Wednesday, December 30, 2020

Cabinet Re-Build for Studio A, part 2...

 Picking back up on the cabinet build for Studio A. It's been a fun project, and CHEAP. I had a unique space size to utilize, and this pair of old shelving units just happened to be thr correct width. For $5, I couldn't help but tackle this build. Below are a few photos of the shelves after being drilled, and the shelves fitted into the locations I needed them at... Enough for today, paint tomorrow!


Tuesday, December 29, 2020

Cabinet Re-Build for Studio A...

I had a little extra wall space in Studio A, and wanted to use it for some of my shortwave radios, QSL card files, etc. Debbie looked around on marketplace and found a local person with a couple of cheesy shelving units for $5. After getting the dimensions, I decided to get them and rebuild them to fit my needs. The shelf loading would be low, so I thought these would work out just fine. Here's a few pics and descriptions...

I began by assembling the bits from the pile of wood I bought. I used the cheesy cardboard backing just to hold it square during assembly. I used some 1" square stock as joiners to hold the two cabinet sections together.

You can see the 1" square stock pieces I used to join the sections. There was no top board for one of the shelving units, so I screwed the bottom board into the upper part, screwed the 1" joiners to the bottom of that shelf, then the sides of the lower section to the joiners. 

I picked up a sheet of 1/8" thick composite cabinet backing from Lowe's for about $12, cut and nailed it to the back. It's much stronger than cardboard, and holds the cabinet square very nicely. 

 View from the front. I put the textured side facing forward, since it would hold paint well and not scratch off easily. 


The bottom of the cabinet is seen in this photo. I plan to pre-drill holes in the shelving and side of the cabinet for AC power and antenna feedlines to enter. 

You can see the holes in the cabinet side in the pic above. Enough for today, I'll get back on this tomorrow and continue.

Sunday, December 20, 2020

32 Year Old Keyboard & Cleaning...

I know, I'm a tightwad... I also like old stuff :-) I have an old keyboard that I've used in the shack for years, on several computers. I keep using this old keyboard because I like it, it's small, and doesn't take up my space on the table. It's perfect for my application, and every other keyboard I have looks like a monster beside this thing. It's actually the removable keyboard from an old 1988 Compaq 286 portable computer. It uses some sort of goofy looking round connector that I found an adapter for many years ago, and the adapter uses a PS/2 style socket on the computer. 

The lighting in this photo wasn't good but it's the only thing I had of it before cleaning... If you click the photo you will get the idea of the stains and really looked bad under bright light. Over the years, this thing had become yellowed, dirtied from handling with dirty hands and fingers, etc. This is a non-smoking home, but it looked like it had been in one...yet it never had. I had tried Windex, a little bit of scrubbing bubbles, etc on it, but nothing seemed to work. I was afraid to get too serious on it with liquids. It just kept getting dirtier. My wife had one of those Mr. Clean magic erasers (you wet it, squeeze it out, and it does remarkable things!). I tested one corner of the keyboard and was amazed. 

I grabbed a small screwdriver and popped all of the buttons off of the board, used a little handi-vac to clean behind those, dampened a magic eraser, and got busy. I did it while listening to a shortwave radio show and it took about 2 hours, off and on. Here's the finished keyboard. It looks and works like new. I use it on 2 dual core machines via free software called "Mouse Without Borders". You can see more about that HERE


WB4IUY Portable 1996


I found this photo while going through a bunch of old pics... Back story: This is an old Atlas 210 radio and power supply, MFJ antenna tuner, paper  & watch for logging, a copy of my license, and a roll of wire. When travelling for work, I used to put all this in a gym bag and take it on the airplanes as carry-on luggage. I'd get the a hotel room the highest I could in the structure, and after dark, I'd deploy the antenna. I would tie a weight onto the end of my antenna wire, and slide the wire out the window and down the side of the building. I'd use other wire scattered around the room for counterpoise / rf ground, tune it up, and I was on the air. Very often I noticed a lot of interference on the TV systems...I don't know what that was :-)


Once, when boarding a commercial flight, i was pulled aside and asked to open and empty the bag. I opened the bag, explained it was portable radio gear, and said "I have a Federal License for this". When I showed them my license, they immediately and said " no problem, sir, carry on. :-) Those were the good ole' days, I doubt it that would work, today! 

I made a lot of great portable contacts on that setup, and I'm sure it helped keep me out of trouble while I was on the road for days at the timer. I miss that old Atlas. It wasn't really a great radio, but it sure was a load of fun! 


Thursday, December 17, 2020

Icom IC-211 PLL and Other Repairs...

 I've owned this Icom 211 for many years. I bought it from a friend back around 2008, and it's had a few issues over the last 13 years. To be fair, this is a mid-70's vintage rig, so some repairs are to be expected to a 45 year old radio :-)  

I leave this rig on 24/7, just so it's nice and stable when I get on 2m SSB. I came in the shack and realized it wouldn't transmit, and upon further inspection, I discovered it wouldn't receive, either. Oh well, off the table, and into the workshop it went. 

Once I got it on the bench, I realized the PLL wasn't locking up, so I began checking various voltages. I discovered the -9vdc supply was only about -7 volts, and by the time the -9vdc source made it to the PLL, it was only about -5.5vdc. I sub'd in a -9vdc source, and the rig fired up and ran. After a bit of poking around, I discovered a small choke that supplied 5vdc to the dc-to-dc converter that generates the -9vdc had failed and was only supplying about 3 volts to the converter. Once that was repaired, 5 vdc was supplied to the converter and it worked correctly. The 9vdc source was once again, as it should be. 

 The radio had been drifting more and more over the last year, and a quick thermal test with coolant and a heat gun revealed a small styrene capacitor in the PLL was failing, and once replace, it was solid and stable. Also, there was problems with the dial lights, and some noisy controls. 

On the bench, getting a good check-up.

I sampled the VCO to the freq counter via a .001 cap. Loading to the VCO wasn't too bad. 

This is where the 820pF styrene cap was located that caused all the drift...

This is the -9vdc dc-to-dc converter that caused the problem...

This is where I sampled the -9vdc that returned to the PLL...

While the radio was on the bench, I wanted to replace the meter lamps. I had some "warm white" LEDs to experiment with, from a string of LED Christmas lights. I discovered that 1000 ohms, 1/2 watt was about the right resistor value to bring the lamp to normal brilliance @ 20 mA or current, when powered from the 12vdc source. 

There's the Christmas lights I used. I'd break the clear part off, and the LED would slide right out. Easy to do, and you can buy a sting of these for $3-4 bucks. They're bright. You can see them in the meters of the radio, below. While the radio was on the workbench, it got a full alignment and is performing very well. 


Tuesday, April 21, 2020

A little work on the Heathkit SB-200 Amplifier

The Heathkit SB-200 is a very popular HF amp, and very dependable. This one belongs to a friend, and had begun to vent the filter caps from time to time. It was time for a little work, so here we go....


Case removed, ready to remove inner covers...

The amp was in very good condition, just had a bit of dust to get rid of :-)

With the upper inner cover removed, it exposes the tubes, filter caps, etc.

I removed and cleaned the dusty tubes. This will help the tubes run a little cooler...

It has the original Cetron 572 tubes installed from the build sometime around 1980. Here they are, clean and ready to be reinstalled...

I also used compressed air to clean the RF compartment, and the rest of the amp.

Note the filter caps. The originals were much larger and only 125uF vs. the newer, smaller caps in blue that provide 330uF. This will yield a better filtered DC supply, and take up less space than the originals.

Here, you can see the power supply board refitted with new capacitors and reinstalled. All bleeder resistors were in tolerance and good condition.

While in the amp, I included a few updates. If you notice the two diodes attached to the back of the plate current meter, this provide protection in the event of a tube short or arc. I also installed HV glitch protection, and bias protection.


All finished, tested, and ready for re-assembly.

Here she is, headed back to her owner. This amp is extremely well cared for, and should last many years to come!

Monday, March 2, 2020

Tri-Band Repeater Antenna Build, cont'd

This is a few more photos of the new repeater antenna build, and some observations.While tearing down a 4-bay antenna on 154mhz for parts & materials, I measured things with my MFJ Antenna Analyzer, and took note of some dimensions...

First, the larger dipoles are from the 154mhz antenna. I made a little pigtail connector for the MFJ, and took some readings. Resonance and impedance of these types of antennas is impacted by proximity to the mounting mast and the width (these are 3") of the loop. They also require at least a 1/4 wl of mast above and below for proper operation. The larger units were resonant at about 154mhz, where I expected. These dipoles are 17" per side, from the mount to the end of the loop, total 35" tip to tip (counting the 1" dia mount in the middle). The loop is 3" wide, edge to edge, and they are 3" from the mounting mast to the edge of the dipole loop. These are the dipoles I will modify for 2 meters.

The smaller dipoles are 15" per side, from the mount to the end of the loop, total 31" tip to tip (counting the 1" dia mount in the middle). They were resonant at about 168mhz. I altered the formula to calculate the proper dipole size, and it clearly doesn't track as I alter the dimensions, so I'll be doing a bit empirical testing (read trial and error, hahaha) to work the bugs out of the 220 and 440 antennas.

Another interesting observation...using DB Products RG-11 cable, the matching sections were pretty much the same length as the tip-to-tip dimension of the folded dipole elements. We'll see how this works out when I get these tuned and installed on a test mast...

I plan to use the single mast section on the right (with the rain bonnet) to install a pair of folded dipoles for 2m, 220, and 440. My plans are to keep this a compact antenna. I realize it'll be a compromise antenna, but I need to keep size down for a DC grounded tri-bander. 

RG-11 in the original installation...

154 mhz vs 168 mhz...

This pair will be modded for the 147.39 repeater.


Wednesday, February 26, 2020

ARR RX Preamp Failure, 442.400 repeater...

Shortly after getting the 442.400 repeater back on the air in test mode, I discovered the receive preamp was not working. This is an ARR P432VDG GaAsFet rx preamp. It has worked well for many years, having originally been installed back around 1994. This repeater took a lighting strike when it was installed at the Zebulon site, and I had never tested the preamp. I had to replace the PA at that time, so I'm guessing that's when the preamp failed. 

I put it on the IFR and spectrum scope, and discovered that it was a "deamplifier" :-) About 34db of loss when powered up, the GaAsFet has failed. This unit is about $100, so it's certainly work repairing. A new FET is ordered, so I'll post more about this during / after repairs. In the photo below, I set the sig gen for 0dB direct, and with the preamp inline, you see the 34dB or so of loss. 


Tuesday, February 25, 2020

Converting a UHF Motorola Micor to Repeater Service

I posted info on my old Motorola Micor UHF repeater on my blog, and people asked questions about how to do it. This is a fairly easy task, though it's far easier to stack two of these radios (one for receive, and one for transmit), but I enjoyed the task of repeating within a single radio. 

There's adequate isolation to do this, even when using a receive preamp, with a good set of cavities. These radios are cheap as dirt, often costing less than the crystal required for conversion to the ham bands. The nice thing, being crystal controlled, is you have no phase noise to deal with as with synthesized rigs. They are TOUGH AS NAILS! I've run them hot, it's been hit by lightning, and has operated an horrible physical conditions at one of the repeater sites. Users have locked it up for hours on end while cross-banding HF operations through it. The repeater in my previous blog has been in operation since 1994, so 26 years is nothing to sneeze at.  I'll snap some pics of the internals that I've modified, when I go back into it, to help illustrate the process. 

As I said, it's much easier to simply tune up a couple, one on the RX frequency and one on the TX frequency, wire a controller, and let'm fly. But, if you want to modify one for full duplex repeat, here's the info. I wrote the compilation of notes I accumulated and included my experiences in Microsoft Word. You can download the file, and if you don't have MS word, there's a host of online converters you can open it with for free. 

Go to my website at , mouse over the toolbar across the top of my webpage to [WORKSHOP], and click on "Schematics Manuals". You'll find Motorola Micor in the listings. Have fun!!