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Don't know if any of you have been following the debacle going on over at the group regarding the uBitx, but those few fortunate people who have quality Spectrum Analyzers and know how to use them, have found that the uBitx 'mostly' does not pass FCC specs, (US), for spectral purity, (some nasty spurs). Some are advising not to use them on the air until some kind of fix is figured out. Funny I have been using mine every since they came out and nobody has knocked at my door yet, but I don't want them to either. All of the EE's on the group are seeking to redesign the uBitx to meet specs. I find this whole thing to be rather disheartening after all the time and effort I put into my two radios. They are talking about cutting the traces going to the LPF section and adding a daughter board with a new LPF design to fixed the existing boards. Not quite sure what to do but wait and see what everybody comes up with. :( :-[ :-\

Technical Corner / Re: Armored BitX40.
« Last post by ELK on August 09, 2018, 10:24:31 AM »
Hi everyone !

I have ordered 2 different kinds of 4x4 and 4x5 membrane matrix keyboards to simulate Gil's military keyboard and work on the corresponding Arduino code.

While waiting for them to come from China (with a bunch of other thingies for my Arduino ecosystem), I am working on adding morse code "talking" capacities to report useful data without any display to the original BitX40 Raduino code.

My main issue is to find enough free pins to connect the keyboard, a buzzer (passive if a pwm pin is available, active if not) for morse rendition and a pin to read battery voltage via a voltage divider (or a specific voltage/current sensor like INA169 and its successors).

I'll get you in touch of my progression...

73! de Stan.
Technical Corner / Re: Armored BitX40.
« Last post by gil on August 09, 2018, 09:27:56 AM »
Back to work!

Actually, thanks to ELK here, Stan, this project just might see the light of day.

Stan is working on the Arduino code to drive the DDS, the Si5351A, to output from 4750 to 5250kHz, which translates to 6950 to 7450kHz for the BitX40.

Here is the list of the keys to be used on the keyboard:

  • Numbers 0-9: Same.
  • Clr: Clear entry, reset.
  • Sto ENT: Enter frequency.
  • Batt CALL: Battery voltage output in Morse.
  • Freq: Frequency output in Morse.
  • Send OFST: + 100Hz. Hold +half-second=+100Hz 5x/sec (+500Hz/sec).
  • TIME: - 100Hz. Hold +half-second=-100Hz 5x/sec (-500Hz/sec).

Also planned are a confirmation beep and an out-of-range beep, maybe a battery low every-5-sec beep below a certain voltage to be determined.
I will let him post about his progress here  :)

Stay tuned...

General Discussion / Rado Preppers on Facebook.
« Last post by gil on August 09, 2018, 06:07:13 AM »
General Discussion / 73s from Croatian Adria
« Last post by CroPrepper on August 08, 2018, 05:28:08 AM »
I am on vacation atm and tried out some setups with sea as a reflector. Quite surprising results...

Via TapaTalk

Thanks. I guess my new minimum is 11.5V...

Net Activity / Re: Radio Vacation
« Last post by dylan on August 06, 2018, 09:51:53 PM »
Some updates, still trying to figure out the radiation pattern to expect from an EFHW antenna. Over the last 20 years most of my antennas have been half-wave doublets.

The 20m EFHW was setup as a "sloper" with the feed point at about 5' from the ground and terminating at about 15' from the ground. Connecting this kind of antenna to the EFHW QRPGuys tuner has always been a challenge as there aren't many options for strain relief. This time I tried something new, as I had an overhead shade that I could use as an anchor. I put a single loop in the antenna wire around a bowline tied into some paracord that was anchored from above. This transferred tension from the "long part" of the antenna wire and left me with about 3' of slack which could be connected to the tuner (attached image). I suppose you could do something similar with an anchor from below, perhaps tied to a tent peg.

I used 26 AWG "silky" wire in this latest experiment which was far lighter and easier to work with than my previous attempts with 14 AWG stranded copper wire.

The counterpoise wire was tossed out on the ground below the driven element. Tinkering with the antenna analyzer seemed to suggest that this gave the best SWR and broadest local minimum in the SWR curve.

Some questions come to mind:

1. Does this kind of strain relief (e.g. a single loop of wire) affect tuning characteristics? It didn't seem to, as my antenna analyzer reported reasonable SWR curves over the 20m band.

2. I found this neat page ( on the theoretical radiation patterns for sloping EFHW antennas, but it still isn't clear to me what the resulting radiation pattern for my recent setup should be (in theory). Based on the linked table ( It would appear that this antenna, hoisted to about 15' (~ 0.25 wavelength) radiates most of the energy straight up! That doesn't seem right, or does it?

I always used 10.5V as the minimum for lead-acid, SLA and AGM batteries, but I have no idea if that's 50%...

Hi Gil. 10.5V is considered to be 95% - 100% discharged and the battery is considered completely dead. In fact, for most batteries, anything below about 11.3 volts is thought to cause permanent damage.

I agree Wally. The biggest takeaway here seems to be the reverse of what I've always been told. That in order to get the most life out of one's batteries, both in terms of longevity and max ah delivery, one should only sip the top few percent off of them.

People who use these batteries for off grid living generally do one cycle per day. They charge during the day and discharge at night, to be charged again the following day. What most off grid people want, is to buy the fewest number of batteries per year. So for the batteries on the graph, 50% discharge gives you 700 cycles or almost 2 years of battery life. But in order to discharge one's batteries less, one has to have a bigger battery bank (more batteries). So the question is, when does it start paying off to buy a big battery bank up front and only sip the top 20% off of them and when does it make more sense to buy fewer batteries at a time but buy them more often. According to this graph, you will always pay less overall, the more batteries you buy upfront and sip just the top of them.

Lets say a person needs 100ah per day. Lets say he can buy 100ah batteries for $200 a piece. If he plans to discharge them down to 50% he will need two batteries to meet his demands and they will last him almost 2 years costing him about $200 per year.

Now say he wants to only draw 25% off of them. He will then need twice as many batteries to meet his demand. 4 batteries will run him $800 up front but those batteries will now last him 1900 days/cycles or 5.2 years. So twice as many batteries lasts him well over twice as long when running them all together. $800 / 5.2 = $154 per year, a $46/year savings.

This trend holds true for all values above 50% discharge but not for anything below 50% discharge since the vector of the graph changes abruptly at the 50% point. According the the graph, after 50%. you're no worse off and perhaps even slightly better off discharging the batteries all the way down to 80%.

This is what surprised me. I've always been told the reverse, that you will get most of the batteries maximum life so long as you keep it above 50% and you only start to see rapid drop in longevity when going below 50%.
Antennas / Re: Successful Wire Antennas.
« Last post by Jon_Garfio on August 06, 2018, 09:23:59 AM »
I think I have complete PDF into my ham radio books folder, I Will try to found It.

Enviado desde mi Redmi Note 4 mediante Tapatalk

I always used 10.5V as the minimum for lead-acid, SLA and AGM batteries, but I have no idea if that's 50%...

Yes, 10.5v gives a better and long life st the batteries. I use the same config for my solar regulator.

Enviado desde mi Redmi Note 4 mediante Tapatalk

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