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Re: Minimum spacings between buses

PostPosted: Fri May 16, 2014 5:38 pm
by n1ps
Is that the fet input by Floyd WVL? Looks like it is. Curious why you went with this circuit.

Peter

Re: Minimum spacings between buses

PostPosted: Fri May 16, 2014 6:10 pm
by W1AC
That's a very nice looking rig! I hope I can do as well!

Please tell me what the circled devices are in your picture. TIA.

Bill, W1AC

Image

Re: Minimum spacings between buses

PostPosted: Fri May 16, 2014 6:21 pm
by W1AC
Gilly wrote:The picture here is of my 40M Sinewave drive TX....a little baby compared to yours but has been a very reliable Transmitter to this day really....


Wayne,

I forgot to mention: although the original RF deck was set up for sine-wave input, I'm going to use IXDC614 drivers instead, and (if Steve still has one) a phase-splitter/driver board. If not, I'll use the existing input toroids and split the phases that way. I'm not going to use a VFO, however, since the FT-890 will serve as my receiver, and it'll do fine as a driver too.

I figure about a 9 db pad will give me enough range in the power adjustment that I won't risk blowing up the driver chips. Has anyone had experience with using typical 100-watt-output transceivers as drivers?

Bill

Re: Minimum spacings between buses

PostPosted: Fri May 16, 2014 8:44 pm
by kf1z
IXDD614 are readily available at Digikey... Mouser etc.

I have a couple tubes of them here......


You need Steve's RF Sine wave to 2 phase digital board and 1 watt from your transceiver.

Ask him if he has any boards....


Sure... you can use a transformer and use the positive RF to drive one phase, and the negative RF to drive the other phase.....

But that convertor board really works well, and allows you to adjust the duty cycle.....

Re: Minimum spacings between buses

PostPosted: Sat May 17, 2014 2:34 am
by Gilly
Hi Peter

Yes the design is from Floyd .... its on a post sometime ago now but cannot find it actually...
Although I feel the input circuit is varied from his .. just cannot remember ....
I didn't like using FB43-1020 for the input transformers as they are so big and looked a little silly.....
The big thing I found was that the windings had to be really tight otherwise the drive levels on the gates varied ...so I just experimented and found these little cores at the local Electronic shop...
They work perfectly and due to their size can be mounted very close the the gates of the FETs....Quite important since this TX is for use on 40M...
The turns ratio is 3:1 ......
There size does make things look neater....

Hi Bill

Those little square things are capacitors to ground and the diodes provide a little bias so that less drive is required....
The FETs are IRF840
As is appox 12 Watts sinewave is required for 24 volts peak to peak..
The cores are only about 50 cents each too....
To be honest the cores aren't too critical for the input circuit....

I found this photo...when experimenting....they worked OK too........

Image





Wayne

Re: Minimum spacings between buses

PostPosted: Sat May 17, 2014 9:37 am
by W1AC
Gilly wrote:
Those little square things are capacitors to ground and the diodes provide a little bias so that less drive is required....
The FETs are IRF840

As is appox 12 Watts sinewave is required for 24 volts peak to peak..
The cores are only about 50 cents each too....

To be honest the cores aren't too critical for the input circuit....


Thanks for the info: that's great to know. I assume the circuit would work on 80 meters as well.

I was told "sine wave" input has stability issues, but seeing that others have done it makes me want to power up the deck I have and see what happens - an urge I should probably suppress. My deck has 5 11N90's per bank, and a tuned input circuit, but I could easily take out the tuning components and feed it directly: I've got up to 100 watts to play with, so I can afford a lot of inefficiency.

Hmmm.

I'll fight the urge while I wait to hear about the input boards.

Bill

Re: Minimum spacings between buses

PostPosted: Sat May 17, 2014 6:58 pm
by Gilly
Hi Bill

I couldn't resist the temptation to try it as is.....it will probably go.....
Using a dummy load maybe first to see how much power your RIG puts out in the low power settings.....5 Watts should be safe using 10 FETs.....
Play around with the power control getting used to the feel of things...

When all thats good place an SWR meter in line and CRO probes on the 2 banks ( Gates )...
Apply a little power ...adjust that input circuitry for lowest SWR reading and then increase the power until you reach 24 volts peak to peak...
Check that anything seems OK and nothing getting hot.......

If alls good then on to the more fun stage of applying Drain voltage etc:

Could be interesting !!!

BUT maybe best to wait until Bruce gets those parts.....



Wayne

Re: Minimum spacings between buses

PostPosted: Wed May 28, 2014 7:35 am
by Diego-CX4DI
dear Wayne,

what mosfet are you using in your "little baby"???

regards,
diego
cx4di

Re: Minimum spacings between buses

PostPosted: Wed May 28, 2014 5:30 pm
by Gilly
Hi Diego

They are IRF840 FETs........

Quite good really with only 1200pF gate capacitance and 600 volts across the D/ S.....
Although probably best to limit the carrier voltage to a maximum of 35 volts....
I work on 30Watts per FET so the TX seems quite happy totalling 120Watts output....
The Drain resistance is only average so best to use high voltage less current etc:

Although I don't use them anymore now.....


Wayne