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Thank you Don,

will watch that, your note is appreciated.

73! George

VE7WQ

Wednesday, February 21, 2018, you wrote:

DCvGI> Yes, what he (Thomas) said! But keep them close, no big runs. Unless you

DCvGI> are going to feed full CW into it for a long time, go for less power

DCvGI> dissipation.5 watts will do for 10 PEP SSB continuous. Even less needed

DCvGI> for shorter times. Best of all, experiment!

DCvGI> And thank you VERY much for the kind words! Best 73, Don

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Thank you Thomas,

just to be sure,?

using 5 pieces a 250 Ohm 2W composite resistors in parallell,

will make a 50 Ohm 10W dummy load. Right?

73! George

VE7WQ

Wednesday, February 21, 2018, you wrote:

TSvGI> Use a multiple of 50 with and additive amount of watts. Put them in

TSvGI> parallel and you'll have 50 ohms at 10 watts.

TSvGI> Example: 5 times 50 = 250 ohms each, 5 times 2 watts each equals 10

TSvGI> watts.Example: 20 times 50 = 1000 ohms, 20 times 1/2 watt each equals 10 watts.

TSvGI> Kirchoff's Law is your friend. Also don't use wire wound resistors. They're inductive.?

Hi Nik,
I looked on eBay, and couldn't find your replacement RaduinoI2C. I would like to order one quickly as I toasted mine for my UBitx. :-(?

When could I get one?

Thank you for the excellent work.?

73, Chuck Kelly W9MDO
Noblesville, IN 46060 USA

Sounds good, Gary!? I just need to carve out some free time soon to get er built.? Once I do, it would be great to set up a sched some evening on 80. Will check with ya then. Thanks!
Tom
AB7WT

--
Best 73
KD8CEC / Ph.D ian lee
kd8cec@...
(my blog)

Yes, what he (Thomas) said! But keep them close, no big runs. Unless you are going to feed full CW into it for a long time, go for less power dissipation.5 watts will do for 10 PEP SSB continuous. Even less needed for shorter times. Best of all, experiment!
And thank you VERY much for the kind words! Best 73, Don

That's great Dennis! Thanks for the info.? I'm your neighbor up in Horseheads.? I ordered mine on December 29th, so let's see when I get the notice.
-Daniel, W2DLC

Thank you very much.

I have ordered the parts and will build this to add to my ubitx.

I think this will supply power to the PA power wire on the power connector.? Is this correct?

Do I need to do anything with RV1?

I will have my Watt/SWR meter on the ubitx so I will know what my actual power output is.

Would you be able to post an PDF or Jpeg of your print?? The print on this blog is not very clear.

I very much appreciate your help.

73, W9KJO, Walter

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Thank you Don,

your blog is a treasure trove, you are a fine artist as well.

The last time I saw an illustration like this, was in a 19th century sciense book:

Question: how can I make up a 50 Ohm 10W dummy load,?

for the B40 out of easily available resistors??

The store don't have 50 Ohm 10W or 2x 100 Ohm 5W resistors here.

73! George

VE7WQ

Wednesday, February 21, 2018, you wrote:

DCvGI> More to come.

DCvGI> Have fun!

DCvGI> -Don, ND6T

BTW, could we keep this thread focused on using the RD16HHF1 discussion and move the SMD/SMT discussion to a new thread?

Thanks for the great measurements on the pre-drivers, Glenn.? Makes it clear the IRF510s aren't the only problem, which corroborates Jerry's excellent LTSpice work.

Allison, you are quite correct.? RD16HHF1 vs IRF510 is more a personal preference for me; both will certainly work well with the right changes.??I agree that redesigning the pre-drivers and finals is the best way to go to get flatter gain across the bands whether using the RD16HHF1 or the IRF510.? Personally, I'm OK with replacing everything from C80 to KT1 pin12 in my uBitX, but I understand that others may want a simpler solution.? That's the beauty of having an open design you can tinker with.? What changes would you recommend to the transformers, and what transistor would you recommend for the pre-drivers to get flatter gain across the 1.8Mhz - 50MHz range?

Thanks,

Carl, K0MWC

What about replacing RV1 with an AD5246, and an SWR bridge to monitor output power and then a PID loop to adjust drive level to attain desired output...

Allison, thanks for the insights.
Much appreciated.

I noticed that the push-pull IRF510's performed much better in simulation using the WA2EBY
output transformer scheme? than with the stock uBitx output transformer.?
Is that the "simplified transformers" you refer to?
Or do you suspect the uBitx has significant trouble in how it drives the IRF510 gates?

My simulation showed that both the WA2EBY and uBitx loaded down the 4x2n3904 driver
with about 12 ohms at 30mhz (still in phase on the WA2EBY, as I vaguely recall).
Rather surprising, but perhaps that was due in part to the simulation using worst case IRF510 spec's?

Any suggestions on how best to pick up gain in the driver and predriver,?
perhaps swap in a different transistor?
We've got lots of uBitx's out in the wild now, and would be nice to have an easy hack.

Jerry, KE7ER

SUBTRACT A FEW PARTS AND A POT AND IT IS CONSTANTLY VARIABLE ADD ASC712 TO MONITOR CURRENT AND A VOLTAGE DIVIDER TO SEE WHATs GOING WITH REALTIME DETAIL.
DAVE
Ihate caps lock

Doesn't matter if psu connects to ammeter black or red,
will likely read with a minus sign if you put the black ammeter probe on the PSU.

I suggest you measure PA current separately, since I think you already have a handle on the main board supply current..
Should see 0 amps with both RV2 and RV3 fully clockwise (minimum) with ptt pressed.
Then you slowly slowly turn RV2 up for 100ma, and then RV3 up for an additional 100ma.

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Thank you Eric,

I was soooo affraid to tackle any smd involved task until now,

but you gave me the needed insite and enouragement,?

I feel, I could do it now.

73! George

VE7WQ

Wednesday, February 21, 2018, you wrote among other things:

EK> Sometimes I'll tape a hunk of fish paper over a thru-hole I?

EK> think might not like the heat. Or I might cover a previous SMT part that?

EK> might come unsoldered and get misaligned or blown away.

EK> Eric KE6US

There seems to be a belief that the IRF5xx parts have no capability at VHF...

I have an amp using 8 of them at 32V that puts out a mere 210W at 50mhz.? All of the parts are
IRF510s in a 4x4 push pull arrangement!? The amps gain over all is about 13db.?

I have also built the WA2eby push-pull HF amp and that design with 2w in gives me 55W at 40M
and 37W at 29mhz, that with a 28V supply.? ?Also IRF510s so the part has capability though
generally if performs better at 24V.

THe bias on the IRF510 is often lower than optimum, Both amps (and other HF/6M projects)
run far more bias current that specified as it produced more power.

The problem is the amplifier has matching issues from simplified transformers.? Additionally?
at 30mhz the AC? gain of the driver and predriver transistors (2n3904) is about 10 as compared
to an AC gain of 20 at 14mhz. So you seeing two problem one of driver that diminishes with
frequency and matching that is less than optimum with increasing frequency.?

I've also built amps around the RD16HHF part and at 13V its good but it requires different
components around it to get the power out they can deliver.? For a push pull pair with adequate
drive 20W is about it.

Before I'd go for changing parts I'd insure the driver and predriver are producing enough power.
It is also possible that the particular parts are on the low sid eof spec but the design is robust enough
to absorb that.

Another thing to insure is that your DC [pwer getting to the final is really 12-14V and not suffering
excessive voltage drop due to wiring? or worse the power source fading at higher currents.

So dropping in RD16HHF1 in without changes will likely not improve matters much and it may
lead to instability.? ?But if you have a pair you can try.?

I'd expect more like 4W or more so something is not right.


Allison/kb1gmx

I finally got my uBitx calibrated to my satisfaction but I still think there is room for some improvement there. Now waiting for my case to arrive and I can finish it up. So far very happy with it.

Joel
N6ALT