[Elecraft] Re: K1 on 10 meters: helpful advice
Hi Wayne, Thanks very much for the additional information! Most of my guestimated values for the 2-band board seem to match those that were in the email you sent; the only ones I was way off on were C16 C20. I actually found a cheap source of fundamental 36MHz crystals. They're about $4.00 each, the only catch is they're surface-mount. I just solder leads on them and use them in the normal crystal mounting holes. Yesterday I was at work most of the day with a lot of time to think and surf the net, and found one email that I'd missed in my earlier research: http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-06/ msg00789.html Based on that email, I reduced the value of RF-R11 from 82 ohms to 33 ohms. I now get up to almost 3 watts out on 10 meters. I'll have a go at adding the L-network at J7-P8 as described in the email you provided and see if that improves things any further. I also went a little crazy last night with experimentation, and decided to have a shot at my 'ideal' 4-band filter board: 80 / 40 / 20 / 10 meters. I've got a design in mind to provide 4 separate low- pass filters, but it will mean some drastic surgery to the filter board, and I won't have room for the noise blanker any more. As it stands now, on the test bench, I have a full 5 watts output on 80, 40, and 20 meters, and 2 to 3 watts on 10 meters. The board's two existing low pass filters are set-up for 40 and 10 meters. So while I can currently listen on all four bands, I won't be transmitting on 80 or 20 just yet. The key for me though is, I know what is required, what the values are, and have a good idea how to lay it out physically, so basically I know it's possible. Thanks again for the info and suggestions! Happy holidays and 73 de Stephanie Maks va3uxb On 26-Dec-2005, at 14.44.01, wayne burdick wrote: Stephanie (and other interested parties), I have some additional thoughts on modifying the K1 for 10 meters. I also found some old e-mail from another customer who attempted it. Between the two, I believe you'll be able to do this successfully. When I designed the Norcal/Wilderness Sierra, which uses the same I.F. as the K1, I realized that a 36-MHz crystal would be expensive, so I came up with an alternate mixing scheme where the LO is below the band rather than above it. The RX and TX image rejection isn't quite as good with this technique, but that probably doesn't matter since the band-pass filters are narrow. Here's the normal conversion scheme (high-side injection): RF 28.000 - 28.100 + IF4.915 = LO 32.915 - 33.015 + VFO3.085 - 2.985 = XO 36.000 Here's the alternate scheme using low-side injection: RF 28.000 - 28.100 - IF4.915 = LO 23.085 - 23.185 + VFO3.085 - 2.985 = XO 26.170 I.e., you can use a 26.170 MHz fundamental crystal. Advantages of this frequency vs. 36 MHz include: (1) more power output from the NE602 premixer oscillator; (2) cheaper; (3) possibly available from Wilderness Radio. If Wilderness doesn't have any, you might try ICM. I think the ICM part number for the basic crystal type (not including frequency) would be #436162. Low-side injection results in one additional minor issue: the sideband gets inverted. This just means that the CW pitch will change in the opposite way from the other bands as you tune. VFO readings should still be accurate. Looking back through old K1 design notes, I found an e-mail from another customer (Bob Larkin, [EMAIL PROTECTED]) who put his K1 on 10 meters. He used an overtone 36 MHz oscillator, requiring changes to the basic band module. A 26.17-MHz crystal would be simpler, as I described above. But Bob's notes on getting adequate power output on this band are quite useful. I have attached them below. Let me know if you try this! If we have a couple of customers successfully complete the mods, we'll offer it as an option kit for use with the 2-band module. 73, Wayne N6KR * * * The RF filter was designed to have 2.2 dB IL in 50 Ohms and has 3 and 40 dB bandwidths of 1.8 and 18.5 MHz. Inductor were the regular 1 uH. C16=C20=270 pF, C17=C19=33 pF, C18=1.5pF (if the latter is not available, use 0.75 inches of the gimmick capacitor). The LPF is an interesting topic. I did not try a direct scaling of the other filters. This might work adequately, and would be good for someone to try. Instead I designed a 2-coil modified elliptic filter. The goal was to move the cutoff frequency far enough above 28 MHz to minimize the insertion loss, and to put an elliptic null at the second harmonic, 56 MHz. The final design cutoff at 34.9 MHz and had a measured insertion loss of 0.17 dB at 28 MHz and 65 dB at 56 MHz. L11 is 0.28uH (9T T37-6, over 75%), L12 is 0.22uH (7T T37-6, tight wound--probably should
Re: [Elecraft] Re: K1 on 10 meters: helpful advice
Keep us posted on this guys! I plan ultimately to build a 17/10 meter board. Already have a 160/80 meter board to go with my 40/30/20/15 meter 4 band board. I'm in no rush as it will be a while before 10 gets decent again except for the usual summertime Sporadic E type stuff and the perennial North-South path to South America. I can work the Argentine/Brazilian Venezuelan stations already on 20 or 15 so don't need 10 meters for them! 73, Sandy W5TVW - Original Message - From: Stephanie Maks [EMAIL PROTECTED] To: wayne burdick [EMAIL PROTECTED] Cc: Elecraft Reflector elecraft@mailman.qth.net Sent: Monday, December 26, 2005 3:30 PM Subject: [Elecraft] Re: K1 on 10 meters: helpful advice | Hi Wayne, | | Thanks very much for the additional information! Most of my | guestimated values for the 2-band board seem to match those that were | in the email you sent; the only ones I was way off on were C16 C20. | | I actually found a cheap source of fundamental 36MHz crystals. | They're about $4.00 each, the only catch is they're surface-mount. I | just solder leads on them and use them in the normal crystal mounting | holes. | | Yesterday I was at work most of the day with a lot of time to think | and surf the net, and found one email that I'd missed in my earlier | research: | http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-06/ | msg00789.html | | Based on that email, I reduced the value of RF-R11 from 82 ohms to 33 | ohms. I now get up to almost 3 watts out on 10 meters. I'll have a | go at adding the L-network at J7-P8 as described in the email you | provided and see if that improves things any further. | | I also went a little crazy last night with experimentation, and | decided to have a shot at my 'ideal' 4-band filter board: 80 / 40 / | 20 / 10 meters. I've got a design in mind to provide 4 separate low- | pass filters, but it will mean some drastic surgery to the filter | board, and I won't have room for the noise blanker any more. As it | stands now, on the test bench, I have a full 5 watts output on 80, | 40, and 20 meters, and 2 to 3 watts on 10 meters. The board's two | existing low pass filters are set-up for 40 and 10 meters. So while | I can currently listen on all four bands, I won't be transmitting on | 80 or 20 just yet. The key for me though is, I know what is | required, what the values are, and have a good idea how to lay it out | physically, so basically I know it's possible. | | Thanks again for the info and suggestions! | | Happy holidays and 73 de | Stephanie Maks | va3uxb | | | | On 26-Dec-2005, at 14.44.01, wayne burdick wrote: | | Stephanie (and other interested parties), | | I have some additional thoughts on modifying the K1 for 10 meters. | I also found some old e-mail from another customer who attempted | it. Between the two, I believe you'll be able to do this successfully. | | When I designed the Norcal/Wilderness Sierra, which uses the same | I.F. as the K1, I realized that a 36-MHz crystal would be | expensive, so I came up with an alternate mixing scheme where the | LO is below the band rather than above it. The RX and TX image | rejection isn't quite as good with this technique, but that | probably doesn't matter since the band-pass filters are narrow. | | Here's the normal conversion scheme (high-side injection): | | RF 28.000 - 28.100 | + IF4.915 | | = LO 32.915 - 33.015 | + VFO3.085 - 2.985 | | = XO 36.000 | | | Here's the alternate scheme using low-side injection: | | RF 28.000 - 28.100 | - IF4.915 | | = LO 23.085 - 23.185 | + VFO3.085 - 2.985 | | = XO 26.170 | | I.e., you can use a 26.170 MHz fundamental crystal. Advantages of | this frequency vs. 36 MHz include: (1) more power output from the | NE602 premixer oscillator; (2) cheaper; (3) possibly available from | Wilderness Radio. If Wilderness doesn't have any, you might try | ICM. I think the ICM part number for the basic crystal type (not | including frequency) would be #436162. | | Low-side injection results in one additional minor issue: the | sideband gets inverted. This just means that the CW pitch will | change in the opposite way from the other bands as you tune. VFO | readings should still be accurate. | | Looking back through old K1 design notes, I found an e-mail from | another customer (Bob Larkin, [EMAIL PROTECTED]) who put his K1 | on 10 meters. He used an overtone 36 MHz oscillator, requiring | changes to the basic band module. A 26.17-MHz crystal would be | simpler, as I described above. But Bob's notes on getting adequate | power output on this band are quite useful. I have attached them | below. Let me know if you try this! If we have a couple of | customers successfully complete
