A while ago, I built the Octaplumb octagonal RX loop, made from heavy gauge copper wire and PVC plumbing parts (see earlier posts). The loop was tuned to 504kHz, since that was what we had at the time.
Very recently, we know got a slightly different range. Hence, the center QRG of the Octaplumb had to be changed. Some experimentation showed that adding 82pF to the 680pF which are in parallel to the butterfly configed poly-vary-con.
Showing posts with label 500k. Show all posts
Showing posts with label 500k. Show all posts
Wednesday, January 2, 2013
Tuesday, February 28, 2012
MF/HF Aerial
And along came an idea....
You may have heard about the CobbWeb aerial. Essentially, this is a cluster of dipoles for the bands 20m, 17m 15m, 12m and 10m. The cluster is fed via a coax choke.
Maybe there is a way to squeeze more out of this aerial. The amount of wire in the dipole array creates a decent capacity, I figure.
It may be worth a try to build such an aerial, feed it with RG-6. And, for MF purposes, use the feedline's shield (and core) as vertical and the dipole array as capacitive load. The rf choke could further help to increase the load on the (very) short Marconi for 600m.
This would be somewhat like the antenna disclosed in the U.S. Patent 3,569,970, (see Figs.7a,7b) but using the CobWebb in place of the stretched dipoles.
You may have heard about the CobbWeb aerial. Essentially, this is a cluster of dipoles for the bands 20m, 17m 15m, 12m and 10m. The cluster is fed via a coax choke.
Maybe there is a way to squeeze more out of this aerial. The amount of wire in the dipole array creates a decent capacity, I figure.
It may be worth a try to build such an aerial, feed it with RG-6. And, for MF purposes, use the feedline's shield (and core) as vertical and the dipole array as capacitive load. The rf choke could further help to increase the load on the (very) short Marconi for 600m.
This would be somewhat like the antenna disclosed in the U.S. Patent 3,569,970, (see Figs.7a,7b) but using the CobWebb in place of the stretched dipoles.
Wednesday, February 22, 2012
472kHz Phasing Transmitter
We have seen that a 1.8432MHz oscillator will provide us with a 460.8kHz I/Q-SDR LO.
This is very much in a comfortable range for of the new amateur radio MF band, i.e. 11.2kHz to the lower band edge and 18.2kHz to the higher band edge.
Now, how to generate the modulator signal? Phasing style, the easiest would be to build an oscillator for the 44.8 to 72.8kHz and use two Flip-Flops to generated the 90 degrees phase shift.
As to receiving, the 11.2kHz to 18.2kHz is in the comfort zone of any 48kbps sampling sound card.
There you have it, my presently preferred solution for the new 600m amateur radio band.
This is very much in a comfortable range for of the new amateur radio MF band, i.e. 11.2kHz to the lower band edge and 18.2kHz to the higher band edge.
Now, how to generate the modulator signal? Phasing style, the easiest would be to build an oscillator for the 44.8 to 72.8kHz and use two Flip-Flops to generated the 90 degrees phase shift.
- Such an oscillator could be a rather simple function generator. Other solutions could be based on micro-controllers such as PICs, PICAXE, AT-Tiny, etc. With such a controller, it would also be possible to program features like memory channels, frequency display, beacon-keyer...
- Another approach would be to build a crystal oscillator, using cheap industrial xtals, and divide it down. Some ideas could be crystals from the XMHz range divided by N (by means of a binary counter) before feeding the Flip-Flops:
- 3.000MHz / 64 = 46.88kHz resulting in 472.5kHz
- 3.072MHz / 64 = 48.0kHz resulting in 472.8kHz
- 3.2768MHz / 64 = 51.2kHz finally resulting in 473.6kHz
- 3.579545MHz / 64 = 55.93kHz resulting in 474.78kHz
- 3.6864MHz / 64 = 57.6kHz resulting in 475.2kHz
- 3.93216MHz / 64 = 61.44kHz resulting in 476.16kHz
- 4.000MHz / 64 = 62.5kHz resulting in 476.4kHz
- 4.096MHz / 64 = 64.0kHz resulting in 4768kHz
- 4.194394MhZ / 64 = 65.54kHz resulting in 477.2kHz
- 4.433619MHz / 64 = 69.28kHz resulting in 478.1kHz
- In the light of the above, ham-radio crystal such as (in MHz) 3.530, 3.535, 5.540, 3.550, 3.555, 3.560, 3.575611, 3.880, 3.885 can fill in gaps. Those crystals are found at box73.de "expanded spectrum systems".
- With some luck, one finds tons and tons of surplus crystals in the range of 2.8672MHz to 4.6592MHz. As I recall, there where channelised commercial transceivers (e.g. military, maritime etc.) making use of crystals in that range.
- Similar to the crystal approach, one could consider to use 3.58MHz, 4.0MHz, 4.19Mhz, 4.50MHz and 4.91MHz ceramic resonators for a VFO. The 6.00MHz, 6.50MHz and 8.00MHz resonators would require one additional division.
- The deluxe version of it all would be a DDS for the range 2.8672MHz to 4.6592MHz. I wonder is there is any kit in which the LO offset can be easily programmed to (f/256)+460800Hz. Maybe a project with the DDS60 board.
As to receiving, the 11.2kHz to 18.2kHz is in the comfort zone of any 48kbps sampling sound card.
There you have it, my presently preferred solution for the new 600m amateur radio band.
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
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.
Friday, September 23, 2011
New Item in the Marine Radio Collection
Could not stop myself from buying an "Emergency Radio Type 610". I believe it is made by Clifford & Snell, but I am not sure about that.
The radio services the frequencies 500kHz (RX/TX), 2182kHz (RX/TX) and 8364kHz (TX). As in this sort of package, cranks are provided as a power source.
The transmitter seem to be built around two electron tubes (have not checked the types yet), while the receiver seem to employ OC transistors, Germanium that is.
Whilst test TXing into the built-in dummy load, on 2182kHz (A3E), the antenna current meter nicely peaks when the matching variometer (coil with dive-in ferrite rod) is agitated. The two other frequencies would require the operator to have a third arm!?? My radio was supplied with the emergency instructions, which showed one operator only, even the text referred to a single operator doing the cranks and the communications all at once. Who ever wrote this may have never operated a radio himself. While in A3E, a carrier in generated anyway. One hand operating the crank, the other to tune the variometer, no problems here.
It is a different story with 500kHz and 8364kHz. Those are A2A frequencies. No, there is not typoe, A2A it is, AF modulated code. And yes, that makes sense. The signal is received in both, an AM receiver as well as a receiver employing a BFO. However, when tuning the emergency transmitter, one would need one arm/hand operating the crank for energy, a second arm/hand for operating the manual key and a third arm/hand for operating the tuning knob.
The makers of the radio seemed to have spent some thought on this issue, although, maybe not enough. The radio is equipped with a mechanical auto-keyer. Keying the transmitter for tuning can therefore be done, sort of, without three arms. However, the designers seemed to never had the code operator in mind. The built-in manual key is so close to the position of the cranks, that operating both at the same time seems to be a challenge per se. However, if that was your option to survive at sea, that what you would be going for.
Enough about the transmitter, lets have a word on the aerial system provided. A system which managed to impress me. As in all of those sets, the aerial is contained in the box itself. Motto: if your vessel is sinking, throw the emergency radio overboard, get in the life raft and hope for the best. Hence, the floating waterproof box of the emergency radio has to contain everything required to perform emergency communication, including the aerial.
The 610 comes with an antenna base, about 1m long, having a rubber foot (for not damaging the life raft's soft bottom). On this foot, a stainless steel telescopic whip is to be mounted, the whip having an impressive length of estimated 4m (maybe more).
To the downside, and the reason why this radio is not widely available.
In order to keep it smaller, I presume, the designers choose to have a low profile for the cranks. Fair enough... however, they put the cranks so low that they can't be used when the radio laying perfectly flat on the ground. A problem that the very similar TRP1 does not have. Is the TRP1 really as similar? Maybe not... think of it, the TRP1 uses TTL circuits, whilst the 610 employs electron valves and Germanium transistors...
Do I regret having bought on of the 610s? No! Would I buy another one? No!
What is the best thing about the type 610? The aerial provided. I believe, there is no other (convenient) way to get your hands on stuff alike... Think of it!
73!
The radio services the frequencies 500kHz (RX/TX), 2182kHz (RX/TX) and 8364kHz (TX). As in this sort of package, cranks are provided as a power source.
The transmitter seem to be built around two electron tubes (have not checked the types yet), while the receiver seem to employ OC transistors, Germanium that is.
Whilst test TXing into the built-in dummy load, on 2182kHz (A3E), the antenna current meter nicely peaks when the matching variometer (coil with dive-in ferrite rod) is agitated. The two other frequencies would require the operator to have a third arm!?? My radio was supplied with the emergency instructions, which showed one operator only, even the text referred to a single operator doing the cranks and the communications all at once. Who ever wrote this may have never operated a radio himself. While in A3E, a carrier in generated anyway. One hand operating the crank, the other to tune the variometer, no problems here.
It is a different story with 500kHz and 8364kHz. Those are A2A frequencies. No, there is not typoe, A2A it is, AF modulated code. And yes, that makes sense. The signal is received in both, an AM receiver as well as a receiver employing a BFO. However, when tuning the emergency transmitter, one would need one arm/hand operating the crank for energy, a second arm/hand for operating the manual key and a third arm/hand for operating the tuning knob.
The makers of the radio seemed to have spent some thought on this issue, although, maybe not enough. The radio is equipped with a mechanical auto-keyer. Keying the transmitter for tuning can therefore be done, sort of, without three arms. However, the designers seemed to never had the code operator in mind. The built-in manual key is so close to the position of the cranks, that operating both at the same time seems to be a challenge per se. However, if that was your option to survive at sea, that what you would be going for.
Enough about the transmitter, lets have a word on the aerial system provided. A system which managed to impress me. As in all of those sets, the aerial is contained in the box itself. Motto: if your vessel is sinking, throw the emergency radio overboard, get in the life raft and hope for the best. Hence, the floating waterproof box of the emergency radio has to contain everything required to perform emergency communication, including the aerial.
The 610 comes with an antenna base, about 1m long, having a rubber foot (for not damaging the life raft's soft bottom). On this foot, a stainless steel telescopic whip is to be mounted, the whip having an impressive length of estimated 4m (maybe more).
To the downside, and the reason why this radio is not widely available.
In order to keep it smaller, I presume, the designers choose to have a low profile for the cranks. Fair enough... however, they put the cranks so low that they can't be used when the radio laying perfectly flat on the ground. A problem that the very similar TRP1 does not have. Is the TRP1 really as similar? Maybe not... think of it, the TRP1 uses TTL circuits, whilst the 610 employs electron valves and Germanium transistors...
Do I regret having bought on of the 610s? No! Would I buy another one? No!
What is the best thing about the type 610? The aerial provided. I believe, there is no other (convenient) way to get your hands on stuff alike... Think of it!
73!
Thursday, January 13, 2011
NE612 Transverter
Something I found on the internet and would like to share:
http://www.geocities.jp/ja6hic/rig/6/trans.gif
I have seen NE612 transverters before, those were using two NE612s. JA6HIC uses one chip for both RX and TX conversion. The rest of the design involves an external LO.
The circuit is fed by RX and TX control voltages, this may be handy in places, although I believe that this is merely a remainder of JA6HIC's earlier designs involving diode mixers.
However, I believe a running the transverter from the general supply could be advantageous in particular since there could be a delay between powering down the RX and powering up the TX trains, which could cause the circuit not being supplied and therefore shut down. Using an external LO, it would not matter to shut down the transverter for a moment. However, the NE612 has got an internal oscillator, when using this, we certainly would not like to power down the chip just to power it up again... this would result in terrible chirp.
So, this is my plan: make use of this very simple but elegant design for transverters for 136kHz, 501kHz and 70MHz. I will be using the internal oscillator of the NE612 as a crystal oscillator. The following obvious options will be available cheaply (the mark (-) indicated subtractive mixing which inverts the band, (*) indicates my preference):
http://www.geocities.jp/ja6hic/rig/6/trans.gif
I have seen NE612 transverters before, those were using two NE612s. JA6HIC uses one chip for both RX and TX conversion. The rest of the design involves an external LO.
The circuit is fed by RX and TX control voltages, this may be handy in places, although I believe that this is merely a remainder of JA6HIC's earlier designs involving diode mixers.
However, I believe a running the transverter from the general supply could be advantageous in particular since there could be a delay between powering down the RX and powering up the TX trains, which could cause the circuit not being supplied and therefore shut down. Using an external LO, it would not matter to shut down the transverter for a moment. However, the NE612 has got an internal oscillator, when using this, we certainly would not like to power down the chip just to power it up again... this would result in terrible chirp.
So, this is my plan: make use of this very simple but elegant design for transverters for 136kHz, 501kHz and 70MHz. I will be using the internal oscillator of the NE612 as a crystal oscillator. The following obvious options will be available cheaply (the mark (-) indicated subtractive mixing which inverts the band, (*) indicates my preference):
- 136kHz: 2.000MHz - 160m band (-)
- 136kHz: 2.048MHz - 160m band (-)
- 136kHz: 3.500MHz - 80m band
- 136kHz: 3.579MHz - 80m band
- 136kHz: 3.686MHz - 80m band (-)
- 136kHz: 7.000MHz - 40m band
- 136kHz: 7.159MHz - 40m band (-)
- 136kHz: 10.000MHz - 30m band (*)
- 136kHz: 14.000MHz - 20m band
- 136kHz: 14.318MHz - 20m band (-)
- 136kHz: 27.000MHz - 11m band
- 501kHz: 2.458MHz - 160m band (-)
- 501kHz: 3.000MHz - 80m band (*)
- 501kHz: 3.072MHz - 80m band
- 501kHz: 3.276MHz - 80m band
- 501kHz: 4.096MHz - 80m band (-)
- 501kHz: 4.194MHz - 80m band (-)
- 501kHz: 6.5536MHz - 40m band
- 501kHz: 13.560MHz - 20m band
- 501kHz: 14.745MHz - 20m band (-)
- 70.0MHz: 20.000MHz - 6m band (*)
Sunday, December 19, 2010
600m QRP TX at the Plumbtenna - VFO Range
Did some additional soldering on the 600m QRP TX, which is now foreseen with a BNC antenna socket. Hooked up the Plumbtenna (matching&coupling details) and just went for it.
The first tests, once again, were done indoors, from the ground floor.
Lots of plasma TV lines. It seems clear that the Plumbtenna actually radiates, at least a little bit. The HF3's AGC is clearly pulled (ant: Octoplumb, 2 stories higher). I did a little keying, nothing of significance though.
The spectrum indicate a VFO range from just below 501kHz to 503.2kHz. Fingers crossed that this will fall into the range (hopefully) to be assigned to radio amateur at the WRC12.
The first tests, once again, were done indoors, from the ground floor.
Lots of plasma TV lines. It seems clear that the Plumbtenna actually radiates, at least a little bit. The HF3's AGC is clearly pulled (ant: Octoplumb, 2 stories higher). I did a little keying, nothing of significance though.
The spectrum indicate a VFO range from just below 501kHz to 503.2kHz. Fingers crossed that this will fall into the range (hopefully) to be assigned to radio amateur at the WRC12.
Friday, December 17, 2010
600m QRP TX update
It is about time to hurry up. Just a few more days and my 600m permit will have expired. As my energy slowly seems to be returning (don't ask what drained it - the regular reader may have a clue though), my soldering iron heats up more regularly. Today, the last drips of solder are dropped and the 600m exciter (see earlier post) has been given a "power stage", namely a 74HC240 operated at 8V.
Just applied some power, no keying yet... neither an aerial, just a few centimeters of wire. Still my grabber's AGC was pulled (tx-ing from ground floor through two reinforced concrete ceilings).
The spectrum shows DI2AM at 505180Hz. The signal at 503200Hz (1955z) would be me testing.
The HC240 developed slightly elevated temperature. I guess this is normal when running it at 8V. I said, the signal was not keyed, and it wasn't, however, I was handling the PCB, feeling temperature etc, hence the variation in signal strength.
I hope that, later 2nite, I will have hooked up a QRSS keyer to the transmitter and have it wired up to an aerial (I figure that will be the original Plumbtenna).
Just applied some power, no keying yet... neither an aerial, just a few centimeters of wire. Still my grabber's AGC was pulled (tx-ing from ground floor through two reinforced concrete ceilings).
The spectrum shows DI2AM at 505180Hz. The signal at 503200Hz (1955z) would be me testing.
The HC240 developed slightly elevated temperature. I guess this is normal when running it at 8V. I said, the signal was not keyed, and it wasn't, however, I was handling the PCB, feeling temperature etc, hence the variation in signal strength.
I hope that, later 2nite, I will have hooked up a QRSS keyer to the transmitter and have it wired up to an aerial (I figure that will be the original Plumbtenna).
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, 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
Monday, April 12, 2010
Ten Tec SCOUT/ARGO Modules for 600m?
Having both radios, the Ten Tec SCOUT 555, for more than 10 yrs by now, and the ARGO 556 ( = SCOUT w/o the P.A.) which I was lucky to obtain some months ago, a thought came to me if the transceivers modules could be modified for 500kHz or even 136kHz.
In principle nothing should speak against this. The SCOUT uses an I.F. of 6.144, the L.O. is generated by a 2.2MHz PTO signal, mixed to and by a NE612 XO/mixer in the band modules.
For 80m that means: 7.444 (XO) + 2.2 (PTO) - 6.144 (I.F.) = 3.500 (QRG)
This would mean for 500kHz: 4.444 (XO) + 2.2 (PTO) - 6.144 (I.F.) = 0.500 (QRG)
It would be necessary not only to replace the crystal but also the LO filter network.
The 160m module can be tuned to about 1.5MHz, however, the PTO stabilizing aka FLS (frequency lock system) does not lock in anymore, Ten-Tec mention here that the AM band rejection in the 160m module would be causing this.
Since the modules also carry the band filter, it seems that no modification to the radio itself is required.
Now we've seen that 4.444MHz is the highest usable local oscillator frequency. So, what crystal will be available and where would the lower band edge will be?
In principle nothing should speak against this. The SCOUT uses an I.F. of 6.144, the L.O. is generated by a 2.2MHz PTO signal, mixed to and by a NE612 XO/mixer in the band modules.
For 80m that means: 7.444 (XO) + 2.2 (PTO) - 6.144 (I.F.) = 3.500 (QRG)
This would mean for 500kHz: 4.444 (XO) + 2.2 (PTO) - 6.144 (I.F.) = 0.500 (QRG)
It would be necessary not only to replace the crystal but also the LO filter network.
The 160m module can be tuned to about 1.5MHz, however, the PTO stabilizing aka FLS (frequency lock system) does not lock in anymore, Ten-Tec mention here that the AM band rejection in the 160m module would be causing this.
Since the modules also carry the band filter, it seems that no modification to the radio itself is required.
Now we've seen that 4.444MHz is the highest usable local oscillator frequency. So, what crystal will be available and where would the lower band edge will be?
- 4.433MHz => 489kHz
- 4.194MHz => 250kHz
- 4.096MHz => 152kHz
- 4.000MHz => 56kHz
Wednesday, March 31, 2010
TECSUN AN-100
The AN-100 dropped in today. TECSUN produces two slightly different MF multi-turn loop aerials for BC-receivers, the AN-100 and the more popular AN-200. My impression, it's just a matter of design. The AN-200 rests on a stylish arc-like stand, while the AN-100 is held by a rather non-stylish foot.
My preference was the AN-100, since I believed that the foot could be opened by a bottom plate, it seemed better suited for modifications. And, the dear reader may have a guess... I was guessing correctly. Underneath 4 rubber-foam pads, 4 screws allow access to the inside of the AN-100's stand.
Surprise surprise, the foot contains a polyvaricon, actually one of the type that is found in any random cheap broadcast receiver. The trick with those is, they employ little trimmers for basic frequency setting.
The modification to resonate the loop at 500kHz was consequently a simple one. One of the polyvaricon's trimmers was not set to maximum but rather to some odd looking position. Obviously that's the one to change. Well, guess what, I did just that, and the lowest resonance of the loop dropped to 494kHz.
Now, that was a simple one, no solder molten.
To drop the frequency even lower, solder needs to be molten. I figure a high quality, e.g. polystyrene, 47pF capacitor parallel to the tuning capacitor will do the trick.
UPDATES:
The most upper resonance frequency is now 1330kHz.
The combination AN-100 & ATS-909 let me presently listen regular CW-QSOs.
Plenty of space in the compartment. Here are some ideas of what could be fit into this space:
 |
| AN-100 from below |
My preference was the AN-100, since I believed that the foot could be opened by a bottom plate, it seemed better suited for modifications. And, the dear reader may have a guess... I was guessing correctly. Underneath 4 rubber-foam pads, 4 screws allow access to the inside of the AN-100's stand.
 |
| screws underneath pads |
 |
| tuning capacitor |
Now, that was a simple one, no solder molten.
To drop the frequency even lower, solder needs to be molten. I figure a high quality, e.g. polystyrene, 47pF capacitor parallel to the tuning capacitor will do the trick.
UPDATES:
The most upper resonance frequency is now 1330kHz.
The combination AN-100 & ATS-909 let me presently listen regular CW-QSOs.
 |
| inside the foot |
- a preamp
- an I/Q-SDR receiver
- a (subharmonic) grabber receiver w/ a USB sound-device, USB powered
Thursday, March 18, 2010
600m Transverter
The plan has been around for a while, ah well, since January, to build a transverter or at least a TX converter for HF to MF. Some ideas came along, some back a forth struggle, but finally, I soldered some components together. I have to admit, this design is not yet (!) tested.
This resembles a regular XOR Pierce crystal oscillator with an additional XOR for pulse shaping. As "filter and matching network", a second crystal is used. The drive level for the subharmonic mixer is adjusted by R3.
CR1 is a ceramic resonator for 500kHz. One could image to arrange a capacitors in series with it in order to pull up the resonator's response slightly.
In my junk box, there seems no indication for a 28.5MHz crystal, therefore, I consider using a regular LC resonant circuit, which is not yet figured out however.
CR1 is a ceramic resonator for 500kHz. One could image to arrange a capacitors in series with it in order to pull up the resonator's response slightly.
In my junk box, there seems no indication for a 28.5MHz crystal, therefore, I consider using a regular LC resonant circuit, which is not yet figured out however.
Wednesday, March 10, 2010
500kHz - AR3030 vs FRG-100
Did some testing lately, in order to see which of the receivers has got the edge. This book: LF Today: A Guide to Success on 136 and 500kHz
indicates that the FRG-100 is seen as being as good as the TS-850. However, the TS-850 is attenuated from 500kHz upwards. The remarks in said book made me to buy a Yaesu FRG-100 some months ago. Prior to that I was able to ebay an AOR AR3030. The AR3030 gave good initial results on the Plumbtenna and the Octaplumb. But what a about a comparison?
In direct comparison the AR3030 gave a WSPR SNR 2dB above the FRG-100. So much to noise. But here comes some more.
In order to keep the receiver isolated from the soundcard, I was using a 1:1 audio transformer in the line. With good success on the Target HF3, which otherwise would have been totally useless.
When using the AR3030, I used the above mentioned cable with no further visible effects. A spectrum made at that time looked like that:
Some QRM, some WSPR, G3ZJO's MEPT, DI2AM, and some unknown signals. The SSB filter slightly kicks in on the upper range, but other than that, the spectrum looks quite "flat". Aerial at the time: Octaplumb.
And that's what the FRG-100 sees, (slightly different condx though) using the same aerial and audio cable:
The SSB filter (still set to 2.4kHz b.w.) cuts somewhat deeper, ok, but what is that bright range at 1.1kHz audio frequency??? I lived with it for a while. BTW, G3ZJO's WSPR at 2300z decoded with a SNR of -19dB, the strongest yet. Other than that, the typical signals are shown... but again, what is that elevated band at 1.1kHz?
As I have seen that Jan PA9QV, also using a FRG-100 meanwhile, does not see anything similar to that, I started looking for culprits. My first guess was the correct one, finally some luck in life. The isolating audio cable, that worked so well with the HF3 did it. Having it replaced now with a regular one (which came with a computer screen once), the sound-card now receives this audio:
A flat response, as received from the AR3030 with the isolation cable. Hmmm, it appears to me, that the "rec out" of the FRG-100 comprises some capacitance that, in combination with the inductance of the audio transformer, leads to a 1.1kHz resonance. Maybe useful to know, but not useful for a wide-band grabber. I could consider making use of that effect when going narrow-band at 1.1kHz audio.
Additionally, but this is not linked to the 1.1kHz issue, I widened the FRG-100's i.f.-filter to 6kHz.
BTW, the condx at time of that reception was very favorable in a NE direction. For the first time I received Radio Rud SK6RUD at 0233z.
indicates that the FRG-100 is seen as being as good as the TS-850. However, the TS-850 is attenuated from 500kHz upwards. The remarks in said book made me to buy a Yaesu FRG-100 some months ago. Prior to that I was able to ebay an AOR AR3030. The AR3030 gave good initial results on the Plumbtenna and the Octaplumb. But what a about a comparison?In direct comparison the AR3030 gave a WSPR SNR 2dB above the FRG-100. So much to noise. But here comes some more.
In order to keep the receiver isolated from the soundcard, I was using a 1:1 audio transformer in the line. With good success on the Target HF3, which otherwise would have been totally useless.
When using the AR3030, I used the above mentioned cable with no further visible effects. A spectrum made at that time looked like that:
And that's what the FRG-100 sees, (slightly different condx though) using the same aerial and audio cable:
As I have seen that Jan PA9QV, also using a FRG-100 meanwhile, does not see anything similar to that, I started looking for culprits. My first guess was the correct one, finally some luck in life. The isolating audio cable, that worked so well with the HF3 did it. Having it replaced now with a regular one (which came with a computer screen once), the sound-card now receives this audio:
Additionally, but this is not linked to the 1.1kHz issue, I widened the FRG-100's i.f.-filter to 6kHz.
BTW, the condx at time of that reception was very favorable in a NE direction. For the first time I received Radio Rud SK6RUD at 0233z.
Saturday, March 6, 2010
Notes
A couple of notes, not worth an individual entry, however interesting enough to share.
Changed from AR3030 to FRG-100, same aerial (Octaplumb), same computer, same software... (had to change the spectrumlab settinga bit). As a result, the AR3030 seems a have a 2dB SNR advantage over the FRG-100. This is the result from receiving G4JNT's WSPRing.
2.5mm² speaker cable is nice, works well in the Plumbtenna and the Octaplumb. I choose 2.5mm² because it was relatively cheap at a certain store. The same store also offers heavier gauge speaker cable, not precut, and somewhat more expensive. Namely 4mm² with red & black insulation for €1.79/m. Bought 10m for the outdoor TX loop.
Fillable sunshade stands make pretty good frame-antenna foots, indoors even when used empty. The frame can easily be rotated independently.
Plasma TVs suck!
Changed from AR3030 to FRG-100, same aerial (Octaplumb), same computer, same software... (had to change the spectrumlab settinga bit). As a result, the AR3030 seems a have a 2dB SNR advantage over the FRG-100. This is the result from receiving G4JNT's WSPRing.
2.5mm² speaker cable is nice, works well in the Plumbtenna and the Octaplumb. I choose 2.5mm² because it was relatively cheap at a certain store. The same store also offers heavier gauge speaker cable, not precut, and somewhat more expensive. Namely 4mm² with red & black insulation for €1.79/m. Bought 10m for the outdoor TX loop.
Fillable sunshade stands make pretty good frame-antenna foots, indoors even when used empty. The frame can easily be rotated independently.
Plasma TVs suck!
Wednesday, March 3, 2010
ATS 909 vs AR3030
The Sangean ATS 909 is not a bad receiver, actually, I believe for the priece, it is a very good receiver. But, how good is it?
To find out, I did the following test:
It seems, the AR3030 has got a 11dB advantage in SNR over the ATS 909. In other words, the relatively inexpensive ATS 909 is just 11dB short (in SNR) to one of the world's finest receivers.
To find out, I did the following test:
- run the ATS 909 with the Octaplumb
- run the AR3030 with the Octaplumb
At the same frequency, measuring SNR (using WSPR) of stations receivable via ground wave.
On 600m, that was the result:
| 2010-03-03 21:26 | G4JNT | 0.503884 | -11 | IO90iv | PA1GSJ | 406 | ||||
| 2010-03-03 21:22 | PA3EGO | 0.503927 | +10 | JO22mb | PA1GSJ | 52 | ||||
| 2010-03-03 21:14 | G4JNT | 0.503881 | -22 | IO90iv | PA1GSJ | 406 | ||||
| 2010-03-03 21:14 | PA3EGO | 0.503923 | -1 | JO22mb | PA1GSJ | 52 |
It seems, the AR3030 has got a 11dB advantage in SNR over the ATS 909. In other words, the relatively inexpensive ATS 909 is just 11dB short (in SNR) to one of the world's finest receivers.
Sunday, February 28, 2010
Q-RX - a 600m Receiver Concept
When searching the internet, I found the QTX by GW3UEP. The exciter of this transmitter uses Q4 (pin 7) of a 4060 ripple counter. Q4 is the lowest division available with the 4060, hence, an 8.0MHz ceramic resonator needs to be used to generate a 500kHz frequency. The nice thing about the 4060 is its' internal oscillator.
So, here is the concept for a 600m receiver. Use a 4060 in the way as it is shown for the QTX. Generate a 250Hz frequency with it as a LO for a subharmonic mixer.
There are two obvious options to do that:
In this receiver, I intend to employ a 500kHz ceramic resonator as sideband filter, provided it can be slightly pulled up by a series capacitor.
So, here is the concept for a 600m receiver. Use a 4060 in the way as it is shown for the QTX. Generate a 250Hz frequency with it as a LO for a subharmonic mixer.
There are two obvious options to do that:
- 8.0MHz ceramic resonator - Q5 (pin 5)
- 4.0MHz ceramic resonator - Q4 (pin 7)
For a grabber, I would even consider using a 4.000MHz crystal for increased stability. The resulting audio signal will fall into the range of 1kHz to 4kHz (5.x for inclusion of the DI2AM).
In this receiver, I intend to employ a 500kHz ceramic resonator as sideband filter, provided it can be slightly pulled up by a series capacitor.
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