Yes, they pull the crystal frequencies quite a bit - the most I needed to pull was 2.335KHz for the 13MHz crystal, and I found that more than this was easily obtained. I used a combination of a silver mica capacitor and 30pF poly trimmer in parallel for the series capacitor. The value of the silver mica capacitor was selected for each crystal such that the desired frequency was reached around mid-span of the trimmer. The values of the silver mica capacitors used here range from 33PF to 82pF. The correct value in each case was reached by experiment using a larger value trimmer on its own to start with, adjusting to the desired frequency, removing it from the circuit and measuring the trimmer value, subtracting 15pF from the measured value, and using the closest standard silver mica capacitor value. I also checked if they could be pulled in the opposite direction using a capacitor in parallel, and they could. Of course inductors could also be used instead of the capacitors, to give the opposite effect
The lower 10 meters is dead on my KWS-1. I have no carrier. Howard Mills told me likely the crystal is dead or drifted too far. I see you made a mod to pull your xtals. Are they still obtainable? Could I merely replace mine for that band? (If that’s my issue. I’m not certain yet)
In my experience, replacing a crystal is not as straightforward as it seems (whether series or parallel resonance, and correct loading must match the original for it to resonate at the correct frequency). All the crystals in this KWS-1 had drifted low of their original frequencies (most crystals drift lower in frequency with age), hence the adapters I made to correct the ones installed in this transmitter. I did look into obtaining new HC6/U (HC/48/U) crystals and they can be obtained new and used - cost around $50 each for a new one 'ground to order', eg. from Klove in the Netherlands (they quoted me 37.5 Euros and a lead time of 5-6 weeks). Vince Jakomin in the UK may have one in stock at a lower price.
Sorry to say but I cannot hear you clearly! could you get a lapel microphone or one that goes right in front of your mouth? I also have a KWS-1 and it recently developed a problem with suddenly going into oscillation mode drawing high PA current which i turned high voltage off immediately. I suspect neutralization problem and will be checking that situation shortly! How well does those trimmers work at the base of the crystals? are they wires in series with the crystals or parallel with the crystals? and what is the effect on the crystal, does it allow more adjustment on the crystal frequency or less? Many thanks ahead of time. John A Bellas at KC2UVN
Hi John. Strange - the audio sounds ok on this video to me (maybe its my northern UK accent!). Good suggestion on a lapel mic though - I will check out what is available for use with an iPhone, maybe with a noise cancelling feature, as the videos of the KWS-1 with the blower running do have an audio issue(!). I agree that the problem you are experiencing with your KWS-1 is likely due to poor neutralization in either the driver and/or PA stage. I found some of the neutralization steps as described in the KWS-1 manual to be ineffective and I had to re-neutralize both the PA stage and driver stage grid-cathode, the latter when fully powered-up with the driver stage oscillating. There is an article on the Collins Association website that describes alternative neutralizing procedures for the KWS-1 here: collinsradio.org/wp-content/uploads/2015/05/KWS-1-Neutralization-Notes-from-W8MAQ.pdf. Also, my detailed article on refurbishing this KWS-1 can be downloaded from the SPARC radio museum website here: sparcradio.ca/wp-content/uploads/2024/09/Gold-Dust-Twins-Refurbishing-the-KWS-1-Transmitter-and-Power-Supply.with-Appendix.pdf, which describes the issues I encountered. The HF crystal trimmer adapters I made work well, though I suspect that in a couple of cases the amount of 'pulling' degraded the crystal activity somewhat, reducing the HF oscillator output and hence the available drive level on a couple of the bands. The series trimmers allow the crystal frequency to be pulled up and parallel trimmers allow the frequency to be pulled down. Inductors have the opposite effect. The amount of pulling achievable depends on the characteristics of the individual crystals, its operating mode, eg. fundamental or 3rd harmonic/series or parallel resonance, and the circuit it is operating in (level of capacitance loading, etc). Usually, a crystal operating at its fundamental frequency can be pulled a few KHz using a trimmer or inductor.
W bardzo ładnym stanie radio. Pozdrawiam
Thanks!- yes, its in very nice condition for an (almost) 70 year old!
Beautiful set, good work. Do those crystal series trimmers give you much margin?
Yes, they pull the crystal frequencies quite a bit - the most I needed to pull was 2.335KHz for the 13MHz crystal, and I found that more than this was easily obtained. I used a combination of a silver mica capacitor and 30pF poly trimmer in parallel for the series capacitor. The value of the silver mica capacitor was selected for each crystal such that the desired frequency was reached around mid-span of the trimmer. The values of the silver mica capacitors used here range from 33PF to 82pF. The correct value in each case was reached by experiment using a larger value trimmer on its own to start with, adjusting to the desired frequency, removing it from the circuit and measuring the trimmer value, subtracting 15pF from the measured value, and using the closest standard silver mica capacitor value. I also checked if they could be pulled in the opposite direction using a capacitor in parallel, and they could. Of course inductors could also be used instead of the capacitors, to give the opposite effect
The lower 10 meters is dead on my KWS-1. I have no carrier. Howard Mills told me likely the crystal is dead or drifted too far. I see you made a mod to pull your xtals. Are they still obtainable? Could I merely replace mine for that band? (If that’s my issue. I’m not certain yet)
In my experience, replacing a crystal is not as straightforward as it seems (whether series or parallel resonance, and correct loading must match the original for it to resonate at the correct frequency). All the crystals in this KWS-1 had drifted low of their original frequencies (most crystals drift lower in frequency with age), hence the adapters I made to correct the ones installed in this transmitter. I did look into obtaining new HC6/U (HC/48/U) crystals and they can be obtained new and used - cost around $50 each for a new one 'ground to order', eg. from Klove in the Netherlands (they quoted me 37.5 Euros and a lead time of 5-6 weeks). Vince Jakomin in the UK may have one in stock at a lower price.
Sorry to say but I cannot hear you clearly! could you get a lapel microphone or one that goes right in front of your mouth? I also have a KWS-1 and it recently developed a problem with suddenly going into oscillation mode drawing high PA current which i turned high voltage off immediately. I suspect neutralization problem and will be checking that situation shortly! How well does those trimmers work at the base of the crystals? are they wires in series with the crystals or parallel with the crystals? and what is the effect on the crystal, does it allow more adjustment on the crystal frequency or less? Many thanks ahead of time. John A Bellas at KC2UVN
Hi John. Strange - the audio sounds ok on this video to me (maybe its my northern UK accent!). Good suggestion on a lapel mic though - I will check out what is available for use with an iPhone, maybe with a noise cancelling feature, as the videos of the KWS-1 with the blower running do have an audio issue(!). I agree that the problem you are experiencing with your KWS-1 is likely due to poor neutralization in either the driver and/or PA stage. I found some of the neutralization steps as described in the KWS-1 manual to be ineffective and I had to re-neutralize both the PA stage and driver stage grid-cathode, the latter when fully powered-up with the driver stage oscillating. There is an article on the Collins Association website that describes alternative neutralizing procedures for the KWS-1 here: collinsradio.org/wp-content/uploads/2015/05/KWS-1-Neutralization-Notes-from-W8MAQ.pdf. Also, my detailed article on refurbishing this KWS-1 can be downloaded from the SPARC radio museum website here: sparcradio.ca/wp-content/uploads/2024/09/Gold-Dust-Twins-Refurbishing-the-KWS-1-Transmitter-and-Power-Supply.with-Appendix.pdf, which describes the issues I encountered. The HF crystal trimmer adapters I made work well, though I suspect that in a couple of cases the amount of 'pulling' degraded the crystal activity somewhat, reducing the HF oscillator output and hence the available drive level on a couple of the bands. The series trimmers allow the crystal frequency to be pulled up and parallel trimmers allow the frequency to be pulled down. Inductors have the opposite effect. The amount of pulling achievable depends on the characteristics of the individual crystals, its operating mode, eg. fundamental or 3rd harmonic/series or parallel resonance, and the circuit it is operating in (level of capacitance loading, etc). Usually, a crystal operating at its fundamental frequency can be pulled a few KHz using a trimmer or inductor.