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Bill, We can make a power sense and feed the DC say 0-5V to an analog pin of the raduino and depending on the power level change the drive current of the VFO, I think we can do a crude(ish) power

Well this is gonna be important when it comes to activating the tuner I’m designing. You won’t want to tune under full power so this turns out to be a great way to decrease the power for

It’s not the bias… it’s the drive level. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton,

How about using an I2C DAC, and then letting?the Raduino setting the bias based on what band and what output power is desired?? -- Karl Heinz - K5KHK

It is interesting that Chris M0NKA does this with his mcHF SDR kit. It has a Max Pwr setting that is similar to uBITX on 80M (12W) but they have a calibrate setting for each band at 5W, and then can

Trouble is… it occurs at every stage so where do you put the gain equalization? I made a couple of calculations and then swept the circuit and noticed that the PA ran away at 21 MHz so did not

?Dr. Schmidt -- no way to put some feedback into the circuit in some manner to stabilize the gain? 1000 pf across the 22 ohm emitter resistors to have a 3db break at 7

I had a couple of hours of spare time today so I started off my measuring the gain of the pre-drivers in the uBITx.. and sure enough, there is a lot of variation from 1.8-54 MHz (where I want mine to

Although not Allard's sketch, this has worked for me: http://www.nd6t.com/bitx/documentation/encoder.htm I am also using polling (without the interrupts) on a replacement sketch for the uBITX although

Yes that makes sense… The current through a capacitor is given by I=C*dV/dt so the average current over time is I=C*int[dV/dt]/t… For your example: let’s use a 100pf capacitor in an 30 MHz

This Vishay datasheet is fairly typical. ? ??( https://www.mouser.com/ds/2/427/vjcommercialseries-222796.pdf ) https://www.mouser.com/ds/2/427/vjcommercialseries-222796.pdf (

That's great!! Sent from my Verizon 4G LTE Droid

Great work. Looks like the heat sinks are direct connect like the originals ? Sorry if you've already mentioned this. I'm going for mica insulated types because then I can use a huge heat sink

The mistake that most people make in RF circuits is not paying attention to the current rating of the part. Make sure your capacitor can handle the current for its service. The voltage, size, and

Silver mica caps work fine, were state of the art when most hams learned how to build LPF's and such. But that was 50 years ago. Surface mount ceramic caps of type np0 or c0g are far cheaper and just

Ceramic capacitors would work fine. Just make sure it is rated for the voltage that will be present. I use 500 or 1KV caps, personally. Over kill, yes, but I have not had one fail yet. Just my

John - I will ask Erhard DF3FY whether this was an error.? I suspect it was. 73 Mike -- Mike Woods mhwoods@...

Here's a fun case I saw in Harbor Freight today. Very handy if you want to keep your uBITX "safe" or if you just want to hide the fact that you are a uBITX

I'm learning here. I understand that a mica capacitor is the best type to use with RF from reading and they are the most stable. What would the impact be of using a polystyrene or ceramic capacitor

Last Saturday went to the Orlando, Fl Hamfest looking for a uBitx case.? Despite all the tailgaters/vendors none seem to have suitable cases. (Did snag an almost new Experimental Methods in RF Design