{"id":937,"date":"2012-05-01T15:31:22","date_gmt":"2012-05-01T19:31:22","guid":{"rendered":"http:\/\/w4kaz.com\/qth\/?page_id=937"},"modified":"2016-10-19T17:25:12","modified_gmt":"2016-10-19T21:25:12","slug":"w4kaz-cw-skimmer-03-band-details","status":"publish","type":"page","link":"http:\/\/w4kaz.com\/qth\/?page_id=937","title":{"rendered":"W4KAZ Softrock Based CW Skimmer Station – 03) Band Details"},"content":{"rendered":"
As of 2015-04-02 this information is mostly obsolete and in need of revision,w4kaz<\/span><\/strong><\/address>\n
160m SoftRock Skimmer<\/h5>\n

The 160m skimmer is an original SoftRock 40(donated by N4GU) that was retrofit with a crystal and band pass filter designed for 160m.\u00c2\u00a0 Part values for 160m were substituted based on value specifications in the SoftRock Lite II schematics.\u00c2\u00a0 The 7.3xxMc crystal resulted in the SoftRock center frequency at 1842950Mc.\u00c2\u00a0 The antenna is the NE facing K9AY, fed into a W7IUV preamp and a cascaded magic-T splitter.<\/p>\n

The 160m skimmer is fed off one of the -6db ports of the splitter.\u00c2\u00a0 I\/Q signal is (for now) fed to a ASUS Xonar DS sound card with a 96Kc scan rate mounted in a dual core e2200 dell optiplex 360 minitower.\u00c2\u00a0 The operating system is Windows XP Pro SP3+,\u00c2\u00a0 VE3NEA CW Skimmer, and W3OA’s Aggregator for reporting up to the Reverse Beacon Network.\u00c2\u00a0 Normal operation at the 96Kc bandwidth will provide a useful bandwidth from 1800.0Mc through 1890.5Mc<\/p>\n

80m softrock skimmer<\/h5>\n

The 80m skimmer is a Softrock lite II.\u00c2\u00a0 The crystal used is 14.138Mhz, resulting in the softrock center\u00c2\u00a0 frequency at 3.533950Mhz.\u00c2\u00a0 The antenna is a NE facing K9AY with the feed split three ways following the W7IUV preamp in the shack.\u00c2\u00a0 The splitter is two magic T splitters cascaded.\u00c2\u00a0 The 80m Softrock is on one of the two -6db ports of the splitter. CW skimmer currently running on Dell Optiplex 745SFF, with 80m skimmer on the onboard Realtek sound card.\u00c2\u00a0 Normal operation is at 48khz scan rate, making the scanned range from 3.510.x through 3.557xxMhz.<\/p>\n

40m softrock skimmer<\/h5>\n

The 40m skimmer is a Softrock v6.2.\u00c2\u00a0 This Softrock was re-worked from a 9Mhz IF build.\u00c2\u00a0 It uses a crystal at 28.224Mhz, putting the Softrock center frequency at 7.055015Mhz.\u00c2\u00a0 The antenna is a NE facing K9AY with the feed split three ways following the W7IUV preamp in the shack.\u00c2\u00a0 The splitter is two magic T splitters cascaded.\u00c2\u00a0 The 40m Softrock is on the 3db port not feeding the second cascaded splitter.\u00c2\u00a0 CW skimmer currently running on Dell Optiplex 745SFF, with 40m skimmer on the Asus Xonar DG sound card.\u00c2\u00a0 Normal operation is at 96khz scan rate, making the scanned range from 7.007 through 7.105Mhz.<\/p>\n

20m SoftRock Skimmer<\/h5>\n

** As of 02\/2013 dead, deceased, and otherwise inactive. \u00c2\u00a0 Requires debug\/repair…**<\/strong><\/p>\n

The 20m SoftRock is\/will be the new SoftRock 20R with all surface mount components.\u00c2\u00a0 Its crystal oscillator is at 18.73xx Mc.\u00c2\u00a0 The divide by four gives 4.68xx Mc. In a twist on the plot, for 20m the QSD mixer really uses the third harmonic.\u00c2\u00a0 So its (18.73xx\/4)*3=14.0475xxMc(Actual center=14.04473xMc).\u00c2\u00a0 As the documentation says, the bandpass filter and software is all that really limits the decoding to 20m.\u00c2\u00a0 The 20m RX antenna is[will be] a sloping coaxial\u00c2\u00a0 dipole<\/a>.[NOT a “bazooka”! see: PA0NHC<\/a>].\u00c2\u00a0 This design scales up easily for HF antennas using different materials.<\/p>\n

The W4KAZ 20m RX version of the coaxial dipole will be constructed from a scrap of coax and wire.\u00c2\u00a0 It is fed like an end-fed antenna and with a good choke at the feedpoint works FB, having a feedpoint impedance close to 50 ohms, ie, same as a “normal” center-fed dipole.\u00c2\u00a0 This is one of those antenna ideas I have tested(years ago), and always been wanting to find a good application to put into use.\u00c2\u00a0 It should be FB for an RX only application where the choke components need only handle RX levels – implying inexpensive, small cores and small gauge wire will be suitable.<\/p>\n

Because of the antenna’s slope the radiation pattern of the is not completely omnidirectional, but the null is not so deep that it will be useless in the null’s direction, down only by 6-10db.\u00c2\u00a0 It should not be difficult to find a good location that favors Europe without losing domestic RX. \u00c2\u00a0 If it works well for 20m this type of antenna will probably also be used for 15m\/10m when their time comes. \u00c2\u00a0[UPDATE: as of 11\/09\/12 the 20m skimmer is using the coaxial dipole, mounted as a sloping vertical favoring the southern direction(because thats the only place I could find to hang it)<\/em><\/strong>]<\/p>\n

20m will normally run on a Dell Optiplex 360(Pentium dual core e2200 running WinXP) on an ASUS Xonar DS soundcard at 96Kc.\u00c2\u00a0 The Xonar DS allows 192Kc scan rates, so during certain contests 20m will probably be opened up to 192Kc.\u00c2\u00a0 The normal bandwidth should be 13.99Mc thru 14.95Mc.\u00c2\u00a0 At the 192Kc scan rate the bandwidth will be 13.951Mc thru 14.143Mc.\u00c2\u00a0 That will be useful for the DX contests where activity spills over above 14.100Mc.<\/p>\n

The sequence of components will be:> \u00c2\u00a0Antenna limiter–>20m band pass filter(W3LPL)—>W7IUV pre-amp—->SoftRock. \u00c2\u00a0 Because of the harmonic problems on the 40m and 80m SoftRocks, these will also be retrofit with the W3LPL design filters.<\/p>\n

15m SoftRock Skimmer<\/h5>\n

Under Construction:<\/strong>……<\/strong>.The original SoftRock Lite II included components for a 15m version of the SoftRock utilizing the 3rd harmonic scheme in the 20m design. \u00c2\u00a0With a 28.060Mhz XTAL on hand, this should work FB when combined with a W3LPL rx bandpass filter to eliminate 40m and 20m sub-harmonics. \u00c2\u00a0Using the third harmonic from the divider, the softrock center frequency will be (28.060\/4*3)=21.045Mc. \u00c2\u00a0 This is a good match for a 48Khz scan rate soundcard, allowing much of the cw segment to be skimmed with a relatively pedestrian sound card. \u00c2\u00a0(Actual center fq=21.044400Mc)<\/p>\n

The W3LPL filter design values(links follow) were plugged into the AADE Filter Design program and tweaked to\u00c2\u00a0accommodate\u00c2\u00a0using capacitor values already available in the parts bin.\u00c2\u00a0 Tweaking was done using\u00c2\u00a0AADE filter design and analysis tool<\/a>. \u00c2\u00a0A very useful bit of freeware, so a great big thank-you-very-much to Neil at AADE.<\/p>\n

This filter was less difficult to tune than the 10m version constructed previously. \u00c2\u00a0Odds are I will re-visit that filter and check values used via the AADE package. \u00c2\u00a0Perhaps new component values can be chosen that will make tuning less critical without sacrificing performance too drastically.<\/p>\n

This plan is pending completion of the 10m experiment.<\/p>\n

Original W3LPL rx filter design.<\/a><\/p>\n

15m bandpass filter for 15m SoftRock CW skimmer<\/a><\/p>\n

15m bandpass filter calculated performance<\/a><\/p>\n

10m SoftRock Skimmer<\/h5>\n

** As of 02\/2013 dead, deceased, and otherwise inactive. \u00c2\u00a0 Requires debug\/repair…**<\/strong><\/p>\n

Decided to experiment with a 10m version based on the principles used in the 20m version. \u00c2\u00a0When building the 20m version, \u00c2\u00a0the levels on the 6th harmonic were tested. \u00c2\u00a0The 6th harmonics seemed to be as strong as the third harmonics. So it will be a fun experiment. \u00c2\u00a0The SoftRock band pass filter will be replaced with the 10m version of the W3LPL RX bandpass filters. \u00c2\u00a0These have been effective on 160m and 80m, and the 10m version filter for this project has been constructed and tuned. \u00c2\u00a0The W3LPL filters should do a good job of rejecting the lower band sub harmonics. \u00c2\u00a0The filter will be placed in front of a W7IUV pre-amp, which will feed the 10m SoftRock.<\/del><\/p>\n

That was plan “A”……..FAIL<\/strong>!<\/p>\n

The 6th harmonic(on the 20m SoftRock)\u00c2\u00a0turned\u00c2\u00a0out to be around 28.0875, which would work FB with one of the sound cards capable of 192khz scan rates. \u00c2\u00a0Unfortunately, the even harmonics don’t work…probably because the quadrature signals from the divider cancel out on even harmonics. \u00c2\u00a0 Should have thought of that before, but not a waste – the kit can be re-worked for either 10m or 15m, or kept as a working 20m spare.<\/p>\n

“Plan B” will require finding a different method, or maybe a dead-bug version of the SoftRock V7.0.<\/p>\n

Plan B:<\/strong> \u00c2\u00a0In TESTING, 10\/2012>>>>><\/strong>Ordered\/received an inexpensive programmable oscillator from auction vendor, programmed by request for 37.450Mc. \u00c2\u00a0The\u00c2\u00a0existent\u00c2\u00a020m softrock was hacked to remove the oscillator stage(removed Q2, C4, C5) on the board, inserting the output of the oscillator at 37.450Mc at the R4-C6 junction. \u00c2\u00a0Using the third harmonic from the divider(37.450\/4*3) gives \u00c2\u00a0a softrock center at 28.087xxxMc. \u00c2\u00a0This hack worked FB once the proper supply voltage was provided to the oscillator, which required adding a voltage divider to supply 3.3v. \u00c2\u00a0The W3LPL style bandpass filter is used on the front end. \u00c2\u00a0Sensitivity on this receiver is down from the lower band versions. \u00c2\u00a0Some more de-bugging on the band pass filter may help with sensitivity, possible the filter needs tuning.<\/p>\n

Given the high(28.087) center frequency, this skimmer will normally be run only when a system\/sound card capable of 192khz scan rates is available.<\/p>\n

Other Mix-n-Match<\/h5>\n

The computer\/soundcard\/band assignments will all likely change after the first few months of actual use during contest season.\u00c2\u00a0 I expect to run one computer and two bands 24\/7\/365, and fire up the other computers\/available bands over contest weekends and other [seemingly] random times.<\/p>\n","protected":false},"excerpt":{"rendered":"

As of 2015-04-02 this information is mostly obsolete and in need of revision,w4kaz 160m SoftRock Skimmer <\/p>\n

The 160m skimmer is an original SoftRock 40(donated by N4GU) that was retrofit with a crystal and band pass filter designed for 160m.\u00c2 Part values for 160m were substituted based on value specifications in the SoftRock Lite II schematics.\u00c2 The 7.3xxMc crystal resulted in the SoftRock center frequency at 1842950Mc.\u00c2 The antenna is the NE facing K9AY, fed into a W7IUV preamp and a cascaded magic-T splitter.<\/p>\n

The 160m skimmer is fed off one of the -6db ports of the splitter.\u00c2 I\/Q signal is (for now) fed to a ASUS Xonar DS sound card with a 96Kc scan rate mounted in a dual core e2200 dell optiplex 360 minitower.\u00c2 The operating system is Windows XP Pro SP3+,\u00c2 VE3NEA CW Skimmer, and W3OA’s Aggregator for reporting up to the Reverse Beacon Network.\u00c2 Normal operation at the 96Kc bandwidth will provide a useful bandwidth from 1800.0Mc through 1890.5Mc<\/p>\n

80m softrock skimmer <\/p>\n

The 80m skimmer is a Softrock lite II.\u00c2 The crystal used is 14.138Mhz, resulting in the softrock center\u00c2 frequency at 3.533950Mhz.\u00c2 The antenna is a NE facing K9AY with the feed split three ways following the W7IUV preamp in the shack.\u00c2 The splitter is two magic T splitters cascaded.\u00c2 The 80m Softrock is on one of the two -6db ports of the splitter. CW skimmer currently running on Dell Optiplex 745SFF, with 80m skimmer on the onboard Realtek sound card.\u00c2 Normal operation is at 48khz […]<\/p>\n

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