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That looks like a great antenna and I bet you will have a Lotta fun. ? If you have some way to measure the standing wave ratio, that will help. ?I buy used Citizen band SWR meters for about $15 at Hamfest‘s to help people new to HF to get going. there are also some models on Amazon for $15-$20 that work fine

If I were going to the trouble of adding a mic gain element, I would use the ssm2617 chip or board. I have and with it you can use the compression to increase your average power significantly. I check in every week to our local net now with the ubitx on 75 meters and nobody has an issue copying me. If you use the board, you need to adjust the level going into the chip or the compression does not work properly.
73 Brad N8YG

Shorten each vertical wire by 6 feet. This will make antenna play on 7 and 21 MHz. Perhaps add a parallel wire 16.5 feet on each side for 14 Mhz. This seems an easy antenna for coax feed.

An FD3 antenna with off center feed could work, but it needs a balun at feed point, or ladder line instead of coax and an antenna tuner.
Curt

There are Raduino clones available from other sources than HF Signals.? Jim Sheldon, W0EB has a kit that is good and his service is great.? i would recommend that rout, as the Raduino is used in both the uBitx and Bitx40, with different SW that is available on multiple sites.



73
Evan
AC9TU

Tech Guy,

Here is a link to the issues as per the designer Ashhar Farhan:
/g/BITX20/topic/spurs_harmonics_whew/28982939?p=Created,,,20,1,0,0::recentpostdate%2Fsticky,,,20,2,0,28982939

I am still trying to find the thread that Ashhar presented the attached hand sketch for the Spurs fixes: (Note: there are some discrepancies in the text vs the schematic)

The longest thread also delves into the issues of how to measure the emissions without spending >$800 for test equipment.
/g/BITX20/topic/29340928#64194

Lastly, I would look at the differences between the v5 and v4 board for the transmitter circuits to see what was done.? As mentioned by Curt and Mark, the best solution for the harmonics is to either add a daughter board for the LPFs, or cut and rewire the traces on the board to reduce the blow back.? This will not address the spurs above 14mhz, that was only solved by the LPF between the IF and the final mixer (going from audio to PA).? The v5 board also changed the 2n3904 out for that IF stage to BFR93Ws to overcome low gain at 90mhz.

Of note is that the entire spurs and harmonic issues came about by an effort to make the output consistent across all of the bands.? It was during that effort that showed that there was a potential issue.

As far as I know the answer to your question is that there are multiple lists, including one at ubitx.net.? For me, I have reached the conclusion that you will need test equipment that can measure the 2 known issues of spurs and harmonics to verify that the v3 and v4 boards are clean enough to feed into a linear amp, but are probably low enough to not be an issue running bare foot on 12 vdc power to the PA.? This is of course for the US.? For most of the rest of the world, the board as supplied meets their requirements.

Truthfully, the lessons learned has been the most fun of the v4 board fix.? Since I have gotten the v5 board, have not really used it, as I am not really that much into operating, more into the technical solves.

FWIW, Above are my observations and opinions, others may be different.? Please do your own research before you make any choices based on them.? The search function on the board are hard to use (at least for me), however there is information here that is worth the digging.

73
Evan
AC9TU

OK I've the confirmation here :?

The 6.35mm jack is well for the headset.?

Dear all,

I live on the top floor of a 3 story apartment. I do not have any other space for antenna except the rooftop. To set up a dipole antenna I made a plan i have attached below. I will use common PVC insulated household electrical wire approx 3-4 sqmm dia, for antenna. I will use a uBitx transceiver and tx power will not be much (Maximum that uBitx support). I am requesting you to suggest/advice me how this antenna will perform and also advise me to make balun/matching transformer/antenna tuner for this antenna. Thick black wire is coax and thick blue wire is antenna.

Regards
Ashok

Either add a pc board hosting added relays or switch the relays to axicom.

Or do Allison's relay mod as described in the wiki.? No need to buy new parts if you don't want to.? Also the Axicom swap relies on the relay having better specifications (which may change with production or if you end up with conterfeit parts) while Allison's mod relies on better isolation of the signal paths and a better switching scheme (like you get with the v5 and probably like is done in the accessory relay board).

73,


Mark.

V3 and v4 need reduced leakage through LPF relays. Either add a pc board hosting added relays or switch the relays to axicom. Our club kitted a relay board designed by Gordon Gibby, but no one is yet selling it.

That leaves spurs associated with the mixer from 45 MHz to RF. Shielded inductors said to help, and additional 45 MHz filtering. This issue impacts 21 MHz and higher only.

No clear consensus nor kitting on these.

Curt

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I have an early bitx 40 without the radino dds. Has anyone used the dds from qrp kits? I have something ?that I stuck together on an experimenter board but it doesn’t have enough drive for the mixer I think. I used a dds from ebay with a nano.

Is there a place that lists v4 fixes for improved compliance?

I am suspicious the arrl lab evaluated harmonics but did not know to look for ssb mixer spurious. No evidence that they did.

Curt

Primary focus is lower spurious.? I myself have not seen a complete set of SSB spurious, but it is said to be in the neighborhood of compliance.? It uses a wider SSB filter, not really an improvement in my thinking but this was done to move away from some internal spurious leakage.? Functionality is unchanged.? I am a v4 owner - its a fun rig - I have all but the high frequency SSB spurious corrected.?

73 Curt

Per the ARRL September QST the uBitx v5 passes FCC requirements.? The prior versions did not.

Other than cleaning up the signal, there are only differences, not necessarily improvements in the calibration procedure.? Calibration now requires a dummy load, or else you would be transmitting on 10MHz, out of band for the US.?

I do feel like I can now build the 70 watt linear for the rig that I was hesitant to do so with the prior versions.? After that will go back and work on the 2 v4 rigs that I have to get them up to speed and setup for digital.

Really fun rig, and a good platform to learn on.

The above is my opinion, others may differ and are entitled to their own.

73
Evan
AC9TU

Is the current product’s spurs much better than v4? Any new features or just signal improvement?

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Thanks!

On 8/24/2019 16:34, John Norris wrote:

My BITX40 shrieks if I get my cellphone too close to it.

Not too surprised after I discovered a similar issue.?? My high frequency hearing isn't very good so I built an active high pass filter (741 ICs) / amp (LM386s). Worked great but had a problem.? Intermittent loud clicking and screeching.?? After a lot of troubleshooting, discovered that if my cell phone was within 2', it was bad.?? Moved the phone away a bit and the problem disappeared.
Woody - KZ4AK

--

Thanks everyone for your answers. I've well measured something opened on the 5mm jack connector. So maybe it's the mic.?

So it seems that :
6.35mm jack is for headset and is about 60 ohms
5mm jack is for mic and acts like an open circuit.?

Does anybody with that kind of aircraft headset could confirm that the mic is well on 5mm jack and headset is 6.35mm jack??

If yes I guess that kind of headset could work. I'll give it a try.?