Thanks all for your answers, although not necessarily fully converging.

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From what I understand, Jay and Roger have used it with no issues at all. But all the rest see some flaws in the use of iFTxx. Actually it is a pity there is no good approach to this as it apparently exists with Android phones.

I understand that a lightning to USB C connector should work fine providing iFTxx behaves…?

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TNX,

?

Joan

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Allison? re? - substitutes for the OPA2674.? and other important matters?

Interestingly Mouser lists? most video amps under? High speed operational amp category.? . If you go to? Video amplifiers you find it very bare.

There are now only two major manufacturers being? AD and? Texas? There are about three other minor manufacturers?

These latter have? Iout max figures of down around 110 mA typically so they are not much chop for the application.

OPA2674. - there is no substitute from? AD since the OPA can source up to 500mA? RF energy? at the output?
The nearest two channel device I can find from AD is the? AD? 8008? which has a 180 mA drive capacity. Threshold frequency might be slightly higher than Texas.

The highest? Iout I can find from an AD device is 175mA from the AD 8009. This is a single channel device.? Frequency specs are somewhat better than the? OPA2674

All three device have? Vmax of? 12 V when operated in single supply mode and generally have? a? +/-5V swing at maximum drive.

Ergo - designing in the? OPA into any bit of? RF? ?kit is fraught with danger commercially? as there is no compatible/comparable substitute. .
=================

I'll leave my critique of? H Granberg's best efforts in terms of what he left out and what he covered by ex Cathedra statements for another time? ?viz.? Motorola application notes.? I have a full bound set on rice paper that I managed to pick up for cheap a long time back.? Full as in Motorola said? they were the most important ones !! Not just Granberg -all sorts of other clowns, many oft them seemingly much more talented.? ?I will stick that critique nder the? ?RF Preamp header for those who may be interested.?

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Hello Hans,

Could you do a favor and share a order id for recently sent parcel?

I understood the huge backlog you having right now and thus I am sorry for my impatient =)

Thanks a lot, Yury

Allison? - comment on LT 1254 noted.

I also have some things to say about the Motorola high power application notes and they aren't all good.??

I'll write the? out in due course and perhaps save some people from a? bit of heart ache.?

You might note that I have come to the conclusion that? the resistors for? the voltage divider and? loading resistor for the driver might?
be in H configuration with the CT take to ground via an RF bypass.? I cover that with a separate note. That would assume that? some of those?
resistors are under-board? mounted.?

?

TEF

Doug, there might be? an H topology arrangement in place with 2x 1 K resistors forming the voltage splitter and then two resistors under the PCB forming the other part of? the H which provides a? say 200 R termination to the transformer and at the same time places? 6V on both legs of the driver copper? post the coupling capacitors. This assumes components and Vias that I cannot see but makes some sense.? Why are the coupl capacitors there at all ? Perhaps they are there to attempt to null out parasitic capacitance? from the RF input transformer.?

TEF

It should be mentioned that IFTX takes considerable liberties with the WSJT-X software concept. I did make some contacts with it, but it needs some changes to be truly useful.

Operational: The software will ONLY let you call stations that are literally calling CQ. You cannot reply to stations sending the 73 period who often get another call immediately from others and may not literally call CQ any time soon. And if you reply to a CQ and the station comes back to someone else, rather than continuing to call (remember, you are probably not on his frequency) you get a big, obnoxious red banner that says “LOST” and you will have to wait for that station to call CQ again before you can call again. WSJT allows you to initiate a call to anyone you can receive at any time, which is how FT8 should work.

Technical: In WSJT there is a split mode that shifts your center VFO frequency if you are calling below 1500 Hz. You keep your relative position in the 3kHz passband, but the radio changes TX center frequency. Why? Because the idea is to keep harmonics of your audio frequency outside the 3kHz passband of the FT8 segment where they will be suppressed rather than transmitted over the air. Example: if you are transmitting on 1600 kHz, the second harmonic would be 3200 kHz, safely suppressed. But if you are on 800 Hz, the second (1600 kHz) and third harmonic (2400 kHz) are NOT suppressed and are transmitted (at somewhat lower power), but are still transmitted over the air. WSJT has a mode called “fake it” that provides this if you don’t have rig control to move the VFO on transmit. I would definitely operate using TX frequency above 1500 kHz with this software. To be a good neighbor to your fellow hams…

While it “works” and is cheap, IFTX is not really ready for prime time, IMHO.

Which solder joints did you reflow to address the sidetone issue?

I’m still having a strong band-dependent ‘knock’ at the end of each character. Wondering if a bad solder joint could be a cause??

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