Author Topic: 1W Portable Transmitter  (Read 3839 times)

ChrisH

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1W Portable Transmitter
« on: March 16, 2012, 06:16:52 am »
Hello,

Wondering if anyone can help me out.

ON the Printed Circuit Diagram T1 and T2 are in dotted lines.
(http://pira.cz/entx3dps.htm)

However, on the PCB there are no drill holes soooo.. does the dotted lines indicate that these need to be placed on the underside of the PCB , or are these parts not necessary --
Looking at the picture of a finished unit, these do not appear to be there either......

HELP! I am 99.99% finished, and I just simply have NO RF coming out --
(When I say 99.99% I am still waiting on the varicap diodes, but would expect to have a solid carrier up but I am not even getting that)

Any comments or suggestions on where to start looking would be great please.

Jan

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Re: 1W Portable Transmitter
« Reply #1 on: March 16, 2012, 07:59:55 am »
Do you really think the transmitter can work without transistors?
They are placed at the bottom side of course.

ChrisH

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Re: 1W Portable Transmitter
« Reply #2 on: March 17, 2012, 02:10:52 am »
Knew it would not work with out them.. I was just being a smart arse ;) -- but just there was no indication where they should go - apart from the dotted line :)

OK Then -- with this transmitter design, without the varicaps in place, as they are still on shipment to me...
Should I be getting a carrier, or do I need these in place to even generate that..

Jan

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Re: 1W Portable Transmitter
« Reply #3 on: March 17, 2012, 08:36:08 am »
You can't get carrier without varicaps. But you may temporarily place 33p capacitors instead of the varicaps, that should turn the carrier on (but frequency is unknown, probably somewhere in range 80 to 110 MHz, tunable by the oscillator coil)

ChrisH

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Re: 1W Portable Transmitter
« Reply #4 on: March 17, 2012, 09:53:46 am »
Thanks so much for that..

I will see if I have 33p Caps in the box of tricks, otherwise I will just wait.
Some of the components for that TX are not supplied in New Zealand..
I have got a Ham friend who suggested alternate parts, so it should be OK.. (he looked over the design) but we will see :)

Thanks again for the site, I think it's fantastic - down in NZ we have part of the FM broadcast spectrum dedicated to Low Power FM broadcasters - no license required, limited to 1watt (although lots of people go over), and its on a first come first served / if you get interference then there is no control - seems to work very well however..

Has got a heap of community stations working, which is a good thing :)

ChrisH

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Re: 1W Portable Transmitter
« Reply #5 on: March 18, 2012, 12:41:33 am »
Jan, I hope you can advise / help on this one :)

I have had to replace the following parts, due to not being able to source them from either Australia or New Zealand and shipping costs from the northern hemisphere is just too prohibitive (I got the SAA chip from the UK and that with postage alone cost me almost $50nzd which is a bit more over half of what I have spent on everything else on the board)

All these changes were suggested by a Ham operator friend of mine.

T2 and T3 I had to replace with BFR91
D1 and D2 I had to replace with BB149
T4 Replaced with MRF237

I believe these are the only things I needed to change or could not source easily, what could/would the impacts of these changes be...

I have been advised there should be minimal impact... I am still learning, so do not know.

PS: I did not have the 33p caps, so could not confirm a carrier, but I suspect the BB149's to turn up early this week.

Thanks again for the support :)