Saturday, September 10, 2011

Sept 10, 2011 B-17 Radio Work

Got a chance to spend some time working in the B-17 this afternoon to finish up a few things in time for next weekends special event station that we'll be operating from the radio compartment.  I met Kevin-KW4B at the museum around noon.  We got a quick brief from Rocky and Jeff on the new external aircraft power switch that they installed behind an access panel in the left wing inboard leading edge.  This was a great idea as it gives us an external shut off switch to kill aircraft power if needed without the need to climb back up in the aircraft.  See picture below.  I showed Kevin where the 12v and 24v batteries and power switches are in the cockpit and walked him thru the aircraft power application procedure.

We were pleased to see that Jeff Hoopes had installed two station lights and a dome light in the radio compartment.  One station light is over the radio operators table and the other is over the Lianson transmitter.  Jeff put in a nice toggle switch panel on the bulkhead to control each light which are run on the 12vdc circuit.  Again, forgot to take a picture but will next time. 

One of the tasks today was to install and test the new LDG KT-100 external antenna tuner.  As you'll see in the picture, we mounted this right on the Kenwood TS480 transceiver under the radio operators table.  This tuner will allow us to better match the radio to the external HF antenna on all of the amateur radio bands.  The Kenwood TS-480 internal tuner wasn't quite getting it done on a couple of the bands.  This KT-100 is designed to work with the TS-480 using the included control cable so that you don't have to physically press the tune button on the tuner.  You simply press the tune on the TS-480 and it tells the LDG to tune automatically.  Worked great the first time and we were able to tune beautifully on all bands (except 160 of course).  We even went ahead and made a few contacts and everything worked fine. 

The other task today was to install and test the low power FM transmitter that will be used to carry the receiver audio out of the aircraft to be heard on any FM broadcast radio in the museum.  Simply plug the headset jack on the BC-348 into the audio jack on the FM transmitter and away we go.  This allows visitors to the museum to hear us operating the radio station without going in the aircraft.  This little transmitter puts out 500mw (that's half a watt) and can be heard across the entire museum and in the front parking lot.  Pretty good in a metal building with a half watt.  This idea was the brainchild of Carroll-WX4Y and it worked well when we had our first official broadcast from the compartment back in July.  We also experimented with inserting the Kenwood audio into the other audio jack on the FM transmitter so that you can here either radio that is selected.  That was Kevin's idea and it worked great.

Once we were happy that we had accomplished our objectives for the day, we cleaned everything up, powered down the station, turned off the 12vdc and 24vdc switches in the cockpit, turned off the external power switch then disconnected the external battery charger.  Once the aircraft was buttoned up we disconnected our external HF antenna at the junction box and called it a day.  A very productive day.

We are looking forward to next Saturday, Sept 17th when we'll be operating the station all day long to celebrate the 64th anniversary of the U.S. Air Force.  This will be the longest period of time so far that we'll operate the station (old gear and new) so we're anxious to see how everything performs.

Guy, K4GTM

Newly installed LDG Antenna Tuner and Low Power FM Transmitter under the Radio Operators Table
External aircraft power shut off switch

External battery charging system using the original external power generator connector

Sunday, September 4, 2011

Hallicrafters S-53A Restoration

Hallicrafters S-53A Receiver
 Like I don't have enough projects at the moment.......I picked up a Hallicrafters S-53A Receiver from my good friend Tom Hoover and I've decided I'll go ahead and see if I can do a basic restoration on it.  This model was manufactured between 1951 and 1957.  I haven't searched by serial number to see if I can determine exactly which year yet.  Of course it was built in Chicago at Hallicrafters.  The retail price on these in 1951 was $89.50.

The radio is in pretty good shape considering it's age.  It's missing the band selector knob and the Standby/Receive toggle switch.  The toggle switch should be easy.  I'll have to find the band selector knob somewhere.  Hopefully original but will use a suitable substitute if necessary.  It has all eight tubes (one is broken) and they appear to be original as they have Hallicrafter printed on them.  Wow.  That makes them about 60 years old.  If they had been replaced some where along the way they would likely be RCA, Sylvania, etc.  I'll probably end up replacing some or all of the capacitors based on what I see when I open the bottom section.  The paper caps will certainly need to be replaced.  The case will need some cleaning on the inside and out but is in good condition.  They built stuff to last back then.

I was excited about the original tubes but was sure that they would be bad after all these years.  My plan was to borrow a tube tester from Carroll Baker, WX4Y.  The same one we use to test the tubes in the radios of the B-17 that we are restoring.  However, Ralph,W4REQ heard me talking about it and offered to lend me a Heathkit Tube Tester that he got from the estate of David Rosenthal, WD4FIH(SK).  Another HAM in town, Mark, KK4AMC was also in need of the tester and he went by picked it up from Ralph and decided to actually buy it.  So I borrowed it from Mark on Saturday and finally got the chance to test the tubes on Saturday night. 

I'm fairly familiar with tube testers from my time in the Air Force but I took a look at the intructions anyway and in a few minutes I was testing tubes.  I was pleasantly supprised to find all seven of the tubes working and passing all the tests!  I still need to replace the one broken tube and there seems to be an abundant supply of 5Y3GT rectifier tubes available via ebay.  My friend Jere, KT4ZB is going to check his old supply of tubes to see if he might have one for me. 

Six Bands

View of the back of the unit

Serial Number

Original paper lable

View looking down into the unit

Different angle

View of the hinged top cover

Hallicrafters 6K6GT Tube

In the Heathkit Tube Tester