Yes I had the same assumption but wanted to make sure.

For those who are wondering? , this is the type of supply that? JB is considering -

?

It's a fairly basic design by Weber and the PCB is available from Far circuits in Chicago for not much money. However? Mr Weber does
not document his filter calculations at all for this design.

TEF

Thanks much for the answer.

Yeah, I finally got it working earlier today myself !

IMPORTANTLY : There is at least on step for (some/a-few/at-least-my-moto-phone) androids that I cannot find any mention of in this particular group...really.

AND: I found at least one "wrinkle" within ft8cn that is NOT mentioned in their manual...hi hi.

es vy 73 OM (especially for the reply) de "baab" w9ya

The main question Allison is do you agree with the splitting of the second feedback resistor as I did to do the maths.? ?

Indeed for the? AD 8009 the datasheet? recommends? about a? 50R resistor in the output drive line to? reduce chance of instability in the amplifier.?

THe datasheet is a bit coy on the conditions that lead to such instability.? Yes I refer to the? 8009.? ?IN the case in question? the OP resistors have been put in? parallel to? ensure that can dissipate? up to? 0.5? W? that is what makes me suspect that those reisistors are there not only for stability reasons but also as? a form of power dump if the? RHS transformer is left unterminated.?

Are there any? dual? Video amps of this type (two to a package )? that you know of? which? can do a similar duty at HF? to? 50 Mhz drive? I get the impression that this OPA is? pretty much unique in this regard.?

I will include a? photo of a commercial application that uses this type of? Tx chip but I have some considerable reservations about what is shown.? Specifically there appear to be be cappies in the lines from the? driver transformer to the OPA . This would mean that? ?there is no way that the signal bias can get to the op amp.. Clearly there could be components under the PCb but given there is a heat sink there , that seems unlikely.? The alternate is that the UKR Mafr has published a false photo and what is supplied does work and is subtly? different from the photo. This design has zero filtering post the? RF power amp mosfets.? ?I include it mainly because it shows how the transformers? were implemented as hand wound designs and not? commericial designs as per schematic supplied (or a completely different application).

Regards,? TEF

?

?

Thanks Dean !
OK, it sounds like a linear supply is the way to go.? I have the parts to build one with the possible exception of high capacitance filter caps.? ?How large should the filter caps be for optimum performance?
Jim

Hi Baab,

Firmware 017 works fine for me on FT8CN 0.92.
I'm using it right now and it has transmitted just fine many times in a row.
I don't recall Hans mentioning fixing anything related to this in the release notes, though.

73, Mike KK7ER

开云体育

how many amps should the diode be able to handle? My regulated power supply shows about 0,8A during transmit on 40m. Is a diode with 1A rating sufficient?
73 OE6HKE

There are some good quiet switchers out there, but there are a lot of noisy ones as well.? You'll never go wrong with a linear supply.? They are inherently quiet.? You won't need to mess with any kind of isolation or noise choking with a linear supply.? But linear supplies are bigger and heavier than switchers.? If that's not a concern, go with a linear supply.? Whatever you wind up using, make sure it is regulated and that the output voltage is within the radio's input voltage limits (refer to your radio manual for the specs).?

Here's a tip from and for the frugal ham.? For powering QRP rigs, I've often used old CB-type regulated supplies.? You can buy them cheap at swap meets and garage sales.? On more than one occasion, I've also salvaged the complete regulated power supply sections out of junked solid-state base station CB radios and packaged them up in suitable chassis boxes with a fuse, suitable output connections, an LED pilot lamp, and a 3-wire power cord.? In fact, I have one sitting over on the other side of the shack right now which I salvaged from a junked Royce base station.? Cost me basically nothing and was a fun project.? Most CB power supplies are good for at least 2 amps, which is more than enough to run a typical QRP rig.?
--
73/72,
Dean K5DH

Doug, those pads are reserved for the TCXO board. The fact that the noise decreases when you touch them is an indication of something. Just not sure what. It could indicate a bad solder joint on a component's gound side. I have a similar issue that I traced to an antenna cable that was leaking RF, but the RF can get in in other ways, like the key, audio, or even power wires.?
--
73, Dan - W2DLC

开云体育

开云体育

Hi Steve - it was just powered from the PC via the USB port.

Peter

Doug, do you notice any increase in volume of the noise when you touch the case or other object, like the key, that's attached to the QCX??
--
73, Dan - W2DLC

Burt: I had the same problem as yourself. Check the tab soldering on the large MOSFET Q507. That is a pre-installed unit and on my board the tab was sitting above the circuit board by about 1/2mm and had not been properly soldered at the factory. When I soldered that on properly it solved my no power out on Tx.

Hey Dave,

I just received my 2x QMX this AM, and had the same question. ?I assume we would use Rev 2 instructions but I’m waiting to see if someone answers here.

Todd K4MSW