GMRS: The Other UHF Band

I’ve always had a liking for the General Mobile Radio Service (GMRS). It’s a licensed radio service but does not require a technical exam so it works great for basic personal communications. When our kids were young we made good use of GMRS communications. This was back in the Pre-Cellphone Era, shortly after the dinosaurs left the earth. I still have my GMRS license: KAF1068



mxt100-with-mic
Midland MicroMobile GMRS Transceiver

GMRS uses frequencies in the general vicinity of 462 and 467 MHz. When the FCC created the Family Radio Service, they intermingled the FRS and GMRS channels, creating a real mess. See this page for a good explanation of how FRS and GMRS frequencies are arranged. Many of the low cost walkie-talkie radios sold in stores are combination FRS/GMRS radios.


I recently came across this really sweet little GMRS rig, the Midland MXT-100 Micro Mobile GMRS Radio. This thing is nice and small with an external mag-mount antenna for the roof of the car. It only has 5W of output power, which is not much more than a typical FRS/GMRS handheld radio but the external antenna should help a lot. (I’ve heard there are newer models on the way so stay tuned for that.)

I’ve encountered 4WD / Jeep clubs that use FRS radios for on the trail communications. This Midland radio would be a good upgrade for that kind of use, providing additional radio range. Some of these 4WD enthusiasts have gotten their ham ticket via our Technician license class. Ham radio provides a lot more capability but not everyone in their club is likely to get their ham license. GMRS is a great alternative…the other UHF band. It will work for other outdoor, community and club activities that involve “non radio” people.

FCC recently reduced the cost of the GMRS license to $65 for 5 years. I suspect that most people don’t bother with getting a license…but they should. For more detail on GMRS, see the FCC GMRS Page or for some good bedtime reading see the FCC Part 95 Rules.

73, Bob KØNR


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Repairing the power switch on the Kenwood KA-8011 (a.k.a. KA-801) amplifier

Back around 1990 my brother mentioned to me that there was an amplifier, in a box, in pieces, in the back room of the home TV/electronics store where he worked at the time and that if I made an offer I could probably get it for cheap.  Dropping by one day I saw that it was a Kenwood KA-8011 Integrated DC amplifier (apparently the same as the KA-801, except with a dark, gray front panel) laying in a box from which the covers were removed with a bunch of screws and knobs laying in the bottom.  I also noticed with some surprise that it had a world-wide voltage selector switch on the back and that the power cord had a Japanese 2-prong wall plug and U.S. adapter – and still does!  All of the parts seemed to be there so I offered some cash ($50, I seem to recall) and walked out with it and a receipt.


Figure 1:
 Spoiler alert:  This is the KA-8011 with the repaired power switch.
As noted in the text, the original, blue-painted panel meter lights were
replaced long ago with blue LEDs.

When I got home with the amplifier I knew that I had my work cut out for me – particularly since, in those days before the widespread internet – I had no schematic for it and no-one that I contacted seemed to be able to find one.  Powering it up I noted that the speaker protection relay would never engage indicating that there was a fault somewhere in the amplifier.


A visual inspection of the awkward-to-reach back panel’s circuit board revealed several burned-looking leads sticking up from the circuit board where transistors had exploded and several burned resistors.  After a few hours of reverse-engineering a portion of the circuit I realized that the majority of the circuit at fault was one of four identical phono preamp input circuits (there are two separate stereo phono inputs) and associated low-level power supplies.  Between the intact amplifier sections and being able to divine the color bands on the smoked resistors – along with some educated guesses – I was able to determine the various components’ values and effect a repair.

Figure 2:
The power switch, with a broken bat.
Click on the image for a larger version.

The amplifier now worked… sort of.  I then had to sort out a problem with the rear-panel input selector switch, operated by a flat, thin ribbon of stainless steel in a plastic jacket that was engaged from a front-panel selector.  I managed to cut off the portion at the front that had been damaged where it was pulled-on from the front panel having been loose in the box, punch some new holes in the ribbon, align the two (front and rear) portions of the switch mechanism and restore its operation.

Snap!

Having done the above, the amplifier was again operational and I have used it almost every day in the 25 or so years since, needing only to replace the blue-colored incandescent meter lights with LEDs, powered from a simple DC filtered supply.  In the intervening years I also had to replace some of the smaller electrolytics on the main board that had gone bad, causing the speaker protection circuit to randomly trip on bassy audio content and with slight AC mains voltage fluctuations.

Figure 3:
Comparing the old (top) and new (bottom) switch components.  In order
to prevent it from interfering with the body of the switch some of the
metal on the new bat would have to be removed.
Click on the image for a larger version.

I was annoyed when one day, a few months ago, the power switch handle – which had been bent before I got the amplifier – and then “un-bent” during the repair – broke off in my hand when I turned it on.

Using the “bloody stump” of the power switch for a few months  I finally did a search on EvilBay to look for a new switch.  While I didn’t find a power switch I did see a “tone control” switch for the same series of amplifier – so I got that, instead.  When it arrived I noted, as expected, that most of it did not mechanically resemble the power switch or look as though it would easily mount in the same location, but it did have essentially the same metal bat on the end as the original that I figured I could fit onto missing portion that had broken off the power switch.

Comment:

Even though the “new” switch was much too small and of insufficient current rating to have been used to switch the mains (AC input) power, it would have sufficed to operate a relay.  To have done this would have required that new holes be drilled in the front sub-panel to match those of this new, smaller switch. While this would not be “original” circuitry, it would have looked the same from the front panel and is a possible option should the power switch itself become unreliable some time in the future.

Removing the original power switch I laid the two side by side and made notes of the differences between and the metal bat of the original, which was narrower in some places to clear parts of the switch body, and taking a file to the new one I took off some metal to clear the possible obstructions.  I then noted on a crude drawing the length and orientation of the new bat based on the axis of the switch’s pivot point.  Because the bat of the original switch was embedded in a block of molded Bakelite I knew that I would have to somehow attach a portion of the new switches’ bat to the old, so I carefully disassembled with old power switch, cutting off and saving the original rivet on which the switch pivoted, and carefully noting where everything had gone, saving the small springs, contacts and some small Bakelite pins.

Figure 4:
The new bat, butt-soldered on the old switch.  Note that the bat from the
“new” switch has been filed to better-resemble the shape of the
original bat to clear the switch body.
Had I not been able to find a “similar” switch on EvilBay I could have
probably measured the original switch, found some scrap
steel of similar thickness and made a suitable replacement entirely
by hand with careful filing using another switch as a template.
Click on the image for a larger version.

Clamping the old part in a vise I cut off most of the original bat, leaving about 5mm of metal remaining.   Carefully comparing the old and new piece I then marked where, on the new bat, that I would have to cut to allow the repaired piece – consisting of the new and old butted and laid end-to-end – have the same length as the intact original.  Doing so – purposely cutting the “new” bat slightly long – I did some fine tuning with a file until the two pieces laid down precisely lined up as they should.

Attaching the new piece

Using some silver solder intended for stainless steel I applied some of its liquid flux – apparently a mixture of chloric and hydrochloric acid – and using a very hot soldering iron, “butt-soldered” the two pieces together in careful alignment and then filed the surfaces flat to remove excess.  While the bakelite switch body can handle a brief application of a soldering iron, I knew that it would not tolerate the heat from a proper, brazed joint.

This (weak!) solder joint was intended to be temporary, need only to be good enough to allow a sleeve to be made by wrapping an appropriately cut piece of thin, tin-plated steel (from my junkbox) around the joint.  Once this sleeve was checked for proper fit and folded tightly, additional flux was applied and the entire joint – sleeve and all – was soldered, the result being a very strong repair with the restored bat being of the same length and at the same angle as the original.

Reassembly:

The trick was now to get every thing back together.

Figure 5:
The steel sleeve being installed over the butt solder joint,
before soldering.
Click on the image for a larger version.

Reinstalling the pivot and making a few clearance adjustments to the original switch’s frame with a small needle file, the original rivet was then soldered into place and the entire assembly washed in an ultrasonic cleaner to remove the remnants of the corrosive flux from the bat and switch body.

In the base of the switch, the contacts, which were the same as those had it been an SPDT switch, were reinstalled – this time, rotated 180 degrees so that the previously unused contact portions would now be subject to electrical wear.  These contact were then “stuck” into place with a dab of dielectric grease so that they would not fall out when the switch body was inverted.

Figure 6:
The repaired switch, reassembled,  with the new bat spliced on.
Click on the image for a larger version.

After reinstalling the springs and pins, the rear part of the switch with the contacts was placed over the top of the moveable portion, held in the mechanical center, and the base was carefully pushed into place, compressing the internal springs and pins.  Holding everything together with one hand the proper operation of the switch was mechanically and electrically verified before bending the tabs to hold everything into place.

In reality the reassembly didn’t go quite as smoothly as the above.  During one of the multiple attempts to get everything back together the smaller-diameter rear portion of the small, spring-loaded Bakelite pins used to push on the contacts snapped off.  To repair these pins the front, larger-diameter portions – that which pushed against the metal contacts – were placed in the collet of a rotary tool and a shallow hole was drilled into the rear portion where the broken pieces had attached to fit short pieces of 18 AWG wire:  By rotating the piece into which the hole was to be drilled, the exact center is automatically located.  The pieces of wire were then secured using a small amount of epoxy – a process accelerated by placing the pins in a 180F (80C) oven for an hour.  After the epoxy had set the wires were then trimmed to the length of the original sections that had broken off and the ends smoothed over with a small needle file to prevent their snagging on the spring.  The result was a repair that was stronger than the original pins and these easily survived the reassembly.

The results:

Figure 7:
After reassembly it was noted that the gray “skirt”
was hitting the front sub-panel frame, preventing it from
being set to the “off” position.  A bit of heat was applied to
set a permanent bend so that it would clear this panel.
Click on the image for a larger version.

The amplifier was then put back together, very carefully.  The only real issue that I noted was that the gray plastic skirt/escutcheon on the bat ended up about half a millimeter farther away from the switch body and closer to the sub panel than before, causing it to snag on the front sub-panel’s cut-out when I attempted to move it to the “off” position.  Careful softening of the plastic with the rising heat of a soldering iron and bending it very slightly allowed it to clear.

Putting all of the knobs back on, tightening the bushing nuts and screws as necessary before doing so, I then tested the amplifier on the bench and was pleased to find that I’d not managed to break anything.

Finding that everything was working fine I put it back on the shelf where it belongs where I continue to use it often.


[End]

Connect Systems: Product Line Overview

Jerry of Connect Systems posted the following to the CS7000 Yahoo Group:

“CS580: This radio was designed to be in direct competition to the MD380 radio but have the advantage of being much easier to use because of a few new features we added. We sold over 100 radios before it was officially released and we have about 200 radios left before we have to order more. It takes at least 30 days from placing an order to receiving more radios. We have already received follow on orders from some of the people who have ordered the first batch of radios. It cost $130 each.

CS750: We reduced the price from $239 to $180. At this price, it is a competitor to the Tytera products but you get a better radio with more features. After the CS760 is stabilized, we will be adding more features to this radio as well as fixing any remaining problems.

CS760: This is the follow on to the CS750 series of radios. Besides having the features of the CS750, it has optional Bluetooth, GPS, Man Down, and vibrator. Its IP67 rated (waterproof) and has a color display. It will have the ability to be compliant with ETSI Standard Tier III. Being a new radio with new features now and more new features in the future, you can expect this radio to have frequent firmware updates both to fix bugs and to add new features. It was originally scheduled to ship December 1, then December 10, and now December 19. The basic radio cost $299 and with all the options it cost $399.

CS800: This is our single band UHF mobile (Available in VHF). After the CS760 is stabilized, we will be adding more features to this radio as well as fixing any remaining problems.

CS800D: This is a dual band CS800. I expect the VHF band to be the same as the CS801 and the UHF band to be extended to 512 MHz. It is initially going to be released as an amateur product but later we will get it part 90 certified. We do not have our cost yet but I am hoping the selling price will be $100 more than the single band CS800. We have preliminary schematics and we have a target of getting a working sample shipped by January 23, 2017 to show at the various amateur shows and production starting about two months later.

CS108G+: This is a Xiegu X108G with custom firmware to include a spectrum analyzer and an ID Timer. It covers all the HAM bands from 160 meters to 10 meters. We expect to get our first shipment next week.

CS7000/CS8000: This is a single band multi-protocol (DMR, DSTAR, Analog, and others) radio. We are still working on it but I will not give a definite date for initial shipments.

E-Commerce Web Site: Connect systems now has an online store where you can order most of our Amateur Products 24 hours a day. Please look carefully at the product description to see if in stock. The site is at csi-radios.com. It can also be reached from our main site of connectsystems.com”

BuyTwoWayRadios: Wouxun KG-D901 DMR Bundle

If you’ve got more money to spend on a new radio, you might consider the Wouxun KG-D901 DMR Holiday Bundle from BuyTwoWayRadios.com for $199.99:

“What’s in the Kit:

This Spewed Out of the Internet #33

0511-0701-3118-0930Here’s some more good stuff flowing forth from the interwebz.

HamRadioNow has a video of Laura Smith’s (FCC) talk at Pacificon. There’s lots of good info here on FCC enforcement activity. Gary KN4AQ produces some of the most valuable amateur radio video content on the web. How else are you going to see someone from the FCC speak about ham radio?

Sterling/NØSSC and Marty/KC1CWF have started the Phasing Line ham radio podcast, talking ham radio with a younger person’s perspective. They are on episode two…give them a listen. Look for them on the usual podcast feeds, or go here: n0ssc.com

I was interviewed by Eric/4Z1UG on QSO Today. Yeah, probably boring as heck but you’re reading this blog so your standards must not be very high.

The ARRL is cranking up an initiative to encourage collegiate ham radio clubs. Good idea.

DX Engineering visited the new venue (Greene County Fairgrounds) for the Dayton Hamvention. See DX Engineering visits the NEW 2017 Hamvention® venue and the drone video by Greg/W8WW that provides an aerial tour of the fairgrounds. I am looking forward to attending Hamvention next spring, the first time in many years.

Use Phonetics: HamRadioSchool.com republished their classic article on the use of phonetic alphabets. Also, take a look at my Shack Talk article on the same subject.

While reviewing the Technician license exam questions, I noticed that SWR is referred to as “2 to 1” or “1 to 1”. I see this as old school terminology…a ratio can be expressed as a single number: “my SWR is 2.” This triggered some discussion and a KB6NU blog posting.

That’s it for now. Happy interwebzing.

73, Bob K0NR

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BuyTwoWayRadios.com: MD-2017 Dual Band DMR Digital HT

BuyTwoWayRadios.com – New dual band DMR digital radio coming from TYT:

“Details are still sketchy, but TYT has released a few specs on this new handheld. Key features of the TYT MD-2017:

  • Dual band 
  • Dual display 
  • Dual standby 
  • Complies with ETSI TS 102 360-1, -2, -3 
  • Uses Time Division Multiple Access (TDMA) 
  • Compatible with MotoTRBO Tier 1 and II 
  • GPS capable 
  • Lone worker function 
  • Encryption function 
  • Analog and Digital Modes 
  • SIngle Call, Group Call and All Call 
  • Remote Kill/Stun/Activate 
  • IP67 Waterproof. 
  • Firmware upgradeable 

Rumour has it the MD-2017 could arrive sometime in March 20-17. However, no official release date has been set. For the latest updates on this new radio, Keep checking in at Buy Two Way Radios subscribeto our blog!”

Technician License Class – Black Forest, CO

Time: Sat Feb 25 and Sat Mar 4 (8 AM to 5 PM) 2017

Location: Black Forest Fire Station 1
(intersection of Burgess Rd. & Teachout Rd., Black Forest, Colorado)
Sponsored by the Tri-Lakes Monument Radio Association

The FCC Technician license is your gateway to the world-wide excitement of Amateur Radio, and the very best emergency communications capability available!

  • Earn your ham radio Technician class radio privileges
  • Pass your FCC amateur radio license exam right in class on the second day
  • Multiple-choice exam, No Morse Code Required
  • See live equipment demonstrations
  • Learn to operate on the ham bands, 10 Meters and higher
  • Learn to use the many VHF/UHF FM repeaters in Colorado
  • Find out how to participate in emergency communications

For more background on ham radio, see Getting Started in Ham Radio.

Registration fee: $30 adults, $20 under age 18

In addition, students must have the required study guide:

HamRadioSchool.com Technician License Course
Second Edition, effective 2014 – 2018, $21.95

Advance registration is required (No later than two weeks before the first session, earlier is better, first-come sign up basis until class is full.)

To register for the class, contact: Bob Witte KØNR

Email: bob@k0nr.com  or Phone: 719/659-3727

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