sample code and I was making clocks in less than 10 minutes. What an age we live in!
Mike M. KU4QO
|
Re: Varactor Diode C Measurement
Hi all
See a number of diode measurements here centering around a lot of LED measurements.
73 Hans G0UPL? ?
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Re: Plug and Play Receiver
On Sun, Dec 15, 2019 at 11:50 AM, Jerry Gaffke wrote:
Then a bare bones SA612 (with 9v battery, coil+cap for LO, hi-Z phones, wire antenna).
An inductor tuned with a brass screw for the LO is cheap and approachable.
Jerry, Give me a few weeks to work on this, but a simple, modular approach makes a lot of sense for the younger kids, while the joy of assembly might appeal to the older group.? Maybe a few DIP headers with partitioned circuits and a plug board to tie them together.? Making up those plug-in modules from SMD chips and passives could be a project for the oldest members of the group. Howard, n3fel
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Re: 2N2222 Transceiver ala K8IQY
I'm hardly the one to ask, am by no means an RF guru.
Career was spent making QRM with digital stuff.
I'm sure there are plenty of things I have never even considered?
that are involved in making a radio "quiet and clean sounding".?
I suppose one reason we don't see the AD831 in ham gear much is the $17 price for singles from Mouser.
Though you can buy a complete board with SMA's for quite a bit less.
Perhaps your local walmart has it in stock?? ;-)
? ??
The AD831 seems worth trying.
As you say, it saves a buffer if driving the LO from an Si5351.
It burns a watt just sitting still, so it better be doing something that an SA612 doesn't.
This is where we need Howard's modules, busted down into various mixers,
a selection of mmic gain blocks, crystal filters, bandpass filters, audio amps.
Plus a signal generator and step attenuator.
Build up a 2n2xx receiver as per Jim's design.
Swap out the first diode ring mixer with this AD831 and remove some of the original gain, see if it helps or hinders.
Try then try swapping in an SA612 at the second mixer, re-adjust the gain distribution appropriately.
Go from Jim's 3 crystal IF filter to the Norcal version, see how different it sounds.
Jerry, KE7ER
?
On Mon, Dec 16, 2019 at 02:43 PM, Scott McDonald wrote:
Jerry, what would you think about using an AD831 for the first mixer?
?
I have one sitting here but haven¡¯t used it yet, but the numbers quoted ( if I remember why I bought one) are a 3D order IMD of something like +24 dBm at a -10 dBm drive level. ?That might get at the Si5351 issue simply.
?
I should add I know nothing more about it than that little I¡¯ve read?, but I see them starting to pop up in a few interesting projects.
?
Thoughts??
?
Scott Ka9p
Make something good happen!
|
Re: Varactor Diode C Measurement
I have uploaded a couple of pdfs for some diode junction capacitance comparisons that I did several years ago. They are in the K5DW directory. I used whatever I had in the junque box at the time. I only used reverse voltages up to 9 volts because I noticed that above that the capacitance flattened out considerably.
Anyways, use them or ignore them as you?see fit!
Don Wines, K5DW
On Mon, Dec 16, 2019 at 1:42 PM Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote: I'm curious how the 1n4001 compares with purpose built varactor diodes.
Figure 3 here shows it going from about 20 to 5 pf as the reverse voltage goes from 0 to 10 volts.
? ??
Would be interesting to verify that with measurements, trying several different manufacturers.
|
Re: 2N2222 Transceiver ala K8IQY
Jerry, what would you think about using an AD831 for the first mixer?
I have one sitting here but haven¡¯t used it yet, but the numbers quoted ( if I remember why I bought one) are a 3D order IMD of something like +24 dBm at a -10 dBm drive level. ?That might get at the Si5351 issue simply.
I should add I know nothing more about it than that little I¡¯ve read?, but I see them starting to pop up in a few interesting projects.
Thoughts??
Scott Ka9p Make something good happen!
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On Dec 16, 2019, at 3:25 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
?I'm assuming most of what people like about the 2n2xx is due to the receiver front end and IF. Anyone have thoughts about what would happen if the 2'd mixer was moved to an SA612? ? Jerry, KE7ER On Mon, Dec 16, 2019 at 01:10 PM, w8diz wrote:
Very quiet and clean sounding radio.
|
Re: 2n2xx Transceiver R.I.P.
Jerry, Excellent observations. Thank you! Going with a NE5532 for audio like the SW-40+ rigs is a good idea. Should be plenty of gain. Plus, parts are available and inexpensive ($0.88 in single quantities).
I suppose it would be fairly simple to add a pad and amp for each synthesizer output. I'll have to do some reading to see if I can make sense of it on my own. Using a NE612 is another, maybe simpler option.?
I'm trying not to drift too far off the path.?
Mike M.? KU4QO
On Mon, Dec 16, 2019 at 2:36 PM Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote: Mike,
Very cool!
I'm trying to get dangerous with Kicad as well, it's a serious set of tools.
Being retired now, I no longer have access to the schematic editor and PADS PCB
board layout program that I had used for 30 years.
I've got a bunch of motor memory to retrain.
I believe you went with Jim's schematics from 2001:
? ??
That's a compromise, in that he was building to the arbitrary spec
of using only 2n2222's as the active device.
The Norcal schematics of 2008 made a bunch of improvements, and addressed any
issues that had come up between 2001 and 2008.
For example, looks like a much more serious bit of crystal filtering in the IF
? ??
Driving those mixers with 7dB of energy from an si5351 presents a conundrum.
The Si5351 datasheet claims it can drive 50 ohms, but then AN619 shows that
the CMOS outputs can be programmed to a max of 8ma.
The ap note is correct, the Si5351 does not do a very good job driving a 50 ohm load,
and loading it up like that will add to the crosstalk between Si5351 channels.
Those diode ring mixers want to be 50 ohms at all three ports.
With 8ma into 50 ohms, we get something on the order of 5 dBm of power.
The 7 dBm mixers will work at 5 dBm, but we're better off having a 6 dB resistive pad between the
oscillator and the mixer to absorb any unwanted spurious products coming out of the mixer and keep
them from bouncing back into the mixer to produce even more such junk.
And after adding that pad, we have lost roughly 8 dB of dynamic range off the top.
This is what the uBitx does, and it seems to work well enough.
But could do better with a buffer amp between the Si5351 and the resistive pad.
I agree about the audio transformer, there's a reason nobody sells them anymore.
Many of the audio amp IC's can drive 8 ohms directly, and might be cheaper than that transformer.
For a simple audio amp on a CW rig I'd take a look at the SW40+, includes an audio filter for CW.
If driving that amp from a diode ring mixer, you may need to add another audio gain stage up front.
? ??
The SW40+ uses an SA612 as the second mixer, we could patch that into the 2n2xx as well if so inclined.
We don't really need the dynamic range of a diode ring mixer after stripping off any QRM
with the very narrow IF crystal filter.? The SA612 would not need a buffer between it and the Si5351's output,
just a resistive attenuator to bring it down to between 200 and 300 mv into SA612 pin 6,
which has a roughly 10k input impedance.? The 14 dB of gain that the SA612 provides (vs 6 dB of loss
through a diode ring mixer)means either the audio amp or the IF amp can have 20 dB less gain,
not clear to me exactly how that extra gain should be distributed.
I'd leave the diode ring mixer up front of the IF alone, as that is what will make this better than all the SA612 rigs.
This old forgotten Philips ap note is a gold mine for those trying to understand the innards of the SA612:
? ??
Here's some history that conflicts slightly with that short piece on page one of the ap note:
? ??
Jerry, KE7ER
On Mon, Dec 16, 2019 at 08:12 AM, Michael Maiorana wrote:
Here's what I have so far. Hopefully this will be legible as an inline image. I'm a Kicad noob, so be gentle :)
I used Jim's original design with the roll-your-own mixers. This is the receiver only. There is no VFO, transmit mute or audio amp. My issue with the discrete audio amp as designed by Jim is that hard to find audio transformer. I'm not sure if I should add audio amplification to this board or just do the audio functions on a different board. Thoughts?
?
I plan to use an Si5351 ebay board and an arduino uno as a VFO/LO to get it running (commonly available code), then possibly design?a simple, low power vfo/display.
?
My intention is to use mostly surface mount parts (0805 size resistors and caps, SOT-23 size transistors and diodes).
?
Opinions are welcome!
?
Best regards,
Mike M. KU4QO
?
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Re: Plug and Play Receiver
Most anything that resonates with your cap, assuming you have a bunch of wire out the window for an antenna.
The coil becomes critical when there is no wire antenna, then the bigger the ferrite rod is the more signal you scoop up,
I assume via magnetic coupling, no longer thinking microvolts into a 50 ohm antenna connector.
Back about 55 years ago, I found toilet paper rolls to make fine inductor cores for AM radio projects of this sort
Jerry, KE7ER
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On Mon, Dec 16, 2019 at 01:39 PM, Michael Maiorana wrote:
Jerry,
That looks like a really fun and quick project. I've got plenty of air variable caps. Any idea what kind of coil to build if you don't have a ferrite rod for a core?
?
Adding this to my list of projects to play with!
Thanks
Mike M.? KU4QO
|
Re: Varactor Diode C Measurement
I used a 1N4007 in my NC-40 build. More range than the specified varactor. The PIN structure helps. 73, Gary? WB6OGD?
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On Dec 16, 2019, at 1:20 PM, Eric KE6US <eric.csuf@...> wrote:
?
Virtually ANY diode will work, some better than
others. I have a number of projects where I used a red LED as a
varactor. I usually got from low-teens pf to ~50 pf. Smaller
ones tended to be better than larger ones. Red was better than
other colors which have a much more limited range. The only
problem I found was light sensitivity. You have to block the
lens (tape, dipped in paint, whatever) or it will pick up 60
cycle variations from lighting and other weird effects.
Didn't have much luck with gp diodes. They work.
Just not as much range as red LEDs. I've used them since about
2005. A couple are still plugging away and work fine.
Eric KE6US
On 12/16/2019 11:42 AM, Jerry Gaffke
via Groups.Io wrote:
I'm curious how the
1n4001 compares with purpose built varactor diodes.
Figure 3 here shows it going from about 20 to 5 pf as the reverse
voltage goes from 0 to 10 volts.
? ??
Would be interesting to verify that with measurements, trying
several different manufacturers.
|
Re: 2N2222 Transceiver ala K8IQY
Another thought:? G0UPL and KD1JV among others are using cheap BS170's in parallel for?
a very efficient rf power amp in class E (or there-abouts).
Would be interesting to try building a class E final using BS170's in push-pull,
driven from 74ACxx gates via capacitive coupling, about 3v of DC bias at the gates.
Definitely beyond my level of competence, I might accidentally learn something.
The Peter Principle at its best.
G0UPL has some good notes on class E in his docs for the QCX.
Any thoughts on the performance of Jim's design with the 3 crystal filter vs the Norcal 2n2?
Jerry, KE7ER
|
Re: Plug and Play Receiver
Jerry, That looks like a really fun and quick project. I've got plenty of air variable caps. Any idea what kind of coil to build if you don't have a ferrite rod for a core?
Adding this to my list of projects to play with! Thanks Mike M.? KU4QO
On Mon, Dec 16, 2019 at 2:56 PM Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote: Here's an unexpected curiosity for those with way too many LM386's in the junk box.
A single chip regenerative receiver.? ?
Using only an LM386:
? ??
Jerry, KE7ER
|
Re: 2N2222 Transceiver ala K8IQY
I'm assuming most of what people like about the 2n2xx is due to the receiver front end and IF.
Anyone have thoughts about what would happen if the 2'd mixer was moved to an SA612?
?
Jerry, KE7ER
toggle quoted message
Show quoted text
On Mon, Dec 16, 2019 at 01:10 PM, w8diz wrote:
Very quiet and clean sounding radio.
|
Re: Varactor Diode C Measurement
Virtually ANY diode will work, some better than
others. I have a number of projects where I used a red LED as a
varactor. I usually got from low-teens pf to ~50 pf. Smaller
ones tended to be better than larger ones. Red was better than
other colors which have a much more limited range. The only
problem I found was light sensitivity. You have to block the
lens (tape, dipped in paint, whatever) or it will pick up 60
cycle variations from lighting and other weird effects.
Didn't have much luck with gp diodes. They work.
Just not as much range as red LEDs. I've used them since about
2005. A couple are still plugging away and work fine.
Eric KE6US
On 12/16/2019 11:42 AM, Jerry Gaffke
via Groups.Io wrote:
toggle quoted message
Show quoted text
I'm curious how the
1n4001 compares with purpose built varactor diodes.
Figure 3 here shows it going from about 20 to 5 pf as the reverse
voltage goes from 0 to 10 volts.
? ??
Would be interesting to verify that with measurements, trying
several different manufacturers.
|
2N2222 Transceiver ala K8IQY
Hi All,
Been reading the mail on Jim's 2N2222 rigs and wanting to create PCBs (for personal use only).
I'm thinking of doing one myself as I remember using one of Jims rigs (built by an FPqrp member)
Very quiet and clean sounding radio.
First, I will need to read all of Jim's docs to find the latest/greatest version of his 2N2222 rigs.
Been a looong time since I did a project for myself that did not include kitsandparts.com :)
-Diz, W8DIZ ...anticipating the fun
Hmmmmm....I have over 10K pieces of surplus MPSH10 transistors....(Jim - any thoughts?)
|
Re: 2n2xx Transceiver R.I.P.
I take that back.
Jim's schematics on? ?
still show a three crystal filter with an apparent last update of 2013
The Norcal thing is its own animal.
Jerry, KE7ER
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On Mon, Dec 16, 2019 at 11:36 AM, Jerry Gaffke wrote:
I believe you went with Jim's schematics from 2001:
|
Nick Kennedy
Don K5DW