1920s Amateur Transmitter

~Now know to be incorrect history~:

This collection of parts, which appears to have been a transmitter, was allegedly used by Marconi in Fordingbridge, Hampshire, UK. However, it seems unlikely that it was used by Marconi himself. The story that accompanied it was that the former owner's father worked for or with Marconi.

The equipment has been returned to its original custodian.

It may have been part of an early 1920s amateur station. The McMichael variable capacitor (16) probably dates from around 1921 and is looks like the most recent part. The Negretti & Zambra, loose coupler is similar to one pictured in Harmsworth's and may date from around 1918. Pictures 7, 8 & 9 show what appears to be a Marconi spark coil dating from the early 1900s. It is a replacable primary type and may have been removed from its original base. These were sometimes used as HT transformers but I can not find evidence of any rectifiers or smoothing in the kit that I have. Harmswoth's Wireless Encyclopaedia has details of a hot-wire ammeter similar to that shown in picture 15. The relay is estimated as being from 1918. Remnants of a crystal set (18) were also with the collection.

It is a guess but the rings, in the lower middle of the frame, look about the right shape to hold an early transmitting valve. This figure, from Harmsworth's, shows the type of valve but these examples would be too large. A similar style of construction can be seen in the equipment inthis picture, of J.L. Baird, from "Television" magazine, dated April 1928. The two insulated rings, in picture 10, are ~33mm inside diameter and are spaced at about 90mm. The spacing is adjustable. The two larger rings are connected together and are about 93mm inside diameter.
Addendum: Later information suggests that is was a Poulsen arc based transmitter.

Click on thumbnails for larger pictures.

1
  thm_DSCN9526_large_coil.jpg  
 
2
  thm_DSCN9527_large_coil.jpg  
 
3
  thm_DSCN9528_large_coil.jpg  
 
4
  thm_DSCN9529_n+z_coil.jpg  
 
5
  thm_DSCN9530_n+z_coil.jpg  
 
6
  thm_DSCN9531_n+z.jpg  
 
7
  thm_DSCN9533_spark_maybe.jpg  
 
8
  thm_DSCN9534_spark_maybe.jpg  
 
9
  thm_DSCN9535_spark_maybe.jpg  
 
10
  thm_DSCN9536_main_front.jpg  
 
11
  thm_DSCN9537_main_back.jpg  
 
12
  thm_DSCN9538_large.jpg  
 
13
  thm_DSCN9545_relay.jpg  
 
14
  thm_DSCN9546_relay+tuner_coil.jpg  
 
15
  thm_DSCN9547_meter.jpg  
 
16
  thm_DSCN9548_capacitor.jpg  
17
  thm_DSCN9672_small_coil.jpg  
 
18
  thm_DSCN9673_xtal_set.jpg  
 
TX Valves

2KZ April 1928

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