Does anyone know the load capacitance for older Uniden crystals

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GT390
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Does anyone know the load capacitance for older Uniden crystals

Post by GT390 »

I have had trouble trying to find crystals that will work properly in older Uniden radios, like the 2830/Lincoln and cobra 148DX. I was hoping someone may know what load capacitance the original spec was ?
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by Richk »

Dear GT390.
I have had XTAL's cut for uniden radios back in the day, Via Quartz LAB. Now what we found out is that the "ELECTRODE" Diameter on these Xtal's are at least 6mm this is the "Bonded" electrode to the Crystal, We had a few tries at this and this was the result, Other_wise you will not get the.
+/- 6 KHz (12 KHz) in total shift required. So when you order new Xtal's for these radios mention this and all will be good.
I do hope this helps.
73's
Richard G
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by SuperLid »

32pF
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cb4ever104
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by cb4ever104 »

viewtopic.php?f=53&t=58255
cb4ever104 wrote: 25 Aug 2020, 15:54 Hi All .

A while back I sent a 14.910 Uniden crystal to KRYSTALY in the Czech Republic for testing . The purpose was to see if they could reproduce crystals with the same specs (+/- shift) to replace dud , or create new crystals in Uniden/Ranger type radios .

They received my crystal and here are the test results .

Frequency: 14.915115 kHz / 1.OT
series resonance
ESR: 10.1 Ohms
C0: 4.759 pF
C1: 20.710 fF
Q-value: 51k

They've told me that they can replicate that crystal to the following specs .

Frequency: 14.915115 kHz / 1.OT (offset +343 ppm)
series resonance
Adjustment: +/-10 ppm at 25 C
ESR: 20 Ohms max.
C0: 4.25 - 5.25 pF
C1: 18.630 – 22.780 fF
Q-value: > 50k

The key parameter for tuning ability of the crystal is the dynamic capacitance C1. The higher C1 is, the easy is frequency tuning of the crystal

Anyway . Regarding the price . They've said "The price is about 10 EUR/pc. But we need to check if we have for the concrete frequencies the suitable blanks for crystal production. If not and if we will have to produce the blanks, the price will be a bit higher." I don't know about the postage .

At the moment I don't actually need any . I just sent them the sample to see if they could make them . Maybe someone on here needs one and wants to take the plunge and try one ? Their details are :

KRYSTALY, Hradec Kralove, a.s.
Josef Vozenilek
Okruzni 1144
500 03 Hradec Kralove
Czech Republic

[email protected]
http://www.krystaly.cz/

Make sure to give them the above specs , and tell Josef that it's for a CB radio . You can mention my name (Paul) if you want .

Anyway . That's about it . If anyone does buy one , then please post your feedback here so everyone else will know .

Cheers

S.
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by cb4ever104 »

Hi All .

Just FYI . Josef at KRYSTALY sent me a sample crystal . Unfortunately it will only pull about 3-3.5khz each way . I had initially sent him a sample of one that a pulled from a Ranger so that he could analyse it . The results of that are further up the page .

He supplied some additional information .

"If you need the biggest possible pulling, we can try, but you must take into account that the parameters below cannot be met (C1, C0, Q, R ...). Due to the MV201 varicap (2.3-14 pF), you would need a pulling of at least 30 ppm/pF. But this is almost physically impossible with quartz."

So , in a nutshell . The search for replacements continues . I've no idea how Uniden managed to produce quartz crystal with a +/-6khz swing and still maintain stability . Maybe someone else knows . I also tested a "McKnights" crystal that I had made in the mid 80s , and that's the same as well . About +/- 3-3.5khz .

S.
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Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by Otter »

Maybe send him a sample out of a Cobra? It can't be almost physically impossible with quartz if Uniden stuck 3 of them in every Mk.1 SS-360FM and C-148.
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Re: Does anyone know the load capacitance for older Uniden crystals

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Otter wrote: 03 Aug 2022, 17:43 Maybe send him a sample out of a Cobra? It can't be almost physically impossible with quartz if Uniden stuck 3 of them in every Mk.1 SS-360FM and C-148.
The Superstar crystal that I sent him had the same specs . It had about a +/- 6/7khz swing . The guy works with crystals , so I presume he knows what he's talking about .

I mean has anyone actually had a crystal made by another company in the last 40 years that actually swung by +/- 6khz ? I was pretty sure that my "McKnight's" one did , but I was wrong . Nick's continually looking for Uniden ones as well , so I presume he has the same issue .
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Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by Stronty »

Some of the crystals on that add show +/- 5 or more but not specified for the old 23Ch ones.
BE055CFE-CB82-426E-B165-C2AB3B0718E1.jpeg
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by cb4ever104 »

Stronty wrote: 07 Aug 2022, 22:45 Some of the crystals on that add show +/- 5 or more but not specified for the old 23Ch ones.
Where'd you find that ad Dougie . A mag from the 1930s ? :) I was half expecting to see some info on prohibition in it somewhere :)
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Paul aka "Sammy". (108) PY60 Old Paisley DX Group (RIP Rab Markie)
Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.
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Re: Does anyone know the load capacitance for older Uniden crystals

Post by Stronty »

cb4ever104 wrote: 08 Aug 2022, 09:37
Stronty wrote: 07 Aug 2022, 22:45 Some of the crystals on that add show +/- 5 or more but not specified for the old 23Ch ones.
Where'd you find that ad Dougie . A mag from the 1930s ? :) I was half expecting to see some info on prohibition in it somewhere :)
:D :D :D I'd say its as old as you or me :lol: :lol:
Lovely looking Crystals I thought.
Can't help but love an Adams.

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