Hi, The 600 ohms sounds more like a spec for the mic. Perhaps it is a dynamic one, where 600 ohms would be quite typical. 73, Mark.

#ubitx

Hi, I would take a small "pocket screwdriver" and file it down to a sharp chisel tip. Then go around the hole and make a circle cut the size of the bolt head or standoff. Finally, chip/chisel off the

Hi, Was the spur problem of the previous versions, reliably fixed on v5? I seem to remember the solution sometimes causing issues with low output on 40m. 73, Mark.

#ubitx #v5

Hi Dries, It looks like you have been working hard on this. Good job to get this far! It is much harder to work from scratch, than to build a kit, but you can learn a lot! This site: http://golddredge

#bitx20help

Thanks Peter! Beside all the TX circuitry, the relay is also driving two other relay coils, so I wonder if that may cause a bit of stress too? Initial resistance of the relay coils in parallel might b

#ubitx #bitx20

Hi Rob, I don't think anything unusual is happening in your case. Just making some general observations: The heatsinks provided are probably good for about 20C/W dissipation; meaning the heatsink temp

#ubitx-help #ubitx #v5

Hi, A mono plug inserted into a stereo socket will short the ring connection to ground and thus engage the PTT. See the wireup diagram on the groups.io wiki section.

It was just from early morning memory, But as a reference I quickly saw this: https://www.abdengineering.com/blog/perception-vs-reality/ They confirm a doubling/halving needed. But I found a test site

Hi David, Could be quite useful for BCI and other out of band receive interference, but I don't think it was made for transmiter harmonics/spur reduction. 73, Mark.

Hi John, The lm386 often states a common output power of 125mW. This is actually a pretty strong volume level, but looking at it will give you an idea of what type of voltage you may see. Po = V^2/R s

Hi, Are they powering on to RX or TX? Unless you have the CW resistors installed on the KEY jack, the radio will power up on TX. 73, Mark.

Hi Dennis, The manufacturer has a page for setting the PA bias; I would go by that recommendation for sure: ubitx tuneup The instructions call for 100mA above background current requirement for each P

#v5 #ubitx #pabias

Hi Dennis, This seems perfectly normal to me. My v3 (as delivered without and changes to the bias) on CW drew from 2A on 80m to less than 1A on 10m, on SSB with a microphone and a loud "hello" it shou

#v5 #ubitx #pabias

Correction: I meant IRF-510 and for the heatsink, I meant an old Pentium III Slot 1 type (still sold new for cheap on ebay and they have relatively quiet fans usually). Cheers and 73, Mark.

Hmm, I don't know what would be unsafe about running the finals at higher voltage. That is how most IRF510 amps are run. Keep to the voltage below 28v and I think they would be pretty durable. Maybe A

Hi N7QL, The original Bitx20 is a single band design, thus one would generally just be concerned with harmonics generated by the PA. These should have been taken care of by the low pass filter in the

Hi, Three throws means three separate contacts for each pole. So this would require three contacts for each pole and one contact each for the pole itself. Thus eight contacts are needed for a DP3T swi

Hi, That's not a 2P3T switch. With only six connections it can either be a 2P2T or a 3PST. 73, Mark

Hi, Sure, higher wattage is better if the package still fits. But for audio, I'm be more likely to choose a low-noise bc548 type or a 4401 type (which is a bit beefier and doesn't have the high ft of

Hmm, On second thought, adding up all the harmonics probably won't make much of a difference. More likely the variations in the individual bands is due to uneven reponse in the stages and mixer prior