[K4RY] K4RY IGate Status

[Kris Kirby]

On Wed, 5 Sep 2012, John Klingelhoeffer wrote:
> Attached are the schematics and service data for the DR-110.  Would 
> you and the other student club members do some basic troubleshooting 
> on the radio before I look at it to make sure that voltage regulators 
> and such are okay before I take time to dig deeper?  Are the voltage 
> regulators working?  Are the illumination bulbs getting voltage?  Are 
> there any shorted electrolytic capacitors?  Many of the early Alinco's 
> had backlit, clear on black LCD's that required backlighting in order 
> to see anything.  If the bulbs have burned out, you may not notice 
> that the segments are indeed lit and operating.  I've had to repair 
> several Alinco's for this malady and it isn't a trivial effort.  

Ah yes! If you can get your hands on the polarizer, flip it over. The 
display will then read as dark on light. We discovered in eighth grade 
that the venerable TI-34 basic Algebra calculator had a single 
display-sized piece of polarizing plastic which could be flipped or 
rotated to change the "sense" of the display to either admit light or 
block it. It looks like a clear piece of plastic, the size of the LCD 
panel located across the front surface of it. 

Since these are "reverse video" LCDs, a flashlight or another portable 
source of light may be used to read the display. 

I've never had luck with LCDs and the fine rubber/copper parts used to 
connect them together. 

> Lightning could have been the culprit, but since you hear noise, most likely not.  Lightning more often than not
> results in a fully zapped radio that does absolutely nothing.  The antenna for this radio is a lot lower than anything
> in the surroundings, and is DC grounded, too.  
> In Alinco's line of VHF radios, this is one of the oldest, hence documentation is sparse.  There is a service manual
> for the DR-112 which is similar, but not identical to, the DR-110.  If there isn't something easy and obvious that you
> find (and that should probably be the case if it is very dead) then it most likely isn't economically repairable.  I'll
> wait on the earlier mentioned transfer until I hear what you folks have found from internal power supply voltage and
> bulb checks.   
> 
> I'd agree with Kris' comment that a crystal controlled commercial 
> mobile radio might be a better choice if a new radio is needed.  I 
> purchase and am familiar with Motorola Maxar 80 (not 50) and Moxy 
> radios, which can be had on Ebay for $20 or so and add $20 worth of 
> crystals from Bomar to put them on the right frequency. 
>  See: http://www.ebay.com/itm/Vintage-Motorola-MAXAR-Two-Way-Radio-Model-D33TRA3000AK-with-microphone-/140844035594?pt=2_Wa 
> y_Radios_FRS&hash=item20caf56e0a   That is what I am going to use on 
> the APRS digipeater up in Clay County, soon.  

The Mitrek is useful either as parts (DIP construction), PA (insert 
1.125W to transmit at 100% rated power in a given model, up to 110W), 
etc. OTOH, I have heard reports of LO leakage, which is not a favorable 
thing at a shared site. 

The MCX100 is a Motorola radio that was designed for European, Asian, 
and Canadian markets. I bought a bunch of them off of eBay in lots of 
four radios or so, but never put the pieces together to convert from 
EPROM to DIP-based PROM. The radio is from the first era of the 
synthesizer, it plays an incrementing number out the I/O pins and loads 
itself with the frequency information using that. PROMs are $10 apiece 
from Jameco, without any data on them. The MCX100 also has a few special 
varieties. One has a 12MHz wide dual front-end (two 6MHz windows, 
diode-selected by the Synthesizer/PROM/Radio programming), and most are 
about 4MHz wide. They also can be knocked apart easily like the Mastr 
series of GE radios. Need a 6W exciter? Take the 25W PA off the back of 
the radio and bypass the RF to the filter board. The filter board is 
separate of the PA modules.

The blasted power plug is unobtainium though. 

Mitrek, Mastr II, MFJ-8621: crystal
Everything else: programmable, with varying levels of "programmability" 
depending on decade, construction, and ordered options. 

I'd aim for something simple-stupid with decent filters and no buttons 
to push. The Mitrek fits that category, and a 40W Mitrek (lowest power 
model) will run almost continuous-duty at 20W. OTOH, that's a liability 
because you don't want the 20W transmitter to desense every other radio 
in the vicinity (but that's going to happen anyway). 20W may be 
overkill. My car APRS rig uses a 40W Mitrek at 25W, and which it 
transmits a burst, my Motorola Saber loses all receive sensitivity. Both 
antenna are the same type, and located about four feet apart. So 
interference is expected. Some how I lucked out and located a 60-second 
time-out timer (TOT) for a few bucks on eBay.

One detractor of the Mitrek is space. One may purchase a TT4 and install 
that directly into the radio chassis and put serial data on the control 
cable pins. It's been said the TinyTrak line of trackers has problems 
with RF; what better place to avoid RF that swimming in it inside of the 
radio. Using two channel elements, a radio on a single frequency will 
"hear itself" inside the radio assembly itself; so the TNC has to be 
programmed that full-duplex is certainly a possibility. The radio's T/R 
relay -- a pair of reed-type relays surrounded by an electromagnet coil 
-- typically goes from T/R or R/T in under 80 ms. Unfortunately, the 
radio wasn't designed to be used for standard squelch (tone squelch was 
the norm of the two-way world), hence the "noise gate" squelch sucks in 
comparison to the bi-level hysteresis squelch of the Micor. Software TNCs 
like the KPC3 tend not to notice, but some of the hardware TNCs look for 
a voltage offset to signal that there is a signal being received by the 
receiver.

*Some UHF Motorola Micor radios have a circulator build-into the T/R 
relay at the output connector of the radio. It's weird juju, but it 
works, and with a few scrap hard drive magnets, you can tune the 
circulator without opening it. Circulators are good for things like 
shared radio sites. Or radios that tend to leak RF/IF/LO out the input 
jack. 

Most of the designs, particularly GE or Motorola, don't like to run at 
less than about 60% of rated power. Efficiency will be low as well at 
the lower power levels on transmit.  Fortunately, you can turn a few 
types of server power supplies into 12 - 15V power supplies for "bulk 
current" use.

 http://www.rcgroups.com/forums/showthread.php?t=1292514

You can make up to 140A at 13.8V from a type of Dell server power 
supply, but it runs on 208V only -- not very handy unless you're in a 
datacenter using standard-type three-phase power. (Yes, it will work on 
240V, but the parts don't have much overhead for peak-to-peak voltage, 
so above 244V, it can go POP!)

Also, any resource for any commercial radio:

Yahoogroups
Radio Information Board (radio161)
Batlabs / Batboard
Repeater-builder.com and the repeater-builder Yahoogroup.
 
> There are also a LOT of commercial radios coming out of service right 
> now due to the FCC narrowbanding rule so even new ones, if they can be 
> programmed, should be better than the Alinco.  If they are 
> multichannel, they are sort of a waste compared to the single channel 
> crystal controlled radios.  But, if the price is right (free with all 
> cables, control heads and free programming) that sort of trumps the 
> others.  Otherwise, they can be a lot of trouble trying to get the 
> accessories and programming done, and generally are not worth the 
> trouble for a single channel radio.  

OTOH, now is the time to start building streaming audio rigs from single 
frequency scanners to put a web feed of the repeater on the website. I 
use this to monitor my repeater, and as long as VLC is listening to the 
stream, none of the rest of the computer cares. Careful bitrate 
manipulation can get it down to 8Kbps or so. And don't forget about 
Echolink, IRLP, APRS, or anything else that needs a dedicated radio to 
do receive-only or single-frequency link.

With the right version of the Radius firmware, the Motorola Radius or 
Maxtrac can be made to step through or jump to a given channel in 16 
channels by flipping four input pins on the 16-pin version of the radio. 
0x00h through 0x0Fh.

The caveats in multiple radios of a similar type at a given place is 
that they all have the same IF, and may create minute mixing products 
with each other. If you don't need to operate the radio, put it in a box 
and use feedthrough caps. Don't install the speaker jumper if the radio 
is going into dedicated service as a packet radio or as a repeater 
receiver. That "comforting white noise" will be annoying to someone....


But... do what you want. It's your club. =D

--
Kris Kirby, KE4AHR
Disinformation Analyst

PS: I briefly thought about dropping a Motorola Syntor or Syntor X9000 
onto I-20 during rush hour. Despite being as tall as pizza box and not 
quite as large, I realized that physics would eventually cause the 
device to be picked up, tossed, or propelled in the given direction of 
someone or something. A baseball isn't fun to dodge, but something 1.75" 
x 11" x 15" at 30 lbs. could kill someone at 35MPH.

I keep two of them stacked and handy at all times, in case I should need 
dirigible ballast or an emergency StairMaster.