From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, February 04, 2018 3:22 PM
To: [email protected]
Subject: [SPAM] Re: [BITX20] Higher voltage for Bitx40 Final

?

11.5v should be fine, make sure it is still 11.5 when PTT is pressed.
Quiescent IRF510 drain current changing somewhat as they get warm is normal

The drop from 6w to 4w when V+ to the IRF510's is bumped from 12v to 24v is very weird.
Have you tried simply switching the IRF510 V+ between the two with exactly the same setup, same instrumentation?
Hate to say it, but my first guess would be pilot error.

On Sun, Feb 4, 2018 at 01:10 pm, Vic WA4THR wrote:

Just finished building my BitX40 after playing with the circuit for a few weeks. Early tests on mine suggested that using the small booster I have and raising the PA voltage from around 14 to 24 did seem to increase the power by the square of the voltage ratio, so matching these experiences. Admittedly, I was trying to read this on a 450w dummy load meter, and yelling into the mic, s not very accurate. So this past weekend I did get a QRP wattmeter that could read 30w as full scale and get a better idea of how much I am increasing.

However, now when I apply 24v to the final the power output actually drops from 6w to 4w! The only significant cuircuit difference is that I am now running the other 2 power connections (main board and Raduino) through a 7812 regulator, and since it is not getting quite enough to regulate to 12v, it is delivering about 11.5v to those boards, which I assumed was just a bit safer. The voltage booster is not dropping voltage under load, so I am befuddled as to why the power actually drops when I apply the higher voltage. I did recheck the PA bias and raised it up closer to 100ma, but I notice it slowly increases from wherever it is set if I continue to hold the PTT. Any ideas? Perhaps I should short the input to the output of the little 7812 to see if that actually had an effect.

Well, it's nice. But you still have to design the amp.

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I really like that!?? If you fold the RD16 over you could use a heat sink out the back…

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Here is how I made the socket and mounted the RDD16

Note the RDD is reversed and? then the gate is actually soldered to the IRF gate line which goes behind the FET.
Now I can use either of them..

You will need to think of a heat sink plate that fits this way!



At 01/02/2018, you wrote:

Why replace everything??? You can probably put it in place of the 510 (making sure it is pinned correctly, of course).? ?
I am waiting on a pair, myself, that I will be stuffing into the ubitx.?? ? I want to even out the power output.?? I will also try a resistor/capacitor in parallel, in series with the gate, to try and even out the frequency response.?? I am thinking 4.7 ohm & 4700pf.?? I will also try 6.8 ohm & 4700pf.?? Depends on how flat I can get the output.

Marco - KG5PRT?

On Jan 31, 2018 10:12 PM, "James Lawrie" <lawriejk@...> wrote:

Hello,

My shipment of replacement RF Mosfets have arrived and I want to replace the on board PASection with one based on the RD16HHF1. It will be a separate small PCB based on the reference design shown in the data sheet. I need help from the professionals here as to where to attach the new PA board.

I know it would be somewhere after the 2N2219A driver, and I want to remove all bypassed SMTs and or other parts from the Bitx board in that area. If you have a pretty good idea could you please let me know, and possibly a drawing if you could. This should keep me busy and off the forum for a while.

I got mine from RF Parts in 2 days around $5 each.

I also got some of the RD16HVF1's (good through 2M) as well. They were
only a tiny bit more than the 30MHz HF parts (less than $6 as I recall).

I won't be trying these until I've had a chance to check out the driver
stages 3.5-30 MHz, later this month when I return from a couple of trips.

Dave WI6R

On Sun, Feb 4, 2018 at 3:32 PM, Nick VK4PLN <nickpullen@...> wrote:

HI Group.
I have been searching and reading topics with regards to using the
*RD16HHF1* in the uBITX
*.*So far I have only been able to find suggesstions, but no actual
implementations...

I was testing my uBITX and getting 9w on 40m but only 1W at 10m...
Would love to have 5w + higher up.

Can anyone provide more info/help?

Thanks.
73, Nick VK4PLN