ZTX327 transistor

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Re: ZTX327 transistor

Post by Admin on Sat Dec 01, 2012 4:59 pm

I seem to recal doing an article on Zeners as capacitance diodes. I will have a look over the weekend,. If it is not on my homepage then it was written for a magazine.

BR Harry
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Re: ZTX327 transistor

Post by Willem on Fri Nov 30, 2012 12:27 pm

Zeners I can get my hands on - and they will be much much cheaper. I'll have a look at the FM techniques

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Re: ZTX327 transistor

Post by Admin on Fri Nov 30, 2012 11:06 am

Varicaps! Try Zener diodes, they are wonderful. They are as good as varicaps, but you have to be careful of the zener avalanch point and the varicap DC bias voltage (plus modulation).

If you look on my homepages you will see a page about FM techniques using varicaps, zeners, LEDs and even switching diodes to switch in capacitance for a part of the RF cycle.

Switching diodes can ive you a 100:1 capacitance ratio, or a frequency ratio of 10:1, which is three times better than old-fashioned air-spaced vapacitors.

Best regards from Harry - SM0VPO
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Re: ZTX327 transistor

Post by Willem on Thu Nov 29, 2012 5:07 am

Thank you for your advice Harry

Glad to hear it's not only us in South Africa who struggle to find components like varicaps

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Re: ZTX327 transistor

Post by Admin on Wed Nov 28, 2012 10:54 am

Ok, I am so glad you have it under control. Here in Sweden we sometimes have a devil of a job getting hold of certain kinds of components. Varicaps, for example.

The last time I tried to get varicaps I had to buy 500 pieces and there was only the one variant available. Zener diodes are easy to get and are also good varicaps.

But as regards the ZTX, PYE telecom in Cambridge used to use several WeIrD transistor types, but were in fact conventional transistors bought "on the cheap". For example CIL108 and ZTX108 (Tonelock boards) which were both BC108. And 2N4286 / 2N4289 which were BC547 / BC557 in a different miniature package (PF70 pocketfone series).

But if I can help further then do not hesitate to contact me.



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Re: ZTX327 transistor

Post by Willem on Tue Nov 27, 2012 6:22 am

Thanks Harry for the info

Its FM broadcast range, about 90 MHz, as I understand it a 10MHz crystal running in third overtone mode

Thank you for the kind offer, but I luckily have lots of BC547's

Popular transistors are easy to find here (I'm in South Africa). Ferrite slugs, tunable coils - that is another matter Smile

I found another crystal controlled FM circuit that does not use the ZTE327 - I just wanted to build a circuit of this kind in addition to all the normal VCO circuits I've done so far

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Re: ZTX327 transistor

Post by Admin on Mon Nov 26, 2012 9:31 pm

What is the operating frequency of the transmitter?

The ZTXnnn devices often are identical (copies of) BCnnn series devices. If you look at my secret server www.sm0vpo.com:800/_pdf you will find the ZTX327.pdf in the root directory and if you look in the BC directory you will find 100s of BC files you can compare with. Both the ZTX327 and BC327 have an ft of 100MHz.

But the ZTX is just a bipolar device so you should be able to substitute it for most other bipolar devices. Most audio and GP devices (eg. BC108 and BC547) are all good at that sort of frequency, and 400mW is a very modest power.

Suggestion: suck-it-and-see. If you need any BC547's then I can send you them, as they are about the cheapest you can buy and they are excellent for up to about 120MHz. "Common as muck" as my dear old mum would say.

Best regards from Harry - SM0VPO
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ZTX327 transistor

Post by Willem on Mon Nov 26, 2012 5:04 pm

Hi,

I am looking for the obsolete ZTX327 transistor. This is for a crystal controlled FM transmitter circuit I want to build. I can't find any NTE equivalent for this - anyone still have some of these lying around?

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