I've been in Amateur Radio since 1974, and still find new and interesting things to do. I like to build, restore, and operate on the air. This blog has been running for many years, so be sure to check out "Jump to Posts on Specific Topics" in the RH column to drill down and find lots of stuff. Visit www.WB4IUY.net for the lowdown at WB4IUY. Email me at wb4iuy@gmail.com if you have any questions.
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.
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 http://www.WB4IUY.net , 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!!
After a long period of inactivity, I'm in the process of getting all of my repeaters cleaned up, checked out, minor repairs made, and readied for going back on the air. Here's a couple of photos of the 442.400 repeater, online in my work shop. I originally built this back in 1993. I've made a few adjustments, and so far, all is running good. The PA is running at low power (15 watts), and it is carrier access. I do have it set up for a sub-audible tone of 88.5, but that is disabled at the moment. It's running on a test antenna out behind the shop, only about 20 feet off the ground.
This will be going back on in the stack of repeaters: 29.620, 53.07, 147.39, 224.80, & 442.400. I'll post more of the permanent installation, once the antenna work is completed.
This repeater uses a 6 cavity Sinclair duplexer on top (light brown enclosure on top of the radio), a homebrew bandpass cavity (gray in color) stacked on top of the duplexer.
The Sinclair duplexer was originally used in the commercial
service a few mhz above the 70 cm amateur band. They were repaired and retuned for the input frequency of
447.400 and the output frequency of 442.400. The bandpass cavity was
built from a scrap 800mhz analog cell site cavity. The repeater was built from a Motorola Micor mobile radio used
by the NC Forestry Service on about 452/457 mhz.
The controller is mostly homebrew, using a Communications Specialists
CW ID'r to handle identification chores. All timing (time-out, COS, tx hang timer, ID front porch timer, etc.) is
analog and built from 555 timers and discrete components. Audio processing is also homebrew using LM324 op-amps.
All audio mixing and controller circuitry is self-contained within the Motorola Case, making for a compact UHF
repeater. A pl of 88.5 is re-encoded on it's output signal during COS activity using Selectone encoders. This
is for linking purposes.
This is probably one of the most popular HF Power & SWR Meters Heathkit ever made. You'll pretty much always find these at every hamfest. Today, they sell for as much as $75, and I've bought some for as little as $10. They're very easy to repair and calibrate, and work nicely on the ham bands from 160 through 10m. I've found them to be fairly accurate (certainly usable) on 6m. Good up to 2000 watts, and can measure SWR with less than 10 watts excitation. I currently have several of these. This is one I bought back around 1991, and use it with my Heathkit HW-101 transceiver.
This is a Hy-Gain Super Penetrator CLR2 antenna I picked up many many years ago for the 10 meter repeater. For years, I used fiberglass antennas alike the Big Stick or the Antron 99 for the repeater. After several lightning strikes on the 10 meter repeater sites, as well as strikes on the 2m and 440 repeater sites using fiberglass antennas like the Diamond and Anli antennas, I'm DONE with fiberglass antennas. It's a proven fact that fiberglass antennas develop a strong opposing charge on the shell as wind blows across them during a storm, making them a target for lightning. They're not so bad for side-mounted or low altitude installations. Stay far, far away from a fiberglass antenna for high altitude repeater installations, use only DC grounded metal antennas.
The first step in this rebuild is to remove years and years of oxidation from the aluminum. I like to use Scotch-Brite pads for this. They easily remove the oxidation and really bring an aluminum antenna back to a nice shine. Disassemble the antenna and be sure to clean into all of the joints. Here's a quick pic of before and after on the 10 meter receiver's receive antennas, after just a few seconds of cleaning with a red Scotch-Brite pad. I'm pointing at a spot I just cleaned...
Here's a few pics and info on a Yaesu FT-101EE I overhauled for a friend. These are GREAT rigs, I've owned and rebuilt several over the years. Beautiful RX audio, stable VFO, great TX audio. Lots of tricks and mods for them, not to mention the cool looks of this venerable rig.
I like to start off with a working radio, if even working poorly. If it's not working, repair it to a point where it is before getting too deep in the restoration. Typically I start by cleaning all of the card connections, rotary controls & switches, and air variable cap rotor wipers with Deoxit D5. Spray and clean all wafers of the band switch assembly. Next, I replace all of the electrolytic caps throughout the rig with new units, I think around 65 pieces. After rebuilding each board, I reinstall it in the radio and power up for a quick test. Replace all power resistors in the PA cathode and grid circuits. Install the driver coupling cap mod. Test and replace driver / PA tubes as needed. Using a service manual, install all documented mods and updates. Perform a full alignment on the RX & TX. Replace all indicator lamps. When finished, these radios will give a modern day rig a good run for the money, and provide many years of dependable service. Here's a few pics of the process...
On the bench, ready for surgery...
Some of the terminal boards have caps that have to be replaced, and aren't easy to get to...
PA compartment open, new filter caps installed (much smaller than the OEM HV caps!)...
Boards laid out, repopulated with all the new caps...
Some of the caps removed and replaced. Notice how tall the HV caps were. The new HV caps are about 1/4 the size, but have higher capacitance and voltage ratings!
Cleaning the rotary switch wafers...
The gray colored cap in the upper edge of the photo needs replacing...
Replacing more caps...
Bags of caps, awaiting installation...
Notice the burned resistors in the PA screen grid circuit...
Replacing more caps...
Notice the difference in the size of the old caps vs. the new caps...
Replacing the driver coupling cap under the trimmer board...
The old HV caps, awaiting replacement...
Getting alignment...
All completed and on the air!
A quick video after the overhaul...
I always say this...I LOVE these rigs :-) I was working in a 2-way shop in the 70's when these were popular. Being a young kid, I never had the money to actually own one, but I got to operate many on the air and loved them.
Back in 1996, I walked to the mailbox one morning, and found a copy of a Japanese magazine - 29MHZ FM Radiosport. I was a little confused, as it was mostly in Japanese. I thumbed through the magazine, and realized they had a feature, multi-page article on my 10 meter repeater! Wow, was I ever surprised. I contacted the author, then JH7LGJ, and thanked him.
Thinking back, Japanese stations were heard regularly on the repeater at night. The repeater has been on the air since 1994, and with sunspot cycle 22 being so strong, it seems it was heard in Japan quite often. The repeater transmitter was running about 350 watts carrier, and would often transmit from before sunrise, until well after 11pm local. Here's a few pics of the magazine...
I have since rebuilt the repeater, and made many changes. Here's a coupe of links to the original installations and info about their builds...
I'm in the process of making arrangements to relocate my 147.39+ repeater, 224.80- repeater, and 442.400+ repeater to a top perch on my tower at home. After 30+ years experience with amateur radio repeaters, I decided I do not want a fiberglass antenna on my tower...only a metal DC grounded antenna. I decided to set about to design a triband antenna for tower top installation for these 3 repeaters, with the vertical mast robust enough to support the DC grounded antenna for my 10 meter repeater RX side.
I've started with a batch of DB Products folded dipoles. These are easily modified for correct operation on 2m, 220, and 440. These will all be fed from a single run of hard line via a 3 band tri-plexer. I've successfully fed the 10m receive antenna, 2 meter repeater, and 440 repeater like this in the past. Here's a few pics of the parts I'm working with. I'll update with more blogs as the project progresses. You can keep up with it by looking in the RH column in the "Jump to Blogs of Specific Topics", and clicking on "Repeater-Antennas".
The long antenna is a Hy-Gain CLR2 I am repairing / retuning to 29.520 mhz for the 10 meter repeater's receiver.
The Hy-Gain CLR2 is a DC grounded 5/8 wl CB antenna, and makes a great 10m antenna.
Here's a batch of the folded dipoles from DB Products that I am re-purposing for this custom build. They typically run around 110 ohms, so I'll be building a phasing & impedance matching harness for these, once tuned.
Load of parts, ready for cleaning and mods. I actually picked these up years ago and stored them away.
I've been playing with a new (to me) toy in the shack, recently. It's the Yaesu FL-2100Z HF amplifier. It's fairly rare, not nearly as easy to find as the FL-2100B. This version was more common in other countries, and has all of the WARC bands on the band switch and tuned inputs for them as well. It uses a pair of Cetron 572B tubes at about 2600VDC. Cetrons are the only 572B tubes that can be operated in a horizontal position, none of the other brands have supports on the grids to keep them from sagging into the plates when operated in this position. This is a sweet little amp, and runs around 500-600 watts output, depending on the band. This one was actually bought to serve as a "guinea pig" for a conversion project to the Russian GI7B tubes, but that's a story for another blog. Here's another pic of it, in operation with my old Yaesu FT-901. I love the looks of this lash-up!
This is the best handling straight key I have in the shack. It's a Signal Electric M100, and was made somewhere around 1939-1941, as best as I can tell from markings and catalog info. This one is equipped with a leaf spring, instead of the typical coil spring, and I've not been able to find any of the Signal Electric "J-38" style keys like that...so I'm a bit baffled by that part. If it was converted by someone, they did a great job: the lever spring force feels perfect and is very easy on the wrist.
I've not tried to clean it, other than to brush the dust off of it. It looks to be all solid brass (not brass plated steel, as it's non-magnetic), with a plated steel lever and flat top knob.
Signal Electric M-100 with leaf spring...
Close up shot of the leaf spring setup...
This leaf spring arrangement is a mystery to me, but it works great!
You can faintly see the "SIGNAL ELECTRIC MFG CO. MENOMINEE, MICH" markings in base, under the "up" adjusting screw contact point.
