CR300 crystal set - UK Vintage Radio Repair and Restoration Discussion Forum

Colinaps · 21st Dec 2014, 3:26 pm

While the fabrication of a PSU for my CR300 is still fairly well down my list of priorities (the bench is still cluttered with HRO carcass), and idly fondling the tuning knob in the passing, it occurs to me that the set has an internal crystal detector for use when everything else has packed in.

Has anyone actually used one of these with the crystal detector?

73.

Colin.

ms660 · 21st Dec 2014, 6:04 pm

Ditto with the CR300 I have, nope not tried the crystal detector. I heard it was a Board of Trade requirement back then...True/False ?

Lawrence

JHGibson · 21st Dec 2014, 8:07 pm

The emergency crystal receiver was a Board of Trade requirement for merchant navy ships. It is 50 years since I tried out the crystal set ( you had to move the top cap lead from the !st RF valve over to a top cap like terminal on the crystal detector.
If I remember right, the detector consisted of a steel flat spring whacking down on a carborundum crystal. I recall that it was very insensitive but would not burn out when the transmitter was keyed.
John.

g4aaw pete · 21st Dec 2014, 8:08 pm

Hello Colin
the manual says:-

Colinaps · 21st Dec 2014, 10:59 pm

One feels the need to try with a germanium diode - I can't see carborundum being up to much but probably enough to work another ship a few miles away. I guess they used mcw or would the sparkers be expected to read clicks and ac hum?

JHGibson · 21st Dec 2014, 11:51 pm

We used MCW and on my first single operator ship we had a spark transmitter for a back up.
The crystal set could use the ships main transmitting aerial, Some 200 ft long and about 80 ft high. The ground was the best ever, the steel hull of the ship in salt water.
John.

21st Dec 2014, 3:26 pm	#1
Colinaps Pentode Join Date: Jul 2009 Location: Roxburghshire, UK. Posts: 196	CR300 crystal set While the fabrication of a PSU for my CR300 is still fairly well down my list of priorities (the bench is still cluttered with HRO carcass), and idly fondling the tuning knob in the passing, it occurs to me that the set has an internal crystal detector for use when everything else has packed in. Has anyone actually used one of these with the crystal detector? 73. Colin.

21st Dec 2014, 6:04 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: CR300 crystal set Ditto with the CR300 I have, nope not tried the crystal detector. I heard it was a Board of Trade requirement back then...True/False ? Lawrence

21st Dec 2014, 8:07 pm	#3
JHGibson Retired Dormant Member Join Date: Apr 2003 Location: Salt Spring Island, BC, Canada Posts: 368	Re: CR300 crystal set The emergency crystal receiver was a Board of Trade requirement for merchant navy ships. It is 50 years since I tried out the crystal set ( you had to move the top cap lead from the !st RF valve over to a top cap like terminal on the crystal detector. If I remember right, the detector consisted of a steel flat spring whacking down on a carborundum crystal. I recall that it was very insensitive but would not burn out when the transmitter was keyed. John.

21st Dec 2014, 8:08 pm	#4
g4aaw pete Heptode Join Date: Jan 2008 Location: Birchington Kent, UK. Posts: 596	Re: CR300 crystal set Hello Colin the manual says:- Attached Thumbnails

21st Dec 2014, 10:59 pm	#5
Colinaps Pentode Join Date: Jul 2009 Location: Roxburghshire, UK. Posts: 196	Re: CR300 crystal set One feels the need to try with a germanium diode - I can't see carborundum being up to much but probably enough to work another ship a few miles away. I guess they used mcw or would the sparkers be expected to read clicks and ac hum?

21st Dec 2014, 11:51 pm	#6
JHGibson Retired Dormant Member Join Date: Apr 2003 Location: Salt Spring Island, BC, Canada Posts: 368	Re: CR300 crystal set We used MCW and on my first single operator ship we had a spark transmitter for a back up. The crystal set could use the ships main transmitting aerial, Some 200 ft long and about 80 ft high. The ground was the best ever, the steel hull of the ship in salt water. John.