R-808/GRC-14 Military Receiver

This is a vintage Military R-808/GRC-14 general coverage receiver. It is a single conversion superheterodyne receiver covering 2-32 MHz. I believe these were issued to the US Marine Corps in the 1950's.  It's the kind of radio you might see mounted on the back of a jeep in the middle of some jungle or in some command center hooked to a teletype machine.  It was one of my dad's garage sale finds that I picked up for care and feeding. 

I didn't perform any repairs on this radio, but I had a fun challenge trying to figure out how to power it up and listen to it.  Since it was made for military use, there were no labels or standard power plug, just two mysterious looking sockets on the front and a handwritten D-J.  What was the D-J? Perhaps a previous owner's initials?

After some creative Google-ing, I found out that the front power connector (Plug J-1506 ?) has pins for 115V power input on pins D, and J. That explained the mysterious D-J.  I fashioned a plug using some wire connectors.  The radio is apparently also made to work on 28V for ship use on pins A and E.  However, I did not test this.

I searched around some more to determine what to do with the Audio connector. I found that this radio was meant to pair up with a 600 Ohm LS-166 speaker using a "U-77" connector.  I searched around on the connector and found that audio comes out of the radio on pins A and B. For testing, I simply used a small 8 Ohm speaker I had in my junk box. I powered up the radio and was able to listen to some AM stations including WWV at 15.00 MHz.

I opened the radio up to take a look inside.  This radio is very well sealed and amazingly well built. I expect you could use it at the beach while sitting in the sand and surf and still be OK.  It's also, quite heavy.   Here you can see the large circular drums that contain the printed frequency readout.

Notice the bright blue Selenium Rectifier.

 

Apparently, you can't use this radio above 10,000 feet.  I suppose that's good to know if you are carrying it up into the mountains. Insides show that this radio was built by Federal Telephone And Radio Company.

Right Side

Bottom of the radio. I counted 23 tubes total in the entire radio.

Links/References

• Video of a R-808 being used by a Japanese Military Radio Club 
• Antique Radio Forum Posting with informaiton about power plug
• Antique Radio Forum Posting with History and Photo
• Someone's write up in Italian
• Another R-808 page with Pictures.
• Reference to these being used on the M38A-1 (Jeep)

Atwater Kent Model 70

This weekend's Radio Projects were an Atlas 210x HF transceiver and an Atwater Kent model 70 console radio.

This particular Atwater Kent model 70 radio is very special. My Great Grandparents purchased it new in 1930 from Hale's Department store in Downtown San Jose.  The store was located on the corner of First and San Carlos streets which is now the San Jose Silicon Valley Chamber of Commerce.  Here is what the area looked like at the time.

I picked it up from my grandfather so I could restore it as a family heirloom. It's been stored in his basement for decades. Other than having some scuffs and some finish damage from a leaking can of tomato paste, the radio was in pretty good shape.

Here's a picture of the Atwater Kent Type L" chassis. It''s a TRF design as you can tell from the multiple air variable capacitors.

Instructions mounted in the cabinet.

Upon first inspection, I found that the 80 rectifier tube had been swapped with one of the 45 audio output tubes.  I also noticed that the power transformer was not original.  I wasn't sure if the tube swap was intentional or not.  These tubes look very similar so someone might have made a mistake.

Normally, I'd trace wires before doing anything with the radio but Grandpa had insisted the radio was working when it was put away. I decided to bring it up slowly on the Variac.  Unfortunately, the radio  did not show any signs of life.  I needed to know if the tube swap was intentional or not so  I opened up the case and checked underneath.

The tube swap was certainly not intentional.  The transformer leads went straight to the socket that was intended for the #80 rectifier tube. Was some ancestor playing with the radio perhaps?  I put the tube in the correct socket, but the radio was still dead.

That transformer looks like it has been leaking tar.  Was this from the original transformer or the replacement?  The bottom of the radio had a paper cover and had tar goop on it.  Hopefully the transformer was OK.

A little more inspection revealed a 2 amp fuse on the power input that had blown. Problem #2 was found. 

Fortunately, I keep fuses in stock.  Though, this fuse is also readily available on Amazon.  If you need an assortment, they also have large assortments for sale cheaply so you can build up your stock as well.

This brought the radio to life!

There was still more work to do.  The tuning dial was slipping.  This was due to a rubber bushing that was supposed to be stuck tight to the tuning shaft.  It was pretty loose after sitting on there for 82 years. 

I could have gone on a hunt for a replacement bushing. However, since it was rubber, I simply used rubber cement to glue it to the inner bushing.  This took care of the tuning for now. 

I then reassembled the radio and waxed the case with carnuba floor wax.

The radio has dials for tuning, tone, and volume. Here's a quick demo while the radio was playing.

Unfortunately, there's still going to be some more work to do on this radio. After playing it for a while, the acrid smell of burnt tar started to fill the room.  Ugh!! Guess that transformer is suspect after all.

Atlas Model 210x

This weekend's Radio Projects were an Atlas 210x HF transceiver and an Atwater Kent model 70 console radio.

The Atlas Model 210x was first introduced in 1973.  It was quite revolutionary at its time as being all solid state. (No Vacuum Tubes).  This particular specimen was found in my dad's backyard. He had purchased it at a yard sale and covered it in a plastic bag. I rescued it while visiting my dad.  When I opened up the chassis, I found that one of the capacitors on the audio board was blown.  It also burnt the side of the adjacent capacitor and spewed a mess on the circuit board.

I decided to replace both capacitors. (22mfd@16v and 100mfd@16v.) and also clean up the circuit board. Here is the audio board with the new capacitors installed. You can see them in the upper left hand corner of the circuit board.

I re-installed the audio board and powered up the radio.  It performed reasonably well and I was able to hear stations between Wisconsin and California on 80M, 40M, and 20M using a long wire antenna installed in my backyard.  I powered it with a 15A 12V power supply which also came from my dad's collection.

I have not yet tried to transmit with the radio. When I do, I'll update this posting.

Google Chromebooks For Education

SCVi's New Chromebook Cart

Our fund raising focus for the 2011-2012 school year is Technology.  This focus has allowed us to  purchase some really wonderful items for use in the school such as a Mac Book Air Cart, Digital Microscopes,  iPads, and a Google Chromebook Cart.  The Google Chrome Book is a great device for student use with its small size, light weight, 8 hour battery and hard plastic case.  Ours came with a Google Branded Bretford Mobility Cart, color laser printer,  and 30 chrome books.

What is a Google Chromebook? 

Simply put,  a Google Chromebook is a small inexpensive laptop that runs the Chrome OS.  If most of what you do is on the web, it's a wonderful tool to get your work done.  Here's a nice video from Google that explains it pretty well.

Benefits Of A Chromebook

For classes that mostly work on the web using things like Google Docs, WikiPedia, YouTube, E2020, EdLine and others, the Chromebook does a good job of fitting their needs. The Chrome Book also has access to a wealth of applications in the Chrome Web Store.  Many of the things you'd want to do on your computer are available in the store.  We have heavy use of Google Docs in grades 6 and up so the Chromebook works well for these grades.

In order to take full advantage of our Chrome Books, our school is also implementing a Google Apps For Education Domain.  This is something that should be done before you  purchase and Google Chromebooks.  With the Google Apps For Education domain, every Learner will be issued a Google ID.  Using this google ID, the student can log into the Chrome book and it is transformed into their own device just by logging on.  When they are done with the device, they simply log out and it is ready for a different student to use. All of their Google Documents and content are stored in the cloud.

I think the ability of the device to work for multiple users so nicely is the single greatest asset of the Chromebook. You can wheel a cart of the devices into a classroom, everyone logs on with their Google ID, and the device is transformed into their own personal computer.  All their Google Documents  and School E-Mail are available.  When they log out, it's ready for the next student.  It doesn't matter which Chromebook you pull from the cart, as soon as you log on, it is yours.  All this power comes built into the Chromebook and there is no extra work to be done by IT staff. 

 

Chrome Book Cautions

Though, certainly an innovative device,  the Chromebook is not a full laptop where you can install anything you want.  The beauty, but also the limitation is that the Chromebook only runs web applications. The Chromebook supports Flash, but not Java, so you can use your flash based web sites.  Any Java based sites you use will need to be ported to HTML5.  If you prefer using installed native applications like Open Office, iMovie,  Outlook, or Photoshop, the Chromebook is not for you.

Another thing to pay very close attention to are the long term costs. The initial purchase price of a Chrome Book can range from $350 (From Amazon) or $450 (From Google).  The $350 Amazon device has no recurring fees, but is primarily designed for family/personal use. You can not manage it from the management console or tie it to a Google apps domain. The advantages of the $450 Google device is that it has a longer life battery, a stronger plastic shell, and can be registered specifically to your own Google domain. (Allows use of the management console). When registered with your own Google domain,  the machine can be limited to only allow logins from your domain. However, there's a catch to all these benefits.

The first year of management on a Chromebook comes for free. After the first year, Google expects to charge $5 per device, per month.  This is $60 per year per device (13% of acquisition cost).  For a cart of 30 Chromebooks this is $1800 per year!! Since our budgets can change from year to year we usually abstain from products that have recurring fees of any kind, especially large fees like this.   I think this turns the tide somewhat against the Chrome Book and we would be unlikely to spend this much just for the ability to use the management console.

When you add up the cost of the management console over 3 years, other technologies become more competitive.  Here's a quick comparison of a few that we use at our school.  Note that this does not include the cost of IT staff to manage any these devices. Though, we do very minimal management on any of our devices so our cost is pretty low anyway.

Device	Initial Cost	30 Device Cart Cost	3 Year Cart Cost  With Recurring Fees
Google Chrome Book	$450	$13,500	$17,100
Google Chrome Book (Amazon)	$350	$12,500	$12,500
iPad	$489	$16,500	$16,500
MacBook Air	$930	$27,300	$27,300

 

Summary

The Chromebook is an innovative device that fits the needs of some of our classrooms really well.  Though, it's not a full laptop and does not work for everyone.  It's great for folks who work entirely on the web already.  The pricing for the device is competitive, but the management console quickly raises the price to where other devices become a better value. At the price Google is asking right now, I think it is very unlikely we would pay the recurring fees.

At SCVi we allow a great deal of flexibility in the technologies used in the classroom.  You may see Ubuntu Linux, iPads,  Mac Book Airs, Windows Netbooks, or Chromebooks.  We make multiple platforms available to our teachers and students and  then see what works for them. I don't expect that we'd ever commit to any one platform.  Many of our facilitators come up with their own ideas and innovations. This means our IT department  must be flexible, adaptable, and constantly learning. 

Links And References

Here are some links that folks may find interesting.

• Jim Klein of Saugus Union School District's posting about Chrome OS
• Joe Wood's postings showing contrasting points of view about iPads and ChromeBooks: Part1, Part2, Part3
• Cloud Craft - Chromebook Carts
• Google Case Studies on Chrome Books 
• Chromebook Business and Education Video From Google
• Chromebook Security Video From Google