Re: Crystals in Softrock LTE combined kit
The use of subharmonic sampling is not so much to allow the mixer to operate at a lower rate. The switches in the QSD work reasonably well up to 10 meters, and they are used that way in the Ensemble RX II and Ensemble RXTX without subharmonic sampling. The issue in the Lite is that fundamental crystals for frequencies above 30 MHz (remember that the crystal has to be for 4x the operating frequency) are not readily available at a reasonable price.
Overtone crystals, which used to be the main way to generate higher frequencies, are no longer easy to find and are not inexpensive. They have mostly been replaced by crystal oscillator modules that use lower frequency crystals and PLL multipliers. Cheap modules are fine for computer clocks but are unsuitable for ham radio LOs because they have not been designed for low phase noise. In fact, computer clocks are often INTENTIONALLY spread to lessen the size of narrow radiated emission peaks. Using an overtone crystal would also require adjustment of the oscillator stage and measurement with high performance test equipment to make sure the oscillator was actually functioning on the correct overtone, negating the goal of a simple and quick build.
If there were enough demand for a Lite variant that would be useful on the higher HF bands (17m through 10m) it might be possible to do a design that incorporated a fixed ratio PLL multiplier in the LO design. You would want to avoid a 4X multiplier because that would place the base LO right at the intended operating frequency and leakage of that signal would be hard to avoid. A 3X or 5X multiplier might be suitable if appropriate inexpensive crystals are available; the Lite uses inexpensive crystals that are mass produced for use as clock oscillators for microcontrollers and their associated peripherals.
On Fri, Apr 11, 2014 at 4:16 PM, Mike Collins <mikecol@...> wrote:
?
Hey Robby,
Sure no problem.? I'm sure it could be clearer, but hopefully got
the idea of the "sampling" for others to understand.
73 and thanks for all your work !!
Mike Collins?? KF4BQ
On 4/11/2014 4:06 PM, R. R. (Robby) Robson wrote:
?
Thanks,
Mike.
As my
motto is "steal from the best with pride", do you mind
if I lift most of your fine exposition onto my web
pages?
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Thanks everyone for setting me straight on how the receiver uses the supplied crystals. This is something I may have read but didn't really understand.?
73s to all. ? ?de ?Jack ?W6VMJ
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Re: Low power readings on an Ensemble RXTX,could it be a PTT problem?
Success, installed HDSDR and the ExtIO DLL, set it to transmit with DL6IAKs tone generator and got 8.46 V on the RF probe at the bnc jack. John Stockman, KC2THY
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Re: Crystals in Softrock LTE combined kit
Hey Robby,
Sure no problem.? I'm sure it could be clearer, but hopefully got
the idea of the "sampling" for others to understand.
73 and thanks for all your work !!
Mike Collins?? KF4BQ
On 4/11/2014 4:06 PM, R. R. (Robby) Robson wrote:
toggle quoted message
Show quoted text
?
Thanks,
Mike.
As my
motto is "steal from the best with pride", do you mind
if I lift most of your fine exposition onto my web
pages?
|
Re: Crystals in Softrock LTE combined kit
Thanks, Mike.
As my motto is "steal from the best with pride", do you mind if I lift most of your fine exposition onto my web pages?
On Fri, Apr 11, 2014 at 3:01 PM, Mike Collins <mikecol@...> wrote:
?
On 4/11/2014 3:11 PM, R. R. (Robby)
Robson wrote:
?
See,
also,?
(the discussion on sub-harmonic sampling)
Hi Robby,
That actually has it wrong.? The statement:
- The two quadrature signals from the Divider stage are fed into
the mixer stage. The 4.6825 MHz quadrature signals from the
divider in the 20m option are rich in harmonics. The third
harmonic (14.0475) is what is actually used in the mixer stage.
It is true that the 4.6825MHz from the divider is rich in
harmonics (all odd becuz of square wave), but only the fundamental
freq is used by the mixer (since it is a digital chip and only
responds when the signal crosses the threshold).? The mixer itself
is what allows the sensitivity to harmonics, becuz it is a
sampling type.? A common analogy is a strobe light on a fan....you
will see the same thing when strobing for one revolution, also for
two revolutions, also for three, ...
The mixer is sensitive to the fundamental and all harmonics of
the mixer sampling freq, but the transformer (with 180deg phasing)
and the hookup of the mixer cancels even harmonics of the freq;
leaving only the fundamental and odd harmonics.
Just as you would see with a strobe light the signal will be
reduced (over the same time period).? The reduction for the 3rd
harmonic is 1/3 the voltage on the holding cap.? That give a
overall 20log(1/3) = -9.54dB loss in the signal compare to
receiving the fundamental.? This is the drawback to sub-sampling;
i.e. a reduction in sensitivity.? It does allow the mixer to
switch at a much lower rate which is why it is used.
The front end filter rejects the fundamental and also the 5th and
higher harmonic products so you are left with only the third.
The harmonic rich LO is often misstated as why the receiver works
with harmonics.? If the LO was a sine wave it would still work
fine (maybe more phase noise, but basically the same).
73,? Mike Collins?? KF4BQ
-- Cheers,
Robby
?
Richard R. (Robby) Robson
LTC USA (USA Retired)
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Re: Crystals in Softrock LTE combined kit
On 4/11/2014 3:11 PM, R. R. (Robby)
Robson wrote:
?
See,
also,?
(the discussion on sub-harmonic sampling)
Hi Robby,
That actually has it wrong.? The statement:
- The two quadrature signals from the Divider stage are fed into
the mixer stage. The 4.6825 MHz quadrature signals from the
divider in the 20m option are rich in harmonics. The third
harmonic (14.0475) is what is actually used in the mixer stage.
It is true that the 4.6825MHz from the divider is rich in
harmonics (all odd becuz of square wave), but only the fundamental
freq is used by the mixer (since it is a digital chip and only
responds when the signal crosses the threshold).? The mixer itself
is what allows the sensitivity to harmonics, becuz it is a
sampling type.? A common analogy is a strobe light on a fan....you
will see the same thing when strobing for one revolution, also for
two revolutions, also for three, ...
The mixer is sensitive to the fundamental and all harmonics of
the mixer sampling freq, but the transformer (with 180deg phasing)
and the hookup of the mixer cancels even harmonics of the freq;
leaving only the fundamental and odd harmonics.
Just as you would see with a strobe light the signal will be
reduced (over the same time period).? The reduction for the 3rd
harmonic is 1/3 the voltage on the holding cap.? That give a
overall 20log(1/3) = -9.54dB loss in the signal compare to
receiving the fundamental.? This is the drawback to sub-sampling;
i.e. a reduction in sensitivity.? It does allow the mixer to
switch at a much lower rate which is why it is used.
The front end filter rejects the fundamental and also the 5th and
higher harmonic products so you are left with only the third.
The harmonic rich LO is often misstated as why the receiver works
with harmonics.? If the LO was a sine wave it would still work
fine (maybe more phase noise, but basically the same).
73,? Mike Collins?? KF4BQ
|
Re: Crystals in Softrock LTE combined kit
See, also,? (the discussion on sub-harmonic sampling)
On Fri, Apr 11, 2014 at 12:16 PM, Alan <alan4alan@...> wrote:
?
Original Message -----
Subject: [softrock40] Crystals in Softrock LTE combined kit
>I really don't understand what is happening with the crystals for 20 meters operation. I understand that the counter needs a
>frequency that is four times that of the received signal to produce the two out of phase signals needed to produce the I an Q
>outputs.and I read that sampling is done at the 3rd overtone. Without a scope or spectrum analyzer I am having trouble trying to
>picture what the freq. is at the detector produced by the counter.
> The crystal supplied for 20 Meters is 18.73 megahertz.
>
>
> Is the crystal operating at the third overtone to create the 56 Mhz signal or is something else going on? I think I better buy
> a scope to really see what is happening.
>
>
A scope will not help:)
and other messages referring to "Subharmonic"
73 Alan G4ZFQ
-- Cheers,
Robby
?
Richard R. (Robby) Robson
LTC USA (USA Retired)
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Re: RXTX sparking and arcing (still having waveform issues)
Thank you, I am doing much better now. ?I am still wondering why I cannot get the wave form to come out correctly though. On Thursday, April 10, 2014 7:17 PM, "n5bz@..." wrote:
?
In order to see sparking/arcing, you need to either have considerable CURRENT flowing or a significant voltage difference between your RXTX and the voltmeter.
What is connected to the RXTX??
What is connected to the voltmeter?
You might have a significant RF pickup by an antenna (any nearby transmitters?), or a static electric pickup by an antenna (dust storms or wind or rain can build up a charge).
The leads on the meter could act as an antenna for some frequencies.
A switching supply that does NOT have a good earth ground on it can couple AC from the power line onto the 'GROUND' of the powersupply output.
When I run my finger over the metal grill on my laptop, I can feel a small 'buzz' from ac coupled through the power supply. There is no 'earth ground' on the AC wall plug. I am careful
NOT to use the laptop while near an earth ground! A voltmeter shows ~5 v ac when I touch one of the leads to the grill and stretch the other out.
Try battery power on the TXRX.
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Re: Low power readings on an Ensemble RXTX,could it be a PTT problem?
I reinstalled the USB driver, CFGSR, and Rocky. I get 0V on R35 with Rocky in transmit mode, but get 13V on R35 when I activate PTT from CFGSR, with Rocky off. Also get a much higher voltage on the BNC jack( .68V vs .163mV) It looks like a software problem. The USB is triggering PTT., ?Was not getting those reading before reinstalation..Will look at Rocky and how I have it set, may also try another SDR program.
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Re: Crystals in Softrock LTE combined kit
Original Message ----- Subject: [softrock40] Crystals in Softrock LTE combined kit I really don't understand what is happening with the crystals for 20 meters operation. I understand that the counter needs a frequency that is four times that of the received signal to produce the two out of phase signals needed to produce the I an Q outputs.and I read that sampling is done at the 3rd overtone. Without a scope or spectrum analyzer I am having trouble trying to picture what the freq. is at the detector produced by the counter.
The crystal supplied for 20 Meters is 18.73 megahertz.
Is the crystal operating at the third overtone to create the 56 Mhz signal or is something else going on? I think I better buy a scope to really see what is happening.
A scope will not help:) and other messages referring to "Subharmonic" 73 Alan G4ZFQ
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Re: Crystals in Softrock LTE combined kit
On 20m and 30m, the Softrock Lite II uses 1/3 subharmonic sampling. That means that the final sample rate isn't 14 MHz on 20m, it's 14 divided by 3. The actual rate with that crystal is 4.6825MHz for a center frequency of 14.0475MHz. The receiver covers all the usual QRP frequencies with a 48KHz sound card and nearly the entire CW portion of 20m with a 96KHz sound card.
On Fri, Apr 11, 2014 at 12:05 PM, <jackmargolis@...> wrote:
?
I really don't understand what is happening with the crystals for 20 meters operation. I understand that the counter needs a frequency that is four times that of the received signal to produce the two out of ?phase signals needed to produce the I an Q outputs.and I read that sampling is done at the 3rd overtone. ?Without a scope or spectrum analyzer I am having trouble trying to picture what the freq. is at the detector produced by the counter. ?
The crystal supplied for 20 Meters is 18.73 megahertz. ??
Is the crystal operating at the third overtone to create the 56 Mhz signal or is something else going on? ? ?I think I better buy a scope to really see what is happening.
|
Crystals in Softrock LTE combined kit
I really don't understand what is happening with the crystals for 20 meters operation. I understand that the counter needs a frequency that is four times that of the received signal to produce the two out of ?phase signals needed to produce the I an Q outputs.and I read that sampling is done at the 3rd overtone. ?Without a scope or spectrum analyzer I am having trouble trying to picture what the freq. is at the detector produced by the counter. ?
The crystal supplied for 20 Meters is 18.73 megahertz. ??
Is the crystal operating at the third overtone to create the 56 Mhz signal or is something else going on? ? ?I think I better buy a scope to really see what is happening.
|
Hi! How are you? ? People say it works ? ? ajsoenke@...?
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Re: RXTX sparking and arcing (still having waveform issues)
In order to see sparking/arcing, you need to either have considerable CURRENT flowing or a significant voltage difference between your RXTX and the voltmeter.
What is connected to the RXTX??
What is connected to the voltmeter?
You might have a significant RF pickup by an antenna (any nearby transmitters?), or a static electric pickup by an antenna (dust storms or wind or rain can build up a charge).
The leads on the meter could act as an antenna for some frequencies.
A switching supply that does NOT have a good earth ground on it can couple AC from the power line onto the 'GROUND' of the powersupply output.
When I run my finger over the metal grill on my laptop, I can feel a small 'buzz' from ac coupled through the power supply. There is no 'earth ground' on the AC wall plug. I am careful NOT to use the laptop while near an earth ground! A voltmeter shows ~5 v ac when I touch one of the leads to the grill and stretch the other out.
Try battery power on the TXRX.
|
Re: RXTX sparking and arcing (still having waveform issues)
Original Message ----- Subject: [softrock40] RXTX sparking and arcing (still having waveform issues) when I go to test the components with a voltmeter, I receive arcing and sparks off the board. I know the board is low voltage, but why is the radio doing this. You must have an intermittent short circuit on the power line. Probably the 12V line. Look carefully with a glass, maybe a solder splash or even a badly etched track. 73 Alan G4ZFQ
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RXTX sparking and arcing (still having waveform issues)
I had a question about the completed softrock kit. ?I put the kit together, and found out that the waveform shown in HDSDR was uniform across all bands and modes. ?In addition, when I go to test the components with a voltmeter, I receive arcing and sparks off the board. ?I know the board is low voltage, but why is the radio doing this.
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Re: Low power readings on an Ensemble RXTX,could it be a PTT problem?
Correction, 0V on R35 and 12.8v on R34. John Stockman, kc2thy
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Re: Low power readings on an Ensemble RXTX,could it be a PTT problem?
Made sure that Rocky's audio and I/Q were configured correctly and measured transmit and receive voltages on the hairpin of R34. Both were zero, so it looks like the transmit is not being keyed. Measured 12.8 V on R35 so its not my power supply. I set Rocky to transmit/tone mode which should result in a signal. It's back to the schematic for next steps and I will re-install the driver and Rocky again to make sure.I thank you and would welcome any further advice ?John Stockman, KC2THY
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Re: Info about SoftRock Lite II for IF monitoring
Hello Alan,
thanks again,
I have both of them :) - the amplifier wouldn't be problem, but without is more simple. 73, Ervin HA2OS
On Wed, Apr 9, 2014 at 1:27 PM, Alan <alan4alan@...> wrote:
?
Original Message -----
Subject: Re: [softrock40] Info about SoftRock Lite II for IF monitoring
>any special device to build
the kit? I mean: signal generator, oscilloscope, ...?
Ervin,
Nothing really.. But a multimeter, and maybe a receiver, does help confirm operation.
You probably will not need an amplifier, it's just a general warning, the level can be low on some rigs.
73 Alan G4ZFQ
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Re: Info about SoftRock Lite II for IF monitoring
Original Message ----- Subject: Re: [softrock40] Info about SoftRock Lite II for IF monitoring any special device to build the kit? I mean: signal generator, oscilloscope, ...? Ervin, Nothing really.. But a multimeter, and maybe a receiver, does help confirm operation. You probably will not need an amplifier, it's just a general warning, the level can be low on some rigs. 73 Alan G4ZFQ
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Shirley Dulcey KE1L
Jack