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Hi Pat Yes I did send Graham a thought that if he
can get the old crystals open he might be able to move them down by
"mechanically loading them" the easiest way is adding some mass by plating some
copper on them electrolytically. It was done with the FT-243 (or was it 241...I
cant remember these days) the one marked "54th harmonic" and that were used for
470kHz IF SSB filters in the 1960s.
Lapping them with "the famous foaming clenser" (
Ajax scouring powder for the younger members :-)) ) will only move them up
in frequency. Pete is right. the worst problen with lapping is getting and
keeping the faces parallel. Non-parallelism is the quickest way to lose
activity.the other problem is microscopic chips off the edges. The best way is
to "ring" several similar thickness blanks onto a half inch thick glass "flat"
with hot wax and lap them on a sheet of plate glass. They stay fairly
parallel like that. Etching does help as it removes the damage layer induced by
the lapping. The etch rate slows as you get through the damage layer, but if you
etch too far you can lose activity. This may be due to rounding the edges but it
can alsi e due to leaving microscopic particles of lapping powder embedded in
the surface, sticking up. Proper lapping compound is very accurately sieved for
calibrated grain sizes. Sometimes a large grain will gouge a minute trough and
the etch will deepen it. Its 50 years now since I was in the crystal lab, and it
always struck me as more of an art than a science. The best techs were from the
optical trade. I believe toothpaste is quite good as a fine grade lapping
compound but I never tried it.
Most of the plated crystals were finished by
measuring them in the vacuum chamber whilst evaporating gold onto the electrode
areas. They move a little when mounted up but that can be taken up with the
capacitive loading. A good tech knows where to stop plating to get spot on the
spec. I was an interloper in the lab because I was working on silicon not
quartz :-))
Alan
G3NYK
----- Original Message -----
Sent: Thursday, April 11, 2013 8:54
PM
Subject: Re: LF: Wanted 10XJ or FT243
XTALS Range 236.25 236.75 KHz
I'm glad you've just popped up on this xtal topic
Alan. I was just going to recommend that you be contacted as a probable
Guru.
73
On 11/04/13 20:26, Alan Melia wrote:
Interesting Pete I didnt get two that time. I
had it happen the other day Idont know whether there is congestion (kids
doing holiday projects) but I hit "send/receive" I got all the receive
messages but got an error on send, and the message wasstill in outbox so I
sent it again......and got two copies from the reflector. So I guess te
server didnt ack the receipt the first time although it did receive the
messages.
That's more like BOGOHP :-))
Alan
----- Original Message -----
Sent: Thursday, April 11, 2013 7:17
PM
Subject: Re: LF: Wanted 10XJ or FT243
XTALS Range 236.25 236.75 KHz
Pat there's something up with your e-mail because it keeps
sending the same thing twice? i.e. two e-mails for the price of
one.
73 es GL Pete M0FMT IO91UX
Well, you might have been happy,
Pete. I discovered that the family cat's whiskers wouldn't work with a
bit of coke and we had to go back to a pair of baked bean cans and
string!
On 11/04/13 16:20, M0FMT wrote:
And we all live in a hole in the road but we were
happy!!.....:0)
73 es GL Pete M0FMT IO91UX
And Wireless Set No.17 for
£2:19:6 (2Volt accumulator and HT Battery 10/- extra)
And
we're all getting older!
73
On 11/04/13
12:18, M0FMT wrote:
Hi Graham
How young you are my introduction to Tottenham Court
Road (Proops?) , Lisles Street (GW Smiths), Charring Cross
and The Edgeware Road about 1956. Aaaaah those were
the days. learnt a lot about
Radio, Life, the Universe and everything there......
hee!
Got my R107 from Lisle Street with money save from my
apprentices pay. Carried it (abt 1 CWT) via bus to Kings
Cross in the days when the conductor would jump off the bus and
give you had to get it on board........ imagine that on a "Bendy
Bus" today. See http://www.retinascope.co.uk/lislestreet.html for
the full story.
OK on the stick info yes but I am CW only really can't
get too excited about sterile data although as you know I do
partake occasionally.
73 es GL Pete M0FMT IO91UX
R Pete
Well , its possible to use the emergency
vfo , but that results in a very
unstable signal , I remember down
the Tottenham court road , there where tea
chests of crystals , but that was 1970 ..
seems a lot of the traditional
firms have closed ,
One of the £5 dds with a
driver would work , but they want
to keep it standard
DS - That's really the
'correct' situation , that -33 db
decode, -3 db lower than normal was
a good indication that the
system is working , over
ranging the a/d is the only
problem . I think dynamic range is 60 d b
after processing , is it 3 db per
bit ? 8 bits , 24 db + 3
that's 27 dB ? 500:1 ? ,
but by removing qty
2 mixers and 2
oscillators , [ may be 3
oscillators 1 , hf-up-conv 2 , pll conv
osc 3 ref osc ) that is a
lot of noise + jitter removed from
the signal path as well as
imd from 2 mixers , I found a
attenuator helped for mw and I
have a mw-filter , which cleaned
up sw bands ...... nice to have
a panoramic display , 2 mhz this time ,
the ra17 was 1 mhz and 28
valves + 20 ish > in the radio
73-G.
Sent: Thursday, April 11, 2013 10:47 AM
Subject: Re: LF: Wanted 10XJ or FT243 XTALS Range
236.25 236.75 KHz
OK Graham
Thought it was home brew retro.......... I am in that
mode and think everbody else is! What do you do at the moment
inject a Sig Genny?
Have you checked the net or checked out Vincent
- QuartzLab etc?
Anyway what's that master osc circuit. I build from
old RADCOM (pre 1975 when they published real amateur radio) and
PW,QST etal. I use modern xtals with no known issues. Well
trying to get third overtone for 10m not to chirp is an issue
with me at the moment.
OK yes got a stick on its way didn't want to tear up
my existing upconverter design. But not sure there is much wrong
with the UC approach it works for me. But want to try the direct
approach. Do you get much Cross mod and IM
products?
73 es GL Pete M0FMT IO91UX
Ok Pete
Q where to have them made ?
The set , Marconi Ocean span
1950's valve tx needs the
big rock's as the oscillator
pass's quite a lot of
power via them ...hc6u are no
good , drive level is very low - the ones fitted
are the wired- gold flashed ones ,
so cannot etch into the band ...
the gang want to keep
it standard
73 -G.
Ps waiting for qty-3
£6 dongles : )
Sent: Wednesday, April 10, 2013 11:43 PM
Subject: Re: LF: Wanted 10XJ or FT243 XTALS Range
236.25 236.75 KHz
Hi
If you want to spend a small fortune get them cut.
However build a Mixer VXO from El cheapo standard xtals and or
old PMR rocks. Then at your next rally buy a couple of Screw
together 10xj or FT243 rocks of any frequency and put the
El-cheapo xtals inside. And Hey Presto you have Retro
rocks.
I have a small all valve 472 tx that uses 6.00
-6.472=0.472 vxo-able a couple of kc/s 12ax7-6am6-6cl6=
4wattso/p. Local QRP rig.
Hope this helps
73 es GL Pete M0FMT IO91UX
Wanted 10XJ or FT243
XTALS Range 236.25
236.75 KHz
Q Is there any manufacture
of crystals in this range
?
Or Surplus items
available
QTY 1 or 2 off
TNX- Graham
G0NBD --
73 de pat g4gvw
es gd dx
qth nr Felixstowe
East Coast UK --
73 de pat g4gvw
es gd dx
qth nr Felixstowe
East Coast UK
--
73 de pat g4gvw
es gd dx
qth nr Felixstowe
East Coast UK
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