One of the best things about the MRHS is the people who show up, see what we're doing, and want to be a part it. Even better, everyone seems to find a project they find challenging and fun that also contributes to the overall program.
Some time ago a group of current and former HP engineers paid a visit, looked around and started working on some of the jobs that needed doing - of which there are no end. But they wanted something more. They made the breathtaking commitment to restore a 1950s vintage RCA "H Set", the most complex model transmitter at the Bolinas transmitting station... and in the worst condition.
Maybe they didn't fully realize what they had taken on. But pretty soon it was too late. They had become True Believers and the work they did is nothing short of astonishing - as you will see in the photos below.
At this point we turn the narrative over to Greg Farrell of the "H Set Team". As you'll see from his fulsome prose, he fully understands the drama of the project and the importance it has in the preservation of our maritime radio heritage.
The Saga of Bolinas RCA H-set Transmitter #298
|The T-3 "H Set" as shown in the RCA technical specifications manual |
It was a glorious May 1959 at RCA Bolinas. Another 20kw Independent Sideband T-3 Transmitter had just been delivered by Santini Brothers. Within 3 days, she had successfully sent RF into a dummy load during initial power-on testing. #298 was destined to be the primary point to point circuit between the Bolinas transmitting station and the island of Guam. There provided faithful service to her customers and to the Corporation for 33 years. In her later years, after the point to point service was discontinued, #298 was modified CW service and made the KPH signal stand tall around the world on 13.002Mc.
The Independent sideband transmitters were designed for near continuous, long-range transoceanic and transcontinental communication on frequencies ranging from 4 Mc to 30 Mc. They could operate in single-sideband, double-sideband or independent-sideband mode. The carrier in any mode could be operated from full carrier to no carrier. The newly developed independent-sideband mode allowed for intelligence to be transmitted on both upper and lower sidebands at the same time, to a receiver such as the RCA model SSB R-3, at the other end in Guam. She was truly an engineering marvel of commercial radio communication of her time.
For 33 years she served, and then sometime in 1993 or early 1994 she was silenced forever. For nearly two decades she sat amongst her now silent H-set brothers and sisters in the south-east corner of Building 2A. Day in and day out, wisps of cool moist and salt laden air from the Bolinas headlands invaded her being, finding every open pore, every crack, every bolt, anywhere RF had lingered to attract salts forever building from the air passing through, so necessary for cooling. The now moist salts began eating away at her metal and electronics, making her incapable to ever produce RF signals again. Or so some lesser mortals thought...
In January 2011, a group of MRHS volunteers accepted the challenge of restoring #298 to operational status. Due to her condition, a 100% dis-assembly of the entire RF-Power Amp assembly had to be undertaken, as well as complete restoration of nearly everything else, both mechanical and electrical. This was to be no easy task, as nearly every bolt or screw had become corroded and frozen in place. 6/32 screws snapped off heads at the least amount of torque.
Testing and work continues to this very day. Once again #298 is producing RF into a dummy load, exactly has she had done back on May 21, 1959. Problems, yes! But #298 had seen these before, just as she had experienced back in 1959 when she was first powered up (we have the engineer's notes that attest to this!).
Recently for example, the low pressure blower motor had to be replaced; and PA Plate idle current (key up) is still too high at 1.5 amps. Radio engineering experts, even former H-set techs such as Warren "TR" Reese, last transmitter engineer at KPH Bolinas, all long since retired, have been called upon by Transmitter Supervisor Steve Hawes, to share any knowledge they might have about the idle current and other issues faced by our team. Steve Pazar and Bob Dildine have taken the lead in our own H-set team, to resolve these issues, along with expert help from Tom Harris and Andy McClean to replace the failed Peerless motor, with a Reliance motor bought by RCA back in 1992.
Truly, everyone in the H-set team deserves a heap of credit for the work they have done over the last year and half, often taking on tasks which had no precedence to resolve. Literally hundreds and hundreds of volunteer hours have gone towards this project.
|The IPA deck with two 4CX250Bs as found. Would you have the heart to take this on? |
|The rebuilt IPA deck with the RF power amp deck above. Each of the 4CX5000 sockets in the RF deck had to be completely dis-assembeled and rebuilt from scratch - just one small part of the total restoration. |
|Two 4CX5000s stand proudly in the RF power amp deck, shown in the final stages of re-assembly in the control room at Bolinas |
|Steve Pazar keeps a careful eye on the meters as he brings the transmitter back to life for the first time in decades in a pre-service test. |
The H-Set Team consists of:
Steve Pazar - W6SSP: project engineering lead, PA 4CX5000 sockets, screen by-pass caps, HV DC power supplies, meters and more
Stan Jaffe - WA6DHM: hardware extraction and PA Assembly removal and re-installation and more
Larry Nutting - K7KSW: Counters, tank circuit tuner, rack signal sources, VU meter, PA unit heater and more
Kurk Radford - K6RAD: DC power supplies in the rack, cabinet blower and more
Bob Dildine - W6SFH: Main PA assembly and driver deck, driver plate induction tuner and more
Andy McClean : Motors, blowers, air filtration and more
Tom Harris - Pears Repairs: Motors, blowers, meters, receivers for the receive site, and much more
Greg Farrell - K6SRO: Power amp sockets, driver plate tuning air capacitors, sheet metal, PA unit heater, project photographer, documentation and logistics and more
John Felton - KE5RI: PA plate transformer heater and more
We'll continue to keep you all posted as we near that glorious day when #298 is once again transmitting RF into the ether, currently expected to be on the 15 meter band (K6KPH) for MRHS special events. And of course we will let you know when we officially push the "money button" to return #298 to the air!