MRHS Newsletter No. 41
Dedicated to True Believers World Wide
27 August 2013

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> Headlines

o Denice Returns Home!

o Spark Transmitter Donated to the MRHS

o But wait, there's More!

> Denice Stoops Returns Home!


As we reported in Newsletter No. 40 our beloved Denice Stoops, who suffered a stroke while joining her third Military Sealift Command ship in Singapore, has returned home.


Paul Shinn of the MRHS Transmitter Department met DA at the airport and escorted her and her sister back across the threshold of Denice's home on the Bolinas Mesa, almost within view of the transmitter site. 


It will be remembered by most that Denice was the first female radiotelegrapher hired at KPH, this in 1979.  She came to KPH after four years at neighbor station NMC of the United States Coast Guard.  Thus it was particularly appropriate that her first visit back to the station last Saturday was also the day that many NMC personnel visited the station to participate in our Services of the Church of the Continuous Wave.


Naturally a group photo of this wonderful event was required.  So here it is...



Denice with her fans 

Denice specifically asked that we make her email address available for those who might want to send her a message.  She can be reached at .  We're sure she'd love to hear from you.


We hope DA will continue to join us for Services.  But for now we're just happy that she's home and back close to us.


> Spark Transmitter Donated to the MRHS

One of the best parts about letting fellow True Believers know about our project is that they understand that donations made to the MRHS will not end up on eBay or in some private collection.  Witness the donation of Radiomarine CRM-R6A receivers by the family of the engineer who designed them (see Newsletter No. 27).

Now comes Dr. David A. Hunt of Reno, NV.  He did us the honor of making contact to inquire if we might possibly be interested in the donation of a spark transmitter.  Of course the answer was "yes".  It took a while to pull together the mission to Reno but before two long Greg Farrell and Tom Harris of the H Set Team set forth over the Sierra Mountains.  Soon Mackay Radio and Telegraph Company Radio Transmitter 30-A, SN 31257 was on its way to its new home.

Transmitter in Dr. Hunt's residence before transport.  The top deck is the short wave transmitter, band change switch handle to the right.

Now we must talk of the history of transmitters, especially that of marine transmitters, in order to put this particular artifact in context.

We all know that the first ship board transmitters used a straight spark gap.  As the art of marine communications advanced these were replaced with rotary spark gaps and later with quenched gaps.  The latter had the advantage of being silent.

Wave change switch with positions corresponding to (L-R) 500kc, 467kc, 425kc and 375kc.  500kc is used today by KSM and 425kc is used by ships working KSM on its working frequency of 426kc.

Eventually vacuum tubes became rugged and powerful enough to be used in marine transmitters.  And at about that time the value of short waves became apparent.

Everything needed for maritime communications aboard ship - from the equipment to the operator - was provided by a communications company, an arrangement pioneered by the Marconi Company and carried on by RCA and the others involved in the field.  They faced a problem.  They had invested heavily in spark equipment.  But  now this equipment needed to be upgraded to meet the advanced state of the art.  What to do?

It was realized that the RF tuning portion of the typical spark transmitter was already suited for operation on the Intermediate Frequency (IF) band.  This is what we now call the Medium Frequency (MF) band.  So all they had to do is change the source of RF from the damped waves produced by the spark gap to the continuous waves produces by vacuum tube oscillators.

Spark transmitters were banned after 1939 so the conversion of 35217 came not a moment too soon!

The transmitter we now have is a superb example of this transitional period.  The spark gap was removed and a power supply built into the space.  Two tubes were installed on a sub-chassis.  That took care of the IF part.  Then a HF oscillator deck was added to the top of the transmitter for short wave work.

Transmitter loaded on suitably vintage hand truck for transport into the Bolinas transmitter gallery

Once we had this beauty safely in the Bolinas store room - home to many treasures by the way - we had a chance to really look it over.  You've all probably been in a similar situation, with a buch of radio squirrels poking and oohing and aahing and exclaiming "Ah-HAH!" as the layout and function of components come into focus.

The new arrival is pondered with reverence.  Transmitter BL-11, object of a previous recovery effort, is to the right.
It was originally thought that the transmitter started life as a quenched gap set since we've seen reference to such conversions in the contemporary literature.  But there is no space on the front panel of this transmitter for the rack to hold the series of quenched gaps.  So the current thought is that this was a rotary gap set.  The suspicion is that the gap was behind the panel where the power supply now is.  But that just a preliminary thought based on our first examination.

Rear view showing 866 rectifiers on bottom deck where the rotary gap may have once resided.  The power transformer is above with the tubes for the IF section above and to the left.  The HF deck is above the variometer (tube removed).

The IF (MF) transmitter is not crystal controlled.  The frequency is determined by a L-C network.  This arrangement remained common up through the 1990s and works very well at those frequencies.  However the HF transmitter is also innocent of crystal control.  On first inspection it appears to be a giant VFO. 

Portion of the HF deck showing the beguiling push-pull HF/IF band change switch.

When looking at equipment like this we can't resist casting our minds back to the days when men were men and radiomen even more so.  You have to wonder how, when using this transmitter, the operators knew where to set the frequency change vernier dial to the correct calling and working frequencies.  But then, as Larry Nutting of the H Set Team said, "That's what wavemeters are for!"  In fact Larry let it slip that he had just acquired a wavemeter of the same vintage as the transmitter so maybe we will be able to prove the truth of his statement.  Because of course we hope to put the HF deck on the air!

More to follow...

> But Wait, There's More!

As the recovery team was about to leave the home of Dr. Hunt he pressed into their hands a book.  It was "Contact at Sea" by Peter R. Schroeder.  Written in 1967, it covers the history of maritime communication up to that time.  None of us had seen or heard of this book before so we couldn't wait to read it.

The book makes fascinating reading.  But it's the names inscribed inside - names of those who have read it before us - that really make it special. 

Here are some names to conjure with.  Richard Johnstone... Could this be the same Richard Johnstone who was an op in the Bay Area and wrote "My San Francisco Story"?  And Thorn Mayes, famous radio historian.  Do you recognize others?

We're all engineers here so we don't admit of things that can't be rationally explained.  And yet... sometimes things happen.  Chief Operator Dillman recounts such an occurrence:

There I was, on watch at KSM soon after the book arrived.  Leafing through it, I stopped in amazement at the page above.  Just then the station phone rang.  It was... Thorn Mayes Jr. the son of Thorn Mayes!  He asked if I knew his father.  "Know him!?  I'm looking at his name right now!".  I don't know how you explain these things.  But I do know we're now in touch with the son of the great man who has promised to share items of radio history with us.





> Support the MRHS 


As you have seen above, we have another fun project on our hands - the restoration of the former spark transmitter!  We fund projects like this out of our own pockets - and are grateful to have the opportunity to do so.  But when fellow True Believers help with a financial donation it is meaningful beyond the amount of the donation.  It lets us know we're not alone and that there are others who understand and appreciate the work we do. 


If you find yourself with a spare few dollars and would like to help us carry on with the many repairs and restorations that are a way of life at the MRHS just click on the yellow button.



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