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" <[email protected]> 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 | > + IF 4.915 | > ------------------------ | > = LO 32.915 - 33.015 | > + VFO 3.085 - 2.985 | > ------------------------ | > = XO 36.000 | > | > | > Here's the alternate scheme using low-side injection: | > | > RF 28.000 - 28.100 | > - IF 4.915 | > ------------------------ | > = LO 23.085 - 23.185 | > + VFO 3.085 - 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 be 8T spread out). C24=94 pF | > (two 47 pF | > in parallel, one on top, one under), C25=164 pF (two 82 pF), C26=75 | > pF. The | > capacitors in parallel with the inductors are mounted below the | > board and | > arranged to be flat against the board to clear the bottom board parts. | > Across L11 is 13 pF (two 6.8 pF in parallel), across L12 is 36 pF. | > This is | > quite a few parts, but the measured performance is great. | > | > Now the K1 was on 10-m, but the transmitter didn't put out any | > power! There | > wasn't enough drive to make the Class C Q7 draw current. I made two | > changes | > to fix this. Both of these have the potential to alter the | > performance on | > other bands, particularly 15 and 20-m. I attempted to evaluate these | > effects, but I only have the one K1! Both changes are attempting to | > compensate for the drop in gain of Q6 and Q7 with frequency. My 10-m | > performance seems to still be limited by drive to Q7. | > | > First, U9 has more gain available. I put 270 pF across R11, | > boosting the | > gain on all bands above 40-m. | > | > This produced a fraction of a Watt, but not enough drive, yet. So, I | > measured the impedance looking into pin 8 of J7, in transmit. At 28 | > MHz, | > this was 5+j8 Ohms. So I added an L-network to match this closer to | > 50 Ohms. | > At the J7-P8 side of D9, I inserted a .12uH (6T #32 on T12-6, | > tight) and on | > the J7-8 end put 200 pF to ground. | > | > Now at 13.8 V I get 3W, and at 12V about 1W. All spurs are at least | > 48 dBc. | > | > As a by-product the output on 15-m is easily 7W. The power control | > seems to | > still be able to work fine and on my K1 the spurs were still | > essentially | > where they were on all bands. | > | > | > | > --- | > | > http://www.elecraft.com | > | | _______________________________________________ | Elecraft mailing list | Post to: [email protected] | You must be a subscriber to post to the list. | Subscriber Info (Addr. Change, sub, unsub etc.): | http://mailman.qth.net/mailman/listinfo/elecraft | | Help: http://mailman.qth.net/subscribers.htm | Elecraft web page: http://www.elecraft.com | | | | -- | No virus found in this incoming message. | Checked by AVG Free Edition. | Version: 7.1.371 / Virus Database: 267.14.7/214 - Release Date: 12/23/2005 | | _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. 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