RR145/S (RR145/S)

Hello Friends
I found that "TUNING INDICATOR"-tube my basket. Now I thinking how methode this tube works and when it wos made and where. Its base are three letter DGL. Who knows?
BG: Eero Ukkola/FIN

To thank the Author because you find the post helpful or well done.

All I know: it is a glow discharge device. The indicating glow area ist proportional to the discharge current.
The usual application was in the early 1930's to feed it via a series resistor from the anode or the screen grid of the AGC RF tube. Strong signal made higher negative AGC voltage, thus reducing the gain of the RF (variable mu) tube, which in turn increased the anode/screen grid voltage and simultaneously gave a higher indication on the tuning indicator. The series resistor was usually adjustable (100 kOhm pot.) and an additional electrode  (>200 v fed through 1-2 MOhm) kept a minimum discharge when no signal was there and the RF tube at full gain i.e. at minimum anode voltage.
As an example have a look to the schematic of this Radio http://www.radiomuseum.org/r/saba_weltsuper_630wl.html

To thank the Author because you find the post helpful or well done.

Here is a picture of the indicator: Attachments:

• RR145/S (40 KB)

To thank the Author because you find the post helpful or well done.

Hello Eero: It is also used in the Koerting Transmare 38.
The neon discharge is proportional to the signal strenght as mention in other reply.
The effect of this indicator is great. Let me know if you want Photos of this working.
I wonder why was no longer used. Perhaps the cost.

Best Regards. Jose

To thank the Author because you find the post helpful or well done.