Here is what you have missed, if you are not in the world of DJs.
The DJ-Tech Mouse, which employs a super-nice big wheel in the center. Have a look:
https://djtechtools.com/2009/08/20/the-dj-mouse/
Showing posts with label sdr. Show all posts
Showing posts with label sdr. Show all posts
Tuesday, August 25, 2020
SDR and the DJ-Tech DJ-Mouse
Friday, August 23, 2013
the old phase shift question
Actually I am rather flattered by the fact that an experimental design, which I did a couple of years ago, still is under discussion.
The good ole question about how much phase shift you need to run Polyakov mixers for I/Q software defined radio (SDR).
Have a look: http://draaggolf.blogspot.com/2010/01/30m-subharmonic-iq-sdr-receiver.html
Yep, this is a very simple concept design, it worked, it suppressed the lower side-band. And yes, it uses 45 degrees of phase shift at the oscillator frequency, which is half the beat-frequency (for reasons of using frequency doubling Polyakov mixers).
Please see the comments on why other designs, resulting in 180 degrees of beat-frequency shift, still seem to work just fine.
My design is not perfect at all, using a potentiometer to adjust a radio-frequency phase-shift is neither elegant, nor stable. Keep in mind, that this quick and dirty design was more a proof of concept rather than a production ready machine.
73!
The good ole question about how much phase shift you need to run Polyakov mixers for I/Q software defined radio (SDR).
Have a look: http://draaggolf.blogspot.com/2010/01/30m-subharmonic-iq-sdr-receiver.html
Yep, this is a very simple concept design, it worked, it suppressed the lower side-band. And yes, it uses 45 degrees of phase shift at the oscillator frequency, which is half the beat-frequency (for reasons of using frequency doubling Polyakov mixers).
Please see the comments on why other designs, resulting in 180 degrees of beat-frequency shift, still seem to work just fine.
My design is not perfect at all, using a potentiometer to adjust a radio-frequency phase-shift is neither elegant, nor stable. Keep in mind, that this quick and dirty design was more a proof of concept rather than a production ready machine.
73!
Sunday, February 19, 2012
600m Signal Source
As we know by now, 472-479kHz it will be. In an earlier post I revealed some "cheap" frequencies which would mix into the new band.
Some further options using industrial crystals:
DigiKey sells a 4.754687MHz crystal... count to (divide by) 5 and further divide by two results in 475kHz. A super-VXO could be an option here.
The above mentioned count to 5 solution applies to the following crystals, found at the same source: 9.494531MHz, 9.509375MHz and 9.545MHz. Other crystals would allow for an out of band I/Q-SDR LO: 9.600MHz, 9.625MHz and 9.7941MHz. Here, the chain would be count to 5, divide by 4.
Further: 18.9375MHz, 19.0625MHz and 19.069928MHz and for I/Q-SDR: 18.869MHz, 18.8696MHz, 19.200MHz, 19.280MHz and 19.440MHz. Consequenctly, the chain would be count to 5, divide by 8.
Plus: 28.59375MHz, 28.5938MHz, 28.636MHz, 28.6363MHz and 28.63636MHz (count to 3, count to 5, divide by 4).
Taking it even higher: 38.000MHz and 38.00053MHz (count to 5, divide by 16). I/Q-SDR: 38.400MHz and 38.880MHz.
Also found at DigiKey: a 7.680MHz crystal. Divide by 16 results in 480kHz. Again, a super-VXO and some (severe) down pull should generate a signal in the band. This crystal provides easy access to I/Q-SDR: LO spot om 480kHz, even a mere 24kbps sample rate would cover the whole band. The same applies to the 15.360MHz found at the same store.
All the above mentioned crystals are of industrial kind. One option would be order one for the favorit solution, the other option would be to carefully watch out for those frequencies before dumping old computers & Co.
Some further options using industrial crystals:
DigiKey sells a 4.754687MHz crystal... count to (divide by) 5 and further divide by two results in 475kHz. A super-VXO could be an option here.
The above mentioned count to 5 solution applies to the following crystals, found at the same source: 9.494531MHz, 9.509375MHz and 9.545MHz. Other crystals would allow for an out of band I/Q-SDR LO: 9.600MHz, 9.625MHz and 9.7941MHz. Here, the chain would be count to 5, divide by 4.
Further: 18.9375MHz, 19.0625MHz and 19.069928MHz and for I/Q-SDR: 18.869MHz, 18.8696MHz, 19.200MHz, 19.280MHz and 19.440MHz. Consequenctly, the chain would be count to 5, divide by 8.
Plus: 28.59375MHz, 28.5938MHz, 28.636MHz, 28.6363MHz and 28.63636MHz (count to 3, count to 5, divide by 4).
Taking it even higher: 38.000MHz and 38.00053MHz (count to 5, divide by 16). I/Q-SDR: 38.400MHz and 38.880MHz.
Also found at DigiKey: a 7.680MHz crystal. Divide by 16 results in 480kHz. Again, a super-VXO and some (severe) down pull should generate a signal in the band. This crystal provides easy access to I/Q-SDR: LO spot om 480kHz, even a mere 24kbps sample rate would cover the whole band. The same applies to the 15.360MHz found at the same store.
All the above mentioned crystals are of industrial kind. One option would be order one for the favorit solution, the other option would be to carefully watch out for those frequencies before dumping old computers & Co.
Tuesday, January 17, 2012
600m SDR RX (TX)
As we know, presently there are a couple of frequencies of the 600m band open to amateur radio operators.
Most of authorities allow transmission somewhere above 500kHz. In The Netherlands the permitted range is 501-505kHz. In the future, depending on the decision of the WRC12, this will possibly change to 472 to 480kHz. The U.S.of A. proposed the following ranges 461-469 and 471-478 kHz.
Lets look at the (inexpensive) option the box73 SDR. The 80m version of this receiver uses a 14.000MHz oscillator. Operation on the 600m band can be achieved by changing the front-end filter and the SDR-LO.
Considering 48kbps sampling, the LO-frequencies would be the following
Most of authorities allow transmission somewhere above 500kHz. In The Netherlands the permitted range is 501-505kHz. In the future, depending on the decision of the WRC12, this will possibly change to 472 to 480kHz. The U.S.of A. proposed the following ranges 461-469 and 471-478 kHz.
Lets look at the (inexpensive) option the box73 SDR. The 80m version of this receiver uses a 14.000MHz oscillator. Operation on the 600m band can be achieved by changing the front-end filter and the SDR-LO.
Considering 48kbps sampling, the LO-frequencies would be the following
- QRG: 470kHz - LO: 1.843MHz
- QRG: 500kHz - LO: 2.000MHz
- 460.8 -/+ 24 = 436.8 .. 484.8
- 500.0 -/+ 24 = 476.0 .. 524.0
Sunday, November 27, 2011
SDR Meets DJ Gear
Hi there! Some of you may know that I am quite busy with music, dance and the stuff concerned.
Some rare occasions have it, and hamradio mixes with music mixing, aka DJing. And here is one of those occasions:
The DJ Mouse
http://www.dj-mouse.com/
Basically, there is nothing special about this mouse, other than the regular scroll wheel is somewhat wider and parallel with a jog wheel. It is just this jog wheel that makes all the difference.
All SDR software solutions I am aware of, are using the scroll wheel for sweeping the frequency. I always felt that this was somewhat awkward. Now we got a mouse with a rotary encoder, just like a VFO knob.
Still I scratch my head what can be done with the "scratch" button...
Some rare occasions have it, and hamradio mixes with music mixing, aka DJing. And here is one of those occasions:
The DJ Mouse
http://www.dj-mouse.com/
Basically, there is nothing special about this mouse, other than the regular scroll wheel is somewhat wider and parallel with a jog wheel. It is just this jog wheel that makes all the difference.
All SDR software solutions I am aware of, are using the scroll wheel for sweeping the frequency. I always felt that this was somewhat awkward. Now we got a mouse with a rotary encoder, just like a VFO knob.
Still I scratch my head what can be done with the "scratch" button...
Saturday, October 29, 2011
SDR for the 600m band
Some short not on an idea for the 600m band.
The typical SDR, as we all know, uses 4x the center frequency so that the 90 phase-shifts can easily be created by flip-flops.
In 2012, the Netherlands will most likely open the range 501-505kHz for ham radio operators. I figure a simple RX (maybe also TX) solution could be a 2.000MHz canned oscillator. This will get us spot on 500kHz center frequency, just as you may want. Comfortable 1 to 5kHz audio, which any sound card can handle easily, with a sample rate of only 24kHz. A further experiment should show if side-band suppression is required at all. I figure, a decent pre-selector should be enough already.
Should however, following a decision at the WRC-12, the range open to hams change to the range proposed by CEPT (472 to 480kHz), a 2.000MHz SDR-LO would be somewhat too high. In this case, the oscillator could easily be swapped with a 1.8432MHz one. Resulting in a center frequency of 460.8kHz. Audio up to 20kHz would still be somewhat a challenge for cheap sound hardware, never the less, a sample rate of 48kHz would cover it all.
No to the TX-part of it. One could either use a sound card generated signal, as provided by some software solution. One could also thing of generating an I/Q modulation signal at 4x the audio signal, divide and phase shift similarly to the LO chain. Unfortunately, we would now have a rich audio square wave. I figure some severe filtering will be required here, in order to end up with a sine wave.
I would not consider an AF phase-shifting network. I believe the frequency range is to great as provide accurate phase-shifting.
However, as in the RX part, it may be conceivable to filter the side-band at the RF range. A series of tank and trap circuits could possibly be enough. Mind you, the aerial matching itself is very selective too.
The typical SDR, as we all know, uses 4x the center frequency so that the 90 phase-shifts can easily be created by flip-flops.
In 2012, the Netherlands will most likely open the range 501-505kHz for ham radio operators. I figure a simple RX (maybe also TX) solution could be a 2.000MHz canned oscillator. This will get us spot on 500kHz center frequency, just as you may want. Comfortable 1 to 5kHz audio, which any sound card can handle easily, with a sample rate of only 24kHz. A further experiment should show if side-band suppression is required at all. I figure, a decent pre-selector should be enough already.
Should however, following a decision at the WRC-12, the range open to hams change to the range proposed by CEPT (472 to 480kHz), a 2.000MHz SDR-LO would be somewhat too high. In this case, the oscillator could easily be swapped with a 1.8432MHz one. Resulting in a center frequency of 460.8kHz. Audio up to 20kHz would still be somewhat a challenge for cheap sound hardware, never the less, a sample rate of 48kHz would cover it all.
No to the TX-part of it. One could either use a sound card generated signal, as provided by some software solution. One could also thing of generating an I/Q modulation signal at 4x the audio signal, divide and phase shift similarly to the LO chain. Unfortunately, we would now have a rich audio square wave. I figure some severe filtering will be required here, in order to end up with a sine wave.
I would not consider an AF phase-shifting network. I believe the frequency range is to great as provide accurate phase-shifting.
However, as in the RX part, it may be conceivable to filter the side-band at the RF range. A series of tank and trap circuits could possibly be enough. Mind you, the aerial matching itself is very selective too.
Saturday, August 6, 2011
455kHz SDR - a second thought
My previous blog was all about the idea of adding a softrock, or any other simple SDR-DC-RX, to a cheap (synthesized) AM radio. Well, honestly said, when thinking of it, this may be a totally unnecessary overkill.
Why? Well, very simple. The main purpose of all the quadrature stuff is to make the two sidebands that a DC-RX receives different. But, what if there is not other sideband? The following may not apply to the absolute cheapest of AM-receivers.
Concerning the ATS-404, I have ambiguous information. While some technical data mention the AM i.f. being 450kHz, the schematics diagram mentions a LT455H, which is a 455kHz ceramic filter having +/-3kHz 6dB bandwidth (+/-9kHz for attenuated bandwidth). If we tap before that filter, we definitely need quadrature, should we however tap the i.f. behind that filter, a non-quadrature SDR would be OK too.
Most of the better world-band receivers use a first i.f. somewhere high with a relatively wide crystal filter. Most of the narrow filtering is done at 455kHz. In this case, we probably wont need quadrature at all. All we have to do is to ensure that our SDR center frequency (or SDR-l.o.) falls close to but outside the range of the intermediate frequency range. In such a scenario, there would not be a second sideband to care about and also a simple mono-audio interface would already do the job.
The Target HF3 would be an example for such a receiver. The first i.f. is at 45MHz having a bandwidth of +/-3.75kHz. The second i.f. band would consequently be 455-3.75=451.25 to 455+3.75=458.75 kHz. In yesterday's example, using a 1.8432Mhz local oscillator, we ended up at an SDR center frequency of 460.8kHz, which is close but outside the HF3's second i.f. band. A regular direct conversion receiver with a local oscillator at 460.8kHz would therefore receive only a lower side-band, since there is no signal in its upper side-band.
My idea would be to try that out using a canned oscillator and two flip-flops for frequency division. With some isolation amplification a singled ended diode mixer and a cheap USB audio adapter should round up that experiment.
Why? Well, very simple. The main purpose of all the quadrature stuff is to make the two sidebands that a DC-RX receives different. But, what if there is not other sideband? The following may not apply to the absolute cheapest of AM-receivers.
Concerning the ATS-404, I have ambiguous information. While some technical data mention the AM i.f. being 450kHz, the schematics diagram mentions a LT455H, which is a 455kHz ceramic filter having +/-3kHz 6dB bandwidth (+/-9kHz for attenuated bandwidth). If we tap before that filter, we definitely need quadrature, should we however tap the i.f. behind that filter, a non-quadrature SDR would be OK too.
Most of the better world-band receivers use a first i.f. somewhere high with a relatively wide crystal filter. Most of the narrow filtering is done at 455kHz. In this case, we probably wont need quadrature at all. All we have to do is to ensure that our SDR center frequency (or SDR-l.o.) falls close to but outside the range of the intermediate frequency range. In such a scenario, there would not be a second sideband to care about and also a simple mono-audio interface would already do the job.
The Target HF3 would be an example for such a receiver. The first i.f. is at 45MHz having a bandwidth of +/-3.75kHz. The second i.f. band would consequently be 455-3.75=451.25 to 455+3.75=458.75 kHz. In yesterday's example, using a 1.8432Mhz local oscillator, we ended up at an SDR center frequency of 460.8kHz, which is close but outside the HF3's second i.f. band. A regular direct conversion receiver with a local oscillator at 460.8kHz would therefore receive only a lower side-band, since there is no signal in its upper side-band.
My idea would be to try that out using a canned oscillator and two flip-flops for frequency division. With some isolation amplification a singled ended diode mixer and a cheap USB audio adapter should round up that experiment.
ATS-404 idea
Using the second intermediate frequency, often at 455kHz, is widely known. A suitable I/Q-SDR would be based on a 1.8432MHz (canned) oscillator, resulting in a 460.8kHz center frequency. Assuming a 24k sample rate, would be adequate to cover the range from 450 to 460kHz perfectly.
Many I/Q-SDR kist are available, due to the size and the low price, the softrock lite could be suitable best.
So, why the ATS-404. I was looking for a relatively cheap wide coverage receiver having direct frequency entry. The 5kHz tuning steps on shortwave suit the 10kHz wide SDR just fine.
The ATS-404 uses the TA8132AN AM/FM-receiver IC. This IC has go the advantage of providing an IF-out at pin 9 (see data-sheet). Slight downside: the TA8132 employs a 450kHz intermediate frequency...
A service manual for the ATS-404 can be found here:
http://www.thiecom.de/ftp/sangean/ats404/
The remaining question... where to put the I/Q-SDR? Using a softrock lite, one may consider using the battery compartment. Speaking of battery, the radio runs of 4 AA cells. It can also be operated from 6V external power. I wonder if 5V from a USB-port would be sufficient, finally, the idea is to use a computer for the SDR anyway.
Which brings me to the last idea... a cheap (stereo!) USB-sound-interface could also be accomodated in the battery compartment, so that only connection would be a USB cable to the computer.
Many I/Q-SDR kist are available, due to the size and the low price, the softrock lite could be suitable best.
So, why the ATS-404. I was looking for a relatively cheap wide coverage receiver having direct frequency entry. The 5kHz tuning steps on shortwave suit the 10kHz wide SDR just fine.
The ATS-404 uses the TA8132AN AM/FM-receiver IC. This IC has go the advantage of providing an IF-out at pin 9 (see data-sheet). Slight downside: the TA8132 employs a 450kHz intermediate frequency...
A service manual for the ATS-404 can be found here:
http://www.thiecom.de/ftp/sangean/ats404/
The remaining question... where to put the I/Q-SDR? Using a softrock lite, one may consider using the battery compartment. Speaking of battery, the radio runs of 4 AA cells. It can also be operated from 6V external power. I wonder if 5V from a USB-port would be sufficient, finally, the idea is to use a computer for the SDR anyway.
Which brings me to the last idea... a cheap (stereo!) USB-sound-interface could also be accomodated in the battery compartment, so that only connection would be a USB cable to the computer.
Wednesday, April 6, 2011
17m XTAL Controlled QRSS / WSPR / QRP / SDR
Sorry for having been silent for a while. Some new thought, although not entirely mine, I believe sharing it this way would be more than appropriate.
The idea about the frequency generation is borrowed from DJ1ZB. Ha-Jo uses CB crystals on their fundamental and doubles the result.
Doubling sounds very much like two things I previously disclosed on this blot, namely, the subharmonic direct conversion receiver (e.g. this) and the subharmonic I/Q-SDR (see earlier posts on the SDR and possible frequencies).
Both designs rely on a local oscillator on half the operating frequency.
Concentrating what could be interesting for QRP, QRSS and WSPR, lets have a closer look to the available crystals.
Additionally, 18.090MHz is the quite close to the QRP frequency, a subharmonic direct conversion receiver would be an obvious choice, so would be a transmitter with a doubler...
Very obviously, the other frequencies are directed more to QRSS and WSPR. I am not going into the QRSS feature here, it is kinda trivial (see above).
Remaining topic: WSPR. The frequency produced by the 16T-XTAL is very very close to the WSPR "dial frequency" 18.1046MHz. With a Pierce oscillator the tiny amount of 633Hz upwards pull should not be a big deal; remember, on half the frequency, one only needs to pull half the distance.
RX: subharmonic direct conversion.
TX: subharmonic mixing of the local oscillator with an audio signal should create a DSB signal... that's the theory... I have not yet tried it yet, however, I fail to see any reason why this should not work.
The idea about the frequency generation is borrowed from DJ1ZB. Ha-Jo uses CB crystals on their fundamental and doubles the result.
Doubling sounds very much like two things I previously disclosed on this blot, namely, the subharmonic direct conversion receiver (e.g. this) and the subharmonic I/Q-SDR (see earlier posts on the SDR and possible frequencies).
Both designs rely on a local oscillator on half the operating frequency.
Concentrating what could be interesting for QRP, QRSS and WSPR, lets have a closer look to the available crystals.
- 27.105MHz (12T) => 9.035MHz x 2 = 18.070MHz
- 27.135MHz (15T) => 9.045MHz x 2 = 18.090MHz
- 27.155MHz (16T) => 9.051667MHz x 2 = 18.103333MHz
- 27.165MHz (17T) => 9.055MHz x 2 = 18.110MHz
Additionally, 18.090MHz is the quite close to the QRP frequency, a subharmonic direct conversion receiver would be an obvious choice, so would be a transmitter with a doubler...
Very obviously, the other frequencies are directed more to QRSS and WSPR. I am not going into the QRSS feature here, it is kinda trivial (see above).
Remaining topic: WSPR. The frequency produced by the 16T-XTAL is very very close to the WSPR "dial frequency" 18.1046MHz. With a Pierce oscillator the tiny amount of 633Hz upwards pull should not be a big deal; remember, on half the frequency, one only needs to pull half the distance.
RX: subharmonic direct conversion.
TX: subharmonic mixing of the local oscillator with an audio signal should create a DSB signal... that's the theory... I have not yet tried it yet, however, I fail to see any reason why this should not work.
Sunday, October 24, 2010
2048kHz XTAL
Haven't got the luck to obtain any of the before mentioned 2030kHz crystals? Well, there is hope ;-)
What about the 2048kHz standard crystal? This one should be widely available.
Let's see what we can do with this one. First of all, such crystals can be penned down, 18kHz should be doable. But what more can we do?
600m I/Q-SDR
For the typical SDR, one could simply feed this signal into two Flip Flops, resulting in an SDR LO of 512kHz. With a minimum sampling rate of 24kbps, a range from 500kHz to 524kHz would be covered. This is in particular interesting since 518kHz, the international NAVTEX frequency falls into this range.
2200m I/Q-SDR
Taking one of the two 512kHz signal and feed it into two further Flip Flops would provide an SDR-LO of 128kHz, which would provide a frequency range of 116kHz to 140kHz, covering the 136kHz amateur radio band.
40m Digi-Mode Superhet
As non SDR use of the crystal, a more classical approach is in reach: a 2048kHz (super-)VXO and a 5000kHz crystal filter coincides nicely with the 40m digital mode range. The 2048kHz crystal could additionally penned down (see earlier post about xtal-penning) to cover the 40m WSPR and PSK frequencies.
20m Digi-Mode Superhet
In the 20m band, the WSPR frequency is easily covered. The trick here, a 2048kHz (super-)VXO as LO for a subharmonic mixer, which per se doubles the LO-frequency. Hence, the effective LO-frequency would be 4096kHz. In such a concept, it would be somewhat obvious to use a 10MHz crystal filter.
10m CW Superhet
Similar to the 20m concept, a subharmonic mixer would be required. As intermediate frequency, 24.000MHz would be obvious. However, watch out for the correct crystals for the filter! Most crystal will be overtone crystals, for a cheap filter we would need fundamental frequency crystals, and yes, they do exist for 24.000MHz.
40m LSB Superhet
Here is a simple one. The sum of 2048kHz and 5068.8kHz results in 7116.8kHz. I would propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. As LO a super-VXO using 5068.8kHz crystals would an obvious choice. Additional options would be a 5120kHz VXO (getting us to 7168kHz), a 9216kHz VXO (9216-2048=7168), or, for some of us, a 5200kHz VXO (7248kHz).
80m LSB Superhet
This could be a tricky one. I would, once again, propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. A conceivable could employ a 5.74MHz ceramic resonator. Subtractive mixing would provide a range, depending how far one pulls the VFO, of a couple of 10kHz about 3692kHz.
4096er Grabber Receiver
You may remember that my 30m grabber receiver employs a subharmonic mixer. Well, the exact same can be done for the 4096er hf-beacons. However, those beacons spread a little bit more than the 100Hz wide 30m QRSS segment, therefore, I would skip the crystal filter. This would have the advantage of also showing beacons below the 4.096MHz nominal frequency in a good old fashion DSB way.
4096er I/Q-SDR Grabber Receiver
One of the most popular entries on this blog is concerned a subharmonic I/Q-SDR in which the 90 degree I/Q phase-shift is done on half the frequency and hence amounts to 45 degrees on the subharmonic local oscillator. The exact same could be done for the 4096er beacon range (click here for more info) using a 2.048MHz crystal and some RC/RR network as shown in the subharmonic SDR article.
There may be more uses of this crystal, feel free to add comments with additional ideas!
What about the 2048kHz standard crystal? This one should be widely available.
Let's see what we can do with this one. First of all, such crystals can be penned down, 18kHz should be doable. But what more can we do?
600m I/Q-SDR
For the typical SDR, one could simply feed this signal into two Flip Flops, resulting in an SDR LO of 512kHz. With a minimum sampling rate of 24kbps, a range from 500kHz to 524kHz would be covered. This is in particular interesting since 518kHz, the international NAVTEX frequency falls into this range.
2200m I/Q-SDR
Taking one of the two 512kHz signal and feed it into two further Flip Flops would provide an SDR-LO of 128kHz, which would provide a frequency range of 116kHz to 140kHz, covering the 136kHz amateur radio band.
40m Digi-Mode Superhet
As non SDR use of the crystal, a more classical approach is in reach: a 2048kHz (super-)VXO and a 5000kHz crystal filter coincides nicely with the 40m digital mode range. The 2048kHz crystal could additionally penned down (see earlier post about xtal-penning) to cover the 40m WSPR and PSK frequencies.
20m Digi-Mode Superhet
In the 20m band, the WSPR frequency is easily covered. The trick here, a 2048kHz (super-)VXO as LO for a subharmonic mixer, which per se doubles the LO-frequency. Hence, the effective LO-frequency would be 4096kHz. In such a concept, it would be somewhat obvious to use a 10MHz crystal filter.
10m CW Superhet
Similar to the 20m concept, a subharmonic mixer would be required. As intermediate frequency, 24.000MHz would be obvious. However, watch out for the correct crystals for the filter! Most crystal will be overtone crystals, for a cheap filter we would need fundamental frequency crystals, and yes, they do exist for 24.000MHz.
40m LSB Superhet
Here is a simple one. The sum of 2048kHz and 5068.8kHz results in 7116.8kHz. I would propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. As LO a super-VXO using 5068.8kHz crystals would an obvious choice. Additional options would be a 5120kHz VXO (getting us to 7168kHz), a 9216kHz VXO (9216-2048=7168), or, for some of us, a 5200kHz VXO (7248kHz).
80m LSB Superhet
This could be a tricky one. I would, once again, propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. A conceivable could employ a 5.74MHz ceramic resonator. Subtractive mixing would provide a range, depending how far one pulls the VFO, of a couple of 10kHz about 3692kHz.
4096er Grabber Receiver
You may remember that my 30m grabber receiver employs a subharmonic mixer. Well, the exact same can be done for the 4096er hf-beacons. However, those beacons spread a little bit more than the 100Hz wide 30m QRSS segment, therefore, I would skip the crystal filter. This would have the advantage of also showing beacons below the 4.096MHz nominal frequency in a good old fashion DSB way.
4096er I/Q-SDR Grabber Receiver
One of the most popular entries on this blog is concerned a subharmonic I/Q-SDR in which the 90 degree I/Q phase-shift is done on half the frequency and hence amounts to 45 degrees on the subharmonic local oscillator. The exact same could be done for the 4096er beacon range (click here for more info) using a 2.048MHz crystal and some RC/RR network as shown in the subharmonic SDR article.
There may be more uses of this crystal, feel free to add comments with additional ideas!
2030kHz XTAL
Browsing one of the regional electronic (online) shops, I found a 2030kHz crystal, which would be perfect for a couple of projects. The order seems a little odd, however, the order reflects the difficulty of the different projects, the further down, the more difficult to realize.
600m I/Q-SDR
For the typical SDR, one could simply feed this signal into two Flip Flops, resulting in an SDR LO of 507.5kHz.
With a minimum sampling rate of 24kbps, a range from 495.5kHz to 519.5kHz would be covered. This is in particular interesting since 518kHz, the international NAVTEX frequency falls into this range.
2200m I/Q-SDR
Taking one of the two 507.5kHz signal and feed it into two further Flip Flops would provide an SDR-LO of 126.875kHz, which would provide a frequency range of 114.875kHz to 138.875kHz, covering the 136kHz amateur radio band.
40m QRP Superhet
As non SDR use of the crystal, a more classical approach is in reach: a 2030kHz (super-)VXO and a 5000kHz crystal filter coincides nicely with the 40m QRP frequency. The 2030kHz crystal could additionally penned down (see earlier post about xtal-penning) to cover lower frequencies in the 40m CW section.
20m QRP Superhet
Also the 20m QRP frequency is easily covered. The trick here, a 2030kHz (super-)VXO as LO for a subharmonic mixer, which per se doubles the LO-frequency. Hence, the effective LO-frequency would be 4060kHz. In such a concept, it would be somewhat obvious to use a 10MHz crystal filter.
10m QRP Superhet
Similar to the 20m concept, a subharmonic mixer would be required. As intermediate frequency, 24.000MHz would be obvious. However, watch out for the correct crystals for the filter! Most crystal will be overtone crystals, for a cheap filter we would need fundamental frequency crystals, and yes, they do exist for 24.000MHz.
40m LSB Superhet
Here is a simple one. The sum of 2030kHz and 5068.8kHz results in 7098.8kHz. I would propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. As LO a super-VXO using 5068.8kHz crystals would an obvious choice. Additional options would be a 5120kHz VXO (getting us to 7150kHz), a 9216kHz VXO (9216-2030=7186), or, for some of us, a 5200kHz VXO (7230kHz).
80m LSB Superhet
This could be a tricky one. I would, once again, propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. A conceivable could employ a 5.74MHz ceramic resonator. Subtractive mixing would provide a range, depending how far one pulls the VFO, of a couple of 10kHz about 3710kHz.
There may be more uses of this crystal, feel free to add comments with additional ideas!
600m I/Q-SDR
For the typical SDR, one could simply feed this signal into two Flip Flops, resulting in an SDR LO of 507.5kHz.
With a minimum sampling rate of 24kbps, a range from 495.5kHz to 519.5kHz would be covered. This is in particular interesting since 518kHz, the international NAVTEX frequency falls into this range.
2200m I/Q-SDR
Taking one of the two 507.5kHz signal and feed it into two further Flip Flops would provide an SDR-LO of 126.875kHz, which would provide a frequency range of 114.875kHz to 138.875kHz, covering the 136kHz amateur radio band.
40m QRP Superhet
As non SDR use of the crystal, a more classical approach is in reach: a 2030kHz (super-)VXO and a 5000kHz crystal filter coincides nicely with the 40m QRP frequency. The 2030kHz crystal could additionally penned down (see earlier post about xtal-penning) to cover lower frequencies in the 40m CW section.
20m QRP Superhet
Also the 20m QRP frequency is easily covered. The trick here, a 2030kHz (super-)VXO as LO for a subharmonic mixer, which per se doubles the LO-frequency. Hence, the effective LO-frequency would be 4060kHz. In such a concept, it would be somewhat obvious to use a 10MHz crystal filter.
10m QRP Superhet
Similar to the 20m concept, a subharmonic mixer would be required. As intermediate frequency, 24.000MHz would be obvious. However, watch out for the correct crystals for the filter! Most crystal will be overtone crystals, for a cheap filter we would need fundamental frequency crystals, and yes, they do exist for 24.000MHz.
40m LSB Superhet
Here is a simple one. The sum of 2030kHz and 5068.8kHz results in 7098.8kHz. I would propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. As LO a super-VXO using 5068.8kHz crystals would an obvious choice. Additional options would be a 5120kHz VXO (getting us to 7150kHz), a 9216kHz VXO (9216-2030=7186), or, for some of us, a 5200kHz VXO (7230kHz).
80m LSB Superhet
This could be a tricky one. I would, once again, propose to build a full-lattice filter with two original and two penned down 2030kHz crystals. A conceivable could employ a 5.74MHz ceramic resonator. Subtractive mixing would provide a range, depending how far one pulls the VFO, of a couple of 10kHz about 3710kHz.
There may be more uses of this crystal, feel free to add comments with additional ideas!
Monday, October 4, 2010
WSPR 2.1 - a possible solution for 600m
Background
Joe, K1JT, recently made WSPR 2.1 available which now employs I/Q-SDR. Primarily it seems to be intended for the SoftRock RXTX Ensemble.
I figure, with the correct tweek, it could be made to operate on the 600m-WSPR range as well. Not sure about the precise working of the I/Q-SDR option of Joe's software, so 2 scenarios are possible:
Oscillator
In case 1, a SDR center frequency of 500kHz would be just fine, hence, the transceiver design could be based on a simple 2.000MHz CMOS oscillator.
In case 2, the SDR center frequency would need to be 502.4kHz. This would chance the design in so far, that a XO would have to be pulled to 2.0096Mhz. A pull by 9.6kHz could be ambitious on 2MHz, even in a Pierce oscillator, but certainly worth a try.
Mixers
Keep it simple, I would very likely opt for 4066 switches. Other stuff imaginable....
Power Amplifier
We are digital, using carriers, linearity is not the primary goal at this stage. So, simple/cheap possibilities would be IRF510, IRF820 etc.
Thoughts
Frequencies are kinda low, so, this all could be done in pure CMOS, which would have the advantage of a) being low power and b) easily creating 8V output to drive the MOSFET.
I hope I can realize this before the expiry of the experimental license.
Joe, K1JT, recently made WSPR 2.1 available which now employs I/Q-SDR. Primarily it seems to be intended for the SoftRock RXTX Ensemble.
I figure, with the correct tweek, it could be made to operate on the 600m-WSPR range as well. Not sure about the precise working of the I/Q-SDR option of Joe's software, so 2 scenarios are possible:
- An ideal case would be that the software employs its own SDR-LO, meaning that it would be sufficient to have the WSPR-band within the coverage of the SDR-receiver.
- Could be that the software does not provide a "virtual local oscillator". In this case, the SDR-center frequency would need to coincide with the "dial frequency" for the respective band.
Oscillator
In case 1, a SDR center frequency of 500kHz would be just fine, hence, the transceiver design could be based on a simple 2.000MHz CMOS oscillator.
In case 2, the SDR center frequency would need to be 502.4kHz. This would chance the design in so far, that a XO would have to be pulled to 2.0096Mhz. A pull by 9.6kHz could be ambitious on 2MHz, even in a Pierce oscillator, but certainly worth a try.
Mixers
Keep it simple, I would very likely opt for 4066 switches. Other stuff imaginable....
Power Amplifier
We are digital, using carriers, linearity is not the primary goal at this stage. So, simple/cheap possibilities would be IRF510, IRF820 etc.
Thoughts
Frequencies are kinda low, so, this all could be done in pure CMOS, which would have the advantage of a) being low power and b) easily creating 8V output to drive the MOSFET.
I hope I can realize this before the expiry of the experimental license.
Tuesday, September 14, 2010
Hybrid SDR Dual Grabber
Testing new aerials is a nice thing, however, comparison to a known antenna would be a nice thing to do.
Actually, this has been done before, by Claudio i2NDT (check it out!).
So, what's the big fuzz about another approach? Well, testing with transmitters would not allow for testing active antennae, obviously. So, what will it be, 2 receivers of the same make? Well, maybe. Tolerances could still play tricks and mess up the measurements.
If you think of it, the solution is as obvious as it is simple... almost a miracle that nobody was writing about it before: use an I/Q-SDR direct conversion receiver with some slight modifications.
Such a receiver actually consists of two identical receiver sharing a local oscillator. The 90 degrees phase shift
Even the cheapest of I/Q-SDR receivers aims for the I and the Q channels being matched as good as possible. Usually, low tolerance parts are used all over.
As modification I would consider the following (once again one of my lists):
Actually, this has been done before, by Claudio i2NDT (check it out!).
So, what's the big fuzz about another approach? Well, testing with transmitters would not allow for testing active antennae, obviously. So, what will it be, 2 receivers of the same make? Well, maybe. Tolerances could still play tricks and mess up the measurements.
If you think of it, the solution is as obvious as it is simple... almost a miracle that nobody was writing about it before: use an I/Q-SDR direct conversion receiver with some slight modifications.
Such a receiver actually consists of two identical receiver sharing a local oscillator. The 90 degrees phase shift
Even the cheapest of I/Q-SDR receivers aims for the I and the Q channels being matched as good as possible. Usually, low tolerance parts are used all over.
As modification I would consider the following (once again one of my lists):
- add a switch to toggle between the usual 3dB splitter and two individual (crystal) filtered front ends
- configure spectrum-lab to show left and write audio channels in individual waterfalls
Tuesday, August 31, 2010
MF/LF Dual Band SDR
Just an idea, what about a 2.000MHz local oscillator. For regular SDR purposes, this will and up at 500kHz centre frequency. Ok... not that surprising.
What about taking this 500kHz signal and use it as LO for another SDR setup. Well, that would provide as with a centre frequency of 125kHz.
Assuming a regular 48kH sampling, two interesting frequencies are in reach:
What about taking this 500kHz signal and use it as LO for another SDR setup. Well, that would provide as with a centre frequency of 125kHz.
Assuming a regular 48kH sampling, two interesting frequencies are in reach:
- MF: 476-524kHz
- LF: 101-149kHz
Thursday, February 4, 2010
LW & MW SDR
Thoughts are back on 500kHz and 136kHz.
Assume we are going SDR, RX and maybe TX, one rig could serve both frequencies.
Conceptual design:
My experience is that (for my computers) 96k sampling works best. The observable ranges would therefore be:
Assume we are going SDR, RX and maybe TX, one rig could serve both frequencies.
Conceptual design:
- TCXO on 4.1943MHz
- 4.1943 / 2 = 2.0972
- 2.0972 / 4 = 0.5243 (SDR center frequency)
- about 20kHz above the band
- 4.1943 / 8 = 0.5243
- 0.5243 / 4 = 0.1311 (SDR center frequency)
- about 6kHz below the band
My experience is that (for my computers) 96k sampling works best. The observable ranges would therefore be:
- 476.3kHz - 572.3kHz for MW
- 83.1kHz - 179.1kHz for LW
Saturday, January 16, 2010
500kHz - SDR crude mod / 500kHz source drifts
The box73 "Einsteiger SDR" for 80m was unused now for a long time. Time to do something with it.
Hence, I grabbed issue 6/2009 of the "Funkamateur" and was looking into the 455kHz mod of the SDR receiver.
This is what I have done so far:
- replaced the 14.000Mhz oscillator by a 1.843MHz oscillator
- replaced the tank coil with a 4k7 resistor
This results is no pre-selection at all. OK, a test anyway.
The official mod also replaces sampling capacitors and all inductors for improved performance.
Wired up to the BB6W clone (7m wire + 9:1 balun) and spectrumlab tweak a bit, this is a first snapshot. Not only does this show two WSPR signals, the faint drifting signal at about 502740Hz is the exciter operating at the ground floor of my house, with 30cm of wire at the 7493 Q2 pin. As assumed, a ceramic resonator drifts, and will even spoil the fun when the frequency is divided by 8. (see image below)
Next step, something selective in the front-end, maybe replacing the sampling capacitors...
Monday, January 11, 2010
500kHz - subharmonic DC-RX or I/Q-SDR
My earlier mistake (4060) was resulting in the birth of a new idea.
Subharmonic stuff needs the local oscillator of half the operating frequency, so, a rather stable subharmonic local oscillator for 500kHz could be made by using a 4060 ripple counter w/ internal oscillator which divides by 16 at Q4 (pin 7). Sure, in this design, a crystal should be used. I figure this will make a nice and stable local oscillator for a subharmonic direct conversion receiver for the 501 to 504kHz band. Any drift of the crystal will have a 1/8 effect on 500kHz.
Depending on what is going on between 495 and 499kHz, image canceling could be considered.
Subharmonic stuff needs the local oscillator of half the operating frequency, so, a rather stable subharmonic local oscillator for 500kHz could be made by using a 4060 ripple counter w/ internal oscillator which divides by 16 at Q4 (pin 7). Sure, in this design, a crystal should be used. I figure this will make a nice and stable local oscillator for a subharmonic direct conversion receiver for the 501 to 504kHz band. Any drift of the crystal will have a 1/8 effect on 500kHz.
Depending on what is going on between 495 and 499kHz, image canceling could be considered.
Sunday, January 10, 2010
500kHz brain storming
Being a part of the early access experimenters group, I am in urgent need of ideas how to become QRV on 500kHz.
Receiving seems no issue: SDR using a 2.048MHz LO (produces a center frequency of 512kHz. Alternatively 4.096MHz and an additional divider... There is an 2.097152MHz oscillator available (Reichelt). Dropping this in the box73 SDR will result in a center of 524.3kHz, well in range with 96k sampling.
RX antenna should also be no deal at all, E-probe etc.
How to transmit?? Hmmm, maybe mixing two standard crystals 2.000MHz and 2.500MHz. Yep, that could be the source. 2.500MHz modulated Pierce, so we get a frequency somewhat higher, and the 2.000MHz as VXO for setting the QRG, pulled down, so less is subtracted. This should get me into the 501-504kHz regime.
Found an idea on the internet, 4.000MHz crystal, divide by 8. This will mean to pull the oscillator between 4.008 and 4.032MHz, now THAT is ambitious.
Now fetching the book "LF Today" from the shelf. Will now read the parts which I skipped in the first place.
Ideas welcome, just send me an email!
Receiving seems no issue: SDR using a 2.048MHz LO (produces a center frequency of 512kHz. Alternatively 4.096MHz and an additional divider... There is an 2.097152MHz oscillator available (Reichelt). Dropping this in the box73 SDR will result in a center of 524.3kHz, well in range with 96k sampling.
RX antenna should also be no deal at all, E-probe etc.
How to transmit?? Hmmm, maybe mixing two standard crystals 2.000MHz and 2.500MHz. Yep, that could be the source. 2.500MHz modulated Pierce, so we get a frequency somewhat higher, and the 2.000MHz as VXO for setting the QRG, pulled down, so less is subtracted. This should get me into the 501-504kHz regime.
Found an idea on the internet, 4.000MHz crystal, divide by 8. This will mean to pull the oscillator between 4.008 and 4.032MHz, now THAT is ambitious.
Now fetching the book "LF Today" from the shelf. Will now read the parts which I skipped in the first place.
Ideas welcome, just send me an email!
Saturday, January 9, 2010
SoftRock lite 80m
The SoftRock lite 80 is up and running. I used a 14.285MHz crystal, so the center frequency is about 3571250Hz. The receiver provides sold copy from 3525kHz to 3615kHz when using a sample rate of 96k.
I assume that the ghost lines about the center frequency's zerobeat line will be reduced as soon as the receiver is in a proper encasing.
Wednesday, January 6, 2010
SDR for QRSS
Finally I started building the SoftRock lite 80. This will be serving as a grabber receiver for the upper QRSS frequency (3599900Hz) as well as the color burst frequency (3579545Hz).
In order to allow for those frequencies, I will drop in a 14.285MHz crystal, which I ordered from Rich some time ago. This will result in a center frequency of 3571250Hz, not too far off 3.6MHz and not too close to the color burst frequency either. This receiver, assuming a sample rate of 96k, will be having a range of about 3.523MHz to 3.619MHz.
The original SoftRock lite kit comes with a 20m qrp crystal (14.060MHz), which would allow for the low QRSS range at 3500800Hz and also essentially covers the 80m CW range to about 3.563MHz.
If you think, this is something I want to build myself, yep, it is doable, and it is cheap (see my links). However, this kit involves some SMD soldering, which not everyone is confident doing.
There is an alternative however. Check out my earlier postings when I was writing about the "box73" SDR kit aka SDR Einsteiger-Kit. This kit is also not expensive at all, and it does not involve any SMD parts. Additionally, box73.de offers a hardware kit for the SDR kit, which provides you with an encasing, connectors and a cable to connect the receiver with a soundcard. The "downside"of this kit is, that it employ a canned oscillator of either 14.000MHz or 14.318MHz. The second would be suitable for the upper QRSS frequency, however, the color burst frequency will zero beat. Zero beat will also be the problem with the 14.000MHz version, maybe it will still be suitable for 800Hz, but, this is very close to the LO. I will try this, I ordered and built the 14.000MHz version. One also could imagine to build a clock oscillator with some gates and a crystal, possibly making it switchable....
BTW, most publications speak about a range of +/- 24kHz for such a receiver. This is since a sampling rate of 48k is assumed. With the built in soundcards of the Asus EeeTOP and the MSI Wind NetTop 96k samples are no problem and a bandwidth of nearly +/- 48k about the center frequency can be received.
In order to allow for those frequencies, I will drop in a 14.285MHz crystal, which I ordered from Rich some time ago. This will result in a center frequency of 3571250Hz, not too far off 3.6MHz and not too close to the color burst frequency either. This receiver, assuming a sample rate of 96k, will be having a range of about 3.523MHz to 3.619MHz.
The original SoftRock lite kit comes with a 20m qrp crystal (14.060MHz), which would allow for the low QRSS range at 3500800Hz and also essentially covers the 80m CW range to about 3.563MHz.
If you think, this is something I want to build myself, yep, it is doable, and it is cheap (see my links). However, this kit involves some SMD soldering, which not everyone is confident doing.
There is an alternative however. Check out my earlier postings when I was writing about the "box73" SDR kit aka SDR Einsteiger-Kit. This kit is also not expensive at all, and it does not involve any SMD parts. Additionally, box73.de offers a hardware kit for the SDR kit, which provides you with an encasing, connectors and a cable to connect the receiver with a soundcard. The "downside"of this kit is, that it employ a canned oscillator of either 14.000MHz or 14.318MHz. The second would be suitable for the upper QRSS frequency, however, the color burst frequency will zero beat. Zero beat will also be the problem with the 14.000MHz version, maybe it will still be suitable for 800Hz, but, this is very close to the LO. I will try this, I ordered and built the 14.000MHz version. One also could imagine to build a clock oscillator with some gates and a crystal, possibly making it switchable....
BTW, most publications speak about a range of +/- 24kHz for such a receiver. This is since a sampling rate of 48k is assumed. With the built in soundcards of the Asus EeeTOP and the MSI Wind NetTop 96k samples are no problem and a bandwidth of nearly +/- 48k about the center frequency can be received.
Subscribe to:
Posts (Atom)