Fantastic Insulators
We believe these fantastic insulators were used to form the giant helices used in applications like the coils for the Alexanderson multiple tuned antenna.
We have one small example of such an insulator that is native to the Bolinas transmitter site. It was badly broken and is now held together with wire.
The large insulators are not original to the Bolinas site but we believe they represent the type that may well have been used there as part of the Alexanderson antenna and possibly even the antenna for the 230kW Marconi rotary gap transmitter that was installed in 1913.
These insulators were mounted on poles or other vertical support, their long dimension at 90 degrees to the support. The cables comprising the helix were laid in and supported by the grooves in the insulator.
MRHS members Bill Ruck and Paul Shinn made the acquisition of these insulators possible through their personal contributions. We also wish to thank Bill Meier who contacted us about the insulators and the previous owner who made them available to us.
We've received this interesting information about the insulators from collector Don Howard:
A friend that knows of my interest in antenna insulators sent me a link to your page with the "Fantastic Insulators."
Here's a little more information about your insulators.
They have been well known in the telegraph and telephone collecting hobby for a number of years and were mistakenly rumored to be cable rack insulators from within submarine hulls. I collect radio-related insulators and had my doubts about the submarine story but couldn't prove anything until I stumbled across a couple of articles in the Proceedings of the IRE identifying them as tuning coil insulators. I provided pictures from the articles to the National Insulator Association and they published them to their web site http://www.nia.org/notins/nons6.htm which is where I assume Don House acquired them.
If you would like to read more about the insulators (and give credit for the pictures on your web page) the references you seek are:
"Designs and Efficiencies of Large Air Core Inductances" by W W Brown and J E Love, Proceedings of the Institute of Radio Engineers, December 1925.
"Main Considerations in Antenna Design" by N Lindenblad and W W Brown, Proceedings of the Institute of Radio Engineers Vol 14 No 3 June 1926 pp. 281-390.
The references for your pictures:
"Figure 2 & 3" appeared on page 757 of the December 1925 article.
"Figure 10 & 11" appeared on pge 763 of the December 1925 article.
The December article indicates that coils using the insulators were tested at RCA's Tuckerton Station. Since Tuckerton dates from after WWI, I think we can be certain that these were in no way related to Marconi's antenna. The article does confirm their use with the Alexanderson alternator, however.
Thanks for the interesting web site. I hope that you find this information helpful in your documentation.
73,
Dan Howard
