Ok.???? Guess I am a bit long in the too but i grew up with 4 band coding......the last being tolerance.? These resistors are five bands hence the error on my part.? Also the first two bands looked like brown but under a magnifying glass they are not they are red.? The value of the two resistors is 2.2 kohms.? Tested on an old analog Heathkit vom and a modern digital vom both agree.? So I have to assume they are meant to be used with the paddle although they are not 10 kohms.? Thanks for all the comments.? Cheers Jeff

You means spectral purity around the fundamental or the harmonics? Listening to a few hams on VHF, having an SDR receiver, my impression is that around the fundamental they were not very clean. I have to say that many that have that rig have done a simple mod around the mic input to have plenty of punch. Also that radio have also a arsenal of possible equalization. Do the users of these NASA rigs always check for their spectral purity or maybe they take for granted they are clean whatever the mods and equalization?

Hiro,

I would think with 3 or 4 Nano's you would have one without the objectionable tone.
The processor clock frequency is determined by a 16mhz ceramic resonator
which can be off by perhaps plus or minus 100khz.
Since it is probably the 3'rd harmonic of the 16mhz resonator creating the tone,
if it is off by 10khz, then the tone would be 3*10khz = 30khz.

Buy Nano's that do not have the pins soldered in such as this:
? ??
To plug the Nano into the Raduino's socket on the v4 uBitx, the pins must be soldered?
into the top side of the Nano, not the bottom side where the pins usually are.

Jerry

Hi,

I wan't to build a filter I can use with the uBITX. However, I don't want to build a filter that is strictly tied to the uBITX.?

So I'm building a standalone Low Pass Filter box that will work as an add on filter for the uBITX as well as become a general purpose piece of Ham equipment I can use over and over for other needs.

It uses an Arduino to measure the frequency you're transmitting on and select any individual or combination of filters you like. The proposed design uses a set of filters and a relay switch board; such as to ones by QRP Labs. But, the Sketch code should be easy enough to modify for whatever you like.

The controller can show he selected filter with LEDs or with an optional LCD display, and show the transmit frequency as well.

I'll need to order parts and build mine to finalize the design. However, I built and tested a prototype with a signal generator.?

I'm releasing the preliminary design to everyone now because it is complete enough for people to try out on their own filter designs. It makes using outboard filters really easy, and I think people will like it. I welcome feedback on improvements people make while building their own "Auto Filters" with the controller.

The code for the controller is here:?


----


Tom, wb6b

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I barely know how to do this, but I uploaded the design document, and the zipped gerber files (which pcbway.com was happy with) to this github directory:

?

Here's an old thread about audio tones in the receiver,
possibly due to beat notes between harmonics of the 12mhz bfo and the 16mhz Nano processor clock.
? ? /g/BITX20/message/54576
Easiest solution if you have a v4 uBitx with the socketed Nano:? replace the Nano

Jerry

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?Hi Jim,? ?Allison already did that for a motley crew of raidos, including a Heathkit HW-100 and they all were good to go except I think one reallly clunky design.? ?The general thing was that most radios are pretty well engineered.? ?

Gordon

Hey, I'm just curious how all the other portable radio compare....
Are they :"clean"? Specs can be that "special" radio, just for testing.
Your mileage may vary,
Jim W0CHL

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I bit the bullet and submitted files to pcbway, for 10 printed circuit boards for external relays.?

While I was at it, I threw on a small bit of circuitry to give me a 3 terminal regulator and a backwards diode etc so if? I need to regulate a voltage for the receiver downwards, i can do that.??

printed circuit boards are amazing.? ? ?My local ARES group absolutely reduced their building time by at least 80% when I switched to giving them printed circuit boards that just have to be populated, rather than piont to point wiring.? ?My own building time went down similarly though i was much faster than beginners of course.

My plans are to get them this optional external relay set,? and also an optional daughter board with the popfix for those with v3 boards and maybe the AGC also..... but all that is in the future.? ?FIRST just to help them learn how to wire up the ubitx, with a bit of resistance in the speaker line if they have the IC amplifier.? ???? One step at a time!

I just got PAT working for the very first time on WINMOR....amazing....will give us winlink access from raspberries to uBitx transceivers.? ??

Gordon

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?Keyes

(1) OK, good that you have a ground plane image that handles the ground connections to the relays.

(2) you might consider taking some action to avoid blow-around via the coils.....Allison has mentioned this several times and the standard she mentioned was inductors in the relay lines.? ?You might (I don't know if this is already done) be sure the relay lines (both of them) are bypassed to ground with some capacitors.? ?That might be enough --- i just don't know.? Not an expert here and don't have any numbers to model this with in my head.?

I chose to throw in some 100 uH inductors which supply a few hundreds of ohms at the lowest frequency if I calculated correctly.? ??

Even a set of pads so some one could put in a small coil of wire around a tack nail might be good.? ?

Cheers,

gordon

all due respect Allison Bitx20A is a dual IRF510/A? class B? design with substantial drive frm small signal drivers . I is suppose to produce 12W clean if well set up. Basically the parameters are similar to a uBitX but the output drive transformer is a bit different from most other designs.? It has the indications of a lot of? dev work done on it and it is supposed to be clean on OP? if built and biased as per directions.

Though it took a little longer time, finally my uBitX seems to be working very well now, for which thank you for advices here so far.

Then, another question to ask you who experienced the same issue.

I hear high frequency noise behind the band noise that my iPhone freq meter says it’s about 2,700Hz. (I’m not sure if this app is reliable or not)

My uBitX is not in a metal case, yet. And I use a small powered speaker.

Maybe it comes from Raduino or main board of uBitX, or possibly the 12v power supply.

Since I’m planning to bring my uBitX to a local lab in order to measure its spurious emission this coming Wed, I’d like not to mod much things on hardware coz it may possibly bring another trouble to me.

I just hope that some capacitor in the line of speaker or some small mod can solve this issue at this moment.

Looking forward to your advice.

Thanks!

// hiro, JJ1FXF

On Sun, Aug 12, 2018 at 09:14 PM, Gordon Gibby wrote:

?Hi Keyes --- I wasn't following so not sure if this is for OUTPUT or as a preselector for the PA stage.? ?I don't know exactly how to read your PCB's but a few questions:

?

1.? I don't see the ground connection on the motherboard for the ground pins of the filter trays.

2.? Did you want to isolate the relay coils? input versus output?? ?I don't see inductors / capacitors to avoid energy getting AROUND the filters via the coils, the coil wiring and then out the other coil.

?

Gordon,

The ground pins on the filter trays are connected to the ground plane on the board and there are 3 grounds and the coax shields which return to uBITX ground. I'll also send the ground plane image. Does not have anything to avoid energy getting around the coils. Just basic LPF design, if/when the LPF is not used, both ends of that LPF are grounded. Relay contacts are redundant and bifurcated.

73 Kees K5BCQ

For some reason the PDFs were duplicated so I erased the thing and redid the note.....confusing enough ;o)?

PRELIMINARY..............

The idea here is to use the existing uBITX components on a different board which has a relay at each end of each LPF. The board inserts between T11 RF output and the K3 contact which goes to the antenna.
?
I was thinking of using the existing TXA, TXB, and TXC to drive 2 relays each (on both ends of the LPFs). Then you add a 3 diode "OR" to those 3 select lines to drive the 4th relay which, in it's normally closed state, "has picked" the 4th LPF (as it does today on the uBITX). Activation of any of the three pulls it "off" the LPF and grounds it. That would only require 3 diodes and a 2N3904 driver for 4th relay.

The daughter board itself measures 74.7mm x 61.7mm and will mount 4 of Hans' LPF boards or, if you can find blank boards, you can use the exact components removed from the uBITX board. The daughter board has the option to have RF IN and RF OUT on the same side or opposite sides via coax (to T11 and K3). The picture shows the top side of the board, the bottom is a full ground plane. The little relays used are 15mm x 10mm relays .....in this case, an Omron G6H-2F. It's a 5V relay so you have to bring in 5V. You can select a similar 12V relay.??

The small example plug-in LPF board has 60mil traces (better line impedance) on one side and a ground plane on the other.?The main capacitors are SMT and located on the underside. The Cx trimmers are on the top with the coils and can be PIH or SMT.??

Please ask if you have any questions.

73 Kees K5BCQ

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?Hi Keyes --- I wasn't following so not sure if this is for OUTPUT or as a preselector for the PA stage.? ?I don't know exactly how to read your PCB's but a few questions:

1.? I don't see the ground connection on the motherboard for the ground pins of the filter trays.

2.? Did you want to isolate the relay coils? input versus output?? ?I don't see inductors / capacitors to avoid energy getting AROUND the filters via the coils, the coil wiring and then out the other coil.

Thanks,

gordon

On Sun, Aug 12, 2018 at 03:23 PM, W3JDR wrote:

Pretty picture nothing else, looks slick and tiny.? A schematic might be useful.

Allison

K4MRT,

I sincerely doubt you getting 24W (70V-PP).? I can believe 7W.

Into? a 50ohm load I'd expect to see maybe 35VPP. for around 6-7W.

Most people put a scope probe across? the output and and cause
serious measurement error.? ?

You can check most scopes with a DC power supply and a multimeter if
the two agree great.? Then you need to use a properly calibrated probe
or better yet review EMRFD (measurements chapter) for correct
procedure.

Even then I consider a scope the least accurate.

A dummy load with diode detector can be calibrated with DC supply.
Plenty of site on how its done and its dirt simple.? Just remember?
mode diode measurements are PEAK voltage and you convert that
to RMS to calculate power.

Allison

The non push pull bitx amp is class AB1 (around 50 ma bias) single ended.

The power out is more a function of the drive available and they tended to be
all over the map.? With 200-400mW of drive the power sould be around 6-8W.
IF you have enough drive it will top out about 10W @ 13V.

With higher DC voltage, the output can easily reach 25W if there is enough
drive (at least 1W) and the circuit around it can actually work at that power.

I have several using IRF510 and for 13V I expect 7W,? ar 16V I've seen 11W
(clean, not saturated).? At 6M I expect 5W at 13V and at 24 not less than
22-23.

In all cases many of the earlier bitx have anemic drive or earlier stages due to device?
or operating conditions for those devices.? FYI 2n3866 is good, the 2N2219
also works for 40 and 20 and should be ok at 17M.? The? 2n3904s at anything
under 20M are only ok for low power stages (under 50mW).? The BS170
push pull driver can easily do 800mw and a IRF510 will make that into?
about 12w (or more) if everything else was right.

The IRF510 will do if properly used about 15-16db of power gain at 10mhz and
down and at least 13db even at 6M.? ?It likes higher voltages with 23-28V?
being a sweet spot with bias in the 100ma range maybe higher.

The uBitx is not the same beast as the monoband Bitx versions.

Allison