New QRP Labs 50W PA for the QCX (and Homebrew, I'm sure)
Hans released this today- $29.50 for a 50W PA that includes filtering and heat sink. It's class C, CW only. Could be a nice addition to a rig during the solar minimum :)? --
Ryan Flowers W7RLF
https://miscdotgeek.com
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Re: Anyone Built the Rose 80?
Correction:? 24-22=2mhz
But you knew that.
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On Thu, Dec 12, 2019 at 06:49 AM, Jerry Gaffke wrote:
The 5'th harmonic of that VFO at 5*4.4=22mhz will mix with the third harmonic
of the 8mhz local oscillator at 3*8=24mhz to give a spur at 24-22=3mhz.?
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Re: 7 MHz Oscillator Ideas
Yes, the capacitance change of a varactor per volt decreases as voltage increases. But remember that the capacitance change has more "worth" at low levels. For example, in a tank with only a varactor for the capacitance (not likely, I know), you'd get the same frequency change going from 20 pF to 10 pF as you got from 200 pF to 100 pF.
In cases where that matters, I've often tried to keep that voltage range up. But as the other poster said, it's important that it be regulated.
73-
Nick, WA5BDU
On Tue, Dec 10, 2019 at 2:52 PM Chuck Carpenter < w5usj@...> wrote: Jerry,
The capacitance beyond 10V changes very little.? The plotted curves by k7qo?in the attached chart show that. The MV209 is similar to the BB910 that I used.
Note too that the curve for the 1N4004 shows very little change beyond about 4-5 V. That curve is typical of junctions from devices like diodes and LEDs and etc. The max C might be more or less at 0V depending on the size of the junction.? But the shape of the curves is about the same.
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: Anyone Built the Rose 80?
Most QRP CW transmitters get by with just the output low pass filter
because the oscillator is working directly at the desired transmit frequency.
There is no mixer to create spurious products.
The only problem is harmonics, and the lowest harmonic is double the desired frequency
and thus easy for the output low pass filter to remove.
A rig with a mixer such as the NE602 at IC5 will have undesired products.
Other than both input frequencies and the sum and difference frequencies,
there will be additional spurs due to harmonics of the input frequencies.
For example, when tuning this rig to 3.6 mhz, the VFO will be at 8-3.6=4.4mhz.
The 5'th harmonic of that VFO at 5*4.4=22mhz will mix with the third harmonic
of the 8mhz local oscillator at 3*8=24mhz to give a spur at 24-22=3mhz.?
That spur is probably 30 or 40 dB down, but still loud enough to make the rig illegal.??
Being lower than the operating frequency, the output low pass filter will have no effect.
The problem with the Rose-80 is that it uses sharply tuned resonant circuits?
at T3 and T5.? On most rigs, T3 and T5 would be broadband,
and there might be a 3.5 to 3.7 mhz bandpass filter (see EMRFD for recipes)
immediately after the mixer at IC5 to remove those nasty spurs.
T3 and T5 are built to be 10.7 mhz IF transformers,
they probably have an internal cap to resonate at 10.7mhz.
The Rose-80 adds an external cap to each to bring the resonant frequency
down into the 80m band.? So removing that external cap is not sufficient
to disable the resonance, T3 and T5 would have to be replaced entirely.
If going to an si5351 vfo, I would remove the mixer at IC5 entirely,
and just drive the final at the desired frequency directly from the si5351 during transmit.
But as I said, the rig is probably just fine as built.
Adjust T3 and T5 to best hit the band slice of interest and leave it be.
Unless you are compelled to tinker and learn, in which case have at it.
Jerry, KE7ER
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On Wed, Dec 11, 2019 at 09:37 PM, Jerry Gaffke wrote:
Most CW transmitters are broadband all the way out through the final.
Being class C, the final creates plenty of harmonics, but the output lowpass filter (L5,L6 in this case)
should be sufficient to clean that up.
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Re: Anyone Built the Rose 80?
John,
Why offline?
Perhaps we can all learn something.
I have no experience with this particular design.
But I don't think you have a layout issue.
Most CW transmitters are broadband all the way out through the final.
Being class C, the final creates plenty of harmonics, but the output lowpass filter (L5,L6 in this case)
should be sufficient to clean that up.
The writeup for the Rose-80 says:
>??Transformers T3 and T5 (Mouser 42IF123) are used to filter unwanted harmonics and spurs. T3 should be adjusted for
>? maximum output at the higher end of the band while T5 should be adjusted at the lower end of the band.
The writeup also says that the VFO operates between 4.3 and 4.4 mhz.?
The gets mixed with 8mhz in the NE602 at IC5, creating an output signal between 8-4.3=3.7mhz and 8-4.4=3.6mhz.
Unfortunately, the NE602 also has some of the 4.3mhz VFO coming through and heading out to the final.
That 4.3mhz is too close to the transmit frequency for the output lowpass filter at L5,L6 to knock out sufficiently.
So the designer added tuned circuits at T3 and T5 around the transmit pre-driver to knock out the VFO.
At least, that's my best guess.
Tuning T5 for the low part of the band and the T3 for the high part would spread the peak out,
but perhaps not evenly enough to meet your expectations.
Are you trying to hit more than a 100khz slice of the 80 meter band with this transmitter?
You may be best off to narrow down the slice you are trying to hit until performance is sufficiently uniform
after tweaking T3 and T5.
If trying to hit 3.5 to 3.6mhz, for example, I'd try peaking T5 for 3.525mhz and T3 for 3.575mhz.
So peak at 25% in from the desired band slice edges, not exactly on them.
Remember, if power varies between 5 and 3 watts out, that's less than half of an S unit.?
The guy at the other end may not even notice.
If I am right and it is just a matter of the VFO sneaking through, one fix would be to move
the VFO above the 8mhz intermediate frequency instead of below.
To tune from 3.5 to 3.6mhz, the vfo would be operating between 11.5 and 11.6mhz.
Doing this would require defeating the tuned circuits at T3 and T5 somehow.
An analog VFO becomes increasingly unstable as you go up in frequency like that,
but one of the many si5351 based VFO's should work quite well.?
Hans (who has checked in here) sells a very nice full featured VFO that could?
be used in lots of different projects, and also works as a general purpose signal generator:
? ??
Me, I'd just live with the loss of 2 Watts at the band slice edges.
Good Luck!
Jerry, KE7ER? ? Flora OR? (hey, not just too far!)
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On Wed, Dec 11, 2019 at 05:56 PM, John Roland wrote:
To make a long story short, I am have a problem with the output power varying a couple watts over the tuning range depending on where I peak the filter (T3 T5).? I built the rig using ugly construction and have tried to improve the layout of the transmitter once but no joy.?? Now that the crummy weather has returned to the PNW, its down off the shelf again and I'm looking at the filter as the culprit.?? I'm thinking I have probably made an error in the assembly of that section but can't see my problem.? If you have any experience with this circuit and could elmer me through this, I'd be very grateful.??
Here's a link to the original article.??
If up to the challenge, please contact me off list.
/John? W7SWB
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Anyone Built the Rose 80?
To make a long story short, I am have a problem with the output power varying a couple watts over the tuning range depending on where I peak the filter (T3 T5).? I built the rig using ugly construction and have tried to improve the layout of the transmitter once but no joy.?? Now that the crummy weather has returned to the PNW, its down off the shelf again and I'm looking at the filter as the culprit.?? I'm thinking I have probably made an error in the assembly of that section but can't see my problem.? If you have any experience with this circuit and could elmer me through this, I'd be very grateful.??
Here's a link to the original article.??
If up to the challenge, please contact me off list.
/John? W7SWB
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Re: What level math is in the RF design books?
As someone who has endured graduate level math...
Don't overthink the math when designing or troubleshooting a radio.?
As someone else commented, high school algebra is almost overkill for the amateur experimenter.? I always thought W7ZOI took it down to the 'basics', but also note there is a lot of 'heavier stuff" as well.? However again, don't get too caught up in the heavier stuff (unless you want to).
There is a guy on YouTube, Charlie Morris, ZL2CTM, who has made video documentations of his many scratch built projects, ranging from a simple DC receiver, to an SDR transceiver.? While he stresses what he is doing is 'not teaching', one thing Charlie does extremely well is break the 'math' down into practical calculations and, he explains his thinking process as he does so.?
So, if you are looking to answer the question of? "what level of math", you might find Charlie's videos extremely enlightening.
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Re: What level math is in the RF design books?
two CR2032 batteries
Roy WA0YMH
On Wed, Dec 11, 2019, 4:31 AM Chuck Carpenter < w5usj@...> wrote: William,
Oooops, That should have been Vrms ?^2
I never could get comfortable with RPN.? I had one of the TI programmables.?That worked good for me for a while.? I loaned it to my son when he was working on his PhD.? He just retired from the workforce.? Still don't have it back!
What sort of battery does the HP-35S use?
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: What level math is in the RF design books?
William,
Oooops, That should have been Vrms ?^2
I never could get comfortable with RPN.? I had one of the TI programmables.?That worked good for me for a while.? I loaned it to my son when he was working on his PhD.? He just retired from the workforce.? Still don't have it back!
What sort of battery does the HP-35S use?
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: What level math is in the RF design books?
Chuck,
Thanks!
I had discovered that a long time ago and was using it in my previous message to illustrate my relative Business Administration degree ignorance of electronic theory. But, coincident with my purchase of the relatively new HP-35S (the retro/nostalgia product unleashed on the market about a decade ago), I entered that calculation and about a dozen others into the memory and am cruising blissfully away, oblivious to the underlying math.
If the batteries crap out, I am toast!
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: 7 MHz Oscillator Ideas
Here's a thought on a minimalist si5351 vfo:
Could turn on a second channel at 600 hz away from the primary channel,
weakly coupled into that primary channel.
This should come through on most receivers as a 600 hz audio tone.
So can tell the user the frequency in morse when requested?
by a button push,?in addition to giving a tick every 25khz.?
The entire vfo could be the size of a penny,
and cost about 200 of them in parts.
Jerry
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On Tue, Dec 10, 2019 at 02:19 PM, Jerry Gaffke wrote:
Maybe have the si5351 stop for 100ms each time it passes through a multiple of 25khz
so you can audibly keep track of where the vfo is.
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Re: 7 MHz Oscillator Ideas
The si5351 is a great part, and only costs $1.
You do need a processor to communicate with the si5351 via its i2c bus,
but a low end msp430 these days is $0.50.
With that, a 25mhz reference crystal, and a couple button switches for up/down, you have a vfo.
Maybe have the si5351 stop for 100ms each time it passes through a multiple of 25khz
so you can audibly keep track of where the vfo is.
Would work fine, assuming you filter out any incoming high frequency RF from the antenna?
that might mix with harmonics of the si5351's square wave.
But part of the attraction of a DC receiver is that it is a very simple analog circuit
that's easy to understand.?
No digital magic.
Jerry
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On Tue, Dec 10, 2019 at 12:05 PM, Jim Pruitt wrote:
Would it be of any value to use a Si5351 module like the Adafruit module ($7 from them or Mouser or Digikey) or a homebrew one like VK3PE makes that is a drop in replacement for the Adafruit
Yes,? the Si5351's are 10 pin smt devices but they are about $2.25 each in small quantities and seem to be used a lot these days or you could buy the Adafruit module that is already soldered for you.? A cheap mechanical encoder could also be used with them.? Yes that does complicate the design by requiring that a PIC chip or Arduino chip or module also be included in the design but I would guess the parts for something like that in a simple DC receiver would be around $25.? Adding a display would drive the cost up and complicate it but is a display really even needed?? I would suspect that there is a way to set the frequency range of the module without using a cpu but I do not know what it is.
Thank you.
Jim Pruitt
WA7DUY
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Re: 7 MHz Oscillator Ideas
It is stable enough because of the use of the crystals.
However, if this was an LC circuit, you definitely want voltage into that pot to be regulated.
The voltage applied to the diode is always some ratio of your unregulated supply,
the ratio being determined by the pot.
This matters even when you set the pot to give the diode 3v.
Jerry
?
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On Tue, Dec 10, 2019 at 12:52 PM, Chuck Carpenter wrote:
The capacitance beyond 10V changes very little.? The plotted curves by k7qo?in the attached chart show that. The MV209 is similar to the BB910 that I used.
Note too that the curve for the 1N4004 shows very little change beyond about 4-5 V. That curve is typical of junctions from devices like diodes and LEDs and etc. The max C might be more or less at 0V depending on the size of the junction.? But the shape of the curves is about the same.
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Re: 7 MHz Oscillator Ideas
Jerry,
The capacitance beyond 10V changes very little.? The plotted curves by k7qo?in the attached chart show that. The MV209 is similar to the BB910 that I used.
Note too that the curve for the 1N4004 shows very little change beyond about 4-5 V. That curve is typical of junctions from devices like diodes and LEDs and etc. The max C might be more or less at 0V depending on the size of the junction.? But the shape of the curves is about the same.
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: 7 MHz Oscillator Ideas
Would it be of any value to use a Si5351 module
like the Adafruit module ($7 from them or Mouser or Digikey) or a
homebrew one like VK3PE makes that is a drop in replacement for
the Adafruit
Yes,? the Si5351's are 10 pin smt devices but they are about $2.25
each in small quantities and seem to be used a lot these days or
you could buy the Adafruit module that is already soldered for
you.? A cheap mechanical encoder could also be used with them.?
Yes that does complicate the design by requiring that a PIC chip
or Arduino chip or module also be included in the design but I
would guess the parts for something like that in a simple DC
receiver would be around $25.? Adding a display would drive the
cost up and complicate it but is a display really even needed?? I
would suspect that there is a way to set the frequency range of
the module without using a cpu but I do not know what it is.
Thank you.
Jim Pruitt
WA7DUY
On 12/10/2019 2:58 AM, Chuck Carpenter
wrote:
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Jerry,
I get about 3 kHz with a pair of crystals on 7MHz using the
"fixture" in the picture.? I measured that with a 10V tuning
range.
The SA612?oscillator is running from the 6V regulator circuit so
the frequency isn't affected by supply voltage changes.
The GQRP Sudden RX kit uses a VFO for tuning.? You could take a
shot at that using those 9mm cans...8^)
They take a lot of space.? I built one of those?for someone and it
seemed to be fairly stable.? I found a source for?new cans but
they are rather pricy.
The RX for my project was intended for installation in mint tins
as shown in sketch pic.???
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: What level math is in the RF design books?
William,
Try this:? Vrms = 0.3535 * Vpp? then, Po = Vrms*2 / 100
That's the simplest approximation.
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: 7 MHz Oscillator Ideas
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On Tue, Dec 10, 2019, 04:58 Chuck Carpenter < w5usj@...> wrote: Jerry,
I get about 3 kHz with a pair of crystals on 7MHz using the "fixture" in the picture.? I measured that with a 10V tuning range.
The SA612?oscillator is running from the 6V regulator circuit so the frequency isn't affected by supply voltage changes.
The GQRP Sudden RX kit uses a VFO for tuning.? You could take a shot at that using those 9mm cans...8^)
They take a lot of space.? I built one of those?for someone and it seemed to be fairly stable.? I found a source for?new cans but they are rather pricy.
The RX for my project was intended for installation in mint tins as shown in sketch pic.???
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: 7 MHz Oscillator Ideas
Would not be an issue with the tuning range limited to 3khz..
However, the frequency determining pot for the varactor diode is operating directly from the power supply.
?
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On Tue, Dec 10, 2019 at 02:58 AM, Chuck Carpenter wrote:
The SA612?oscillator is running from the 6V regulator circuit so the frequency isn't affected by supply voltage changes.
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Re: 7 MHz Oscillator Ideas
this is the vfo I made from Solid State Design
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Re: 7 MHz Oscillator Ideas
I built a simple regenerative receiver awhile ago using VK3YE design Rob mentioned and linked ?? Stable, sensitive.? Two transistors, a resonator, and an LM386, some parallel diodes as tuning capacitance rather than air variable.? No toroids.? First build was manhattan, second etched a "muppet" board.? Mine tunes 7025-75, am impressed with it's simplicity.? The ceramic resonators are about 25 cents from Mouser.
I was trying different regen receiver circuits with less than stellar results.? This one works very well.
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Nick Kennedy
Chuck Carpenter
k6whp