Narrow-Bandwidth Television Association

I have been facinated by the jeffree cell ever since first reading about them, now that LED's and lasers can be modulated at high speed the jeffree cell is somewhat redundant, but I hope to build one, I have been trawling through my collection of NBTV stuff to gleen information,
amplitude modulation at 10mhz, using distilled water, I intend using a piezo.
Has anyone built one or have any advise on building one???, any help would be appreciated.

johnrpm wrote:I have been facinated by the jeffree cell ever since first reading about them, now that LED's and lasers can be modulated at high speed the jeffree cell is somewhat redundant, but I hope to build one, I have been trawling through my collection of NBTV stuff to gleen information,
amplitude modulation at 10mhz, using distilled water, I intend using a piezo.
Has anyone built one or have any advise on building one???, any help would be appreciated.

Hi i looked into this a while ago but i was still thinking of using a crystal but you would want this for nbtv so expect using a piezo might be good for low frequencies smaller band width.

This is the best link to a jeffree cell
http://www.bluehaze.com.au/modlight/UltrasoundMod.htm

The post i did some time back on the first laser television was interesting used something like that for the horizontal sweep.

i expect you would be using a laser for the experiments ..good luck..

thanks harry, that link is wonderfull, the most information I have seen on the jeffree cell.

This is of topic, I just received the newsletter and on the back page is a picture of spiral pins arrayed like a mirror screw by Karen, it says more details in next issue, sheesh have we got to wait that long????, i suppose patience is a virtue.

My original intention was to use a piezp plate for the jeffree cell, but the problem in getting actuators of the right size and mode of vibration has resulted in the decision to use quartz, again getting quartz in big enough pieces is expensive, cutting my own is the only option at present, I have bought a crystal point and am now building a cutting machine, diamond discs are available but a brass or copper disc with abrasive runs cooler but slower, but should avoid causing fractures.
I have lenses from the club shop, and glass plates from poundland, I have a feeling this is not going to be a quick project.

some info on cutting quartz oscillators here
http://www.vacuumtubeera.net/RadioBroad ... 928-12.pdf

johnrpm wrote:My original intention was to use a piezp plate for the jeffree cell, but the problem in getting actuators of the right size and mode of vibration has resulted in the decision to use quartz, again getting quartz in big enough pieces is expensive, cutting my own is the only option at present, I have bought a crystal point and am now building a cutting machine, diamond discs are available but a brass or copper disc with abrasive runs cooler but slower, but should avoid causing fractures.
I have lenses from the club shop, and glass plates from poundland, I have a feeling this is not going to be a quick project.

some info on cutting quartz oscillators here
http://www.vacuumtubeera.net/RadioBroad ... 928-12.pdf

Oh that looks like a lot of work ! perhaps a easier way would be to get a 40 or 50 khz Crystal and getting out of the case...that should do for nbtv bandwidth...i think if its around that frequency should still work what ever you can find so long as it fits the nbtv bandwidth.
Should go a bit quicker using a ready made one out of its can .

harry dalek wrote:
Oh that looks like a lot of work ! perhaps a easier way would be to get a 40 or 50 khz Crystal and getting out of the case...that should do for nbtv bandwidth...i think if its around that frequency should still work what ever you can find so long as it fits the nbtv bandwidth.
Should go a bit quicker using a ready made one out of its can .

Harry, I think the main problem is that modern crystals are too small (dimensionally) for this application.

gary wrote:

harry dalek wrote:
Harry, I think the main problem is that modern crystals are too small (dimensionally) for this application.

Oh okay Gary i will have to do some more reading ... the supersonic vibrations on the liquid ...could you use a few crystals if its amplification thing..perhaps a ultrasonic transducer might be a better idea than a crystal ?
but getting away from the original idea...

Well, it's really about moving a large mass of liquid for a large beam of light, possibly you could use multiple crystals, I suppose it's an area for experimentation, but, of course, that complicates things considerably, and you move away from Jeffree's very clear and proven instructions.

Jeffree states a crystal about 1"x1"x .010, the cell has a dimension of 10mm x ?, in the PDF, The ? dimension I am unsure of, it may be dependent on the size of crystal perhaps, If i can get this to work, the plan is to build a scophony system, I could use a laser as it would be easier, but the jeffree cell is so much more interesting.
At the back of my mind is the thought that if I can get the whole thing to work it may be possible to have an image using UV light, which could cure a photosensitive resin layer by layer to build 3d parts, which would make a 1930's system apply to modern use.

for interest, I cut open a 10mhz full size can to see what was inside, I hoped to see a bigger crystal, its about 7mm diameter with a resistor and IC.

I have been attempting to cut a crystal with the cutting machine, the machine is not yet fully finished but I thought I would have a play, it has a brass disc 7 1/2 diameter and runs at about 200 rpm (variable) my problem at present is the lapping media, I have very fine and very course but need to get some 150 grit, the fine just sits rubbing and the course grit does not seem to bed into the brass very well, it does cut but takes ages, I bought 2 diamond discs, 100mm dia and .8 thick, they start of very well but seem to loose the diamond coating after a while, maybe because I am running then too slow,

Hi john i just found these files which may be of use i forgot i had them !

Thanks yet again Harry,
Images like these really help, yesterday I left the diamond wheel cutting all day whilst I creosoted the shed, it cut about 1mm, I do have a diamond tile cutter but it runs at high speed, and I am concerned it may introduce tiny fractures in the crystal due to local heating, so lets hope the 150 grit (when I get some) with the brass disc will do a better job?.

I tried with course lapping paste, works well and cuts at a reasonable rate.