AmateurRadio.com

Through some reorganization at work in the past two months, I have suddenly gained ready access to a lab full of RF test equipment again.  Two years is a long time to go without. Apologies for the cell-phone photograph of the screen.

I took the W1GHZ 1152-MHz LO board over to have a look at it during lunch.  I’m seeing -11 dBm at 1152.007 MHz.  I am a bit dubious of the last digit of the frequency (even at 300 Hz RBW) but I’m sure there’s a frequency counter around somewhere.  Anyhow, I need to put a MMIC (or two) on the transverter board.  That should be a nice evening project along with the W6PQL preamp kit that showed up today.

After chatting with Terry, W8ZN, about whether to keep or sell the AM-6155s (which I did sell to finance a tower), he suggested that I apply the N1DPM “Active Bias” modification to my elderly “160-watt” Mirage 2-meter amplifier.  I contacted Fred, N1DPM, and he sent me a copy of his paper Linearization of Solid State “Brick” Amplifiers from the 21st Eastern VHF/UHF Conference (1995), along with some additional notes from his notebook.  It’s pretty eye-opening how non-linear the amp is without the modification!  I finally gathered the parts and hacked it together last night.  Hope to test it soon with a “dummy” transistor and then live on the amp. The braided wires go to the thermal compensation transistor which is thermally bonded to one of the RF power transistors.

It probably won’t be ready for the ARRL June VHF this weekend, though.  So, I’ll only be using the amp on CW.  That’s no matter since I haven’t hung the low-loss cable (LMR and Heliax), nor have I received a D1010 432-MHz amp that will be on its way to me soon.  Everything seems to take longer than it ought to!

A while back, I came upon about two dozen Times Microwave Systems TC-600-NM connectors that had been improperly installed and cut off.  Knowing that LMR-600 type cable is commonly available, I stashed them for later use.  These connectors cost between $8 and $15 each, so the ability to recycle could offer a substantial savings.  I endeavored to see just what it would take to do so.

The first step is to remove the heatshrink tubing (if installed).  These connectors employed a relatively easy-to-remove heatshrink, which I was able to get off with a sharp knife.  (That probably means that they would have filled with water if they had been used.)

Twist off the old crimp ring with two pair of Channel-Lock-type pliers.

Presto!  (Be sure to do this in a work area where it is easy to vacuum up the small strands of braid that will invariably fall everywhere.)

A butane torch gets the pin off in no time.

Unfortunately, I did not have enough hands to take a photograph and demonstrate the proper technique.  Place the tip of the flame on the widest (diameter) part of the pin and rotate the cut-off coax with the pin hanging down.  The solder will melt and the pin will drop.  Reinstallation can be performed in the exact opposite sequence with the pin sitting on top of the coax.

The secret to this whole operation is the replacement crimp rings.  I originally was going to make them but since I did not know the dimensions, I was searching around the Web.  And, I discovered that Times Microwave offers them individually (part #CR-600).  So, I contacted Joel at The RF Connection and he sold me a bunch of them (second from right below) at an attractive price.

The three rightmost components—connector body, crimp ring, and solder pin, form a complete connector.  You just need to add heatshrink, which is also available from the RF Connection and many other vendors.  The trick to getting a correct installation on the connectors is to be sure that the pin seats (clicks) into the body before crimping the ring.  The whole process of disassembly takes about as long as assembly (minus the stripping step)—just a few minutes.

I recently obtained about 250 ft (80 m) of LMR-600 pieces from various places for about what it costs to fill the gas tank in my Escort.  So, this should be a relatively attractive cable for use at K8GU.

Thanks to some quick thinking on Sarah’s part, I was able to attend the Hamvention (Saturday only—the day that the sewer backed-up and “ruptured”…spewing nasty water down through the fleamarket) for the first time in a few years.  This is a recap from my perspective.

1. Attendance was down.  The fleamarket was shrinking.
2. There were a lot of lookers but few buyers in the fleamarket.  Predict that the fleamarket will shrink further next year.
3. There were still good deals to be found in the fleamarket—I picked up some LMR-600, a WA2AAU 2304-MHz amp (unmodified 1900-MHz PCS amp), a Rohn 45G rotator plate, some 20-GHz rated SMA relays, and some miscellaneous parts.  And, I passed on a few good deals as well.
4. I saw a lot more young people than I remember from past years.  Or maybe I’m just getting older and the population of hams younger than me is growing on account of that.
5. Hamabouts (and their drivers) were not so obnoxious as prior years.
6. Hara Arena may be a dump (K1LT told me the story—don’t know if it’s true—that during the Rolling Stones first U.S. tour, they had been booked at Hara, but refused to play when they saw the facility); but, it’s perfect for the riff-raff who show up for the Hamvention.
7. In the end, the Hamvention (like ham radio itself) is about the people you know and meet.  I had fabulous eyeball QSOs  with guys from almost all phases of my ham career (except the early years from 1993-2000).  The VHF/UHF weak signal crowd is a pretty amazing bunch of hams.  I had a great time getting to know some of them in the fleamarket.

This is about building electronics, not making beer, at home; although, I am sure there are parallels.  Three things brought me to writing this:  1. an eHam forum thread I responded to a few weeks ago;  2. the June 2011 issue of IEEE Microwave magazine (has articles by K2UYH, N2UO, and KK7B, perhaps others? thanks to W3KL via the PVRC reflector for bringing it to my attention since I let my IEEE/MTT membership lapse); and 3. a few minutes spent last night resuming a partially-completed Softrock kit gifted to me by a friend who decided to buy a FLEX-3000 instead.

Every once in a while, a thread appears on an amateur radio forum that goes a little bit like this, “Hi, I’m a new ham and I don’t have a lot of money to spend so I want to build an HF SSB station from scratch” or something similar. Somehow, somewhere, somebody has given the impression that it is less expensive to build your own amateur radio equipment than to buy it.  That’s true in some circumstances, but certainly rarely for anything that is mature, mass-produced, and readily-available on the second-hand market.  After all, there is nothing novel about a 100-watt superheterodyne HF SSB transceiver these days. The principal uncounted cost is the “engineering cost” associated with getting your first few projects working and keeping them working.

One of the first construction projects I undertook as a new ham was to build a Ramsey Electronics HR-20 (NE602-based) 20-meter receiver—$20 at a hamfest.  It did actually work eventually—but this was a simple kit with maybe two dozen parts.  Next, I built a ONER transmitter kit from now defunct 624 Kits.  I think that was another $20.  I never made any QSOs with that combination because I was always afraid of blowing out the receiver with the transmitter.  The first thing that I built that I actually managed to make a QSO with was a Small Wonder Labs SW-40, which I still have.  That set me back $55 and it did not work immediately.  Suddenly, that’s over $100 by the time you include the money I spent on a soldering iron and solder.  That’s one-third to half-way to a “real” used HF transceiver and I had two bands at 1 watt on CW only.  Furthermore—these are all kits—they leverage economies of scale in purchasing parts from various vendors and they have instructions to help you along.  And, I’d like to think that I was a relatively representative example of a recently-minted ham who had more ambition than money or skills…

As I soldered down 1206-size (easy ones) SMT capacitors last night, I was thinking of times that I rushed through a homebrew or kit project just to get it on the air.  In those instances the process was often, as I have belabored above, about saving money, not about the act of creating something.  Last night was about creating, not saving, and that is the joy of homebrew.

See original post here.  Convinced that I had it working, I put the IC-290A aside and worked on some other projects.  But, when I came back to it a few weeks later, the display was still disappearing.  So, armed with the schematic and the block diagram, I began narrowing it down.

The display digits and tuning A/D converter are both driven off the same bus.  But, since the disappearance of the display did not bring loss of receive, that gave me some confidence that it was not affecting the synthesizer.  In order to simplify the analysis, I elected to assume that it was a single component (almost certainly a cold solder joint or an electrolytic capacitor) at fault.

Another clue was that the VFO dial ceased to operate once the display started acting up.  Taking the single-point-of-failure assumption into account, this strongly implicated the microprocessor on the LOGIC board as a starting point.  The only suspicious device that I could find on the schematic was C9, a 1000-uF, 6.3-volt electrolytic capacitor on the Vcc line of the microprocessor.  So, I replaced it with a similar value unit from my junk box.

And, the radio seems to be working…for now.   I did park it on WA1ZMS/B overnight and it is still running.

For while, I had three computers stuffed into two operating positions at K8GU and things were just getting out of hand as far as keeping the software updated, the clocks synchronized, and LoTW uploaded—as well as just plain having space on the operating table.  So, I moved the venerable sakhalin into backup, spent $18 on USB-to-RS232 adapters and a few hours over the past two weekends reorganizing the operating table.

The new arrangement replaces a monitor with two small shelves (which are designed, I might add, to hold exactly two T2X control boxes).  I moved the DC power distribution system to be more centrally located and made room for some accessories that I’ve been meaning to move into arm’s reach.

Software is a different story.  I have been test-driving N1MM in VHF contests which are slower-paced than their HF counterparts.  As a die-hard TR-Log user, it’s difficult to make the switch.  I decided I had to go cold turkey.  I am presently trying TR4W, which is a very good clone.  However, it does have idiosyncrasies—the biggest of which is the behavior of two-radio mode.  When CQing on Radio #1 in TR-Log, ALT-D lets you dupe a station on Radio #2 then hit the SPACE bar to call that station on Radio #2.  With TR4W, ALT-D changes the focus to the Radio #2, but does not dump your call in, a step which requires you to hit ENTER.  The other small thing is that the delightful emacs key-bindings CTRL-W and CTRL-K do not wipe the present and both (call and exchange) entry fields in TR4W.  But, I’m getting the hang of using ESC.

Another thing that will take some getting used to is the fact that if the TR4W window loses focus, I can’t use the CW memories!  Fortunately, the paddles are close at hand!  For serious operating without sidetone, this won’t work, though.  Speaking of paddles, I’ve found that putting the paddles on the keyboard tray and the mouse up on the operating table is actually good as far as keeping mouse usage low.  Plus, the paddles remain at a comfortable height for sending.  Great arrangement!

Lots of other little projects around the station remain…