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SoftRock Ensemble RXTX

November 11th, 2011

A few photographs of my latest tinkering—a SoftRock Ensemble RXTX.  This unit provides all of the hardware necessary to have a software-defined radio (SDR) transceiver that uses a computer soundcard for ADC and DAC.  It is available here as a kit.  They are kitted in batches of 20-100 every few weeks and usually sell out within 24-48 hours.

I originally had little interest in doing a full SDR transceiver (preferring receivers only) until it occurred to me that I could modify the RXTX as an IF strip for VHF/UHF transverters like many have done with the FlexRadio Systems rigs.  So, I have developed a modification that is minimally invasive to the operation of the RXTX.  At build time, you choose a nearly octave-wide “super band” for operation.  This one was built for the 20-30 MHz band, covering the 15-, 12-, and 10-meter Amateur bands, as well as the 25-28 MHz IFs that I (will) use with present and planned transverters for the 6-, 2-, 1.25-, and 0.70-meter bands.

I’m not sure I have the enthusiasm to build another SoftRock.  There are a lot of trifilar transformers to wind.  The final result looks pretty good and seems to work.  I’m going to put it on the spectrum analyzer soon to see how clean the output is and how I should balance the drive for the transverters.  Then, I will also include a write-up of how the modifications are done.  (I promise that writeup is the same place as the control circuit schematic for the 50-MHz transverter!)

Here, you can see the W1GHZ relay board for doing split-IF T/R switching.  If the transverter control cable (DB-9) is disconnected, the SoftRock switches to common-RF for regular 15-/12-/10-meter operation.

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(No?) Nonsense Radio

November 10th, 2011

The November 2011 issue of QST contains an Op-Ed that really left me shaking my head more than normal.  The author bemoans the complexity and feature sets of newer handheld radios and pines for the days of his IC-02AT.  He goes on at length about the “unnecessary” receive capabilities (NOAA weather broadcasts, AM/FM radio, etc) and how he has to search for the manual every time he wants to program a repeater offset.

Well, as someone who recently upgraded from a radio just slightly newer than the IC-02AT to a “modern” HT, he’s wrong on nearly every account (except the micro-/mini-USB port, which I would wholeheartedly support for charging purposes).

  • Eliminate extraneous features.  Too bad we all have different definitions of this.  I think scanning is a worthless feature, but like NOAA/NWS weather broadcasts.  In fact, my wife is delighted that we now have a battery-powered AM/FM+NOAA/NWS radio again that I will always be able to find and will guarantee that it works.  Did you hear that, guys?  My non-ham wife actually likes my HT and uses it to listen to FM radio!
  • Eliminate multilevel menu trees.   I’m just dying to replace my cell-phone-sized VX-3r with a knob-covered brick.  I’m sure you are too.  It’ll look great in my shirt pocket.
  • Eliminate the proprietary programming cables.  Maybe I’m not a typical ham, but I only have about ten memory channels programmed into my VHF/UHF FM radios and they took about 10 minutes to program through the front panel (my bad, menus).  The mini-/micro-USB port is a good idea for charging, though.
  • Allow for a battery pack that uses disposable batteries.  Last time I checked, most radios have this option.  Did I miss something?
  • Create an inter-vendor standard for user interface.  What if they standardize on Icom?!?!  The last Icom VHF/UHF FM radio I used received a “grade of S, for ‘stupid'” from its owner.  That was in 1993.  All of the Japanese manufacturers will be put out of business by the factory owned by the Chinese military that produces their products before this happens.

He should buy another IC-02AT if he liked them so much.  I bet for a Jackson or two, you could have a nice one…complete with the 6x AA battery holder.  Heck, buy two or three for spare parts.  I think I have the Service Manual around here somewhere if I didn’t already sell it.

On a more serious note, there are lots of no-frills radios available out there, even brand new ones with factory warranties.  Until recently, at least, the money in VHF FM radios was in two-way, government, and public safety, not amateur.  There are a lot of amateur rigs at the “low end” of the market that share a lot in common with their commercial counterparts.  And, of course, you can always buy used Motorola gear on eBay if you desire ultimate performance and ruggedness.

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CW Sweepstakes 2011

November 8th, 2011

So, K3KU, who won last year’s Maryland-DC certificate in A-power (150-watts, no DX cluster) for Sweepstakes CW posted to the contest club e-mail reflector a few weeks ago noting that although he had won that I had nipped at his heels with 7 additional hours of operating left on the table.  I responded to the reflector that he had operated long and made more contacts and therefore deserved the win…but, that I was highly motivated by that fact this year.

I tried not to let Sweepstakes consume my home life before the contest since contesting is a major disruption for a married couple, let alone a couple with a four-month baby.  So, I did not start setting up and testing the logging software, etc, until Saturday morning of the contest.  As long-time readers know, I replaced TR Log for DOS in the Spring with TR4W on Windows XP.  I also replaced the real-time keying interfaces (basically an NPN transistor and a resistor attached to a serial or parallel port) with a K1EL WKUSB.  This combination worked flawlessly for the most part, although there were a few glitches I need to fix.

Last year, 80 meters was excellent.  And, for a city lot station, I have a pretty good setup on 80 (full-size vertical and a K9AY RX antenna).  So, even when I had a slow start on 40 meters with the second radio on 20 meters, I had high hopes for a bottomless pit on 80…that never happened.  And, something—perhaps related to the lawn mower incident— is wrong with the K9AY.  So, I had a solid S9 buzz on 80.  When I worked K3AU (op K2YWE), he sent ‘A’ as his precedence and a serial number that was 20% higher than mine.  In fact, every time I heard him, that geometric relationship in our scores held.  I was worried but plowed forward.  The high bands were clearly in good shape because there was always a clear run frequency on 40 and 80.

I operated from the start at 2100 UT on Saturday pretty much straight through until 0700 (3 am local, actually 2 am after the Standard/Daylight time change) on Sunday morning.  Slept for about 4.5 hours (an even multiple of 90 minutes, I might point out) and was back at it again.  Having not spent much time on 20 the night before, I was keen to get there and was well-rewarded for doing so after scraping up what I could on 80 and 40.

I never really worry about multipliers in SS.  Like the “Soviet Russia” jokes go, “In Sweepstakes, multipliers work you.”  But, the fact that K3AU was kicking my butt and the fact that I had only 70 sections (out of the possible 80) on Sunday morning was a bit of a motivator to set score aside and make an effort to get “the Sweep” of all 80.  My normal (low-sunspot) strategy is to call CQ all day Sunday on 40 meters with the second radio S&Ping on 20 and vice versa.  With two more bands definitely in play, this was a different experience.  Since I finished the W3NQN filters, I now felt confident that I wasn’t going to destroy my receivers operating SO2R on 15 and 10.  However, I soon noticed that there was quite a bit of RF getting into the computer.  When I was CQing on 20, keyboard entry to the computer was choppy.  It’s very difficult to line-up a second-radio contact when you can’t enter the call!  Some ferrite will fix this.

So, I ended up using the second radio mostly as a multiplier monitor.  First, I found KE0A (North Dakota) on 10 meters with a roaring pileup.  I kept CQing on 40 and 20 with 10 in my right ear until the pileup died.  I dumped my call in and worked him on the first try while running off a dozen or so guys on the left radio.  SO2R WIN #1!  The same thing happened with the elusive VY1EI (who deserves a massive medal—Northwest Territories).  However, VY1EI’s pile-up management technique involved moving around in frequency.  So, I just waited for him to move and I had the good fortune of being able to study his habits for a half hour without losing rate on the other radio.  SO2R WIN #2!

With VY1EI in the log, I only needed Nebraska for the Sweep.  And, I was rewarded when W0PQ answered my CQ on 20 at 2242 UT.  So, with the Sweep out of the way, I pressed on trying my best to stay motivated and keep the rate up.

Although running (calling CQ) is mentally easier, I found search & pounce much more effective from a rate standpoint for a lot of the contest.  I probably should have done even more.  TR4W guessed that I made 441 QSOs by running and 294 by S&P.  It also says that I called CQ 3870 times.  That’s a pretty bad return on investment.  Anyhow, here are the numbers from 3830 for the interested:

                    ARRL Sweepstakes Contest, CW

Call: K8GU
Operator(s): K8GU
Station: K8GU

Class: Single Op LP
QTH: MDC
Operating Time (hrs): 21
Radios: SO2R

Summary:
 Band  QSOs
------------
  160:    0
   80:  182
   40:  330
   20:  170
   15:   31
   10:   22
------------
Total:  735  Sections = 80  Total Score = 116,000

Club: Potomac Valley Radio Club

 
Those numbers include 10 dupes (at least two of which duped me several times).  But, the score is calculated as 725 x 80 (x 2).  Last year, I lost 12 QSOs with two additional penalty QSOs.  I’m not optimistic about this year.  Last year’s #3 finisher in Maryland-DC is claiming 738 x 80 in 24 hours (and an effort to improve his accuracy).  And, K3KU is claiming 716 x 79 also in 24 hours.  So, I may have to settle for a spot down in the rankings again this year.  After the contest, K2YWE fessed up that his K3AU effort was actually a last-minute switch to Unlimited…so, at least I have a chance despite some mediocre performance on my part this year!  It all comes down to the log-checking.

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DXpedition QSLing

November 1st, 2011

This post might better be titled “supporting things that you value.”  A recent large-scale DXpedition to a “new one” just started sending out QSL cards in the past few weeks.  I have seen a bit of traffic leaking onto the regional contest club’s e-mail reflector about QSLing this operation and today someone complained that QSL requests that included donations were being processed rapidly and that he had not yet seen his. He was thoroughly chastised by a number of people on the reflector (including one of the DXpedition operators who went on at some length about the cost of the DXpedition) before the thread was (wisely) quashed by the moderator.

I composed a short reply very early in the melee, but decided (also wisely) not to contribute it because it really had little to do with contesting.  So, I’m writing here in hopes that someone finds it interesting.

When I was a new ham, I won a copy of the ARRL Operating Manual at a hamfest.  It sounds inane now, but I read the thing cover to cover.  In the chapter on DXpeditions, the author writes, “A donation should never be a condition for receiving a QSL card.”  That has stuck with me through the years.  The fundamental question is: why spend tens of thousands of dollars on the effort only to hold the operators who worked you hostage for a donation that might cover your QSLing costs if you’re lucky?

But, life is rarely black and white and most DXpeditions understand the futility of that question, so the situation outlined above rarely happens.  In the present scenario, the DXpedition stepped into the gray by prioritizing donors ahead of non-donors.  I have no problem with this.  In fact, as I began to write in my reply, it is a matter of supporting things that are important to you.  If having a card for the “new one” is important so you get on the Honor Roll for this year’s DXCC Yearbook, how much is that worth?

This falls into the same category as people who used to complain about the results of contests sponsored by CQ magazine being unavailable for free online.  Well, if you want the results, buy the magazine!

Enough ranting…did somebody mention that CW Sweepstakes is this weekend?  SWEEPSTAKES!

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Amateur Wiring

October 13th, 2011

I’ve picked up a couple of Mirage “brick” amplifiers over the past few years.   I’ve also rewired the DC cable on each and every one.  Here’s the latest.  AWG 10 to AWG 16 transition?  Seriously?  I know it technically doesn’t matter too much for a short run, but these amplifiers suck down a lot of current and I just don’t see cutting corners on that.  Maybe I’m a purist…

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A deaf VX-3R

October 12th, 2011

I do not spend a lot of time on VHF/UHF FM and have not for many years.  My first radio in 1993 was an Alinco DJ-580T handheld and I’ve thought at various times that a new handheld might suit me well, especially for receiving.  A few weeks ago, as I tend to, I came across a Yaesu VX-3R offered “for parts or repair” on attractive terms and so acquired it—my second handheld ever.  The problem seemed straightforward enough:  full TX power, but no RX on amateur bands.  RX on FM broadcast OK.  The seller assured me, after I had agreed to purchase based on his description, that “somebody” had told him that this problem occurs when “only one component is bad.”

Based on the seller’s description of the problem and a thorough reading of the Technical Supplement, I developed a short list of candidate failure modes, components, and sources.  Fortunately, all of the components could be sourced easily from the usual sources.

When the radio arrived, I gave it a functional check and it indeed exhibited the problem that the seller had advertised.  I quickly popped it open and noticed a small red sticker in the lower right-hand (when facing the device like you would operate it) corner of the Main Unit (Side A, per the Technical Supplement’s notation).  A neatly hand-drawn arrow pointed to component Q1025, which upon closer inspection, was clearly damaged.

So, I quickly set about identifying the component and procuring a replacement.  It was a NJU7007F3 operational amplifier.  Huh…it did not contribute to any of the failure modes I had initially suspected.  However, a careful reading of the Technical Supplement indicated that this op amp drives varactor diodes in a tracking preselector—so, if it does not work, the radio will exhibit varying degrees of deafness in the amateur bands.  I found out later that the “somebody” was actually a Yaesu technician who had seen the radio for repair at the behest of a previous owner and left the sticker for me.  At any rate, this component clearly would have to be replaced if I were to fix the radio, so I set about looking for a source.

Mouser listed it in their catalog but wanted me to buy a reel of 3000.  No thanks.  At least they had it listed.  So, I did the next most logical thing—I made a list of other parts that I needed and called Yaesu.  The part was back-ordered to Japan for 4-6 weeks, but only cost 0.42 USD.  I bought three.

After however many weeks it has been, a package from Yaesu showed up on my doorstep tonight.  After repairing a damaged PCB trace (non trivial on something this small), I was able to replace it.  The little black speck in the middle of this photograph is the removed component.  For my non-US readers, the US 0.01 USD coin (“Penny”) is about 19 mm in diameter.

The radio fired right up and received NOAA/NWS right away.  The entire repair once I had the parts was about 30 minutes.  There are still two unbuilt SoftRock kits, an IC-290A with an unlocking PLL, and W1GHZ transverters for 903 and 1296 to be worked on…maybe tomorrow…

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W3NQN filter wrap-up

October 9th, 2011

After about six years of sporadic effort, I finally finished the W3NQN filter set by building the 10- and 15-meter filters over the past two weekends.  Now I can operate SO2R with impunity on all bands.  Several band combinations are still problematic, but those are problems that filters can’t solve.

Because the geometry of our home does not permit me to have a walk-behind station desk, I had to attach the filters to the mounting board by laying on my back with a right-angle drill.  That sort of thing is always a bit exciting!

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Eliminating CRTs

October 9th, 2011

Ever since I replaced my primary station computer (a decision that may be reversed soon—details in a later post), I desired to replace the remaining 19-inch Dell Trinitron CRT monitor with something lighter and smaller.  Mom and Dad were in town a few weeks ago on a much-needed vacation and we went to the National Air and Space Museum’s Udvar-Hazy facility near Dulles Airport.  This is only a few miles from one of the best used computer shops in the DC area—CedarPC.

CedarPC is nice because they’ll sell you “damaged” stuff at a discount if you don’t care about the damage.  I inquired about a 24-inch flat panel I had seen on the web site, but they could not find it.  They did find me a nice 20-inch flat panel that was just missing the stand and the price was right.  The missing stand was no big deal because I wanted to mount the monitor on an arm so I could bring it closer to the HF end of the station desk, tuck it in at the VHF end, or even swivel it out over the couch to watch a DVD.  Sold.

Monitor arms are generally expensive…at least 2-3 times what I paid for the monitor itself, often more.  So, I went to trusty eBay and found something designed for mounting televisions for $15 including shipping.  This did require some modification of the monitor housing and liberal application of wide washers to reinforce the plastic in the housing.  But, it was done with all junkbox screws and washers.

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Fascinating signals: AA1TJ/QRPp

August 17th, 2011

Last night, as I have been doing lately in both the evenings and mornings, I was trawling the bands with a SoftRock (a dual-band v6.0 built for 40 and 80 meters—my first SoftRock) and Rocky.  Without fail, the waterfall enables me to see something interesting, which brings me to the point that I really need to integrate these receivers into my station.  But, I digress.  The really tantalizing, fascinating signals are the weak ones, especially when they are weak and unusual.

The subject weak and unusual signal is shown in the figure headlining this post.  Rocky’s cursor shows the approximate bandwidth of the CW filter (250 Hz, if I recall correctly) and the center frequency (7026.25 MHz).  I tuned it in and caught a CQ from “AA1T…”  Recalling that I head read about Mike, AA1TJ‘s, Das DereLicht transmitter built mostly from parts scavenged from a dead CFL, I suspected it was him.  After a moment the QSB came up and I caught the ‘J.’  Thanks to the fact that the SDR is not fully integrated into the station, I scrambled to plug my 15-year-old Small Wonder SW-40 in and get it online.  Mid-scramble, Sarah handed Evan off to me for a diaper change, but I did manage to snap the screenshot above.  By the time I returned to the shack awhile later to close things down, AA1TJ had disappeared.

Through the (ubiquitous) magic of the Internet, I sent Mike an apologetic e-mail QSL, which yielded a nice response.  It turns out that he was trying a 40-meter version of the first transistor transmitter described in the amateur literature.  The design for 146 MHz by K2AH appears in March 1953 QST.  If you are an ARRL member, pull up those old QSTs in the archives and read about it.  K2AH is on the cover of February 1953 QST with the same transmitter.  Mike figures he was making 20 mW, or 20650 miles/Watt on the path from his station to mine.  The more remarkable thing is that he was using a 1956-era point-contact transistor (the same type as in the K2AH article).  Fascinating stuff!  Hopefully, we’ll connect for a real over-the-air QSO sometime soon.

Thanks, Mike, for making my day by doing something interesting and sharing it on the air!

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Improving 50-MHz Transmit Capability

July 28th, 2011

Over the past week in the evenings, I’ve managed to cobble a little PA together for the 50-MHz transverter.  It’s a near-clone of the PA in the Elecraft XV50 using the Mitsubishi RA30H0608M.  Last night, I got it all hooked up and installed in the cabinet.  It broke into oscillation when keyed on CW.

The oscillation was about 50.040 MHz.  I reasoned that it might be the PA output coupling into the nearby TX RF bandpass filters which are followed by 12 dB of gain before returning to the PA.  So, tonight, I added a litle shield between the BPF and the PA board.  That seemed to clear things up and I got about 10 watts out.  There is a 6-dB pad between the last driver stage and the PA, so I should be able to get it up to about 18-20 watts.  But, the first goal will be to check the linearity on SSB.

In other transmit capability news, some boxes and heatsinks arrived for the W6PQL PAs for 903 and 1296 this afternoon.

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